Update Linux to v5.10.109
Sourced from [1]
[1] https://cdn.kernel.org/pub/linux/kernel/v5.x/linux-5.10.109.tar.xz
Change-Id: I19bca9fc6762d4e63bcf3e4cba88bbe560d9c76c
Signed-off-by: Olivier Deprez <olivier.deprez@arm.com>
diff --git a/Documentation/virt/guest-halt-polling.rst b/Documentation/virt/guest-halt-polling.rst
new file mode 100644
index 0000000..b4e7479
--- /dev/null
+++ b/Documentation/virt/guest-halt-polling.rst
@@ -0,0 +1,84 @@
+==================
+Guest halt polling
+==================
+
+The cpuidle_haltpoll driver, with the haltpoll governor, allows
+the guest vcpus to poll for a specified amount of time before
+halting.
+
+This provides the following benefits to host side polling:
+
+ 1) The POLL flag is set while polling is performed, which allows
+ a remote vCPU to avoid sending an IPI (and the associated
+ cost of handling the IPI) when performing a wakeup.
+
+ 2) The VM-exit cost can be avoided.
+
+The downside of guest side polling is that polling is performed
+even with other runnable tasks in the host.
+
+The basic logic as follows: A global value, guest_halt_poll_ns,
+is configured by the user, indicating the maximum amount of
+time polling is allowed. This value is fixed.
+
+Each vcpu has an adjustable guest_halt_poll_ns
+("per-cpu guest_halt_poll_ns"), which is adjusted by the algorithm
+in response to events (explained below).
+
+Module Parameters
+=================
+
+The haltpoll governor has 5 tunable module parameters:
+
+1) guest_halt_poll_ns:
+
+Maximum amount of time, in nanoseconds, that polling is
+performed before halting.
+
+Default: 200000
+
+2) guest_halt_poll_shrink:
+
+Division factor used to shrink per-cpu guest_halt_poll_ns when
+wakeup event occurs after the global guest_halt_poll_ns.
+
+Default: 2
+
+3) guest_halt_poll_grow:
+
+Multiplication factor used to grow per-cpu guest_halt_poll_ns
+when event occurs after per-cpu guest_halt_poll_ns
+but before global guest_halt_poll_ns.
+
+Default: 2
+
+4) guest_halt_poll_grow_start:
+
+The per-cpu guest_halt_poll_ns eventually reaches zero
+in case of an idle system. This value sets the initial
+per-cpu guest_halt_poll_ns when growing. This can
+be increased from 10000, to avoid misses during the initial
+growth stage:
+
+10k, 20k, 40k, ... (example assumes guest_halt_poll_grow=2).
+
+Default: 50000
+
+5) guest_halt_poll_allow_shrink:
+
+Bool parameter which allows shrinking. Set to N
+to avoid it (per-cpu guest_halt_poll_ns will remain
+high once achieves global guest_halt_poll_ns value).
+
+Default: Y
+
+The module parameters can be set from the debugfs files in::
+
+ /sys/module/haltpoll/parameters/
+
+Further Notes
+=============
+
+- Care should be taken when setting the guest_halt_poll_ns parameter as a
+ large value has the potential to drive the cpu usage to 100% on a machine
+ which would be almost entirely idle otherwise.
diff --git a/Documentation/virt/index.rst b/Documentation/virt/index.rst
index 062ffb5..350f5c8 100644
--- a/Documentation/virt/index.rst
+++ b/Documentation/virt/index.rst
@@ -8,7 +8,10 @@
:maxdepth: 2
kvm/index
+ uml/user_mode_linux_howto_v2
paravirt_ops
+ guest-halt-polling
+ ne_overview
.. only:: html and subproject
diff --git a/Documentation/virt/kvm/amd-memory-encryption.rst b/Documentation/virt/kvm/amd-memory-encryption.rst
index d18c97b..09a8f2a 100644
--- a/Documentation/virt/kvm/amd-memory-encryption.rst
+++ b/Documentation/virt/kvm/amd-memory-encryption.rst
@@ -53,6 +53,29 @@
encrypting bootstrap code, snapshot, migrating and debugging the guest. For more
information, see the SEV Key Management spec [api-spec]_
+The main ioctl to access SEV is KVM_MEMORY_ENCRYPT_OP. If the argument
+to KVM_MEMORY_ENCRYPT_OP is NULL, the ioctl returns 0 if SEV is enabled
+and ``ENOTTY` if it is disabled (on some older versions of Linux,
+the ioctl runs normally even with a NULL argument, and therefore will
+likely return ``EFAULT``). If non-NULL, the argument to KVM_MEMORY_ENCRYPT_OP
+must be a struct kvm_sev_cmd::
+
+ struct kvm_sev_cmd {
+ __u32 id;
+ __u64 data;
+ __u32 error;
+ __u32 sev_fd;
+ };
+
+
+The ``id`` field contains the subcommand, and the ``data`` field points to
+another struct containing arguments specific to command. The ``sev_fd``
+should point to a file descriptor that is opened on the ``/dev/sev``
+device, if needed (see individual commands).
+
+On output, ``error`` is zero on success, or an error code. Error codes
+are defined in ``<linux/psp-dev.h>``.
+
KVM implements the following commands to support common lifecycle events of SEV
guests, such as launching, running, snapshotting, migrating and decommissioning.
@@ -90,6 +113,8 @@
On success, the 'handle' field contains a new handle and on error, a negative value.
+KVM_SEV_LAUNCH_START requires the ``sev_fd`` field to be valid.
+
For more details, see SEV spec Section 6.2.
3. KVM_SEV_LAUNCH_UPDATE_DATA
@@ -245,6 +270,6 @@
See [white-paper]_, [api-spec]_, [amd-apm]_ and [kvm-forum]_ for more info.
.. [white-paper] http://amd-dev.wpengine.netdna-cdn.com/wordpress/media/2013/12/AMD_Memory_Encryption_Whitepaper_v7-Public.pdf
-.. [api-spec] http://support.amd.com/TechDocs/55766_SEV-KM_API_Specification.pdf
-.. [amd-apm] http://support.amd.com/TechDocs/24593.pdf (section 15.34)
-.. [kvm-forum] http://www.linux-kvm.org/images/7/74/02x08A-Thomas_Lendacky-AMDs_Virtualizatoin_Memory_Encryption_Technology.pdf
+.. [api-spec] https://support.amd.com/TechDocs/55766_SEV-KM_API_Specification.pdf
+.. [amd-apm] https://support.amd.com/TechDocs/24593.pdf (section 15.34)
+.. [kvm-forum] https://www.linux-kvm.org/images/7/74/02x08A-Thomas_Lendacky-AMDs_Virtualizatoin_Memory_Encryption_Technology.pdf
diff --git a/Documentation/virt/kvm/api.txt b/Documentation/virt/kvm/api.rst
similarity index 63%
rename from Documentation/virt/kvm/api.txt
rename to Documentation/virt/kvm/api.rst
index fd22224..cd8a585 100644
--- a/Documentation/virt/kvm/api.txt
+++ b/Documentation/virt/kvm/api.rst
@@ -1,11 +1,14 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+===================================================================
The Definitive KVM (Kernel-based Virtual Machine) API Documentation
===================================================================
1. General description
-----------------------
+======================
The kvm API is a set of ioctls that are issued to control various aspects
-of a virtual machine. The ioctls belong to three classes:
+of a virtual machine. The ioctls belong to the following classes:
- System ioctls: These query and set global attributes which affect the
whole kvm subsystem. In addition a system ioctl is used to create
@@ -33,7 +36,7 @@
was used to create the VM.
2. File descriptors
--------------------
+===================
The kvm API is centered around file descriptors. An initial
open("/dev/kvm") obtains a handle to the kvm subsystem; this handle
@@ -62,7 +65,7 @@
put their references to the VM's file descriptor.
Because a VM's resources are not freed until the last reference to its
-file descriptor is released, creating additional references to a VM via
+file descriptor is released, creating additional references to a VM
via fork(), dup(), etc... without careful consideration is strongly
discouraged and may have unwanted side effects, e.g. memory allocated
by and on behalf of the VM's process may not be freed/unaccounted when
@@ -70,7 +73,7 @@
3. Extensions
--------------
+=============
As of Linux 2.6.22, the KVM ABI has been stabilized: no backward
incompatible change are allowed. However, there is an extension
@@ -84,13 +87,14 @@
4. API description
-------------------
+==================
This section describes ioctls that can be used to control kvm guests.
For each ioctl, the following information is provided along with a
description:
- Capability: which KVM extension provides this ioctl. Can be 'basic',
+ Capability:
+ which KVM extension provides this ioctl. Can be 'basic',
which means that is will be provided by any kernel that supports
API version 12 (see section 4.1), a KVM_CAP_xyz constant, which
means availability needs to be checked with KVM_CHECK_EXTENSION
@@ -99,24 +103,29 @@
availability: for kernels that don't support the ioctl,
the ioctl returns -ENOTTY.
- Architectures: which instruction set architectures provide this ioctl.
+ Architectures:
+ which instruction set architectures provide this ioctl.
x86 includes both i386 and x86_64.
- Type: system, vm, or vcpu.
+ Type:
+ system, vm, or vcpu.
- Parameters: what parameters are accepted by the ioctl.
+ Parameters:
+ what parameters are accepted by the ioctl.
- Returns: the return value. General error numbers (EBADF, ENOMEM, EINVAL)
+ Returns:
+ the return value. General error numbers (EBADF, ENOMEM, EINVAL)
are not detailed, but errors with specific meanings are.
4.1 KVM_GET_API_VERSION
+-----------------------
-Capability: basic
-Architectures: all
-Type: system ioctl
-Parameters: none
-Returns: the constant KVM_API_VERSION (=12)
+:Capability: basic
+:Architectures: all
+:Type: system ioctl
+:Parameters: none
+:Returns: the constant KVM_API_VERSION (=12)
This identifies the API version as the stable kvm API. It is not
expected that this number will change. However, Linux 2.6.20 and
@@ -127,12 +136,13 @@
4.2 KVM_CREATE_VM
+-----------------
-Capability: basic
-Architectures: all
-Type: system ioctl
-Parameters: machine type identifier (KVM_VM_*)
-Returns: a VM fd that can be used to control the new virtual machine.
+:Capability: basic
+:Architectures: all
+:Type: system ioctl
+:Parameters: machine type identifier (KVM_VM_*)
+:Returns: a VM fd that can be used to control the new virtual machine.
The new VM has no virtual cpus and no memory.
You probably want to use 0 as machine type.
@@ -155,17 +165,17 @@
address used by the VM. The IPA_Bits is encoded in bits[7-0] of the
machine type identifier.
-e.g, to configure a guest to use 48bit physical address size :
+e.g, to configure a guest to use 48bit physical address size::
vm_fd = ioctl(dev_fd, KVM_CREATE_VM, KVM_VM_TYPE_ARM_IPA_SIZE(48));
-The requested size (IPA_Bits) must be :
- 0 - Implies default size, 40bits (for backward compatibility)
+The requested size (IPA_Bits) must be:
- or
-
- N - Implies N bits, where N is a positive integer such that,
+ == =========================================================
+ 0 Implies default size, 40bits (for backward compatibility)
+ N Implies N bits, where N is a positive integer such that,
32 <= N <= Host_IPA_Limit
+ == =========================================================
Host_IPA_Limit is the maximum possible value for IPA_Bits on the host and
is dependent on the CPU capability and the kernel configuration. The limit can
@@ -182,21 +192,28 @@
4.3 KVM_GET_MSR_INDEX_LIST, KVM_GET_MSR_FEATURE_INDEX_LIST
+----------------------------------------------------------
-Capability: basic, KVM_CAP_GET_MSR_FEATURES for KVM_GET_MSR_FEATURE_INDEX_LIST
-Architectures: x86
-Type: system ioctl
-Parameters: struct kvm_msr_list (in/out)
-Returns: 0 on success; -1 on error
+:Capability: basic, KVM_CAP_GET_MSR_FEATURES for KVM_GET_MSR_FEATURE_INDEX_LIST
+:Architectures: x86
+:Type: system ioctl
+:Parameters: struct kvm_msr_list (in/out)
+:Returns: 0 on success; -1 on error
+
Errors:
- EFAULT: the msr index list cannot be read from or written to
- E2BIG: the msr index list is to be to fit in the array specified by
- the user.
-struct kvm_msr_list {
+ ====== ============================================================
+ EFAULT the msr index list cannot be read from or written to
+ E2BIG the msr index list is to be to fit in the array specified by
+ the user.
+ ====== ============================================================
+
+::
+
+ struct kvm_msr_list {
__u32 nmsrs; /* number of msrs in entries */
__u32 indices[0];
-};
+ };
The user fills in the size of the indices array in nmsrs, and in return
kvm adjusts nmsrs to reflect the actual number of msrs and fills in the
@@ -217,12 +234,13 @@
4.4 KVM_CHECK_EXTENSION
+-----------------------
-Capability: basic, KVM_CAP_CHECK_EXTENSION_VM for vm ioctl
-Architectures: all
-Type: system ioctl, vm ioctl
-Parameters: extension identifier (KVM_CAP_*)
-Returns: 0 if unsupported; 1 (or some other positive integer) if supported
+:Capability: basic, KVM_CAP_CHECK_EXTENSION_VM for vm ioctl
+:Architectures: all
+:Type: system ioctl, vm ioctl
+:Parameters: extension identifier (KVM_CAP_*)
+:Returns: 0 if unsupported; 1 (or some other positive integer) if supported
The API allows the application to query about extensions to the core
kvm API. Userspace passes an extension identifier (an integer) and
@@ -235,12 +253,13 @@
with KVM_CAP_CHECK_EXTENSION_VM on the vm fd)
4.5 KVM_GET_VCPU_MMAP_SIZE
+--------------------------
-Capability: basic
-Architectures: all
-Type: system ioctl
-Parameters: none
-Returns: size of vcpu mmap area, in bytes
+:Capability: basic
+:Architectures: all
+:Type: system ioctl
+:Parameters: none
+:Returns: size of vcpu mmap area, in bytes
The KVM_RUN ioctl (cf.) communicates with userspace via a shared
memory region. This ioctl returns the size of that region. See the
@@ -248,23 +267,25 @@
4.6 KVM_SET_MEMORY_REGION
+-------------------------
-Capability: basic
-Architectures: all
-Type: vm ioctl
-Parameters: struct kvm_memory_region (in)
-Returns: 0 on success, -1 on error
+:Capability: basic
+:Architectures: all
+:Type: vm ioctl
+:Parameters: struct kvm_memory_region (in)
+:Returns: 0 on success, -1 on error
This ioctl is obsolete and has been removed.
4.7 KVM_CREATE_VCPU
+-------------------
-Capability: basic
-Architectures: all
-Type: vm ioctl
-Parameters: vcpu id (apic id on x86)
-Returns: vcpu fd on success, -1 on error
+:Capability: basic
+:Architectures: all
+:Type: vm ioctl
+:Parameters: vcpu id (apic id on x86)
+:Returns: vcpu fd on success, -1 on error
This API adds a vcpu to a virtual machine. No more than max_vcpus may be added.
The vcpu id is an integer in the range [0, max_vcpu_id).
@@ -305,22 +326,25 @@
4.8 KVM_GET_DIRTY_LOG (vm ioctl)
+--------------------------------
-Capability: basic
-Architectures: all
-Type: vm ioctl
-Parameters: struct kvm_dirty_log (in/out)
-Returns: 0 on success, -1 on error
+:Capability: basic
+:Architectures: all
+:Type: vm ioctl
+:Parameters: struct kvm_dirty_log (in/out)
+:Returns: 0 on success, -1 on error
-/* for KVM_GET_DIRTY_LOG */
-struct kvm_dirty_log {
+::
+
+ /* for KVM_GET_DIRTY_LOG */
+ struct kvm_dirty_log {
__u32 slot;
__u32 padding;
union {
void __user *dirty_bitmap; /* one bit per page */
__u64 padding;
};
-};
+ };
Given a memory slot, return a bitmap containing any pages dirtied
since the last call to this ioctl. Bit 0 is the first page in the
@@ -337,25 +361,31 @@
see the description of the capability.
4.9 KVM_SET_MEMORY_ALIAS
+------------------------
-Capability: basic
-Architectures: x86
-Type: vm ioctl
-Parameters: struct kvm_memory_alias (in)
-Returns: 0 (success), -1 (error)
+:Capability: basic
+:Architectures: x86
+:Type: vm ioctl
+:Parameters: struct kvm_memory_alias (in)
+:Returns: 0 (success), -1 (error)
This ioctl is obsolete and has been removed.
4.10 KVM_RUN
+------------
-Capability: basic
-Architectures: all
-Type: vcpu ioctl
-Parameters: none
-Returns: 0 on success, -1 on error
+:Capability: basic
+:Architectures: all
+:Type: vcpu ioctl
+:Parameters: none
+:Returns: 0 on success, -1 on error
+
Errors:
- EINTR: an unmasked signal is pending
+
+ ===== =============================
+ EINTR an unmasked signal is pending
+ ===== =============================
This ioctl is used to run a guest virtual cpu. While there are no
explicit parameters, there is an implicit parameter block that can be
@@ -365,42 +395,46 @@
4.11 KVM_GET_REGS
+-----------------
-Capability: basic
-Architectures: all except ARM, arm64
-Type: vcpu ioctl
-Parameters: struct kvm_regs (out)
-Returns: 0 on success, -1 on error
+:Capability: basic
+:Architectures: all except ARM, arm64
+:Type: vcpu ioctl
+:Parameters: struct kvm_regs (out)
+:Returns: 0 on success, -1 on error
Reads the general purpose registers from the vcpu.
-/* x86 */
-struct kvm_regs {
+::
+
+ /* x86 */
+ struct kvm_regs {
/* out (KVM_GET_REGS) / in (KVM_SET_REGS) */
__u64 rax, rbx, rcx, rdx;
__u64 rsi, rdi, rsp, rbp;
__u64 r8, r9, r10, r11;
__u64 r12, r13, r14, r15;
__u64 rip, rflags;
-};
+ };
-/* mips */
-struct kvm_regs {
+ /* mips */
+ struct kvm_regs {
/* out (KVM_GET_REGS) / in (KVM_SET_REGS) */
__u64 gpr[32];
__u64 hi;
__u64 lo;
__u64 pc;
-};
+ };
4.12 KVM_SET_REGS
+-----------------
-Capability: basic
-Architectures: all except ARM, arm64
-Type: vcpu ioctl
-Parameters: struct kvm_regs (in)
-Returns: 0 on success, -1 on error
+:Capability: basic
+:Architectures: all except ARM, arm64
+:Type: vcpu ioctl
+:Parameters: struct kvm_regs (in)
+:Returns: 0 on success, -1 on error
Writes the general purpose registers into the vcpu.
@@ -408,17 +442,20 @@
4.13 KVM_GET_SREGS
+------------------
-Capability: basic
-Architectures: x86, ppc
-Type: vcpu ioctl
-Parameters: struct kvm_sregs (out)
-Returns: 0 on success, -1 on error
+:Capability: basic
+:Architectures: x86, ppc
+:Type: vcpu ioctl
+:Parameters: struct kvm_sregs (out)
+:Returns: 0 on success, -1 on error
Reads special registers from the vcpu.
-/* x86 */
-struct kvm_sregs {
+::
+
+ /* x86 */
+ struct kvm_sregs {
struct kvm_segment cs, ds, es, fs, gs, ss;
struct kvm_segment tr, ldt;
struct kvm_dtable gdt, idt;
@@ -426,9 +463,9 @@
__u64 efer;
__u64 apic_base;
__u64 interrupt_bitmap[(KVM_NR_INTERRUPTS + 63) / 64];
-};
+ };
-/* ppc -- see arch/powerpc/include/uapi/asm/kvm.h */
+ /* ppc -- see arch/powerpc/include/uapi/asm/kvm.h */
interrupt_bitmap is a bitmap of pending external interrupts. At most
one bit may be set. This interrupt has been acknowledged by the APIC
@@ -436,29 +473,33 @@
4.14 KVM_SET_SREGS
+------------------
-Capability: basic
-Architectures: x86, ppc
-Type: vcpu ioctl
-Parameters: struct kvm_sregs (in)
-Returns: 0 on success, -1 on error
+:Capability: basic
+:Architectures: x86, ppc
+:Type: vcpu ioctl
+:Parameters: struct kvm_sregs (in)
+:Returns: 0 on success, -1 on error
Writes special registers into the vcpu. See KVM_GET_SREGS for the
data structures.
4.15 KVM_TRANSLATE
+------------------
-Capability: basic
-Architectures: x86
-Type: vcpu ioctl
-Parameters: struct kvm_translation (in/out)
-Returns: 0 on success, -1 on error
+:Capability: basic
+:Architectures: x86
+:Type: vcpu ioctl
+:Parameters: struct kvm_translation (in/out)
+:Returns: 0 on success, -1 on error
Translates a virtual address according to the vcpu's current address
translation mode.
-struct kvm_translation {
+::
+
+ struct kvm_translation {
/* in */
__u64 linear_address;
@@ -468,59 +509,68 @@
__u8 writeable;
__u8 usermode;
__u8 pad[5];
-};
+ };
4.16 KVM_INTERRUPT
+------------------
-Capability: basic
-Architectures: x86, ppc, mips
-Type: vcpu ioctl
-Parameters: struct kvm_interrupt (in)
-Returns: 0 on success, negative on failure.
+:Capability: basic
+:Architectures: x86, ppc, mips
+:Type: vcpu ioctl
+:Parameters: struct kvm_interrupt (in)
+:Returns: 0 on success, negative on failure.
Queues a hardware interrupt vector to be injected.
-/* for KVM_INTERRUPT */
-struct kvm_interrupt {
+::
+
+ /* for KVM_INTERRUPT */
+ struct kvm_interrupt {
/* in */
__u32 irq;
-};
+ };
X86:
+^^^^
-Returns: 0 on success,
- -EEXIST if an interrupt is already enqueued
- -EINVAL the the irq number is invalid
- -ENXIO if the PIC is in the kernel
- -EFAULT if the pointer is invalid
+:Returns:
+
+ ========= ===================================
+ 0 on success,
+ -EEXIST if an interrupt is already enqueued
+ -EINVAL the irq number is invalid
+ -ENXIO if the PIC is in the kernel
+ -EFAULT if the pointer is invalid
+ ========= ===================================
Note 'irq' is an interrupt vector, not an interrupt pin or line. This
ioctl is useful if the in-kernel PIC is not used.
PPC:
+^^^^
Queues an external interrupt to be injected. This ioctl is overleaded
with 3 different irq values:
a) KVM_INTERRUPT_SET
- This injects an edge type external interrupt into the guest once it's ready
- to receive interrupts. When injected, the interrupt is done.
+ This injects an edge type external interrupt into the guest once it's ready
+ to receive interrupts. When injected, the interrupt is done.
b) KVM_INTERRUPT_UNSET
- This unsets any pending interrupt.
+ This unsets any pending interrupt.
- Only available with KVM_CAP_PPC_UNSET_IRQ.
+ Only available with KVM_CAP_PPC_UNSET_IRQ.
c) KVM_INTERRUPT_SET_LEVEL
- This injects a level type external interrupt into the guest context. The
- interrupt stays pending until a specific ioctl with KVM_INTERRUPT_UNSET
- is triggered.
+ This injects a level type external interrupt into the guest context. The
+ interrupt stays pending until a specific ioctl with KVM_INTERRUPT_UNSET
+ is triggered.
- Only available with KVM_CAP_PPC_IRQ_LEVEL.
+ Only available with KVM_CAP_PPC_IRQ_LEVEL.
Note that any value for 'irq' other than the ones stated above is invalid
and incurs unexpected behavior.
@@ -528,6 +578,7 @@
This is an asynchronous vcpu ioctl and can be invoked from any thread.
MIPS:
+^^^^^
Queues an external interrupt to be injected into the virtual CPU. A negative
interrupt number dequeues the interrupt.
@@ -536,24 +587,26 @@
4.17 KVM_DEBUG_GUEST
+--------------------
-Capability: basic
-Architectures: none
-Type: vcpu ioctl
-Parameters: none)
-Returns: -1 on error
+:Capability: basic
+:Architectures: none
+:Type: vcpu ioctl
+:Parameters: none)
+:Returns: -1 on error
Support for this has been removed. Use KVM_SET_GUEST_DEBUG instead.
4.18 KVM_GET_MSRS
+-----------------
-Capability: basic (vcpu), KVM_CAP_GET_MSR_FEATURES (system)
-Architectures: x86
-Type: system ioctl, vcpu ioctl
-Parameters: struct kvm_msrs (in/out)
-Returns: number of msrs successfully returned;
- -1 on error
+:Capability: basic (vcpu), KVM_CAP_GET_MSR_FEATURES (system)
+:Architectures: x86
+:Type: system ioctl, vcpu ioctl
+:Parameters: struct kvm_msrs (in/out)
+:Returns: number of msrs successfully returned;
+ -1 on error
When used as a system ioctl:
Reads the values of MSR-based features that are available for the VM. This
@@ -565,18 +618,20 @@
Reads model-specific registers from the vcpu. Supported msr indices can
be obtained using KVM_GET_MSR_INDEX_LIST in a system ioctl.
-struct kvm_msrs {
+::
+
+ struct kvm_msrs {
__u32 nmsrs; /* number of msrs in entries */
__u32 pad;
struct kvm_msr_entry entries[0];
-};
+ };
-struct kvm_msr_entry {
+ struct kvm_msr_entry {
__u32 index;
__u32 reserved;
__u64 data;
-};
+ };
Application code should set the 'nmsrs' member (which indicates the
size of the entries array) and the 'index' member of each array entry.
@@ -584,12 +639,13 @@
4.19 KVM_SET_MSRS
+-----------------
-Capability: basic
-Architectures: x86
-Type: vcpu ioctl
-Parameters: struct kvm_msrs (in)
-Returns: number of msrs successfully set (see below), -1 on error
+:Capability: basic
+:Architectures: x86
+:Type: vcpu ioctl
+:Parameters: struct kvm_msrs (in)
+:Returns: number of msrs successfully set (see below), -1 on error
Writes model-specific registers to the vcpu. See KVM_GET_MSRS for the
data structures.
@@ -605,41 +661,48 @@
4.20 KVM_SET_CPUID
+------------------
-Capability: basic
-Architectures: x86
-Type: vcpu ioctl
-Parameters: struct kvm_cpuid (in)
-Returns: 0 on success, -1 on error
+:Capability: basic
+:Architectures: x86
+:Type: vcpu ioctl
+:Parameters: struct kvm_cpuid (in)
+:Returns: 0 on success, -1 on error
Defines the vcpu responses to the cpuid instruction. Applications
should use the KVM_SET_CPUID2 ioctl if available.
+Note, when this IOCTL fails, KVM gives no guarantees that previous valid CPUID
+configuration (if there is) is not corrupted. Userspace can get a copy of the
+resulting CPUID configuration through KVM_GET_CPUID2 in case.
-struct kvm_cpuid_entry {
+::
+
+ struct kvm_cpuid_entry {
__u32 function;
__u32 eax;
__u32 ebx;
__u32 ecx;
__u32 edx;
__u32 padding;
-};
+ };
-/* for KVM_SET_CPUID */
-struct kvm_cpuid {
+ /* for KVM_SET_CPUID */
+ struct kvm_cpuid {
__u32 nent;
__u32 padding;
struct kvm_cpuid_entry entries[0];
-};
+ };
4.21 KVM_SET_SIGNAL_MASK
+------------------------
-Capability: basic
-Architectures: all
-Type: vcpu ioctl
-Parameters: struct kvm_signal_mask (in)
-Returns: 0 on success, -1 on error
+:Capability: basic
+:Architectures: all
+:Type: vcpu ioctl
+:Parameters: struct kvm_signal_mask (in)
+:Returns: 0 on success, -1 on error
Defines which signals are blocked during execution of KVM_RUN. This
signal mask temporarily overrides the threads signal mask. Any
@@ -649,25 +712,30 @@
Note the signal will only be delivered if not blocked by the original
signal mask.
-/* for KVM_SET_SIGNAL_MASK */
-struct kvm_signal_mask {
+::
+
+ /* for KVM_SET_SIGNAL_MASK */
+ struct kvm_signal_mask {
__u32 len;
__u8 sigset[0];
-};
+ };
4.22 KVM_GET_FPU
+----------------
-Capability: basic
-Architectures: x86
-Type: vcpu ioctl
-Parameters: struct kvm_fpu (out)
-Returns: 0 on success, -1 on error
+:Capability: basic
+:Architectures: x86
+:Type: vcpu ioctl
+:Parameters: struct kvm_fpu (out)
+:Returns: 0 on success, -1 on error
Reads the floating point state from the vcpu.
-/* for KVM_GET_FPU and KVM_SET_FPU */
-struct kvm_fpu {
+::
+
+ /* for KVM_GET_FPU and KVM_SET_FPU */
+ struct kvm_fpu {
__u8 fpr[8][16];
__u16 fcw;
__u16 fsw;
@@ -679,21 +747,24 @@
__u8 xmm[16][16];
__u32 mxcsr;
__u32 pad2;
-};
+ };
4.23 KVM_SET_FPU
+----------------
-Capability: basic
-Architectures: x86
-Type: vcpu ioctl
-Parameters: struct kvm_fpu (in)
-Returns: 0 on success, -1 on error
+:Capability: basic
+:Architectures: x86
+:Type: vcpu ioctl
+:Parameters: struct kvm_fpu (in)
+:Returns: 0 on success, -1 on error
Writes the floating point state to the vcpu.
-/* for KVM_GET_FPU and KVM_SET_FPU */
-struct kvm_fpu {
+::
+
+ /* for KVM_GET_FPU and KVM_SET_FPU */
+ struct kvm_fpu {
__u8 fpr[8][16];
__u16 fcw;
__u16 fsw;
@@ -705,16 +776,17 @@
__u8 xmm[16][16];
__u32 mxcsr;
__u32 pad2;
-};
+ };
4.24 KVM_CREATE_IRQCHIP
+-----------------------
-Capability: KVM_CAP_IRQCHIP, KVM_CAP_S390_IRQCHIP (s390)
-Architectures: x86, ARM, arm64, s390
-Type: vm ioctl
-Parameters: none
-Returns: 0 on success, -1 on error
+:Capability: KVM_CAP_IRQCHIP, KVM_CAP_S390_IRQCHIP (s390)
+:Architectures: x86, ARM, arm64, s390
+:Type: vm ioctl
+:Parameters: none
+:Returns: 0 on success, -1 on error
Creates an interrupt controller model in the kernel.
On x86, creates a virtual ioapic, a virtual PIC (two PICs, nested), and sets up
@@ -730,12 +802,13 @@
4.25 KVM_IRQ_LINE
+-----------------
-Capability: KVM_CAP_IRQCHIP
-Architectures: x86, arm, arm64
-Type: vm ioctl
-Parameters: struct kvm_irq_level
-Returns: 0 on success, -1 on error
+:Capability: KVM_CAP_IRQCHIP
+:Architectures: x86, arm, arm64
+:Type: vm ioctl
+:Parameters: struct kvm_irq_level
+:Returns: 0 on success, -1 on error
Sets the level of a GSI input to the interrupt controller model in the kernel.
On some architectures it is required that an interrupt controller model has
@@ -759,16 +832,20 @@
ARM/arm64 can signal an interrupt either at the CPU level, or at the
in-kernel irqchip (GIC), and for in-kernel irqchip can tell the GIC to
use PPIs designated for specific cpus. The irq field is interpreted
-like this:
+like this::
bits: | 31 ... 28 | 27 ... 24 | 23 ... 16 | 15 ... 0 |
field: | vcpu2_index | irq_type | vcpu_index | irq_id |
The irq_type field has the following values:
-- irq_type[0]: out-of-kernel GIC: irq_id 0 is IRQ, irq_id 1 is FIQ
-- irq_type[1]: in-kernel GIC: SPI, irq_id between 32 and 1019 (incl.)
+
+- irq_type[0]:
+ out-of-kernel GIC: irq_id 0 is IRQ, irq_id 1 is FIQ
+- irq_type[1]:
+ in-kernel GIC: SPI, irq_id between 32 and 1019 (incl.)
(the vcpu_index field is ignored)
-- irq_type[2]: in-kernel GIC: PPI, irq_id between 16 and 31 (incl.)
+- irq_type[2]:
+ in-kernel GIC: PPI, irq_id between 16 and 31 (incl.)
(The irq_id field thus corresponds nicely to the IRQ ID in the ARM GIC specs)
@@ -782,27 +859,32 @@
injection of interrupts for the in-kernel irqchip. KVM_IRQ_LINE can always
be used for a userspace interrupt controller.
-struct kvm_irq_level {
+::
+
+ struct kvm_irq_level {
union {
__u32 irq; /* GSI */
__s32 status; /* not used for KVM_IRQ_LEVEL */
};
__u32 level; /* 0 or 1 */
-};
+ };
4.26 KVM_GET_IRQCHIP
+--------------------
-Capability: KVM_CAP_IRQCHIP
-Architectures: x86
-Type: vm ioctl
-Parameters: struct kvm_irqchip (in/out)
-Returns: 0 on success, -1 on error
+:Capability: KVM_CAP_IRQCHIP
+:Architectures: x86
+:Type: vm ioctl
+:Parameters: struct kvm_irqchip (in/out)
+:Returns: 0 on success, -1 on error
Reads the state of a kernel interrupt controller created with
KVM_CREATE_IRQCHIP into a buffer provided by the caller.
-struct kvm_irqchip {
+::
+
+ struct kvm_irqchip {
__u32 chip_id; /* 0 = PIC1, 1 = PIC2, 2 = IOAPIC */
__u32 pad;
union {
@@ -810,21 +892,24 @@
struct kvm_pic_state pic;
struct kvm_ioapic_state ioapic;
} chip;
-};
+ };
4.27 KVM_SET_IRQCHIP
+--------------------
-Capability: KVM_CAP_IRQCHIP
-Architectures: x86
-Type: vm ioctl
-Parameters: struct kvm_irqchip (in)
-Returns: 0 on success, -1 on error
+:Capability: KVM_CAP_IRQCHIP
+:Architectures: x86
+:Type: vm ioctl
+:Parameters: struct kvm_irqchip (in)
+:Returns: 0 on success, -1 on error
Sets the state of a kernel interrupt controller created with
KVM_CREATE_IRQCHIP from a buffer provided by the caller.
-struct kvm_irqchip {
+::
+
+ struct kvm_irqchip {
__u32 chip_id; /* 0 = PIC1, 1 = PIC2, 2 = IOAPIC */
__u32 pad;
union {
@@ -832,16 +917,17 @@
struct kvm_pic_state pic;
struct kvm_ioapic_state ioapic;
} chip;
-};
+ };
4.28 KVM_XEN_HVM_CONFIG
+-----------------------
-Capability: KVM_CAP_XEN_HVM
-Architectures: x86
-Type: vm ioctl
-Parameters: struct kvm_xen_hvm_config (in)
-Returns: 0 on success, -1 on error
+:Capability: KVM_CAP_XEN_HVM
+:Architectures: x86
+:Type: vm ioctl
+:Parameters: struct kvm_xen_hvm_config (in)
+:Returns: 0 on success, -1 on error
Sets the MSR that the Xen HVM guest uses to initialize its hypercall
page, and provides the starting address and size of the hypercall
@@ -849,7 +935,9 @@
page of a blob (32- or 64-bit, depending on the vcpu mode) to guest
memory.
-struct kvm_xen_hvm_config {
+::
+
+ struct kvm_xen_hvm_config {
__u32 flags;
__u32 msr;
__u64 blob_addr_32;
@@ -857,16 +945,17 @@
__u8 blob_size_32;
__u8 blob_size_64;
__u8 pad2[30];
-};
+ };
4.29 KVM_GET_CLOCK
+------------------
-Capability: KVM_CAP_ADJUST_CLOCK
-Architectures: x86
-Type: vm ioctl
-Parameters: struct kvm_clock_data (out)
-Returns: 0 on success, -1 on error
+:Capability: KVM_CAP_ADJUST_CLOCK
+:Architectures: x86
+:Type: vm ioctl
+:Parameters: struct kvm_clock_data (out)
+:Returns: 0 on success, -1 on error
Gets the current timestamp of kvmclock as seen by the current guest. In
conjunction with KVM_SET_CLOCK, it is used to ensure monotonicity on scenarios
@@ -883,47 +972,56 @@
but the exact value read by each VCPU could differ, because the host
TSC is not stable.
-struct kvm_clock_data {
+::
+
+ struct kvm_clock_data {
__u64 clock; /* kvmclock current value */
__u32 flags;
__u32 pad[9];
-};
+ };
4.30 KVM_SET_CLOCK
+------------------
-Capability: KVM_CAP_ADJUST_CLOCK
-Architectures: x86
-Type: vm ioctl
-Parameters: struct kvm_clock_data (in)
-Returns: 0 on success, -1 on error
+:Capability: KVM_CAP_ADJUST_CLOCK
+:Architectures: x86
+:Type: vm ioctl
+:Parameters: struct kvm_clock_data (in)
+:Returns: 0 on success, -1 on error
Sets the current timestamp of kvmclock to the value specified in its parameter.
In conjunction with KVM_GET_CLOCK, it is used to ensure monotonicity on scenarios
such as migration.
-struct kvm_clock_data {
+::
+
+ struct kvm_clock_data {
__u64 clock; /* kvmclock current value */
__u32 flags;
__u32 pad[9];
-};
+ };
4.31 KVM_GET_VCPU_EVENTS
+------------------------
-Capability: KVM_CAP_VCPU_EVENTS
-Extended by: KVM_CAP_INTR_SHADOW
-Architectures: x86, arm, arm64
-Type: vcpu ioctl
-Parameters: struct kvm_vcpu_event (out)
-Returns: 0 on success, -1 on error
+:Capability: KVM_CAP_VCPU_EVENTS
+:Extended by: KVM_CAP_INTR_SHADOW
+:Architectures: x86, arm, arm64
+:Type: vcpu ioctl
+:Parameters: struct kvm_vcpu_event (out)
+:Returns: 0 on success, -1 on error
X86:
+^^^^
Gets currently pending exceptions, interrupts, and NMIs as well as related
states of the vcpu.
-struct kvm_vcpu_events {
+::
+
+ struct kvm_vcpu_events {
struct {
__u8 injected;
__u8 nr;
@@ -954,7 +1052,7 @@
__u8 reserved[27];
__u8 exception_has_payload;
__u64 exception_payload;
-};
+ };
The following bits are defined in the flags field:
@@ -970,6 +1068,7 @@
KVM_CAP_EXCEPTION_PAYLOAD is enabled.
ARM/ARM64:
+^^^^^^^^^^
If the guest accesses a device that is being emulated by the host kernel in
such a way that a real device would generate a physical SError, KVM may make
@@ -1005,27 +1104,36 @@
-EINVAL. Setting anything other than the lower 24bits of exception.serror_esr
will return -EINVAL.
-struct kvm_vcpu_events {
+It is not possible to read back a pending external abort (injected via
+KVM_SET_VCPU_EVENTS or otherwise) because such an exception is always delivered
+directly to the virtual CPU).
+
+::
+
+ struct kvm_vcpu_events {
struct {
__u8 serror_pending;
__u8 serror_has_esr;
+ __u8 ext_dabt_pending;
/* Align it to 8 bytes */
- __u8 pad[6];
+ __u8 pad[5];
__u64 serror_esr;
} exception;
__u32 reserved[12];
-};
+ };
4.32 KVM_SET_VCPU_EVENTS
+------------------------
-Capability: KVM_CAP_VCPU_EVENTS
-Extended by: KVM_CAP_INTR_SHADOW
-Architectures: x86, arm, arm64
-Type: vcpu ioctl
-Parameters: struct kvm_vcpu_event (in)
-Returns: 0 on success, -1 on error
+:Capability: KVM_CAP_VCPU_EVENTS
+:Extended by: KVM_CAP_INTR_SHADOW
+:Architectures: x86, arm, arm64
+:Type: vcpu ioctl
+:Parameters: struct kvm_vcpu_event (in)
+:Returns: 0 on success, -1 on error
X86:
+^^^^
Set pending exceptions, interrupts, and NMIs as well as related states of the
vcpu.
@@ -1037,9 +1145,11 @@
smi.pending. Keep the corresponding bits in the flags field cleared to
suppress overwriting the current in-kernel state. The bits are:
-KVM_VCPUEVENT_VALID_NMI_PENDING - transfer nmi.pending to the kernel
-KVM_VCPUEVENT_VALID_SIPI_VECTOR - transfer sipi_vector
-KVM_VCPUEVENT_VALID_SMM - transfer the smi sub-struct.
+=============================== ==================================
+KVM_VCPUEVENT_VALID_NMI_PENDING transfer nmi.pending to the kernel
+KVM_VCPUEVENT_VALID_SIPI_VECTOR transfer sipi_vector
+KVM_VCPUEVENT_VALID_SMM transfer the smi sub-struct.
+=============================== ==================================
If KVM_CAP_INTR_SHADOW is available, KVM_VCPUEVENT_VALID_SHADOW can be set in
the flags field to signal that interrupt.shadow contains a valid state and
@@ -1053,39 +1163,58 @@
contain a valid state and shall be written into the VCPU.
ARM/ARM64:
+^^^^^^^^^^
+
+User space may need to inject several types of events to the guest.
Set the pending SError exception state for this VCPU. It is not possible to
'cancel' an Serror that has been made pending.
+If the guest performed an access to I/O memory which could not be handled by
+userspace, for example because of missing instruction syndrome decode
+information or because there is no device mapped at the accessed IPA, then
+userspace can ask the kernel to inject an external abort using the address
+from the exiting fault on the VCPU. It is a programming error to set
+ext_dabt_pending after an exit which was not either KVM_EXIT_MMIO or
+KVM_EXIT_ARM_NISV. This feature is only available if the system supports
+KVM_CAP_ARM_INJECT_EXT_DABT. This is a helper which provides commonality in
+how userspace reports accesses for the above cases to guests, across different
+userspace implementations. Nevertheless, userspace can still emulate all Arm
+exceptions by manipulating individual registers using the KVM_SET_ONE_REG API.
+
See KVM_GET_VCPU_EVENTS for the data structure.
4.33 KVM_GET_DEBUGREGS
+----------------------
-Capability: KVM_CAP_DEBUGREGS
-Architectures: x86
-Type: vm ioctl
-Parameters: struct kvm_debugregs (out)
-Returns: 0 on success, -1 on error
+:Capability: KVM_CAP_DEBUGREGS
+:Architectures: x86
+:Type: vm ioctl
+:Parameters: struct kvm_debugregs (out)
+:Returns: 0 on success, -1 on error
Reads debug registers from the vcpu.
-struct kvm_debugregs {
+::
+
+ struct kvm_debugregs {
__u64 db[4];
__u64 dr6;
__u64 dr7;
__u64 flags;
__u64 reserved[9];
-};
+ };
4.34 KVM_SET_DEBUGREGS
+----------------------
-Capability: KVM_CAP_DEBUGREGS
-Architectures: x86
-Type: vm ioctl
-Parameters: struct kvm_debugregs (in)
-Returns: 0 on success, -1 on error
+:Capability: KVM_CAP_DEBUGREGS
+:Architectures: x86
+:Type: vm ioctl
+:Parameters: struct kvm_debugregs (in)
+:Returns: 0 on success, -1 on error
Writes debug registers into the vcpu.
@@ -1094,24 +1223,27 @@
4.35 KVM_SET_USER_MEMORY_REGION
+-------------------------------
-Capability: KVM_CAP_USER_MEMORY
-Architectures: all
-Type: vm ioctl
-Parameters: struct kvm_userspace_memory_region (in)
-Returns: 0 on success, -1 on error
+:Capability: KVM_CAP_USER_MEMORY
+:Architectures: all
+:Type: vm ioctl
+:Parameters: struct kvm_userspace_memory_region (in)
+:Returns: 0 on success, -1 on error
-struct kvm_userspace_memory_region {
+::
+
+ struct kvm_userspace_memory_region {
__u32 slot;
__u32 flags;
__u64 guest_phys_addr;
__u64 memory_size; /* bytes */
__u64 userspace_addr; /* start of the userspace allocated memory */
-};
+ };
-/* for kvm_memory_region::flags */
-#define KVM_MEM_LOG_DIRTY_PAGES (1UL << 0)
-#define KVM_MEM_READONLY (1UL << 1)
+ /* for kvm_memory_region::flags */
+ #define KVM_MEM_LOG_DIRTY_PAGES (1UL << 0)
+ #define KVM_MEM_READONLY (1UL << 1)
This ioctl allows the user to create, modify or delete a guest physical
memory slot. Bits 0-15 of "slot" specify the slot id and this value
@@ -1160,12 +1292,13 @@
4.36 KVM_SET_TSS_ADDR
+---------------------
-Capability: KVM_CAP_SET_TSS_ADDR
-Architectures: x86
-Type: vm ioctl
-Parameters: unsigned long tss_address (in)
-Returns: 0 on success, -1 on error
+:Capability: KVM_CAP_SET_TSS_ADDR
+:Architectures: x86
+:Type: vm ioctl
+:Parameters: unsigned long tss_address (in)
+:Returns: 0 on success, -1 on error
This ioctl defines the physical address of a three-page region in the guest
physical address space. The region must be within the first 4GB of the
@@ -1179,21 +1312,24 @@
4.37 KVM_ENABLE_CAP
+-------------------
-Capability: KVM_CAP_ENABLE_CAP
-Architectures: mips, ppc, s390
-Type: vcpu ioctl
-Parameters: struct kvm_enable_cap (in)
-Returns: 0 on success; -1 on error
+:Capability: KVM_CAP_ENABLE_CAP
+:Architectures: mips, ppc, s390
+:Type: vcpu ioctl
+:Parameters: struct kvm_enable_cap (in)
+:Returns: 0 on success; -1 on error
-Capability: KVM_CAP_ENABLE_CAP_VM
-Architectures: all
-Type: vcpu ioctl
-Parameters: struct kvm_enable_cap (in)
-Returns: 0 on success; -1 on error
+:Capability: KVM_CAP_ENABLE_CAP_VM
+:Architectures: all
+:Type: vm ioctl
+:Parameters: struct kvm_enable_cap (in)
+:Returns: 0 on success; -1 on error
-+Not all extensions are enabled by default. Using this ioctl the application
-can enable an extension, making it available to the guest.
+.. note::
+
+ Not all extensions are enabled by default. Using this ioctl the application
+ can enable an extension, making it available to the guest.
On systems that do not support this ioctl, it always fails. On systems that
do support it, it only works for extensions that are supported for enablement.
@@ -1201,76 +1337,91 @@
To check if a capability can be enabled, the KVM_CHECK_EXTENSION ioctl should
be used.
-struct kvm_enable_cap {
+::
+
+ struct kvm_enable_cap {
/* in */
__u32 cap;
The capability that is supposed to get enabled.
+::
+
__u32 flags;
A bitfield indicating future enhancements. Has to be 0 for now.
+::
+
__u64 args[4];
Arguments for enabling a feature. If a feature needs initial values to
function properly, this is the place to put them.
+::
+
__u8 pad[64];
-};
+ };
The vcpu ioctl should be used for vcpu-specific capabilities, the vm ioctl
for vm-wide capabilities.
4.38 KVM_GET_MP_STATE
+---------------------
-Capability: KVM_CAP_MP_STATE
-Architectures: x86, s390, arm, arm64
-Type: vcpu ioctl
-Parameters: struct kvm_mp_state (out)
-Returns: 0 on success; -1 on error
+:Capability: KVM_CAP_MP_STATE
+:Architectures: x86, s390, arm, arm64
+:Type: vcpu ioctl
+:Parameters: struct kvm_mp_state (out)
+:Returns: 0 on success; -1 on error
-struct kvm_mp_state {
+::
+
+ struct kvm_mp_state {
__u32 mp_state;
-};
+ };
Returns the vcpu's current "multiprocessing state" (though also valid on
uniprocessor guests).
Possible values are:
- - KVM_MP_STATE_RUNNABLE: the vcpu is currently running [x86,arm/arm64]
- - KVM_MP_STATE_UNINITIALIZED: the vcpu is an application processor (AP)
+ ========================== ===============================================
+ KVM_MP_STATE_RUNNABLE the vcpu is currently running [x86,arm/arm64]
+ KVM_MP_STATE_UNINITIALIZED the vcpu is an application processor (AP)
which has not yet received an INIT signal [x86]
- - KVM_MP_STATE_INIT_RECEIVED: the vcpu has received an INIT signal, and is
+ KVM_MP_STATE_INIT_RECEIVED the vcpu has received an INIT signal, and is
now ready for a SIPI [x86]
- - KVM_MP_STATE_HALTED: the vcpu has executed a HLT instruction and
+ KVM_MP_STATE_HALTED the vcpu has executed a HLT instruction and
is waiting for an interrupt [x86]
- - KVM_MP_STATE_SIPI_RECEIVED: the vcpu has just received a SIPI (vector
+ KVM_MP_STATE_SIPI_RECEIVED the vcpu has just received a SIPI (vector
accessible via KVM_GET_VCPU_EVENTS) [x86]
- - KVM_MP_STATE_STOPPED: the vcpu is stopped [s390,arm/arm64]
- - KVM_MP_STATE_CHECK_STOP: the vcpu is in a special error state [s390]
- - KVM_MP_STATE_OPERATING: the vcpu is operating (running or halted)
+ KVM_MP_STATE_STOPPED the vcpu is stopped [s390,arm/arm64]
+ KVM_MP_STATE_CHECK_STOP the vcpu is in a special error state [s390]
+ KVM_MP_STATE_OPERATING the vcpu is operating (running or halted)
[s390]
- - KVM_MP_STATE_LOAD: the vcpu is in a special load/startup state
+ KVM_MP_STATE_LOAD the vcpu is in a special load/startup state
[s390]
+ ========================== ===============================================
On x86, this ioctl is only useful after KVM_CREATE_IRQCHIP. Without an
in-kernel irqchip, the multiprocessing state must be maintained by userspace on
these architectures.
For arm/arm64:
+^^^^^^^^^^^^^^
The only states that are valid are KVM_MP_STATE_STOPPED and
KVM_MP_STATE_RUNNABLE which reflect if the vcpu is paused or not.
4.39 KVM_SET_MP_STATE
+---------------------
-Capability: KVM_CAP_MP_STATE
-Architectures: x86, s390, arm, arm64
-Type: vcpu ioctl
-Parameters: struct kvm_mp_state (in)
-Returns: 0 on success; -1 on error
+:Capability: KVM_CAP_MP_STATE
+:Architectures: x86, s390, arm, arm64
+:Type: vcpu ioctl
+:Parameters: struct kvm_mp_state (in)
+:Returns: 0 on success; -1 on error
Sets the vcpu's current "multiprocessing state"; see KVM_GET_MP_STATE for
arguments.
@@ -1280,17 +1431,19 @@
these architectures.
For arm/arm64:
+^^^^^^^^^^^^^^
The only states that are valid are KVM_MP_STATE_STOPPED and
KVM_MP_STATE_RUNNABLE which reflect if the vcpu should be paused or not.
4.40 KVM_SET_IDENTITY_MAP_ADDR
+------------------------------
-Capability: KVM_CAP_SET_IDENTITY_MAP_ADDR
-Architectures: x86
-Type: vm ioctl
-Parameters: unsigned long identity (in)
-Returns: 0 on success, -1 on error
+:Capability: KVM_CAP_SET_IDENTITY_MAP_ADDR
+:Architectures: x86
+:Type: vm ioctl
+:Parameters: unsigned long identity (in)
+:Returns: 0 on success, -1 on error
This ioctl defines the physical address of a one-page region in the guest
physical address space. The region must be within the first 4GB of the
@@ -1308,12 +1461,13 @@
Fails if any VCPU has already been created.
4.41 KVM_SET_BOOT_CPU_ID
+------------------------
-Capability: KVM_CAP_SET_BOOT_CPU_ID
-Architectures: x86
-Type: vm ioctl
-Parameters: unsigned long vcpu_id
-Returns: 0 on success, -1 on error
+:Capability: KVM_CAP_SET_BOOT_CPU_ID
+:Architectures: x86
+:Type: vm ioctl
+:Parameters: unsigned long vcpu_id
+:Returns: 0 on success, -1 on error
Define which vcpu is the Bootstrap Processor (BSP). Values are the same
as the vcpu id in KVM_CREATE_VCPU. If this ioctl is not called, the default
@@ -1321,102 +1475,119 @@
4.42 KVM_GET_XSAVE
+------------------
-Capability: KVM_CAP_XSAVE
-Architectures: x86
-Type: vcpu ioctl
-Parameters: struct kvm_xsave (out)
-Returns: 0 on success, -1 on error
+:Capability: KVM_CAP_XSAVE
+:Architectures: x86
+:Type: vcpu ioctl
+:Parameters: struct kvm_xsave (out)
+:Returns: 0 on success, -1 on error
-struct kvm_xsave {
+
+::
+
+ struct kvm_xsave {
__u32 region[1024];
-};
+ };
This ioctl would copy current vcpu's xsave struct to the userspace.
4.43 KVM_SET_XSAVE
+------------------
-Capability: KVM_CAP_XSAVE
-Architectures: x86
-Type: vcpu ioctl
-Parameters: struct kvm_xsave (in)
-Returns: 0 on success, -1 on error
+:Capability: KVM_CAP_XSAVE
+:Architectures: x86
+:Type: vcpu ioctl
+:Parameters: struct kvm_xsave (in)
+:Returns: 0 on success, -1 on error
-struct kvm_xsave {
+::
+
+
+ struct kvm_xsave {
__u32 region[1024];
-};
+ };
This ioctl would copy userspace's xsave struct to the kernel.
4.44 KVM_GET_XCRS
+-----------------
-Capability: KVM_CAP_XCRS
-Architectures: x86
-Type: vcpu ioctl
-Parameters: struct kvm_xcrs (out)
-Returns: 0 on success, -1 on error
+:Capability: KVM_CAP_XCRS
+:Architectures: x86
+:Type: vcpu ioctl
+:Parameters: struct kvm_xcrs (out)
+:Returns: 0 on success, -1 on error
-struct kvm_xcr {
+::
+
+ struct kvm_xcr {
__u32 xcr;
__u32 reserved;
__u64 value;
-};
+ };
-struct kvm_xcrs {
+ struct kvm_xcrs {
__u32 nr_xcrs;
__u32 flags;
struct kvm_xcr xcrs[KVM_MAX_XCRS];
__u64 padding[16];
-};
+ };
This ioctl would copy current vcpu's xcrs to the userspace.
4.45 KVM_SET_XCRS
+-----------------
-Capability: KVM_CAP_XCRS
-Architectures: x86
-Type: vcpu ioctl
-Parameters: struct kvm_xcrs (in)
-Returns: 0 on success, -1 on error
+:Capability: KVM_CAP_XCRS
+:Architectures: x86
+:Type: vcpu ioctl
+:Parameters: struct kvm_xcrs (in)
+:Returns: 0 on success, -1 on error
-struct kvm_xcr {
+::
+
+ struct kvm_xcr {
__u32 xcr;
__u32 reserved;
__u64 value;
-};
+ };
-struct kvm_xcrs {
+ struct kvm_xcrs {
__u32 nr_xcrs;
__u32 flags;
struct kvm_xcr xcrs[KVM_MAX_XCRS];
__u64 padding[16];
-};
+ };
This ioctl would set vcpu's xcr to the value userspace specified.
4.46 KVM_GET_SUPPORTED_CPUID
+----------------------------
-Capability: KVM_CAP_EXT_CPUID
-Architectures: x86
-Type: system ioctl
-Parameters: struct kvm_cpuid2 (in/out)
-Returns: 0 on success, -1 on error
+:Capability: KVM_CAP_EXT_CPUID
+:Architectures: x86
+:Type: system ioctl
+:Parameters: struct kvm_cpuid2 (in/out)
+:Returns: 0 on success, -1 on error
-struct kvm_cpuid2 {
+::
+
+ struct kvm_cpuid2 {
__u32 nent;
__u32 padding;
struct kvm_cpuid_entry2 entries[0];
-};
+ };
-#define KVM_CPUID_FLAG_SIGNIFCANT_INDEX BIT(0)
-#define KVM_CPUID_FLAG_STATEFUL_FUNC BIT(1)
-#define KVM_CPUID_FLAG_STATE_READ_NEXT BIT(2)
+ #define KVM_CPUID_FLAG_SIGNIFCANT_INDEX BIT(0)
+ #define KVM_CPUID_FLAG_STATEFUL_FUNC BIT(1) /* deprecated */
+ #define KVM_CPUID_FLAG_STATE_READ_NEXT BIT(2) /* deprecated */
-struct kvm_cpuid_entry2 {
+ struct kvm_cpuid_entry2 {
__u32 function;
__u32 index;
__u32 flags;
@@ -1425,7 +1596,7 @@
__u32 ecx;
__u32 edx;
__u32 padding[3];
-};
+ };
This ioctl returns x86 cpuid features which are supported by both the
hardware and kvm in its default configuration. Userspace can use the
@@ -1453,25 +1624,26 @@
x2apic), may not be present in the host cpu, but are exposed by kvm if it can
emulate them efficiently. The fields in each entry are defined as follows:
- function: the eax value used to obtain the entry
- index: the ecx value used to obtain the entry (for entries that are
+ function:
+ the eax value used to obtain the entry
+
+ index:
+ the ecx value used to obtain the entry (for entries that are
affected by ecx)
- flags: an OR of zero or more of the following:
+
+ flags:
+ an OR of zero or more of the following:
+
KVM_CPUID_FLAG_SIGNIFCANT_INDEX:
if the index field is valid
- KVM_CPUID_FLAG_STATEFUL_FUNC:
- if cpuid for this function returns different values for successive
- invocations; there will be several entries with the same function,
- all with this flag set
- KVM_CPUID_FLAG_STATE_READ_NEXT:
- for KVM_CPUID_FLAG_STATEFUL_FUNC entries, set if this entry is
- the first entry to be read by a cpu
- eax, ebx, ecx, edx: the values returned by the cpuid instruction for
+
+ eax, ebx, ecx, edx:
+ the values returned by the cpuid instruction for
this function/index combination
The TSC deadline timer feature (CPUID leaf 1, ecx[24]) is always returned
as false, since the feature depends on KVM_CREATE_IRQCHIP for local APIC
-support. Instead it is reported via
+support. Instead it is reported via::
ioctl(KVM_CHECK_EXTENSION, KVM_CAP_TSC_DEADLINE_TIMER)
@@ -1480,18 +1652,21 @@
4.47 KVM_PPC_GET_PVINFO
+-----------------------
-Capability: KVM_CAP_PPC_GET_PVINFO
-Architectures: ppc
-Type: vm ioctl
-Parameters: struct kvm_ppc_pvinfo (out)
-Returns: 0 on success, !0 on error
+:Capability: KVM_CAP_PPC_GET_PVINFO
+:Architectures: ppc
+:Type: vm ioctl
+:Parameters: struct kvm_ppc_pvinfo (out)
+:Returns: 0 on success, !0 on error
-struct kvm_ppc_pvinfo {
+::
+
+ struct kvm_ppc_pvinfo {
__u32 flags;
__u32 hcall[4];
__u8 pad[108];
-};
+ };
This ioctl fetches PV specific information that need to be passed to the guest
using the device tree or other means from vm context.
@@ -1501,33 +1676,39 @@
If any additional field gets added to this structure later on, a bit for that
additional piece of information will be set in the flags bitmap.
-The flags bitmap is defined as:
+The flags bitmap is defined as::
/* the host supports the ePAPR idle hcall
#define KVM_PPC_PVINFO_FLAGS_EV_IDLE (1<<0)
4.52 KVM_SET_GSI_ROUTING
+------------------------
-Capability: KVM_CAP_IRQ_ROUTING
-Architectures: x86 s390 arm arm64
-Type: vm ioctl
-Parameters: struct kvm_irq_routing (in)
-Returns: 0 on success, -1 on error
+:Capability: KVM_CAP_IRQ_ROUTING
+:Architectures: x86 s390 arm arm64
+:Type: vm ioctl
+:Parameters: struct kvm_irq_routing (in)
+:Returns: 0 on success, -1 on error
Sets the GSI routing table entries, overwriting any previously set entries.
On arm/arm64, GSI routing has the following limitation:
+
- GSI routing does not apply to KVM_IRQ_LINE but only to KVM_IRQFD.
-struct kvm_irq_routing {
+::
+
+ struct kvm_irq_routing {
__u32 nr;
__u32 flags;
struct kvm_irq_routing_entry entries[0];
-};
+ };
No flags are specified so far, the corresponding field must be set to zero.
-struct kvm_irq_routing_entry {
+::
+
+ struct kvm_irq_routing_entry {
__u32 gsi;
__u32 type;
__u32 flags;
@@ -1539,15 +1720,16 @@
struct kvm_irq_routing_hv_sint hv_sint;
__u32 pad[8];
} u;
-};
+ };
-/* gsi routing entry types */
-#define KVM_IRQ_ROUTING_IRQCHIP 1
-#define KVM_IRQ_ROUTING_MSI 2
-#define KVM_IRQ_ROUTING_S390_ADAPTER 3
-#define KVM_IRQ_ROUTING_HV_SINT 4
+ /* gsi routing entry types */
+ #define KVM_IRQ_ROUTING_IRQCHIP 1
+ #define KVM_IRQ_ROUTING_MSI 2
+ #define KVM_IRQ_ROUTING_S390_ADAPTER 3
+ #define KVM_IRQ_ROUTING_HV_SINT 4
flags:
+
- KVM_MSI_VALID_DEVID: used along with KVM_IRQ_ROUTING_MSI routing entry
type, specifies that the devid field contains a valid value. The per-VM
KVM_CAP_MSI_DEVID capability advertises the requirement to provide
@@ -1555,12 +1737,14 @@
never set the KVM_MSI_VALID_DEVID flag as the ioctl might fail.
- zero otherwise
-struct kvm_irq_routing_irqchip {
+::
+
+ struct kvm_irq_routing_irqchip {
__u32 irqchip;
__u32 pin;
-};
+ };
-struct kvm_irq_routing_msi {
+ struct kvm_irq_routing_msi {
__u32 address_lo;
__u32 address_hi;
__u32 data;
@@ -1568,7 +1752,7 @@
__u32 pad;
__u32 devid;
};
-};
+ };
If KVM_MSI_VALID_DEVID is set, devid contains a unique device identifier
for the device that wrote the MSI message. For PCI, this is usually a
@@ -1579,39 +1763,43 @@
address_hi bits 31-8 provide bits 31-8 of the destination id. Bits 7-0 of
address_hi must be zero.
-struct kvm_irq_routing_s390_adapter {
+::
+
+ struct kvm_irq_routing_s390_adapter {
__u64 ind_addr;
__u64 summary_addr;
__u64 ind_offset;
__u32 summary_offset;
__u32 adapter_id;
-};
+ };
-struct kvm_irq_routing_hv_sint {
+ struct kvm_irq_routing_hv_sint {
__u32 vcpu;
__u32 sint;
-};
+ };
4.55 KVM_SET_TSC_KHZ
+--------------------
-Capability: KVM_CAP_TSC_CONTROL
-Architectures: x86
-Type: vcpu ioctl
-Parameters: virtual tsc_khz
-Returns: 0 on success, -1 on error
+:Capability: KVM_CAP_TSC_CONTROL
+:Architectures: x86
+:Type: vcpu ioctl
+:Parameters: virtual tsc_khz
+:Returns: 0 on success, -1 on error
Specifies the tsc frequency for the virtual machine. The unit of the
frequency is KHz.
4.56 KVM_GET_TSC_KHZ
+--------------------
-Capability: KVM_CAP_GET_TSC_KHZ
-Architectures: x86
-Type: vcpu ioctl
-Parameters: none
-Returns: virtual tsc-khz on success, negative value on error
+:Capability: KVM_CAP_GET_TSC_KHZ
+:Architectures: x86
+:Type: vcpu ioctl
+:Parameters: none
+:Returns: virtual tsc-khz on success, negative value on error
Returns the tsc frequency of the guest. The unit of the return value is
KHz. If the host has unstable tsc this ioctl returns -EIO instead as an
@@ -1619,17 +1807,20 @@
4.57 KVM_GET_LAPIC
+------------------
-Capability: KVM_CAP_IRQCHIP
-Architectures: x86
-Type: vcpu ioctl
-Parameters: struct kvm_lapic_state (out)
-Returns: 0 on success, -1 on error
+:Capability: KVM_CAP_IRQCHIP
+:Architectures: x86
+:Type: vcpu ioctl
+:Parameters: struct kvm_lapic_state (out)
+:Returns: 0 on success, -1 on error
-#define KVM_APIC_REG_SIZE 0x400
-struct kvm_lapic_state {
+::
+
+ #define KVM_APIC_REG_SIZE 0x400
+ struct kvm_lapic_state {
char regs[KVM_APIC_REG_SIZE];
-};
+ };
Reads the Local APIC registers and copies them into the input argument. The
data format and layout are the same as documented in the architecture manual.
@@ -1647,17 +1838,20 @@
4.58 KVM_SET_LAPIC
+------------------
-Capability: KVM_CAP_IRQCHIP
-Architectures: x86
-Type: vcpu ioctl
-Parameters: struct kvm_lapic_state (in)
-Returns: 0 on success, -1 on error
+:Capability: KVM_CAP_IRQCHIP
+:Architectures: x86
+:Type: vcpu ioctl
+:Parameters: struct kvm_lapic_state (in)
+:Returns: 0 on success, -1 on error
-#define KVM_APIC_REG_SIZE 0x400
-struct kvm_lapic_state {
+::
+
+ #define KVM_APIC_REG_SIZE 0x400
+ struct kvm_lapic_state {
char regs[KVM_APIC_REG_SIZE];
-};
+ };
Copies the input argument into the Local APIC registers. The data format
and layout are the same as documented in the architecture manual.
@@ -1668,35 +1862,38 @@
4.59 KVM_IOEVENTFD
+------------------
-Capability: KVM_CAP_IOEVENTFD
-Architectures: all
-Type: vm ioctl
-Parameters: struct kvm_ioeventfd (in)
-Returns: 0 on success, !0 on error
+:Capability: KVM_CAP_IOEVENTFD
+:Architectures: all
+:Type: vm ioctl
+:Parameters: struct kvm_ioeventfd (in)
+:Returns: 0 on success, !0 on error
This ioctl attaches or detaches an ioeventfd to a legal pio/mmio address
within the guest. A guest write in the registered address will signal the
provided event instead of triggering an exit.
-struct kvm_ioeventfd {
+::
+
+ struct kvm_ioeventfd {
__u64 datamatch;
__u64 addr; /* legal pio/mmio address */
__u32 len; /* 0, 1, 2, 4, or 8 bytes */
__s32 fd;
__u32 flags;
__u8 pad[36];
-};
+ };
For the special case of virtio-ccw devices on s390, the ioevent is matched
to a subchannel/virtqueue tuple instead.
-The following flags are defined:
+The following flags are defined::
-#define KVM_IOEVENTFD_FLAG_DATAMATCH (1 << kvm_ioeventfd_flag_nr_datamatch)
-#define KVM_IOEVENTFD_FLAG_PIO (1 << kvm_ioeventfd_flag_nr_pio)
-#define KVM_IOEVENTFD_FLAG_DEASSIGN (1 << kvm_ioeventfd_flag_nr_deassign)
-#define KVM_IOEVENTFD_FLAG_VIRTIO_CCW_NOTIFY \
+ #define KVM_IOEVENTFD_FLAG_DATAMATCH (1 << kvm_ioeventfd_flag_nr_datamatch)
+ #define KVM_IOEVENTFD_FLAG_PIO (1 << kvm_ioeventfd_flag_nr_pio)
+ #define KVM_IOEVENTFD_FLAG_DEASSIGN (1 << kvm_ioeventfd_flag_nr_deassign)
+ #define KVM_IOEVENTFD_FLAG_VIRTIO_CCW_NOTIFY \
(1 << kvm_ioeventfd_flag_nr_virtio_ccw_notify)
If datamatch flag is set, the event will be signaled only if the written value
@@ -1711,17 +1908,20 @@
work anyway.
4.60 KVM_DIRTY_TLB
+------------------
-Capability: KVM_CAP_SW_TLB
-Architectures: ppc
-Type: vcpu ioctl
-Parameters: struct kvm_dirty_tlb (in)
-Returns: 0 on success, -1 on error
+:Capability: KVM_CAP_SW_TLB
+:Architectures: ppc
+:Type: vcpu ioctl
+:Parameters: struct kvm_dirty_tlb (in)
+:Returns: 0 on success, -1 on error
-struct kvm_dirty_tlb {
+::
+
+ struct kvm_dirty_tlb {
__u64 bitmap;
__u32 num_dirty;
-};
+ };
This must be called whenever userspace has changed an entry in the shared
TLB, prior to calling KVM_RUN on the associated vcpu.
@@ -1744,23 +1944,26 @@
4.62 KVM_CREATE_SPAPR_TCE
+-------------------------
-Capability: KVM_CAP_SPAPR_TCE
-Architectures: powerpc
-Type: vm ioctl
-Parameters: struct kvm_create_spapr_tce (in)
-Returns: file descriptor for manipulating the created TCE table
+:Capability: KVM_CAP_SPAPR_TCE
+:Architectures: powerpc
+:Type: vm ioctl
+:Parameters: struct kvm_create_spapr_tce (in)
+:Returns: file descriptor for manipulating the created TCE table
This creates a virtual TCE (translation control entry) table, which
is an IOMMU for PAPR-style virtual I/O. It is used to translate
logical addresses used in virtual I/O into guest physical addresses,
and provides a scatter/gather capability for PAPR virtual I/O.
-/* for KVM_CAP_SPAPR_TCE */
-struct kvm_create_spapr_tce {
+::
+
+ /* for KVM_CAP_SPAPR_TCE */
+ struct kvm_create_spapr_tce {
__u64 liobn;
__u32 window_size;
-};
+ };
The liobn field gives the logical IO bus number for which to create a
TCE table. The window_size field specifies the size of the DMA window
@@ -1780,12 +1983,13 @@
4.63 KVM_ALLOCATE_RMA
+---------------------
-Capability: KVM_CAP_PPC_RMA
-Architectures: powerpc
-Type: vm ioctl
-Parameters: struct kvm_allocate_rma (out)
-Returns: file descriptor for mapping the allocated RMA
+:Capability: KVM_CAP_PPC_RMA
+:Architectures: powerpc
+:Type: vm ioctl
+:Parameters: struct kvm_allocate_rma (out)
+:Returns: file descriptor for mapping the allocated RMA
This allocates a Real Mode Area (RMA) from the pool allocated at boot
time by the kernel. An RMA is a physically-contiguous, aligned region
@@ -1794,10 +1998,12 @@
POWER processors support a set of sizes for the RMA that usually
includes 64MB, 128MB, 256MB and some larger powers of two.
-/* for KVM_ALLOCATE_RMA */
-struct kvm_allocate_rma {
+::
+
+ /* for KVM_ALLOCATE_RMA */
+ struct kvm_allocate_rma {
__u64 rma_size;
-};
+ };
The return value is a file descriptor which can be passed to mmap(2)
to map the allocated RMA into userspace. The mapped area can then be
@@ -1813,12 +2019,13 @@
4.64 KVM_NMI
+------------
-Capability: KVM_CAP_USER_NMI
-Architectures: x86
-Type: vcpu ioctl
-Parameters: none
-Returns: 0 on success, -1 on error
+:Capability: KVM_CAP_USER_NMI
+:Architectures: x86
+:Type: vcpu ioctl
+:Parameters: none
+:Returns: 0 on success, -1 on error
Queues an NMI on the thread's vcpu. Note this is well defined only
when KVM_CREATE_IRQCHIP has not been called, since this is an interface
@@ -1839,14 +2046,16 @@
4.65 KVM_S390_UCAS_MAP
+----------------------
-Capability: KVM_CAP_S390_UCONTROL
-Architectures: s390
-Type: vcpu ioctl
-Parameters: struct kvm_s390_ucas_mapping (in)
-Returns: 0 in case of success
+:Capability: KVM_CAP_S390_UCONTROL
+:Architectures: s390
+:Type: vcpu ioctl
+:Parameters: struct kvm_s390_ucas_mapping (in)
+:Returns: 0 in case of success
-The parameter is defined like this:
+The parameter is defined like this::
+
struct kvm_s390_ucas_mapping {
__u64 user_addr;
__u64 vcpu_addr;
@@ -1859,14 +2068,16 @@
4.66 KVM_S390_UCAS_UNMAP
+------------------------
-Capability: KVM_CAP_S390_UCONTROL
-Architectures: s390
-Type: vcpu ioctl
-Parameters: struct kvm_s390_ucas_mapping (in)
-Returns: 0 in case of success
+:Capability: KVM_CAP_S390_UCONTROL
+:Architectures: s390
+:Type: vcpu ioctl
+:Parameters: struct kvm_s390_ucas_mapping (in)
+:Returns: 0 in case of success
-The parameter is defined like this:
+The parameter is defined like this::
+
struct kvm_s390_ucas_mapping {
__u64 user_addr;
__u64 vcpu_addr;
@@ -1879,12 +2090,13 @@
4.67 KVM_S390_VCPU_FAULT
+------------------------
-Capability: KVM_CAP_S390_UCONTROL
-Architectures: s390
-Type: vcpu ioctl
-Parameters: vcpu absolute address (in)
-Returns: 0 in case of success
+:Capability: KVM_CAP_S390_UCONTROL
+:Architectures: s390
+:Type: vcpu ioctl
+:Parameters: vcpu absolute address (in)
+:Returns: 0 in case of success
This call creates a page table entry on the virtual cpu's address space
(for user controlled virtual machines) or the virtual machine's address
@@ -1896,23 +2108,32 @@
4.68 KVM_SET_ONE_REG
+--------------------
-Capability: KVM_CAP_ONE_REG
-Architectures: all
-Type: vcpu ioctl
-Parameters: struct kvm_one_reg (in)
-Returns: 0 on success, negative value on failure
+:Capability: KVM_CAP_ONE_REG
+:Architectures: all
+:Type: vcpu ioctl
+:Parameters: struct kvm_one_reg (in)
+:Returns: 0 on success, negative value on failure
+
Errors:
- ENOENT: no such register
- EINVAL: invalid register ID, or no such register
- EPERM: (arm64) register access not allowed before vcpu finalization
+
+ ====== ============================================================
+ ENOENT no such register
+ EINVAL invalid register ID, or no such register or used with VMs in
+ protected virtualization mode on s390
+ EPERM (arm64) register access not allowed before vcpu finalization
+ ====== ============================================================
+
(These error codes are indicative only: do not rely on a specific error
code being returned in a specific situation.)
-struct kvm_one_reg {
+::
+
+ struct kvm_one_reg {
__u64 id;
__u64 addr;
-};
+ };
Using this ioctl, a single vcpu register can be set to a specific value
defined by user space with the passed in struct kvm_one_reg, where id
@@ -1922,217 +2143,229 @@
and their own constants and width. To keep track of the implemented
registers, find a list below:
- Arch | Register | Width (bits)
- | |
- PPC | KVM_REG_PPC_HIOR | 64
- PPC | KVM_REG_PPC_IAC1 | 64
- PPC | KVM_REG_PPC_IAC2 | 64
- PPC | KVM_REG_PPC_IAC3 | 64
- PPC | KVM_REG_PPC_IAC4 | 64
- PPC | KVM_REG_PPC_DAC1 | 64
- PPC | KVM_REG_PPC_DAC2 | 64
- PPC | KVM_REG_PPC_DABR | 64
- PPC | KVM_REG_PPC_DSCR | 64
- PPC | KVM_REG_PPC_PURR | 64
- PPC | KVM_REG_PPC_SPURR | 64
- PPC | KVM_REG_PPC_DAR | 64
- PPC | KVM_REG_PPC_DSISR | 32
- PPC | KVM_REG_PPC_AMR | 64
- PPC | KVM_REG_PPC_UAMOR | 64
- PPC | KVM_REG_PPC_MMCR0 | 64
- PPC | KVM_REG_PPC_MMCR1 | 64
- PPC | KVM_REG_PPC_MMCRA | 64
- PPC | KVM_REG_PPC_MMCR2 | 64
- PPC | KVM_REG_PPC_MMCRS | 64
- PPC | KVM_REG_PPC_SIAR | 64
- PPC | KVM_REG_PPC_SDAR | 64
- PPC | KVM_REG_PPC_SIER | 64
- PPC | KVM_REG_PPC_PMC1 | 32
- PPC | KVM_REG_PPC_PMC2 | 32
- PPC | KVM_REG_PPC_PMC3 | 32
- PPC | KVM_REG_PPC_PMC4 | 32
- PPC | KVM_REG_PPC_PMC5 | 32
- PPC | KVM_REG_PPC_PMC6 | 32
- PPC | KVM_REG_PPC_PMC7 | 32
- PPC | KVM_REG_PPC_PMC8 | 32
- PPC | KVM_REG_PPC_FPR0 | 64
- ...
- PPC | KVM_REG_PPC_FPR31 | 64
- PPC | KVM_REG_PPC_VR0 | 128
- ...
- PPC | KVM_REG_PPC_VR31 | 128
- PPC | KVM_REG_PPC_VSR0 | 128
- ...
- PPC | KVM_REG_PPC_VSR31 | 128
- PPC | KVM_REG_PPC_FPSCR | 64
- PPC | KVM_REG_PPC_VSCR | 32
- PPC | KVM_REG_PPC_VPA_ADDR | 64
- PPC | KVM_REG_PPC_VPA_SLB | 128
- PPC | KVM_REG_PPC_VPA_DTL | 128
- PPC | KVM_REG_PPC_EPCR | 32
- PPC | KVM_REG_PPC_EPR | 32
- PPC | KVM_REG_PPC_TCR | 32
- PPC | KVM_REG_PPC_TSR | 32
- PPC | KVM_REG_PPC_OR_TSR | 32
- PPC | KVM_REG_PPC_CLEAR_TSR | 32
- PPC | KVM_REG_PPC_MAS0 | 32
- PPC | KVM_REG_PPC_MAS1 | 32
- PPC | KVM_REG_PPC_MAS2 | 64
- PPC | KVM_REG_PPC_MAS7_3 | 64
- PPC | KVM_REG_PPC_MAS4 | 32
- PPC | KVM_REG_PPC_MAS6 | 32
- PPC | KVM_REG_PPC_MMUCFG | 32
- PPC | KVM_REG_PPC_TLB0CFG | 32
- PPC | KVM_REG_PPC_TLB1CFG | 32
- PPC | KVM_REG_PPC_TLB2CFG | 32
- PPC | KVM_REG_PPC_TLB3CFG | 32
- PPC | KVM_REG_PPC_TLB0PS | 32
- PPC | KVM_REG_PPC_TLB1PS | 32
- PPC | KVM_REG_PPC_TLB2PS | 32
- PPC | KVM_REG_PPC_TLB3PS | 32
- PPC | KVM_REG_PPC_EPTCFG | 32
- PPC | KVM_REG_PPC_ICP_STATE | 64
- PPC | KVM_REG_PPC_VP_STATE | 128
- PPC | KVM_REG_PPC_TB_OFFSET | 64
- PPC | KVM_REG_PPC_SPMC1 | 32
- PPC | KVM_REG_PPC_SPMC2 | 32
- PPC | KVM_REG_PPC_IAMR | 64
- PPC | KVM_REG_PPC_TFHAR | 64
- PPC | KVM_REG_PPC_TFIAR | 64
- PPC | KVM_REG_PPC_TEXASR | 64
- PPC | KVM_REG_PPC_FSCR | 64
- PPC | KVM_REG_PPC_PSPB | 32
- PPC | KVM_REG_PPC_EBBHR | 64
- PPC | KVM_REG_PPC_EBBRR | 64
- PPC | KVM_REG_PPC_BESCR | 64
- PPC | KVM_REG_PPC_TAR | 64
- PPC | KVM_REG_PPC_DPDES | 64
- PPC | KVM_REG_PPC_DAWR | 64
- PPC | KVM_REG_PPC_DAWRX | 64
- PPC | KVM_REG_PPC_CIABR | 64
- PPC | KVM_REG_PPC_IC | 64
- PPC | KVM_REG_PPC_VTB | 64
- PPC | KVM_REG_PPC_CSIGR | 64
- PPC | KVM_REG_PPC_TACR | 64
- PPC | KVM_REG_PPC_TCSCR | 64
- PPC | KVM_REG_PPC_PID | 64
- PPC | KVM_REG_PPC_ACOP | 64
- PPC | KVM_REG_PPC_VRSAVE | 32
- PPC | KVM_REG_PPC_LPCR | 32
- PPC | KVM_REG_PPC_LPCR_64 | 64
- PPC | KVM_REG_PPC_PPR | 64
- PPC | KVM_REG_PPC_ARCH_COMPAT | 32
- PPC | KVM_REG_PPC_DABRX | 32
- PPC | KVM_REG_PPC_WORT | 64
- PPC | KVM_REG_PPC_SPRG9 | 64
- PPC | KVM_REG_PPC_DBSR | 32
- PPC | KVM_REG_PPC_TIDR | 64
- PPC | KVM_REG_PPC_PSSCR | 64
- PPC | KVM_REG_PPC_DEC_EXPIRY | 64
- PPC | KVM_REG_PPC_PTCR | 64
- PPC | KVM_REG_PPC_TM_GPR0 | 64
- ...
- PPC | KVM_REG_PPC_TM_GPR31 | 64
- PPC | KVM_REG_PPC_TM_VSR0 | 128
- ...
- PPC | KVM_REG_PPC_TM_VSR63 | 128
- PPC | KVM_REG_PPC_TM_CR | 64
- PPC | KVM_REG_PPC_TM_LR | 64
- PPC | KVM_REG_PPC_TM_CTR | 64
- PPC | KVM_REG_PPC_TM_FPSCR | 64
- PPC | KVM_REG_PPC_TM_AMR | 64
- PPC | KVM_REG_PPC_TM_PPR | 64
- PPC | KVM_REG_PPC_TM_VRSAVE | 64
- PPC | KVM_REG_PPC_TM_VSCR | 32
- PPC | KVM_REG_PPC_TM_DSCR | 64
- PPC | KVM_REG_PPC_TM_TAR | 64
- PPC | KVM_REG_PPC_TM_XER | 64
- | |
- MIPS | KVM_REG_MIPS_R0 | 64
- ...
- MIPS | KVM_REG_MIPS_R31 | 64
- MIPS | KVM_REG_MIPS_HI | 64
- MIPS | KVM_REG_MIPS_LO | 64
- MIPS | KVM_REG_MIPS_PC | 64
- MIPS | KVM_REG_MIPS_CP0_INDEX | 32
- MIPS | KVM_REG_MIPS_CP0_ENTRYLO0 | 64
- MIPS | KVM_REG_MIPS_CP0_ENTRYLO1 | 64
- MIPS | KVM_REG_MIPS_CP0_CONTEXT | 64
- MIPS | KVM_REG_MIPS_CP0_CONTEXTCONFIG| 32
- MIPS | KVM_REG_MIPS_CP0_USERLOCAL | 64
- MIPS | KVM_REG_MIPS_CP0_XCONTEXTCONFIG| 64
- MIPS | KVM_REG_MIPS_CP0_PAGEMASK | 32
- MIPS | KVM_REG_MIPS_CP0_PAGEGRAIN | 32
- MIPS | KVM_REG_MIPS_CP0_SEGCTL0 | 64
- MIPS | KVM_REG_MIPS_CP0_SEGCTL1 | 64
- MIPS | KVM_REG_MIPS_CP0_SEGCTL2 | 64
- MIPS | KVM_REG_MIPS_CP0_PWBASE | 64
- MIPS | KVM_REG_MIPS_CP0_PWFIELD | 64
- MIPS | KVM_REG_MIPS_CP0_PWSIZE | 64
- MIPS | KVM_REG_MIPS_CP0_WIRED | 32
- MIPS | KVM_REG_MIPS_CP0_PWCTL | 32
- MIPS | KVM_REG_MIPS_CP0_HWRENA | 32
- MIPS | KVM_REG_MIPS_CP0_BADVADDR | 64
- MIPS | KVM_REG_MIPS_CP0_BADINSTR | 32
- MIPS | KVM_REG_MIPS_CP0_BADINSTRP | 32
- MIPS | KVM_REG_MIPS_CP0_COUNT | 32
- MIPS | KVM_REG_MIPS_CP0_ENTRYHI | 64
- MIPS | KVM_REG_MIPS_CP0_COMPARE | 32
- MIPS | KVM_REG_MIPS_CP0_STATUS | 32
- MIPS | KVM_REG_MIPS_CP0_INTCTL | 32
- MIPS | KVM_REG_MIPS_CP0_CAUSE | 32
- MIPS | KVM_REG_MIPS_CP0_EPC | 64
- MIPS | KVM_REG_MIPS_CP0_PRID | 32
- MIPS | KVM_REG_MIPS_CP0_EBASE | 64
- MIPS | KVM_REG_MIPS_CP0_CONFIG | 32
- MIPS | KVM_REG_MIPS_CP0_CONFIG1 | 32
- MIPS | KVM_REG_MIPS_CP0_CONFIG2 | 32
- MIPS | KVM_REG_MIPS_CP0_CONFIG3 | 32
- MIPS | KVM_REG_MIPS_CP0_CONFIG4 | 32
- MIPS | KVM_REG_MIPS_CP0_CONFIG5 | 32
- MIPS | KVM_REG_MIPS_CP0_CONFIG7 | 32
- MIPS | KVM_REG_MIPS_CP0_XCONTEXT | 64
- MIPS | KVM_REG_MIPS_CP0_ERROREPC | 64
- MIPS | KVM_REG_MIPS_CP0_KSCRATCH1 | 64
- MIPS | KVM_REG_MIPS_CP0_KSCRATCH2 | 64
- MIPS | KVM_REG_MIPS_CP0_KSCRATCH3 | 64
- MIPS | KVM_REG_MIPS_CP0_KSCRATCH4 | 64
- MIPS | KVM_REG_MIPS_CP0_KSCRATCH5 | 64
- MIPS | KVM_REG_MIPS_CP0_KSCRATCH6 | 64
- MIPS | KVM_REG_MIPS_CP0_MAAR(0..63) | 64
- MIPS | KVM_REG_MIPS_COUNT_CTL | 64
- MIPS | KVM_REG_MIPS_COUNT_RESUME | 64
- MIPS | KVM_REG_MIPS_COUNT_HZ | 64
- MIPS | KVM_REG_MIPS_FPR_32(0..31) | 32
- MIPS | KVM_REG_MIPS_FPR_64(0..31) | 64
- MIPS | KVM_REG_MIPS_VEC_128(0..31) | 128
- MIPS | KVM_REG_MIPS_FCR_IR | 32
- MIPS | KVM_REG_MIPS_FCR_CSR | 32
- MIPS | KVM_REG_MIPS_MSA_IR | 32
- MIPS | KVM_REG_MIPS_MSA_CSR | 32
+ ======= =============================== ============
+ Arch Register Width (bits)
+ ======= =============================== ============
+ PPC KVM_REG_PPC_HIOR 64
+ PPC KVM_REG_PPC_IAC1 64
+ PPC KVM_REG_PPC_IAC2 64
+ PPC KVM_REG_PPC_IAC3 64
+ PPC KVM_REG_PPC_IAC4 64
+ PPC KVM_REG_PPC_DAC1 64
+ PPC KVM_REG_PPC_DAC2 64
+ PPC KVM_REG_PPC_DABR 64
+ PPC KVM_REG_PPC_DSCR 64
+ PPC KVM_REG_PPC_PURR 64
+ PPC KVM_REG_PPC_SPURR 64
+ PPC KVM_REG_PPC_DAR 64
+ PPC KVM_REG_PPC_DSISR 32
+ PPC KVM_REG_PPC_AMR 64
+ PPC KVM_REG_PPC_UAMOR 64
+ PPC KVM_REG_PPC_MMCR0 64
+ PPC KVM_REG_PPC_MMCR1 64
+ PPC KVM_REG_PPC_MMCRA 64
+ PPC KVM_REG_PPC_MMCR2 64
+ PPC KVM_REG_PPC_MMCRS 64
+ PPC KVM_REG_PPC_MMCR3 64
+ PPC KVM_REG_PPC_SIAR 64
+ PPC KVM_REG_PPC_SDAR 64
+ PPC KVM_REG_PPC_SIER 64
+ PPC KVM_REG_PPC_SIER2 64
+ PPC KVM_REG_PPC_SIER3 64
+ PPC KVM_REG_PPC_PMC1 32
+ PPC KVM_REG_PPC_PMC2 32
+ PPC KVM_REG_PPC_PMC3 32
+ PPC KVM_REG_PPC_PMC4 32
+ PPC KVM_REG_PPC_PMC5 32
+ PPC KVM_REG_PPC_PMC6 32
+ PPC KVM_REG_PPC_PMC7 32
+ PPC KVM_REG_PPC_PMC8 32
+ PPC KVM_REG_PPC_FPR0 64
+ ...
+ PPC KVM_REG_PPC_FPR31 64
+ PPC KVM_REG_PPC_VR0 128
+ ...
+ PPC KVM_REG_PPC_VR31 128
+ PPC KVM_REG_PPC_VSR0 128
+ ...
+ PPC KVM_REG_PPC_VSR31 128
+ PPC KVM_REG_PPC_FPSCR 64
+ PPC KVM_REG_PPC_VSCR 32
+ PPC KVM_REG_PPC_VPA_ADDR 64
+ PPC KVM_REG_PPC_VPA_SLB 128
+ PPC KVM_REG_PPC_VPA_DTL 128
+ PPC KVM_REG_PPC_EPCR 32
+ PPC KVM_REG_PPC_EPR 32
+ PPC KVM_REG_PPC_TCR 32
+ PPC KVM_REG_PPC_TSR 32
+ PPC KVM_REG_PPC_OR_TSR 32
+ PPC KVM_REG_PPC_CLEAR_TSR 32
+ PPC KVM_REG_PPC_MAS0 32
+ PPC KVM_REG_PPC_MAS1 32
+ PPC KVM_REG_PPC_MAS2 64
+ PPC KVM_REG_PPC_MAS7_3 64
+ PPC KVM_REG_PPC_MAS4 32
+ PPC KVM_REG_PPC_MAS6 32
+ PPC KVM_REG_PPC_MMUCFG 32
+ PPC KVM_REG_PPC_TLB0CFG 32
+ PPC KVM_REG_PPC_TLB1CFG 32
+ PPC KVM_REG_PPC_TLB2CFG 32
+ PPC KVM_REG_PPC_TLB3CFG 32
+ PPC KVM_REG_PPC_TLB0PS 32
+ PPC KVM_REG_PPC_TLB1PS 32
+ PPC KVM_REG_PPC_TLB2PS 32
+ PPC KVM_REG_PPC_TLB3PS 32
+ PPC KVM_REG_PPC_EPTCFG 32
+ PPC KVM_REG_PPC_ICP_STATE 64
+ PPC KVM_REG_PPC_VP_STATE 128
+ PPC KVM_REG_PPC_TB_OFFSET 64
+ PPC KVM_REG_PPC_SPMC1 32
+ PPC KVM_REG_PPC_SPMC2 32
+ PPC KVM_REG_PPC_IAMR 64
+ PPC KVM_REG_PPC_TFHAR 64
+ PPC KVM_REG_PPC_TFIAR 64
+ PPC KVM_REG_PPC_TEXASR 64
+ PPC KVM_REG_PPC_FSCR 64
+ PPC KVM_REG_PPC_PSPB 32
+ PPC KVM_REG_PPC_EBBHR 64
+ PPC KVM_REG_PPC_EBBRR 64
+ PPC KVM_REG_PPC_BESCR 64
+ PPC KVM_REG_PPC_TAR 64
+ PPC KVM_REG_PPC_DPDES 64
+ PPC KVM_REG_PPC_DAWR 64
+ PPC KVM_REG_PPC_DAWRX 64
+ PPC KVM_REG_PPC_CIABR 64
+ PPC KVM_REG_PPC_IC 64
+ PPC KVM_REG_PPC_VTB 64
+ PPC KVM_REG_PPC_CSIGR 64
+ PPC KVM_REG_PPC_TACR 64
+ PPC KVM_REG_PPC_TCSCR 64
+ PPC KVM_REG_PPC_PID 64
+ PPC KVM_REG_PPC_ACOP 64
+ PPC KVM_REG_PPC_VRSAVE 32
+ PPC KVM_REG_PPC_LPCR 32
+ PPC KVM_REG_PPC_LPCR_64 64
+ PPC KVM_REG_PPC_PPR 64
+ PPC KVM_REG_PPC_ARCH_COMPAT 32
+ PPC KVM_REG_PPC_DABRX 32
+ PPC KVM_REG_PPC_WORT 64
+ PPC KVM_REG_PPC_SPRG9 64
+ PPC KVM_REG_PPC_DBSR 32
+ PPC KVM_REG_PPC_TIDR 64
+ PPC KVM_REG_PPC_PSSCR 64
+ PPC KVM_REG_PPC_DEC_EXPIRY 64
+ PPC KVM_REG_PPC_PTCR 64
+ PPC KVM_REG_PPC_TM_GPR0 64
+ ...
+ PPC KVM_REG_PPC_TM_GPR31 64
+ PPC KVM_REG_PPC_TM_VSR0 128
+ ...
+ PPC KVM_REG_PPC_TM_VSR63 128
+ PPC KVM_REG_PPC_TM_CR 64
+ PPC KVM_REG_PPC_TM_LR 64
+ PPC KVM_REG_PPC_TM_CTR 64
+ PPC KVM_REG_PPC_TM_FPSCR 64
+ PPC KVM_REG_PPC_TM_AMR 64
+ PPC KVM_REG_PPC_TM_PPR 64
+ PPC KVM_REG_PPC_TM_VRSAVE 64
+ PPC KVM_REG_PPC_TM_VSCR 32
+ PPC KVM_REG_PPC_TM_DSCR 64
+ PPC KVM_REG_PPC_TM_TAR 64
+ PPC KVM_REG_PPC_TM_XER 64
+
+ MIPS KVM_REG_MIPS_R0 64
+ ...
+ MIPS KVM_REG_MIPS_R31 64
+ MIPS KVM_REG_MIPS_HI 64
+ MIPS KVM_REG_MIPS_LO 64
+ MIPS KVM_REG_MIPS_PC 64
+ MIPS KVM_REG_MIPS_CP0_INDEX 32
+ MIPS KVM_REG_MIPS_CP0_ENTRYLO0 64
+ MIPS KVM_REG_MIPS_CP0_ENTRYLO1 64
+ MIPS KVM_REG_MIPS_CP0_CONTEXT 64
+ MIPS KVM_REG_MIPS_CP0_CONTEXTCONFIG 32
+ MIPS KVM_REG_MIPS_CP0_USERLOCAL 64
+ MIPS KVM_REG_MIPS_CP0_XCONTEXTCONFIG 64
+ MIPS KVM_REG_MIPS_CP0_PAGEMASK 32
+ MIPS KVM_REG_MIPS_CP0_PAGEGRAIN 32
+ MIPS KVM_REG_MIPS_CP0_SEGCTL0 64
+ MIPS KVM_REG_MIPS_CP0_SEGCTL1 64
+ MIPS KVM_REG_MIPS_CP0_SEGCTL2 64
+ MIPS KVM_REG_MIPS_CP0_PWBASE 64
+ MIPS KVM_REG_MIPS_CP0_PWFIELD 64
+ MIPS KVM_REG_MIPS_CP0_PWSIZE 64
+ MIPS KVM_REG_MIPS_CP0_WIRED 32
+ MIPS KVM_REG_MIPS_CP0_PWCTL 32
+ MIPS KVM_REG_MIPS_CP0_HWRENA 32
+ MIPS KVM_REG_MIPS_CP0_BADVADDR 64
+ MIPS KVM_REG_MIPS_CP0_BADINSTR 32
+ MIPS KVM_REG_MIPS_CP0_BADINSTRP 32
+ MIPS KVM_REG_MIPS_CP0_COUNT 32
+ MIPS KVM_REG_MIPS_CP0_ENTRYHI 64
+ MIPS KVM_REG_MIPS_CP0_COMPARE 32
+ MIPS KVM_REG_MIPS_CP0_STATUS 32
+ MIPS KVM_REG_MIPS_CP0_INTCTL 32
+ MIPS KVM_REG_MIPS_CP0_CAUSE 32
+ MIPS KVM_REG_MIPS_CP0_EPC 64
+ MIPS KVM_REG_MIPS_CP0_PRID 32
+ MIPS KVM_REG_MIPS_CP0_EBASE 64
+ MIPS KVM_REG_MIPS_CP0_CONFIG 32
+ MIPS KVM_REG_MIPS_CP0_CONFIG1 32
+ MIPS KVM_REG_MIPS_CP0_CONFIG2 32
+ MIPS KVM_REG_MIPS_CP0_CONFIG3 32
+ MIPS KVM_REG_MIPS_CP0_CONFIG4 32
+ MIPS KVM_REG_MIPS_CP0_CONFIG5 32
+ MIPS KVM_REG_MIPS_CP0_CONFIG7 32
+ MIPS KVM_REG_MIPS_CP0_XCONTEXT 64
+ MIPS KVM_REG_MIPS_CP0_ERROREPC 64
+ MIPS KVM_REG_MIPS_CP0_KSCRATCH1 64
+ MIPS KVM_REG_MIPS_CP0_KSCRATCH2 64
+ MIPS KVM_REG_MIPS_CP0_KSCRATCH3 64
+ MIPS KVM_REG_MIPS_CP0_KSCRATCH4 64
+ MIPS KVM_REG_MIPS_CP0_KSCRATCH5 64
+ MIPS KVM_REG_MIPS_CP0_KSCRATCH6 64
+ MIPS KVM_REG_MIPS_CP0_MAAR(0..63) 64
+ MIPS KVM_REG_MIPS_COUNT_CTL 64
+ MIPS KVM_REG_MIPS_COUNT_RESUME 64
+ MIPS KVM_REG_MIPS_COUNT_HZ 64
+ MIPS KVM_REG_MIPS_FPR_32(0..31) 32
+ MIPS KVM_REG_MIPS_FPR_64(0..31) 64
+ MIPS KVM_REG_MIPS_VEC_128(0..31) 128
+ MIPS KVM_REG_MIPS_FCR_IR 32
+ MIPS KVM_REG_MIPS_FCR_CSR 32
+ MIPS KVM_REG_MIPS_MSA_IR 32
+ MIPS KVM_REG_MIPS_MSA_CSR 32
+ ======= =============================== ============
ARM registers are mapped using the lower 32 bits. The upper 16 of that
is the register group type, or coprocessor number:
-ARM core registers have the following id bit patterns:
+ARM core registers have the following id bit patterns::
+
0x4020 0000 0010 <index into the kvm_regs struct:16>
-ARM 32-bit CP15 registers have the following id bit patterns:
+ARM 32-bit CP15 registers have the following id bit patterns::
+
0x4020 0000 000F <zero:1> <crn:4> <crm:4> <opc1:4> <opc2:3>
-ARM 64-bit CP15 registers have the following id bit patterns:
+ARM 64-bit CP15 registers have the following id bit patterns::
+
0x4030 0000 000F <zero:1> <zero:4> <crm:4> <opc1:4> <zero:3>
-ARM CCSIDR registers are demultiplexed by CSSELR value:
+ARM CCSIDR registers are demultiplexed by CSSELR value::
+
0x4020 0000 0011 00 <csselr:8>
-ARM 32-bit VFP control registers have the following id bit patterns:
+ARM 32-bit VFP control registers have the following id bit patterns::
+
0x4020 0000 0012 1 <regno:12>
-ARM 64-bit FP registers have the following id bit patterns:
+ARM 64-bit FP registers have the following id bit patterns::
+
0x4030 0000 0012 0 <regno:12>
-ARM firmware pseudo-registers have the following bit pattern:
+ARM firmware pseudo-registers have the following bit pattern::
+
0x4030 0000 0014 <regno:16>
@@ -2142,15 +2375,18 @@
arm64 core/FP-SIMD registers have the following id bit patterns. Note
that the size of the access is variable, as the kvm_regs structure
contains elements ranging from 32 to 128 bits. The index is a 32bit
-value in the kvm_regs structure seen as a 32bit array.
+value in the kvm_regs structure seen as a 32bit array::
+
0x60x0 0000 0010 <index into the kvm_regs struct:16>
Specifically:
+
+======================= ========= ===== =======================================
Encoding Register Bits kvm_regs member
-----------------------------------------------------------------
+======================= ========= ===== =======================================
0x6030 0000 0010 0000 X0 64 regs.regs[0]
0x6030 0000 0010 0002 X1 64 regs.regs[1]
- ...
+ ...
0x6030 0000 0010 003c X30 64 regs.regs[30]
0x6030 0000 0010 003e SP 64 regs.sp
0x6030 0000 0010 0040 PC 64 regs.pc
@@ -2162,30 +2398,45 @@
0x6030 0000 0010 004c SPSR_UND 64 spsr[KVM_SPSR_UND]
0x6030 0000 0010 004e SPSR_IRQ 64 spsr[KVM_SPSR_IRQ]
0x6060 0000 0010 0050 SPSR_FIQ 64 spsr[KVM_SPSR_FIQ]
- 0x6040 0000 0010 0054 V0 128 fp_regs.vregs[0] (*)
- 0x6040 0000 0010 0058 V1 128 fp_regs.vregs[1] (*)
- ...
- 0x6040 0000 0010 00d0 V31 128 fp_regs.vregs[31] (*)
+ 0x6040 0000 0010 0054 V0 128 fp_regs.vregs[0] [1]_
+ 0x6040 0000 0010 0058 V1 128 fp_regs.vregs[1] [1]_
+ ...
+ 0x6040 0000 0010 00d0 V31 128 fp_regs.vregs[31] [1]_
0x6020 0000 0010 00d4 FPSR 32 fp_regs.fpsr
0x6020 0000 0010 00d5 FPCR 32 fp_regs.fpcr
+======================= ========= ===== =======================================
-(*) These encodings are not accepted for SVE-enabled vcpus. See
- KVM_ARM_VCPU_INIT.
+.. [1] These encodings are not accepted for SVE-enabled vcpus. See
+ KVM_ARM_VCPU_INIT.
- The equivalent register content can be accessed via bits [127:0] of
- the corresponding SVE Zn registers instead for vcpus that have SVE
- enabled (see below).
+ The equivalent register content can be accessed via bits [127:0] of
+ the corresponding SVE Zn registers instead for vcpus that have SVE
+ enabled (see below).
-arm64 CCSIDR registers are demultiplexed by CSSELR value:
+arm64 CCSIDR registers are demultiplexed by CSSELR value::
+
0x6020 0000 0011 00 <csselr:8>
-arm64 system registers have the following id bit patterns:
+arm64 system registers have the following id bit patterns::
+
0x6030 0000 0013 <op0:2> <op1:3> <crn:4> <crm:4> <op2:3>
-arm64 firmware pseudo-registers have the following bit pattern:
+.. warning::
+
+ Two system register IDs do not follow the specified pattern. These
+ are KVM_REG_ARM_TIMER_CVAL and KVM_REG_ARM_TIMER_CNT, which map to
+ system registers CNTV_CVAL_EL0 and CNTVCT_EL0 respectively. These
+ two had their values accidentally swapped, which means TIMER_CVAL is
+ derived from the register encoding for CNTVCT_EL0 and TIMER_CNT is
+ derived from the register encoding for CNTV_CVAL_EL0. As this is
+ API, it must remain this way.
+
+arm64 firmware pseudo-registers have the following bit pattern::
+
0x6030 0000 0014 <regno:16>
-arm64 SVE registers have the following bit patterns:
+arm64 SVE registers have the following bit patterns::
+
0x6080 0000 0015 00 <n:5> <slice:5> Zn bits[2048*slice + 2047 : 2048*slice]
0x6050 0000 0015 04 <n:4> <slice:5> Pn bits[256*slice + 255 : 256*slice]
0x6050 0000 0015 060 <slice:5> FFR bits[256*slice + 255 : 256*slice]
@@ -2193,7 +2444,7 @@
Access to register IDs where 2048 * slice >= 128 * max_vq will fail with
ENOENT. max_vq is the vcpu's maximum supported vector length in 128-bit
-quadwords: see (**) below.
+quadwords: see [2]_ below.
These registers are only accessible on vcpus for which SVE is enabled.
See KVM_ARM_VCPU_INIT for details.
@@ -2208,21 +2459,21 @@
userspace. When transferred to or from user memory via KVM_GET_ONE_REG
or KVM_SET_ONE_REG, the value of this register is of type
__u64[KVM_ARM64_SVE_VLS_WORDS], and encodes the set of vector lengths as
-follows:
+follows::
-__u64 vector_lengths[KVM_ARM64_SVE_VLS_WORDS];
+ __u64 vector_lengths[KVM_ARM64_SVE_VLS_WORDS];
-if (vq >= SVE_VQ_MIN && vq <= SVE_VQ_MAX &&
- ((vector_lengths[(vq - KVM_ARM64_SVE_VQ_MIN) / 64] >>
+ if (vq >= SVE_VQ_MIN && vq <= SVE_VQ_MAX &&
+ ((vector_lengths[(vq - KVM_ARM64_SVE_VQ_MIN) / 64] >>
((vq - KVM_ARM64_SVE_VQ_MIN) % 64)) & 1))
/* Vector length vq * 16 bytes supported */
-else
+ else
/* Vector length vq * 16 bytes not supported */
-(**) The maximum value vq for which the above condition is true is
-max_vq. This is the maximum vector length available to the guest on
-this vcpu, and determines which register slices are visible through
-this ioctl interface.
+.. [2] The maximum value vq for which the above condition is true is
+ max_vq. This is the maximum vector length available to the guest on
+ this vcpu, and determines which register slices are visible through
+ this ioctl interface.
(See Documentation/arm64/sve.rst for an explanation of the "vq"
nomenclature.)
@@ -2247,11 +2498,13 @@
MIPS registers are mapped using the lower 32 bits. The upper 16 of that is
the register group type:
-MIPS core registers (see above) have the following id bit patterns:
+MIPS core registers (see above) have the following id bit patterns::
+
0x7030 0000 0000 <reg:16>
MIPS CP0 registers (see KVM_REG_MIPS_CP0_* above) have the following id bit
-patterns depending on whether they're 32-bit or 64-bit registers:
+patterns depending on whether they're 32-bit or 64-bit registers::
+
0x7020 0000 0001 00 <reg:5> <sel:3> (32-bit)
0x7030 0000 0001 00 <reg:5> <sel:3> (64-bit)
@@ -2262,10 +2515,12 @@
the PFNX field starting at bit 30.
MIPS MAARs (see KVM_REG_MIPS_CP0_MAAR(*) above) have the following id bit
-patterns:
+patterns::
+
0x7030 0000 0001 01 <reg:8>
-MIPS KVM control registers (see above) have the following id bit patterns:
+MIPS KVM control registers (see above) have the following id bit patterns::
+
0x7030 0000 0002 <reg:16>
MIPS FPU registers (see KVM_REG_MIPS_FPR_{32,64}() above) have the following
@@ -2274,31 +2529,41 @@
Config5.FRE), i.e. as the guest would see them, and they become unpredictable
if the guest FPU mode is changed. MIPS SIMD Architecture (MSA) vector
registers (see KVM_REG_MIPS_VEC_128() above) have similar patterns as they
-overlap the FPU registers:
+overlap the FPU registers::
+
0x7020 0000 0003 00 <0:3> <reg:5> (32-bit FPU registers)
0x7030 0000 0003 00 <0:3> <reg:5> (64-bit FPU registers)
0x7040 0000 0003 00 <0:3> <reg:5> (128-bit MSA vector registers)
MIPS FPU control registers (see KVM_REG_MIPS_FCR_{IR,CSR} above) have the
-following id bit patterns:
+following id bit patterns::
+
0x7020 0000 0003 01 <0:3> <reg:5>
MIPS MSA control registers (see KVM_REG_MIPS_MSA_{IR,CSR} above) have the
-following id bit patterns:
+following id bit patterns::
+
0x7020 0000 0003 02 <0:3> <reg:5>
4.69 KVM_GET_ONE_REG
+--------------------
-Capability: KVM_CAP_ONE_REG
-Architectures: all
-Type: vcpu ioctl
-Parameters: struct kvm_one_reg (in and out)
-Returns: 0 on success, negative value on failure
+:Capability: KVM_CAP_ONE_REG
+:Architectures: all
+:Type: vcpu ioctl
+:Parameters: struct kvm_one_reg (in and out)
+:Returns: 0 on success, negative value on failure
+
Errors include:
- ENOENT: no such register
- EINVAL: invalid register ID, or no such register
- EPERM: (arm64) register access not allowed before vcpu finalization
+
+ ======== ============================================================
+ ENOENT no such register
+ EINVAL invalid register ID, or no such register or used with VMs in
+ protected virtualization mode on s390
+ EPERM (arm64) register access not allowed before vcpu finalization
+ ======== ============================================================
+
(These error codes are indicative only: do not rely on a specific error
code being returned in a specific situation.)
@@ -2312,20 +2577,23 @@
4.70 KVM_KVMCLOCK_CTRL
+----------------------
-Capability: KVM_CAP_KVMCLOCK_CTRL
-Architectures: Any that implement pvclocks (currently x86 only)
-Type: vcpu ioctl
-Parameters: None
-Returns: 0 on success, -1 on error
+:Capability: KVM_CAP_KVMCLOCK_CTRL
+:Architectures: Any that implement pvclocks (currently x86 only)
+:Type: vcpu ioctl
+:Parameters: None
+:Returns: 0 on success, -1 on error
-This signals to the host kernel that the specified guest is being paused by
-userspace. The host will set a flag in the pvclock structure that is checked
-from the soft lockup watchdog. The flag is part of the pvclock structure that
-is shared between guest and host, specifically the second bit of the flags
+This ioctl sets a flag accessible to the guest indicating that the specified
+vCPU has been paused by the host userspace.
+
+The host will set a flag in the pvclock structure that is checked from the
+soft lockup watchdog. The flag is part of the pvclock structure that is
+shared between guest and host, specifically the second bit of the flags
field of the pvclock_vcpu_time_info structure. It will be set exclusively by
the host and read/cleared exclusively by the guest. The guest operation of
-checking and clearing the flag must an atomic operation so
+checking and clearing the flag must be an atomic operation so
load-link/store-conditional, or equivalent must be used. There are two cases
where the guest will clear the flag: when the soft lockup watchdog timer resets
itself or when a soft lockup is detected. This ioctl can be called any time
@@ -2333,26 +2601,30 @@
4.71 KVM_SIGNAL_MSI
+-------------------
-Capability: KVM_CAP_SIGNAL_MSI
-Architectures: x86 arm arm64
-Type: vm ioctl
-Parameters: struct kvm_msi (in)
-Returns: >0 on delivery, 0 if guest blocked the MSI, and -1 on error
+:Capability: KVM_CAP_SIGNAL_MSI
+:Architectures: x86 arm arm64
+:Type: vm ioctl
+:Parameters: struct kvm_msi (in)
+:Returns: >0 on delivery, 0 if guest blocked the MSI, and -1 on error
Directly inject a MSI message. Only valid with in-kernel irqchip that handles
MSI messages.
-struct kvm_msi {
+::
+
+ struct kvm_msi {
__u32 address_lo;
__u32 address_hi;
__u32 data;
__u32 flags;
__u32 devid;
__u8 pad[12];
-};
+ };
-flags: KVM_MSI_VALID_DEVID: devid contains a valid value. The per-VM
+flags:
+ KVM_MSI_VALID_DEVID: devid contains a valid value. The per-VM
KVM_CAP_MSI_DEVID capability advertises the requirement to provide
the device ID. If this capability is not available, userspace
should never set the KVM_MSI_VALID_DEVID flag as the ioctl might fail.
@@ -2368,30 +2640,31 @@
4.71 KVM_CREATE_PIT2
+--------------------
-Capability: KVM_CAP_PIT2
-Architectures: x86
-Type: vm ioctl
-Parameters: struct kvm_pit_config (in)
-Returns: 0 on success, -1 on error
+:Capability: KVM_CAP_PIT2
+:Architectures: x86
+:Type: vm ioctl
+:Parameters: struct kvm_pit_config (in)
+:Returns: 0 on success, -1 on error
Creates an in-kernel device model for the i8254 PIT. This call is only valid
after enabling in-kernel irqchip support via KVM_CREATE_IRQCHIP. The following
-parameters have to be passed:
+parameters have to be passed::
-struct kvm_pit_config {
+ struct kvm_pit_config {
__u32 flags;
__u32 pad[15];
-};
+ };
-Valid flags are:
+Valid flags are::
-#define KVM_PIT_SPEAKER_DUMMY 1 /* emulate speaker port stub */
+ #define KVM_PIT_SPEAKER_DUMMY 1 /* emulate speaker port stub */
PIT timer interrupts may use a per-VM kernel thread for injection. If it
-exists, this thread will have a name of the following pattern:
+exists, this thread will have a name of the following pattern::
-kvm-pit/<owner-process-pid>
+ kvm-pit/<owner-process-pid>
When running a guest with elevated priorities, the scheduling parameters of
this thread may have to be adjusted accordingly.
@@ -2400,37 +2673,39 @@
4.72 KVM_GET_PIT2
+-----------------
-Capability: KVM_CAP_PIT_STATE2
-Architectures: x86
-Type: vm ioctl
-Parameters: struct kvm_pit_state2 (out)
-Returns: 0 on success, -1 on error
+:Capability: KVM_CAP_PIT_STATE2
+:Architectures: x86
+:Type: vm ioctl
+:Parameters: struct kvm_pit_state2 (out)
+:Returns: 0 on success, -1 on error
Retrieves the state of the in-kernel PIT model. Only valid after
-KVM_CREATE_PIT2. The state is returned in the following structure:
+KVM_CREATE_PIT2. The state is returned in the following structure::
-struct kvm_pit_state2 {
+ struct kvm_pit_state2 {
struct kvm_pit_channel_state channels[3];
__u32 flags;
__u32 reserved[9];
-};
+ };
-Valid flags are:
+Valid flags are::
-/* disable PIT in HPET legacy mode */
-#define KVM_PIT_FLAGS_HPET_LEGACY 0x00000001
+ /* disable PIT in HPET legacy mode */
+ #define KVM_PIT_FLAGS_HPET_LEGACY 0x00000001
This IOCTL replaces the obsolete KVM_GET_PIT.
4.73 KVM_SET_PIT2
+-----------------
-Capability: KVM_CAP_PIT_STATE2
-Architectures: x86
-Type: vm ioctl
-Parameters: struct kvm_pit_state2 (in)
-Returns: 0 on success, -1 on error
+:Capability: KVM_CAP_PIT_STATE2
+:Architectures: x86
+:Type: vm ioctl
+:Parameters: struct kvm_pit_state2 (in)
+:Returns: 0 on success, -1 on error
Sets the state of the in-kernel PIT model. Only valid after KVM_CREATE_PIT2.
See KVM_GET_PIT2 for details on struct kvm_pit_state2.
@@ -2439,12 +2714,13 @@
4.74 KVM_PPC_GET_SMMU_INFO
+--------------------------
-Capability: KVM_CAP_PPC_GET_SMMU_INFO
-Architectures: powerpc
-Type: vm ioctl
-Parameters: None
-Returns: 0 on success, -1 on error
+:Capability: KVM_CAP_PPC_GET_SMMU_INFO
+:Architectures: powerpc
+:Type: vm ioctl
+:Parameters: None
+:Returns: 0 on success, -1 on error
This populates and returns a structure describing the features of
the "Server" class MMU emulation supported by KVM.
@@ -2452,7 +2728,7 @@
device-tree properties for the guest operating system.
The structure contains some global information, followed by an
-array of supported segment page sizes:
+array of supported segment page sizes::
struct kvm_ppc_smmu_info {
__u64 flags;
@@ -2480,7 +2756,7 @@
The "sps" array contains 8 entries indicating the supported base
page sizes for a segment in increasing order. Each entry is defined
-as follow:
+as follow::
struct kvm_ppc_one_seg_page_size {
__u32 page_shift; /* Base page shift of segment (or 0) */
@@ -2501,7 +2777,7 @@
only larger or equal to the base page size), along with the
corresponding encoding in the hash PTE. Similarly, the array is
8 entries sorted by increasing sizes and an entry with a "0" shift
-is an empty entry and a terminator:
+is an empty entry and a terminator::
struct kvm_ppc_one_page_size {
__u32 page_shift; /* Page shift (or 0) */
@@ -2513,12 +2789,13 @@
into the hash PTE second double word).
4.75 KVM_IRQFD
+--------------
-Capability: KVM_CAP_IRQFD
-Architectures: x86 s390 arm arm64
-Type: vm ioctl
-Parameters: struct kvm_irqfd (in)
-Returns: 0 on success, -1 on error
+:Capability: KVM_CAP_IRQFD
+:Architectures: x86 s390 arm arm64
+:Type: vm ioctl
+:Parameters: struct kvm_irqfd (in)
+:Returns: 0 on success, -1 on error
Allows setting an eventfd to directly trigger a guest interrupt.
kvm_irqfd.fd specifies the file descriptor to use as the eventfd and
@@ -2542,6 +2819,7 @@
and need not be specified with KVM_IRQFD_FLAG_DEASSIGN.
On arm/arm64, gsi routing being supported, the following can happen:
+
- in case no routing entry is associated to this gsi, injection fails
- in case the gsi is associated to an irqchip routing entry,
irqchip.pin + 32 corresponds to the injected SPI ID.
@@ -2550,12 +2828,13 @@
to GICv3 ITS in-kernel emulation).
4.76 KVM_PPC_ALLOCATE_HTAB
+--------------------------
-Capability: KVM_CAP_PPC_ALLOC_HTAB
-Architectures: powerpc
-Type: vm ioctl
-Parameters: Pointer to u32 containing hash table order (in/out)
-Returns: 0 on success, -1 on error
+:Capability: KVM_CAP_PPC_ALLOC_HTAB
+:Architectures: powerpc
+:Type: vm ioctl
+:Parameters: Pointer to u32 containing hash table order (in/out)
+:Returns: 0 on success, -1 on error
This requests the host kernel to allocate an MMU hash table for a
guest using the PAPR paravirtualization interface. This only does
@@ -2586,75 +2865,88 @@
HPTEs on the next KVM_RUN of any vcpu.
4.77 KVM_S390_INTERRUPT
+-----------------------
-Capability: basic
-Architectures: s390
-Type: vm ioctl, vcpu ioctl
-Parameters: struct kvm_s390_interrupt (in)
-Returns: 0 on success, -1 on error
+:Capability: basic
+:Architectures: s390
+:Type: vm ioctl, vcpu ioctl
+:Parameters: struct kvm_s390_interrupt (in)
+:Returns: 0 on success, -1 on error
Allows to inject an interrupt to the guest. Interrupts can be floating
(vm ioctl) or per cpu (vcpu ioctl), depending on the interrupt type.
-Interrupt parameters are passed via kvm_s390_interrupt:
+Interrupt parameters are passed via kvm_s390_interrupt::
-struct kvm_s390_interrupt {
+ struct kvm_s390_interrupt {
__u32 type;
__u32 parm;
__u64 parm64;
-};
+ };
type can be one of the following:
-KVM_S390_SIGP_STOP (vcpu) - sigp stop; optional flags in parm
-KVM_S390_PROGRAM_INT (vcpu) - program check; code in parm
-KVM_S390_SIGP_SET_PREFIX (vcpu) - sigp set prefix; prefix address in parm
-KVM_S390_RESTART (vcpu) - restart
-KVM_S390_INT_CLOCK_COMP (vcpu) - clock comparator interrupt
-KVM_S390_INT_CPU_TIMER (vcpu) - CPU timer interrupt
-KVM_S390_INT_VIRTIO (vm) - virtio external interrupt; external interrupt
- parameters in parm and parm64
-KVM_S390_INT_SERVICE (vm) - sclp external interrupt; sclp parameter in parm
-KVM_S390_INT_EMERGENCY (vcpu) - sigp emergency; source cpu in parm
-KVM_S390_INT_EXTERNAL_CALL (vcpu) - sigp external call; source cpu in parm
-KVM_S390_INT_IO(ai,cssid,ssid,schid) (vm) - compound value to indicate an
- I/O interrupt (ai - adapter interrupt; cssid,ssid,schid - subchannel);
- I/O interruption parameters in parm (subchannel) and parm64 (intparm,
- interruption subclass)
-KVM_S390_MCHK (vm, vcpu) - machine check interrupt; cr 14 bits in parm,
- machine check interrupt code in parm64 (note that
- machine checks needing further payload are not
- supported by this ioctl)
+KVM_S390_SIGP_STOP (vcpu)
+ - sigp stop; optional flags in parm
+KVM_S390_PROGRAM_INT (vcpu)
+ - program check; code in parm
+KVM_S390_SIGP_SET_PREFIX (vcpu)
+ - sigp set prefix; prefix address in parm
+KVM_S390_RESTART (vcpu)
+ - restart
+KVM_S390_INT_CLOCK_COMP (vcpu)
+ - clock comparator interrupt
+KVM_S390_INT_CPU_TIMER (vcpu)
+ - CPU timer interrupt
+KVM_S390_INT_VIRTIO (vm)
+ - virtio external interrupt; external interrupt
+ parameters in parm and parm64
+KVM_S390_INT_SERVICE (vm)
+ - sclp external interrupt; sclp parameter in parm
+KVM_S390_INT_EMERGENCY (vcpu)
+ - sigp emergency; source cpu in parm
+KVM_S390_INT_EXTERNAL_CALL (vcpu)
+ - sigp external call; source cpu in parm
+KVM_S390_INT_IO(ai,cssid,ssid,schid) (vm)
+ - compound value to indicate an
+ I/O interrupt (ai - adapter interrupt; cssid,ssid,schid - subchannel);
+ I/O interruption parameters in parm (subchannel) and parm64 (intparm,
+ interruption subclass)
+KVM_S390_MCHK (vm, vcpu)
+ - machine check interrupt; cr 14 bits in parm, machine check interrupt
+ code in parm64 (note that machine checks needing further payload are not
+ supported by this ioctl)
This is an asynchronous vcpu ioctl and can be invoked from any thread.
4.78 KVM_PPC_GET_HTAB_FD
+------------------------
-Capability: KVM_CAP_PPC_HTAB_FD
-Architectures: powerpc
-Type: vm ioctl
-Parameters: Pointer to struct kvm_get_htab_fd (in)
-Returns: file descriptor number (>= 0) on success, -1 on error
+:Capability: KVM_CAP_PPC_HTAB_FD
+:Architectures: powerpc
+:Type: vm ioctl
+:Parameters: Pointer to struct kvm_get_htab_fd (in)
+:Returns: file descriptor number (>= 0) on success, -1 on error
This returns a file descriptor that can be used either to read out the
entries in the guest's hashed page table (HPT), or to write entries to
initialize the HPT. The returned fd can only be written to if the
KVM_GET_HTAB_WRITE bit is set in the flags field of the argument, and
can only be read if that bit is clear. The argument struct looks like
-this:
+this::
-/* For KVM_PPC_GET_HTAB_FD */
-struct kvm_get_htab_fd {
+ /* For KVM_PPC_GET_HTAB_FD */
+ struct kvm_get_htab_fd {
__u64 flags;
__u64 start_index;
__u64 reserved[2];
-};
+ };
-/* Values for kvm_get_htab_fd.flags */
-#define KVM_GET_HTAB_BOLTED_ONLY ((__u64)0x1)
-#define KVM_GET_HTAB_WRITE ((__u64)0x2)
+ /* Values for kvm_get_htab_fd.flags */
+ #define KVM_GET_HTAB_BOLTED_ONLY ((__u64)0x1)
+ #define KVM_GET_HTAB_WRITE ((__u64)0x2)
-The `start_index' field gives the index in the HPT of the entry at
+The 'start_index' field gives the index in the HPT of the entry at
which to start reading. It is ignored when writing.
Reads on the fd will initially supply information about all
@@ -2669,29 +2961,34 @@
series of valid HPT entries (16 bytes) each. The header indicates how
many valid HPT entries there are and how many invalid entries follow
the valid entries. The invalid entries are not represented explicitly
-in the stream. The header format is:
+in the stream. The header format is::
-struct kvm_get_htab_header {
+ struct kvm_get_htab_header {
__u32 index;
__u16 n_valid;
__u16 n_invalid;
-};
+ };
Writes to the fd create HPT entries starting at the index given in the
-header; first `n_valid' valid entries with contents from the data
-written, then `n_invalid' invalid entries, invalidating any previously
+header; first 'n_valid' valid entries with contents from the data
+written, then 'n_invalid' invalid entries, invalidating any previously
valid entries found.
4.79 KVM_CREATE_DEVICE
+----------------------
-Capability: KVM_CAP_DEVICE_CTRL
-Type: vm ioctl
-Parameters: struct kvm_create_device (in/out)
-Returns: 0 on success, -1 on error
+:Capability: KVM_CAP_DEVICE_CTRL
+:Type: vm ioctl
+:Parameters: struct kvm_create_device (in/out)
+:Returns: 0 on success, -1 on error
+
Errors:
- ENODEV: The device type is unknown or unsupported
- EEXIST: Device already created, and this type of device may not
+
+ ====== =======================================================
+ ENODEV The device type is unknown or unsupported
+ EEXIST Device already created, and this type of device may not
be instantiated multiple times
+ ====== =======================================================
Other error conditions may be defined by individual device types or
have their standard meanings.
@@ -2707,25 +3004,32 @@
for specifying any behavior that is not implied by the device type
number.
-struct kvm_create_device {
+::
+
+ struct kvm_create_device {
__u32 type; /* in: KVM_DEV_TYPE_xxx */
__u32 fd; /* out: device handle */
__u32 flags; /* in: KVM_CREATE_DEVICE_xxx */
-};
+ };
4.80 KVM_SET_DEVICE_ATTR/KVM_GET_DEVICE_ATTR
+--------------------------------------------
-Capability: KVM_CAP_DEVICE_CTRL, KVM_CAP_VM_ATTRIBUTES for vm device,
- KVM_CAP_VCPU_ATTRIBUTES for vcpu device
-Type: device ioctl, vm ioctl, vcpu ioctl
-Parameters: struct kvm_device_attr
-Returns: 0 on success, -1 on error
+:Capability: KVM_CAP_DEVICE_CTRL, KVM_CAP_VM_ATTRIBUTES for vm device,
+ KVM_CAP_VCPU_ATTRIBUTES for vcpu device
+:Type: device ioctl, vm ioctl, vcpu ioctl
+:Parameters: struct kvm_device_attr
+:Returns: 0 on success, -1 on error
+
Errors:
- ENXIO: The group or attribute is unknown/unsupported for this device
+
+ ===== =============================================================
+ ENXIO The group or attribute is unknown/unsupported for this device
or hardware support is missing.
- EPERM: The attribute cannot (currently) be accessed this way
+ EPERM The attribute cannot (currently) be accessed this way
(e.g. read-only attribute, or attribute that only makes
sense when the device is in a different state)
+ ===== =============================================================
Other error conditions may be defined by individual device types.
@@ -2734,23 +3038,30 @@
the "devices" directory. As with ONE_REG, the size of the data
transferred is defined by the particular attribute.
-struct kvm_device_attr {
+::
+
+ struct kvm_device_attr {
__u32 flags; /* no flags currently defined */
__u32 group; /* device-defined */
__u64 attr; /* group-defined */
__u64 addr; /* userspace address of attr data */
-};
+ };
4.81 KVM_HAS_DEVICE_ATTR
+------------------------
-Capability: KVM_CAP_DEVICE_CTRL, KVM_CAP_VM_ATTRIBUTES for vm device,
- KVM_CAP_VCPU_ATTRIBUTES for vcpu device
-Type: device ioctl, vm ioctl, vcpu ioctl
-Parameters: struct kvm_device_attr
-Returns: 0 on success, -1 on error
+:Capability: KVM_CAP_DEVICE_CTRL, KVM_CAP_VM_ATTRIBUTES for vm device,
+ KVM_CAP_VCPU_ATTRIBUTES for vcpu device
+:Type: device ioctl, vm ioctl, vcpu ioctl
+:Parameters: struct kvm_device_attr
+:Returns: 0 on success, -1 on error
+
Errors:
- ENXIO: The group or attribute is unknown/unsupported for this device
+
+ ===== =============================================================
+ ENXIO The group or attribute is unknown/unsupported for this device
or hardware support is missing.
+ ===== =============================================================
Tests whether a device supports a particular attribute. A successful
return indicates the attribute is implemented. It does not necessarily
@@ -2758,15 +3069,20 @@
current state. "addr" is ignored.
4.82 KVM_ARM_VCPU_INIT
+----------------------
-Capability: basic
-Architectures: arm, arm64
-Type: vcpu ioctl
-Parameters: struct kvm_vcpu_init (in)
-Returns: 0 on success; -1 on error
+:Capability: basic
+:Architectures: arm, arm64
+:Type: vcpu ioctl
+:Parameters: struct kvm_vcpu_init (in)
+:Returns: 0 on success; -1 on error
+
Errors:
- EINVAL: the target is unknown, or the combination of features is invalid.
- ENOENT: a features bit specified is unknown.
+
+ ====== =================================================================
+ EINVAL the target is unknown, or the combination of features is invalid.
+ ENOENT a features bit specified is unknown.
+ ====== =================================================================
This tells KVM what type of CPU to present to the guest, and what
optional features it should have. This will cause a reset of the cpu
@@ -2782,6 +3098,7 @@
target and same set of feature flags, otherwise EINVAL will be returned.
Possible features:
+
- KVM_ARM_VCPU_POWER_OFF: Starts the CPU in a power-off state.
Depends on KVM_CAP_ARM_PSCI. If not set, the CPU will be powered on
and execute guest code when KVM_RUN is called.
@@ -2838,14 +3155,19 @@
no longer be written using KVM_SET_ONE_REG.
4.83 KVM_ARM_PREFERRED_TARGET
+-----------------------------
-Capability: basic
-Architectures: arm, arm64
-Type: vm ioctl
-Parameters: struct struct kvm_vcpu_init (out)
-Returns: 0 on success; -1 on error
+:Capability: basic
+:Architectures: arm, arm64
+:Type: vm ioctl
+:Parameters: struct kvm_vcpu_init (out)
+:Returns: 0 on success; -1 on error
+
Errors:
- ENODEV: no preferred target available for the host
+
+ ====== ==========================================
+ ENODEV no preferred target available for the host
+ ====== ==========================================
This queries KVM for preferred CPU target type which can be emulated
by KVM on underlying host.
@@ -2858,47 +3180,61 @@
The information returned by this ioctl can be used to prepare an instance
of struct kvm_vcpu_init for KVM_ARM_VCPU_INIT ioctl which will result in
-in VCPU matching underlying host.
+VCPU matching underlying host.
4.84 KVM_GET_REG_LIST
+---------------------
-Capability: basic
-Architectures: arm, arm64, mips
-Type: vcpu ioctl
-Parameters: struct kvm_reg_list (in/out)
-Returns: 0 on success; -1 on error
+:Capability: basic
+:Architectures: arm, arm64, mips
+:Type: vcpu ioctl
+:Parameters: struct kvm_reg_list (in/out)
+:Returns: 0 on success; -1 on error
+
Errors:
- E2BIG: the reg index list is too big to fit in the array specified by
- the user (the number required will be written into n).
-struct kvm_reg_list {
+ ===== ==============================================================
+ E2BIG the reg index list is too big to fit in the array specified by
+ the user (the number required will be written into n).
+ ===== ==============================================================
+
+::
+
+ struct kvm_reg_list {
__u64 n; /* number of registers in reg[] */
__u64 reg[0];
-};
+ };
This ioctl returns the guest registers that are supported for the
KVM_GET_ONE_REG/KVM_SET_ONE_REG calls.
4.85 KVM_ARM_SET_DEVICE_ADDR (deprecated)
+-----------------------------------------
-Capability: KVM_CAP_ARM_SET_DEVICE_ADDR
-Architectures: arm, arm64
-Type: vm ioctl
-Parameters: struct kvm_arm_device_address (in)
-Returns: 0 on success, -1 on error
+:Capability: KVM_CAP_ARM_SET_DEVICE_ADDR
+:Architectures: arm, arm64
+:Type: vm ioctl
+:Parameters: struct kvm_arm_device_address (in)
+:Returns: 0 on success, -1 on error
+
Errors:
- ENODEV: The device id is unknown
- ENXIO: Device not supported on current system
- EEXIST: Address already set
- E2BIG: Address outside guest physical address space
- EBUSY: Address overlaps with other device range
-struct kvm_arm_device_addr {
+ ====== ============================================
+ ENODEV The device id is unknown
+ ENXIO Device not supported on current system
+ EEXIST Address already set
+ E2BIG Address outside guest physical address space
+ EBUSY Address overlaps with other device range
+ ====== ============================================
+
+::
+
+ struct kvm_arm_device_addr {
__u64 id;
__u64 addr;
-};
+ };
Specify a device address in the guest's physical address space where guests
can access emulated or directly exposed devices, which the host kernel needs
@@ -2906,7 +3242,7 @@
specific device.
ARM/arm64 divides the id field into two parts, a device id and an
-address type id specific to the individual device.
+address type id specific to the individual device::
bits: | 63 ... 32 | 31 ... 16 | 15 ... 0 |
field: | 0x00000000 | device id | addr type id |
@@ -2924,12 +3260,13 @@
4.86 KVM_PPC_RTAS_DEFINE_TOKEN
+------------------------------
-Capability: KVM_CAP_PPC_RTAS
-Architectures: ppc
-Type: vm ioctl
-Parameters: struct kvm_rtas_token_args
-Returns: 0 on success, -1 on error
+:Capability: KVM_CAP_PPC_RTAS
+:Architectures: ppc
+:Type: vm ioctl
+:Parameters: struct kvm_rtas_token_args
+:Returns: 0 on success, -1 on error
Defines a token value for a RTAS (Run Time Abstraction Services)
service in order to allow it to be handled in the kernel. The
@@ -2943,18 +3280,21 @@
handled.
4.87 KVM_SET_GUEST_DEBUG
+------------------------
-Capability: KVM_CAP_SET_GUEST_DEBUG
-Architectures: x86, s390, ppc, arm64
-Type: vcpu ioctl
-Parameters: struct kvm_guest_debug (in)
-Returns: 0 on success; -1 on error
+:Capability: KVM_CAP_SET_GUEST_DEBUG
+:Architectures: x86, s390, ppc, arm64
+:Type: vcpu ioctl
+:Parameters: struct kvm_guest_debug (in)
+:Returns: 0 on success; -1 on error
-struct kvm_guest_debug {
+::
+
+ struct kvm_guest_debug {
__u32 control;
__u32 pad;
struct kvm_guest_debug_arch arch;
-};
+ };
Set up the processor specific debug registers and configure vcpu for
handling guest debug events. There are two parts to the structure, the
@@ -2988,31 +3328,39 @@
KVM_CAP_GUEST_DEBUG_HW_WPS capabilities which return a positive number
indicating the number of supported registers.
+For ppc, the KVM_CAP_PPC_GUEST_DEBUG_SSTEP capability indicates whether
+the single-step debug event (KVM_GUESTDBG_SINGLESTEP) is supported.
+
When debug events exit the main run loop with the reason
KVM_EXIT_DEBUG with the kvm_debug_exit_arch part of the kvm_run
structure containing architecture specific debug information.
4.88 KVM_GET_EMULATED_CPUID
+---------------------------
-Capability: KVM_CAP_EXT_EMUL_CPUID
-Architectures: x86
-Type: system ioctl
-Parameters: struct kvm_cpuid2 (in/out)
-Returns: 0 on success, -1 on error
+:Capability: KVM_CAP_EXT_EMUL_CPUID
+:Architectures: x86
+:Type: system ioctl
+:Parameters: struct kvm_cpuid2 (in/out)
+:Returns: 0 on success, -1 on error
-struct kvm_cpuid2 {
+::
+
+ struct kvm_cpuid2 {
__u32 nent;
__u32 flags;
struct kvm_cpuid_entry2 entries[0];
-};
+ };
The member 'flags' is used for passing flags from userspace.
-#define KVM_CPUID_FLAG_SIGNIFCANT_INDEX BIT(0)
-#define KVM_CPUID_FLAG_STATEFUL_FUNC BIT(1)
-#define KVM_CPUID_FLAG_STATE_READ_NEXT BIT(2)
+::
-struct kvm_cpuid_entry2 {
+ #define KVM_CPUID_FLAG_SIGNIFCANT_INDEX BIT(0)
+ #define KVM_CPUID_FLAG_STATEFUL_FUNC BIT(1) /* deprecated */
+ #define KVM_CPUID_FLAG_STATE_READ_NEXT BIT(2) /* deprecated */
+
+ struct kvm_cpuid_entry2 {
__u32 function;
__u32 index;
__u32 flags;
@@ -3021,7 +3369,7 @@
__u32 ecx;
__u32 edx;
__u32 padding[3];
-};
+ };
This ioctl returns x86 cpuid features which are emulated by
kvm.Userspace can use the information returned by this ioctl to query
@@ -3046,37 +3394,38 @@
The fields in each entry are defined as follows:
- function: the eax value used to obtain the entry
- index: the ecx value used to obtain the entry (for entries that are
+ function:
+ the eax value used to obtain the entry
+ index:
+ the ecx value used to obtain the entry (for entries that are
affected by ecx)
- flags: an OR of zero or more of the following:
+ flags:
+ an OR of zero or more of the following:
+
KVM_CPUID_FLAG_SIGNIFCANT_INDEX:
if the index field is valid
- KVM_CPUID_FLAG_STATEFUL_FUNC:
- if cpuid for this function returns different values for successive
- invocations; there will be several entries with the same function,
- all with this flag set
- KVM_CPUID_FLAG_STATE_READ_NEXT:
- for KVM_CPUID_FLAG_STATEFUL_FUNC entries, set if this entry is
- the first entry to be read by a cpu
- eax, ebx, ecx, edx: the values returned by the cpuid instruction for
+
+ eax, ebx, ecx, edx:
+
+ the values returned by the cpuid instruction for
this function/index combination
4.89 KVM_S390_MEM_OP
+--------------------
-Capability: KVM_CAP_S390_MEM_OP
-Architectures: s390
-Type: vcpu ioctl
-Parameters: struct kvm_s390_mem_op (in)
-Returns: = 0 on success,
- < 0 on generic error (e.g. -EFAULT or -ENOMEM),
- > 0 if an exception occurred while walking the page tables
+:Capability: KVM_CAP_S390_MEM_OP
+:Architectures: s390
+:Type: vcpu ioctl
+:Parameters: struct kvm_s390_mem_op (in)
+:Returns: = 0 on success,
+ < 0 on generic error (e.g. -EFAULT or -ENOMEM),
+ > 0 if an exception occurred while walking the page tables
Read or write data from/to the logical (virtual) memory of a VCPU.
-Parameters are specified via the following structure:
+Parameters are specified via the following structure::
-struct kvm_s390_mem_op {
+ struct kvm_s390_mem_op {
__u64 gaddr; /* the guest address */
__u64 flags; /* flags */
__u32 size; /* amount of bytes */
@@ -3084,7 +3433,7 @@
__u64 buf; /* buffer in userspace */
__u8 ar; /* the access register number */
__u8 reserved[31]; /* should be set to 0 */
-};
+ };
The type of operation is specified in the "op" field. It is either
KVM_S390_MEMOP_LOGICAL_READ for reading from logical memory space or
@@ -3111,24 +3460,25 @@
KVM with the currently defined set of flags.
4.90 KVM_S390_GET_SKEYS
+-----------------------
-Capability: KVM_CAP_S390_SKEYS
-Architectures: s390
-Type: vm ioctl
-Parameters: struct kvm_s390_skeys
-Returns: 0 on success, KVM_S390_GET_KEYS_NONE if guest is not using storage
- keys, negative value on error
+:Capability: KVM_CAP_S390_SKEYS
+:Architectures: s390
+:Type: vm ioctl
+:Parameters: struct kvm_s390_skeys
+:Returns: 0 on success, KVM_S390_GET_KEYS_NONE if guest is not using storage
+ keys, negative value on error
This ioctl is used to get guest storage key values on the s390
-architecture. The ioctl takes parameters via the kvm_s390_skeys struct.
+architecture. The ioctl takes parameters via the kvm_s390_skeys struct::
-struct kvm_s390_skeys {
+ struct kvm_s390_skeys {
__u64 start_gfn;
__u64 count;
__u64 skeydata_addr;
__u32 flags;
__u32 reserved[9];
-};
+ };
The start_gfn field is the number of the first guest frame whose storage keys
you want to get.
@@ -3142,12 +3492,13 @@
bytes. This buffer will be filled with storage key data by the ioctl.
4.91 KVM_S390_SET_SKEYS
+-----------------------
-Capability: KVM_CAP_S390_SKEYS
-Architectures: s390
-Type: vm ioctl
-Parameters: struct kvm_s390_skeys
-Returns: 0 on success, negative value on error
+:Capability: KVM_CAP_S390_SKEYS
+:Architectures: s390
+:Type: vm ioctl
+:Parameters: struct kvm_s390_skeys
+:Returns: 0 on success, negative value on error
This ioctl is used to set guest storage key values on the s390
architecture. The ioctl takes parameters via the kvm_s390_skeys struct.
@@ -3169,21 +3520,27 @@
the ioctl will return -EINVAL.
4.92 KVM_S390_IRQ
+-----------------
-Capability: KVM_CAP_S390_INJECT_IRQ
-Architectures: s390
-Type: vcpu ioctl
-Parameters: struct kvm_s390_irq (in)
-Returns: 0 on success, -1 on error
+:Capability: KVM_CAP_S390_INJECT_IRQ
+:Architectures: s390
+:Type: vcpu ioctl
+:Parameters: struct kvm_s390_irq (in)
+:Returns: 0 on success, -1 on error
+
Errors:
- EINVAL: interrupt type is invalid
- type is KVM_S390_SIGP_STOP and flag parameter is invalid value
+
+
+ ====== =================================================================
+ EINVAL interrupt type is invalid
+ type is KVM_S390_SIGP_STOP and flag parameter is invalid value,
type is KVM_S390_INT_EXTERNAL_CALL and code is bigger
- than the maximum of VCPUs
- EBUSY: type is KVM_S390_SIGP_SET_PREFIX and vcpu is not stopped
- type is KVM_S390_SIGP_STOP and a stop irq is already pending
+ than the maximum of VCPUs
+ EBUSY type is KVM_S390_SIGP_SET_PREFIX and vcpu is not stopped,
+ type is KVM_S390_SIGP_STOP and a stop irq is already pending,
type is KVM_S390_INT_EXTERNAL_CALL and an external call interrupt
- is already pending
+ is already pending
+ ====== =================================================================
Allows to inject an interrupt to the guest.
@@ -3191,9 +3548,9 @@
to inject additional payload which is not
possible via KVM_S390_INTERRUPT.
-Interrupt parameters are passed via kvm_s390_irq:
+Interrupt parameters are passed via kvm_s390_irq::
-struct kvm_s390_irq {
+ struct kvm_s390_irq {
__u64 type;
union {
struct kvm_s390_io_info io;
@@ -3206,44 +3563,45 @@
struct kvm_s390_mchk_info mchk;
char reserved[64];
} u;
-};
+ };
type can be one of the following:
-KVM_S390_SIGP_STOP - sigp stop; parameter in .stop
-KVM_S390_PROGRAM_INT - program check; parameters in .pgm
-KVM_S390_SIGP_SET_PREFIX - sigp set prefix; parameters in .prefix
-KVM_S390_RESTART - restart; no parameters
-KVM_S390_INT_CLOCK_COMP - clock comparator interrupt; no parameters
-KVM_S390_INT_CPU_TIMER - CPU timer interrupt; no parameters
-KVM_S390_INT_EMERGENCY - sigp emergency; parameters in .emerg
-KVM_S390_INT_EXTERNAL_CALL - sigp external call; parameters in .extcall
-KVM_S390_MCHK - machine check interrupt; parameters in .mchk
+- KVM_S390_SIGP_STOP - sigp stop; parameter in .stop
+- KVM_S390_PROGRAM_INT - program check; parameters in .pgm
+- KVM_S390_SIGP_SET_PREFIX - sigp set prefix; parameters in .prefix
+- KVM_S390_RESTART - restart; no parameters
+- KVM_S390_INT_CLOCK_COMP - clock comparator interrupt; no parameters
+- KVM_S390_INT_CPU_TIMER - CPU timer interrupt; no parameters
+- KVM_S390_INT_EMERGENCY - sigp emergency; parameters in .emerg
+- KVM_S390_INT_EXTERNAL_CALL - sigp external call; parameters in .extcall
+- KVM_S390_MCHK - machine check interrupt; parameters in .mchk
This is an asynchronous vcpu ioctl and can be invoked from any thread.
4.94 KVM_S390_GET_IRQ_STATE
+---------------------------
-Capability: KVM_CAP_S390_IRQ_STATE
-Architectures: s390
-Type: vcpu ioctl
-Parameters: struct kvm_s390_irq_state (out)
-Returns: >= number of bytes copied into buffer,
- -EINVAL if buffer size is 0,
- -ENOBUFS if buffer size is too small to fit all pending interrupts,
- -EFAULT if the buffer address was invalid
+:Capability: KVM_CAP_S390_IRQ_STATE
+:Architectures: s390
+:Type: vcpu ioctl
+:Parameters: struct kvm_s390_irq_state (out)
+:Returns: >= number of bytes copied into buffer,
+ -EINVAL if buffer size is 0,
+ -ENOBUFS if buffer size is too small to fit all pending interrupts,
+ -EFAULT if the buffer address was invalid
This ioctl allows userspace to retrieve the complete state of all currently
pending interrupts in a single buffer. Use cases include migration
and introspection. The parameter structure contains the address of a
-userspace buffer and its length:
+userspace buffer and its length::
-struct kvm_s390_irq_state {
+ struct kvm_s390_irq_state {
__u64 buf;
__u32 flags; /* will stay unused for compatibility reasons */
__u32 len;
__u32 reserved[4]; /* will stay unused for compatibility reasons */
-};
+ };
Userspace passes in the above struct and for each pending interrupt a
struct kvm_s390_irq is copied to the provided buffer.
@@ -3257,29 +3615,30 @@
may retry with a bigger buffer.
4.95 KVM_S390_SET_IRQ_STATE
+---------------------------
-Capability: KVM_CAP_S390_IRQ_STATE
-Architectures: s390
-Type: vcpu ioctl
-Parameters: struct kvm_s390_irq_state (in)
-Returns: 0 on success,
- -EFAULT if the buffer address was invalid,
- -EINVAL for an invalid buffer length (see below),
- -EBUSY if there were already interrupts pending,
- errors occurring when actually injecting the
+:Capability: KVM_CAP_S390_IRQ_STATE
+:Architectures: s390
+:Type: vcpu ioctl
+:Parameters: struct kvm_s390_irq_state (in)
+:Returns: 0 on success,
+ -EFAULT if the buffer address was invalid,
+ -EINVAL for an invalid buffer length (see below),
+ -EBUSY if there were already interrupts pending,
+ errors occurring when actually injecting the
interrupt. See KVM_S390_IRQ.
This ioctl allows userspace to set the complete state of all cpu-local
interrupts currently pending for the vcpu. It is intended for restoring
interrupt state after a migration. The input parameter is a userspace buffer
-containing a struct kvm_s390_irq_state:
+containing a struct kvm_s390_irq_state::
-struct kvm_s390_irq_state {
+ struct kvm_s390_irq_state {
__u64 buf;
__u32 flags; /* will stay unused for compatibility reasons */
__u32 len;
__u32 reserved[4]; /* will stay unused for compatibility reasons */
-};
+ };
The restrictions for flags and reserved apply as well.
(see KVM_S390_GET_IRQ_STATE)
@@ -3294,20 +3653,22 @@
which is the maximum number of possibly pending cpu-local interrupts.
4.96 KVM_SMI
+------------
-Capability: KVM_CAP_X86_SMM
-Architectures: x86
-Type: vcpu ioctl
-Parameters: none
-Returns: 0 on success, -1 on error
+:Capability: KVM_CAP_X86_SMM
+:Architectures: x86
+:Type: vcpu ioctl
+:Parameters: none
+:Returns: 0 on success, -1 on error
Queues an SMI on the thread's vcpu.
4.97 KVM_CAP_PPC_MULTITCE
+-------------------------
-Capability: KVM_CAP_PPC_MULTITCE
-Architectures: ppc
-Type: vm
+:Capability: KVM_CAP_PPC_MULTITCE
+:Architectures: ppc
+:Type: vm
This capability means the kernel is capable of handling hypercalls
H_PUT_TCE_INDIRECT and H_STUFF_TCE without passing those into the user
@@ -3329,26 +3690,27 @@
This capability is always enabled.
4.98 KVM_CREATE_SPAPR_TCE_64
+----------------------------
-Capability: KVM_CAP_SPAPR_TCE_64
-Architectures: powerpc
-Type: vm ioctl
-Parameters: struct kvm_create_spapr_tce_64 (in)
-Returns: file descriptor for manipulating the created TCE table
+:Capability: KVM_CAP_SPAPR_TCE_64
+:Architectures: powerpc
+:Type: vm ioctl
+:Parameters: struct kvm_create_spapr_tce_64 (in)
+:Returns: file descriptor for manipulating the created TCE table
This is an extension for KVM_CAP_SPAPR_TCE which only supports 32bit
windows, described in 4.62 KVM_CREATE_SPAPR_TCE
-This capability uses extended struct in ioctl interface:
+This capability uses extended struct in ioctl interface::
-/* for KVM_CAP_SPAPR_TCE_64 */
-struct kvm_create_spapr_tce_64 {
+ /* for KVM_CAP_SPAPR_TCE_64 */
+ struct kvm_create_spapr_tce_64 {
__u64 liobn;
__u32 page_shift;
__u32 flags;
__u64 offset; /* in pages */
__u64 size; /* in pages */
-};
+ };
The aim of extension is to support an additional bigger DMA window with
a variable page size.
@@ -3361,12 +3723,13 @@
The rest of functionality is identical to KVM_CREATE_SPAPR_TCE.
4.99 KVM_REINJECT_CONTROL
+-------------------------
-Capability: KVM_CAP_REINJECT_CONTROL
-Architectures: x86
-Type: vm ioctl
-Parameters: struct kvm_reinject_control (in)
-Returns: 0 on success,
+:Capability: KVM_CAP_REINJECT_CONTROL
+:Architectures: x86
+:Type: vm ioctl
+:Parameters: struct kvm_reinject_control (in)
+:Returns: 0 on success,
-EFAULT if struct kvm_reinject_control cannot be read,
-ENXIO if KVM_CREATE_PIT or KVM_CREATE_PIT2 didn't succeed earlier.
@@ -3376,21 +3739,24 @@
interrupt whenever there isn't a pending interrupt from i8254.
!reinject mode injects an interrupt as soon as a tick arrives.
-struct kvm_reinject_control {
+::
+
+ struct kvm_reinject_control {
__u8 pit_reinject;
__u8 reserved[31];
-};
+ };
pit_reinject = 0 (!reinject mode) is recommended, unless running an old
operating system that uses the PIT for timing (e.g. Linux 2.4.x).
4.100 KVM_PPC_CONFIGURE_V3_MMU
+------------------------------
-Capability: KVM_CAP_PPC_RADIX_MMU or KVM_CAP_PPC_HASH_MMU_V3
-Architectures: ppc
-Type: vm ioctl
-Parameters: struct kvm_ppc_mmuv3_cfg (in)
-Returns: 0 on success,
+:Capability: KVM_CAP_PPC_RADIX_MMU or KVM_CAP_PPC_HASH_MMU_V3
+:Architectures: ppc
+:Type: vm ioctl
+:Parameters: struct kvm_ppc_mmuv3_cfg (in)
+:Returns: 0 on success,
-EFAULT if struct kvm_ppc_mmuv3_cfg cannot be read,
-EINVAL if the configuration is invalid
@@ -3398,10 +3764,12 @@
page table) translation, and sets the pointer to the process table for
the guest.
-struct kvm_ppc_mmuv3_cfg {
+::
+
+ struct kvm_ppc_mmuv3_cfg {
__u64 flags;
__u64 process_table;
-};
+ };
There are two bits that can be set in flags; KVM_PPC_MMUV3_RADIX and
KVM_PPC_MMUV3_GTSE. KVM_PPC_MMUV3_RADIX, if set, configures the guest
@@ -3416,12 +3784,13 @@
the Power ISA V3.00, Book III section 5.7.6.1.
4.101 KVM_PPC_GET_RMMU_INFO
+---------------------------
-Capability: KVM_CAP_PPC_RADIX_MMU
-Architectures: ppc
-Type: vm ioctl
-Parameters: struct kvm_ppc_rmmu_info (out)
-Returns: 0 on success,
+:Capability: KVM_CAP_PPC_RADIX_MMU
+:Architectures: ppc
+:Type: vm ioctl
+:Parameters: struct kvm_ppc_rmmu_info (out)
+:Returns: 0 on success,
-EFAULT if struct kvm_ppc_rmmu_info cannot be written,
-EINVAL if no useful information can be returned
@@ -3430,14 +3799,16 @@
page sizes to put in the "AP" (actual page size) field for the tlbie
(TLB invalidate entry) instruction.
-struct kvm_ppc_rmmu_info {
+::
+
+ struct kvm_ppc_rmmu_info {
struct kvm_ppc_radix_geom {
__u8 page_shift;
__u8 level_bits[4];
__u8 pad[3];
} geometries[8];
__u32 ap_encodings[8];
-};
+ };
The geometries[] field gives up to 8 supported geometries for the
radix page table, in terms of the log base 2 of the smallest page
@@ -3450,19 +3821,54 @@
base 2 of the page size in the bottom 6 bits.
4.102 KVM_PPC_RESIZE_HPT_PREPARE
+--------------------------------
-Capability: KVM_CAP_SPAPR_RESIZE_HPT
-Architectures: powerpc
-Type: vm ioctl
-Parameters: struct kvm_ppc_resize_hpt (in)
-Returns: 0 on successful completion,
+:Capability: KVM_CAP_SPAPR_RESIZE_HPT
+:Architectures: powerpc
+:Type: vm ioctl
+:Parameters: struct kvm_ppc_resize_hpt (in)
+:Returns: 0 on successful completion,
>0 if a new HPT is being prepared, the value is an estimated
- number of milliseconds until preparation is complete
+ number of milliseconds until preparation is complete,
-EFAULT if struct kvm_reinject_control cannot be read,
- -EINVAL if the supplied shift or flags are invalid
- -ENOMEM if unable to allocate the new HPT
- -ENOSPC if there was a hash collision when moving existing
- HPT entries to the new HPT
+ -EINVAL if the supplied shift or flags are invalid,
+ -ENOMEM if unable to allocate the new HPT,
+ -ENOSPC if there was a hash collision
+
+::
+
+ struct kvm_ppc_rmmu_info {
+ struct kvm_ppc_radix_geom {
+ __u8 page_shift;
+ __u8 level_bits[4];
+ __u8 pad[3];
+ } geometries[8];
+ __u32 ap_encodings[8];
+ };
+
+The geometries[] field gives up to 8 supported geometries for the
+radix page table, in terms of the log base 2 of the smallest page
+size, and the number of bits indexed at each level of the tree, from
+the PTE level up to the PGD level in that order. Any unused entries
+will have 0 in the page_shift field.
+
+The ap_encodings gives the supported page sizes and their AP field
+encodings, encoded with the AP value in the top 3 bits and the log
+base 2 of the page size in the bottom 6 bits.
+
+4.102 KVM_PPC_RESIZE_HPT_PREPARE
+--------------------------------
+
+:Capability: KVM_CAP_SPAPR_RESIZE_HPT
+:Architectures: powerpc
+:Type: vm ioctl
+:Parameters: struct kvm_ppc_resize_hpt (in)
+:Returns: 0 on successful completion,
+ >0 if a new HPT is being prepared, the value is an estimated
+ number of milliseconds until preparation is complete,
+ -EFAULT if struct kvm_reinject_control cannot be read,
+ -EINVAL if the supplied shift or flags are invalid,when moving existing
+ HPT entries to the new HPT,
-EIO on other error conditions
Used to implement the PAPR extension for runtime resizing of a guest's
@@ -3480,6 +3886,7 @@
creates a new one as above.
If called when there is a pending HPT of the size requested, will:
+
* If preparation of the pending HPT is already complete, return 0
* If preparation of the pending HPT has failed, return an error
code, then discard the pending HPT.
@@ -3496,26 +3903,29 @@
it returns <= 0. The first call will initiate preparation, subsequent
ones will monitor preparation until it completes or fails.
-struct kvm_ppc_resize_hpt {
+::
+
+ struct kvm_ppc_resize_hpt {
__u64 flags;
__u32 shift;
__u32 pad;
-};
+ };
4.103 KVM_PPC_RESIZE_HPT_COMMIT
+-------------------------------
-Capability: KVM_CAP_SPAPR_RESIZE_HPT
-Architectures: powerpc
-Type: vm ioctl
-Parameters: struct kvm_ppc_resize_hpt (in)
-Returns: 0 on successful completion,
+:Capability: KVM_CAP_SPAPR_RESIZE_HPT
+:Architectures: powerpc
+:Type: vm ioctl
+:Parameters: struct kvm_ppc_resize_hpt (in)
+:Returns: 0 on successful completion,
-EFAULT if struct kvm_reinject_control cannot be read,
- -EINVAL if the supplied shift or flags are invalid
+ -EINVAL if the supplied shift or flags are invalid,
-ENXIO is there is no pending HPT, or the pending HPT doesn't
- have the requested size
- -EBUSY if the pending HPT is not fully prepared
+ have the requested size,
+ -EBUSY if the pending HPT is not fully prepared,
-ENOSPC if there was a hash collision when moving existing
- HPT entries to the new HPT
+ HPT entries to the new HPT,
-EIO on other error conditions
Used to implement the PAPR extension for runtime resizing of a guest's
@@ -3538,31 +3948,35 @@
On failure, the guest will still be operating on its previous HPT.
-struct kvm_ppc_resize_hpt {
+::
+
+ struct kvm_ppc_resize_hpt {
__u64 flags;
__u32 shift;
__u32 pad;
-};
+ };
4.104 KVM_X86_GET_MCE_CAP_SUPPORTED
+-----------------------------------
-Capability: KVM_CAP_MCE
-Architectures: x86
-Type: system ioctl
-Parameters: u64 mce_cap (out)
-Returns: 0 on success, -1 on error
+:Capability: KVM_CAP_MCE
+:Architectures: x86
+:Type: system ioctl
+:Parameters: u64 mce_cap (out)
+:Returns: 0 on success, -1 on error
Returns supported MCE capabilities. The u64 mce_cap parameter
has the same format as the MSR_IA32_MCG_CAP register. Supported
capabilities will have the corresponding bits set.
4.105 KVM_X86_SETUP_MCE
+-----------------------
-Capability: KVM_CAP_MCE
-Architectures: x86
-Type: vcpu ioctl
-Parameters: u64 mcg_cap (in)
-Returns: 0 on success,
+:Capability: KVM_CAP_MCE
+:Architectures: x86
+:Type: vcpu ioctl
+:Parameters: u64 mcg_cap (in)
+:Returns: 0 on success,
-EFAULT if u64 mcg_cap cannot be read,
-EINVAL if the requested number of banks is invalid,
-EINVAL if requested MCE capability is not supported.
@@ -3575,20 +3989,21 @@
retrieved with KVM_X86_GET_MCE_CAP_SUPPORTED.
4.106 KVM_X86_SET_MCE
+---------------------
-Capability: KVM_CAP_MCE
-Architectures: x86
-Type: vcpu ioctl
-Parameters: struct kvm_x86_mce (in)
-Returns: 0 on success,
+:Capability: KVM_CAP_MCE
+:Architectures: x86
+:Type: vcpu ioctl
+:Parameters: struct kvm_x86_mce (in)
+:Returns: 0 on success,
-EFAULT if struct kvm_x86_mce cannot be read,
-EINVAL if the bank number is invalid,
-EINVAL if VAL bit is not set in status field.
Inject a machine check error (MCE) into the guest. The input
-parameter is:
+parameter is::
-struct kvm_x86_mce {
+ struct kvm_x86_mce {
__u64 status;
__u64 addr;
__u64 misc;
@@ -3596,7 +4011,7 @@
__u8 bank;
__u8 pad1[7];
__u64 pad2[3];
-};
+ };
If the MCE being reported is an uncorrected error, KVM will
inject it as an MCE exception into the guest. If the guest
@@ -3608,15 +4023,17 @@
not holding a previously reported uncorrected error).
4.107 KVM_S390_GET_CMMA_BITS
+----------------------------
-Capability: KVM_CAP_S390_CMMA_MIGRATION
-Architectures: s390
-Type: vm ioctl
-Parameters: struct kvm_s390_cmma_log (in, out)
-Returns: 0 on success, a negative value on error
+:Capability: KVM_CAP_S390_CMMA_MIGRATION
+:Architectures: s390
+:Type: vm ioctl
+:Parameters: struct kvm_s390_cmma_log (in, out)
+:Returns: 0 on success, a negative value on error
This ioctl is used to get the values of the CMMA bits on the s390
architecture. It is meant to be used in two scenarios:
+
- During live migration to save the CMMA values. Live migration needs
to be enabled via the KVM_REQ_START_MIGRATION VM property.
- To non-destructively peek at the CMMA values, with the flag
@@ -3626,9 +4043,12 @@
values are written to a buffer whose location is indicated via the "values"
member in the kvm_s390_cmma_log struct. The values in the input struct are
also updated as needed.
+
Each CMMA value takes up one byte.
-struct kvm_s390_cmma_log {
+::
+
+ struct kvm_s390_cmma_log {
__u64 start_gfn;
__u32 count;
__u32 flags;
@@ -3637,7 +4057,7 @@
__u64 mask;
};
__u64 values;
-};
+ };
start_gfn is the number of the first guest frame whose CMMA values are
to be retrieved,
@@ -3698,12 +4118,13 @@
present for the addresses (e.g. when using hugepages).
4.108 KVM_S390_SET_CMMA_BITS
+----------------------------
-Capability: KVM_CAP_S390_CMMA_MIGRATION
-Architectures: s390
-Type: vm ioctl
-Parameters: struct kvm_s390_cmma_log (in)
-Returns: 0 on success, a negative value on error
+:Capability: KVM_CAP_S390_CMMA_MIGRATION
+:Architectures: s390
+:Type: vm ioctl
+:Parameters: struct kvm_s390_cmma_log (in)
+:Returns: 0 on success, a negative value on error
This ioctl is used to set the values of the CMMA bits on the s390
architecture. It is meant to be used during live migration to restore
@@ -3711,16 +4132,18 @@
The ioctl takes parameters via the kvm_s390_cmma_values struct.
Each CMMA value takes up one byte.
-struct kvm_s390_cmma_log {
+::
+
+ struct kvm_s390_cmma_log {
__u64 start_gfn;
__u32 count;
__u32 flags;
union {
__u64 remaining;
__u64 mask;
- };
+ };
__u64 values;
-};
+ };
start_gfn indicates the starting guest frame number,
@@ -3743,26 +4166,27 @@
hugepages).
4.109 KVM_PPC_GET_CPU_CHAR
+--------------------------
-Capability: KVM_CAP_PPC_GET_CPU_CHAR
-Architectures: powerpc
-Type: vm ioctl
-Parameters: struct kvm_ppc_cpu_char (out)
-Returns: 0 on successful completion
+:Capability: KVM_CAP_PPC_GET_CPU_CHAR
+:Architectures: powerpc
+:Type: vm ioctl
+:Parameters: struct kvm_ppc_cpu_char (out)
+:Returns: 0 on successful completion,
-EFAULT if struct kvm_ppc_cpu_char cannot be written
This ioctl gives userspace information about certain characteristics
of the CPU relating to speculative execution of instructions and
possible information leakage resulting from speculative execution (see
CVE-2017-5715, CVE-2017-5753 and CVE-2017-5754). The information is
-returned in struct kvm_ppc_cpu_char, which looks like this:
+returned in struct kvm_ppc_cpu_char, which looks like this::
-struct kvm_ppc_cpu_char {
+ struct kvm_ppc_cpu_char {
__u64 character; /* characteristics of the CPU */
__u64 behaviour; /* recommended software behaviour */
__u64 character_mask; /* valid bits in character */
__u64 behaviour_mask; /* valid bits in behaviour */
-};
+ };
For extensibility, the character_mask and behaviour_mask fields
indicate which bits of character and behaviour have been filled in by
@@ -3789,12 +4213,13 @@
H_GET_CPU_CHARACTERISTICS hypercall.
4.110 KVM_MEMORY_ENCRYPT_OP
+---------------------------
-Capability: basic
-Architectures: x86
-Type: system
-Parameters: an opaque platform specific structure (in/out)
-Returns: 0 on success; -1 on error
+:Capability: basic
+:Architectures: x86
+:Type: vm
+:Parameters: an opaque platform specific structure (in/out)
+:Returns: 0 on success; -1 on error
If the platform supports creating encrypted VMs then this ioctl can be used
for issuing platform-specific memory encryption commands to manage those
@@ -3805,12 +4230,13 @@
Documentation/virt/kvm/amd-memory-encryption.rst.
4.111 KVM_MEMORY_ENCRYPT_REG_REGION
+-----------------------------------
-Capability: basic
-Architectures: x86
-Type: system
-Parameters: struct kvm_enc_region (in)
-Returns: 0 on success; -1 on error
+:Capability: basic
+:Architectures: x86
+:Type: system
+:Parameters: struct kvm_enc_region (in)
+:Returns: 0 on success; -1 on error
This ioctl can be used to register a guest memory region which may
contain encrypted data (e.g. guest RAM, SMRAM etc).
@@ -3828,60 +4254,71 @@
memory region registered with the ioctl.
4.112 KVM_MEMORY_ENCRYPT_UNREG_REGION
+-------------------------------------
-Capability: basic
-Architectures: x86
-Type: system
-Parameters: struct kvm_enc_region (in)
-Returns: 0 on success; -1 on error
+:Capability: basic
+:Architectures: x86
+:Type: system
+:Parameters: struct kvm_enc_region (in)
+:Returns: 0 on success; -1 on error
This ioctl can be used to unregister the guest memory region registered
with KVM_MEMORY_ENCRYPT_REG_REGION ioctl above.
4.113 KVM_HYPERV_EVENTFD
+------------------------
-Capability: KVM_CAP_HYPERV_EVENTFD
-Architectures: x86
-Type: vm ioctl
-Parameters: struct kvm_hyperv_eventfd (in)
+:Capability: KVM_CAP_HYPERV_EVENTFD
+:Architectures: x86
+:Type: vm ioctl
+:Parameters: struct kvm_hyperv_eventfd (in)
This ioctl (un)registers an eventfd to receive notifications from the guest on
the specified Hyper-V connection id through the SIGNAL_EVENT hypercall, without
causing a user exit. SIGNAL_EVENT hypercall with non-zero event flag number
(bits 24-31) still triggers a KVM_EXIT_HYPERV_HCALL user exit.
-struct kvm_hyperv_eventfd {
+::
+
+ struct kvm_hyperv_eventfd {
__u32 conn_id;
__s32 fd;
__u32 flags;
__u32 padding[3];
-};
+ };
-The conn_id field should fit within 24 bits:
+The conn_id field should fit within 24 bits::
-#define KVM_HYPERV_CONN_ID_MASK 0x00ffffff
+ #define KVM_HYPERV_CONN_ID_MASK 0x00ffffff
-The acceptable values for the flags field are:
+The acceptable values for the flags field are::
-#define KVM_HYPERV_EVENTFD_DEASSIGN (1 << 0)
+ #define KVM_HYPERV_EVENTFD_DEASSIGN (1 << 0)
-Returns: 0 on success,
- -EINVAL if conn_id or flags is outside the allowed range
- -ENOENT on deassign if the conn_id isn't registered
- -EEXIST on assign if the conn_id is already registered
+:Returns: 0 on success,
+ -EINVAL if conn_id or flags is outside the allowed range,
+ -ENOENT on deassign if the conn_id isn't registered,
+ -EEXIST on assign if the conn_id is already registered
4.114 KVM_GET_NESTED_STATE
+--------------------------
-Capability: KVM_CAP_NESTED_STATE
-Architectures: x86
-Type: vcpu ioctl
-Parameters: struct kvm_nested_state (in/out)
-Returns: 0 on success, -1 on error
+:Capability: KVM_CAP_NESTED_STATE
+:Architectures: x86
+:Type: vcpu ioctl
+:Parameters: struct kvm_nested_state (in/out)
+:Returns: 0 on success, -1 on error
+
Errors:
- E2BIG: the total state size exceeds the value of 'size' specified by
- the user; the size required will be written into size.
-struct kvm_nested_state {
+ ===== =============================================================
+ E2BIG the total state size exceeds the value of 'size' specified by
+ the user; the size required will be written into size.
+ ===== =============================================================
+
+::
+
+ struct kvm_nested_state {
__u16 flags;
__u16 format;
__u32 size;
@@ -3898,33 +4335,38 @@
struct kvm_vmx_nested_state_data vmx[0];
struct kvm_svm_nested_state_data svm[0];
} data;
-};
+ };
-#define KVM_STATE_NESTED_GUEST_MODE 0x00000001
-#define KVM_STATE_NESTED_RUN_PENDING 0x00000002
-#define KVM_STATE_NESTED_EVMCS 0x00000004
+ #define KVM_STATE_NESTED_GUEST_MODE 0x00000001
+ #define KVM_STATE_NESTED_RUN_PENDING 0x00000002
+ #define KVM_STATE_NESTED_EVMCS 0x00000004
-#define KVM_STATE_NESTED_FORMAT_VMX 0
-#define KVM_STATE_NESTED_FORMAT_SVM 1
+ #define KVM_STATE_NESTED_FORMAT_VMX 0
+ #define KVM_STATE_NESTED_FORMAT_SVM 1
-#define KVM_STATE_NESTED_VMX_VMCS_SIZE 0x1000
+ #define KVM_STATE_NESTED_VMX_VMCS_SIZE 0x1000
-#define KVM_STATE_NESTED_VMX_SMM_GUEST_MODE 0x00000001
-#define KVM_STATE_NESTED_VMX_SMM_VMXON 0x00000002
+ #define KVM_STATE_NESTED_VMX_SMM_GUEST_MODE 0x00000001
+ #define KVM_STATE_NESTED_VMX_SMM_VMXON 0x00000002
-struct kvm_vmx_nested_state_hdr {
+ #define KVM_STATE_VMX_PREEMPTION_TIMER_DEADLINE 0x00000001
+
+ struct kvm_vmx_nested_state_hdr {
__u64 vmxon_pa;
__u64 vmcs12_pa;
struct {
__u16 flags;
} smm;
-};
-struct kvm_vmx_nested_state_data {
+ __u32 flags;
+ __u64 preemption_timer_deadline;
+ };
+
+ struct kvm_vmx_nested_state_data {
__u8 vmcs12[KVM_STATE_NESTED_VMX_VMCS_SIZE];
__u8 shadow_vmcs12[KVM_STATE_NESTED_VMX_VMCS_SIZE];
-};
+ };
This ioctl copies the vcpu's nested virtualization state from the kernel to
userspace.
@@ -3933,24 +4375,26 @@
to the KVM_CHECK_EXTENSION ioctl().
4.115 KVM_SET_NESTED_STATE
+--------------------------
-Capability: KVM_CAP_NESTED_STATE
-Architectures: x86
-Type: vcpu ioctl
-Parameters: struct kvm_nested_state (in)
-Returns: 0 on success, -1 on error
+:Capability: KVM_CAP_NESTED_STATE
+:Architectures: x86
+:Type: vcpu ioctl
+:Parameters: struct kvm_nested_state (in)
+:Returns: 0 on success, -1 on error
This copies the vcpu's kvm_nested_state struct from userspace to the kernel.
For the definition of struct kvm_nested_state, see KVM_GET_NESTED_STATE.
4.116 KVM_(UN)REGISTER_COALESCED_MMIO
+-------------------------------------
-Capability: KVM_CAP_COALESCED_MMIO (for coalesced mmio)
- KVM_CAP_COALESCED_PIO (for coalesced pio)
-Architectures: all
-Type: vm ioctl
-Parameters: struct kvm_coalesced_mmio_zone
-Returns: 0 on success, < 0 on error
+:Capability: KVM_CAP_COALESCED_MMIO (for coalesced mmio)
+ KVM_CAP_COALESCED_PIO (for coalesced pio)
+:Architectures: all
+:Type: vm ioctl
+:Parameters: struct kvm_coalesced_mmio_zone
+:Returns: 0 on success, < 0 on error
Coalesced I/O is a performance optimization that defers hardware
register write emulation so that userspace exits are avoided. It is
@@ -3972,15 +4416,18 @@
to I/O ports.
4.117 KVM_CLEAR_DIRTY_LOG (vm ioctl)
+------------------------------------
-Capability: KVM_CAP_MANUAL_DIRTY_LOG_PROTECT2
-Architectures: x86, arm, arm64, mips
-Type: vm ioctl
-Parameters: struct kvm_dirty_log (in)
-Returns: 0 on success, -1 on error
+:Capability: KVM_CAP_MANUAL_DIRTY_LOG_PROTECT2
+:Architectures: x86, arm, arm64, mips
+:Type: vm ioctl
+:Parameters: struct kvm_dirty_log (in)
+:Returns: 0 on success, -1 on error
-/* for KVM_CLEAR_DIRTY_LOG */
-struct kvm_clear_dirty_log {
+::
+
+ /* for KVM_CLEAR_DIRTY_LOG */
+ struct kvm_clear_dirty_log {
__u32 slot;
__u32 num_pages;
__u64 first_page;
@@ -3988,7 +4435,7 @@
void __user *dirty_bitmap; /* one bit per page */
__u64 padding;
};
-};
+ };
The ioctl clears the dirty status of pages in a memory slot, according to
the bitmap that is passed in struct kvm_clear_dirty_log's dirty_bitmap
@@ -4012,20 +4459,23 @@
that KVM_CAP_MANUAL_DIRTY_LOG_PROTECT2 is present.
4.118 KVM_GET_SUPPORTED_HV_CPUID
+--------------------------------
-Capability: KVM_CAP_HYPERV_CPUID
-Architectures: x86
-Type: vcpu ioctl
-Parameters: struct kvm_cpuid2 (in/out)
-Returns: 0 on success, -1 on error
+:Capability: KVM_CAP_HYPERV_CPUID
+:Architectures: x86
+:Type: vcpu ioctl
+:Parameters: struct kvm_cpuid2 (in/out)
+:Returns: 0 on success, -1 on error
-struct kvm_cpuid2 {
+::
+
+ struct kvm_cpuid2 {
__u32 nent;
__u32 padding;
struct kvm_cpuid_entry2 entries[0];
-};
+ };
-struct kvm_cpuid_entry2 {
+ struct kvm_cpuid_entry2 {
__u32 function;
__u32 index;
__u32 flags;
@@ -4034,7 +4484,7 @@
__u32 ecx;
__u32 edx;
__u32 padding[3];
-};
+ };
This ioctl returns x86 cpuid features leaves related to Hyper-V emulation in
KVM. Userspace can use the information returned by this ioctl to construct
@@ -4047,18 +4497,21 @@
leaves (0x40000000, 0x40000001).
Currently, the following list of CPUID leaves are returned:
- HYPERV_CPUID_VENDOR_AND_MAX_FUNCTIONS
- HYPERV_CPUID_INTERFACE
- HYPERV_CPUID_VERSION
- HYPERV_CPUID_FEATURES
- HYPERV_CPUID_ENLIGHTMENT_INFO
- HYPERV_CPUID_IMPLEMENT_LIMITS
- HYPERV_CPUID_NESTED_FEATURES
+ - HYPERV_CPUID_VENDOR_AND_MAX_FUNCTIONS
+ - HYPERV_CPUID_INTERFACE
+ - HYPERV_CPUID_VERSION
+ - HYPERV_CPUID_FEATURES
+ - HYPERV_CPUID_ENLIGHTMENT_INFO
+ - HYPERV_CPUID_IMPLEMENT_LIMITS
+ - HYPERV_CPUID_NESTED_FEATURES
+ - HYPERV_CPUID_SYNDBG_VENDOR_AND_MAX_FUNCTIONS
+ - HYPERV_CPUID_SYNDBG_INTERFACE
+ - HYPERV_CPUID_SYNDBG_PLATFORM_CAPABILITIES
HYPERV_CPUID_NESTED_FEATURES leaf is only exposed when Enlightened VMCS was
enabled on the corresponding vCPU (KVM_CAP_HYPERV_ENLIGHTENED_VMCS).
-Userspace invokes KVM_GET_SUPPORTED_CPUID by passing a kvm_cpuid2 structure
+Userspace invokes KVM_GET_SUPPORTED_HV_CPUID by passing a kvm_cpuid2 structure
with the 'nent' field indicating the number of entries in the variable-size
array 'entries'. If the number of entries is too low to describe all Hyper-V
feature leaves, an error (E2BIG) is returned. If the number is more or equal
@@ -4069,17 +4522,25 @@
userspace should not expect to get any particular value there.
4.119 KVM_ARM_VCPU_FINALIZE
+---------------------------
-Architectures: arm, arm64
-Type: vcpu ioctl
-Parameters: int feature (in)
-Returns: 0 on success, -1 on error
+:Architectures: arm, arm64
+:Type: vcpu ioctl
+:Parameters: int feature (in)
+:Returns: 0 on success, -1 on error
+
Errors:
- EPERM: feature not enabled, needs configuration, or already finalized
- EINVAL: feature unknown or not present
+
+ ====== ==============================================================
+ EPERM feature not enabled, needs configuration, or already finalized
+ EINVAL feature unknown or not present
+ ====== ==============================================================
Recognised values for feature:
+
+ ===== ===========================================
arm64 KVM_ARM_VCPU_SVE (requires KVM_CAP_ARM_SVE)
+ ===== ===========================================
Finalizes the configuration of the specified vcpu feature.
@@ -4103,21 +4564,24 @@
using this ioctl.
4.120 KVM_SET_PMU_EVENT_FILTER
+------------------------------
-Capability: KVM_CAP_PMU_EVENT_FILTER
-Architectures: x86
-Type: vm ioctl
-Parameters: struct kvm_pmu_event_filter (in)
-Returns: 0 on success, -1 on error
+:Capability: KVM_CAP_PMU_EVENT_FILTER
+:Architectures: x86
+:Type: vm ioctl
+:Parameters: struct kvm_pmu_event_filter (in)
+:Returns: 0 on success, -1 on error
-struct kvm_pmu_event_filter {
+::
+
+ struct kvm_pmu_event_filter {
__u32 action;
__u32 nevents;
__u32 fixed_counter_bitmap;
__u32 flags;
__u32 pad[4];
__u64 events[0];
-};
+ };
This ioctl restricts the set of PMU events that the guest can program.
The argument holds a list of events which will be allowed or denied.
@@ -4128,13 +4592,232 @@
No flags are defined yet, the field must be zero.
-Valid values for 'action':
-#define KVM_PMU_EVENT_ALLOW 0
-#define KVM_PMU_EVENT_DENY 1
+Valid values for 'action'::
+
+ #define KVM_PMU_EVENT_ALLOW 0
+ #define KVM_PMU_EVENT_DENY 1
+
+4.121 KVM_PPC_SVM_OFF
+---------------------
+
+:Capability: basic
+:Architectures: powerpc
+:Type: vm ioctl
+:Parameters: none
+:Returns: 0 on successful completion,
+
+Errors:
+
+ ====== ================================================================
+ EINVAL if ultravisor failed to terminate the secure guest
+ ENOMEM if hypervisor failed to allocate new radix page tables for guest
+ ====== ================================================================
+
+This ioctl is used to turn off the secure mode of the guest or transition
+the guest from secure mode to normal mode. This is invoked when the guest
+is reset. This has no effect if called for a normal guest.
+
+This ioctl issues an ultravisor call to terminate the secure guest,
+unpins the VPA pages and releases all the device pages that are used to
+track the secure pages by hypervisor.
+
+4.122 KVM_S390_NORMAL_RESET
+---------------------------
+
+:Capability: KVM_CAP_S390_VCPU_RESETS
+:Architectures: s390
+:Type: vcpu ioctl
+:Parameters: none
+:Returns: 0
+
+This ioctl resets VCPU registers and control structures according to
+the cpu reset definition in the POP (Principles Of Operation).
+
+4.123 KVM_S390_INITIAL_RESET
+----------------------------
+
+:Capability: none
+:Architectures: s390
+:Type: vcpu ioctl
+:Parameters: none
+:Returns: 0
+
+This ioctl resets VCPU registers and control structures according to
+the initial cpu reset definition in the POP. However, the cpu is not
+put into ESA mode. This reset is a superset of the normal reset.
+
+4.124 KVM_S390_CLEAR_RESET
+--------------------------
+
+:Capability: KVM_CAP_S390_VCPU_RESETS
+:Architectures: s390
+:Type: vcpu ioctl
+:Parameters: none
+:Returns: 0
+
+This ioctl resets VCPU registers and control structures according to
+the clear cpu reset definition in the POP. However, the cpu is not put
+into ESA mode. This reset is a superset of the initial reset.
+
+
+4.125 KVM_S390_PV_COMMAND
+-------------------------
+
+:Capability: KVM_CAP_S390_PROTECTED
+:Architectures: s390
+:Type: vm ioctl
+:Parameters: struct kvm_pv_cmd
+:Returns: 0 on success, < 0 on error
+
+::
+
+ struct kvm_pv_cmd {
+ __u32 cmd; /* Command to be executed */
+ __u16 rc; /* Ultravisor return code */
+ __u16 rrc; /* Ultravisor return reason code */
+ __u64 data; /* Data or address */
+ __u32 flags; /* flags for future extensions. Must be 0 for now */
+ __u32 reserved[3];
+ };
+
+cmd values:
+
+KVM_PV_ENABLE
+ Allocate memory and register the VM with the Ultravisor, thereby
+ donating memory to the Ultravisor that will become inaccessible to
+ KVM. All existing CPUs are converted to protected ones. After this
+ command has succeeded, any CPU added via hotplug will become
+ protected during its creation as well.
+
+ Errors:
+
+ ===== =============================
+ EINTR an unmasked signal is pending
+ ===== =============================
+
+KVM_PV_DISABLE
+
+ Deregister the VM from the Ultravisor and reclaim the memory that
+ had been donated to the Ultravisor, making it usable by the kernel
+ again. All registered VCPUs are converted back to non-protected
+ ones.
+
+KVM_PV_VM_SET_SEC_PARMS
+ Pass the image header from VM memory to the Ultravisor in
+ preparation of image unpacking and verification.
+
+KVM_PV_VM_UNPACK
+ Unpack (protect and decrypt) a page of the encrypted boot image.
+
+KVM_PV_VM_VERIFY
+ Verify the integrity of the unpacked image. Only if this succeeds,
+ KVM is allowed to start protected VCPUs.
+
+4.126 KVM_X86_SET_MSR_FILTER
+----------------------------
+
+:Capability: KVM_X86_SET_MSR_FILTER
+:Architectures: x86
+:Type: vm ioctl
+:Parameters: struct kvm_msr_filter
+:Returns: 0 on success, < 0 on error
+
+::
+
+ struct kvm_msr_filter_range {
+ #define KVM_MSR_FILTER_READ (1 << 0)
+ #define KVM_MSR_FILTER_WRITE (1 << 1)
+ __u32 flags;
+ __u32 nmsrs; /* number of msrs in bitmap */
+ __u32 base; /* MSR index the bitmap starts at */
+ __u8 *bitmap; /* a 1 bit allows the operations in flags, 0 denies */
+ };
+
+ #define KVM_MSR_FILTER_MAX_RANGES 16
+ struct kvm_msr_filter {
+ #define KVM_MSR_FILTER_DEFAULT_ALLOW (0 << 0)
+ #define KVM_MSR_FILTER_DEFAULT_DENY (1 << 0)
+ __u32 flags;
+ struct kvm_msr_filter_range ranges[KVM_MSR_FILTER_MAX_RANGES];
+ };
+
+flags values for ``struct kvm_msr_filter_range``:
+
+``KVM_MSR_FILTER_READ``
+
+ Filter read accesses to MSRs using the given bitmap. A 0 in the bitmap
+ indicates that a read should immediately fail, while a 1 indicates that
+ a read for a particular MSR should be handled regardless of the default
+ filter action.
+
+``KVM_MSR_FILTER_WRITE``
+
+ Filter write accesses to MSRs using the given bitmap. A 0 in the bitmap
+ indicates that a write should immediately fail, while a 1 indicates that
+ a write for a particular MSR should be handled regardless of the default
+ filter action.
+
+``KVM_MSR_FILTER_READ | KVM_MSR_FILTER_WRITE``
+
+ Filter both read and write accesses to MSRs using the given bitmap. A 0
+ in the bitmap indicates that both reads and writes should immediately fail,
+ while a 1 indicates that reads and writes for a particular MSR are not
+ filtered by this range.
+
+flags values for ``struct kvm_msr_filter``:
+
+``KVM_MSR_FILTER_DEFAULT_ALLOW``
+
+ If no filter range matches an MSR index that is getting accessed, KVM will
+ fall back to allowing access to the MSR.
+
+``KVM_MSR_FILTER_DEFAULT_DENY``
+
+ If no filter range matches an MSR index that is getting accessed, KVM will
+ fall back to rejecting access to the MSR. In this mode, all MSRs that should
+ be processed by KVM need to explicitly be marked as allowed in the bitmaps.
+
+This ioctl allows user space to define up to 16 bitmaps of MSR ranges to
+specify whether a certain MSR access should be explicitly filtered for or not.
+
+If this ioctl has never been invoked, MSR accesses are not guarded and the
+default KVM in-kernel emulation behavior is fully preserved.
+
+Calling this ioctl with an empty set of ranges (all nmsrs == 0) disables MSR
+filtering. In that mode, ``KVM_MSR_FILTER_DEFAULT_DENY`` is invalid and causes
+an error.
+
+As soon as the filtering is in place, every MSR access is processed through
+the filtering except for accesses to the x2APIC MSRs (from 0x800 to 0x8ff);
+x2APIC MSRs are always allowed, independent of the ``default_allow`` setting,
+and their behavior depends on the ``X2APIC_ENABLE`` bit of the APIC base
+register.
+
+If a bit is within one of the defined ranges, read and write accesses are
+guarded by the bitmap's value for the MSR index if the kind of access
+is included in the ``struct kvm_msr_filter_range`` flags. If no range
+cover this particular access, the behavior is determined by the flags
+field in the kvm_msr_filter struct: ``KVM_MSR_FILTER_DEFAULT_ALLOW``
+and ``KVM_MSR_FILTER_DEFAULT_DENY``.
+
+Each bitmap range specifies a range of MSRs to potentially allow access on.
+The range goes from MSR index [base .. base+nmsrs]. The flags field
+indicates whether reads, writes or both reads and writes are filtered
+by setting a 1 bit in the bitmap for the corresponding MSR index.
+
+If an MSR access is not permitted through the filtering, it generates a
+#GP inside the guest. When combined with KVM_CAP_X86_USER_SPACE_MSR, that
+allows user space to deflect and potentially handle various MSR accesses
+into user space.
+
+Note, invoking this ioctl with a vCPU is running is inherently racy. However,
+KVM does guarantee that vCPUs will see either the previous filter or the new
+filter, e.g. MSRs with identical settings in both the old and new filter will
+have deterministic behavior.
5. The kvm_run structure
-------------------------
+========================
Application code obtains a pointer to the kvm_run structure by
mmap()ing a vcpu fd. From that point, application code can control
@@ -4142,13 +4825,17 @@
ioctl, and obtain information about the reason KVM_RUN returned by
looking up structure members.
-struct kvm_run {
+::
+
+ struct kvm_run {
/* in */
__u8 request_interrupt_window;
Request that KVM_RUN return when it becomes possible to inject external
interrupts into the guest. Useful in conjunction with KVM_INTERRUPT.
+::
+
__u8 immediate_exit;
This field is polled once when KVM_RUN starts; if non-zero, KVM_RUN
@@ -4160,6 +4847,8 @@
This field is ignored if KVM_CAP_IMMEDIATE_EXIT is not available.
+::
+
__u8 padding1[6];
/* out */
@@ -4169,16 +4858,22 @@
application code why KVM_RUN has returned. Allowable values for this
field are detailed below.
+::
+
__u8 ready_for_interrupt_injection;
If request_interrupt_window has been specified, this field indicates
an interrupt can be injected now with KVM_INTERRUPT.
+::
+
__u8 if_flag;
The value of the current interrupt flag. Only valid if in-kernel
local APIC is not used.
+::
+
__u16 flags;
More architecture-specific flags detailing state of the VCPU that may
@@ -4186,17 +4881,23 @@
KVM_RUN_X86_SMM, which is valid on x86 machines and is set if the
VCPU is in system management mode.
+::
+
/* in (pre_kvm_run), out (post_kvm_run) */
__u64 cr8;
The value of the cr8 register. Only valid if in-kernel local APIC is
not used. Both input and output.
+::
+
__u64 apic_base;
The value of the APIC BASE msr. Only valid if in-kernel local
APIC is not used. Both input and output.
+::
+
union {
/* KVM_EXIT_UNKNOWN */
struct {
@@ -4207,15 +4908,20 @@
reasons. Further architecture-specific information is available in
hardware_exit_reason.
+::
+
/* KVM_EXIT_FAIL_ENTRY */
struct {
__u64 hardware_entry_failure_reason;
+ __u32 cpu; /* if KVM_LAST_CPU */
} fail_entry;
If exit_reason is KVM_EXIT_FAIL_ENTRY, the vcpu could not be run due
to unknown reasons. Further architecture-specific information is
available in hardware_entry_failure_reason.
+::
+
/* KVM_EXIT_EXCEPTION */
struct {
__u32 exception;
@@ -4224,10 +4930,12 @@
Unused.
+::
+
/* KVM_EXIT_IO */
struct {
-#define KVM_EXIT_IO_IN 0
-#define KVM_EXIT_IO_OUT 1
+ #define KVM_EXIT_IO_IN 0
+ #define KVM_EXIT_IO_OUT 1
__u8 direction;
__u8 size; /* bytes */
__u16 port;
@@ -4241,6 +4949,8 @@
where kvm expects application code to place the data for the next
KVM_RUN invocation (KVM_EXIT_IO_IN). Data format is a packed array.
+::
+
/* KVM_EXIT_DEBUG */
struct {
struct kvm_debug_exit_arch arch;
@@ -4249,6 +4959,8 @@
If the exit_reason is KVM_EXIT_DEBUG, then a vcpu is processing a debug event
for which architecture specific information is returned.
+::
+
/* KVM_EXIT_MMIO */
struct {
__u64 phys_addr;
@@ -4266,13 +4978,17 @@
appear if the VCPU performed a load or store of the appropriate width directly
to the byte array.
-NOTE: For KVM_EXIT_IO, KVM_EXIT_MMIO, KVM_EXIT_OSI, KVM_EXIT_PAPR and
- KVM_EXIT_EPR the corresponding
-operations are complete (and guest state is consistent) only after userspace
-has re-entered the kernel with KVM_RUN. The kernel side will first finish
-incomplete operations and then check for pending signals. Userspace
-can re-enter the guest with an unmasked signal pending to complete
-pending operations.
+.. note::
+
+ For KVM_EXIT_IO, KVM_EXIT_MMIO, KVM_EXIT_OSI, KVM_EXIT_PAPR,
+ KVM_EXIT_EPR, KVM_EXIT_X86_RDMSR and KVM_EXIT_X86_WRMSR the corresponding
+ operations are complete (and guest state is consistent) only after userspace
+ has re-entered the kernel with KVM_RUN. The kernel side will first finish
+ incomplete operations and then check for pending signals. Userspace
+ can re-enter the guest with an unmasked signal pending to complete
+ pending operations.
+
+::
/* KVM_EXIT_HYPERCALL */
struct {
@@ -4285,7 +5001,10 @@
Unused. This was once used for 'hypercall to userspace'. To implement
such functionality, use KVM_EXIT_IO (x86) or KVM_EXIT_MMIO (all except s390).
-Note KVM_EXIT_IO is significantly faster than KVM_EXIT_MMIO.
+
+.. note:: KVM_EXIT_IO is significantly faster than KVM_EXIT_MMIO.
+
+::
/* KVM_EXIT_TPR_ACCESS */
struct {
@@ -4296,6 +5015,8 @@
To be documented (KVM_TPR_ACCESS_REPORTING).
+::
+
/* KVM_EXIT_S390_SIEIC */
struct {
__u8 icptcode;
@@ -4307,16 +5028,20 @@
s390 specific.
+::
+
/* KVM_EXIT_S390_RESET */
-#define KVM_S390_RESET_POR 1
-#define KVM_S390_RESET_CLEAR 2
-#define KVM_S390_RESET_SUBSYSTEM 4
-#define KVM_S390_RESET_CPU_INIT 8
-#define KVM_S390_RESET_IPL 16
+ #define KVM_S390_RESET_POR 1
+ #define KVM_S390_RESET_CLEAR 2
+ #define KVM_S390_RESET_SUBSYSTEM 4
+ #define KVM_S390_RESET_CPU_INIT 8
+ #define KVM_S390_RESET_IPL 16
__u64 s390_reset_flags;
s390 specific.
+::
+
/* KVM_EXIT_S390_UCONTROL */
struct {
__u64 trans_exc_code;
@@ -4331,6 +5056,8 @@
Principles of Operation Book in the Chapter for Dynamic Address Translation
(DAT)
+::
+
/* KVM_EXIT_DCR */
struct {
__u32 dcrn;
@@ -4340,6 +5067,8 @@
Deprecated - was used for 440 KVM.
+::
+
/* KVM_EXIT_OSI */
struct {
__u64 gprs[32];
@@ -4353,6 +5082,8 @@
necessary. Upon guest entry all guest GPRs will then be replaced by the values
in this struct.
+::
+
/* KVM_EXIT_PAPR_HCALL */
struct {
__u64 nr;
@@ -4370,6 +5101,8 @@
Requirements (PAPR) document available from www.power.org (free
developer registration required to access it).
+::
+
/* KVM_EXIT_S390_TSCH */
struct {
__u16 subchannel_id;
@@ -4386,6 +5119,8 @@
subchannel_nr, io_int_parm and io_int_word contain the parameters for that
interrupt. ipb is needed for instruction parameter decoding.
+::
+
/* KVM_EXIT_EPR */
struct {
__u32 epr;
@@ -4405,11 +5140,13 @@
external interrupt has just been delivered into the guest. User space
should put the acknowledged interrupt vector into the 'epr' field.
+::
+
/* KVM_EXIT_SYSTEM_EVENT */
struct {
-#define KVM_SYSTEM_EVENT_SHUTDOWN 1
-#define KVM_SYSTEM_EVENT_RESET 2
-#define KVM_SYSTEM_EVENT_CRASH 3
+ #define KVM_SYSTEM_EVENT_SHUTDOWN 1
+ #define KVM_SYSTEM_EVENT_RESET 2
+ #define KVM_SYSTEM_EVENT_CRASH 3
__u32 type;
__u64 flags;
} system_event;
@@ -4422,18 +5159,21 @@
specific flags for the system-level event.
Valid values for 'type' are:
- KVM_SYSTEM_EVENT_SHUTDOWN -- the guest has requested a shutdown of the
+
+ - KVM_SYSTEM_EVENT_SHUTDOWN -- the guest has requested a shutdown of the
VM. Userspace is not obliged to honour this, and if it does honour
this does not need to destroy the VM synchronously (ie it may call
KVM_RUN again before shutdown finally occurs).
- KVM_SYSTEM_EVENT_RESET -- the guest has requested a reset of the VM.
+ - KVM_SYSTEM_EVENT_RESET -- the guest has requested a reset of the VM.
As with SHUTDOWN, userspace can choose to ignore the request, or
to schedule the reset to occur in the future and may call KVM_RUN again.
- KVM_SYSTEM_EVENT_CRASH -- the guest crash occurred and the guest
+ - KVM_SYSTEM_EVENT_CRASH -- the guest crash occurred and the guest
has requested a crash condition maintenance. Userspace can choose
to ignore the request, or to gather VM memory core dump and/or
reset/shutdown of the VM.
+::
+
/* KVM_EXIT_IOAPIC_EOI */
struct {
__u8 vector;
@@ -4446,9 +5186,12 @@
it is still asserted. Vector is the LAPIC interrupt vector for which the
EOI was received.
+::
+
struct kvm_hyperv_exit {
-#define KVM_EXIT_HYPERV_SYNIC 1
-#define KVM_EXIT_HYPERV_HCALL 2
+ #define KVM_EXIT_HYPERV_SYNIC 1
+ #define KVM_EXIT_HYPERV_HCALL 2
+ #define KVM_EXIT_HYPERV_SYNDBG 3
__u32 type;
__u32 pad1;
union {
@@ -4464,18 +5207,112 @@
__u64 result;
__u64 params[2];
} hcall;
+ struct {
+ __u32 msr;
+ __u32 pad2;
+ __u64 control;
+ __u64 status;
+ __u64 send_page;
+ __u64 recv_page;
+ __u64 pending_page;
+ } syndbg;
} u;
};
/* KVM_EXIT_HYPERV */
struct kvm_hyperv_exit hyperv;
+
Indicates that the VCPU exits into userspace to process some tasks
related to Hyper-V emulation.
+
Valid values for 'type' are:
- KVM_EXIT_HYPERV_SYNIC -- synchronously notify user-space about
+
+ - KVM_EXIT_HYPERV_SYNIC -- synchronously notify user-space about
+
Hyper-V SynIC state change. Notification is used to remap SynIC
event/message pages and to enable/disable SynIC messages/events processing
in userspace.
+ - KVM_EXIT_HYPERV_SYNDBG -- synchronously notify user-space about
+
+Hyper-V Synthetic debugger state change. Notification is used to either update
+the pending_page location or to send a control command (send the buffer located
+in send_page or recv a buffer to recv_page).
+
+::
+
+ /* KVM_EXIT_ARM_NISV */
+ struct {
+ __u64 esr_iss;
+ __u64 fault_ipa;
+ } arm_nisv;
+
+Used on arm and arm64 systems. If a guest accesses memory not in a memslot,
+KVM will typically return to userspace and ask it to do MMIO emulation on its
+behalf. However, for certain classes of instructions, no instruction decode
+(direction, length of memory access) is provided, and fetching and decoding
+the instruction from the VM is overly complicated to live in the kernel.
+
+Historically, when this situation occurred, KVM would print a warning and kill
+the VM. KVM assumed that if the guest accessed non-memslot memory, it was
+trying to do I/O, which just couldn't be emulated, and the warning message was
+phrased accordingly. However, what happened more often was that a guest bug
+caused access outside the guest memory areas which should lead to a more
+meaningful warning message and an external abort in the guest, if the access
+did not fall within an I/O window.
+
+Userspace implementations can query for KVM_CAP_ARM_NISV_TO_USER, and enable
+this capability at VM creation. Once this is done, these types of errors will
+instead return to userspace with KVM_EXIT_ARM_NISV, with the valid bits from
+the HSR (arm) and ESR_EL2 (arm64) in the esr_iss field, and the faulting IPA
+in the fault_ipa field. Userspace can either fix up the access if it's
+actually an I/O access by decoding the instruction from guest memory (if it's
+very brave) and continue executing the guest, or it can decide to suspend,
+dump, or restart the guest.
+
+Note that KVM does not skip the faulting instruction as it does for
+KVM_EXIT_MMIO, but userspace has to emulate any change to the processing state
+if it decides to decode and emulate the instruction.
+
+::
+
+ /* KVM_EXIT_X86_RDMSR / KVM_EXIT_X86_WRMSR */
+ struct {
+ __u8 error; /* user -> kernel */
+ __u8 pad[7];
+ __u32 reason; /* kernel -> user */
+ __u32 index; /* kernel -> user */
+ __u64 data; /* kernel <-> user */
+ } msr;
+
+Used on x86 systems. When the VM capability KVM_CAP_X86_USER_SPACE_MSR is
+enabled, MSR accesses to registers that would invoke a #GP by KVM kernel code
+will instead trigger a KVM_EXIT_X86_RDMSR exit for reads and KVM_EXIT_X86_WRMSR
+exit for writes.
+
+The "reason" field specifies why the MSR trap occurred. User space will only
+receive MSR exit traps when a particular reason was requested during through
+ENABLE_CAP. Currently valid exit reasons are:
+
+ KVM_MSR_EXIT_REASON_UNKNOWN - access to MSR that is unknown to KVM
+ KVM_MSR_EXIT_REASON_INVAL - access to invalid MSRs or reserved bits
+ KVM_MSR_EXIT_REASON_FILTER - access blocked by KVM_X86_SET_MSR_FILTER
+
+For KVM_EXIT_X86_RDMSR, the "index" field tells user space which MSR the guest
+wants to read. To respond to this request with a successful read, user space
+writes the respective data into the "data" field and must continue guest
+execution to ensure the read data is transferred into guest register state.
+
+If the RDMSR request was unsuccessful, user space indicates that with a "1" in
+the "error" field. This will inject a #GP into the guest when the VCPU is
+executed again.
+
+For KVM_EXIT_X86_WRMSR, the "index" field tells user space which MSR the guest
+wants to write. Once finished processing the event, user space must continue
+vCPU execution. If the MSR write was unsuccessful, user space also sets the
+"error" field to "1".
+
+::
+
/* Fix the size of the union. */
char padding[256];
};
@@ -4500,18 +5337,20 @@
Userspace can query the validity of the structure by checking
kvm_valid_regs for specific bits. These bits are architecture specific
and usually define the validity of a groups of registers. (e.g. one bit
- for general purpose registers)
+for general purpose registers)
Please note that the kernel is allowed to use the kvm_run structure as the
primary storage for certain register types. Therefore, the kernel may use the
values in kvm_run even if the corresponding bit in kvm_dirty_regs is not set.
-};
+::
+
+ };
6. Capabilities that can be enabled on vCPUs
---------------------------------------------
+============================================
There are certain capabilities that change the behavior of the virtual CPU or
the virtual machine when enabled. To enable them, please see section 4.37.
@@ -4520,23 +5359,28 @@
The following information is provided along with the description:
- Architectures: which instruction set architectures provide this ioctl.
+ Architectures:
+ which instruction set architectures provide this ioctl.
x86 includes both i386 and x86_64.
- Target: whether this is a per-vcpu or per-vm capability.
+ Target:
+ whether this is a per-vcpu or per-vm capability.
- Parameters: what parameters are accepted by the capability.
+ Parameters:
+ what parameters are accepted by the capability.
- Returns: the return value. General error numbers (EBADF, ENOMEM, EINVAL)
+ Returns:
+ the return value. General error numbers (EBADF, ENOMEM, EINVAL)
are not detailed, but errors with specific meanings are.
6.1 KVM_CAP_PPC_OSI
+-------------------
-Architectures: ppc
-Target: vcpu
-Parameters: none
-Returns: 0 on success; -1 on error
+:Architectures: ppc
+:Target: vcpu
+:Parameters: none
+:Returns: 0 on success; -1 on error
This capability enables interception of OSI hypercalls that otherwise would
be treated as normal system calls to be injected into the guest. OSI hypercalls
@@ -4547,11 +5391,12 @@
6.2 KVM_CAP_PPC_PAPR
+--------------------
-Architectures: ppc
-Target: vcpu
-Parameters: none
-Returns: 0 on success; -1 on error
+:Architectures: ppc
+:Target: vcpu
+:Parameters: none
+:Returns: 0 on success; -1 on error
This capability enables interception of PAPR hypercalls. PAPR hypercalls are
done using the hypercall instruction "sc 1".
@@ -4567,18 +5412,21 @@
6.3 KVM_CAP_SW_TLB
+------------------
-Architectures: ppc
-Target: vcpu
-Parameters: args[0] is the address of a struct kvm_config_tlb
-Returns: 0 on success; -1 on error
+:Architectures: ppc
+:Target: vcpu
+:Parameters: args[0] is the address of a struct kvm_config_tlb
+:Returns: 0 on success; -1 on error
-struct kvm_config_tlb {
+::
+
+ struct kvm_config_tlb {
__u64 params;
__u64 array;
__u32 mmu_type;
__u32 array_len;
-};
+ };
Configures the virtual CPU's TLB array, establishing a shared memory area
between userspace and KVM. The "params" and "array" fields are userspace
@@ -4597,6 +5445,7 @@
on this vcpu.
For mmu types KVM_MMU_FSL_BOOKE_NOHV and KVM_MMU_FSL_BOOKE_HV:
+
- The "params" field is of type "struct kvm_book3e_206_tlb_params".
- The "array" field points to an array of type "struct
kvm_book3e_206_tlb_entry".
@@ -4610,11 +5459,12 @@
hardware ignores this value for TLB0.
6.4 KVM_CAP_S390_CSS_SUPPORT
+----------------------------
-Architectures: s390
-Target: vcpu
-Parameters: none
-Returns: 0 on success; -1 on error
+:Architectures: s390
+:Target: vcpu
+:Parameters: none
+:Returns: 0 on success; -1 on error
This capability enables support for handling of channel I/O instructions.
@@ -4628,11 +5478,12 @@
virtual machine is affected.
6.5 KVM_CAP_PPC_EPR
+-------------------
-Architectures: ppc
-Target: vcpu
-Parameters: args[0] defines whether the proxy facility is active
-Returns: 0 on success; -1 on error
+:Architectures: ppc
+:Target: vcpu
+:Parameters: args[0] defines whether the proxy facility is active
+:Returns: 0 on success; -1 on error
This capability enables or disables the delivery of interrupts through the
external proxy facility.
@@ -4646,62 +5497,70 @@
When this capability is enabled, KVM_EXIT_EPR can occur.
6.6 KVM_CAP_IRQ_MPIC
+--------------------
-Architectures: ppc
-Parameters: args[0] is the MPIC device fd
- args[1] is the MPIC CPU number for this vcpu
+:Architectures: ppc
+:Parameters: args[0] is the MPIC device fd;
+ args[1] is the MPIC CPU number for this vcpu
This capability connects the vcpu to an in-kernel MPIC device.
6.7 KVM_CAP_IRQ_XICS
+--------------------
-Architectures: ppc
-Target: vcpu
-Parameters: args[0] is the XICS device fd
- args[1] is the XICS CPU number (server ID) for this vcpu
+:Architectures: ppc
+:Target: vcpu
+:Parameters: args[0] is the XICS device fd;
+ args[1] is the XICS CPU number (server ID) for this vcpu
This capability connects the vcpu to an in-kernel XICS device.
6.8 KVM_CAP_S390_IRQCHIP
+------------------------
-Architectures: s390
-Target: vm
-Parameters: none
+:Architectures: s390
+:Target: vm
+:Parameters: none
This capability enables the in-kernel irqchip for s390. Please refer to
"4.24 KVM_CREATE_IRQCHIP" for details.
6.9 KVM_CAP_MIPS_FPU
+--------------------
-Architectures: mips
-Target: vcpu
-Parameters: args[0] is reserved for future use (should be 0).
+:Architectures: mips
+:Target: vcpu
+:Parameters: args[0] is reserved for future use (should be 0).
This capability allows the use of the host Floating Point Unit by the guest. It
allows the Config1.FP bit to be set to enable the FPU in the guest. Once this is
-done the KVM_REG_MIPS_FPR_* and KVM_REG_MIPS_FCR_* registers can be accessed
-(depending on the current guest FPU register mode), and the Status.FR,
+done the ``KVM_REG_MIPS_FPR_*`` and ``KVM_REG_MIPS_FCR_*`` registers can be
+accessed (depending on the current guest FPU register mode), and the Status.FR,
Config5.FRE bits are accessible via the KVM API and also from the guest,
depending on them being supported by the FPU.
6.10 KVM_CAP_MIPS_MSA
+---------------------
-Architectures: mips
-Target: vcpu
-Parameters: args[0] is reserved for future use (should be 0).
+:Architectures: mips
+:Target: vcpu
+:Parameters: args[0] is reserved for future use (should be 0).
This capability allows the use of the MIPS SIMD Architecture (MSA) by the guest.
It allows the Config3.MSAP bit to be set to enable the use of MSA by the guest.
-Once this is done the KVM_REG_MIPS_VEC_* and KVM_REG_MIPS_MSA_* registers can be
-accessed, and the Config5.MSAEn bit is accessible via the KVM API and also from
-the guest.
+Once this is done the ``KVM_REG_MIPS_VEC_*`` and ``KVM_REG_MIPS_MSA_*``
+registers can be accessed, and the Config5.MSAEn bit is accessible via the
+KVM API and also from the guest.
6.74 KVM_CAP_SYNC_REGS
-Architectures: s390, x86
-Target: s390: always enabled, x86: vcpu
-Parameters: none
-Returns: x86: KVM_CHECK_EXTENSION returns a bit-array indicating which register
-sets are supported (bitfields defined in arch/x86/include/uapi/asm/kvm.h).
+----------------------
+
+:Architectures: s390, x86
+:Target: s390: always enabled, x86: vcpu
+:Parameters: none
+:Returns: x86: KVM_CHECK_EXTENSION returns a bit-array indicating which register
+ sets are supported
+ (bitfields defined in arch/x86/include/uapi/asm/kvm.h).
As described above in the kvm_sync_regs struct info in section 5 (kvm_run):
KVM_CAP_SYNC_REGS "allow[s] userspace to access certain guest registers
@@ -4714,6 +5573,7 @@
For s390 specifics, please refer to the source code.
For x86:
+
- the register sets to be copied out to kvm_run are selectable
by userspace (rather that all sets being copied out for every exit).
- vcpu_events are available in addition to regs and sregs.
@@ -4730,23 +5590,26 @@
Unused bitfields in the bitarrays must be set to zero.
-struct kvm_sync_regs {
+::
+
+ struct kvm_sync_regs {
struct kvm_regs regs;
struct kvm_sregs sregs;
struct kvm_vcpu_events events;
-};
+ };
6.75 KVM_CAP_PPC_IRQ_XIVE
+-------------------------
-Architectures: ppc
-Target: vcpu
-Parameters: args[0] is the XIVE device fd
- args[1] is the XIVE CPU number (server ID) for this vcpu
+:Architectures: ppc
+:Target: vcpu
+:Parameters: args[0] is the XIVE device fd;
+ args[1] is the XIVE CPU number (server ID) for this vcpu
This capability connects the vcpu to an in-kernel XIVE device.
7. Capabilities that can be enabled on VMs
-------------------------------------------
+==========================================
There are certain capabilities that change the behavior of the virtual
machine when enabled. To enable them, please see section 4.37. Below
@@ -4755,20 +5618,24 @@
The following information is provided along with the description:
- Architectures: which instruction set architectures provide this ioctl.
+ Architectures:
+ which instruction set architectures provide this ioctl.
x86 includes both i386 and x86_64.
- Parameters: what parameters are accepted by the capability.
+ Parameters:
+ what parameters are accepted by the capability.
- Returns: the return value. General error numbers (EBADF, ENOMEM, EINVAL)
+ Returns:
+ the return value. General error numbers (EBADF, ENOMEM, EINVAL)
are not detailed, but errors with specific meanings are.
7.1 KVM_CAP_PPC_ENABLE_HCALL
+----------------------------
-Architectures: ppc
-Parameters: args[0] is the sPAPR hcall number
- args[1] is 0 to disable, 1 to enable in-kernel handling
+:Architectures: ppc
+:Parameters: args[0] is the sPAPR hcall number;
+ args[1] is 0 to disable, 1 to enable in-kernel handling
This capability controls whether individual sPAPR hypercalls (hcalls)
get handled by the kernel or not. Enabling or disabling in-kernel
@@ -4786,13 +5653,15 @@
error.
7.2 KVM_CAP_S390_USER_SIGP
+--------------------------
-Architectures: s390
-Parameters: none
+:Architectures: s390
+:Parameters: none
This capability controls which SIGP orders will be handled completely in user
space. With this capability enabled, all fast orders will be handled completely
in the kernel:
+
- SENSE
- SENSE RUNNING
- EXTERNAL CALL
@@ -4806,48 +5675,52 @@
old way of handling SIGP orders is used (partially in kernel and user space).
7.3 KVM_CAP_S390_VECTOR_REGISTERS
+---------------------------------
-Architectures: s390
-Parameters: none
-Returns: 0 on success, negative value on error
+:Architectures: s390
+:Parameters: none
+:Returns: 0 on success, negative value on error
Allows use of the vector registers introduced with z13 processor, and
provides for the synchronization between host and user space. Will
return -EINVAL if the machine does not support vectors.
7.4 KVM_CAP_S390_USER_STSI
+--------------------------
-Architectures: s390
-Parameters: none
+:Architectures: s390
+:Parameters: none
This capability allows post-handlers for the STSI instruction. After
initial handling in the kernel, KVM exits to user space with
KVM_EXIT_S390_STSI to allow user space to insert further data.
Before exiting to userspace, kvm handlers should fill in s390_stsi field of
-vcpu->run:
-struct {
+vcpu->run::
+
+ struct {
__u64 addr;
__u8 ar;
__u8 reserved;
__u8 fc;
__u8 sel1;
__u16 sel2;
-} s390_stsi;
+ } s390_stsi;
-@addr - guest address of STSI SYSIB
-@fc - function code
-@sel1 - selector 1
-@sel2 - selector 2
-@ar - access register number
+ @addr - guest address of STSI SYSIB
+ @fc - function code
+ @sel1 - selector 1
+ @sel2 - selector 2
+ @ar - access register number
KVM handlers should exit to userspace with rc = -EREMOTE.
7.5 KVM_CAP_SPLIT_IRQCHIP
+-------------------------
-Architectures: x86
-Parameters: args[0] - number of routes reserved for userspace IOAPICs
-Returns: 0 on success, -1 on error
+:Architectures: x86
+:Parameters: args[0] - number of routes reserved for userspace IOAPICs
+:Returns: 0 on success, -1 on error
Create a local apic for each processor in the kernel. This can be used
instead of KVM_CREATE_IRQCHIP if the userspace VMM wishes to emulate the
@@ -4864,24 +5737,26 @@
kernel (i.e. KVM_CREATE_IRQCHIP has already been called).
7.6 KVM_CAP_S390_RI
+-------------------
-Architectures: s390
-Parameters: none
+:Architectures: s390
+:Parameters: none
Allows use of runtime-instrumentation introduced with zEC12 processor.
Will return -EINVAL if the machine does not support runtime-instrumentation.
Will return -EBUSY if a VCPU has already been created.
7.7 KVM_CAP_X2APIC_API
+----------------------
-Architectures: x86
-Parameters: args[0] - features that should be enabled
-Returns: 0 on success, -EINVAL when args[0] contains invalid features
+:Architectures: x86
+:Parameters: args[0] - features that should be enabled
+:Returns: 0 on success, -EINVAL when args[0] contains invalid features
-Valid feature flags in args[0] are
+Valid feature flags in args[0] are::
-#define KVM_X2APIC_API_USE_32BIT_IDS (1ULL << 0)
-#define KVM_X2APIC_API_DISABLE_BROADCAST_QUIRK (1ULL << 1)
+ #define KVM_X2APIC_API_USE_32BIT_IDS (1ULL << 0)
+ #define KVM_X2APIC_API_DISABLE_BROADCAST_QUIRK (1ULL << 1)
Enabling KVM_X2APIC_API_USE_32BIT_IDS changes the behavior of
KVM_SET_GSI_ROUTING, KVM_SIGNAL_MSI, KVM_SET_LAPIC, and KVM_GET_LAPIC,
@@ -4895,9 +5770,10 @@
where 0xff represents CPUs 0-7 in cluster 0.
7.8 KVM_CAP_S390_USER_INSTR0
+----------------------------
-Architectures: s390
-Parameters: none
+:Architectures: s390
+:Parameters: none
With this capability enabled, all illegal instructions 0x0000 (2 bytes) will
be intercepted and forwarded to user space. User space can use this
@@ -4909,26 +5785,29 @@
created and are running.
7.9 KVM_CAP_S390_GS
+-------------------
-Architectures: s390
-Parameters: none
-Returns: 0 on success; -EINVAL if the machine does not support
- guarded storage; -EBUSY if a VCPU has already been created.
+:Architectures: s390
+:Parameters: none
+:Returns: 0 on success; -EINVAL if the machine does not support
+ guarded storage; -EBUSY if a VCPU has already been created.
Allows use of guarded storage for the KVM guest.
7.10 KVM_CAP_S390_AIS
+---------------------
-Architectures: s390
-Parameters: none
+:Architectures: s390
+:Parameters: none
Allow use of adapter-interruption suppression.
-Returns: 0 on success; -EBUSY if a VCPU has already been created.
+:Returns: 0 on success; -EBUSY if a VCPU has already been created.
7.11 KVM_CAP_PPC_SMT
+--------------------
-Architectures: ppc
-Parameters: vsmt_mode, flags
+:Architectures: ppc
+:Parameters: vsmt_mode, flags
Enabling this capability on a VM provides userspace with a way to set
the desired virtual SMT mode (i.e. the number of virtual CPUs per
@@ -4943,9 +5822,10 @@
modes are available.
7.12 KVM_CAP_PPC_FWNMI
+----------------------
-Architectures: ppc
-Parameters: none
+:Architectures: ppc
+:Parameters: none
With this capability a machine check exception in the guest address
space will cause KVM to exit the guest with NMI exit reason. This
@@ -4954,17 +5834,18 @@
branch to guests' 0x200 interrupt vector.
7.13 KVM_CAP_X86_DISABLE_EXITS
+------------------------------
-Architectures: x86
-Parameters: args[0] defines which exits are disabled
-Returns: 0 on success, -EINVAL when args[0] contains invalid exits
+:Architectures: x86
+:Parameters: args[0] defines which exits are disabled
+:Returns: 0 on success, -EINVAL when args[0] contains invalid exits
-Valid bits in args[0] are
+Valid bits in args[0] are::
-#define KVM_X86_DISABLE_EXITS_MWAIT (1 << 0)
-#define KVM_X86_DISABLE_EXITS_HLT (1 << 1)
-#define KVM_X86_DISABLE_EXITS_PAUSE (1 << 2)
-#define KVM_X86_DISABLE_EXITS_CSTATE (1 << 3)
+ #define KVM_X86_DISABLE_EXITS_MWAIT (1 << 0)
+ #define KVM_X86_DISABLE_EXITS_HLT (1 << 1)
+ #define KVM_X86_DISABLE_EXITS_PAUSE (1 << 2)
+ #define KVM_X86_DISABLE_EXITS_CSTATE (1 << 3)
Enabling this capability on a VM provides userspace with a way to no
longer intercept some instructions for improved latency in some
@@ -4976,12 +5857,13 @@
Do not enable KVM_FEATURE_PV_UNHALT if you disable HLT exits.
7.14 KVM_CAP_S390_HPAGE_1M
+--------------------------
-Architectures: s390
-Parameters: none
-Returns: 0 on success, -EINVAL if hpage module parameter was not set
- or cmma is enabled, or the VM has the KVM_VM_S390_UCONTROL
- flag set
+:Architectures: s390
+:Parameters: none
+:Returns: 0 on success, -EINVAL if hpage module parameter was not set
+ or cmma is enabled, or the VM has the KVM_VM_S390_UCONTROL
+ flag set
With this capability the KVM support for memory backing with 1m pages
through hugetlbfs can be enabled for a VM. After the capability is
@@ -4993,20 +5875,22 @@
this capability, the VM will not be able to run.
7.15 KVM_CAP_MSR_PLATFORM_INFO
+------------------------------
-Architectures: x86
-Parameters: args[0] whether feature should be enabled or not
+:Architectures: x86
+:Parameters: args[0] whether feature should be enabled or not
With this capability, a guest may read the MSR_PLATFORM_INFO MSR. Otherwise,
a #GP would be raised when the guest tries to access. Currently, this
capability does not enable write permissions of this MSR for the guest.
7.16 KVM_CAP_PPC_NESTED_HV
+--------------------------
-Architectures: ppc
-Parameters: none
-Returns: 0 on success, -EINVAL when the implementation doesn't support
- nested-HV virtualization.
+:Architectures: ppc
+:Parameters: none
+:Returns: 0 on success, -EINVAL when the implementation doesn't support
+ nested-HV virtualization.
HV-KVM on POWER9 and later systems allows for "nested-HV"
virtualization, which provides a way for a guest VM to run guests that
@@ -5016,9 +5900,10 @@
kvm-hv module parameter.
7.17 KVM_CAP_EXCEPTION_PAYLOAD
+------------------------------
-Architectures: x86
-Parameters: args[0] whether feature should be enabled or not
+:Architectures: x86
+:Parameters: args[0] whether feature should be enabled or not
With this capability enabled, CR2 will not be modified prior to the
emulated VM-exit when L1 intercepts a #PF exception that occurs in
@@ -5029,24 +5914,29 @@
faulting address (or the new DR6 bits*) will be reported in the
exception_payload field. Similarly, when userspace injects a #PF (or
#DB) into L2 using KVM_SET_VCPU_EVENTS, it is expected to set
-exception.has_payload and to put the faulting address (or the new DR6
-bits*) in the exception_payload field.
+exception.has_payload and to put the faulting address - or the new DR6
+bits\ [#]_ - in the exception_payload field.
This capability also enables exception.pending in struct
kvm_vcpu_events, which allows userspace to distinguish between pending
and injected exceptions.
-* For the new DR6 bits, note that bit 16 is set iff the #DB exception
- will clear DR6.RTM.
+.. [#] For the new DR6 bits, note that bit 16 is set iff the #DB exception
+ will clear DR6.RTM.
7.18 KVM_CAP_MANUAL_DIRTY_LOG_PROTECT2
-Architectures: x86, arm, arm64, mips
-Parameters: args[0] whether feature should be enabled or not
+:Architectures: x86, arm, arm64, mips
+:Parameters: args[0] whether feature should be enabled or not
-With this capability enabled, KVM_GET_DIRTY_LOG will not automatically
-clear and write-protect all pages that are returned as dirty.
+Valid flags are::
+
+ #define KVM_DIRTY_LOG_MANUAL_PROTECT_ENABLE (1 << 0)
+ #define KVM_DIRTY_LOG_INITIALLY_SET (1 << 1)
+
+With KVM_DIRTY_LOG_MANUAL_PROTECT_ENABLE is set, KVM_GET_DIRTY_LOG will not
+automatically clear and write-protect all pages that are returned as dirty.
Rather, userspace will have to do this operation separately using
KVM_CLEAR_DIRTY_LOG.
@@ -5057,39 +5947,105 @@
take spinlocks for an extended period of time. Second, in some cases a
large amount of time can pass between a call to KVM_GET_DIRTY_LOG and
userspace actually using the data in the page. Pages can be modified
-during this time, which is inefficint for both the guest and userspace:
+during this time, which is inefficient for both the guest and userspace:
the guest will incur a higher penalty due to write protection faults,
while userspace can see false reports of dirty pages. Manual reprotection
helps reducing this time, improving guest performance and reducing the
number of dirty log false positives.
+With KVM_DIRTY_LOG_INITIALLY_SET set, all the bits of the dirty bitmap
+will be initialized to 1 when created. This also improves performance because
+dirty logging can be enabled gradually in small chunks on the first call
+to KVM_CLEAR_DIRTY_LOG. KVM_DIRTY_LOG_INITIALLY_SET depends on
+KVM_DIRTY_LOG_MANUAL_PROTECT_ENABLE (it is also only available on
+x86 and arm64 for now).
+
KVM_CAP_MANUAL_DIRTY_LOG_PROTECT2 was previously available under the name
KVM_CAP_MANUAL_DIRTY_LOG_PROTECT, but the implementation had bugs that make
it hard or impossible to use it correctly. The availability of
KVM_CAP_MANUAL_DIRTY_LOG_PROTECT2 signals that those bugs are fixed.
Userspace should not try to use KVM_CAP_MANUAL_DIRTY_LOG_PROTECT.
-8. Other capabilities.
+7.19 KVM_CAP_PPC_SECURE_GUEST
+------------------------------
+
+:Architectures: ppc
+
+This capability indicates that KVM is running on a host that has
+ultravisor firmware and thus can support a secure guest. On such a
+system, a guest can ask the ultravisor to make it a secure guest,
+one whose memory is inaccessible to the host except for pages which
+are explicitly requested to be shared with the host. The ultravisor
+notifies KVM when a guest requests to become a secure guest, and KVM
+has the opportunity to veto the transition.
+
+If present, this capability can be enabled for a VM, meaning that KVM
+will allow the transition to secure guest mode. Otherwise KVM will
+veto the transition.
+
+7.20 KVM_CAP_HALT_POLL
----------------------
+:Architectures: all
+:Target: VM
+:Parameters: args[0] is the maximum poll time in nanoseconds
+:Returns: 0 on success; -1 on error
+
+This capability overrides the kvm module parameter halt_poll_ns for the
+target VM.
+
+VCPU polling allows a VCPU to poll for wakeup events instead of immediately
+scheduling during guest halts. The maximum time a VCPU can spend polling is
+controlled by the kvm module parameter halt_poll_ns. This capability allows
+the maximum halt time to specified on a per-VM basis, effectively overriding
+the module parameter for the target VM.
+
+7.21 KVM_CAP_X86_USER_SPACE_MSR
+-------------------------------
+
+:Architectures: x86
+:Target: VM
+:Parameters: args[0] contains the mask of KVM_MSR_EXIT_REASON_* events to report
+:Returns: 0 on success; -1 on error
+
+This capability enables trapping of #GP invoking RDMSR and WRMSR instructions
+into user space.
+
+When a guest requests to read or write an MSR, KVM may not implement all MSRs
+that are relevant to a respective system. It also does not differentiate by
+CPU type.
+
+To allow more fine grained control over MSR handling, user space may enable
+this capability. With it enabled, MSR accesses that match the mask specified in
+args[0] and trigger a #GP event inside the guest by KVM will instead trigger
+KVM_EXIT_X86_RDMSR and KVM_EXIT_X86_WRMSR exit notifications which user space
+can then handle to implement model specific MSR handling and/or user notifications
+to inform a user that an MSR was not handled.
+
+8. Other capabilities.
+======================
+
This section lists capabilities that give information about other
features of the KVM implementation.
8.1 KVM_CAP_PPC_HWRNG
+---------------------
-Architectures: ppc
+:Architectures: ppc
This capability, if KVM_CHECK_EXTENSION indicates that it is
-available, means that that the kernel has an implementation of the
+available, means that the kernel has an implementation of the
H_RANDOM hypercall backed by a hardware random-number generator.
If present, the kernel H_RANDOM handler can be enabled for guest use
with the KVM_CAP_PPC_ENABLE_HCALL capability.
8.2 KVM_CAP_HYPERV_SYNIC
+------------------------
-Architectures: x86
+:Architectures: x86
+
This capability, if KVM_CHECK_EXTENSION indicates that it is
-available, means that that the kernel has an implementation of the
+available, means that the kernel has an implementation of the
Hyper-V Synthetic interrupt controller(SynIC). Hyper-V SynIC is
used to support Windows Hyper-V based guest paravirt drivers(VMBus).
@@ -5099,26 +6055,29 @@
by the CPU, as it's incompatible with SynIC auto-EOI behavior.
8.3 KVM_CAP_PPC_RADIX_MMU
+-------------------------
-Architectures: ppc
+:Architectures: ppc
This capability, if KVM_CHECK_EXTENSION indicates that it is
-available, means that that the kernel can support guests using the
+available, means that the kernel can support guests using the
radix MMU defined in Power ISA V3.00 (as implemented in the POWER9
processor).
8.4 KVM_CAP_PPC_HASH_MMU_V3
+---------------------------
-Architectures: ppc
+:Architectures: ppc
This capability, if KVM_CHECK_EXTENSION indicates that it is
-available, means that that the kernel can support guests using the
+available, means that the kernel can support guests using the
hashed page table MMU defined in Power ISA V3.00 (as implemented in
the POWER9 processor), including in-memory segment tables.
8.5 KVM_CAP_MIPS_VZ
+-------------------
-Architectures: mips
+:Architectures: mips
This capability, if KVM_CHECK_EXTENSION on the main kvm handle indicates that
it is available, means that full hardware assisted virtualization capabilities
@@ -5136,16 +6095,19 @@
possibility of other hardware assisted virtualization implementations which
may be incompatible with the MIPS VZ ASE.
- 0: The trap & emulate implementation is in use to run guest code in user
+== ==========================================================================
+ 0 The trap & emulate implementation is in use to run guest code in user
mode. Guest virtual memory segments are rearranged to fit the guest in the
user mode address space.
- 1: The MIPS VZ ASE is in use, providing full hardware assisted
+ 1 The MIPS VZ ASE is in use, providing full hardware assisted
virtualization, including standard guest virtual memory segments.
+== ==========================================================================
8.6 KVM_CAP_MIPS_TE
+-------------------
-Architectures: mips
+:Architectures: mips
This capability, if KVM_CHECK_EXTENSION on the main kvm handle indicates that
it is available, means that the trap & emulate implementation is available to
@@ -5157,8 +6119,9 @@
available, it means that the VM is using trap & emulate.
8.7 KVM_CAP_MIPS_64BIT
+----------------------
-Architectures: mips
+:Architectures: mips
This capability indicates the supported architecture type of the guest, i.e. the
supported register and address width.
@@ -5168,22 +6131,26 @@
be checked specifically against known values (see below). All other values are
reserved.
- 0: MIPS32 or microMIPS32.
+== ========================================================================
+ 0 MIPS32 or microMIPS32.
Both registers and addresses are 32-bits wide.
It will only be possible to run 32-bit guest code.
- 1: MIPS64 or microMIPS64 with access only to 32-bit compatibility segments.
+ 1 MIPS64 or microMIPS64 with access only to 32-bit compatibility segments.
Registers are 64-bits wide, but addresses are 32-bits wide.
64-bit guest code may run but cannot access MIPS64 memory segments.
It will also be possible to run 32-bit guest code.
- 2: MIPS64 or microMIPS64 with access to all address segments.
+ 2 MIPS64 or microMIPS64 with access to all address segments.
Both registers and addresses are 64-bits wide.
It will be possible to run 64-bit or 32-bit guest code.
+== ========================================================================
8.9 KVM_CAP_ARM_USER_IRQ
+------------------------
-Architectures: arm, arm64
+:Architectures: arm, arm64
+
This capability, if KVM_CHECK_EXTENSION indicates that it is available, means
that if userspace creates a VM without an in-kernel interrupt controller, it
will be notified of changes to the output level of in-kernel emulated devices,
@@ -5208,9 +6175,9 @@
If KVM_CAP_ARM_USER_IRQ is supported, the KVM_CHECK_EXTENSION ioctl returns a
number larger than 0 indicating the version of this capability is implemented
-and thereby which bits in in run->s.regs.device_irq_level can signal values.
+and thereby which bits in run->s.regs.device_irq_level can signal values.
-Currently the following bits are defined for the device_irq_level bitmap:
+Currently the following bits are defined for the device_irq_level bitmap::
KVM_CAP_ARM_USER_IRQ >= 1:
@@ -5223,8 +6190,9 @@
listed above.
8.10 KVM_CAP_PPC_SMT_POSSIBLE
+-----------------------------
-Architectures: ppc
+:Architectures: ppc
Querying this capability returns a bitmap indicating the possible
virtual SMT modes that can be set using KVM_CAP_PPC_SMT. If bit N
@@ -5232,8 +6200,9 @@
available.
8.11 KVM_CAP_HYPERV_SYNIC2
+--------------------------
-Architectures: x86
+:Architectures: x86
This capability enables a newer version of Hyper-V Synthetic interrupt
controller (SynIC). The only difference with KVM_CAP_HYPERV_SYNIC is that KVM
@@ -5241,8 +6210,9 @@
writing to the respective MSRs.
8.12 KVM_CAP_HYPERV_VP_INDEX
+----------------------------
-Architectures: x86
+:Architectures: x86
This capability indicates that userspace can load HV_X64_MSR_VP_INDEX msr. Its
value is used to denote the target vcpu for a SynIC interrupt. For
@@ -5250,47 +6220,53 @@
capability is absent, userspace can still query this msr's value.
8.13 KVM_CAP_S390_AIS_MIGRATION
+-------------------------------
-Architectures: s390
-Parameters: none
+:Architectures: s390
+:Parameters: none
This capability indicates if the flic device will be able to get/set the
AIS states for migration via the KVM_DEV_FLIC_AISM_ALL attribute and allows
to discover this without having to create a flic device.
8.14 KVM_CAP_S390_PSW
+---------------------
-Architectures: s390
+:Architectures: s390
This capability indicates that the PSW is exposed via the kvm_run structure.
8.15 KVM_CAP_S390_GMAP
+----------------------
-Architectures: s390
+:Architectures: s390
This capability indicates that the user space memory used as guest mapping can
be anywhere in the user memory address space, as long as the memory slots are
aligned and sized to a segment (1MB) boundary.
8.16 KVM_CAP_S390_COW
+---------------------
-Architectures: s390
+:Architectures: s390
This capability indicates that the user space memory used as guest mapping can
use copy-on-write semantics as well as dirty pages tracking via read-only page
tables.
8.17 KVM_CAP_S390_BPB
+---------------------
-Architectures: s390
+:Architectures: s390
This capability indicates that kvm will implement the interfaces to handle
reset, migration and nested KVM for branch prediction blocking. The stfle
facility 82 should not be provided to the guest without this capability.
8.18 KVM_CAP_HYPERV_TLBFLUSH
+----------------------------
-Architectures: x86
+:Architectures: x86
This capability indicates that KVM supports paravirtualized Hyper-V TLB Flush
hypercalls:
@@ -5298,8 +6274,9 @@
HvFlushVirtualAddressList, HvFlushVirtualAddressListEx.
8.19 KVM_CAP_ARM_INJECT_SERROR_ESR
+----------------------------------
-Architectures: arm, arm64
+:Architectures: arm, arm64
This capability indicates that userspace can specify (via the
KVM_SET_VCPU_EVENTS ioctl) the syndrome value reported to the guest when it
@@ -5310,16 +6287,20 @@
AArch64, this value will be reported in the ISS field of ESR_ELx.
See KVM_CAP_VCPU_EVENTS for more details.
-8.20 KVM_CAP_HYPERV_SEND_IPI
-Architectures: x86
+8.20 KVM_CAP_HYPERV_SEND_IPI
+----------------------------
+
+:Architectures: x86
This capability indicates that KVM supports paravirtualized Hyper-V IPI send
hypercalls:
HvCallSendSyntheticClusterIpi, HvCallSendSyntheticClusterIpiEx.
-8.21 KVM_CAP_HYPERV_DIRECT_TLBFLUSH
-Architecture: x86
+8.21 KVM_CAP_HYPERV_DIRECT_TLBFLUSH
+-----------------------------------
+
+:Architectures: x86
This capability indicates that KVM running on top of Hyper-V hypervisor
enables Direct TLB flush for its guests meaning that TLB flush
@@ -5330,3 +6311,90 @@
flush hypercalls by Hyper-V) so userspace should disable KVM identification
in CPUID and only exposes Hyper-V identification. In this case, guest
thinks it's running on Hyper-V and only use Hyper-V hypercalls.
+
+8.22 KVM_CAP_S390_VCPU_RESETS
+-----------------------------
+
+:Architectures: s390
+
+This capability indicates that the KVM_S390_NORMAL_RESET and
+KVM_S390_CLEAR_RESET ioctls are available.
+
+8.23 KVM_CAP_S390_PROTECTED
+---------------------------
+
+:Architectures: s390
+
+This capability indicates that the Ultravisor has been initialized and
+KVM can therefore start protected VMs.
+This capability governs the KVM_S390_PV_COMMAND ioctl and the
+KVM_MP_STATE_LOAD MP_STATE. KVM_SET_MP_STATE can fail for protected
+guests when the state change is invalid.
+
+8.24 KVM_CAP_STEAL_TIME
+-----------------------
+
+:Architectures: arm64, x86
+
+This capability indicates that KVM supports steal time accounting.
+When steal time accounting is supported it may be enabled with
+architecture-specific interfaces. This capability and the architecture-
+specific interfaces must be consistent, i.e. if one says the feature
+is supported, than the other should as well and vice versa. For arm64
+see Documentation/virt/kvm/devices/vcpu.rst "KVM_ARM_VCPU_PVTIME_CTRL".
+For x86 see Documentation/virt/kvm/msr.rst "MSR_KVM_STEAL_TIME".
+
+8.25 KVM_CAP_S390_DIAG318
+-------------------------
+
+:Architectures: s390
+
+This capability enables a guest to set information about its control program
+(i.e. guest kernel type and version). The information is helpful during
+system/firmware service events, providing additional data about the guest
+environments running on the machine.
+
+The information is associated with the DIAGNOSE 0x318 instruction, which sets
+an 8-byte value consisting of a one-byte Control Program Name Code (CPNC) and
+a 7-byte Control Program Version Code (CPVC). The CPNC determines what
+environment the control program is running in (e.g. Linux, z/VM...), and the
+CPVC is used for information specific to OS (e.g. Linux version, Linux
+distribution...)
+
+If this capability is available, then the CPNC and CPVC can be synchronized
+between KVM and userspace via the sync regs mechanism (KVM_SYNC_DIAG318).
+
+8.26 KVM_CAP_X86_USER_SPACE_MSR
+-------------------------------
+
+:Architectures: x86
+
+This capability indicates that KVM supports deflection of MSR reads and
+writes to user space. It can be enabled on a VM level. If enabled, MSR
+accesses that would usually trigger a #GP by KVM into the guest will
+instead get bounced to user space through the KVM_EXIT_X86_RDMSR and
+KVM_EXIT_X86_WRMSR exit notifications.
+
+8.27 KVM_X86_SET_MSR_FILTER
+---------------------------
+
+:Architectures: x86
+
+This capability indicates that KVM supports that accesses to user defined MSRs
+may be rejected. With this capability exposed, KVM exports new VM ioctl
+KVM_X86_SET_MSR_FILTER which user space can call to specify bitmaps of MSR
+ranges that KVM should reject access to.
+
+In combination with KVM_CAP_X86_USER_SPACE_MSR, this allows user space to
+trap and emulate MSRs that are outside of the scope of KVM as well as
+limit the attack surface on KVM's MSR emulation code.
+
+8.28 KVM_CAP_ENFORCE_PV_CPUID
+-----------------------------
+
+Architectures: x86
+
+When enabled, KVM will disable paravirtual features provided to the
+guest according to the bits in the KVM_CPUID_FEATURES CPUID leaf
+(0x40000001). Otherwise, a guest may use the paravirtual features
+regardless of what has actually been exposed through the CPUID leaf.
diff --git a/Documentation/virt/kvm/arm/hyp-abi.txt b/Documentation/virt/kvm/arm/hyp-abi.rst
similarity index 64%
rename from Documentation/virt/kvm/arm/hyp-abi.txt
rename to Documentation/virt/kvm/arm/hyp-abi.rst
index a20a0be..83cadd8 100644
--- a/Documentation/virt/kvm/arm/hyp-abi.txt
+++ b/Documentation/virt/kvm/arm/hyp-abi.rst
@@ -1,4 +1,8 @@
-* Internal ABI between the kernel and HYP
+.. SPDX-License-Identifier: GPL-2.0
+
+=======================================
+Internal ABI between the kernel and HYP
+=======================================
This file documents the interaction between the Linux kernel and the
hypervisor layer when running Linux as a hypervisor (for example
@@ -7,6 +11,11 @@
hypervisor), or any hypervisor-specific interaction when the kernel is
used as a host.
+Note: KVM/arm has been removed from the kernel. The API described
+here is still valid though, as it allows the kernel to kexec when
+booted at HYP. It can also be used by a hypervisor other than KVM
+if necessary.
+
On arm and arm64 (without VHE), the kernel doesn't run in hypervisor
mode, but still needs to interact with it, allowing a built-in
hypervisor to be either installed or torn down.
@@ -19,29 +28,35 @@
Unless specified otherwise, any built-in hypervisor must implement
these functions (see arch/arm{,64}/include/asm/virt.h):
-* r0/x0 = HVC_SET_VECTORS
- r1/x1 = vectors
+* ::
+
+ r0/x0 = HVC_SET_VECTORS
+ r1/x1 = vectors
Set HVBAR/VBAR_EL2 to 'vectors' to enable a hypervisor. 'vectors'
must be a physical address, and respect the alignment requirements
of the architecture. Only implemented by the initial stubs, not by
Linux hypervisors.
-* r0/x0 = HVC_RESET_VECTORS
+* ::
+
+ r0/x0 = HVC_RESET_VECTORS
Turn HYP/EL2 MMU off, and reset HVBAR/VBAR_EL2 to the initials
stubs' exception vector value. This effectively disables an existing
hypervisor.
-* r0/x0 = HVC_SOFT_RESTART
- r1/x1 = restart address
- x2 = x0's value when entering the next payload (arm64)
- x3 = x1's value when entering the next payload (arm64)
- x4 = x2's value when entering the next payload (arm64)
+* ::
- Mask all exceptions, disable the MMU, move the arguments into place
- (arm64 only), and jump to the restart address while at HYP/EL2. This
- hypercall is not expected to return to its caller.
+ r0/x0 = HVC_SOFT_RESTART
+ r1/x1 = restart address
+ x2 = x0's value when entering the next payload (arm64)
+ x3 = x1's value when entering the next payload (arm64)
+ x4 = x2's value when entering the next payload (arm64)
+
+ Mask all exceptions, disable the MMU, clear I+D bits, move the arguments
+ into place (arm64 only), and jump to the restart address while at HYP/EL2.
+ This hypercall is not expected to return to its caller.
Any other value of r0/x0 triggers a hypervisor-specific handling,
which is not documented here.
diff --git a/Documentation/virt/kvm/arm/index.rst b/Documentation/virt/kvm/arm/index.rst
new file mode 100644
index 0000000..3e2b2ab
--- /dev/null
+++ b/Documentation/virt/kvm/arm/index.rst
@@ -0,0 +1,12 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+===
+ARM
+===
+
+.. toctree::
+ :maxdepth: 2
+
+ hyp-abi
+ psci
+ pvtime
diff --git a/Documentation/virt/kvm/arm/psci.txt b/Documentation/virt/kvm/arm/psci.rst
similarity index 60%
rename from Documentation/virt/kvm/arm/psci.txt
rename to Documentation/virt/kvm/arm/psci.rst
index 559586f..d52c2e8 100644
--- a/Documentation/virt/kvm/arm/psci.txt
+++ b/Documentation/virt/kvm/arm/psci.rst
@@ -1,3 +1,9 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+=========================================
+Power State Coordination Interface (PSCI)
+=========================================
+
KVM implements the PSCI (Power State Coordination Interface)
specification in order to provide services such as CPU on/off, reset
and power-off to the guest.
@@ -30,32 +36,42 @@
- Affects the whole VM (even if the register view is per-vcpu)
* KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_1:
- Holds the state of the firmware support to mitigate CVE-2017-5715, as
- offered by KVM to the guest via a HVC call. The workaround is described
- under SMCCC_ARCH_WORKAROUND_1 in [1].
+ Holds the state of the firmware support to mitigate CVE-2017-5715, as
+ offered by KVM to the guest via a HVC call. The workaround is described
+ under SMCCC_ARCH_WORKAROUND_1 in [1].
+
Accepted values are:
- KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_1_NOT_AVAIL: KVM does not offer
+
+ KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_1_NOT_AVAIL:
+ KVM does not offer
firmware support for the workaround. The mitigation status for the
guest is unknown.
- KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_1_AVAIL: The workaround HVC call is
+ KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_1_AVAIL:
+ The workaround HVC call is
available to the guest and required for the mitigation.
- KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_1_NOT_REQUIRED: The workaround HVC call
+ KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_1_NOT_REQUIRED:
+ The workaround HVC call
is available to the guest, but it is not needed on this VCPU.
* KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2:
- Holds the state of the firmware support to mitigate CVE-2018-3639, as
- offered by KVM to the guest via a HVC call. The workaround is described
- under SMCCC_ARCH_WORKAROUND_2 in [1].
+ Holds the state of the firmware support to mitigate CVE-2018-3639, as
+ offered by KVM to the guest via a HVC call. The workaround is described
+ under SMCCC_ARCH_WORKAROUND_2 in [1]_.
+
Accepted values are:
- KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_NOT_AVAIL: A workaround is not
+
+ KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_NOT_AVAIL:
+ A workaround is not
available. KVM does not offer firmware support for the workaround.
- KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_UNKNOWN: The workaround state is
+ KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_UNKNOWN:
+ The workaround state is
unknown. KVM does not offer firmware support for the workaround.
- KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_AVAIL: The workaround is available,
+ KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_AVAIL:
+ The workaround is available,
and can be disabled by a vCPU. If
KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_ENABLED is set, it is active for
this vCPU.
- KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_NOT_REQUIRED: The workaround is
- always active on this vCPU or it is not needed.
+ KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_NOT_REQUIRED:
+ The workaround is always active on this vCPU or it is not needed.
-[1] https://developer.arm.com/-/media/developer/pdf/ARM_DEN_0070A_Firmware_interfaces_for_mitigating_CVE-2017-5715.pdf
+.. [1] https://developer.arm.com/-/media/developer/pdf/ARM_DEN_0070A_Firmware_interfaces_for_mitigating_CVE-2017-5715.pdf
diff --git a/Documentation/virt/kvm/arm/pvtime.rst b/Documentation/virt/kvm/arm/pvtime.rst
new file mode 100644
index 0000000..687b60d
--- /dev/null
+++ b/Documentation/virt/kvm/arm/pvtime.rst
@@ -0,0 +1,80 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+Paravirtualized time support for arm64
+======================================
+
+Arm specification DEN0057/A defines a standard for paravirtualised time
+support for AArch64 guests:
+
+https://developer.arm.com/docs/den0057/a
+
+KVM/arm64 implements the stolen time part of this specification by providing
+some hypervisor service calls to support a paravirtualized guest obtaining a
+view of the amount of time stolen from its execution.
+
+Two new SMCCC compatible hypercalls are defined:
+
+* PV_TIME_FEATURES: 0xC5000020
+* PV_TIME_ST: 0xC5000021
+
+These are only available in the SMC64/HVC64 calling convention as
+paravirtualized time is not available to 32 bit Arm guests. The existence of
+the PV_FEATURES hypercall should be probed using the SMCCC 1.1 ARCH_FEATURES
+mechanism before calling it.
+
+PV_TIME_FEATURES
+ ============= ======== ==========
+ Function ID: (uint32) 0xC5000020
+ PV_call_id: (uint32) The function to query for support.
+ Currently only PV_TIME_ST is supported.
+ Return value: (int64) NOT_SUPPORTED (-1) or SUCCESS (0) if the relevant
+ PV-time feature is supported by the hypervisor.
+ ============= ======== ==========
+
+PV_TIME_ST
+ ============= ======== ==========
+ Function ID: (uint32) 0xC5000021
+ Return value: (int64) IPA of the stolen time data structure for this
+ VCPU. On failure:
+ NOT_SUPPORTED (-1)
+ ============= ======== ==========
+
+The IPA returned by PV_TIME_ST should be mapped by the guest as normal memory
+with inner and outer write back caching attributes, in the inner shareable
+domain. A total of 16 bytes from the IPA returned are guaranteed to be
+meaningfully filled by the hypervisor (see structure below).
+
+PV_TIME_ST returns the structure for the calling VCPU.
+
+Stolen Time
+-----------
+
+The structure pointed to by the PV_TIME_ST hypercall is as follows:
+
++-------------+-------------+-------------+----------------------------+
+| Field | Byte Length | Byte Offset | Description |
++=============+=============+=============+============================+
+| Revision | 4 | 0 | Must be 0 for version 1.0 |
++-------------+-------------+-------------+----------------------------+
+| Attributes | 4 | 4 | Must be 0 |
++-------------+-------------+-------------+----------------------------+
+| Stolen time | 8 | 8 | Stolen time in unsigned |
+| | | | nanoseconds indicating how |
+| | | | much time this VCPU thread |
+| | | | was involuntarily not |
+| | | | running on a physical CPU. |
++-------------+-------------+-------------+----------------------------+
+
+All values in the structure are stored little-endian.
+
+The structure will be updated by the hypervisor prior to scheduling a VCPU. It
+will be present within a reserved region of the normal memory given to the
+guest. The guest should not attempt to write into this memory. There is a
+structure per VCPU of the guest.
+
+It is advisable that one or more 64k pages are set aside for the purpose of
+these structures and not used for other purposes, this enables the guest to map
+the region using 64k pages and avoids conflicting attributes with other memory.
+
+For the user space interface see Documentation/virt/kvm/devices/vcpu.rst
+section "3. GROUP: KVM_ARM_VCPU_PVTIME_CTRL".
diff --git a/Documentation/virt/kvm/cpuid.rst b/Documentation/virt/kvm/cpuid.rst
index 01b081f..cf62162 100644
--- a/Documentation/virt/kvm/cpuid.rst
+++ b/Documentation/virt/kvm/cpuid.rst
@@ -38,58 +38,68 @@
where ``flag`` is defined as below:
-================================= =========== ================================
-flag value meaning
-================================= =========== ================================
-KVM_FEATURE_CLOCKSOURCE 0 kvmclock available at msrs
- 0x11 and 0x12
+================================== =========== ================================
+flag value meaning
+================================== =========== ================================
+KVM_FEATURE_CLOCKSOURCE 0 kvmclock available at msrs
+ 0x11 and 0x12
-KVM_FEATURE_NOP_IO_DELAY 1 not necessary to perform delays
- on PIO operations
+KVM_FEATURE_NOP_IO_DELAY 1 not necessary to perform delays
+ on PIO operations
-KVM_FEATURE_MMU_OP 2 deprecated
+KVM_FEATURE_MMU_OP 2 deprecated
-KVM_FEATURE_CLOCKSOURCE2 3 kvmclock available at msrs
+KVM_FEATURE_CLOCKSOURCE2 3 kvmclock available at msrs
+ 0x4b564d00 and 0x4b564d01
- 0x4b564d00 and 0x4b564d01
-KVM_FEATURE_ASYNC_PF 4 async pf can be enabled by
- writing to msr 0x4b564d02
+KVM_FEATURE_ASYNC_PF 4 async pf can be enabled by
+ writing to msr 0x4b564d02
-KVM_FEATURE_STEAL_TIME 5 steal time can be enabled by
- writing to msr 0x4b564d03
+KVM_FEATURE_STEAL_TIME 5 steal time can be enabled by
+ writing to msr 0x4b564d03
-KVM_FEATURE_PV_EOI 6 paravirtualized end of interrupt
- handler can be enabled by
- writing to msr 0x4b564d04
+KVM_FEATURE_PV_EOI 6 paravirtualized end of interrupt
+ handler can be enabled by
+ writing to msr 0x4b564d04
-KVM_FEATURE_PV_UNHAULT 7 guest checks this feature bit
- before enabling paravirtualized
- spinlock support
+KVM_FEATURE_PV_UNHALT 7 guest checks this feature bit
+ before enabling paravirtualized
+ spinlock support
-KVM_FEATURE_PV_TLB_FLUSH 9 guest checks this feature bit
- before enabling paravirtualized
- tlb flush
+KVM_FEATURE_PV_TLB_FLUSH 9 guest checks this feature bit
+ before enabling paravirtualized
+ tlb flush
-KVM_FEATURE_ASYNC_PF_VMEXIT 10 paravirtualized async PF VM EXIT
- can be enabled by setting bit 2
- when writing to msr 0x4b564d02
+KVM_FEATURE_ASYNC_PF_VMEXIT 10 paravirtualized async PF VM EXIT
+ can be enabled by setting bit 2
+ when writing to msr 0x4b564d02
-KVM_FEATURE_PV_SEND_IPI 11 guest checks this feature bit
- before enabling paravirtualized
- sebd IPIs
+KVM_FEATURE_PV_SEND_IPI 11 guest checks this feature bit
+ before enabling paravirtualized
+ send IPIs
-KVM_FEATURE_PV_POLL_CONTROL 12 host-side polling on HLT can
- be disabled by writing
- to msr 0x4b564d05.
+KVM_FEATURE_POLL_CONTROL 12 host-side polling on HLT can
+ be disabled by writing
+ to msr 0x4b564d05.
-KVM_FEATURE_PV_SCHED_YIELD 13 guest checks this feature bit
- before using paravirtualized
- sched yield.
+KVM_FEATURE_PV_SCHED_YIELD 13 guest checks this feature bit
+ before using paravirtualized
+ sched yield.
-KVM_FEATURE_CLOCSOURCE_STABLE_BIT 24 host will warn if no guest-side
- per-cpu warps are expeced in
- kvmclock
-================================= =========== ================================
+KVM_FEATURE_ASYNC_PF_INT 14 guest checks this feature bit
+ before using the second async
+ pf control msr 0x4b564d06 and
+ async pf acknowledgment msr
+ 0x4b564d07.
+
+KVM_FEATURE_MSI_EXT_DEST_ID 15 guest checks this feature bit
+ before using extended destination
+ ID bits in MSI address bits 11-5.
+
+KVM_FEATURE_CLOCKSOURCE_STABLE_BIT 24 host will warn if no guest-side
+ per-cpu warps are expected in
+ kvmclock
+================================== =========== ================================
::
diff --git a/Documentation/virt/kvm/devices/arm-vgic-its.txt b/Documentation/virt/kvm/devices/arm-vgic-its.rst
similarity index 71%
rename from Documentation/virt/kvm/devices/arm-vgic-its.txt
rename to Documentation/virt/kvm/devices/arm-vgic-its.rst
index eeaa95b..6c304fd 100644
--- a/Documentation/virt/kvm/devices/arm-vgic-its.txt
+++ b/Documentation/virt/kvm/devices/arm-vgic-its.rst
@@ -1,3 +1,6 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+===============================================
ARM Virtual Interrupt Translation Service (ITS)
===============================================
@@ -12,22 +15,32 @@
a separate, non-overlapping MMIO region.
-Groups:
- KVM_DEV_ARM_VGIC_GRP_ADDR
+Groups
+======
+
+KVM_DEV_ARM_VGIC_GRP_ADDR
+-------------------------
+
Attributes:
KVM_VGIC_ITS_ADDR_TYPE (rw, 64-bit)
Base address in the guest physical address space of the GICv3 ITS
control register frame.
This address needs to be 64K aligned and the region covers 128K.
+
Errors:
- -E2BIG: Address outside of addressable IPA range
- -EINVAL: Incorrectly aligned address
- -EEXIST: Address already configured
- -EFAULT: Invalid user pointer for attr->addr.
- -ENODEV: Incorrect attribute or the ITS is not supported.
+
+ ======= =================================================
+ -E2BIG Address outside of addressable IPA range
+ -EINVAL Incorrectly aligned address
+ -EEXIST Address already configured
+ -EFAULT Invalid user pointer for attr->addr.
+ -ENODEV Incorrect attribute or the ITS is not supported.
+ ======= =================================================
- KVM_DEV_ARM_VGIC_GRP_CTRL
+KVM_DEV_ARM_VGIC_GRP_CTRL
+-------------------------
+
Attributes:
KVM_DEV_ARM_VGIC_CTRL_INIT
request the initialization of the ITS, no additional parameter in
@@ -58,16 +71,21 @@
"ITS Restore Sequence".
Errors:
- -ENXIO: ITS not properly configured as required prior to setting
- this attribute
- -ENOMEM: Memory shortage when allocating ITS internal data
- -EINVAL: Inconsistent restored data
- -EFAULT: Invalid guest ram access
- -EBUSY: One or more VCPUS are running
- -EACCES: The virtual ITS is backed by a physical GICv4 ITS, and the
- state is not available
- KVM_DEV_ARM_VGIC_GRP_ITS_REGS
+ ======= ==========================================================
+ -ENXIO ITS not properly configured as required prior to setting
+ this attribute
+ -ENOMEM Memory shortage when allocating ITS internal data
+ -EINVAL Inconsistent restored data
+ -EFAULT Invalid guest ram access
+ -EBUSY One or more VCPUS are running
+ -EACCES The virtual ITS is backed by a physical GICv4 ITS, and the
+ state is not available
+ ======= ==========================================================
+
+KVM_DEV_ARM_VGIC_GRP_ITS_REGS
+-----------------------------
+
Attributes:
The attr field of kvm_device_attr encodes the offset of the
ITS register, relative to the ITS control frame base address
@@ -78,6 +96,7 @@
be accessed with full length.
Writes to read-only registers are ignored by the kernel except for:
+
- GITS_CREADR. It must be restored otherwise commands in the queue
will be re-executed after restoring CWRITER. GITS_CREADR must be
restored before restoring the GITS_CTLR which is likely to enable the
@@ -91,30 +110,36 @@
For other registers, getting or setting a register has the same
effect as reading/writing the register on real hardware.
- Errors:
- -ENXIO: Offset does not correspond to any supported register
- -EFAULT: Invalid user pointer for attr->addr
- -EINVAL: Offset is not 64-bit aligned
- -EBUSY: one or more VCPUS are running
- ITS Restore Sequence:
- -------------------------
+ Errors:
+
+ ======= ====================================================
+ -ENXIO Offset does not correspond to any supported register
+ -EFAULT Invalid user pointer for attr->addr
+ -EINVAL Offset is not 64-bit aligned
+ -EBUSY one or more VCPUS are running
+ ======= ====================================================
+
+ITS Restore Sequence:
+---------------------
The following ordering must be followed when restoring the GIC and the ITS:
+
a) restore all guest memory and create vcpus
b) restore all redistributors
c) provide the ITS base address
(KVM_DEV_ARM_VGIC_GRP_ADDR)
d) restore the ITS in the following order:
- 1. Restore GITS_CBASER
- 2. Restore all other GITS_ registers, except GITS_CTLR!
- 3. Load the ITS table data (KVM_DEV_ARM_ITS_RESTORE_TABLES)
- 4. Restore GITS_CTLR
+
+ 1. Restore GITS_CBASER
+ 2. Restore all other ``GITS_`` registers, except GITS_CTLR!
+ 3. Load the ITS table data (KVM_DEV_ARM_ITS_RESTORE_TABLES)
+ 4. Restore GITS_CTLR
Then vcpus can be started.
- ITS Table ABI REV0:
- -------------------
+ITS Table ABI REV0:
+-------------------
Revision 0 of the ABI only supports the features of a virtual GICv3, and does
not support a virtual GICv4 with support for direct injection of virtual
@@ -125,12 +150,13 @@
entries in the collection are listed in no particular order.
All entries are 8 bytes.
- Device Table Entry (DTE):
+ Device Table Entry (DTE)::
- bits: | 63| 62 ... 49 | 48 ... 5 | 4 ... 0 |
- values: | V | next | ITT_addr | Size |
+ bits: | 63| 62 ... 49 | 48 ... 5 | 4 ... 0 |
+ values: | V | next | ITT_addr | Size |
- where;
+ where:
+
- V indicates whether the entry is valid. If not, other fields
are not meaningful.
- next: equals to 0 if this entry is the last one; otherwise it
@@ -140,32 +166,34 @@
- Size specifies the supported number of bits for the EventID,
minus one
- Collection Table Entry (CTE):
+ Collection Table Entry (CTE)::
- bits: | 63| 62 .. 52 | 51 ... 16 | 15 ... 0 |
- values: | V | RES0 | RDBase | ICID |
+ bits: | 63| 62 .. 52 | 51 ... 16 | 15 ... 0 |
+ values: | V | RES0 | RDBase | ICID |
where:
+
- V indicates whether the entry is valid. If not, other fields are
not meaningful.
- RES0: reserved field with Should-Be-Zero-or-Preserved behavior.
- RDBase is the PE number (GICR_TYPER.Processor_Number semantic),
- ICID is the collection ID
- Interrupt Translation Entry (ITE):
+ Interrupt Translation Entry (ITE)::
- bits: | 63 ... 48 | 47 ... 16 | 15 ... 0 |
- values: | next | pINTID | ICID |
+ bits: | 63 ... 48 | 47 ... 16 | 15 ... 0 |
+ values: | next | pINTID | ICID |
where:
+
- next: equals to 0 if this entry is the last one; otherwise it corresponds
to the EventID offset to the next ITE capped by 2^16 -1.
- pINTID is the physical LPI ID; if zero, it means the entry is not valid
and other fields are not meaningful.
- ICID is the collection ID
- ITS Reset State:
- ----------------
+ITS Reset State:
+----------------
RESET returns the ITS to the same state that it was when first created and
initialized. When the RESET command returns, the following things are
diff --git a/Documentation/virt/kvm/devices/arm-vgic-v3.txt b/Documentation/virt/kvm/devices/arm-vgic-v3.rst
similarity index 76%
rename from Documentation/virt/kvm/devices/arm-vgic-v3.txt
rename to Documentation/virt/kvm/devices/arm-vgic-v3.rst
index ff290b4..5dd3bff 100644
--- a/Documentation/virt/kvm/devices/arm-vgic-v3.txt
+++ b/Documentation/virt/kvm/devices/arm-vgic-v3.rst
@@ -1,9 +1,12 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+==============================================================
ARM Virtual Generic Interrupt Controller v3 and later (VGICv3)
==============================================================
Device types supported:
- KVM_DEV_TYPE_ARM_VGIC_V3 ARM Generic Interrupt Controller v3.0
+ - KVM_DEV_TYPE_ARM_VGIC_V3 ARM Generic Interrupt Controller v3.0
Only one VGIC instance may be instantiated through this API. The created VGIC
will act as the VM interrupt controller, requiring emulated user-space devices
@@ -15,7 +18,8 @@
Groups:
KVM_DEV_ARM_VGIC_GRP_ADDR
- Attributes:
+ Attributes:
+
KVM_VGIC_V3_ADDR_TYPE_DIST (rw, 64-bit)
Base address in the guest physical address space of the GICv3 distributor
register mappings. Only valid for KVM_DEV_TYPE_ARM_VGIC_V3.
@@ -29,21 +33,25 @@
This address needs to be 64K aligned.
KVM_VGIC_V3_ADDR_TYPE_REDIST_REGION (rw, 64-bit)
- The attribute data pointed to by kvm_device_attr.addr is a __u64 value:
- bits: | 63 .... 52 | 51 .... 16 | 15 - 12 |11 - 0
- values: | count | base | flags | index
+ The attribute data pointed to by kvm_device_attr.addr is a __u64 value::
+
+ bits: | 63 .... 52 | 51 .... 16 | 15 - 12 |11 - 0
+ values: | count | base | flags | index
+
- index encodes the unique redistributor region index
- flags: reserved for future use, currently 0
- base field encodes bits [51:16] of the guest physical base address
of the first redistributor in the region.
- count encodes the number of redistributors in the region. Must be
greater than 0.
+
There are two 64K pages for each redistributor in the region and
redistributors are laid out contiguously within the region. Regions
are filled with redistributors in the index order. The sum of all
region count fields must be greater than or equal to the number of
VCPUs. Redistributor regions must be registered in the incremental
index order, starting from index 0.
+
The characteristics of a specific redistributor region can be read
by presetting the index field in the attr data.
Only valid for KVM_DEV_TYPE_ARM_VGIC_V3.
@@ -52,23 +60,27 @@
KVM_VGIC_V3_ADDR_TYPE_REDIST_REGION attributes.
Errors:
- -E2BIG: Address outside of addressable IPA range
- -EINVAL: Incorrectly aligned address, bad redistributor region
+
+ ======= =============================================================
+ -E2BIG Address outside of addressable IPA range
+ -EINVAL Incorrectly aligned address, bad redistributor region
count/index, mixed redistributor region attribute usage
- -EEXIST: Address already configured
- -ENOENT: Attempt to read the characteristics of a non existing
+ -EEXIST Address already configured
+ -ENOENT Attempt to read the characteristics of a non existing
redistributor region
- -ENXIO: The group or attribute is unknown/unsupported for this device
+ -ENXIO The group or attribute is unknown/unsupported for this device
or hardware support is missing.
- -EFAULT: Invalid user pointer for attr->addr.
+ -EFAULT Invalid user pointer for attr->addr.
+ ======= =============================================================
- KVM_DEV_ARM_VGIC_GRP_DIST_REGS
- KVM_DEV_ARM_VGIC_GRP_REDIST_REGS
- Attributes:
- The attr field of kvm_device_attr encodes two values:
- bits: | 63 .... 32 | 31 .... 0 |
- values: | mpidr | offset |
+ KVM_DEV_ARM_VGIC_GRP_DIST_REGS, KVM_DEV_ARM_VGIC_GRP_REDIST_REGS
+ Attributes:
+
+ The attr field of kvm_device_attr encodes two values::
+
+ bits: | 63 .... 32 | 31 .... 0 |
+ values: | mpidr | offset |
All distributor regs are (rw, 32-bit) and kvm_device_attr.addr points to a
__u32 value. 64-bit registers must be accessed by separately accessing the
@@ -93,7 +105,8 @@
redistributor is accessed. The mpidr is ignored for the distributor.
The mpidr encoding is based on the affinity information in the
- architecture defined MPIDR, and the field is encoded as follows:
+ architecture defined MPIDR, and the field is encoded as follows::
+
| 63 .... 56 | 55 .... 48 | 47 .... 40 | 39 .... 32 |
| Aff3 | Aff2 | Aff1 | Aff0 |
@@ -148,24 +161,30 @@
ignored.
Errors:
- -ENXIO: Getting or setting this register is not yet supported
- -EBUSY: One or more VCPUs are running
+
+ ====== =====================================================
+ -ENXIO Getting or setting this register is not yet supported
+ -EBUSY One or more VCPUs are running
+ ====== =====================================================
KVM_DEV_ARM_VGIC_GRP_CPU_SYSREGS
- Attributes:
- The attr field of kvm_device_attr encodes two values:
- bits: | 63 .... 32 | 31 .... 16 | 15 .... 0 |
- values: | mpidr | RES | instr |
+ Attributes:
+
+ The attr field of kvm_device_attr encodes two values::
+
+ bits: | 63 .... 32 | 31 .... 16 | 15 .... 0 |
+ values: | mpidr | RES | instr |
The mpidr field encodes the CPU ID based on the affinity information in the
- architecture defined MPIDR, and the field is encoded as follows:
+ architecture defined MPIDR, and the field is encoded as follows::
+
| 63 .... 56 | 55 .... 48 | 47 .... 40 | 39 .... 32 |
| Aff3 | Aff2 | Aff1 | Aff0 |
The instr field encodes the system register to access based on the fields
defined in the A64 instruction set encoding for system register access
- (RES means the bits are reserved for future use and should be zero):
+ (RES means the bits are reserved for future use and should be zero)::
| 15 ... 14 | 13 ... 11 | 10 ... 7 | 6 ... 3 | 2 ... 0 |
| Op 0 | Op1 | CRn | CRm | Op2 |
@@ -178,26 +197,35 @@
CPU interface registers access is not implemented for AArch32 mode.
Error -ENXIO is returned when accessed in AArch32 mode.
+
Errors:
- -ENXIO: Getting or setting this register is not yet supported
- -EBUSY: VCPU is running
- -EINVAL: Invalid mpidr or register value supplied
+
+ ======= =====================================================
+ -ENXIO Getting or setting this register is not yet supported
+ -EBUSY VCPU is running
+ -EINVAL Invalid mpidr or register value supplied
+ ======= =====================================================
KVM_DEV_ARM_VGIC_GRP_NR_IRQS
- Attributes:
+ Attributes:
+
A value describing the number of interrupts (SGI, PPI and SPI) for
this GIC instance, ranging from 64 to 1024, in increments of 32.
kvm_device_attr.addr points to a __u32 value.
Errors:
- -EINVAL: Value set is out of the expected range
- -EBUSY: Value has already be set.
+
+ ======= ======================================
+ -EINVAL Value set is out of the expected range
+ -EBUSY Value has already be set.
+ ======= ======================================
KVM_DEV_ARM_VGIC_GRP_CTRL
- Attributes:
+ Attributes:
+
KVM_DEV_ARM_VGIC_CTRL_INIT
request the initialization of the VGIC, no additional parameter in
kvm_device_attr.addr.
@@ -205,20 +233,26 @@
save all LPI pending bits into guest RAM pending tables.
The first kB of the pending table is not altered by this operation.
+
Errors:
- -ENXIO: VGIC not properly configured as required prior to calling
- this attribute
- -ENODEV: no online VCPU
- -ENOMEM: memory shortage when allocating vgic internal data
- -EFAULT: Invalid guest ram access
- -EBUSY: One or more VCPUS are running
+
+ ======= ========================================================
+ -ENXIO VGIC not properly configured as required prior to calling
+ this attribute
+ -ENODEV no online VCPU
+ -ENOMEM memory shortage when allocating vgic internal data
+ -EFAULT Invalid guest ram access
+ -EBUSY One or more VCPUS are running
+ ======= ========================================================
KVM_DEV_ARM_VGIC_GRP_LEVEL_INFO
- Attributes:
- The attr field of kvm_device_attr encodes the following values:
- bits: | 63 .... 32 | 31 .... 10 | 9 .... 0 |
- values: | mpidr | info | vINTID |
+ Attributes:
+
+ The attr field of kvm_device_attr encodes the following values::
+
+ bits: | 63 .... 32 | 31 .... 10 | 9 .... 0 |
+ values: | mpidr | info | vINTID |
The vINTID specifies which set of IRQs is reported on.
@@ -228,6 +262,7 @@
VGIC_LEVEL_INFO_LINE_LEVEL:
Get/Set the input level of the IRQ line for a set of 32 contiguously
numbered interrupts.
+
vINTID must be a multiple of 32.
kvm_device_attr.addr points to a __u32 value which will contain a
@@ -243,9 +278,14 @@
reported with the same value regardless of the mpidr specified.
The mpidr field encodes the CPU ID based on the affinity information in the
- architecture defined MPIDR, and the field is encoded as follows:
+ architecture defined MPIDR, and the field is encoded as follows::
+
| 63 .... 56 | 55 .... 48 | 47 .... 40 | 39 .... 32 |
| Aff3 | Aff2 | Aff1 | Aff0 |
+
Errors:
- -EINVAL: vINTID is not multiple of 32 or
- info field is not VGIC_LEVEL_INFO_LINE_LEVEL
+
+ ======= =============================================
+ -EINVAL vINTID is not multiple of 32 or info field is
+ not VGIC_LEVEL_INFO_LINE_LEVEL
+ ======= =============================================
diff --git a/Documentation/virt/kvm/devices/arm-vgic.txt b/Documentation/virt/kvm/devices/arm-vgic.rst
similarity index 66%
rename from Documentation/virt/kvm/devices/arm-vgic.txt
rename to Documentation/virt/kvm/devices/arm-vgic.rst
index 97b6518..40bdeea 100644
--- a/Documentation/virt/kvm/devices/arm-vgic.txt
+++ b/Documentation/virt/kvm/devices/arm-vgic.rst
@@ -1,8 +1,12 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+==================================================
ARM Virtual Generic Interrupt Controller v2 (VGIC)
==================================================
Device types supported:
- KVM_DEV_TYPE_ARM_VGIC_V2 ARM Generic Interrupt Controller v2.0
+
+ - KVM_DEV_TYPE_ARM_VGIC_V2 ARM Generic Interrupt Controller v2.0
Only one VGIC instance may be instantiated through either this API or the
legacy KVM_CREATE_IRQCHIP API. The created VGIC will act as the VM interrupt
@@ -17,7 +21,8 @@
Groups:
KVM_DEV_ARM_VGIC_GRP_ADDR
- Attributes:
+ Attributes:
+
KVM_VGIC_V2_ADDR_TYPE_DIST (rw, 64-bit)
Base address in the guest physical address space of the GIC distributor
register mappings. Only valid for KVM_DEV_TYPE_ARM_VGIC_V2.
@@ -27,19 +32,25 @@
Base address in the guest physical address space of the GIC virtual cpu
interface register mappings. Only valid for KVM_DEV_TYPE_ARM_VGIC_V2.
This address needs to be 4K aligned and the region covers 4 KByte.
+
Errors:
- -E2BIG: Address outside of addressable IPA range
- -EINVAL: Incorrectly aligned address
- -EEXIST: Address already configured
- -ENXIO: The group or attribute is unknown/unsupported for this device
+
+ ======= =============================================================
+ -E2BIG Address outside of addressable IPA range
+ -EINVAL Incorrectly aligned address
+ -EEXIST Address already configured
+ -ENXIO The group or attribute is unknown/unsupported for this device
or hardware support is missing.
- -EFAULT: Invalid user pointer for attr->addr.
+ -EFAULT Invalid user pointer for attr->addr.
+ ======= =============================================================
KVM_DEV_ARM_VGIC_GRP_DIST_REGS
- Attributes:
- The attr field of kvm_device_attr encodes two values:
- bits: | 63 .... 40 | 39 .. 32 | 31 .... 0 |
- values: | reserved | vcpu_index | offset |
+ Attributes:
+
+ The attr field of kvm_device_attr encodes two values::
+
+ bits: | 63 .... 40 | 39 .. 32 | 31 .... 0 |
+ values: | reserved | vcpu_index | offset |
All distributor regs are (rw, 32-bit)
@@ -58,16 +69,22 @@
KVM_DEV_ARM_VGIC_GRP_DIST_REGS and KVM_DEV_ARM_VGIC_GRP_CPU_REGS) to ensure
the expected behavior. Unless GICD_IIDR has been set from userspace, writes
to the interrupt group registers (GICD_IGROUPR) are ignored.
+
Errors:
- -ENXIO: Getting or setting this register is not yet supported
- -EBUSY: One or more VCPUs are running
- -EINVAL: Invalid vcpu_index supplied
+
+ ======= =====================================================
+ -ENXIO Getting or setting this register is not yet supported
+ -EBUSY One or more VCPUs are running
+ -EINVAL Invalid vcpu_index supplied
+ ======= =====================================================
KVM_DEV_ARM_VGIC_GRP_CPU_REGS
- Attributes:
- The attr field of kvm_device_attr encodes two values:
- bits: | 63 .... 40 | 39 .. 32 | 31 .... 0 |
- values: | reserved | vcpu_index | offset |
+ Attributes:
+
+ The attr field of kvm_device_attr encodes two values::
+
+ bits: | 63 .... 40 | 39 .. 32 | 31 .... 0 |
+ values: | reserved | vcpu_index | offset |
All CPU interface regs are (rw, 32-bit)
@@ -101,27 +118,39 @@
value left by 3 places to obtain the actual priority mask level.
Errors:
- -ENXIO: Getting or setting this register is not yet supported
- -EBUSY: One or more VCPUs are running
- -EINVAL: Invalid vcpu_index supplied
+
+ ======= =====================================================
+ -ENXIO Getting or setting this register is not yet supported
+ -EBUSY One or more VCPUs are running
+ -EINVAL Invalid vcpu_index supplied
+ ======= =====================================================
KVM_DEV_ARM_VGIC_GRP_NR_IRQS
- Attributes:
+ Attributes:
+
A value describing the number of interrupts (SGI, PPI and SPI) for
this GIC instance, ranging from 64 to 1024, in increments of 32.
Errors:
- -EINVAL: Value set is out of the expected range
- -EBUSY: Value has already be set, or GIC has already been initialized
- with default values.
+
+ ======= =============================================================
+ -EINVAL Value set is out of the expected range
+ -EBUSY Value has already be set, or GIC has already been initialized
+ with default values.
+ ======= =============================================================
KVM_DEV_ARM_VGIC_GRP_CTRL
- Attributes:
+ Attributes:
+
KVM_DEV_ARM_VGIC_CTRL_INIT
request the initialization of the VGIC or ITS, no additional parameter
in kvm_device_attr.addr.
+
Errors:
- -ENXIO: VGIC not properly configured as required prior to calling
- this attribute
- -ENODEV: no online VCPU
- -ENOMEM: memory shortage when allocating vgic internal data
+
+ ======= =========================================================
+ -ENXIO VGIC not properly configured as required prior to calling
+ this attribute
+ -ENODEV no online VCPU
+ -ENOMEM memory shortage when allocating vgic internal data
+ ======= =========================================================
diff --git a/Documentation/virt/kvm/devices/index.rst b/Documentation/virt/kvm/devices/index.rst
new file mode 100644
index 0000000..192cda7
--- /dev/null
+++ b/Documentation/virt/kvm/devices/index.rst
@@ -0,0 +1,19 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+=======
+Devices
+=======
+
+.. toctree::
+ :maxdepth: 2
+
+ arm-vgic-its
+ arm-vgic
+ arm-vgic-v3
+ mpic
+ s390_flic
+ vcpu
+ vfio
+ vm
+ xics
+ xive
diff --git a/Documentation/virt/kvm/devices/mpic.txt b/Documentation/virt/kvm/devices/mpic.rst
similarity index 90%
rename from Documentation/virt/kvm/devices/mpic.txt
rename to Documentation/virt/kvm/devices/mpic.rst
index 8257397..55cefe0 100644
--- a/Documentation/virt/kvm/devices/mpic.txt
+++ b/Documentation/virt/kvm/devices/mpic.rst
@@ -1,9 +1,13 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+=========================
MPIC interrupt controller
=========================
Device types supported:
- KVM_DEV_TYPE_FSL_MPIC_20 Freescale MPIC v2.0
- KVM_DEV_TYPE_FSL_MPIC_42 Freescale MPIC v4.2
+
+ - KVM_DEV_TYPE_FSL_MPIC_20 Freescale MPIC v2.0
+ - KVM_DEV_TYPE_FSL_MPIC_42 Freescale MPIC v4.2
Only one MPIC instance, of any type, may be instantiated. The created
MPIC will act as the system interrupt controller, connecting to each
@@ -11,7 +15,8 @@
Groups:
KVM_DEV_MPIC_GRP_MISC
- Attributes:
+ Attributes:
+
KVM_DEV_MPIC_BASE_ADDR (rw, 64-bit)
Base address of the 256 KiB MPIC register space. Must be
naturally aligned. A value of zero disables the mapping.
diff --git a/Documentation/virt/kvm/devices/s390_flic.txt b/Documentation/virt/kvm/devices/s390_flic.rst
similarity index 85%
rename from Documentation/virt/kvm/devices/s390_flic.txt
rename to Documentation/virt/kvm/devices/s390_flic.rst
index a4e20a0..ea96559 100644
--- a/Documentation/virt/kvm/devices/s390_flic.txt
+++ b/Documentation/virt/kvm/devices/s390_flic.rst
@@ -1,3 +1,6 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+====================================
FLIC (floating interrupt controller)
====================================
@@ -31,8 +34,10 @@
Copies all floating interrupts into a buffer provided by userspace.
When the buffer is too small it returns -ENOMEM, which is the indication
for userspace to try again with a bigger buffer.
+
-ENOBUFS is returned when the allocation of a kernelspace buffer has
failed.
+
-EFAULT is returned when copying data to userspace failed.
All interrupts remain pending, i.e. are not deleted from the list of
currently pending interrupts.
@@ -60,38 +65,41 @@
KVM_DEV_FLIC_ADAPTER_REGISTER
Register an I/O adapter interrupt source. Takes a kvm_s390_io_adapter
- describing the adapter to register:
+ describing the adapter to register::
-struct kvm_s390_io_adapter {
- __u32 id;
- __u8 isc;
- __u8 maskable;
- __u8 swap;
- __u8 flags;
-};
+ struct kvm_s390_io_adapter {
+ __u32 id;
+ __u8 isc;
+ __u8 maskable;
+ __u8 swap;
+ __u8 flags;
+ };
id contains the unique id for the adapter, isc the I/O interruption subclass
to use, maskable whether this adapter may be masked (interrupts turned off),
swap whether the indicators need to be byte swapped, and flags contains
further characteristics of the adapter.
+
Currently defined values for 'flags' are:
+
- KVM_S390_ADAPTER_SUPPRESSIBLE: adapter is subject to AIS
(adapter-interrupt-suppression) facility. This flag only has an effect if
the AIS capability is enabled.
+
Unknown flag values are ignored.
KVM_DEV_FLIC_ADAPTER_MODIFY
Modifies attributes of an existing I/O adapter interrupt source. Takes
- a kvm_s390_io_adapter_req specifying the adapter and the operation:
+ a kvm_s390_io_adapter_req specifying the adapter and the operation::
-struct kvm_s390_io_adapter_req {
- __u32 id;
- __u8 type;
- __u8 mask;
- __u16 pad0;
- __u64 addr;
-};
+ struct kvm_s390_io_adapter_req {
+ __u32 id;
+ __u8 type;
+ __u8 mask;
+ __u16 pad0;
+ __u64 addr;
+ };
id specifies the adapter and type the operation. The supported operations
are:
@@ -100,28 +108,23 @@
mask or unmask the adapter, as specified in mask
KVM_S390_IO_ADAPTER_MAP
- perform a gmap translation for the guest address provided in addr,
- pin a userspace page for the translated address and add it to the
- list of mappings
- Note: A new mapping will be created unconditionally; therefore,
- the calling code should avoid making duplicate mappings.
-
+ This is now a no-op. The mapping is purely done by the irq route.
KVM_S390_IO_ADAPTER_UNMAP
- release a userspace page for the translated address specified in addr
- from the list of mappings
+ This is now a no-op. The mapping is purely done by the irq route.
KVM_DEV_FLIC_AISM
modify the adapter-interruption-suppression mode for a given isc if the
- AIS capability is enabled. Takes a kvm_s390_ais_req describing:
+ AIS capability is enabled. Takes a kvm_s390_ais_req describing::
-struct kvm_s390_ais_req {
- __u8 isc;
- __u16 mode;
-};
+ struct kvm_s390_ais_req {
+ __u8 isc;
+ __u16 mode;
+ };
isc contains the target I/O interruption subclass, mode the target
adapter-interruption-suppression mode. The following modes are
currently supported:
+
- KVM_S390_AIS_MODE_ALL: ALL-Interruptions Mode, i.e. airq injection
is always allowed;
- KVM_S390_AIS_MODE_SINGLE: SINGLE-Interruption Mode, i.e. airq
@@ -139,12 +142,12 @@
KVM_DEV_FLIC_AISM_ALL
Gets or sets the adapter-interruption-suppression mode for all ISCs. Takes
- a kvm_s390_ais_all describing:
+ a kvm_s390_ais_all describing::
-struct kvm_s390_ais_all {
- __u8 simm; /* Single-Interruption-Mode mask */
- __u8 nimm; /* No-Interruption-Mode mask *
-};
+ struct kvm_s390_ais_all {
+ __u8 simm; /* Single-Interruption-Mode mask */
+ __u8 nimm; /* No-Interruption-Mode mask *
+ };
simm contains Single-Interruption-Mode mask for all ISCs, nimm contains
No-Interruption-Mode mask for all ISCs. Each bit in simm and nimm corresponds
@@ -159,5 +162,5 @@
that a FLIC operation is unavailable based on the error code resulting from a
usage attempt.
-Note: The KVM_DEV_FLIC_CLEAR_IO_IRQ ioctl will return EINVAL in case a zero
-schid is specified.
+.. note:: The KVM_DEV_FLIC_CLEAR_IO_IRQ ioctl will return EINVAL in case a
+ zero schid is specified.
diff --git a/Documentation/virt/kvm/devices/vcpu.rst b/Documentation/virt/kvm/devices/vcpu.rst
new file mode 100644
index 0000000..2acec3b
--- /dev/null
+++ b/Documentation/virt/kvm/devices/vcpu.rst
@@ -0,0 +1,163 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+======================
+Generic vcpu interface
+======================
+
+The virtual cpu "device" also accepts the ioctls KVM_SET_DEVICE_ATTR,
+KVM_GET_DEVICE_ATTR, and KVM_HAS_DEVICE_ATTR. The interface uses the same struct
+kvm_device_attr as other devices, but targets VCPU-wide settings and controls.
+
+The groups and attributes per virtual cpu, if any, are architecture specific.
+
+1. GROUP: KVM_ARM_VCPU_PMU_V3_CTRL
+==================================
+
+:Architectures: ARM64
+
+1.1. ATTRIBUTE: KVM_ARM_VCPU_PMU_V3_IRQ
+---------------------------------------
+
+:Parameters: in kvm_device_attr.addr the address for PMU overflow interrupt is a
+ pointer to an int
+
+Returns:
+
+ ======= ========================================================
+ -EBUSY The PMU overflow interrupt is already set
+ -EFAULT Error reading interrupt number
+ -ENXIO PMUv3 not supported or the overflow interrupt not set
+ when attempting to get it
+ -ENODEV KVM_ARM_VCPU_PMU_V3 feature missing from VCPU
+ -EINVAL Invalid PMU overflow interrupt number supplied or
+ trying to set the IRQ number without using an in-kernel
+ irqchip.
+ ======= ========================================================
+
+A value describing the PMUv3 (Performance Monitor Unit v3) overflow interrupt
+number for this vcpu. This interrupt could be a PPI or SPI, but the interrupt
+type must be same for each vcpu. As a PPI, the interrupt number is the same for
+all vcpus, while as an SPI it must be a separate number per vcpu.
+
+1.2 ATTRIBUTE: KVM_ARM_VCPU_PMU_V3_INIT
+---------------------------------------
+
+:Parameters: no additional parameter in kvm_device_attr.addr
+
+Returns:
+
+ ======= ======================================================
+ -EEXIST Interrupt number already used
+ -ENODEV PMUv3 not supported or GIC not initialized
+ -ENXIO PMUv3 not supported, missing VCPU feature or interrupt
+ number not set
+ -EBUSY PMUv3 already initialized
+ ======= ======================================================
+
+Request the initialization of the PMUv3. If using the PMUv3 with an in-kernel
+virtual GIC implementation, this must be done after initializing the in-kernel
+irqchip.
+
+1.3 ATTRIBUTE: KVM_ARM_VCPU_PMU_V3_FILTER
+-----------------------------------------
+
+:Parameters: in kvm_device_attr.addr the address for a PMU event filter is a
+ pointer to a struct kvm_pmu_event_filter
+
+:Returns:
+
+ ======= ======================================================
+ -ENODEV PMUv3 not supported or GIC not initialized
+ -ENXIO PMUv3 not properly configured or in-kernel irqchip not
+ configured as required prior to calling this attribute
+ -EBUSY PMUv3 already initialized
+ -EINVAL Invalid filter range
+ ======= ======================================================
+
+Request the installation of a PMU event filter described as follows::
+
+ struct kvm_pmu_event_filter {
+ __u16 base_event;
+ __u16 nevents;
+
+ #define KVM_PMU_EVENT_ALLOW 0
+ #define KVM_PMU_EVENT_DENY 1
+
+ __u8 action;
+ __u8 pad[3];
+ };
+
+A filter range is defined as the range [@base_event, @base_event + @nevents),
+together with an @action (KVM_PMU_EVENT_ALLOW or KVM_PMU_EVENT_DENY). The
+first registered range defines the global policy (global ALLOW if the first
+@action is DENY, global DENY if the first @action is ALLOW). Multiple ranges
+can be programmed, and must fit within the event space defined by the PMU
+architecture (10 bits on ARMv8.0, 16 bits from ARMv8.1 onwards).
+
+Note: "Cancelling" a filter by registering the opposite action for the same
+range doesn't change the default action. For example, installing an ALLOW
+filter for event range [0:10) as the first filter and then applying a DENY
+action for the same range will leave the whole range as disabled.
+
+Restrictions: Event 0 (SW_INCR) is never filtered, as it doesn't count a
+hardware event. Filtering event 0x1E (CHAIN) has no effect either, as it
+isn't strictly speaking an event. Filtering the cycle counter is possible
+using event 0x11 (CPU_CYCLES).
+
+
+2. GROUP: KVM_ARM_VCPU_TIMER_CTRL
+=================================
+
+:Architectures: ARM, ARM64
+
+2.1. ATTRIBUTES: KVM_ARM_VCPU_TIMER_IRQ_VTIMER, KVM_ARM_VCPU_TIMER_IRQ_PTIMER
+-----------------------------------------------------------------------------
+
+:Parameters: in kvm_device_attr.addr the address for the timer interrupt is a
+ pointer to an int
+
+Returns:
+
+ ======= =================================
+ -EINVAL Invalid timer interrupt number
+ -EBUSY One or more VCPUs has already run
+ ======= =================================
+
+A value describing the architected timer interrupt number when connected to an
+in-kernel virtual GIC. These must be a PPI (16 <= intid < 32). Setting the
+attribute overrides the default values (see below).
+
+============================= ==========================================
+KVM_ARM_VCPU_TIMER_IRQ_VTIMER The EL1 virtual timer intid (default: 27)
+KVM_ARM_VCPU_TIMER_IRQ_PTIMER The EL1 physical timer intid (default: 30)
+============================= ==========================================
+
+Setting the same PPI for different timers will prevent the VCPUs from running.
+Setting the interrupt number on a VCPU configures all VCPUs created at that
+time to use the number provided for a given timer, overwriting any previously
+configured values on other VCPUs. Userspace should configure the interrupt
+numbers on at least one VCPU after creating all VCPUs and before running any
+VCPUs.
+
+3. GROUP: KVM_ARM_VCPU_PVTIME_CTRL
+==================================
+
+:Architectures: ARM64
+
+3.1 ATTRIBUTE: KVM_ARM_VCPU_PVTIME_IPA
+--------------------------------------
+
+:Parameters: 64-bit base address
+
+Returns:
+
+ ======= ======================================
+ -ENXIO Stolen time not implemented
+ -EEXIST Base address already set for this VCPU
+ -EINVAL Base address not 64 byte aligned
+ ======= ======================================
+
+Specifies the base address of the stolen time structure for this VCPU. The
+base address must be 64 byte aligned and exist within a valid guest memory
+region. See Documentation/virt/kvm/arm/pvtime.rst for more information
+including the layout of the stolen time structure.
diff --git a/Documentation/virt/kvm/devices/vcpu.txt b/Documentation/virt/kvm/devices/vcpu.txt
deleted file mode 100644
index 2b5dab1..0000000
--- a/Documentation/virt/kvm/devices/vcpu.txt
+++ /dev/null
@@ -1,62 +0,0 @@
-Generic vcpu interface
-====================================
-
-The virtual cpu "device" also accepts the ioctls KVM_SET_DEVICE_ATTR,
-KVM_GET_DEVICE_ATTR, and KVM_HAS_DEVICE_ATTR. The interface uses the same struct
-kvm_device_attr as other devices, but targets VCPU-wide settings and controls.
-
-The groups and attributes per virtual cpu, if any, are architecture specific.
-
-1. GROUP: KVM_ARM_VCPU_PMU_V3_CTRL
-Architectures: ARM64
-
-1.1. ATTRIBUTE: KVM_ARM_VCPU_PMU_V3_IRQ
-Parameters: in kvm_device_attr.addr the address for PMU overflow interrupt is a
- pointer to an int
-Returns: -EBUSY: The PMU overflow interrupt is already set
- -ENXIO: The overflow interrupt not set when attempting to get it
- -ENODEV: PMUv3 not supported
- -EINVAL: Invalid PMU overflow interrupt number supplied or
- trying to set the IRQ number without using an in-kernel
- irqchip.
-
-A value describing the PMUv3 (Performance Monitor Unit v3) overflow interrupt
-number for this vcpu. This interrupt could be a PPI or SPI, but the interrupt
-type must be same for each vcpu. As a PPI, the interrupt number is the same for
-all vcpus, while as an SPI it must be a separate number per vcpu.
-
-1.2 ATTRIBUTE: KVM_ARM_VCPU_PMU_V3_INIT
-Parameters: no additional parameter in kvm_device_attr.addr
-Returns: -ENODEV: PMUv3 not supported or GIC not initialized
- -ENXIO: PMUv3 not properly configured or in-kernel irqchip not
- configured as required prior to calling this attribute
- -EBUSY: PMUv3 already initialized
-
-Request the initialization of the PMUv3. If using the PMUv3 with an in-kernel
-virtual GIC implementation, this must be done after initializing the in-kernel
-irqchip.
-
-
-2. GROUP: KVM_ARM_VCPU_TIMER_CTRL
-Architectures: ARM,ARM64
-
-2.1. ATTRIBUTE: KVM_ARM_VCPU_TIMER_IRQ_VTIMER
-2.2. ATTRIBUTE: KVM_ARM_VCPU_TIMER_IRQ_PTIMER
-Parameters: in kvm_device_attr.addr the address for the timer interrupt is a
- pointer to an int
-Returns: -EINVAL: Invalid timer interrupt number
- -EBUSY: One or more VCPUs has already run
-
-A value describing the architected timer interrupt number when connected to an
-in-kernel virtual GIC. These must be a PPI (16 <= intid < 32). Setting the
-attribute overrides the default values (see below).
-
-KVM_ARM_VCPU_TIMER_IRQ_VTIMER: The EL1 virtual timer intid (default: 27)
-KVM_ARM_VCPU_TIMER_IRQ_PTIMER: The EL1 physical timer intid (default: 30)
-
-Setting the same PPI for different timers will prevent the VCPUs from running.
-Setting the interrupt number on a VCPU configures all VCPUs created at that
-time to use the number provided for a given timer, overwriting any previously
-configured values on other VCPUs. Userspace should configure the interrupt
-numbers on at least one VCPU after creating all VCPUs and before running any
-VCPUs.
diff --git a/Documentation/virt/kvm/devices/vfio.txt b/Documentation/virt/kvm/devices/vfio.rst
similarity index 72%
rename from Documentation/virt/kvm/devices/vfio.txt
rename to Documentation/virt/kvm/devices/vfio.rst
index 528c77c..2d20dc5 100644
--- a/Documentation/virt/kvm/devices/vfio.txt
+++ b/Documentation/virt/kvm/devices/vfio.rst
@@ -1,8 +1,12 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+===================
VFIO virtual device
===================
Device types supported:
- KVM_DEV_TYPE_VFIO
+
+ - KVM_DEV_TYPE_VFIO
Only one VFIO instance may be created per VM. The created device
tracks VFIO groups in use by the VM and features of those groups
@@ -23,14 +27,15 @@
for the VFIO group.
KVM_DEV_VFIO_GROUP_SET_SPAPR_TCE: attaches a guest visible TCE table
allocated by sPAPR KVM.
- kvm_device_attr.addr points to a struct:
+ kvm_device_attr.addr points to a struct::
- struct kvm_vfio_spapr_tce {
- __s32 groupfd;
- __s32 tablefd;
- };
+ struct kvm_vfio_spapr_tce {
+ __s32 groupfd;
+ __s32 tablefd;
+ };
- where
- @groupfd is a file descriptor for a VFIO group;
- @tablefd is a file descriptor for a TCE table allocated via
- KVM_CREATE_SPAPR_TCE.
+ where:
+
+ - @groupfd is a file descriptor for a VFIO group;
+ - @tablefd is a file descriptor for a TCE table allocated via
+ KVM_CREATE_SPAPR_TCE.
diff --git a/Documentation/virt/kvm/devices/vm.txt b/Documentation/virt/kvm/devices/vm.rst
similarity index 61%
rename from Documentation/virt/kvm/devices/vm.txt
rename to Documentation/virt/kvm/devices/vm.rst
index 4ffb82b..0aa5b1c 100644
--- a/Documentation/virt/kvm/devices/vm.txt
+++ b/Documentation/virt/kvm/devices/vm.rst
@@ -1,5 +1,8 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+====================
Generic vm interface
-====================================
+====================
The virtual machine "device" also accepts the ioctls KVM_SET_DEVICE_ATTR,
KVM_GET_DEVICE_ATTR, and KVM_HAS_DEVICE_ATTR. The interface uses the same
@@ -10,30 +13,38 @@
specific.
1. GROUP: KVM_S390_VM_MEM_CTRL
-Architectures: s390
+==============================
+
+:Architectures: s390
1.1. ATTRIBUTE: KVM_S390_VM_MEM_ENABLE_CMMA
-Parameters: none
-Returns: -EBUSY if a vcpu is already defined, otherwise 0
+-------------------------------------------
+
+:Parameters: none
+:Returns: -EBUSY if a vcpu is already defined, otherwise 0
Enables Collaborative Memory Management Assist (CMMA) for the virtual machine.
1.2. ATTRIBUTE: KVM_S390_VM_MEM_CLR_CMMA
-Parameters: none
-Returns: -EINVAL if CMMA was not enabled
- 0 otherwise
+----------------------------------------
+
+:Parameters: none
+:Returns: -EINVAL if CMMA was not enabled;
+ 0 otherwise
Clear the CMMA status for all guest pages, so any pages the guest marked
as unused are again used any may not be reclaimed by the host.
1.3. ATTRIBUTE KVM_S390_VM_MEM_LIMIT_SIZE
-Parameters: in attr->addr the address for the new limit of guest memory
-Returns: -EFAULT if the given address is not accessible
- -EINVAL if the virtual machine is of type UCONTROL
- -E2BIG if the given guest memory is to big for that machine
- -EBUSY if a vcpu is already defined
- -ENOMEM if not enough memory is available for a new shadow guest mapping
- 0 otherwise
+-----------------------------------------
+
+:Parameters: in attr->addr the address for the new limit of guest memory
+:Returns: -EFAULT if the given address is not accessible;
+ -EINVAL if the virtual machine is of type UCONTROL;
+ -E2BIG if the given guest memory is to big for that machine;
+ -EBUSY if a vcpu is already defined;
+ -ENOMEM if not enough memory is available for a new shadow guest mapping;
+ 0 otherwise.
Allows userspace to query the actual limit and set a new limit for
the maximum guest memory size. The limit will be rounded up to
@@ -42,78 +53,92 @@
the limit to KVM_S390_NO_MEM_LIMIT (U64_MAX).
2. GROUP: KVM_S390_VM_CPU_MODEL
-Architectures: s390
+===============================
+
+:Architectures: s390
2.1. ATTRIBUTE: KVM_S390_VM_CPU_MACHINE (r/o)
+---------------------------------------------
-Allows user space to retrieve machine and kvm specific cpu related information:
+Allows user space to retrieve machine and kvm specific cpu related information::
-struct kvm_s390_vm_cpu_machine {
+ struct kvm_s390_vm_cpu_machine {
__u64 cpuid; # CPUID of host
__u32 ibc; # IBC level range offered by host
__u8 pad[4];
__u64 fac_mask[256]; # set of cpu facilities enabled by KVM
__u64 fac_list[256]; # set of cpu facilities offered by host
-}
+ }
-Parameters: address of buffer to store the machine related cpu data
- of type struct kvm_s390_vm_cpu_machine*
-Returns: -EFAULT if the given address is not accessible from kernel space
- -ENOMEM if not enough memory is available to process the ioctl
- 0 in case of success
+:Parameters: address of buffer to store the machine related cpu data
+ of type struct kvm_s390_vm_cpu_machine*
+:Returns: -EFAULT if the given address is not accessible from kernel space;
+ -ENOMEM if not enough memory is available to process the ioctl;
+ 0 in case of success.
2.2. ATTRIBUTE: KVM_S390_VM_CPU_PROCESSOR (r/w)
+===============================================
-Allows user space to retrieve or request to change cpu related information for a vcpu:
+Allows user space to retrieve or request to change cpu related information for a vcpu::
-struct kvm_s390_vm_cpu_processor {
+ struct kvm_s390_vm_cpu_processor {
__u64 cpuid; # CPUID currently (to be) used by this vcpu
__u16 ibc; # IBC level currently (to be) used by this vcpu
__u8 pad[6];
__u64 fac_list[256]; # set of cpu facilities currently (to be) used
- # by this vcpu
-}
+ # by this vcpu
+ }
KVM does not enforce or limit the cpu model data in any form. Take the information
retrieved by means of KVM_S390_VM_CPU_MACHINE as hint for reasonable configuration
setups. Instruction interceptions triggered by additionally set facility bits that
are not handled by KVM need to by imlemented in the VM driver code.
-Parameters: address of buffer to store/set the processor related cpu
- data of type struct kvm_s390_vm_cpu_processor*.
-Returns: -EBUSY in case 1 or more vcpus are already activated (only in write case)
- -EFAULT if the given address is not accessible from kernel space
- -ENOMEM if not enough memory is available to process the ioctl
- 0 in case of success
+:Parameters: address of buffer to store/set the processor related cpu
+ data of type struct kvm_s390_vm_cpu_processor*.
+:Returns: -EBUSY in case 1 or more vcpus are already activated (only in write case);
+ -EFAULT if the given address is not accessible from kernel space;
+ -ENOMEM if not enough memory is available to process the ioctl;
+ 0 in case of success.
+
+.. _KVM_S390_VM_CPU_MACHINE_FEAT:
2.3. ATTRIBUTE: KVM_S390_VM_CPU_MACHINE_FEAT (r/o)
+--------------------------------------------------
Allows user space to retrieve available cpu features. A feature is available if
provided by the hardware and supported by kvm. In theory, cpu features could
even be completely emulated by kvm.
-struct kvm_s390_vm_cpu_feat {
- __u64 feat[16]; # Bitmap (1 = feature available), MSB 0 bit numbering
-};
+::
-Parameters: address of a buffer to load the feature list from.
-Returns: -EFAULT if the given address is not accessible from kernel space.
- 0 in case of success.
+ struct kvm_s390_vm_cpu_feat {
+ __u64 feat[16]; # Bitmap (1 = feature available), MSB 0 bit numbering
+ };
+
+:Parameters: address of a buffer to load the feature list from.
+:Returns: -EFAULT if the given address is not accessible from kernel space;
+ 0 in case of success.
2.4. ATTRIBUTE: KVM_S390_VM_CPU_PROCESSOR_FEAT (r/w)
+----------------------------------------------------
Allows user space to retrieve or change enabled cpu features for all VCPUs of a
VM. Features that are not available cannot be enabled.
-See 2.3. for a description of the parameter struct.
+See :ref:`KVM_S390_VM_CPU_MACHINE_FEAT` for
+a description of the parameter struct.
-Parameters: address of a buffer to store/load the feature list from.
-Returns: -EFAULT if the given address is not accessible from kernel space.
- -EINVAL if a cpu feature that is not available is to be enabled.
- -EBUSY if at least one VCPU has already been defined.
+:Parameters: address of a buffer to store/load the feature list from.
+:Returns: -EFAULT if the given address is not accessible from kernel space;
+ -EINVAL if a cpu feature that is not available is to be enabled;
+ -EBUSY if at least one VCPU has already been defined;
0 in case of success.
+.. _KVM_S390_VM_CPU_MACHINE_SUBFUNC:
+
2.5. ATTRIBUTE: KVM_S390_VM_CPU_MACHINE_SUBFUNC (r/o)
+-----------------------------------------------------
Allows user space to retrieve available cpu subfunctions without any filtering
done by a set IBC. These subfunctions are indicated to the guest VCPU via
@@ -126,7 +151,9 @@
indicates subfunctions via a "test bit" mechanism, the subfunction codes are
contained in the returned struct in MSB 0 bit numbering.
-struct kvm_s390_vm_cpu_subfunc {
+::
+
+ struct kvm_s390_vm_cpu_subfunc {
u8 plo[32]; # always valid (ESA/390 feature)
u8 ptff[16]; # valid with TOD-clock steering
u8 kmac[16]; # valid with Message-Security-Assist
@@ -143,13 +170,14 @@
u8 kma[16]; # valid with Message-Security-Assist-Extension 8
u8 kdsa[16]; # valid with Message-Security-Assist-Extension 9
u8 reserved[1792]; # reserved for future instructions
-};
+ };
-Parameters: address of a buffer to load the subfunction blocks from.
-Returns: -EFAULT if the given address is not accessible from kernel space.
+:Parameters: address of a buffer to load the subfunction blocks from.
+:Returns: -EFAULT if the given address is not accessible from kernel space;
0 in case of success.
2.6. ATTRIBUTE: KVM_S390_VM_CPU_PROCESSOR_SUBFUNC (r/w)
+-------------------------------------------------------
Allows user space to retrieve or change cpu subfunctions to be indicated for
all VCPUs of a VM. This attribute will only be available if kernel and
@@ -164,107 +192,125 @@
to determine available subfunctions in this case, this will guarantee backward
compatibility.
-See 2.5. for a description of the parameter struct.
+See :ref:`KVM_S390_VM_CPU_MACHINE_SUBFUNC` for a
+description of the parameter struct.
-Parameters: address of a buffer to store/load the subfunction blocks from.
-Returns: -EFAULT if the given address is not accessible from kernel space.
- -EINVAL when reading, if there was no write yet.
- -EBUSY if at least one VCPU has already been defined.
+:Parameters: address of a buffer to store/load the subfunction blocks from.
+:Returns: -EFAULT if the given address is not accessible from kernel space;
+ -EINVAL when reading, if there was no write yet;
+ -EBUSY if at least one VCPU has already been defined;
0 in case of success.
3. GROUP: KVM_S390_VM_TOD
-Architectures: s390
+=========================
+
+:Architectures: s390
3.1. ATTRIBUTE: KVM_S390_VM_TOD_HIGH
+------------------------------------
Allows user space to set/get the TOD clock extension (u8) (superseded by
KVM_S390_VM_TOD_EXT).
-Parameters: address of a buffer in user space to store the data (u8) to
-Returns: -EFAULT if the given address is not accessible from kernel space
+:Parameters: address of a buffer in user space to store the data (u8) to
+:Returns: -EFAULT if the given address is not accessible from kernel space;
-EINVAL if setting the TOD clock extension to != 0 is not supported
3.2. ATTRIBUTE: KVM_S390_VM_TOD_LOW
+-----------------------------------
Allows user space to set/get bits 0-63 of the TOD clock register as defined in
the POP (u64).
-Parameters: address of a buffer in user space to store the data (u64) to
-Returns: -EFAULT if the given address is not accessible from kernel space
+:Parameters: address of a buffer in user space to store the data (u64) to
+:Returns: -EFAULT if the given address is not accessible from kernel space
3.3. ATTRIBUTE: KVM_S390_VM_TOD_EXT
+-----------------------------------
+
Allows user space to set/get bits 0-63 of the TOD clock register as defined in
the POP (u64). If the guest CPU model supports the TOD clock extension (u8), it
also allows user space to get/set it. If the guest CPU model does not support
it, it is stored as 0 and not allowed to be set to a value != 0.
-Parameters: address of a buffer in user space to store the data
- (kvm_s390_vm_tod_clock) to
-Returns: -EFAULT if the given address is not accessible from kernel space
+:Parameters: address of a buffer in user space to store the data
+ (kvm_s390_vm_tod_clock) to
+:Returns: -EFAULT if the given address is not accessible from kernel space;
-EINVAL if setting the TOD clock extension to != 0 is not supported
4. GROUP: KVM_S390_VM_CRYPTO
-Architectures: s390
+============================
+
+:Architectures: s390
4.1. ATTRIBUTE: KVM_S390_VM_CRYPTO_ENABLE_AES_KW (w/o)
+------------------------------------------------------
Allows user space to enable aes key wrapping, including generating a new
wrapping key.
-Parameters: none
-Returns: 0
+:Parameters: none
+:Returns: 0
4.2. ATTRIBUTE: KVM_S390_VM_CRYPTO_ENABLE_DEA_KW (w/o)
+------------------------------------------------------
Allows user space to enable dea key wrapping, including generating a new
wrapping key.
-Parameters: none
-Returns: 0
+:Parameters: none
+:Returns: 0
4.3. ATTRIBUTE: KVM_S390_VM_CRYPTO_DISABLE_AES_KW (w/o)
+-------------------------------------------------------
Allows user space to disable aes key wrapping, clearing the wrapping key.
-Parameters: none
-Returns: 0
+:Parameters: none
+:Returns: 0
4.4. ATTRIBUTE: KVM_S390_VM_CRYPTO_DISABLE_DEA_KW (w/o)
+-------------------------------------------------------
Allows user space to disable dea key wrapping, clearing the wrapping key.
-Parameters: none
-Returns: 0
+:Parameters: none
+:Returns: 0
5. GROUP: KVM_S390_VM_MIGRATION
-Architectures: s390
+===============================
+
+:Architectures: s390
5.1. ATTRIBUTE: KVM_S390_VM_MIGRATION_STOP (w/o)
+------------------------------------------------
Allows userspace to stop migration mode, needed for PGSTE migration.
Setting this attribute when migration mode is not active will have no
effects.
-Parameters: none
-Returns: 0
+:Parameters: none
+:Returns: 0
5.2. ATTRIBUTE: KVM_S390_VM_MIGRATION_START (w/o)
+-------------------------------------------------
Allows userspace to start migration mode, needed for PGSTE migration.
Setting this attribute when migration mode is already active will have
no effects.
-Parameters: none
-Returns: -ENOMEM if there is not enough free memory to start migration mode
- -EINVAL if the state of the VM is invalid (e.g. no memory defined)
+:Parameters: none
+:Returns: -ENOMEM if there is not enough free memory to start migration mode;
+ -EINVAL if the state of the VM is invalid (e.g. no memory defined);
0 in case of success.
5.3. ATTRIBUTE: KVM_S390_VM_MIGRATION_STATUS (r/o)
+--------------------------------------------------
Allows userspace to query the status of migration mode.
-Parameters: address of a buffer in user space to store the data (u64) to;
- the data itself is either 0 if migration mode is disabled or 1
- if it is enabled
-Returns: -EFAULT if the given address is not accessible from kernel space
+:Parameters: address of a buffer in user space to store the data (u64) to;
+ the data itself is either 0 if migration mode is disabled or 1
+ if it is enabled
+:Returns: -EFAULT if the given address is not accessible from kernel space;
0 in case of success.
diff --git a/Documentation/virt/kvm/devices/xics.txt b/Documentation/virt/kvm/devices/xics.rst
similarity index 75%
rename from Documentation/virt/kvm/devices/xics.txt
rename to Documentation/virt/kvm/devices/xics.rst
index 4286493..2d6927e 100644
--- a/Documentation/virt/kvm/devices/xics.txt
+++ b/Documentation/virt/kvm/devices/xics.rst
@@ -1,10 +1,31 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+=========================
XICS interrupt controller
+=========================
Device type supported: KVM_DEV_TYPE_XICS
Groups:
- KVM_DEV_XICS_SOURCES
- Attributes: One per interrupt source, indexed by the source number.
+ 1. KVM_DEV_XICS_GRP_SOURCES
+ Attributes:
+
+ One per interrupt source, indexed by the source number.
+ 2. KVM_DEV_XICS_GRP_CTRL
+ Attributes:
+
+ 2.1 KVM_DEV_XICS_NR_SERVERS (write only)
+
+ The kvm_device_attr.addr points to a __u32 value which is the number of
+ interrupt server numbers (ie, highest possible vcpu id plus one).
+
+ Errors:
+
+ ======= ==========================================
+ -EINVAL Value greater than KVM_MAX_VCPU_ID.
+ -EFAULT Invalid user pointer for attr->addr.
+ -EBUSY A vcpu is already connected to the device.
+ ======= ==========================================
This device emulates the XICS (eXternal Interrupt Controller
Specification) defined in PAPR. The XICS has a set of interrupt
@@ -38,29 +59,34 @@
Each source has 64 bits of state that can be read and written using
the KVM_GET_DEVICE_ATTR and KVM_SET_DEVICE_ATTR ioctls, specifying the
-KVM_DEV_XICS_SOURCES attribute group, with the attribute number being
+KVM_DEV_XICS_GRP_SOURCES attribute group, with the attribute number being
the interrupt source number. The 64 bit state word has the following
bitfields, starting from the least-significant end of the word:
* Destination (server number), 32 bits
+
This specifies where the interrupt should be sent, and is the
interrupt server number specified for the destination vcpu.
* Priority, 8 bits
+
This is the priority specified for this interrupt source, where 0 is
the highest priority and 255 is the lowest. An interrupt with a
priority of 255 will never be delivered.
* Level sensitive flag, 1 bit
+
This bit is 1 for a level-sensitive interrupt source, or 0 for
edge-sensitive (or MSI).
* Masked flag, 1 bit
+
This bit is set to 1 if the interrupt is masked (cannot be delivered
regardless of its priority), for example by the ibm,int-off RTAS
call, or 0 if it is not masked.
* Pending flag, 1 bit
+
This bit is 1 if the source has a pending interrupt, otherwise 0.
Only one XICS instance may be created per VM.
diff --git a/Documentation/virt/kvm/devices/xive.txt b/Documentation/virt/kvm/devices/xive.rst
similarity index 60%
rename from Documentation/virt/kvm/devices/xive.txt
rename to Documentation/virt/kvm/devices/xive.rst
index 9a24a45..8bdf3dc 100644
--- a/Documentation/virt/kvm/devices/xive.txt
+++ b/Documentation/virt/kvm/devices/xive.rst
@@ -1,8 +1,11 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+===========================================================
POWER9 eXternal Interrupt Virtualization Engine (XIVE Gen1)
-==========================================================
+===========================================================
Device types supported:
- KVM_DEV_TYPE_XIVE POWER9 XIVE Interrupt Controller generation 1
+ - KVM_DEV_TYPE_XIVE POWER9 XIVE Interrupt Controller generation 1
This device acts as a VM interrupt controller. It provides the KVM
interface to configure the interrupt sources of a VM in the underlying
@@ -64,64 +67,100 @@
* Groups:
- 1. KVM_DEV_XIVE_GRP_CTRL
- Provides global controls on the device
+1. KVM_DEV_XIVE_GRP_CTRL
+ Provides global controls on the device
+
Attributes:
1.1 KVM_DEV_XIVE_RESET (write only)
Resets the interrupt controller configuration for sources and event
queues. To be used by kexec and kdump.
+
Errors: none
1.2 KVM_DEV_XIVE_EQ_SYNC (write only)
Sync all the sources and queues and mark the EQ pages dirty. This
to make sure that a consistent memory state is captured when
migrating the VM.
+
Errors: none
- 2. KVM_DEV_XIVE_GRP_SOURCE (write only)
- Initializes a new source in the XIVE device and mask it.
+ 1.3 KVM_DEV_XIVE_NR_SERVERS (write only)
+ The kvm_device_attr.addr points to a __u32 value which is the number of
+ interrupt server numbers (ie, highest possible vcpu id plus one).
+
+ Errors:
+
+ ======= ==========================================
+ -EINVAL Value greater than KVM_MAX_VCPU_ID.
+ -EFAULT Invalid user pointer for attr->addr.
+ -EBUSY A vCPU is already connected to the device.
+ ======= ==========================================
+
+2. KVM_DEV_XIVE_GRP_SOURCE (write only)
+ Initializes a new source in the XIVE device and mask it.
+
Attributes:
Interrupt source number (64-bit)
- The kvm_device_attr.addr points to a __u64 value:
- bits: | 63 .... 2 | 1 | 0
- values: | unused | level | type
+
+ The kvm_device_attr.addr points to a __u64 value::
+
+ bits: | 63 .... 2 | 1 | 0
+ values: | unused | level | type
+
- type: 0:MSI 1:LSI
- level: assertion level in case of an LSI.
- Errors:
- -E2BIG: Interrupt source number is out of range
- -ENOMEM: Could not create a new source block
- -EFAULT: Invalid user pointer for attr->addr.
- -ENXIO: Could not allocate underlying HW interrupt
- 3. KVM_DEV_XIVE_GRP_SOURCE_CONFIG (write only)
- Configures source targeting
+ Errors:
+
+ ======= ==========================================
+ -E2BIG Interrupt source number is out of range
+ -ENOMEM Could not create a new source block
+ -EFAULT Invalid user pointer for attr->addr.
+ -ENXIO Could not allocate underlying HW interrupt
+ ======= ==========================================
+
+3. KVM_DEV_XIVE_GRP_SOURCE_CONFIG (write only)
+ Configures source targeting
+
Attributes:
Interrupt source number (64-bit)
- The kvm_device_attr.addr points to a __u64 value:
- bits: | 63 .... 33 | 32 | 31 .. 3 | 2 .. 0
- values: | eisn | mask | server | priority
+
+ The kvm_device_attr.addr points to a __u64 value::
+
+ bits: | 63 .... 33 | 32 | 31 .. 3 | 2 .. 0
+ values: | eisn | mask | server | priority
+
- priority: 0-7 interrupt priority level
- server: CPU number chosen to handle the interrupt
- mask: mask flag (unused)
- eisn: Effective Interrupt Source Number
- Errors:
- -ENOENT: Unknown source number
- -EINVAL: Not initialized source number
- -EINVAL: Invalid priority
- -EINVAL: Invalid CPU number.
- -EFAULT: Invalid user pointer for attr->addr.
- -ENXIO: CPU event queues not configured or configuration of the
- underlying HW interrupt failed
- -EBUSY: No CPU available to serve interrupt
- 4. KVM_DEV_XIVE_GRP_EQ_CONFIG (read-write)
- Configures an event queue of a CPU
+ Errors:
+
+ ======= =======================================================
+ -ENOENT Unknown source number
+ -EINVAL Not initialized source number
+ -EINVAL Invalid priority
+ -EINVAL Invalid CPU number.
+ -EFAULT Invalid user pointer for attr->addr.
+ -ENXIO CPU event queues not configured or configuration of the
+ underlying HW interrupt failed
+ -EBUSY No CPU available to serve interrupt
+ ======= =======================================================
+
+4. KVM_DEV_XIVE_GRP_EQ_CONFIG (read-write)
+ Configures an event queue of a CPU
+
Attributes:
EQ descriptor identifier (64-bit)
- The EQ descriptor identifier is a tuple (server, priority) :
- bits: | 63 .... 32 | 31 .. 3 | 2 .. 0
- values: | unused | server | priority
- The kvm_device_attr.addr points to :
+
+ The EQ descriptor identifier is a tuple (server, priority)::
+
+ bits: | 63 .... 32 | 31 .. 3 | 2 .. 0
+ values: | unused | server | priority
+
+ The kvm_device_attr.addr points to::
+
struct kvm_ppc_xive_eq {
__u32 flags;
__u32 qshift;
@@ -130,8 +169,9 @@
__u32 qindex;
__u8 pad[40];
};
+
- flags: queue flags
- KVM_XIVE_EQ_ALWAYS_NOTIFY (required)
+ KVM_XIVE_EQ_ALWAYS_NOTIFY (required)
forces notification without using the coalescing mechanism
provided by the XIVE END ESBs.
- qshift: queue size (power of 2)
@@ -139,22 +179,31 @@
- qtoggle: current queue toggle bit
- qindex: current queue index
- pad: reserved for future use
- Errors:
- -ENOENT: Invalid CPU number
- -EINVAL: Invalid priority
- -EINVAL: Invalid flags
- -EINVAL: Invalid queue size
- -EINVAL: Invalid queue address
- -EFAULT: Invalid user pointer for attr->addr.
- -EIO: Configuration of the underlying HW failed
- 5. KVM_DEV_XIVE_GRP_SOURCE_SYNC (write only)
- Synchronize the source to flush event notifications
+ Errors:
+
+ ======= =========================================
+ -ENOENT Invalid CPU number
+ -EINVAL Invalid priority
+ -EINVAL Invalid flags
+ -EINVAL Invalid queue size
+ -EINVAL Invalid queue address
+ -EFAULT Invalid user pointer for attr->addr.
+ -EIO Configuration of the underlying HW failed
+ ======= =========================================
+
+5. KVM_DEV_XIVE_GRP_SOURCE_SYNC (write only)
+ Synchronize the source to flush event notifications
+
Attributes:
Interrupt source number (64-bit)
+
Errors:
- -ENOENT: Unknown source number
- -EINVAL: Not initialized source number
+
+ ======= =============================
+ -ENOENT Unknown source number
+ -EINVAL Not initialized source number
+ ======= =============================
* VCPU state
@@ -167,11 +216,12 @@
as it synthesizes the priorities of the pending interrupts. We
capture a bit more to report debug information.
- KVM_REG_PPC_VP_STATE (2 * 64bits)
- bits: | 63 .... 32 | 31 .... 0 |
- values: | TIMA word0 | TIMA word1 |
- bits: | 127 .......... 64 |
- values: | unused |
+ KVM_REG_PPC_VP_STATE (2 * 64bits)::
+
+ bits: | 63 .... 32 | 31 .... 0 |
+ values: | TIMA word0 | TIMA word1 |
+ bits: | 127 .......... 64 |
+ values: | unused |
* Migration:
@@ -188,7 +238,7 @@
3. Capture the state of the source targeting, the EQs configuration
and the state of thread interrupt context registers.
- Restore is similar :
+ Restore is similar:
1. Restore the EQ configuration. As targeting depends on it.
2. Restore targeting
diff --git a/Documentation/virt/kvm/halt-polling.txt b/Documentation/virt/kvm/halt-polling.rst
similarity index 64%
rename from Documentation/virt/kvm/halt-polling.txt
rename to Documentation/virt/kvm/halt-polling.rst
index 4f791b1..4922e4a 100644
--- a/Documentation/virt/kvm/halt-polling.txt
+++ b/Documentation/virt/kvm/halt-polling.rst
@@ -1,3 +1,6 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+===========================
The KVM halt polling system
===========================
@@ -68,7 +71,8 @@
which come at an approximately constant rate, otherwise there will be constant
adjustment of the polling interval.
-[0] total block time: the time between when the halt polling function is
+[0] total block time:
+ the time between when the halt polling function is
invoked and a wakeup source received (irrespective of
whether the scheduler is invoked within that function).
@@ -81,31 +85,32 @@
parameters in virt/kvm/kvm_main.c, or arch/powerpc/kvm/book3s_hv.c in the
powerpc kvm-hv case.
-Module Parameter | Description | Default Value
---------------------------------------------------------------------------------
-halt_poll_ns | The global max polling | KVM_HALT_POLL_NS_DEFAULT
- | interval which defines |
- | the ceiling value of the |
- | polling interval for | (per arch value)
- | each vcpu. |
---------------------------------------------------------------------------------
-halt_poll_ns_grow | The value by which the | 2
- | halt polling interval is |
- | multiplied in the |
- | grow_halt_poll_ns() |
- | function. |
---------------------------------------------------------------------------------
-halt_poll_ns_grow_start | The initial value to grow | 10000
- | to from zero in the |
- | grow_halt_poll_ns() |
- | function. |
---------------------------------------------------------------------------------
-halt_poll_ns_shrink | The value by which the | 0
- | halt polling interval is |
- | divided in the |
- | shrink_halt_poll_ns() |
- | function. |
---------------------------------------------------------------------------------
++-----------------------+---------------------------+-------------------------+
+|Module Parameter | Description | Default Value |
++-----------------------+---------------------------+-------------------------+
+|halt_poll_ns | The global max polling | KVM_HALT_POLL_NS_DEFAULT|
+| | interval which defines | |
+| | the ceiling value of the | |
+| | polling interval for | (per arch value) |
+| | each vcpu. | |
++-----------------------+---------------------------+-------------------------+
+|halt_poll_ns_grow | The value by which the | 2 |
+| | halt polling interval is | |
+| | multiplied in the | |
+| | grow_halt_poll_ns() | |
+| | function. | |
++-----------------------+---------------------------+-------------------------+
+|halt_poll_ns_grow_start| The initial value to grow | 10000 |
+| | to from zero in the | |
+| | grow_halt_poll_ns() | |
+| | function. | |
++-----------------------+---------------------------+-------------------------+
+|halt_poll_ns_shrink | The value by which the | 0 |
+| | halt polling interval is | |
+| | divided in the | |
+| | shrink_halt_poll_ns() | |
+| | function. | |
++-----------------------+---------------------------+-------------------------+
These module parameters can be set from the debugfs files in:
@@ -117,20 +122,19 @@
Further Notes
=============
-- Care should be taken when setting the halt_poll_ns module parameter as a
-large value has the potential to drive the cpu usage to 100% on a machine which
-would be almost entirely idle otherwise. This is because even if a guest has
-wakeups during which very little work is done and which are quite far apart, if
-the period is shorter than the global max polling interval (halt_poll_ns) then
-the host will always poll for the entire block time and thus cpu utilisation
-will go to 100%.
+- Care should be taken when setting the halt_poll_ns module parameter as a large value
+ has the potential to drive the cpu usage to 100% on a machine which would be almost
+ entirely idle otherwise. This is because even if a guest has wakeups during which very
+ little work is done and which are quite far apart, if the period is shorter than the
+ global max polling interval (halt_poll_ns) then the host will always poll for the
+ entire block time and thus cpu utilisation will go to 100%.
-- Halt polling essentially presents a trade off between power usage and latency
-and the module parameters should be used to tune the affinity for this. Idle
-cpu time is essentially converted to host kernel time with the aim of decreasing
-latency when entering the guest.
+- Halt polling essentially presents a trade off between power usage and latency and
+ the module parameters should be used to tune the affinity for this. Idle cpu time is
+ essentially converted to host kernel time with the aim of decreasing latency when
+ entering the guest.
-- Halt polling will only be conducted by the host when no other tasks are
-runnable on that cpu, otherwise the polling will cease immediately and
-schedule will be invoked to allow that other task to run. Thus this doesn't
-allow a guest to denial of service the cpu.
+- Halt polling will only be conducted by the host when no other tasks are runnable on
+ that cpu, otherwise the polling will cease immediately and schedule will be invoked to
+ allow that other task to run. Thus this doesn't allow a guest to denial of service the
+ cpu.
diff --git a/Documentation/virt/kvm/hypercalls.rst b/Documentation/virt/kvm/hypercalls.rst
new file mode 100644
index 0000000..ed4fddd
--- /dev/null
+++ b/Documentation/virt/kvm/hypercalls.rst
@@ -0,0 +1,171 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+===================
+Linux KVM Hypercall
+===================
+
+X86:
+ KVM Hypercalls have a three-byte sequence of either the vmcall or the vmmcall
+ instruction. The hypervisor can replace it with instructions that are
+ guaranteed to be supported.
+
+ Up to four arguments may be passed in rbx, rcx, rdx, and rsi respectively.
+ The hypercall number should be placed in rax and the return value will be
+ placed in rax. No other registers will be clobbered unless explicitly stated
+ by the particular hypercall.
+
+S390:
+ R2-R7 are used for parameters 1-6. In addition, R1 is used for hypercall
+ number. The return value is written to R2.
+
+ S390 uses diagnose instruction as hypercall (0x500) along with hypercall
+ number in R1.
+
+ For further information on the S390 diagnose call as supported by KVM,
+ refer to Documentation/virt/kvm/s390-diag.rst.
+
+PowerPC:
+ It uses R3-R10 and hypercall number in R11. R4-R11 are used as output registers.
+ Return value is placed in R3.
+
+ KVM hypercalls uses 4 byte opcode, that are patched with 'hypercall-instructions'
+ property inside the device tree's /hypervisor node.
+ For more information refer to Documentation/virt/kvm/ppc-pv.rst
+
+MIPS:
+ KVM hypercalls use the HYPCALL instruction with code 0 and the hypercall
+ number in $2 (v0). Up to four arguments may be placed in $4-$7 (a0-a3) and
+ the return value is placed in $2 (v0).
+
+KVM Hypercalls Documentation
+============================
+
+The template for each hypercall is:
+1. Hypercall name.
+2. Architecture(s)
+3. Status (deprecated, obsolete, active)
+4. Purpose
+
+1. KVM_HC_VAPIC_POLL_IRQ
+------------------------
+
+:Architecture: x86
+:Status: active
+:Purpose: Trigger guest exit so that the host can check for pending
+ interrupts on reentry.
+
+2. KVM_HC_MMU_OP
+----------------
+
+:Architecture: x86
+:Status: deprecated.
+:Purpose: Support MMU operations such as writing to PTE,
+ flushing TLB, release PT.
+
+3. KVM_HC_FEATURES
+------------------
+
+:Architecture: PPC
+:Status: active
+:Purpose: Expose hypercall availability to the guest. On x86 platforms, cpuid
+ used to enumerate which hypercalls are available. On PPC, either
+ device tree based lookup ( which is also what EPAPR dictates)
+ OR KVM specific enumeration mechanism (which is this hypercall)
+ can be used.
+
+4. KVM_HC_PPC_MAP_MAGIC_PAGE
+----------------------------
+
+:Architecture: PPC
+:Status: active
+:Purpose: To enable communication between the hypervisor and guest there is a
+ shared page that contains parts of supervisor visible register state.
+ The guest can map this shared page to access its supervisor register
+ through memory using this hypercall.
+
+5. KVM_HC_KICK_CPU
+------------------
+
+:Architecture: x86
+:Status: active
+:Purpose: Hypercall used to wakeup a vcpu from HLT state
+:Usage example:
+ A vcpu of a paravirtualized guest that is busywaiting in guest
+ kernel mode for an event to occur (ex: a spinlock to become available) can
+ execute HLT instruction once it has busy-waited for more than a threshold
+ time-interval. Execution of HLT instruction would cause the hypervisor to put
+ the vcpu to sleep until occurrence of an appropriate event. Another vcpu of the
+ same guest can wakeup the sleeping vcpu by issuing KVM_HC_KICK_CPU hypercall,
+ specifying APIC ID (a1) of the vcpu to be woken up. An additional argument (a0)
+ is used in the hypercall for future use.
+
+
+6. KVM_HC_CLOCK_PAIRING
+-----------------------
+:Architecture: x86
+:Status: active
+:Purpose: Hypercall used to synchronize host and guest clocks.
+
+Usage:
+
+a0: guest physical address where host copies
+"struct kvm_clock_offset" structure.
+
+a1: clock_type, ATM only KVM_CLOCK_PAIRING_WALLCLOCK (0)
+is supported (corresponding to the host's CLOCK_REALTIME clock).
+
+ ::
+
+ struct kvm_clock_pairing {
+ __s64 sec;
+ __s64 nsec;
+ __u64 tsc;
+ __u32 flags;
+ __u32 pad[9];
+ };
+
+ Where:
+ * sec: seconds from clock_type clock.
+ * nsec: nanoseconds from clock_type clock.
+ * tsc: guest TSC value used to calculate sec/nsec pair
+ * flags: flags, unused (0) at the moment.
+
+The hypercall lets a guest compute a precise timestamp across
+host and guest. The guest can use the returned TSC value to
+compute the CLOCK_REALTIME for its clock, at the same instant.
+
+Returns KVM_EOPNOTSUPP if the host does not use TSC clocksource,
+or if clock type is different than KVM_CLOCK_PAIRING_WALLCLOCK.
+
+6. KVM_HC_SEND_IPI
+------------------
+
+:Architecture: x86
+:Status: active
+:Purpose: Send IPIs to multiple vCPUs.
+
+- a0: lower part of the bitmap of destination APIC IDs
+- a1: higher part of the bitmap of destination APIC IDs
+- a2: the lowest APIC ID in bitmap
+- a3: APIC ICR
+
+The hypercall lets a guest send multicast IPIs, with at most 128
+128 destinations per hypercall in 64-bit mode and 64 vCPUs per
+hypercall in 32-bit mode. The destinations are represented by a
+bitmap contained in the first two arguments (a0 and a1). Bit 0 of
+a0 corresponds to the APIC ID in the third argument (a2), bit 1
+corresponds to the APIC ID a2+1, and so on.
+
+Returns the number of CPUs to which the IPIs were delivered successfully.
+
+7. KVM_HC_SCHED_YIELD
+---------------------
+
+:Architecture: x86
+:Status: active
+:Purpose: Hypercall used to yield if the IPI target vCPU is preempted
+
+a0: destination APIC ID
+
+:Usage example: When sending a call-function IPI-many to vCPUs, yield if
+ any of the IPI target vCPUs was preempted.
diff --git a/Documentation/virt/kvm/hypercalls.txt b/Documentation/virt/kvm/hypercalls.txt
deleted file mode 100644
index 5f6d291..0000000
--- a/Documentation/virt/kvm/hypercalls.txt
+++ /dev/null
@@ -1,154 +0,0 @@
-Linux KVM Hypercall:
-===================
-X86:
- KVM Hypercalls have a three-byte sequence of either the vmcall or the vmmcall
- instruction. The hypervisor can replace it with instructions that are
- guaranteed to be supported.
-
- Up to four arguments may be passed in rbx, rcx, rdx, and rsi respectively.
- The hypercall number should be placed in rax and the return value will be
- placed in rax. No other registers will be clobbered unless explicitly stated
- by the particular hypercall.
-
-S390:
- R2-R7 are used for parameters 1-6. In addition, R1 is used for hypercall
- number. The return value is written to R2.
-
- S390 uses diagnose instruction as hypercall (0x500) along with hypercall
- number in R1.
-
- For further information on the S390 diagnose call as supported by KVM,
- refer to Documentation/virt/kvm/s390-diag.txt.
-
- PowerPC:
- It uses R3-R10 and hypercall number in R11. R4-R11 are used as output registers.
- Return value is placed in R3.
-
- KVM hypercalls uses 4 byte opcode, that are patched with 'hypercall-instructions'
- property inside the device tree's /hypervisor node.
- For more information refer to Documentation/virt/kvm/ppc-pv.txt
-
-MIPS:
- KVM hypercalls use the HYPCALL instruction with code 0 and the hypercall
- number in $2 (v0). Up to four arguments may be placed in $4-$7 (a0-a3) and
- the return value is placed in $2 (v0).
-
-KVM Hypercalls Documentation
-===========================
-The template for each hypercall is:
-1. Hypercall name.
-2. Architecture(s)
-3. Status (deprecated, obsolete, active)
-4. Purpose
-
-1. KVM_HC_VAPIC_POLL_IRQ
-------------------------
-Architecture: x86
-Status: active
-Purpose: Trigger guest exit so that the host can check for pending
-interrupts on reentry.
-
-2. KVM_HC_MMU_OP
-------------------------
-Architecture: x86
-Status: deprecated.
-Purpose: Support MMU operations such as writing to PTE,
-flushing TLB, release PT.
-
-3. KVM_HC_FEATURES
-------------------------
-Architecture: PPC
-Status: active
-Purpose: Expose hypercall availability to the guest. On x86 platforms, cpuid
-used to enumerate which hypercalls are available. On PPC, either device tree
-based lookup ( which is also what EPAPR dictates) OR KVM specific enumeration
-mechanism (which is this hypercall) can be used.
-
-4. KVM_HC_PPC_MAP_MAGIC_PAGE
-------------------------
-Architecture: PPC
-Status: active
-Purpose: To enable communication between the hypervisor and guest there is a
-shared page that contains parts of supervisor visible register state.
-The guest can map this shared page to access its supervisor register through
-memory using this hypercall.
-
-5. KVM_HC_KICK_CPU
-------------------------
-Architecture: x86
-Status: active
-Purpose: Hypercall used to wakeup a vcpu from HLT state
-Usage example : A vcpu of a paravirtualized guest that is busywaiting in guest
-kernel mode for an event to occur (ex: a spinlock to become available) can
-execute HLT instruction once it has busy-waited for more than a threshold
-time-interval. Execution of HLT instruction would cause the hypervisor to put
-the vcpu to sleep until occurrence of an appropriate event. Another vcpu of the
-same guest can wakeup the sleeping vcpu by issuing KVM_HC_KICK_CPU hypercall,
-specifying APIC ID (a1) of the vcpu to be woken up. An additional argument (a0)
-is used in the hypercall for future use.
-
-
-6. KVM_HC_CLOCK_PAIRING
-------------------------
-Architecture: x86
-Status: active
-Purpose: Hypercall used to synchronize host and guest clocks.
-Usage:
-
-a0: guest physical address where host copies
-"struct kvm_clock_offset" structure.
-
-a1: clock_type, ATM only KVM_CLOCK_PAIRING_WALLCLOCK (0)
-is supported (corresponding to the host's CLOCK_REALTIME clock).
-
- struct kvm_clock_pairing {
- __s64 sec;
- __s64 nsec;
- __u64 tsc;
- __u32 flags;
- __u32 pad[9];
- };
-
- Where:
- * sec: seconds from clock_type clock.
- * nsec: nanoseconds from clock_type clock.
- * tsc: guest TSC value used to calculate sec/nsec pair
- * flags: flags, unused (0) at the moment.
-
-The hypercall lets a guest compute a precise timestamp across
-host and guest. The guest can use the returned TSC value to
-compute the CLOCK_REALTIME for its clock, at the same instant.
-
-Returns KVM_EOPNOTSUPP if the host does not use TSC clocksource,
-or if clock type is different than KVM_CLOCK_PAIRING_WALLCLOCK.
-
-6. KVM_HC_SEND_IPI
-------------------------
-Architecture: x86
-Status: active
-Purpose: Send IPIs to multiple vCPUs.
-
-a0: lower part of the bitmap of destination APIC IDs
-a1: higher part of the bitmap of destination APIC IDs
-a2: the lowest APIC ID in bitmap
-a3: APIC ICR
-
-The hypercall lets a guest send multicast IPIs, with at most 128
-128 destinations per hypercall in 64-bit mode and 64 vCPUs per
-hypercall in 32-bit mode. The destinations are represented by a
-bitmap contained in the first two arguments (a0 and a1). Bit 0 of
-a0 corresponds to the APIC ID in the third argument (a2), bit 1
-corresponds to the APIC ID a2+1, and so on.
-
-Returns the number of CPUs to which the IPIs were delivered successfully.
-
-7. KVM_HC_SCHED_YIELD
-------------------------
-Architecture: x86
-Status: active
-Purpose: Hypercall used to yield if the IPI target vCPU is preempted
-
-a0: destination APIC ID
-
-Usage example: When sending a call-function IPI-many to vCPUs, yield if
-any of the IPI target vCPUs was preempted.
diff --git a/Documentation/virt/kvm/index.rst b/Documentation/virt/kvm/index.rst
index ada224a..b6833c7 100644
--- a/Documentation/virt/kvm/index.rst
+++ b/Documentation/virt/kvm/index.rst
@@ -7,6 +7,26 @@
.. toctree::
:maxdepth: 2
+ api
amd-memory-encryption
cpuid
+ halt-polling
+ hypercalls
+ locking
+ mmu
+ msr
+ nested-vmx
+ ppc-pv
+ s390-diag
+ s390-pv
+ s390-pv-boot
+ timekeeping
vcpu-requests
+
+ review-checklist
+
+ arm/index
+
+ devices/index
+
+ running-nested-guests
diff --git a/Documentation/virt/kvm/locking.rst b/Documentation/virt/kvm/locking.rst
new file mode 100644
index 0000000..b21a34c
--- /dev/null
+++ b/Documentation/virt/kvm/locking.rst
@@ -0,0 +1,242 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+=================
+KVM Lock Overview
+=================
+
+1. Acquisition Orders
+---------------------
+
+The acquisition orders for mutexes are as follows:
+
+- kvm->lock is taken outside vcpu->mutex
+
+- kvm->lock is taken outside kvm->slots_lock and kvm->irq_lock
+
+- kvm->slots_lock is taken outside kvm->irq_lock, though acquiring
+ them together is quite rare.
+
+On x86, vcpu->mutex is taken outside kvm->arch.hyperv.hv_lock.
+
+Everything else is a leaf: no other lock is taken inside the critical
+sections.
+
+2. Exception
+------------
+
+Fast page fault:
+
+Fast page fault is the fast path which fixes the guest page fault out of
+the mmu-lock on x86. Currently, the page fault can be fast in one of the
+following two cases:
+
+1. Access Tracking: The SPTE is not present, but it is marked for access
+ tracking i.e. the SPTE_SPECIAL_MASK is set. That means we need to
+ restore the saved R/X bits. This is described in more detail later below.
+
+2. Write-Protection: The SPTE is present and the fault is
+ caused by write-protect. That means we just need to change the W bit of
+ the spte.
+
+What we use to avoid all the race is the SPTE_HOST_WRITEABLE bit and
+SPTE_MMU_WRITEABLE bit on the spte:
+
+- SPTE_HOST_WRITEABLE means the gfn is writable on host.
+- SPTE_MMU_WRITEABLE means the gfn is writable on mmu. The bit is set when
+ the gfn is writable on guest mmu and it is not write-protected by shadow
+ page write-protection.
+
+On fast page fault path, we will use cmpxchg to atomically set the spte W
+bit if spte.SPTE_HOST_WRITEABLE = 1 and spte.SPTE_WRITE_PROTECT = 1, or
+restore the saved R/X bits if VMX_EPT_TRACK_ACCESS mask is set, or both. This
+is safe because whenever changing these bits can be detected by cmpxchg.
+
+But we need carefully check these cases:
+
+1) The mapping from gfn to pfn
+
+The mapping from gfn to pfn may be changed since we can only ensure the pfn
+is not changed during cmpxchg. This is a ABA problem, for example, below case
+will happen:
+
++------------------------------------------------------------------------+
+| At the beginning:: |
+| |
+| gpte = gfn1 |
+| gfn1 is mapped to pfn1 on host |
+| spte is the shadow page table entry corresponding with gpte and |
+| spte = pfn1 |
++------------------------------------------------------------------------+
+| On fast page fault path: |
++------------------------------------+-----------------------------------+
+| CPU 0: | CPU 1: |
++------------------------------------+-----------------------------------+
+| :: | |
+| | |
+| old_spte = *spte; | |
++------------------------------------+-----------------------------------+
+| | pfn1 is swapped out:: |
+| | |
+| | spte = 0; |
+| | |
+| | pfn1 is re-alloced for gfn2. |
+| | |
+| | gpte is changed to point to |
+| | gfn2 by the guest:: |
+| | |
+| | spte = pfn1; |
++------------------------------------+-----------------------------------+
+| :: |
+| |
+| if (cmpxchg(spte, old_spte, old_spte+W) |
+| mark_page_dirty(vcpu->kvm, gfn1) |
+| OOPS!!! |
++------------------------------------------------------------------------+
+
+We dirty-log for gfn1, that means gfn2 is lost in dirty-bitmap.
+
+For direct sp, we can easily avoid it since the spte of direct sp is fixed
+to gfn. For indirect sp, we disabled fast page fault for simplicity.
+
+A solution for indirect sp could be to pin the gfn, for example via
+kvm_vcpu_gfn_to_pfn_atomic, before the cmpxchg. After the pinning:
+
+- We have held the refcount of pfn that means the pfn can not be freed and
+ be reused for another gfn.
+- The pfn is writable and therefore it cannot be shared between different gfns
+ by KSM.
+
+Then, we can ensure the dirty bitmaps is correctly set for a gfn.
+
+2) Dirty bit tracking
+
+In the origin code, the spte can be fast updated (non-atomically) if the
+spte is read-only and the Accessed bit has already been set since the
+Accessed bit and Dirty bit can not be lost.
+
+But it is not true after fast page fault since the spte can be marked
+writable between reading spte and updating spte. Like below case:
+
++------------------------------------------------------------------------+
+| At the beginning:: |
+| |
+| spte.W = 0 |
+| spte.Accessed = 1 |
++------------------------------------+-----------------------------------+
+| CPU 0: | CPU 1: |
++------------------------------------+-----------------------------------+
+| In mmu_spte_clear_track_bits():: | |
+| | |
+| old_spte = *spte; | |
+| | |
+| | |
+| /* 'if' condition is satisfied. */| |
+| if (old_spte.Accessed == 1 && | |
+| old_spte.W == 0) | |
+| spte = 0ull; | |
++------------------------------------+-----------------------------------+
+| | on fast page fault path:: |
+| | |
+| | spte.W = 1 |
+| | |
+| | memory write on the spte:: |
+| | |
+| | spte.Dirty = 1 |
++------------------------------------+-----------------------------------+
+| :: | |
+| | |
+| else | |
+| old_spte = xchg(spte, 0ull) | |
+| if (old_spte.Accessed == 1) | |
+| kvm_set_pfn_accessed(spte.pfn);| |
+| if (old_spte.Dirty == 1) | |
+| kvm_set_pfn_dirty(spte.pfn); | |
+| OOPS!!! | |
++------------------------------------+-----------------------------------+
+
+The Dirty bit is lost in this case.
+
+In order to avoid this kind of issue, we always treat the spte as "volatile"
+if it can be updated out of mmu-lock, see spte_has_volatile_bits(), it means,
+the spte is always atomically updated in this case.
+
+3) flush tlbs due to spte updated
+
+If the spte is updated from writable to readonly, we should flush all TLBs,
+otherwise rmap_write_protect will find a read-only spte, even though the
+writable spte might be cached on a CPU's TLB.
+
+As mentioned before, the spte can be updated to writable out of mmu-lock on
+fast page fault path, in order to easily audit the path, we see if TLBs need
+be flushed caused by this reason in mmu_spte_update() since this is a common
+function to update spte (present -> present).
+
+Since the spte is "volatile" if it can be updated out of mmu-lock, we always
+atomically update the spte, the race caused by fast page fault can be avoided,
+See the comments in spte_has_volatile_bits() and mmu_spte_update().
+
+Lockless Access Tracking:
+
+This is used for Intel CPUs that are using EPT but do not support the EPT A/D
+bits. In this case, when the KVM MMU notifier is called to track accesses to a
+page (via kvm_mmu_notifier_clear_flush_young), it marks the PTE as not-present
+by clearing the RWX bits in the PTE and storing the original R & X bits in
+some unused/ignored bits. In addition, the SPTE_SPECIAL_MASK is also set on the
+PTE (using the ignored bit 62). When the VM tries to access the page later on,
+a fault is generated and the fast page fault mechanism described above is used
+to atomically restore the PTE to a Present state. The W bit is not saved when
+the PTE is marked for access tracking and during restoration to the Present
+state, the W bit is set depending on whether or not it was a write access. If
+it wasn't, then the W bit will remain clear until a write access happens, at
+which time it will be set using the Dirty tracking mechanism described above.
+
+3. Reference
+------------
+
+:Name: kvm_lock
+:Type: mutex
+:Arch: any
+:Protects: - vm_list
+
+:Name: kvm_count_lock
+:Type: raw_spinlock_t
+:Arch: any
+:Protects: - hardware virtualization enable/disable
+:Comment: 'raw' because hardware enabling/disabling must be atomic /wrt
+ migration.
+
+:Name: kvm_arch::tsc_write_lock
+:Type: raw_spinlock
+:Arch: x86
+:Protects: - kvm_arch::{last_tsc_write,last_tsc_nsec,last_tsc_offset}
+ - tsc offset in vmcb
+:Comment: 'raw' because updating the tsc offsets must not be preempted.
+
+:Name: kvm->mmu_lock
+:Type: spinlock_t
+:Arch: any
+:Protects: -shadow page/shadow tlb entry
+:Comment: it is a spinlock since it is used in mmu notifier.
+
+:Name: kvm->srcu
+:Type: srcu lock
+:Arch: any
+:Protects: - kvm->memslots
+ - kvm->buses
+:Comment: The srcu read lock must be held while accessing memslots (e.g.
+ when using gfn_to_* functions) and while accessing in-kernel
+ MMIO/PIO address->device structure mapping (kvm->buses).
+ The srcu index can be stored in kvm_vcpu->srcu_idx per vcpu
+ if it is needed by multiple functions.
+
+:Name: blocked_vcpu_on_cpu_lock
+:Type: spinlock_t
+:Arch: x86
+:Protects: blocked_vcpu_on_cpu
+:Comment: This is a per-CPU lock and it is used for VT-d posted-interrupts.
+ When VT-d posted-interrupts is supported and the VM has assigned
+ devices, we put the blocked vCPU on the list blocked_vcpu_on_cpu
+ protected by blocked_vcpu_on_cpu_lock, when VT-d hardware issues
+ wakeup notification event since external interrupts from the
+ assigned devices happens, we will find the vCPU on the list to
+ wakeup.
diff --git a/Documentation/virt/kvm/locking.txt b/Documentation/virt/kvm/locking.txt
deleted file mode 100644
index 635cd6e..0000000
--- a/Documentation/virt/kvm/locking.txt
+++ /dev/null
@@ -1,215 +0,0 @@
-KVM Lock Overview
-=================
-
-1. Acquisition Orders
----------------------
-
-The acquisition orders for mutexes are as follows:
-
-- kvm->lock is taken outside vcpu->mutex
-
-- kvm->lock is taken outside kvm->slots_lock and kvm->irq_lock
-
-- kvm->slots_lock is taken outside kvm->irq_lock, though acquiring
- them together is quite rare.
-
-On x86, vcpu->mutex is taken outside kvm->arch.hyperv.hv_lock.
-
-Everything else is a leaf: no other lock is taken inside the critical
-sections.
-
-2: Exception
-------------
-
-Fast page fault:
-
-Fast page fault is the fast path which fixes the guest page fault out of
-the mmu-lock on x86. Currently, the page fault can be fast in one of the
-following two cases:
-
-1. Access Tracking: The SPTE is not present, but it is marked for access
-tracking i.e. the SPTE_SPECIAL_MASK is set. That means we need to
-restore the saved R/X bits. This is described in more detail later below.
-
-2. Write-Protection: The SPTE is present and the fault is
-caused by write-protect. That means we just need to change the W bit of the
-spte.
-
-What we use to avoid all the race is the SPTE_HOST_WRITEABLE bit and
-SPTE_MMU_WRITEABLE bit on the spte:
-- SPTE_HOST_WRITEABLE means the gfn is writable on host.
-- SPTE_MMU_WRITEABLE means the gfn is writable on mmu. The bit is set when
- the gfn is writable on guest mmu and it is not write-protected by shadow
- page write-protection.
-
-On fast page fault path, we will use cmpxchg to atomically set the spte W
-bit if spte.SPTE_HOST_WRITEABLE = 1 and spte.SPTE_WRITE_PROTECT = 1, or
-restore the saved R/X bits if VMX_EPT_TRACK_ACCESS mask is set, or both. This
-is safe because whenever changing these bits can be detected by cmpxchg.
-
-But we need carefully check these cases:
-1): The mapping from gfn to pfn
-The mapping from gfn to pfn may be changed since we can only ensure the pfn
-is not changed during cmpxchg. This is a ABA problem, for example, below case
-will happen:
-
-At the beginning:
-gpte = gfn1
-gfn1 is mapped to pfn1 on host
-spte is the shadow page table entry corresponding with gpte and
-spte = pfn1
-
- VCPU 0 VCPU0
-on fast page fault path:
-
- old_spte = *spte;
- pfn1 is swapped out:
- spte = 0;
-
- pfn1 is re-alloced for gfn2.
-
- gpte is changed to point to
- gfn2 by the guest:
- spte = pfn1;
-
- if (cmpxchg(spte, old_spte, old_spte+W)
- mark_page_dirty(vcpu->kvm, gfn1)
- OOPS!!!
-
-We dirty-log for gfn1, that means gfn2 is lost in dirty-bitmap.
-
-For direct sp, we can easily avoid it since the spte of direct sp is fixed
-to gfn. For indirect sp, before we do cmpxchg, we call gfn_to_pfn_atomic()
-to pin gfn to pfn, because after gfn_to_pfn_atomic():
-- We have held the refcount of pfn that means the pfn can not be freed and
- be reused for another gfn.
-- The pfn is writable that means it can not be shared between different gfns
- by KSM.
-
-Then, we can ensure the dirty bitmaps is correctly set for a gfn.
-
-Currently, to simplify the whole things, we disable fast page fault for
-indirect shadow page.
-
-2): Dirty bit tracking
-In the origin code, the spte can be fast updated (non-atomically) if the
-spte is read-only and the Accessed bit has already been set since the
-Accessed bit and Dirty bit can not be lost.
-
-But it is not true after fast page fault since the spte can be marked
-writable between reading spte and updating spte. Like below case:
-
-At the beginning:
-spte.W = 0
-spte.Accessed = 1
-
- VCPU 0 VCPU0
-In mmu_spte_clear_track_bits():
-
- old_spte = *spte;
-
- /* 'if' condition is satisfied. */
- if (old_spte.Accessed == 1 &&
- old_spte.W == 0)
- spte = 0ull;
- on fast page fault path:
- spte.W = 1
- memory write on the spte:
- spte.Dirty = 1
-
-
- else
- old_spte = xchg(spte, 0ull)
-
-
- if (old_spte.Accessed == 1)
- kvm_set_pfn_accessed(spte.pfn);
- if (old_spte.Dirty == 1)
- kvm_set_pfn_dirty(spte.pfn);
- OOPS!!!
-
-The Dirty bit is lost in this case.
-
-In order to avoid this kind of issue, we always treat the spte as "volatile"
-if it can be updated out of mmu-lock, see spte_has_volatile_bits(), it means,
-the spte is always atomically updated in this case.
-
-3): flush tlbs due to spte updated
-If the spte is updated from writable to readonly, we should flush all TLBs,
-otherwise rmap_write_protect will find a read-only spte, even though the
-writable spte might be cached on a CPU's TLB.
-
-As mentioned before, the spte can be updated to writable out of mmu-lock on
-fast page fault path, in order to easily audit the path, we see if TLBs need
-be flushed caused by this reason in mmu_spte_update() since this is a common
-function to update spte (present -> present).
-
-Since the spte is "volatile" if it can be updated out of mmu-lock, we always
-atomically update the spte, the race caused by fast page fault can be avoided,
-See the comments in spte_has_volatile_bits() and mmu_spte_update().
-
-Lockless Access Tracking:
-
-This is used for Intel CPUs that are using EPT but do not support the EPT A/D
-bits. In this case, when the KVM MMU notifier is called to track accesses to a
-page (via kvm_mmu_notifier_clear_flush_young), it marks the PTE as not-present
-by clearing the RWX bits in the PTE and storing the original R & X bits in
-some unused/ignored bits. In addition, the SPTE_SPECIAL_MASK is also set on the
-PTE (using the ignored bit 62). When the VM tries to access the page later on,
-a fault is generated and the fast page fault mechanism described above is used
-to atomically restore the PTE to a Present state. The W bit is not saved when
-the PTE is marked for access tracking and during restoration to the Present
-state, the W bit is set depending on whether or not it was a write access. If
-it wasn't, then the W bit will remain clear until a write access happens, at
-which time it will be set using the Dirty tracking mechanism described above.
-
-3. Reference
-------------
-
-Name: kvm_lock
-Type: mutex
-Arch: any
-Protects: - vm_list
-
-Name: kvm_count_lock
-Type: raw_spinlock_t
-Arch: any
-Protects: - hardware virtualization enable/disable
-Comment: 'raw' because hardware enabling/disabling must be atomic /wrt
- migration.
-
-Name: kvm_arch::tsc_write_lock
-Type: raw_spinlock
-Arch: x86
-Protects: - kvm_arch::{last_tsc_write,last_tsc_nsec,last_tsc_offset}
- - tsc offset in vmcb
-Comment: 'raw' because updating the tsc offsets must not be preempted.
-
-Name: kvm->mmu_lock
-Type: spinlock_t
-Arch: any
-Protects: -shadow page/shadow tlb entry
-Comment: it is a spinlock since it is used in mmu notifier.
-
-Name: kvm->srcu
-Type: srcu lock
-Arch: any
-Protects: - kvm->memslots
- - kvm->buses
-Comment: The srcu read lock must be held while accessing memslots (e.g.
- when using gfn_to_* functions) and while accessing in-kernel
- MMIO/PIO address->device structure mapping (kvm->buses).
- The srcu index can be stored in kvm_vcpu->srcu_idx per vcpu
- if it is needed by multiple functions.
-
-Name: blocked_vcpu_on_cpu_lock
-Type: spinlock_t
-Arch: x86
-Protects: blocked_vcpu_on_cpu
-Comment: This is a per-CPU lock and it is used for VT-d posted-interrupts.
- When VT-d posted-interrupts is supported and the VM has assigned
- devices, we put the blocked vCPU on the list blocked_vcpu_on_cpu
- protected by blocked_vcpu_on_cpu_lock, when VT-d hardware issues
- wakeup notification event since external interrupts from the
- assigned devices happens, we will find the vCPU on the list to
- wakeup.
diff --git a/Documentation/virt/kvm/mmu.txt b/Documentation/virt/kvm/mmu.rst
similarity index 93%
rename from Documentation/virt/kvm/mmu.txt
rename to Documentation/virt/kvm/mmu.rst
index da1ac6a..20d85da 100644
--- a/Documentation/virt/kvm/mmu.txt
+++ b/Documentation/virt/kvm/mmu.rst
@@ -1,3 +1,6 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+======================
The x86 kvm shadow mmu
======================
@@ -7,27 +10,37 @@
The mmu code attempts to satisfy the following requirements:
-- correctness: the guest should not be able to determine that it is running
+- correctness:
+ the guest should not be able to determine that it is running
on an emulated mmu except for timing (we attempt to comply
with the specification, not emulate the characteristics of
a particular implementation such as tlb size)
-- security: the guest must not be able to touch host memory not assigned
+- security:
+ the guest must not be able to touch host memory not assigned
to it
-- performance: minimize the performance penalty imposed by the mmu
-- scaling: need to scale to large memory and large vcpu guests
-- hardware: support the full range of x86 virtualization hardware
-- integration: Linux memory management code must be in control of guest memory
+- performance:
+ minimize the performance penalty imposed by the mmu
+- scaling:
+ need to scale to large memory and large vcpu guests
+- hardware:
+ support the full range of x86 virtualization hardware
+- integration:
+ Linux memory management code must be in control of guest memory
so that swapping, page migration, page merging, transparent
hugepages, and similar features work without change
-- dirty tracking: report writes to guest memory to enable live migration
+- dirty tracking:
+ report writes to guest memory to enable live migration
and framebuffer-based displays
-- footprint: keep the amount of pinned kernel memory low (most memory
+- footprint:
+ keep the amount of pinned kernel memory low (most memory
should be shrinkable)
-- reliability: avoid multipage or GFP_ATOMIC allocations
+- reliability:
+ avoid multipage or GFP_ATOMIC allocations
Acronyms
========
+==== ====================================================================
pfn host page frame number
hpa host physical address
hva host virtual address
@@ -41,6 +54,7 @@
gpte guest pte (referring to gfns)
spte shadow pte (referring to pfns)
tdp two dimensional paging (vendor neutral term for NPT and EPT)
+==== ====================================================================
Virtual and real hardware supported
===================================
@@ -90,11 +104,13 @@
The mmu is driven by events, some from the guest, some from the host.
Guest generated events:
+
- writes to control registers (especially cr3)
- invlpg/invlpga instruction execution
- access to missing or protected translations
Host generated events:
+
- changes in the gpa->hpa translation (either through gpa->hva changes or
through hva->hpa changes)
- memory pressure (the shrinker)
@@ -117,16 +133,19 @@
The following table shows translations encoded by leaf ptes, with higher-level
translations in parentheses:
- Non-nested guests:
+ Non-nested guests::
+
nonpaging: gpa->hpa
paging: gva->gpa->hpa
paging, tdp: (gva->)gpa->hpa
- Nested guests:
+
+ Nested guests::
+
non-tdp: ngva->gpa->hpa (*)
tdp: (ngva->)ngpa->gpa->hpa
-(*) the guest hypervisor will encode the ngva->gpa translation into its page
- tables if npt is not present
+ (*) the guest hypervisor will encode the ngva->gpa translation into its page
+ tables if npt is not present
Shadow pages contain the following information:
role.level:
@@ -291,28 +310,41 @@
- if the RSV bit of the error code is set, the page fault is caused by guest
accessing MMIO and cached MMIO information is available.
+
- walk shadow page table
- check for valid generation number in the spte (see "Fast invalidation of
MMIO sptes" below)
- cache the information to vcpu->arch.mmio_gva, vcpu->arch.mmio_access and
vcpu->arch.mmio_gfn, and call the emulator
+
- If both P bit and R/W bit of error code are set, this could possibly
be handled as a "fast page fault" (fixed without taking the MMU lock). See
- the description in Documentation/virt/kvm/locking.txt.
+ the description in Documentation/virt/kvm/locking.rst.
+
- if needed, walk the guest page tables to determine the guest translation
(gva->gpa or ngpa->gpa)
+
- if permissions are insufficient, reflect the fault back to the guest
+
- determine the host page
+
- if this is an mmio request, there is no host page; cache the info to
vcpu->arch.mmio_gva, vcpu->arch.mmio_access and vcpu->arch.mmio_gfn
+
- walk the shadow page table to find the spte for the translation,
instantiating missing intermediate page tables as necessary
+
- If this is an mmio request, cache the mmio info to the spte and set some
reserved bit on the spte (see callers of kvm_mmu_set_mmio_spte_mask)
+
- try to unsynchronize the page
+
- if successful, we can let the guest continue and modify the gpte
+
- emulate the instruction
+
- if failed, unshadow the page and let the guest continue
+
- update any translations that were modified by the instruction
invlpg handling:
@@ -324,10 +356,12 @@
Guest control register updates:
- mov to cr3
+
- look up new shadow roots
- synchronize newly reachable shadow pages
- mov to cr0/cr4/efer
+
- set up mmu context for new paging mode
- look up new shadow roots
- synchronize newly reachable shadow pages
@@ -358,6 +392,7 @@
(user write faults generate a #PF)
In the first case there are two additional complications:
+
- if CR4.SMEP is enabled: since we've turned the page into a kernel page,
the kernel may now execute it. We handle this by also setting spte.nx.
If we get a user fetch or read fault, we'll change spte.u=1 and
@@ -445,5 +480,4 @@
===============
- NPT presentation from KVM Forum 2008
- http://www.linux-kvm.org/images/c/c8/KvmForum2008%24kdf2008_21.pdf
-
+ https://www.linux-kvm.org/images/c/c8/KvmForum2008%24kdf2008_21.pdf
diff --git a/Documentation/virt/kvm/msr.rst b/Documentation/virt/kvm/msr.rst
new file mode 100644
index 0000000..e37a14c
--- /dev/null
+++ b/Documentation/virt/kvm/msr.rst
@@ -0,0 +1,378 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+=================
+KVM-specific MSRs
+=================
+
+:Author: Glauber Costa <glommer@redhat.com>, Red Hat Inc, 2010
+
+KVM makes use of some custom MSRs to service some requests.
+
+Custom MSRs have a range reserved for them, that goes from
+0x4b564d00 to 0x4b564dff. There are MSRs outside this area,
+but they are deprecated and their use is discouraged.
+
+Custom MSR list
+---------------
+
+The current supported Custom MSR list is:
+
+MSR_KVM_WALL_CLOCK_NEW:
+ 0x4b564d00
+
+data:
+ 4-byte alignment physical address of a memory area which must be
+ in guest RAM. This memory is expected to hold a copy of the following
+ structure::
+
+ struct pvclock_wall_clock {
+ u32 version;
+ u32 sec;
+ u32 nsec;
+ } __attribute__((__packed__));
+
+ whose data will be filled in by the hypervisor. The hypervisor is only
+ guaranteed to update this data at the moment of MSR write.
+ Users that want to reliably query this information more than once have
+ to write more than once to this MSR. Fields have the following meanings:
+
+ version:
+ guest has to check version before and after grabbing
+ time information and check that they are both equal and even.
+ An odd version indicates an in-progress update.
+
+ sec:
+ number of seconds for wallclock at time of boot.
+
+ nsec:
+ number of nanoseconds for wallclock at time of boot.
+
+ In order to get the current wallclock time, the system_time from
+ MSR_KVM_SYSTEM_TIME_NEW needs to be added.
+
+ Note that although MSRs are per-CPU entities, the effect of this
+ particular MSR is global.
+
+ Availability of this MSR must be checked via bit 3 in 0x4000001 cpuid
+ leaf prior to usage.
+
+MSR_KVM_SYSTEM_TIME_NEW:
+ 0x4b564d01
+
+data:
+ 4-byte aligned physical address of a memory area which must be in
+ guest RAM, plus an enable bit in bit 0. This memory is expected to hold
+ a copy of the following structure::
+
+ struct pvclock_vcpu_time_info {
+ u32 version;
+ u32 pad0;
+ u64 tsc_timestamp;
+ u64 system_time;
+ u32 tsc_to_system_mul;
+ s8 tsc_shift;
+ u8 flags;
+ u8 pad[2];
+ } __attribute__((__packed__)); /* 32 bytes */
+
+ whose data will be filled in by the hypervisor periodically. Only one
+ write, or registration, is needed for each VCPU. The interval between
+ updates of this structure is arbitrary and implementation-dependent.
+ The hypervisor may update this structure at any time it sees fit until
+ anything with bit0 == 0 is written to it.
+
+ Fields have the following meanings:
+
+ version:
+ guest has to check version before and after grabbing
+ time information and check that they are both equal and even.
+ An odd version indicates an in-progress update.
+
+ tsc_timestamp:
+ the tsc value at the current VCPU at the time
+ of the update of this structure. Guests can subtract this value
+ from current tsc to derive a notion of elapsed time since the
+ structure update.
+
+ system_time:
+ a host notion of monotonic time, including sleep
+ time at the time this structure was last updated. Unit is
+ nanoseconds.
+
+ tsc_to_system_mul:
+ multiplier to be used when converting
+ tsc-related quantity to nanoseconds
+
+ tsc_shift:
+ shift to be used when converting tsc-related
+ quantity to nanoseconds. This shift will ensure that
+ multiplication with tsc_to_system_mul does not overflow.
+ A positive value denotes a left shift, a negative value
+ a right shift.
+
+ The conversion from tsc to nanoseconds involves an additional
+ right shift by 32 bits. With this information, guests can
+ derive per-CPU time by doing::
+
+ time = (current_tsc - tsc_timestamp)
+ if (tsc_shift >= 0)
+ time <<= tsc_shift;
+ else
+ time >>= -tsc_shift;
+ time = (time * tsc_to_system_mul) >> 32
+ time = time + system_time
+
+ flags:
+ bits in this field indicate extended capabilities
+ coordinated between the guest and the hypervisor. Availability
+ of specific flags has to be checked in 0x40000001 cpuid leaf.
+ Current flags are:
+
+
+ +-----------+--------------+----------------------------------+
+ | flag bit | cpuid bit | meaning |
+ +-----------+--------------+----------------------------------+
+ | | | time measures taken across |
+ | 0 | 24 | multiple cpus are guaranteed to |
+ | | | be monotonic |
+ +-----------+--------------+----------------------------------+
+ | | | guest vcpu has been paused by |
+ | 1 | N/A | the host |
+ | | | See 4.70 in api.txt |
+ +-----------+--------------+----------------------------------+
+
+ Availability of this MSR must be checked via bit 3 in 0x4000001 cpuid
+ leaf prior to usage.
+
+
+MSR_KVM_WALL_CLOCK:
+ 0x11
+
+data and functioning:
+ same as MSR_KVM_WALL_CLOCK_NEW. Use that instead.
+
+ This MSR falls outside the reserved KVM range and may be removed in the
+ future. Its usage is deprecated.
+
+ Availability of this MSR must be checked via bit 0 in 0x4000001 cpuid
+ leaf prior to usage.
+
+MSR_KVM_SYSTEM_TIME:
+ 0x12
+
+data and functioning:
+ same as MSR_KVM_SYSTEM_TIME_NEW. Use that instead.
+
+ This MSR falls outside the reserved KVM range and may be removed in the
+ future. Its usage is deprecated.
+
+ Availability of this MSR must be checked via bit 0 in 0x4000001 cpuid
+ leaf prior to usage.
+
+ The suggested algorithm for detecting kvmclock presence is then::
+
+ if (!kvm_para_available()) /* refer to cpuid.txt */
+ return NON_PRESENT;
+
+ flags = cpuid_eax(0x40000001);
+ if (flags & 3) {
+ msr_kvm_system_time = MSR_KVM_SYSTEM_TIME_NEW;
+ msr_kvm_wall_clock = MSR_KVM_WALL_CLOCK_NEW;
+ return PRESENT;
+ } else if (flags & 0) {
+ msr_kvm_system_time = MSR_KVM_SYSTEM_TIME;
+ msr_kvm_wall_clock = MSR_KVM_WALL_CLOCK;
+ return PRESENT;
+ } else
+ return NON_PRESENT;
+
+MSR_KVM_ASYNC_PF_EN:
+ 0x4b564d02
+
+data:
+ Asynchronous page fault (APF) control MSR.
+
+ Bits 63-6 hold 64-byte aligned physical address of a 64 byte memory area
+ which must be in guest RAM and must be zeroed. This memory is expected
+ to hold a copy of the following structure::
+
+ struct kvm_vcpu_pv_apf_data {
+ /* Used for 'page not present' events delivered via #PF */
+ __u32 flags;
+
+ /* Used for 'page ready' events delivered via interrupt notification */
+ __u32 token;
+
+ __u8 pad[56];
+ __u32 enabled;
+ };
+
+ Bits 5-4 of the MSR are reserved and should be zero. Bit 0 is set to 1
+ when asynchronous page faults are enabled on the vcpu, 0 when disabled.
+ Bit 1 is 1 if asynchronous page faults can be injected when vcpu is in
+ cpl == 0. Bit 2 is 1 if asynchronous page faults are delivered to L1 as
+ #PF vmexits. Bit 2 can be set only if KVM_FEATURE_ASYNC_PF_VMEXIT is
+ present in CPUID. Bit 3 enables interrupt based delivery of 'page ready'
+ events. Bit 3 can only be set if KVM_FEATURE_ASYNC_PF_INT is present in
+ CPUID.
+
+ 'Page not present' events are currently always delivered as synthetic
+ #PF exception. During delivery of these events APF CR2 register contains
+ a token that will be used to notify the guest when missing page becomes
+ available. Also, to make it possible to distinguish between real #PF and
+ APF, first 4 bytes of 64 byte memory location ('flags') will be written
+ to by the hypervisor at the time of injection. Only first bit of 'flags'
+ is currently supported, when set, it indicates that the guest is dealing
+ with asynchronous 'page not present' event. If during a page fault APF
+ 'flags' is '0' it means that this is regular page fault. Guest is
+ supposed to clear 'flags' when it is done handling #PF exception so the
+ next event can be delivered.
+
+ Note, since APF 'page not present' events use the same exception vector
+ as regular page fault, guest must reset 'flags' to '0' before it does
+ something that can generate normal page fault.
+
+ Bytes 5-7 of 64 byte memory location ('token') will be written to by the
+ hypervisor at the time of APF 'page ready' event injection. The content
+ of these bytes is a token which was previously delivered as 'page not
+ present' event. The event indicates the page in now available. Guest is
+ supposed to write '0' to 'token' when it is done handling 'page ready'
+ event and to write 1' to MSR_KVM_ASYNC_PF_ACK after clearing the location;
+ writing to the MSR forces KVM to re-scan its queue and deliver the next
+ pending notification.
+
+ Note, MSR_KVM_ASYNC_PF_INT MSR specifying the interrupt vector for 'page
+ ready' APF delivery needs to be written to before enabling APF mechanism
+ in MSR_KVM_ASYNC_PF_EN or interrupt #0 can get injected. The MSR is
+ available if KVM_FEATURE_ASYNC_PF_INT is present in CPUID.
+
+ Note, previously, 'page ready' events were delivered via the same #PF
+ exception as 'page not present' events but this is now deprecated. If
+ bit 3 (interrupt based delivery) is not set APF events are not delivered.
+
+ If APF is disabled while there are outstanding APFs, they will
+ not be delivered.
+
+ Currently 'page ready' APF events will be always delivered on the
+ same vcpu as 'page not present' event was, but guest should not rely on
+ that.
+
+MSR_KVM_STEAL_TIME:
+ 0x4b564d03
+
+data:
+ 64-byte alignment physical address of a memory area which must be
+ in guest RAM, plus an enable bit in bit 0. This memory is expected to
+ hold a copy of the following structure::
+
+ struct kvm_steal_time {
+ __u64 steal;
+ __u32 version;
+ __u32 flags;
+ __u8 preempted;
+ __u8 u8_pad[3];
+ __u32 pad[11];
+ }
+
+ whose data will be filled in by the hypervisor periodically. Only one
+ write, or registration, is needed for each VCPU. The interval between
+ updates of this structure is arbitrary and implementation-dependent.
+ The hypervisor may update this structure at any time it sees fit until
+ anything with bit0 == 0 is written to it. Guest is required to make sure
+ this structure is initialized to zero.
+
+ Fields have the following meanings:
+
+ version:
+ a sequence counter. In other words, guest has to check
+ this field before and after grabbing time information and make
+ sure they are both equal and even. An odd version indicates an
+ in-progress update.
+
+ flags:
+ At this point, always zero. May be used to indicate
+ changes in this structure in the future.
+
+ steal:
+ the amount of time in which this vCPU did not run, in
+ nanoseconds. Time during which the vcpu is idle, will not be
+ reported as steal time.
+
+ preempted:
+ indicate the vCPU who owns this struct is running or
+ not. Non-zero values mean the vCPU has been preempted. Zero
+ means the vCPU is not preempted. NOTE, it is always zero if the
+ the hypervisor doesn't support this field.
+
+MSR_KVM_EOI_EN:
+ 0x4b564d04
+
+data:
+ Bit 0 is 1 when PV end of interrupt is enabled on the vcpu; 0
+ when disabled. Bit 1 is reserved and must be zero. When PV end of
+ interrupt is enabled (bit 0 set), bits 63-2 hold a 4-byte aligned
+ physical address of a 4 byte memory area which must be in guest RAM and
+ must be zeroed.
+
+ The first, least significant bit of 4 byte memory location will be
+ written to by the hypervisor, typically at the time of interrupt
+ injection. Value of 1 means that guest can skip writing EOI to the apic
+ (using MSR or MMIO write); instead, it is sufficient to signal
+ EOI by clearing the bit in guest memory - this location will
+ later be polled by the hypervisor.
+ Value of 0 means that the EOI write is required.
+
+ It is always safe for the guest to ignore the optimization and perform
+ the APIC EOI write anyway.
+
+ Hypervisor is guaranteed to only modify this least
+ significant bit while in the current VCPU context, this means that
+ guest does not need to use either lock prefix or memory ordering
+ primitives to synchronise with the hypervisor.
+
+ However, hypervisor can set and clear this memory bit at any time:
+ therefore to make sure hypervisor does not interrupt the
+ guest and clear the least significant bit in the memory area
+ in the window between guest testing it to detect
+ whether it can skip EOI apic write and between guest
+ clearing it to signal EOI to the hypervisor,
+ guest must both read the least significant bit in the memory area and
+ clear it using a single CPU instruction, such as test and clear, or
+ compare and exchange.
+
+MSR_KVM_POLL_CONTROL:
+ 0x4b564d05
+
+ Control host-side polling.
+
+data:
+ Bit 0 enables (1) or disables (0) host-side HLT polling logic.
+
+ KVM guests can request the host not to poll on HLT, for example if
+ they are performing polling themselves.
+
+MSR_KVM_ASYNC_PF_INT:
+ 0x4b564d06
+
+data:
+ Second asynchronous page fault (APF) control MSR.
+
+ Bits 0-7: APIC vector for delivery of 'page ready' APF events.
+ Bits 8-63: Reserved
+
+ Interrupt vector for asynchnonous 'page ready' notifications delivery.
+ The vector has to be set up before asynchronous page fault mechanism
+ is enabled in MSR_KVM_ASYNC_PF_EN. The MSR is only available if
+ KVM_FEATURE_ASYNC_PF_INT is present in CPUID.
+
+MSR_KVM_ASYNC_PF_ACK:
+ 0x4b564d07
+
+data:
+ Asynchronous page fault (APF) acknowledgment.
+
+ When the guest is done processing 'page ready' APF event and 'token'
+ field in 'struct kvm_vcpu_pv_apf_data' is cleared it is supposed to
+ write '1' to bit 0 of the MSR, this causes the host to re-scan its queue
+ and check if there are more notifications pending. The MSR is available
+ if KVM_FEATURE_ASYNC_PF_INT is present in CPUID.
diff --git a/Documentation/virt/kvm/msr.txt b/Documentation/virt/kvm/msr.txt
deleted file mode 100644
index df1f433..0000000
--- a/Documentation/virt/kvm/msr.txt
+++ /dev/null
@@ -1,284 +0,0 @@
-KVM-specific MSRs.
-Glauber Costa <glommer@redhat.com>, Red Hat Inc, 2010
-=====================================================
-
-KVM makes use of some custom MSRs to service some requests.
-
-Custom MSRs have a range reserved for them, that goes from
-0x4b564d00 to 0x4b564dff. There are MSRs outside this area,
-but they are deprecated and their use is discouraged.
-
-Custom MSR list
---------
-
-The current supported Custom MSR list is:
-
-MSR_KVM_WALL_CLOCK_NEW: 0x4b564d00
-
- data: 4-byte alignment physical address of a memory area which must be
- in guest RAM. This memory is expected to hold a copy of the following
- structure:
-
- struct pvclock_wall_clock {
- u32 version;
- u32 sec;
- u32 nsec;
- } __attribute__((__packed__));
-
- whose data will be filled in by the hypervisor. The hypervisor is only
- guaranteed to update this data at the moment of MSR write.
- Users that want to reliably query this information more than once have
- to write more than once to this MSR. Fields have the following meanings:
-
- version: guest has to check version before and after grabbing
- time information and check that they are both equal and even.
- An odd version indicates an in-progress update.
-
- sec: number of seconds for wallclock at time of boot.
-
- nsec: number of nanoseconds for wallclock at time of boot.
-
- In order to get the current wallclock time, the system_time from
- MSR_KVM_SYSTEM_TIME_NEW needs to be added.
-
- Note that although MSRs are per-CPU entities, the effect of this
- particular MSR is global.
-
- Availability of this MSR must be checked via bit 3 in 0x4000001 cpuid
- leaf prior to usage.
-
-MSR_KVM_SYSTEM_TIME_NEW: 0x4b564d01
-
- data: 4-byte aligned physical address of a memory area which must be in
- guest RAM, plus an enable bit in bit 0. This memory is expected to hold
- a copy of the following structure:
-
- struct pvclock_vcpu_time_info {
- u32 version;
- u32 pad0;
- u64 tsc_timestamp;
- u64 system_time;
- u32 tsc_to_system_mul;
- s8 tsc_shift;
- u8 flags;
- u8 pad[2];
- } __attribute__((__packed__)); /* 32 bytes */
-
- whose data will be filled in by the hypervisor periodically. Only one
- write, or registration, is needed for each VCPU. The interval between
- updates of this structure is arbitrary and implementation-dependent.
- The hypervisor may update this structure at any time it sees fit until
- anything with bit0 == 0 is written to it.
-
- Fields have the following meanings:
-
- version: guest has to check version before and after grabbing
- time information and check that they are both equal and even.
- An odd version indicates an in-progress update.
-
- tsc_timestamp: the tsc value at the current VCPU at the time
- of the update of this structure. Guests can subtract this value
- from current tsc to derive a notion of elapsed time since the
- structure update.
-
- system_time: a host notion of monotonic time, including sleep
- time at the time this structure was last updated. Unit is
- nanoseconds.
-
- tsc_to_system_mul: multiplier to be used when converting
- tsc-related quantity to nanoseconds
-
- tsc_shift: shift to be used when converting tsc-related
- quantity to nanoseconds. This shift will ensure that
- multiplication with tsc_to_system_mul does not overflow.
- A positive value denotes a left shift, a negative value
- a right shift.
-
- The conversion from tsc to nanoseconds involves an additional
- right shift by 32 bits. With this information, guests can
- derive per-CPU time by doing:
-
- time = (current_tsc - tsc_timestamp)
- if (tsc_shift >= 0)
- time <<= tsc_shift;
- else
- time >>= -tsc_shift;
- time = (time * tsc_to_system_mul) >> 32
- time = time + system_time
-
- flags: bits in this field indicate extended capabilities
- coordinated between the guest and the hypervisor. Availability
- of specific flags has to be checked in 0x40000001 cpuid leaf.
- Current flags are:
-
- flag bit | cpuid bit | meaning
- -------------------------------------------------------------
- | | time measures taken across
- 0 | 24 | multiple cpus are guaranteed to
- | | be monotonic
- -------------------------------------------------------------
- | | guest vcpu has been paused by
- 1 | N/A | the host
- | | See 4.70 in api.txt
- -------------------------------------------------------------
-
- Availability of this MSR must be checked via bit 3 in 0x4000001 cpuid
- leaf prior to usage.
-
-
-MSR_KVM_WALL_CLOCK: 0x11
-
- data and functioning: same as MSR_KVM_WALL_CLOCK_NEW. Use that instead.
-
- This MSR falls outside the reserved KVM range and may be removed in the
- future. Its usage is deprecated.
-
- Availability of this MSR must be checked via bit 0 in 0x4000001 cpuid
- leaf prior to usage.
-
-MSR_KVM_SYSTEM_TIME: 0x12
-
- data and functioning: same as MSR_KVM_SYSTEM_TIME_NEW. Use that instead.
-
- This MSR falls outside the reserved KVM range and may be removed in the
- future. Its usage is deprecated.
-
- Availability of this MSR must be checked via bit 0 in 0x4000001 cpuid
- leaf prior to usage.
-
- The suggested algorithm for detecting kvmclock presence is then:
-
- if (!kvm_para_available()) /* refer to cpuid.txt */
- return NON_PRESENT;
-
- flags = cpuid_eax(0x40000001);
- if (flags & 3) {
- msr_kvm_system_time = MSR_KVM_SYSTEM_TIME_NEW;
- msr_kvm_wall_clock = MSR_KVM_WALL_CLOCK_NEW;
- return PRESENT;
- } else if (flags & 0) {
- msr_kvm_system_time = MSR_KVM_SYSTEM_TIME;
- msr_kvm_wall_clock = MSR_KVM_WALL_CLOCK;
- return PRESENT;
- } else
- return NON_PRESENT;
-
-MSR_KVM_ASYNC_PF_EN: 0x4b564d02
- data: Bits 63-6 hold 64-byte aligned physical address of a
- 64 byte memory area which must be in guest RAM and must be
- zeroed. Bits 5-3 are reserved and should be zero. Bit 0 is 1
- when asynchronous page faults are enabled on the vcpu 0 when
- disabled. Bit 1 is 1 if asynchronous page faults can be injected
- when vcpu is in cpl == 0. Bit 2 is 1 if asynchronous page faults
- are delivered to L1 as #PF vmexits. Bit 2 can be set only if
- KVM_FEATURE_ASYNC_PF_VMEXIT is present in CPUID.
-
- First 4 byte of 64 byte memory location will be written to by
- the hypervisor at the time of asynchronous page fault (APF)
- injection to indicate type of asynchronous page fault. Value
- of 1 means that the page referred to by the page fault is not
- present. Value 2 means that the page is now available. Disabling
- interrupt inhibits APFs. Guest must not enable interrupt
- before the reason is read, or it may be overwritten by another
- APF. Since APF uses the same exception vector as regular page
- fault guest must reset the reason to 0 before it does
- something that can generate normal page fault. If during page
- fault APF reason is 0 it means that this is regular page
- fault.
-
- During delivery of type 1 APF cr2 contains a token that will
- be used to notify a guest when missing page becomes
- available. When page becomes available type 2 APF is sent with
- cr2 set to the token associated with the page. There is special
- kind of token 0xffffffff which tells vcpu that it should wake
- up all processes waiting for APFs and no individual type 2 APFs
- will be sent.
-
- If APF is disabled while there are outstanding APFs, they will
- not be delivered.
-
- Currently type 2 APF will be always delivered on the same vcpu as
- type 1 was, but guest should not rely on that.
-
-MSR_KVM_STEAL_TIME: 0x4b564d03
-
- data: 64-byte alignment physical address of a memory area which must be
- in guest RAM, plus an enable bit in bit 0. This memory is expected to
- hold a copy of the following structure:
-
- struct kvm_steal_time {
- __u64 steal;
- __u32 version;
- __u32 flags;
- __u8 preempted;
- __u8 u8_pad[3];
- __u32 pad[11];
- }
-
- whose data will be filled in by the hypervisor periodically. Only one
- write, or registration, is needed for each VCPU. The interval between
- updates of this structure is arbitrary and implementation-dependent.
- The hypervisor may update this structure at any time it sees fit until
- anything with bit0 == 0 is written to it. Guest is required to make sure
- this structure is initialized to zero.
-
- Fields have the following meanings:
-
- version: a sequence counter. In other words, guest has to check
- this field before and after grabbing time information and make
- sure they are both equal and even. An odd version indicates an
- in-progress update.
-
- flags: At this point, always zero. May be used to indicate
- changes in this structure in the future.
-
- steal: the amount of time in which this vCPU did not run, in
- nanoseconds. Time during which the vcpu is idle, will not be
- reported as steal time.
-
- preempted: indicate the vCPU who owns this struct is running or
- not. Non-zero values mean the vCPU has been preempted. Zero
- means the vCPU is not preempted. NOTE, it is always zero if the
- the hypervisor doesn't support this field.
-
-MSR_KVM_EOI_EN: 0x4b564d04
- data: Bit 0 is 1 when PV end of interrupt is enabled on the vcpu; 0
- when disabled. Bit 1 is reserved and must be zero. When PV end of
- interrupt is enabled (bit 0 set), bits 63-2 hold a 4-byte aligned
- physical address of a 4 byte memory area which must be in guest RAM and
- must be zeroed.
-
- The first, least significant bit of 4 byte memory location will be
- written to by the hypervisor, typically at the time of interrupt
- injection. Value of 1 means that guest can skip writing EOI to the apic
- (using MSR or MMIO write); instead, it is sufficient to signal
- EOI by clearing the bit in guest memory - this location will
- later be polled by the hypervisor.
- Value of 0 means that the EOI write is required.
-
- It is always safe for the guest to ignore the optimization and perform
- the APIC EOI write anyway.
-
- Hypervisor is guaranteed to only modify this least
- significant bit while in the current VCPU context, this means that
- guest does not need to use either lock prefix or memory ordering
- primitives to synchronise with the hypervisor.
-
- However, hypervisor can set and clear this memory bit at any time:
- therefore to make sure hypervisor does not interrupt the
- guest and clear the least significant bit in the memory area
- in the window between guest testing it to detect
- whether it can skip EOI apic write and between guest
- clearing it to signal EOI to the hypervisor,
- guest must both read the least significant bit in the memory area and
- clear it using a single CPU instruction, such as test and clear, or
- compare and exchange.
-
-MSR_KVM_POLL_CONTROL: 0x4b564d05
- Control host-side polling.
-
- data: Bit 0 enables (1) or disables (0) host-side HLT polling logic.
-
- KVM guests can request the host not to poll on HLT, for example if
- they are performing polling themselves.
-
diff --git a/Documentation/virt/kvm/nested-vmx.txt b/Documentation/virt/kvm/nested-vmx.rst
similarity index 87%
rename from Documentation/virt/kvm/nested-vmx.txt
rename to Documentation/virt/kvm/nested-vmx.rst
index 97eb135..6ab4e35 100644
--- a/Documentation/virt/kvm/nested-vmx.txt
+++ b/Documentation/virt/kvm/nested-vmx.rst
@@ -1,3 +1,6 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+==========
Nested VMX
==========
@@ -19,7 +22,7 @@
"The Turtles Project: Design and Implementation of Nested Virtualization",
available at:
- http://www.usenix.org/events/osdi10/tech/full_papers/Ben-Yehuda.pdf
+ https://www.usenix.org/events/osdi10/tech/full_papers/Ben-Yehuda.pdf
Terminology
@@ -41,9 +44,9 @@
emulated CPU type (qemu64) does not list the "VMX" CPU feature, so it must be
explicitly enabled, by giving qemu one of the following options:
- -cpu host (emulated CPU has all features of the real CPU)
+ - cpu host (emulated CPU has all features of the real CPU)
- -cpu qemu64,+vmx (add just the vmx feature to a named CPU type)
+ - cpu qemu64,+vmx (add just the vmx feature to a named CPU type)
ABIs
@@ -75,6 +78,8 @@
VMCS12_REVISION (from vmx.c) should be changed if struct vmcs12 or its inner
struct shadow_vmcs is ever changed.
+::
+
typedef u64 natural_width;
struct __packed vmcs12 {
/* According to the Intel spec, a VMCS region must start with
@@ -111,10 +116,7 @@
natural_width cr4_guest_host_mask;
natural_width cr0_read_shadow;
natural_width cr4_read_shadow;
- natural_width cr3_target_value0;
- natural_width cr3_target_value1;
- natural_width cr3_target_value2;
- natural_width cr3_target_value3;
+ natural_width dead_space[4]; /* Last remnants of cr3_target_value[0-3]. */
natural_width exit_qualification;
natural_width guest_linear_address;
natural_width guest_cr0;
@@ -220,21 +222,21 @@
-------
These patches were written by:
- Abel Gordon, abelg <at> il.ibm.com
- Nadav Har'El, nyh <at> il.ibm.com
- Orit Wasserman, oritw <at> il.ibm.com
- Ben-Ami Yassor, benami <at> il.ibm.com
- Muli Ben-Yehuda, muli <at> il.ibm.com
+ - Abel Gordon, abelg <at> il.ibm.com
+ - Nadav Har'El, nyh <at> il.ibm.com
+ - Orit Wasserman, oritw <at> il.ibm.com
+ - Ben-Ami Yassor, benami <at> il.ibm.com
+ - Muli Ben-Yehuda, muli <at> il.ibm.com
With contributions by:
- Anthony Liguori, aliguori <at> us.ibm.com
- Mike Day, mdday <at> us.ibm.com
- Michael Factor, factor <at> il.ibm.com
- Zvi Dubitzky, dubi <at> il.ibm.com
+ - Anthony Liguori, aliguori <at> us.ibm.com
+ - Mike Day, mdday <at> us.ibm.com
+ - Michael Factor, factor <at> il.ibm.com
+ - Zvi Dubitzky, dubi <at> il.ibm.com
And valuable reviews by:
- Avi Kivity, avi <at> redhat.com
- Gleb Natapov, gleb <at> redhat.com
- Marcelo Tosatti, mtosatti <at> redhat.com
- Kevin Tian, kevin.tian <at> intel.com
- and others.
+ - Avi Kivity, avi <at> redhat.com
+ - Gleb Natapov, gleb <at> redhat.com
+ - Marcelo Tosatti, mtosatti <at> redhat.com
+ - Kevin Tian, kevin.tian <at> intel.com
+ - and others.
diff --git a/Documentation/virt/kvm/ppc-pv.txt b/Documentation/virt/kvm/ppc-pv.rst
similarity index 90%
rename from Documentation/virt/kvm/ppc-pv.txt
rename to Documentation/virt/kvm/ppc-pv.rst
index e26115c..5fdb907 100644
--- a/Documentation/virt/kvm/ppc-pv.txt
+++ b/Documentation/virt/kvm/ppc-pv.rst
@@ -1,3 +1,6 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+=================================
The PPC KVM paravirtual interface
=================================
@@ -34,8 +37,9 @@
The parameters are as follows:
+ ======== ================ ================
Register IN OUT
-
+ ======== ================ ================
r0 - volatile
r3 1st parameter Return code
r4 2nd parameter 1st output value
@@ -47,6 +51,7 @@
r10 8th parameter 7th output value
r11 hypercall number 8th output value
r12 - volatile
+ ======== ================ ================
Hypercall definitions are shared in generic code, so the same hypercall numbers
apply for x86 and powerpc alike with the exception that each KVM hypercall
@@ -54,11 +59,13 @@
Return codes can be as follows:
+ ==== =========================
Code Meaning
-
+ ==== =========================
0 Success
12 Hypercall not implemented
<0 Error
+ ==== =========================
The magic page
==============
@@ -72,7 +79,7 @@
MMU is enabled. The second parameter indicates the address in real mode, if
applicable to the target. For now, we always map the page to -4096. This way we
can access it using absolute load and store functions. The following
-instruction reads the first field of the magic page:
+instruction reads the first field of the magic page::
ld rX, -4096(0)
@@ -93,8 +100,10 @@
The following enhancements to the magic page are currently available:
+ ============================ =======================================
KVM_MAGIC_FEAT_SR Maps SR registers r/w in the magic page
KVM_MAGIC_FEAT_MAS0_TO_SPRG7 Maps MASn, ESR, PIR and high SPRGs
+ ============================ =======================================
For enhanced features in the magic page, please check for the existence of the
feature before using them!
@@ -121,8 +130,8 @@
The following bits are safe to be set inside the guest:
- MSR_EE
- MSR_RI
+ - MSR_EE
+ - MSR_RI
If any other bit changes in the MSR, please still use mtmsr(d).
@@ -138,9 +147,9 @@
also act on the shared page. So calling privileged instructions still works as
before.
+======================= ================================
From To
-==== ==
-
+======================= ================================
mfmsr rX ld rX, magic_page->msr
mfsprg rX, 0 ld rX, magic_page->sprg0
mfsprg rX, 1 ld rX, magic_page->sprg1
@@ -173,7 +182,7 @@
[BookE only]
wrteei [0|1] b <special wrteei section>
-
+======================= ================================
Some instructions require more logic to determine what's going on than a load
or store instruction can deliver. To enable patching of those, we keep some
@@ -191,6 +200,7 @@
Hypercall ABIs in KVM on PowerPC
=================================
+
1) KVM hypercalls (ePAPR)
These are ePAPR compliant hypercall implementation (mentioned above). Even
diff --git a/Documentation/virt/kvm/review-checklist.txt b/Documentation/virt/kvm/review-checklist.rst
similarity index 91%
rename from Documentation/virt/kvm/review-checklist.txt
rename to Documentation/virt/kvm/review-checklist.rst
index 499af49..dc01aea 100644
--- a/Documentation/virt/kvm/review-checklist.txt
+++ b/Documentation/virt/kvm/review-checklist.rst
@@ -1,3 +1,6 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+================================
Review checklist for kvm patches
================================
@@ -7,7 +10,7 @@
2. Patches should be against kvm.git master branch.
3. If the patch introduces or modifies a new userspace API:
- - the API must be documented in Documentation/virt/kvm/api.txt
+ - the API must be documented in Documentation/virt/kvm/api.rst
- the API must be discoverable using KVM_CHECK_EXTENSION
4. New state must include support for save/restore.
diff --git a/Documentation/virt/kvm/running-nested-guests.rst b/Documentation/virt/kvm/running-nested-guests.rst
new file mode 100644
index 0000000..d0a1fc7
--- /dev/null
+++ b/Documentation/virt/kvm/running-nested-guests.rst
@@ -0,0 +1,276 @@
+==============================
+Running nested guests with KVM
+==============================
+
+A nested guest is the ability to run a guest inside another guest (it
+can be KVM-based or a different hypervisor). The straightforward
+example is a KVM guest that in turn runs on a KVM guest (the rest of
+this document is built on this example)::
+
+ .----------------. .----------------.
+ | | | |
+ | L2 | | L2 |
+ | (Nested Guest) | | (Nested Guest) |
+ | | | |
+ |----------------'--'----------------|
+ | |
+ | L1 (Guest Hypervisor) |
+ | KVM (/dev/kvm) |
+ | |
+ .------------------------------------------------------.
+ | L0 (Host Hypervisor) |
+ | KVM (/dev/kvm) |
+ |------------------------------------------------------|
+ | Hardware (with virtualization extensions) |
+ '------------------------------------------------------'
+
+Terminology:
+
+- L0 – level-0; the bare metal host, running KVM
+
+- L1 – level-1 guest; a VM running on L0; also called the "guest
+ hypervisor", as it itself is capable of running KVM.
+
+- L2 – level-2 guest; a VM running on L1, this is the "nested guest"
+
+.. note:: The above diagram is modelled after the x86 architecture;
+ s390x, ppc64 and other architectures are likely to have
+ a different design for nesting.
+
+ For example, s390x always has an LPAR (LogicalPARtition)
+ hypervisor running on bare metal, adding another layer and
+ resulting in at least four levels in a nested setup — L0 (bare
+ metal, running the LPAR hypervisor), L1 (host hypervisor), L2
+ (guest hypervisor), L3 (nested guest).
+
+ This document will stick with the three-level terminology (L0,
+ L1, and L2) for all architectures; and will largely focus on
+ x86.
+
+
+Use Cases
+---------
+
+There are several scenarios where nested KVM can be useful, to name a
+few:
+
+- As a developer, you want to test your software on different operating
+ systems (OSes). Instead of renting multiple VMs from a Cloud
+ Provider, using nested KVM lets you rent a large enough "guest
+ hypervisor" (level-1 guest). This in turn allows you to create
+ multiple nested guests (level-2 guests), running different OSes, on
+ which you can develop and test your software.
+
+- Live migration of "guest hypervisors" and their nested guests, for
+ load balancing, disaster recovery, etc.
+
+- VM image creation tools (e.g. ``virt-install``, etc) often run
+ their own VM, and users expect these to work inside a VM.
+
+- Some OSes use virtualization internally for security (e.g. to let
+ applications run safely in isolation).
+
+
+Enabling "nested" (x86)
+-----------------------
+
+From Linux kernel v4.19 onwards, the ``nested`` KVM parameter is enabled
+by default for Intel and AMD. (Though your Linux distribution might
+override this default.)
+
+In case you are running a Linux kernel older than v4.19, to enable
+nesting, set the ``nested`` KVM module parameter to ``Y`` or ``1``. To
+persist this setting across reboots, you can add it in a config file, as
+shown below:
+
+1. On the bare metal host (L0), list the kernel modules and ensure that
+ the KVM modules::
+
+ $ lsmod | grep -i kvm
+ kvm_intel 133627 0
+ kvm 435079 1 kvm_intel
+
+2. Show information for ``kvm_intel`` module::
+
+ $ modinfo kvm_intel | grep -i nested
+ parm: nested:bool
+
+3. For the nested KVM configuration to persist across reboots, place the
+ below in ``/etc/modprobed/kvm_intel.conf`` (create the file if it
+ doesn't exist)::
+
+ $ cat /etc/modprobe.d/kvm_intel.conf
+ options kvm-intel nested=y
+
+4. Unload and re-load the KVM Intel module::
+
+ $ sudo rmmod kvm-intel
+ $ sudo modprobe kvm-intel
+
+5. Verify if the ``nested`` parameter for KVM is enabled::
+
+ $ cat /sys/module/kvm_intel/parameters/nested
+ Y
+
+For AMD hosts, the process is the same as above, except that the module
+name is ``kvm-amd``.
+
+
+Additional nested-related kernel parameters (x86)
+-------------------------------------------------
+
+If your hardware is sufficiently advanced (Intel Haswell processor or
+higher, which has newer hardware virt extensions), the following
+additional features will also be enabled by default: "Shadow VMCS
+(Virtual Machine Control Structure)", APIC Virtualization on your bare
+metal host (L0). Parameters for Intel hosts::
+
+ $ cat /sys/module/kvm_intel/parameters/enable_shadow_vmcs
+ Y
+
+ $ cat /sys/module/kvm_intel/parameters/enable_apicv
+ Y
+
+ $ cat /sys/module/kvm_intel/parameters/ept
+ Y
+
+.. note:: If you suspect your L2 (i.e. nested guest) is running slower,
+ ensure the above are enabled (particularly
+ ``enable_shadow_vmcs`` and ``ept``).
+
+
+Starting a nested guest (x86)
+-----------------------------
+
+Once your bare metal host (L0) is configured for nesting, you should be
+able to start an L1 guest with::
+
+ $ qemu-kvm -cpu host [...]
+
+The above will pass through the host CPU's capabilities as-is to the
+gues); or for better live migration compatibility, use a named CPU
+model supported by QEMU. e.g.::
+
+ $ qemu-kvm -cpu Haswell-noTSX-IBRS,vmx=on
+
+then the guest hypervisor will subsequently be capable of running a
+nested guest with accelerated KVM.
+
+
+Enabling "nested" (s390x)
+-------------------------
+
+1. On the host hypervisor (L0), enable the ``nested`` parameter on
+ s390x::
+
+ $ rmmod kvm
+ $ modprobe kvm nested=1
+
+.. note:: On s390x, the kernel parameter ``hpage`` is mutually exclusive
+ with the ``nested`` paramter — i.e. to be able to enable
+ ``nested``, the ``hpage`` parameter *must* be disabled.
+
+2. The guest hypervisor (L1) must be provided with the ``sie`` CPU
+ feature — with QEMU, this can be done by using "host passthrough"
+ (via the command-line ``-cpu host``).
+
+3. Now the KVM module can be loaded in the L1 (guest hypervisor)::
+
+ $ modprobe kvm
+
+
+Live migration with nested KVM
+------------------------------
+
+Migrating an L1 guest, with a *live* nested guest in it, to another
+bare metal host, works as of Linux kernel 5.3 and QEMU 4.2.0 for
+Intel x86 systems, and even on older versions for s390x.
+
+On AMD systems, once an L1 guest has started an L2 guest, the L1 guest
+should no longer be migrated or saved (refer to QEMU documentation on
+"savevm"/"loadvm") until the L2 guest shuts down. Attempting to migrate
+or save-and-load an L1 guest while an L2 guest is running will result in
+undefined behavior. You might see a ``kernel BUG!`` entry in ``dmesg``, a
+kernel 'oops', or an outright kernel panic. Such a migrated or loaded L1
+guest can no longer be considered stable or secure, and must be restarted.
+Migrating an L1 guest merely configured to support nesting, while not
+actually running L2 guests, is expected to function normally even on AMD
+systems but may fail once guests are started.
+
+Migrating an L2 guest is always expected to succeed, so all the following
+scenarios should work even on AMD systems:
+
+- Migrating a nested guest (L2) to another L1 guest on the *same* bare
+ metal host.
+
+- Migrating a nested guest (L2) to another L1 guest on a *different*
+ bare metal host.
+
+- Migrating a nested guest (L2) to a bare metal host.
+
+Reporting bugs from nested setups
+-----------------------------------
+
+Debugging "nested" problems can involve sifting through log files across
+L0, L1 and L2; this can result in tedious back-n-forth between the bug
+reporter and the bug fixer.
+
+- Mention that you are in a "nested" setup. If you are running any kind
+ of "nesting" at all, say so. Unfortunately, this needs to be called
+ out because when reporting bugs, people tend to forget to even
+ *mention* that they're using nested virtualization.
+
+- Ensure you are actually running KVM on KVM. Sometimes people do not
+ have KVM enabled for their guest hypervisor (L1), which results in
+ them running with pure emulation or what QEMU calls it as "TCG", but
+ they think they're running nested KVM. Thus confusing "nested Virt"
+ (which could also mean, QEMU on KVM) with "nested KVM" (KVM on KVM).
+
+Information to collect (generic)
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+The following is not an exhaustive list, but a very good starting point:
+
+ - Kernel, libvirt, and QEMU version from L0
+
+ - Kernel, libvirt and QEMU version from L1
+
+ - QEMU command-line of L1 -- when using libvirt, you'll find it here:
+ ``/var/log/libvirt/qemu/instance.log``
+
+ - QEMU command-line of L2 -- as above, when using libvirt, get the
+ complete libvirt-generated QEMU command-line
+
+ - ``cat /sys/cpuinfo`` from L0
+
+ - ``cat /sys/cpuinfo`` from L1
+
+ - ``lscpu`` from L0
+
+ - ``lscpu`` from L1
+
+ - Full ``dmesg`` output from L0
+
+ - Full ``dmesg`` output from L1
+
+x86-specific info to collect
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Both the below commands, ``x86info`` and ``dmidecode``, should be
+available on most Linux distributions with the same name:
+
+ - Output of: ``x86info -a`` from L0
+
+ - Output of: ``x86info -a`` from L1
+
+ - Output of: ``dmidecode`` from L0
+
+ - Output of: ``dmidecode`` from L1
+
+s390x-specific info to collect
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Along with the earlier mentioned generic details, the below is
+also recommended:
+
+ - ``/proc/sysinfo`` from L1; this will also include the info from L0
diff --git a/Documentation/virt/kvm/s390-diag.txt b/Documentation/virt/kvm/s390-diag.rst
similarity index 89%
rename from Documentation/virt/kvm/s390-diag.txt
rename to Documentation/virt/kvm/s390-diag.rst
index 7c52e5f..eaac486 100644
--- a/Documentation/virt/kvm/s390-diag.txt
+++ b/Documentation/virt/kvm/s390-diag.rst
@@ -1,3 +1,6 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+=============================
The s390 DIAGNOSE call on KVM
=============================
@@ -16,12 +19,12 @@
all supported DIAGNOSE calls need to be handled by either KVM or its
userspace.
-All DIAGNOSE calls supported by KVM use the RS-a format:
+All DIAGNOSE calls supported by KVM use the RS-a format::
---------------------------------------
-| '83' | R1 | R3 | B2 | D2 |
---------------------------------------
-0 8 12 16 20 31
+ --------------------------------------
+ | '83' | R1 | R3 | B2 | D2 |
+ --------------------------------------
+ 0 8 12 16 20 31
The second-operand address (obtained by the base/displacement calculation)
is not used to address data. Instead, bits 48-63 of this address specify
diff --git a/Documentation/virt/kvm/s390-pv-boot.rst b/Documentation/virt/kvm/s390-pv-boot.rst
new file mode 100644
index 0000000..8b8fa03
--- /dev/null
+++ b/Documentation/virt/kvm/s390-pv-boot.rst
@@ -0,0 +1,84 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+======================================
+s390 (IBM Z) Boot/IPL of Protected VMs
+======================================
+
+Summary
+-------
+The memory of Protected Virtual Machines (PVMs) is not accessible to
+I/O or the hypervisor. In those cases where the hypervisor needs to
+access the memory of a PVM, that memory must be made accessible.
+Memory made accessible to the hypervisor will be encrypted. See
+:doc:`s390-pv` for details."
+
+On IPL (boot) a small plaintext bootloader is started, which provides
+information about the encrypted components and necessary metadata to
+KVM to decrypt the protected virtual machine.
+
+Based on this data, KVM will make the protected virtual machine known
+to the Ultravisor (UV) and instruct it to secure the memory of the
+PVM, decrypt the components and verify the data and address list
+hashes, to ensure integrity. Afterwards KVM can run the PVM via the
+SIE instruction which the UV will intercept and execute on KVM's
+behalf.
+
+As the guest image is just like an opaque kernel image that does the
+switch into PV mode itself, the user can load encrypted guest
+executables and data via every available method (network, dasd, scsi,
+direct kernel, ...) without the need to change the boot process.
+
+
+Diag308
+-------
+This diagnose instruction is the basic mechanism to handle IPL and
+related operations for virtual machines. The VM can set and retrieve
+IPL information blocks, that specify the IPL method/devices and
+request VM memory and subsystem resets, as well as IPLs.
+
+For PVMs this concept has been extended with new subcodes:
+
+Subcode 8: Set an IPL Information Block of type 5 (information block
+for PVMs)
+Subcode 9: Store the saved block in guest memory
+Subcode 10: Move into Protected Virtualization mode
+
+The new PV load-device-specific-parameters field specifies all data
+that is necessary to move into PV mode.
+
+* PV Header origin
+* PV Header length
+* List of Components composed of
+ * AES-XTS Tweak prefix
+ * Origin
+ * Size
+
+The PV header contains the keys and hashes, which the UV will use to
+decrypt and verify the PV, as well as control flags and a start PSW.
+
+The components are for instance an encrypted kernel, kernel parameters
+and initrd. The components are decrypted by the UV.
+
+After the initial import of the encrypted data, all defined pages will
+contain the guest content. All non-specified pages will start out as
+zero pages on first access.
+
+
+When running in protected virtualization mode, some subcodes will result in
+exceptions or return error codes.
+
+Subcodes 4 and 7, which specify operations that do not clear the guest
+memory, will result in specification exceptions. This is because the
+UV will clear all memory when a secure VM is removed, and therefore
+non-clearing IPL subcodes are not allowed.
+
+Subcodes 8, 9, 10 will result in specification exceptions.
+Re-IPL into a protected mode is only possible via a detour into non
+protected mode.
+
+Keys
+----
+Every CEC will have a unique public key to enable tooling to build
+encrypted images.
+See `s390-tools <https://github.com/ibm-s390-tools/s390-tools/>`_
+for the tooling.
diff --git a/Documentation/virt/kvm/s390-pv.rst b/Documentation/virt/kvm/s390-pv.rst
new file mode 100644
index 0000000..8e41a3b
--- /dev/null
+++ b/Documentation/virt/kvm/s390-pv.rst
@@ -0,0 +1,116 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+=========================================
+s390 (IBM Z) Ultravisor and Protected VMs
+=========================================
+
+Summary
+-------
+Protected virtual machines (PVM) are KVM VMs that do not allow KVM to
+access VM state like guest memory or guest registers. Instead, the
+PVMs are mostly managed by a new entity called Ultravisor (UV). The UV
+provides an API that can be used by PVMs and KVM to request management
+actions.
+
+Each guest starts in non-protected mode and then may make a request to
+transition into protected mode. On transition, KVM registers the guest
+and its VCPUs with the Ultravisor and prepares everything for running
+it.
+
+The Ultravisor will secure and decrypt the guest's boot memory
+(i.e. kernel/initrd). It will safeguard state changes like VCPU
+starts/stops and injected interrupts while the guest is running.
+
+As access to the guest's state, such as the SIE state description, is
+normally needed to be able to run a VM, some changes have been made in
+the behavior of the SIE instruction. A new format 4 state description
+has been introduced, where some fields have different meanings for a
+PVM. SIE exits are minimized as much as possible to improve speed and
+reduce exposed guest state.
+
+
+Interrupt injection
+-------------------
+Interrupt injection is safeguarded by the Ultravisor. As KVM doesn't
+have access to the VCPUs' lowcores, injection is handled via the
+format 4 state description.
+
+Machine check, external, IO and restart interruptions each can be
+injected on SIE entry via a bit in the interrupt injection control
+field (offset 0x54). If the guest cpu is not enabled for the interrupt
+at the time of injection, a validity interception is recognized. The
+format 4 state description contains fields in the interception data
+block where data associated with the interrupt can be transported.
+
+Program and Service Call exceptions have another layer of
+safeguarding; they can only be injected for instructions that have
+been intercepted into KVM. The exceptions need to be a valid outcome
+of an instruction emulation by KVM, e.g. we can never inject a
+addressing exception as they are reported by SIE since KVM has no
+access to the guest memory.
+
+
+Mask notification interceptions
+-------------------------------
+KVM cannot intercept lctl(g) and lpsw(e) anymore in order to be
+notified when a PVM enables a certain class of interrupt. As a
+replacement, two new interception codes have been introduced: One
+indicating that the contents of CRs 0, 6, or 14 have been changed,
+indicating different interruption subclasses; and one indicating that
+PSW bit 13 has been changed, indicating that a machine check
+intervention was requested and those are now enabled.
+
+Instruction emulation
+---------------------
+With the format 4 state description for PVMs, the SIE instruction already
+interprets more instructions than it does with format 2. It is not able
+to interpret every instruction, but needs to hand some tasks to KVM;
+therefore, the SIE and the ultravisor safeguard emulation inputs and outputs.
+
+The control structures associated with SIE provide the Secure
+Instruction Data Area (SIDA), the Interception Parameters (IP) and the
+Secure Interception General Register Save Area. Guest GRs and most of
+the instruction data, such as I/O data structures, are filtered.
+Instruction data is copied to and from the SIDA when needed. Guest
+GRs are put into / retrieved from the Secure Interception General
+Register Save Area.
+
+Only GR values needed to emulate an instruction will be copied into this
+save area and the real register numbers will be hidden.
+
+The Interception Parameters state description field still contains
+the bytes of the instruction text, but with pre-set register values
+instead of the actual ones. I.e. each instruction always uses the same
+instruction text, in order not to leak guest instruction text.
+This also implies that the register content that a guest had in r<n>
+may be in r<m> from the hypervisor's point of view.
+
+The Secure Instruction Data Area contains instruction storage
+data. Instruction data, i.e. data being referenced by an instruction
+like the SCCB for sclp, is moved via the SIDA. When an instruction is
+intercepted, the SIE will only allow data and program interrupts for
+this instruction to be moved to the guest via the two data areas
+discussed before. Other data is either ignored or results in validity
+interceptions.
+
+
+Instruction emulation interceptions
+-----------------------------------
+There are two types of SIE secure instruction intercepts: the normal
+and the notification type. Normal secure instruction intercepts will
+make the guest pending for instruction completion of the intercepted
+instruction type, i.e. on SIE entry it is attempted to complete
+emulation of the instruction with the data provided by KVM. That might
+be a program exception or instruction completion.
+
+The notification type intercepts inform KVM about guest environment
+changes due to guest instruction interpretation. Such an interception
+is recognized, for example, for the store prefix instruction to provide
+the new lowcore location. On SIE reentry, any KVM data in the data areas
+is ignored and execution continues as if the guest instruction had
+completed. For that reason KVM is not allowed to inject a program
+interrupt.
+
+Links
+-----
+`KVM Forum 2019 presentation <https://static.sched.com/hosted_files/kvmforum2019/3b/ibm_protected_vms_s390x.pdf>`_
diff --git a/Documentation/virt/kvm/timekeeping.txt b/Documentation/virt/kvm/timekeeping.rst
similarity index 85%
rename from Documentation/virt/kvm/timekeeping.txt
rename to Documentation/virt/kvm/timekeeping.rst
index 76808a1..21ae7ef 100644
--- a/Documentation/virt/kvm/timekeeping.txt
+++ b/Documentation/virt/kvm/timekeeping.rst
@@ -1,17 +1,21 @@
+.. SPDX-License-Identifier: GPL-2.0
- Timekeeping Virtualization for X86-Based Architectures
+======================================================
+Timekeeping Virtualization for X86-Based Architectures
+======================================================
- Zachary Amsden <zamsden@redhat.com>
- Copyright (c) 2010, Red Hat. All rights reserved.
+:Author: Zachary Amsden <zamsden@redhat.com>
+:Copyright: (c) 2010, Red Hat. All rights reserved.
-1) Overview
-2) Timing Devices
-3) TSC Hardware
-4) Virtualization Problems
+.. Contents
-=========================================================================
+ 1) Overview
+ 2) Timing Devices
+ 3) TSC Hardware
+ 4) Virtualization Problems
-1) Overview
+1. Overview
+===========
One of the most complicated parts of the X86 platform, and specifically,
the virtualization of this platform is the plethora of timing devices available
@@ -27,15 +31,15 @@
timekeeping which may be difficult to find elsewhere, specifically,
information relevant to KVM and hardware-based virtualization.
-=========================================================================
-
-2) Timing Devices
+2. Timing Devices
+=================
First we discuss the basic hardware devices available. TSC and the related
KVM clock are special enough to warrant a full exposition and are described in
the following section.
-2.1) i8254 - PIT
+2.1. i8254 - PIT
+----------------
One of the first timer devices available is the programmable interrupt timer,
or PIT. The PIT has a fixed frequency 1.193182 MHz base clock and three
@@ -50,13 +54,13 @@
using single or multiple byte access to the I/O ports. There are 6 modes
available, but not all modes are available to all timers, as only timer 2
has a connected gate input, required for modes 1 and 5. The gate line is
-controlled by port 61h, bit 0, as illustrated in the following diagram.
+controlled by port 61h, bit 0, as illustrated in the following diagram::
- -------------- ----------------
-| | | |
-| 1.1932 MHz |---------->| CLOCK OUT | ---------> IRQ 0
-| Clock | | | |
- -------------- | +->| GATE TIMER 0 |
+ -------------- ----------------
+ | | | |
+ | 1.1932 MHz|---------->| CLOCK OUT | ---------> IRQ 0
+ | Clock | | | |
+ -------------- | +->| GATE TIMER 0 |
| ----------------
|
| ----------------
@@ -70,29 +74,33 @@
| | |
|------>| CLOCK OUT | ---------> Port 61h, bit 5
| | |
-Port 61h, bit 0 ---------->| GATE TIMER 2 | \_.---- ____
+ Port 61h, bit 0 -------->| GATE TIMER 2 | \_.---- ____
---------------- _| )--|LPF|---Speaker
/ *---- \___/
-Port 61h, bit 1 -----------------------------------/
+ Port 61h, bit 1 ---------------------------------/
The timer modes are now described.
-Mode 0: Single Timeout. This is a one-shot software timeout that counts down
+Mode 0: Single Timeout.
+ This is a one-shot software timeout that counts down
when the gate is high (always true for timers 0 and 1). When the count
reaches zero, the output goes high.
-Mode 1: Triggered One-shot. The output is initially set high. When the gate
+Mode 1: Triggered One-shot.
+ The output is initially set high. When the gate
line is set high, a countdown is initiated (which does not stop if the gate is
lowered), during which the output is set low. When the count reaches zero,
the output goes high.
-Mode 2: Rate Generator. The output is initially set high. When the countdown
+Mode 2: Rate Generator.
+ The output is initially set high. When the countdown
reaches 1, the output goes low for one count and then returns high. The value
is reloaded and the countdown automatically resumes. If the gate line goes
low, the count is halted. If the output is low when the gate is lowered, the
output automatically goes high (this only affects timer 2).
-Mode 3: Square Wave. This generates a high / low square wave. The count
+Mode 3: Square Wave.
+ This generates a high / low square wave. The count
determines the length of the pulse, which alternates between high and low
when zero is reached. The count only proceeds when gate is high and is
automatically reloaded on reaching zero. The count is decremented twice at
@@ -103,12 +111,14 @@
values are not observed when reading. This is the intended mode for timer 2,
which generates sine-like tones by low-pass filtering the square wave output.
-Mode 4: Software Strobe. After programming this mode and loading the counter,
+Mode 4: Software Strobe.
+ After programming this mode and loading the counter,
the output remains high until the counter reaches zero. Then the output
goes low for 1 clock cycle and returns high. The counter is not reloaded.
Counting only occurs when gate is high.
-Mode 5: Hardware Strobe. After programming and loading the counter, the
+Mode 5: Hardware Strobe.
+ After programming and loading the counter, the
output remains high. When the gate is raised, a countdown is initiated
(which does not stop if the gate is lowered). When the counter reaches zero,
the output goes low for 1 clock cycle and then returns high. The counter is
@@ -118,49 +128,49 @@
command port, 0x43 is used to set the counter and mode for each of the three
timers.
-PIT commands, issued to port 0x43, using the following bit encoding:
+PIT commands, issued to port 0x43, using the following bit encoding::
-Bit 7-4: Command (See table below)
-Bit 3-1: Mode (000 = Mode 0, 101 = Mode 5, 11X = undefined)
-Bit 0 : Binary (0) / BCD (1)
+ Bit 7-4: Command (See table below)
+ Bit 3-1: Mode (000 = Mode 0, 101 = Mode 5, 11X = undefined)
+ Bit 0 : Binary (0) / BCD (1)
-Command table:
+Command table::
-0000 - Latch Timer 0 count for port 0x40
+ 0000 - Latch Timer 0 count for port 0x40
sample and hold the count to be read in port 0x40;
additional commands ignored until counter is read;
mode bits ignored.
-0001 - Set Timer 0 LSB mode for port 0x40
+ 0001 - Set Timer 0 LSB mode for port 0x40
set timer to read LSB only and force MSB to zero;
mode bits set timer mode
-0010 - Set Timer 0 MSB mode for port 0x40
+ 0010 - Set Timer 0 MSB mode for port 0x40
set timer to read MSB only and force LSB to zero;
mode bits set timer mode
-0011 - Set Timer 0 16-bit mode for port 0x40
+ 0011 - Set Timer 0 16-bit mode for port 0x40
set timer to read / write LSB first, then MSB;
mode bits set timer mode
-0100 - Latch Timer 1 count for port 0x41 - as described above
-0101 - Set Timer 1 LSB mode for port 0x41 - as described above
-0110 - Set Timer 1 MSB mode for port 0x41 - as described above
-0111 - Set Timer 1 16-bit mode for port 0x41 - as described above
+ 0100 - Latch Timer 1 count for port 0x41 - as described above
+ 0101 - Set Timer 1 LSB mode for port 0x41 - as described above
+ 0110 - Set Timer 1 MSB mode for port 0x41 - as described above
+ 0111 - Set Timer 1 16-bit mode for port 0x41 - as described above
-1000 - Latch Timer 2 count for port 0x42 - as described above
-1001 - Set Timer 2 LSB mode for port 0x42 - as described above
-1010 - Set Timer 2 MSB mode for port 0x42 - as described above
-1011 - Set Timer 2 16-bit mode for port 0x42 as described above
+ 1000 - Latch Timer 2 count for port 0x42 - as described above
+ 1001 - Set Timer 2 LSB mode for port 0x42 - as described above
+ 1010 - Set Timer 2 MSB mode for port 0x42 - as described above
+ 1011 - Set Timer 2 16-bit mode for port 0x42 as described above
-1101 - General counter latch
+ 1101 - General counter latch
Latch combination of counters into corresponding ports
Bit 3 = Counter 2
Bit 2 = Counter 1
Bit 1 = Counter 0
Bit 0 = Unused
-1110 - Latch timer status
+ 1110 - Latch timer status
Latch combination of counter mode into corresponding ports
Bit 3 = Counter 2
Bit 2 = Counter 1
@@ -177,7 +187,8 @@
Bit 3-1 = Mode
Bit 0 = Binary (0) / BCD mode (1)
-2.2) RTC
+2.2. RTC
+--------
The second device which was available in the original PC was the MC146818 real
time clock. The original device is now obsolete, and usually emulated by the
@@ -201,21 +212,21 @@
The clock uses a 32.768kHz crystal, so bits 6-4 of register A should be
programmed to a 32kHz divider if the RTC is to count seconds.
-This is the RAM map originally used for the RTC/CMOS:
+This is the RAM map originally used for the RTC/CMOS::
-Location Size Description
-------------------------------------------
-00h byte Current second (BCD)
-01h byte Seconds alarm (BCD)
-02h byte Current minute (BCD)
-03h byte Minutes alarm (BCD)
-04h byte Current hour (BCD)
-05h byte Hours alarm (BCD)
-06h byte Current day of week (BCD)
-07h byte Current day of month (BCD)
-08h byte Current month (BCD)
-09h byte Current year (BCD)
-0Ah byte Register A
+ Location Size Description
+ ------------------------------------------
+ 00h byte Current second (BCD)
+ 01h byte Seconds alarm (BCD)
+ 02h byte Current minute (BCD)
+ 03h byte Minutes alarm (BCD)
+ 04h byte Current hour (BCD)
+ 05h byte Hours alarm (BCD)
+ 06h byte Current day of week (BCD)
+ 07h byte Current day of month (BCD)
+ 08h byte Current month (BCD)
+ 09h byte Current year (BCD)
+ 0Ah byte Register A
bit 7 = Update in progress
bit 6-4 = Divider for clock
000 = 4.194 MHz
@@ -234,7 +245,7 @@
1101 = 125 mS
1110 = 250 mS
1111 = 500 mS
-0Bh byte Register B
+ 0Bh byte Register B
bit 7 = Run (0) / Halt (1)
bit 6 = Periodic interrupt enable
bit 5 = Alarm interrupt enable
@@ -243,19 +254,20 @@
bit 2 = BCD calendar (0) / Binary (1)
bit 1 = 12-hour mode (0) / 24-hour mode (1)
bit 0 = 0 (DST off) / 1 (DST enabled)
-OCh byte Register C (read only)
+ OCh byte Register C (read only)
bit 7 = interrupt request flag (IRQF)
bit 6 = periodic interrupt flag (PF)
bit 5 = alarm interrupt flag (AF)
bit 4 = update interrupt flag (UF)
bit 3-0 = reserved
-ODh byte Register D (read only)
+ ODh byte Register D (read only)
bit 7 = RTC has power
bit 6-0 = reserved
-32h byte Current century BCD (*)
+ 32h byte Current century BCD (*)
(*) location vendor specific and now determined from ACPI global tables
-2.3) APIC
+2.3. APIC
+---------
On Pentium and later processors, an on-board timer is available to each CPU
as part of the Advanced Programmable Interrupt Controller. The APIC is
@@ -276,7 +288,8 @@
of one-shot or periodic operation, and is based on the bus clock divided down
by the programmable divider register.
-2.4) HPET
+2.4. HPET
+---------
HPET is quite complex, and was originally intended to replace the PIT / RTC
support of the X86 PC. It remains to be seen whether that will be the case, as
@@ -297,7 +310,8 @@
Detailed specification of the HPET is beyond the current scope of this
document, as it is also very well documented elsewhere.
-2.5) Offboard Timers
+2.5. Offboard Timers
+--------------------
Several cards, both proprietary (watchdog boards) and commonplace (e1000) have
timing chips built into the cards which may have registers which are accessible
@@ -307,9 +321,8 @@
timer device would require additional support to be virtualized properly and is
not considered important at this time as no known operating system does this.
-=========================================================================
-
-3) TSC Hardware
+3. TSC Hardware
+===============
The TSC or time stamp counter is relatively simple in theory; it counts
instruction cycles issued by the processor, which can be used as a measure of
@@ -340,7 +353,8 @@
promise to allow the TSC to additionally be scaled, but this hardware is not
yet widely available.
-3.1) TSC synchronization
+3.1. TSC synchronization
+------------------------
The TSC is a CPU-local clock in most implementations. This means, on SMP
platforms, the TSCs of different CPUs may start at different times depending
@@ -357,7 +371,8 @@
values are read from the same clock, which generally only is possible on single
socket systems or those with special hardware support.
-3.2) TSC and CPU hotplug
+3.2. TSC and CPU hotplug
+------------------------
As touched on already, CPUs which arrive later than the boot time of the system
may not have a TSC value that is synchronized with the rest of the system.
@@ -367,7 +382,8 @@
TSC is synchronized back to a state where TSC synchronization flaws, however
small, may be exposed to the OS and any virtualization environment.
-3.3) TSC and multi-socket / NUMA
+3.3. TSC and multi-socket / NUMA
+--------------------------------
Multi-socket systems, especially large multi-socket systems are likely to have
individual clocksources rather than a single, universally distributed clock.
@@ -385,7 +401,8 @@
It is recommended not to trust the TSCs to remain synchronized on NUMA or
multiple socket systems for these reasons.
-3.4) TSC and C-states
+3.4. TSC and C-states
+---------------------
C-states, or idling states of the processor, especially C1E and deeper sleep
states may be problematic for TSC as well. The TSC may stop advancing in such
@@ -396,7 +413,8 @@
The TSC in such a case may be corrected by catching it up to a known external
clocksource.
-3.5) TSC frequency change / P-states
+3.5. TSC frequency change / P-states
+------------------------------------
To make things slightly more interesting, some CPUs may change frequency. They
may or may not run the TSC at the same rate, and because the frequency change
@@ -416,14 +434,16 @@
than that of non-halted processors. AMD Turion processors are known to have
this problem.
-3.6) TSC and STPCLK / T-states
+3.6. TSC and STPCLK / T-states
+------------------------------
External signals given to the processor may also have the effect of stopping
the TSC. This is typically done for thermal emergency power control to prevent
an overheating condition, and typically, there is no way to detect that this
condition has happened.
-3.7) TSC virtualization - VMX
+3.7. TSC virtualization - VMX
+-----------------------------
VMX provides conditional trapping of RDTSC, RDMSR, WRMSR and RDTSCP
instructions, which is enough for full virtualization of TSC in any manner. In
@@ -431,14 +451,16 @@
field specified in the VMCS. Special instructions must be used to read and
write the VMCS field.
-3.8) TSC virtualization - SVM
+3.8. TSC virtualization - SVM
+-----------------------------
SVM provides conditional trapping of RDTSC, RDMSR, WRMSR and RDTSCP
instructions, which is enough for full virtualization of TSC in any manner. In
addition, SVM allows passing through the host TSC plus an additional offset
field specified in the SVM control block.
-3.9) TSC feature bits in Linux
+3.9. TSC feature bits in Linux
+------------------------------
In summary, there is no way to guarantee the TSC remains in perfect
synchronization unless it is explicitly guaranteed by the architecture. Even
@@ -448,13 +470,16 @@
The following feature bits are used by Linux to signal various TSC attributes,
but they can only be taken to be meaningful for UP or single node systems.
-X86_FEATURE_TSC : The TSC is available in hardware
-X86_FEATURE_RDTSCP : The RDTSCP instruction is available
-X86_FEATURE_CONSTANT_TSC : The TSC rate is unchanged with P-states
-X86_FEATURE_NONSTOP_TSC : The TSC does not stop in C-states
-X86_FEATURE_TSC_RELIABLE : TSC sync checks are skipped (VMware)
+========================= =======================================
+X86_FEATURE_TSC The TSC is available in hardware
+X86_FEATURE_RDTSCP The RDTSCP instruction is available
+X86_FEATURE_CONSTANT_TSC The TSC rate is unchanged with P-states
+X86_FEATURE_NONSTOP_TSC The TSC does not stop in C-states
+X86_FEATURE_TSC_RELIABLE TSC sync checks are skipped (VMware)
+========================= =======================================
-4) Virtualization Problems
+4. Virtualization Problems
+==========================
Timekeeping is especially problematic for virtualization because a number of
challenges arise. The most obvious problem is that time is now shared between
@@ -473,7 +498,8 @@
cause similar problems to virtualization makes it a good justification for
solving many of these problems on bare metal.
-4.1) Interrupt clocking
+4.1. Interrupt clocking
+-----------------------
One of the most immediate problems that occurs with legacy operating systems
is that the system timekeeping routines are often designed to keep track of
@@ -502,7 +528,8 @@
rate (ed: is it 18.2 Hz?) however that it has not yet been a problem in
practice.
-4.2) TSC sampling and serialization
+4.2. TSC sampling and serialization
+-----------------------------------
As the highest precision time source available, the cycle counter of the CPU
has aroused much interest from developers. As explained above, this timer has
@@ -524,7 +551,8 @@
the TSC as seen from other CPUs, even in an otherwise perfectly synchronized
system.
-4.3) Timespec aliasing
+4.3. Timespec aliasing
+----------------------
Additionally, this lack of serialization from the TSC poses another challenge
when using results of the TSC when measured against another time source. As
@@ -548,7 +576,8 @@
and any other values derived from TSC computation (such as TSC virtualization
itself).
-4.4) Migration
+4.4. Migration
+--------------
Migration of a virtual machine raises problems for timekeeping in two ways.
First, the migration itself may take time, during which interrupts cannot be
@@ -566,7 +595,8 @@
simply storing multipliers and offsets against the TSC for the guest to convert
back into nanosecond resolution values.
-4.5) Scheduling
+4.5. Scheduling
+---------------
Since scheduling may be based on precise timing and firing of interrupts, the
scheduling algorithms of an operating system may be adversely affected by
@@ -579,7 +609,8 @@
paravirtualized scheduler clock, which reveals the true amount of CPU time for
which a virtual machine has been running.
-4.6) Watchdogs
+4.6. Watchdogs
+--------------
Watchdog timers, such as the lock detector in Linux may fire accidentally when
running under hardware virtualization due to timer interrupts being delayed or
@@ -587,7 +618,8 @@
spurious and can be ignored, but in some circumstances it may be necessary to
disable such detection.
-4.7) Delays and precision timing
+4.7. Delays and precision timing
+--------------------------------
Precise timing and delays may not be possible in a virtualized system. This
can happen if the system is controlling physical hardware, or issues delays to
@@ -600,7 +632,8 @@
significant issue. In many cases these delays may be eliminated through
configuration or paravirtualization.
-4.8) Covert channels and leaks
+4.8. Covert channels and leaks
+------------------------------
In addition to the above problems, time information will inevitably leak to the
guest about the host in anything but a perfect implementation of virtualized
diff --git a/Documentation/virt/ne_overview.rst b/Documentation/virt/ne_overview.rst
new file mode 100644
index 0000000..39b0c8f
--- /dev/null
+++ b/Documentation/virt/ne_overview.rst
@@ -0,0 +1,95 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+==============
+Nitro Enclaves
+==============
+
+Overview
+========
+
+Nitro Enclaves (NE) is a new Amazon Elastic Compute Cloud (EC2) capability
+that allows customers to carve out isolated compute environments within EC2
+instances [1].
+
+For example, an application that processes sensitive data and runs in a VM,
+can be separated from other applications running in the same VM. This
+application then runs in a separate VM than the primary VM, namely an enclave.
+
+An enclave runs alongside the VM that spawned it. This setup matches low latency
+applications needs. The resources that are allocated for the enclave, such as
+memory and CPUs, are carved out of the primary VM. Each enclave is mapped to a
+process running in the primary VM, that communicates with the NE driver via an
+ioctl interface.
+
+In this sense, there are two components:
+
+1. An enclave abstraction process - a user space process running in the primary
+VM guest that uses the provided ioctl interface of the NE driver to spawn an
+enclave VM (that's 2 below).
+
+There is a NE emulated PCI device exposed to the primary VM. The driver for this
+new PCI device is included in the NE driver.
+
+The ioctl logic is mapped to PCI device commands e.g. the NE_START_ENCLAVE ioctl
+maps to an enclave start PCI command. The PCI device commands are then
+translated into actions taken on the hypervisor side; that's the Nitro
+hypervisor running on the host where the primary VM is running. The Nitro
+hypervisor is based on core KVM technology.
+
+2. The enclave itself - a VM running on the same host as the primary VM that
+spawned it. Memory and CPUs are carved out of the primary VM and are dedicated
+for the enclave VM. An enclave does not have persistent storage attached.
+
+The memory regions carved out of the primary VM and given to an enclave need to
+be aligned 2 MiB / 1 GiB physically contiguous memory regions (or multiple of
+this size e.g. 8 MiB). The memory can be allocated e.g. by using hugetlbfs from
+user space [2][3]. The memory size for an enclave needs to be at least 64 MiB.
+The enclave memory and CPUs need to be from the same NUMA node.
+
+An enclave runs on dedicated cores. CPU 0 and its CPU siblings need to remain
+available for the primary VM. A CPU pool has to be set for NE purposes by an
+user with admin capability. See the cpu list section from the kernel
+documentation [4] for how a CPU pool format looks.
+
+An enclave communicates with the primary VM via a local communication channel,
+using virtio-vsock [5]. The primary VM has virtio-pci vsock emulated device,
+while the enclave VM has a virtio-mmio vsock emulated device. The vsock device
+uses eventfd for signaling. The enclave VM sees the usual interfaces - local
+APIC and IOAPIC - to get interrupts from virtio-vsock device. The virtio-mmio
+device is placed in memory below the typical 4 GiB.
+
+The application that runs in the enclave needs to be packaged in an enclave
+image together with the OS ( e.g. kernel, ramdisk, init ) that will run in the
+enclave VM. The enclave VM has its own kernel and follows the standard Linux
+boot protocol [6].
+
+The kernel bzImage, the kernel command line, the ramdisk(s) are part of the
+Enclave Image Format (EIF); plus an EIF header including metadata such as magic
+number, eif version, image size and CRC.
+
+Hash values are computed for the entire enclave image (EIF), the kernel and
+ramdisk(s). That's used, for example, to check that the enclave image that is
+loaded in the enclave VM is the one that was intended to be run.
+
+These crypto measurements are included in a signed attestation document
+generated by the Nitro Hypervisor and further used to prove the identity of the
+enclave; KMS is an example of service that NE is integrated with and that checks
+the attestation doc.
+
+The enclave image (EIF) is loaded in the enclave memory at offset 8 MiB. The
+init process in the enclave connects to the vsock CID of the primary VM and a
+predefined port - 9000 - to send a heartbeat value - 0xb7. This mechanism is
+used to check in the primary VM that the enclave has booted. The CID of the
+primary VM is 3.
+
+If the enclave VM crashes or gracefully exits, an interrupt event is received by
+the NE driver. This event is sent further to the user space enclave process
+running in the primary VM via a poll notification mechanism. Then the user space
+enclave process can exit.
+
+[1] https://aws.amazon.com/ec2/nitro/nitro-enclaves/
+[2] https://www.kernel.org/doc/html/latest/admin-guide/mm/hugetlbpage.html
+[3] https://lwn.net/Articles/807108/
+[4] https://www.kernel.org/doc/html/latest/admin-guide/kernel-parameters.html
+[5] https://man7.org/linux/man-pages/man7/vsock.7.html
+[6] https://www.kernel.org/doc/html/latest/x86/boot.html
diff --git a/Documentation/virt/uml/UserModeLinux-HOWTO.txt b/Documentation/virt/uml/UserModeLinux-HOWTO.txt
deleted file mode 100644
index 87b80f5..0000000
--- a/Documentation/virt/uml/UserModeLinux-HOWTO.txt
+++ /dev/null
@@ -1,4589 +0,0 @@
- User Mode Linux HOWTO
- User Mode Linux Core Team
- Mon Nov 18 14:16:16 EST 2002
-
- This document describes the use and abuse of Jeff Dike's User Mode
- Linux: a port of the Linux kernel as a normal Intel Linux process.
- ______________________________________________________________________
-
- Table of Contents
-
- 1. Introduction
-
- 1.1 How is User Mode Linux Different?
- 1.2 Why Would I Want User Mode Linux?
-
- 2. Compiling the kernel and modules
-
- 2.1 Compiling the kernel
- 2.2 Compiling and installing kernel modules
- 2.3 Compiling and installing uml_utilities
-
- 3. Running UML and logging in
-
- 3.1 Running UML
- 3.2 Logging in
- 3.3 Examples
-
- 4. UML on 2G/2G hosts
-
- 4.1 Introduction
- 4.2 The problem
- 4.3 The solution
-
- 5. Setting up serial lines and consoles
-
- 5.1 Specifying the device
- 5.2 Specifying the channel
- 5.3 Examples
-
- 6. Setting up the network
-
- 6.1 General setup
- 6.2 Userspace daemons
- 6.3 Specifying ethernet addresses
- 6.4 UML interface setup
- 6.5 Multicast
- 6.6 TUN/TAP with the uml_net helper
- 6.7 TUN/TAP with a preconfigured tap device
- 6.8 Ethertap
- 6.9 The switch daemon
- 6.10 Slip
- 6.11 Slirp
- 6.12 pcap
- 6.13 Setting up the host yourself
-
- 7. Sharing Filesystems between Virtual Machines
-
- 7.1 A warning
- 7.2 Using layered block devices
- 7.3 Note!
- 7.4 Another warning
- 7.5 uml_moo : Merging a COW file with its backing file
-
- 8. Creating filesystems
-
- 8.1 Create the filesystem file
- 8.2 Assign the file to a UML device
- 8.3 Creating and mounting the filesystem
-
- 9. Host file access
-
- 9.1 Using hostfs
- 9.2 hostfs as the root filesystem
- 9.3 Building hostfs
-
- 10. The Management Console
- 10.1 version
- 10.2 halt and reboot
- 10.3 config
- 10.4 remove
- 10.5 sysrq
- 10.6 help
- 10.7 cad
- 10.8 stop
- 10.9 go
-
- 11. Kernel debugging
-
- 11.1 Starting the kernel under gdb
- 11.2 Examining sleeping processes
- 11.3 Running ddd on UML
- 11.4 Debugging modules
- 11.5 Attaching gdb to the kernel
- 11.6 Using alternate debuggers
-
- 12. Kernel debugging examples
-
- 12.1 The case of the hung fsck
- 12.2 Episode 2: The case of the hung fsck
-
- 13. What to do when UML doesn't work
-
- 13.1 Strange compilation errors when you build from source
- 13.2 (obsolete)
- 13.3 A variety of panics and hangs with /tmp on a reiserfs filesystem
- 13.4 The compile fails with errors about conflicting types for 'open', 'dup', and 'waitpid'
- 13.5 UML doesn't work when /tmp is an NFS filesystem
- 13.6 UML hangs on boot when compiled with gprof support
- 13.7 syslogd dies with a SIGTERM on startup
- 13.8 TUN/TAP networking doesn't work on a 2.4 host
- 13.9 You can network to the host but not to other machines on the net
- 13.10 I have no root and I want to scream
- 13.11 UML build conflict between ptrace.h and ucontext.h
- 13.12 The UML BogoMips is exactly half the host's BogoMips
- 13.13 When you run UML, it immediately segfaults
- 13.14 xterms appear, then immediately disappear
- 13.15 Any other panic, hang, or strange behavior
-
- 14. Diagnosing Problems
-
- 14.1 Case 1 : Normal kernel panics
- 14.2 Case 2 : Tracing thread panics
- 14.3 Case 3 : Tracing thread panics caused by other threads
- 14.4 Case 4 : Hangs
-
- 15. Thanks
-
- 15.1 Code and Documentation
- 15.2 Flushing out bugs
- 15.3 Buglets and clean-ups
- 15.4 Case Studies
- 15.5 Other contributions
-
-
- ______________________________________________________________________
-
- 1. Introduction
-
- Welcome to User Mode Linux. It's going to be fun.
-
-
-
- 1.1. How is User Mode Linux Different?
-
- Normally, the Linux Kernel talks straight to your hardware (video
- card, keyboard, hard drives, etc), and any programs which run ask the
- kernel to operate the hardware, like so:
-
-
-
- +-----------+-----------+----+
- | Process 1 | Process 2 | ...|
- +-----------+-----------+----+
- | Linux Kernel |
- +----------------------------+
- | Hardware |
- +----------------------------+
-
-
-
-
- The User Mode Linux Kernel is different; instead of talking to the
- hardware, it talks to a `real' Linux kernel (called the `host kernel'
- from now on), like any other program. Programs can then run inside
- User-Mode Linux as if they were running under a normal kernel, like
- so:
-
-
-
- +----------------+
- | Process 2 | ...|
- +-----------+----------------+
- | Process 1 | User-Mode Linux|
- +----------------------------+
- | Linux Kernel |
- +----------------------------+
- | Hardware |
- +----------------------------+
-
-
-
-
-
- 1.2. Why Would I Want User Mode Linux?
-
-
- 1. If User Mode Linux crashes, your host kernel is still fine.
-
- 2. You can run a usermode kernel as a non-root user.
-
- 3. You can debug the User Mode Linux like any normal process.
-
- 4. You can run gprof (profiling) and gcov (coverage testing).
-
- 5. You can play with your kernel without breaking things.
-
- 6. You can use it as a sandbox for testing new apps.
-
- 7. You can try new development kernels safely.
-
- 8. You can run different distributions simultaneously.
-
- 9. It's extremely fun.
-
-
-
-
-
- 2. Compiling the kernel and modules
-
-
-
-
- 2.1. Compiling the kernel
-
-
- Compiling the user mode kernel is just like compiling any other
- kernel. Let's go through the steps, using 2.4.0-prerelease (current
- as of this writing) as an example:
-
-
- 1. Download the latest UML patch from
-
- the download page <http://user-mode-linux.sourceforge.net/
-
- In this example, the file is uml-patch-2.4.0-prerelease.bz2.
-
-
- 2. Download the matching kernel from your favourite kernel mirror,
- such as:
-
- ftp://ftp.ca.kernel.org/pub/kernel/v2.4/linux-2.4.0-prerelease.tar.bz2
- <ftp://ftp.ca.kernel.org/pub/kernel/v2.4/linux-2.4.0-prerelease.tar.bz2>
- .
-
-
- 3. Make a directory and unpack the kernel into it.
-
-
-
- host%
- mkdir ~/uml
-
-
-
-
-
-
- host%
- cd ~/uml
-
-
-
-
-
-
- host%
- tar -xzvf linux-2.4.0-prerelease.tar.bz2
-
-
-
-
-
-
- 4. Apply the patch using
-
-
-
- host%
- cd ~/uml/linux
-
-
-
- host%
- bzcat uml-patch-2.4.0-prerelease.bz2 | patch -p1
-
-
-
-
-
-
- 5. Run your favorite config; `make xconfig ARCH=um' is the most
- convenient. `make config ARCH=um' and 'make menuconfig ARCH=um'
- will work as well. The defaults will give you a useful kernel. If
- you want to change something, go ahead, it probably won't hurt
- anything.
-
-
- Note: If the host is configured with a 2G/2G address space split
- rather than the usual 3G/1G split, then the packaged UML binaries
- will not run. They will immediately segfault. See ``UML on 2G/2G
- hosts'' for the scoop on running UML on your system.
-
-
-
- 6. Finish with `make linux ARCH=um': the result is a file called
- `linux' in the top directory of your source tree.
-
- Make sure that you don't build this kernel in /usr/src/linux. On some
- distributions, /usr/include/asm is a link into this pool. The user-
- mode build changes the other end of that link, and things that include
- <asm/anything.h> stop compiling.
-
- The sources are also available from cvs at the project's cvs page,
- which has directions on getting the sources. You can also browse the
- CVS pool from there.
-
- If you get the CVS sources, you will have to check them out into an
- empty directory. You will then have to copy each file into the
- corresponding directory in the appropriate kernel pool.
-
- If you don't have the latest kernel pool, you can get the
- corresponding user-mode sources with
-
-
- host% cvs co -r v_2_3_x linux
-
-
-
-
- where 'x' is the version in your pool. Note that you will not get the
- bug fixes and enhancements that have gone into subsequent releases.
-
-
- 2.2. Compiling and installing kernel modules
-
- UML modules are built in the same way as the native kernel (with the
- exception of the 'ARCH=um' that you always need for UML):
-
-
- host% make modules ARCH=um
-
-
-
-
- Any modules that you want to load into this kernel need to be built in
- the user-mode pool. Modules from the native kernel won't work.
-
- You can install them by using ftp or something to copy them into the
- virtual machine and dropping them into /lib/modules/`uname -r`.
-
- You can also get the kernel build process to install them as follows:
-
- 1. with the kernel not booted, mount the root filesystem in the top
- level of the kernel pool:
-
-
- host% mount root_fs mnt -o loop
-
-
-
-
-
-
- 2. run
-
-
- host%
- make modules_install INSTALL_MOD_PATH=`pwd`/mnt ARCH=um
-
-
-
-
-
-
- 3. unmount the filesystem
-
-
- host% umount mnt
-
-
-
-
-
-
- 4. boot the kernel on it
-
-
- When the system is booted, you can use insmod as usual to get the
- modules into the kernel. A number of things have been loaded into UML
- as modules, especially filesystems and network protocols and filters,
- so most symbols which need to be exported probably already are.
- However, if you do find symbols that need exporting, let us
- <http://user-mode-linux.sourceforge.net/> know, and
- they'll be "taken care of".
-
-
-
- 2.3. Compiling and installing uml_utilities
-
- Many features of the UML kernel require a user-space helper program,
- so a uml_utilities package is distributed separately from the kernel
- patch which provides these helpers. Included within this is:
-
- o port-helper - Used by consoles which connect to xterms or ports
-
- o tunctl - Configuration tool to create and delete tap devices
-
- o uml_net - Setuid binary for automatic tap device configuration
-
- o uml_switch - User-space virtual switch required for daemon
- transport
-
- The uml_utilities tree is compiled with:
-
-
- host#
- make && make install
-
-
-
-
- Note that UML kernel patches may require a specific version of the
- uml_utilities distribution. If you don't keep up with the mailing
- lists, ensure that you have the latest release of uml_utilities if you
- are experiencing problems with your UML kernel, particularly when
- dealing with consoles or command-line switches to the helper programs
-
-
-
-
-
-
-
-
- 3. Running UML and logging in
-
-
-
- 3.1. Running UML
-
- It runs on 2.2.15 or later, and all 2.4 kernels.
-
-
- Booting UML is straightforward. Simply run 'linux': it will try to
- mount the file `root_fs' in the current directory. You do not need to
- run it as root. If your root filesystem is not named `root_fs', then
- you need to put a `ubd0=root_fs_whatever' switch on the linux command
- line.
-
-
- You will need a filesystem to boot UML from. There are a number
- available for download from here <http://user-mode-
- linux.sourceforge.net/> . There are also several tools
- <http://user-mode-linux.sourceforge.net/> which can be
- used to generate UML-compatible filesystem images from media.
- The kernel will boot up and present you with a login prompt.
-
-
- Note: If the host is configured with a 2G/2G address space split
- rather than the usual 3G/1G split, then the packaged UML binaries will
- not run. They will immediately segfault. See ``UML on 2G/2G hosts''
- for the scoop on running UML on your system.
-
-
-
- 3.2. Logging in
-
-
-
- The prepackaged filesystems have a root account with password 'root'
- and a user account with password 'user'. The login banner will
- generally tell you how to log in. So, you log in and you will find
- yourself inside a little virtual machine. Our filesystems have a
- variety of commands and utilities installed (and it is fairly easy to
- add more), so you will have a lot of tools with which to poke around
- the system.
-
- There are a couple of other ways to log in:
-
- o On a virtual console
-
-
-
- Each virtual console that is configured (i.e. the device exists in
- /dev and /etc/inittab runs a getty on it) will come up in its own
- xterm. If you get tired of the xterms, read ``Setting up serial
- lines and consoles'' to see how to attach the consoles to
- something else, like host ptys.
-
-
-
- o Over the serial line
-
-
- In the boot output, find a line that looks like:
-
-
-
- serial line 0 assigned pty /dev/ptyp1
-
-
-
-
- Attach your favorite terminal program to the corresponding tty. I.e.
- for minicom, the command would be
-
-
- host% minicom -o -p /dev/ttyp1
-
-
-
-
-
-
- o Over the net
-
-
- If the network is running, then you can telnet to the virtual
- machine and log in to it. See ``Setting up the network'' to learn
- about setting up a virtual network.
-
- When you're done using it, run halt, and the kernel will bring itself
- down and the process will exit.
-
-
- 3.3. Examples
-
- Here are some examples of UML in action:
-
- o A login session <http://user-mode-linux.sourceforge.net/login.html>
-
- o A virtual network <http://user-mode-linux.sourceforge.net/net.html>
-
-
-
-
-
-
-
- 4. UML on 2G/2G hosts
-
-
-
-
- 4.1. Introduction
-
-
- Most Linux machines are configured so that the kernel occupies the
- upper 1G (0xc0000000 - 0xffffffff) of the 4G address space and
- processes use the lower 3G (0x00000000 - 0xbfffffff). However, some
- machine are configured with a 2G/2G split, with the kernel occupying
- the upper 2G (0x80000000 - 0xffffffff) and processes using the lower
- 2G (0x00000000 - 0x7fffffff).
-
-
-
-
- 4.2. The problem
-
-
- The prebuilt UML binaries on this site will not run on 2G/2G hosts
- because UML occupies the upper .5G of the 3G process address space
- (0xa0000000 - 0xbfffffff). Obviously, on 2G/2G hosts, this is right
- in the middle of the kernel address space, so UML won't even load - it
- will immediately segfault.
-
-
-
-
- 4.3. The solution
-
-
- The fix for this is to rebuild UML from source after enabling
- CONFIG_HOST_2G_2G (under 'General Setup'). This will cause UML to
- load itself in the top .5G of that smaller process address space,
- where it will run fine. See ``Compiling the kernel and modules'' if
- you need help building UML from source.
-
-
-
-
-
-
-
-
-
-
- 5. Setting up serial lines and consoles
-
-
- It is possible to attach UML serial lines and consoles to many types
- of host I/O channels by specifying them on the command line.
-
-
- You can attach them to host ptys, ttys, file descriptors, and ports.
- This allows you to do things like
-
- o have a UML console appear on an unused host console,
-
- o hook two virtual machines together by having one attach to a pty
- and having the other attach to the corresponding tty
-
- o make a virtual machine accessible from the net by attaching a
- console to a port on the host.
-
-
- The general format of the command line option is device=channel.
-
-
-
- 5.1. Specifying the device
-
- Devices are specified with "con" or "ssl" (console or serial line,
- respectively), optionally with a device number if you are talking
- about a specific device.
-
-
- Using just "con" or "ssl" describes all of the consoles or serial
- lines. If you want to talk about console #3 or serial line #10, they
- would be "con3" and "ssl10", respectively.
-
-
- A specific device name will override a less general "con=" or "ssl=".
- So, for example, you can assign a pty to each of the serial lines
- except for the first two like this:
-
-
- ssl=pty ssl0=tty:/dev/tty0 ssl1=tty:/dev/tty1
-
-
-
-
- The specificity of the device name is all that matters; order on the
- command line is irrelevant.
-
-
-
- 5.2. Specifying the channel
-
- There are a number of different types of channels to attach a UML
- device to, each with a different way of specifying exactly what to
- attach to.
-
- o pseudo-terminals - device=pty pts terminals - device=pts
-
-
- This will cause UML to allocate a free host pseudo-terminal for the
- device. The terminal that it got will be announced in the boot
- log. You access it by attaching a terminal program to the
- corresponding tty:
-
- o screen /dev/pts/n
-
- o screen /dev/ttyxx
-
- o minicom -o -p /dev/ttyxx - minicom seems not able to handle pts
- devices
-
- o kermit - start it up, 'open' the device, then 'connect'
-
-
-
-
-
- o terminals - device=tty:tty device file
-
-
- This will make UML attach the device to the specified tty (i.e
-
-
- con1=tty:/dev/tty3
-
-
-
-
- will attach UML's console 1 to the host's /dev/tty3). If the tty that
- you specify is the slave end of a tty/pty pair, something else must
- have already opened the corresponding pty in order for this to work.
-
-
-
-
-
- o xterms - device=xterm
-
-
- UML will run an xterm and the device will be attached to it.
-
-
-
-
-
- o Port - device=port:port number
-
-
- This will attach the UML devices to the specified host port.
- Attaching console 1 to the host's port 9000 would be done like
- this:
-
-
- con1=port:9000
-
-
-
-
- Attaching all the serial lines to that port would be done similarly:
-
-
- ssl=port:9000
-
-
-
-
- You access these devices by telnetting to that port. Each active tel-
- net session gets a different device. If there are more telnets to a
- port than UML devices attached to it, then the extra telnet sessions
- will block until an existing telnet detaches, or until another device
- becomes active (i.e. by being activated in /etc/inittab).
-
- This channel has the advantage that you can both attach multiple UML
- devices to it and know how to access them without reading the UML boot
- log. It is also unique in allowing access to a UML from remote
- machines without requiring that the UML be networked. This could be
- useful in allowing public access to UMLs because they would be
- accessible from the net, but wouldn't need any kind of network
- filtering or access control because they would have no network access.
-
-
- If you attach the main console to a portal, then the UML boot will
- appear to hang. In reality, it's waiting for a telnet to connect, at
- which point the boot will proceed.
-
-
-
-
-
- o already-existing file descriptors - device=file descriptor
-
-
- If you set up a file descriptor on the UML command line, you can
- attach a UML device to it. This is most commonly used to put the
- main console back on stdin and stdout after assigning all the other
- consoles to something else:
-
-
- con0=fd:0,fd:1 con=pts
-
-
-
-
-
-
-
-
- o Nothing - device=null
-
-
- This allows the device to be opened, in contrast to 'none', but
- reads will block, and writes will succeed and the data will be
- thrown out.
-
-
-
-
-
- o None - device=none
-
-
- This causes the device to disappear.
-
-
-
- You can also specify different input and output channels for a device
- by putting a comma between them:
-
-
- ssl3=tty:/dev/tty2,xterm
-
-
-
-
- will cause serial line 3 to accept input on the host's /dev/tty2 and
- display output on an xterm. That's a silly example - the most common
- use of this syntax is to reattach the main console to stdin and stdout
- as shown above.
-
-
- If you decide to move the main console away from stdin/stdout, the
- initial boot output will appear in the terminal that you're running
- UML in. However, once the console driver has been officially
- initialized, then the boot output will start appearing wherever you
- specified that console 0 should be. That device will receive all
- subsequent output.
-
-
-
- 5.3. Examples
-
- There are a number of interesting things you can do with this
- capability.
-
-
- First, this is how you get rid of those bleeding console xterms by
- attaching them to host ptys:
-
-
- con=pty con0=fd:0,fd:1
-
-
-
-
- This will make a UML console take over an unused host virtual console,
- so that when you switch to it, you will see the UML login prompt
- rather than the host login prompt:
-
-
- con1=tty:/dev/tty6
-
-
-
-
- You can attach two virtual machines together with what amounts to a
- serial line as follows:
-
- Run one UML with a serial line attached to a pty -
-
-
- ssl1=pty
-
-
-
-
- Look at the boot log to see what pty it got (this example will assume
- that it got /dev/ptyp1).
-
- Boot the other UML with a serial line attached to the corresponding
- tty -
-
-
- ssl1=tty:/dev/ttyp1
-
-
-
-
- Log in, make sure that it has no getty on that serial line, attach a
- terminal program like minicom to it, and you should see the login
- prompt of the other virtual machine.
-
-
- 6. Setting up the network
-
-
-
- This page describes how to set up the various transports and to
- provide a UML instance with network access to the host, other machines
- on the local net, and the rest of the net.
-
-
- As of 2.4.5, UML networking has been completely redone to make it much
- easier to set up, fix bugs, and add new features.
-
-
- There is a new helper, uml_net, which does the host setup that
- requires root privileges.
-
-
- There are currently five transport types available for a UML virtual
- machine to exchange packets with other hosts:
-
- o ethertap
-
- o TUN/TAP
-
- o Multicast
-
- o a switch daemon
-
- o slip
-
- o slirp
-
- o pcap
-
- The TUN/TAP, ethertap, slip, and slirp transports allow a UML
- instance to exchange packets with the host. They may be directed
- to the host or the host may just act as a router to provide access
- to other physical or virtual machines.
-
-
- The pcap transport is a synthetic read-only interface, using the
- libpcap binary to collect packets from interfaces on the host and
- filter them. This is useful for building preconfigured traffic
- monitors or sniffers.
-
-
- The daemon and multicast transports provide a completely virtual
- network to other virtual machines. This network is completely
- disconnected from the physical network unless one of the virtual
- machines on it is acting as a gateway.
-
-
- With so many host transports, which one should you use? Here's when
- you should use each one:
-
- o ethertap - if you want access to the host networking and it is
- running 2.2
-
- o TUN/TAP - if you want access to the host networking and it is
- running 2.4. Also, the TUN/TAP transport is able to use a
- preconfigured device, allowing it to avoid using the setuid uml_net
- helper, which is a security advantage.
-
- o Multicast - if you want a purely virtual network and you don't want
- to set up anything but the UML
-
- o a switch daemon - if you want a purely virtual network and you
- don't mind running the daemon in order to get somewhat better
- performance
-
- o slip - there is no particular reason to run the slip backend unless
- ethertap and TUN/TAP are just not available for some reason
-
- o slirp - if you don't have root access on the host to setup
- networking, or if you don't want to allocate an IP to your UML
-
- o pcap - not much use for actual network connectivity, but great for
- monitoring traffic on the host
-
- Ethertap is available on 2.4 and works fine. TUN/TAP is preferred
- to it because it has better performance and ethertap is officially
- considered obsolete in 2.4. Also, the root helper only needs to
- run occasionally for TUN/TAP, rather than handling every packet, as
- it does with ethertap. This is a slight security advantage since
- it provides fewer opportunities for a nasty UML user to somehow
- exploit the helper's root privileges.
-
-
- 6.1. General setup
-
- First, you must have the virtual network enabled in your UML. If are
- running a prebuilt kernel from this site, everything is already
- enabled. If you build the kernel yourself, under the "Network device
- support" menu, enable "Network device support", and then the three
- transports.
-
-
- The next step is to provide a network device to the virtual machine.
- This is done by describing it on the kernel command line.
-
- The general format is
-
-
- eth <n> = <transport> , <transport args>
-
-
-
-
- For example, a virtual ethernet device may be attached to a host
- ethertap device as follows:
-
-
- eth0=ethertap,tap0,fe:fd:0:0:0:1,192.168.0.254
-
-
-
-
- This sets up eth0 inside the virtual machine to attach itself to the
- host /dev/tap0, assigns it an ethernet address, and assigns the host
- tap0 interface an IP address.
-
-
-
- Note that the IP address you assign to the host end of the tap device
- must be different than the IP you assign to the eth device inside UML.
- If you are short on IPs and don't want to consume two per UML, then
- you can reuse the host's eth IP address for the host ends of the tap
- devices. Internally, the UMLs must still get unique IPs for their eth
- devices. You can also give the UMLs non-routable IPs (192.168.x.x or
- 10.x.x.x) and have the host masquerade them. This will let outgoing
- connections work, but incoming connections won't without more work,
- such as port forwarding from the host.
- Also note that when you configure the host side of an interface, it is
- only acting as a gateway. It will respond to pings sent to it
- locally, but is not useful to do that since it's a host interface.
- You are not talking to the UML when you ping that interface and get a
- response.
-
-
- You can also add devices to a UML and remove them at runtime. See the
- ``The Management Console'' page for details.
-
-
- The sections below describe this in more detail.
-
-
- Once you've decided how you're going to set up the devices, you boot
- UML, log in, configure the UML side of the devices, and set up routes
- to the outside world. At that point, you will be able to talk to any
- other machines, physical or virtual, on the net.
-
-
- If ifconfig inside UML fails and the network refuses to come up, run
- tell you what went wrong.
-
-
-
- 6.2. Userspace daemons
-
- You will likely need the setuid helper, or the switch daemon, or both.
- They are both installed with the RPM and deb, so if you've installed
- either, you can skip the rest of this section.
-
-
- If not, then you need to check them out of CVS, build them, and
- install them. The helper is uml_net, in CVS /tools/uml_net, and the
- daemon is uml_switch, in CVS /tools/uml_router. They are both built
- with a plain 'make'. Both need to be installed in a directory that's
- in your path - /usr/bin is recommend. On top of that, uml_net needs
- to be setuid root.
-
-
-
- 6.3. Specifying ethernet addresses
-
- Below, you will see that the TUN/TAP, ethertap, and daemon interfaces
- allow you to specify hardware addresses for the virtual ethernet
- devices. This is generally not necessary. If you don't have a
- specific reason to do it, you probably shouldn't. If one is not
- specified on the command line, the driver will assign one based on the
- device IP address. It will provide the address fe:fd:nn:nn:nn:nn
- where nn.nn.nn.nn is the device IP address. This is nearly always
- sufficient to guarantee a unique hardware address for the device. A
- couple of exceptions are:
-
- o Another set of virtual ethernet devices are on the same network and
- they are assigned hardware addresses using a different scheme which
- may conflict with the UML IP address-based scheme
-
- o You aren't going to use the device for IP networking, so you don't
- assign the device an IP address
-
- If you let the driver provide the hardware address, you should make
- sure that the device IP address is known before the interface is
- brought up. So, inside UML, this will guarantee that:
-
-
-
- UML#
- ifconfig eth0 192.168.0.250 up
-
-
-
-
- If you decide to assign the hardware address yourself, make sure that
- the first byte of the address is even. Addresses with an odd first
- byte are broadcast addresses, which you don't want assigned to a
- device.
-
-
-
- 6.4. UML interface setup
-
- Once the network devices have been described on the command line, you
- should boot UML and log in.
-
-
- The first thing to do is bring the interface up:
-
-
- UML# ifconfig ethn ip-address up
-
-
-
-
- You should be able to ping the host at this point.
-
-
- To reach the rest of the world, you should set a default route to the
- host:
-
-
- UML# route add default gw host ip
-
-
-
-
- Again, with host ip of 192.168.0.4:
-
-
- UML# route add default gw 192.168.0.4
-
-
-
-
- This page used to recommend setting a network route to your local net.
- This is wrong, because it will cause UML to try to figure out hardware
- addresses of the local machines by arping on the interface to the
- host. Since that interface is basically a single strand of ethernet
- with two nodes on it (UML and the host) and arp requests don't cross
- networks, they will fail to elicit any responses. So, what you want
- is for UML to just blindly throw all packets at the host and let it
- figure out what to do with them, which is what leaving out the network
- route and adding the default route does.
-
-
- Note: If you can't communicate with other hosts on your physical
- ethernet, it's probably because of a network route that's
- automatically set up. If you run 'route -n' and see a route that
- looks like this:
-
-
-
-
- Destination Gateway Genmask Flags Metric Ref Use Iface
- 192.168.0.0 0.0.0.0 255.255.255.0 U 0 0 0 eth0
-
-
-
-
- with a mask that's not 255.255.255.255, then replace it with a route
- to your host:
-
-
- UML#
- route del -net 192.168.0.0 dev eth0 netmask 255.255.255.0
-
-
-
-
-
-
- UML#
- route add -host 192.168.0.4 dev eth0
-
-
-
-
- This, plus the default route to the host, will allow UML to exchange
- packets with any machine on your ethernet.
-
-
-
- 6.5. Multicast
-
- The simplest way to set up a virtual network between multiple UMLs is
- to use the mcast transport. This was written by Harald Welte and is
- present in UML version 2.4.5-5um and later. Your system must have
- multicast enabled in the kernel and there must be a multicast-capable
- network device on the host. Normally, this is eth0, but if there is
- no ethernet card on the host, then you will likely get strange error
- messages when you bring the device up inside UML.
-
-
- To use it, run two UMLs with
-
-
- eth0=mcast
-
-
-
-
- on their command lines. Log in, configure the ethernet device in each
- machine with different IP addresses:
-
-
- UML1# ifconfig eth0 192.168.0.254
-
-
-
-
-
-
- UML2# ifconfig eth0 192.168.0.253
-
-
-
-
- and they should be able to talk to each other.
-
- The full set of command line options for this transport are
-
-
-
- ethn=mcast,ethernet address,multicast
- address,multicast port,ttl
-
-
-
-
- Harald's original README is here <http://user-mode-linux.source-
- forge.net/> and explains these in detail, as well as
- some other issues.
-
- There is also a related point-to-point only "ucast" transport.
- This is useful when your network does not support multicast, and
- all network connections are simple point to point links.
-
- The full set of command line options for this transport are
-
-
- ethn=ucast,ethernet address,remote address,listen port,remote port
-
-
-
-
- 6.6. TUN/TAP with the uml_net helper
-
- TUN/TAP is the preferred mechanism on 2.4 to exchange packets with the
- host. The TUN/TAP backend has been in UML since 2.4.9-3um.
-
-
- The easiest way to get up and running is to let the setuid uml_net
- helper do the host setup for you. This involves insmod-ing the tun.o
- module if necessary, configuring the device, and setting up IP
- forwarding, routing, and proxy arp. If you are new to UML networking,
- do this first. If you're concerned about the security implications of
- the setuid helper, use it to get up and running, then read the next
- section to see how to have UML use a preconfigured tap device, which
- avoids the use of uml_net.
-
-
- If you specify an IP address for the host side of the device, the
- uml_net helper will do all necessary setup on the host - the only
- requirement is that TUN/TAP be available, either built in to the host
- kernel or as the tun.o module.
-
- The format of the command line switch to attach a device to a TUN/TAP
- device is
-
-
- eth <n> =tuntap,,, <IP address>
-
-
-
-
- For example, this argument will attach the UML's eth0 to the next
- available tap device and assign an ethernet address to it based on its
- IP address
-
-
- eth0=tuntap,,,192.168.0.254
-
-
-
-
-
-
- Note that the IP address that must be used for the eth device inside
- UML is fixed by the routing and proxy arp that is set up on the
- TUN/TAP device on the host. You can use a different one, but it won't
- work because reply packets won't reach the UML. This is a feature.
- It prevents a nasty UML user from doing things like setting the UML IP
- to the same as the network's nameserver or mail server.
-
-
- There are a couple potential problems with running the TUN/TAP
- transport on a 2.4 host kernel
-
- o TUN/TAP seems not to work on 2.4.3 and earlier. Upgrade the host
- kernel or use the ethertap transport.
-
- o With an upgraded kernel, TUN/TAP may fail with
-
-
- File descriptor in bad state
-
-
-
-
- This is due to a header mismatch between the upgraded kernel and the
- kernel that was originally installed on the machine. The fix is to
- make sure that /usr/src/linux points to the headers for the running
- kernel.
-
- These were pointed out by Tim Robinson <timro at trkr dot net> in
- <http://www.geocrawler.com/> name="this uml-
- user post"> .
-
-
-
- 6.7. TUN/TAP with a preconfigured tap device
-
- If you prefer not to have UML use uml_net (which is somewhat
- insecure), with UML 2.4.17-11, you can set up a TUN/TAP device
- beforehand. The setup needs to be done as root, but once that's done,
- there is no need for root assistance. Setting up the device is done
- as follows:
-
- o Create the device with tunctl (available from the UML utilities
- tarball)
-
-
-
-
- host# tunctl -u uid
-
-
-
-
- where uid is the user id or username that UML will be run as. This
- will tell you what device was created.
-
- o Configure the device IP (change IP addresses and device name to
- suit)
-
-
-
-
- host# ifconfig tap0 192.168.0.254 up
-
-
-
-
-
- o Set up routing and arping if desired - this is my recipe, there are
- other ways of doing the same thing
-
-
- host#
- bash -c 'echo 1 > /proc/sys/net/ipv4/ip_forward'
-
- host#
- route add -host 192.168.0.253 dev tap0
-
-
-
-
-
-
- host#
- bash -c 'echo 1 > /proc/sys/net/ipv4/conf/tap0/proxy_arp'
-
-
-
-
-
-
- host#
- arp -Ds 192.168.0.253 eth0 pub
-
-
-
-
- Note that this must be done every time the host boots - this configu-
- ration is not stored across host reboots. So, it's probably a good
- idea to stick it in an rc file. An even better idea would be a little
- utility which reads the information from a config file and sets up
- devices at boot time.
-
- o Rather than using up two IPs and ARPing for one of them, you can
- also provide direct access to your LAN by the UML by using a
- bridge.
-
-
- host#
- brctl addbr br0
-
-
-
-
-
-
- host#
- ifconfig eth0 0.0.0.0 promisc up
-
-
-
-
-
-
- host#
- ifconfig tap0 0.0.0.0 promisc up
-
-
-
-
-
-
- host#
- ifconfig br0 192.168.0.1 netmask 255.255.255.0 up
-
-
-
-
-
-
-
- host#
- brctl stp br0 off
-
-
-
-
-
-
- host#
- brctl setfd br0 1
-
-
-
-
-
-
- host#
- brctl sethello br0 1
-
-
-
-
-
-
- host#
- brctl addif br0 eth0
-
-
-
-
-
-
- host#
- brctl addif br0 tap0
-
-
-
-
- Note that 'br0' should be setup using ifconfig with the existing IP
- address of eth0, as eth0 no longer has its own IP.
-
- o
-
-
- Also, the /dev/net/tun device must be writable by the user running
- UML in order for the UML to use the device that's been configured
- for it. The simplest thing to do is
-
-
- host# chmod 666 /dev/net/tun
-
-
-
-
- Making it world-writable looks bad, but it seems not to be
- exploitable as a security hole. However, it does allow anyone to cre-
- ate useless tap devices (useless because they can't configure them),
- which is a DOS attack. A somewhat more secure alternative would to be
- to create a group containing all the users who have preconfigured tap
- devices and chgrp /dev/net/tun to that group with mode 664 or 660.
-
-
- o Once the device is set up, run UML with 'eth0=tuntap,device name'
- (i.e. 'eth0=tuntap,tap0') on the command line (or do it with the
- mconsole config command).
-
- o Bring the eth device up in UML and you're in business.
-
- If you don't want that tap device any more, you can make it non-
- persistent with
-
-
- host# tunctl -d tap device
-
-
-
-
- Finally, tunctl has a -b (for brief mode) switch which causes it to
- output only the name of the tap device it created. This makes it
- suitable for capture by a script:
-
-
- host# TAP=`tunctl -u 1000 -b`
-
-
-
-
-
-
- 6.8. Ethertap
-
- Ethertap is the general mechanism on 2.2 for userspace processes to
- exchange packets with the kernel.
-
-
-
- To use this transport, you need to describe the virtual network device
- on the UML command line. The general format for this is
-
-
- eth <n> =ethertap, <device> , <ethernet address> , <tap IP address>
-
-
-
-
- So, the previous example
-
-
- eth0=ethertap,tap0,fe:fd:0:0:0:1,192.168.0.254
-
-
-
-
- attaches the UML eth0 device to the host /dev/tap0, assigns it the
- ethernet address fe:fd:0:0:0:1, and assigns the IP address
- 192.168.0.254 to the tap device.
-
-
-
- The tap device is mandatory, but the others are optional. If the
- ethernet address is omitted, one will be assigned to it.
-
-
- The presence of the tap IP address will cause the helper to run and do
- whatever host setup is needed to allow the virtual machine to
- communicate with the outside world. If you're not sure you know what
- you're doing, this is the way to go.
-
-
- If it is absent, then you must configure the tap device and whatever
- arping and routing you will need on the host. However, even in this
- case, the uml_net helper still needs to be in your path and it must be
- setuid root if you're not running UML as root. This is because the
- tap device doesn't support SIGIO, which UML needs in order to use
- something as a source of input. So, the helper is used as a
- convenient asynchronous IO thread.
-
- If you're using the uml_net helper, you can ignore the following host
- setup - uml_net will do it for you. You just need to make sure you
- have ethertap available, either built in to the host kernel or
- available as a module.
-
-
- If you want to set things up yourself, you need to make sure that the
- appropriate /dev entry exists. If it doesn't, become root and create
- it as follows:
-
-
- mknod /dev/tap <minor> c 36 <minor> + 16
-
-
-
-
- For example, this is how to create /dev/tap0:
-
-
- mknod /dev/tap0 c 36 0 + 16
-
-
-
-
- You also need to make sure that the host kernel has ethertap support.
- If ethertap is enabled as a module, you apparently need to insmod
- ethertap once for each ethertap device you want to enable. So,
-
-
- host#
- insmod ethertap
-
-
-
-
- will give you the tap0 interface. To get the tap1 interface, you need
- to run
-
-
- host#
- insmod ethertap unit=1 -o ethertap1
-
-
-
-
-
-
-
- 6.9. The switch daemon
-
- Note: This is the daemon formerly known as uml_router, but which was
- renamed so the network weenies of the world would stop growling at me.
-
-
- The switch daemon, uml_switch, provides a mechanism for creating a
- totally virtual network. By default, it provides no connection to the
- host network (but see -tap, below).
-
-
- The first thing you need to do is run the daemon. Running it with no
- arguments will make it listen on a default pair of unix domain
- sockets.
-
-
- If you want it to listen on a different pair of sockets, use
-
-
- -unix control socket data socket
-
-
-
-
-
- If you want it to act as a hub rather than a switch, use
-
-
- -hub
-
-
-
-
-
- If you want the switch to be connected to host networking (allowing
- the umls to get access to the outside world through the host), use
-
-
- -tap tap0
-
-
-
-
-
- Note that the tap device must be preconfigured (see "TUN/TAP with a
- preconfigured tap device", above). If you're using a different tap
- device than tap0, specify that instead of tap0.
-
-
- uml_switch can be backgrounded as follows
-
-
- host%
- uml_switch [ options ] < /dev/null > /dev/null
-
-
-
-
- The reason it doesn't background by default is that it listens to
- stdin for EOF. When it sees that, it exits.
-
-
- The general format of the kernel command line switch is
-
-
-
- ethn=daemon,ethernet address,socket
- type,control socket,data socket
-
-
-
-
- You can leave off everything except the 'daemon'. You only need to
- specify the ethernet address if the one that will be assigned to it
- isn't acceptable for some reason. The rest of the arguments describe
- how to communicate with the daemon. You should only specify them if
- you told the daemon to use different sockets than the default. So, if
- you ran the daemon with no arguments, running the UML on the same
- machine with
- eth0=daemon
-
-
-
-
- will cause the eth0 driver to attach itself to the daemon correctly.
-
-
-
- 6.10. Slip
-
- Slip is another, less general, mechanism for a process to communicate
- with the host networking. In contrast to the ethertap interface,
- which exchanges ethernet frames with the host and can be used to
- transport any higher-level protocol, it can only be used to transport
- IP.
-
-
- The general format of the command line switch is
-
-
-
- ethn=slip,slip IP
-
-
-
-
- The slip IP argument is the IP address that will be assigned to the
- host end of the slip device. If it is specified, the helper will run
- and will set up the host so that the virtual machine can reach it and
- the rest of the network.
-
-
- There are some oddities with this interface that you should be aware
- of. You should only specify one slip device on a given virtual
- machine, and its name inside UML will be 'umn', not 'eth0' or whatever
- you specified on the command line. These problems will be fixed at
- some point.
-
-
-
- 6.11. Slirp
-
- slirp uses an external program, usually /usr/bin/slirp, to provide IP
- only networking connectivity through the host. This is similar to IP
- masquerading with a firewall, although the translation is performed in
- user-space, rather than by the kernel. As slirp does not set up any
- interfaces on the host, or changes routing, slirp does not require
- root access or setuid binaries on the host.
-
-
- The general format of the command line switch for slirp is:
-
-
-
- ethn=slirp,ethernet address,slirp path
-
-
-
-
- The ethernet address is optional, as UML will set up the interface
- with an ethernet address based upon the initial IP address of the
- interface. The slirp path is generally /usr/bin/slirp, although it
- will depend on distribution.
-
-
- The slirp program can have a number of options passed to the command
- line and we can't add them to the UML command line, as they will be
- parsed incorrectly. Instead, a wrapper shell script can be written or
- the options inserted into the /.slirprc file. More information on
- all of the slirp options can be found in its man pages.
-
-
- The eth0 interface on UML should be set up with the IP 10.2.0.15,
- although you can use anything as long as it is not used by a network
- you will be connecting to. The default route on UML should be set to
- use
-
-
- UML#
- route add default dev eth0
-
-
-
-
- slirp provides a number of useful IP addresses which can be used by
- UML, such as 10.0.2.3 which is an alias for the DNS server specified
- in /etc/resolv.conf on the host or the IP given in the 'dns' option
- for slirp.
-
-
- Even with a baudrate setting higher than 115200, the slirp connection
- is limited to 115200. If you need it to go faster, the slirp binary
- needs to be compiled with FULL_BOLT defined in config.h.
-
-
-
- 6.12. pcap
-
- The pcap transport is attached to a UML ethernet device on the command
- line or with uml_mconsole with the following syntax:
-
-
-
- ethn=pcap,host interface,filter
- expression,option1,option2
-
-
-
-
- The expression and options are optional.
-
-
- The interface is whatever network device on the host you want to
- sniff. The expression is a pcap filter expression, which is also what
- tcpdump uses, so if you know how to specify tcpdump filters, you will
- use the same expressions here. The options are up to two of
- 'promisc', control whether pcap puts the host interface into
- promiscuous mode. 'optimize' and 'nooptimize' control whether the pcap
- expression optimizer is used.
-
-
- Example:
-
-
-
- eth0=pcap,eth0,tcp
-
- eth1=pcap,eth0,!tcp
-
-
-
- will cause the UML eth0 to emit all tcp packets on the host eth0 and
- the UML eth1 to emit all non-tcp packets on the host eth0.
-
-
-
- 6.13. Setting up the host yourself
-
- If you don't specify an address for the host side of the ethertap or
- slip device, UML won't do any setup on the host. So this is what is
- needed to get things working (the examples use a host-side IP of
- 192.168.0.251 and a UML-side IP of 192.168.0.250 - adjust to suit your
- own network):
-
- o The device needs to be configured with its IP address. Tap devices
- are also configured with an mtu of 1484. Slip devices are
- configured with a point-to-point address pointing at the UML ip
- address.
-
-
- host# ifconfig tap0 arp mtu 1484 192.168.0.251 up
-
-
-
-
-
-
- host#
- ifconfig sl0 192.168.0.251 pointopoint 192.168.0.250 up
-
-
-
-
-
- o If a tap device is being set up, a route is set to the UML IP.
-
-
- UML# route add -host 192.168.0.250 gw 192.168.0.251
-
-
-
-
-
- o To allow other hosts on your network to see the virtual machine,
- proxy arp is set up for it.
-
-
- host# arp -Ds 192.168.0.250 eth0 pub
-
-
-
-
-
- o Finally, the host is set up to route packets.
-
-
- host# echo 1 > /proc/sys/net/ipv4/ip_forward
-
-
-
-
-
-
-
-
-
-
- 7. Sharing Filesystems between Virtual Machines
-
-
-
-
- 7.1. A warning
-
- Don't attempt to share filesystems simply by booting two UMLs from the
- same file. That's the same thing as booting two physical machines
- from a shared disk. It will result in filesystem corruption.
-
-
-
- 7.2. Using layered block devices
-
- The way to share a filesystem between two virtual machines is to use
- the copy-on-write (COW) layering capability of the ubd block driver.
- As of 2.4.6-2um, the driver supports layering a read-write private
- device over a read-only shared device. A machine's writes are stored
- in the private device, while reads come from either device - the
- private one if the requested block is valid in it, the shared one if
- not. Using this scheme, the majority of data which is unchanged is
- shared between an arbitrary number of virtual machines, each of which
- has a much smaller file containing the changes that it has made. With
- a large number of UMLs booting from a large root filesystem, this
- leads to a huge disk space saving. It will also help performance,
- since the host will be able to cache the shared data using a much
- smaller amount of memory, so UML disk requests will be served from the
- host's memory rather than its disks.
-
-
-
-
- To add a copy-on-write layer to an existing block device file, simply
- add the name of the COW file to the appropriate ubd switch:
-
-
- ubd0=root_fs_cow,root_fs_debian_22
-
-
-
-
- where 'root_fs_cow' is the private COW file and 'root_fs_debian_22' is
- the existing shared filesystem. The COW file need not exist. If it
- doesn't, the driver will create and initialize it. Once the COW file
- has been initialized, it can be used on its own on the command line:
-
-
- ubd0=root_fs_cow
-
-
-
-
- The name of the backing file is stored in the COW file header, so it
- would be redundant to continue specifying it on the command line.
-
-
-
- 7.3. Note!
-
- When checking the size of the COW file in order to see the gobs of
- space that you're saving, make sure you use 'ls -ls' to see the actual
- disk consumption rather than the length of the file. The COW file is
- sparse, so the length will be very different from the disk usage.
- Here is a 'ls -l' of a COW file and backing file from one boot and
- shutdown:
- host% ls -l cow.debian debian2.2
- -rw-r--r-- 1 jdike jdike 492504064 Aug 6 21:16 cow.debian
- -rwxrw-rw- 1 jdike jdike 537919488 Aug 6 20:42 debian2.2
-
-
-
-
- Doesn't look like much saved space, does it? Well, here's 'ls -ls':
-
-
- host% ls -ls cow.debian debian2.2
- 880 -rw-r--r-- 1 jdike jdike 492504064 Aug 6 21:16 cow.debian
- 525832 -rwxrw-rw- 1 jdike jdike 537919488 Aug 6 20:42 debian2.2
-
-
-
-
- Now, you can see that the COW file has less than a meg of disk, rather
- than 492 meg.
-
-
-
- 7.4. Another warning
-
- Once a filesystem is being used as a readonly backing file for a COW
- file, do not boot directly from it or modify it in any way. Doing so
- will invalidate any COW files that are using it. The mtime and size
- of the backing file are stored in the COW file header at its creation,
- and they must continue to match. If they don't, the driver will
- refuse to use the COW file.
-
-
-
-
- If you attempt to evade this restriction by changing either the
- backing file or the COW header by hand, you will get a corrupted
- filesystem.
-
-
-
-
- Among other things, this means that upgrading the distribution in a
- backing file and expecting that all of the COW files using it will see
- the upgrade will not work.
-
-
-
-
- 7.5. uml_moo : Merging a COW file with its backing file
-
- Depending on how you use UML and COW devices, it may be advisable to
- merge the changes in the COW file into the backing file every once in
- a while.
-
-
-
-
- The utility that does this is uml_moo. Its usage is
-
-
- host% uml_moo COW file new backing file
-
-
-
-
- There's no need to specify the backing file since that information is
- already in the COW file header. If you're paranoid, boot the new
- merged file, and if you're happy with it, move it over the old backing
- file.
-
-
-
-
- uml_moo creates a new backing file by default as a safety measure. It
- also has a destructive merge option which will merge the COW file
- directly into its current backing file. This is really only usable
- when the backing file only has one COW file associated with it. If
- there are multiple COWs associated with a backing file, a -d merge of
- one of them will invalidate all of the others. However, it is
- convenient if you're short of disk space, and it should also be
- noticeably faster than a non-destructive merge.
-
-
-
-
- uml_moo is installed with the UML deb and RPM. If you didn't install
- UML from one of those packages, you can also get it from the UML
- utilities <http://user-mode-linux.sourceforge.net/
- utilities> tar file in tools/moo.
-
-
-
-
-
-
-
-
- 8. Creating filesystems
-
-
- You may want to create and mount new UML filesystems, either because
- your root filesystem isn't large enough or because you want to use a
- filesystem other than ext2.
-
-
- This was written on the occasion of reiserfs being included in the
- 2.4.1 kernel pool, and therefore the 2.4.1 UML, so the examples will
- talk about reiserfs. This information is generic, and the examples
- should be easy to translate to the filesystem of your choice.
-
-
- 8.1. Create the filesystem file
-
- dd is your friend. All you need to do is tell dd to create an empty
- file of the appropriate size. I usually make it sparse to save time
- and to avoid allocating disk space until it's actually used. For
- example, the following command will create a sparse 100 meg file full
- of zeroes.
-
-
- host%
- dd if=/dev/zero of=new_filesystem seek=100 count=1 bs=1M
-
-
-
-
-
-
- 8.2. Assign the file to a UML device
-
- Add an argument like the following to the UML command line:
-
- ubd4=new_filesystem
-
-
-
-
- making sure that you use an unassigned ubd device number.
-
-
-
- 8.3. Creating and mounting the filesystem
-
- Make sure that the filesystem is available, either by being built into
- the kernel, or available as a module, then boot up UML and log in. If
- the root filesystem doesn't have the filesystem utilities (mkfs, fsck,
- etc), then get them into UML by way of the net or hostfs.
-
-
- Make the new filesystem on the device assigned to the new file:
-
-
- host# mkreiserfs /dev/ubd/4
-
-
- <----------- MKREISERFSv2 ----------->
-
- ReiserFS version 3.6.25
- Block size 4096 bytes
- Block count 25856
- Used blocks 8212
- Journal - 8192 blocks (18-8209), journal header is in block 8210
- Bitmaps: 17
- Root block 8211
- Hash function "r5"
- ATTENTION: ALL DATA WILL BE LOST ON '/dev/ubd/4'! (y/n)y
- journal size 8192 (from 18)
- Initializing journal - 0%....20%....40%....60%....80%....100%
- Syncing..done.
-
-
-
-
- Now, mount it:
-
-
- UML#
- mount /dev/ubd/4 /mnt
-
-
-
-
- and you're in business.
-
-
-
-
-
-
-
-
-
- 9. Host file access
-
-
- If you want to access files on the host machine from inside UML, you
- can treat it as a separate machine and either nfs mount directories
- from the host or copy files into the virtual machine with scp or rcp.
- However, since UML is running on the host, it can access those
- files just like any other process and make them available inside the
- virtual machine without needing to use the network.
-
-
- This is now possible with the hostfs virtual filesystem. With it, you
- can mount a host directory into the UML filesystem and access the
- files contained in it just as you would on the host.
-
-
- 9.1. Using hostfs
-
- To begin with, make sure that hostfs is available inside the virtual
- machine with
-
-
- UML# cat /proc/filesystems
-
-
-
- . hostfs should be listed. If it's not, either rebuild the kernel
- with hostfs configured into it or make sure that hostfs is built as a
- module and available inside the virtual machine, and insmod it.
-
-
- Now all you need to do is run mount:
-
-
- UML# mount none /mnt/host -t hostfs
-
-
-
-
- will mount the host's / on the virtual machine's /mnt/host.
-
-
- If you don't want to mount the host root directory, then you can
- specify a subdirectory to mount with the -o switch to mount:
-
-
- UML# mount none /mnt/home -t hostfs -o /home
-
-
-
-
- will mount the hosts's /home on the virtual machine's /mnt/home.
-
-
-
- 9.2. hostfs as the root filesystem
-
- It's possible to boot from a directory hierarchy on the host using
- hostfs rather than using the standard filesystem in a file.
-
- To start, you need that hierarchy. The easiest way is to loop mount
- an existing root_fs file:
-
-
- host# mount root_fs uml_root_dir -o loop
-
-
-
-
- You need to change the filesystem type of / in etc/fstab to be
- 'hostfs', so that line looks like this:
-
- /dev/ubd/0 / hostfs defaults 1 1
-
-
-
-
- Then you need to chown to yourself all the files in that directory
- that are owned by root. This worked for me:
-
-
- host# find . -uid 0 -exec chown jdike {} \;
-
-
-
-
- Next, make sure that your UML kernel has hostfs compiled in, not as a
- module. Then run UML with the boot device pointing at that directory:
-
-
- ubd0=/path/to/uml/root/directory
-
-
-
-
- UML should then boot as it does normally.
-
-
- 9.3. Building hostfs
-
- If you need to build hostfs because it's not in your kernel, you have
- two choices:
-
-
-
- o Compiling hostfs into the kernel:
-
-
- Reconfigure the kernel and set the 'Host filesystem' option under
-
-
- o Compiling hostfs as a module:
-
-
- Reconfigure the kernel and set the 'Host filesystem' option under
- be in arch/um/fs/hostfs/hostfs.o. Install that in
- /lib/modules/`uname -r`/fs in the virtual machine, boot it up, and
-
-
- UML# insmod hostfs
-
-
-
-
-
-
-
-
-
-
-
-
- 10. The Management Console
-
-
-
- The UML management console is a low-level interface to the kernel,
- somewhat like the i386 SysRq interface. Since there is a full-blown
- operating system under UML, there is much greater flexibility possible
- than with the SysRq mechanism.
-
-
- There are a number of things you can do with the mconsole interface:
-
- o get the kernel version
-
- o add and remove devices
-
- o halt or reboot the machine
-
- o Send SysRq commands
-
- o Pause and resume the UML
-
-
- You need the mconsole client (uml_mconsole) which is present in CVS
- (/tools/mconsole) in 2.4.5-9um and later, and will be in the RPM in
- 2.4.6.
-
-
- You also need CONFIG_MCONSOLE (under 'General Setup') enabled in UML.
- When you boot UML, you'll see a line like:
-
-
- mconsole initialized on /home/jdike/.uml/umlNJ32yL/mconsole
-
-
-
-
- If you specify a unique machine id one the UML command line, i.e.
-
-
- umid=debian
-
-
-
-
- you'll see this
-
-
- mconsole initialized on /home/jdike/.uml/debian/mconsole
-
-
-
-
- That file is the socket that uml_mconsole will use to communicate with
- UML. Run it with either the umid or the full path as its argument:
-
-
- host% uml_mconsole debian
-
-
-
-
- or
-
-
- host% uml_mconsole /home/jdike/.uml/debian/mconsole
-
-
-
-
- You'll get a prompt, at which you can run one of these commands:
-
- o version
-
- o halt
-
- o reboot
-
- o config
-
- o remove
-
- o sysrq
-
- o help
-
- o cad
-
- o stop
-
- o go
-
-
- 10.1. version
-
- This takes no arguments. It prints the UML version.
-
-
- (mconsole) version
- OK Linux usermode 2.4.5-9um #1 Wed Jun 20 22:47:08 EDT 2001 i686
-
-
-
-
- There are a couple actual uses for this. It's a simple no-op which
- can be used to check that a UML is running. It's also a way of
- sending an interrupt to the UML. This is sometimes useful on SMP
- hosts, where there's a bug which causes signals to UML to be lost,
- often causing it to appear to hang. Sending such a UML the mconsole
- version command is a good way to 'wake it up' before networking has
- been enabled, as it does not do anything to the function of the UML.
-
-
-
- 10.2. halt and reboot
-
- These take no arguments. They shut the machine down immediately, with
- no syncing of disks and no clean shutdown of userspace. So, they are
- pretty close to crashing the machine.
-
-
- (mconsole) halt
- OK
-
-
-
-
-
-
- 10.3. config
-
- "config" adds a new device to the virtual machine. Currently the ubd
- and network drivers support this. It takes one argument, which is the
- device to add, with the same syntax as the kernel command line.
-
-
-
-
- (mconsole)
- config ubd3=/home/jdike/incoming/roots/root_fs_debian22
-
- OK
- (mconsole) config eth1=mcast
- OK
-
-
-
-
-
-
- 10.4. remove
-
- "remove" deletes a device from the system. Its argument is just the
- name of the device to be removed. The device must be idle in whatever
- sense the driver considers necessary. In the case of the ubd driver,
- the removed block device must not be mounted, swapped on, or otherwise
- open, and in the case of the network driver, the device must be down.
-
-
- (mconsole) remove ubd3
- OK
- (mconsole) remove eth1
- OK
-
-
-
-
-
-
- 10.5. sysrq
-
- This takes one argument, which is a single letter. It calls the
- generic kernel's SysRq driver, which does whatever is called for by
- that argument. See the SysRq documentation in
- Documentation/admin-guide/sysrq.rst in your favorite kernel tree to
- see what letters are valid and what they do.
-
-
-
- 10.6. help
-
- "help" returns a string listing the valid commands and what each one
- does.
-
-
-
- 10.7. cad
-
- This invokes the Ctl-Alt-Del action on init. What exactly this ends
- up doing is up to /etc/inittab. Normally, it reboots the machine.
- With UML, this is usually not desired, so if a halt would be better,
- then find the section of inittab that looks like this
-
-
- # What to do when CTRL-ALT-DEL is pressed.
- ca:12345:ctrlaltdel:/sbin/shutdown -t1 -a -r now
-
-
-
-
- and change the command to halt.
-
-
-
- 10.8. stop
-
- This puts the UML in a loop reading mconsole requests until a 'go'
- mconsole command is received. This is very useful for making backups
- of UML filesystems, as the UML can be stopped, then synced via 'sysrq
- s', so that everything is written to the filesystem. You can then copy
- the filesystem and then send the UML 'go' via mconsole.
-
-
- Note that a UML running with more than one CPU will have problems
- after you send the 'stop' command, as only one CPU will be held in a
- mconsole loop and all others will continue as normal. This is a bug,
- and will be fixed.
-
-
-
- 10.9. go
-
- This resumes a UML after being paused by a 'stop' command. Note that
- when the UML has resumed, TCP connections may have timed out and if
- the UML is paused for a long period of time, crond might go a little
- crazy, running all the jobs it didn't do earlier.
-
-
-
-
-
-
-
-
- 11. Kernel debugging
-
-
- Note: The interface that makes debugging, as described here, possible
- is present in 2.4.0-test6 kernels and later.
-
-
- Since the user-mode kernel runs as a normal Linux process, it is
- possible to debug it with gdb almost like any other process. It is
- slightly different because the kernel's threads are already being
- ptraced for system call interception, so gdb can't ptrace them.
- However, a mechanism has been added to work around that problem.
-
-
- In order to debug the kernel, you need build it from source. See
- ``Compiling the kernel and modules'' for information on doing that.
- Make sure that you enable CONFIG_DEBUGSYM and CONFIG_PT_PROXY during
- the config. These will compile the kernel with -g, and enable the
- ptrace proxy so that gdb works with UML, respectively.
-
-
-
-
- 11.1. Starting the kernel under gdb
-
- You can have the kernel running under the control of gdb from the
- beginning by putting 'debug' on the command line. You will get an
- xterm with gdb running inside it. The kernel will send some commands
- to gdb which will leave it stopped at the beginning of start_kernel.
- At this point, you can get things going with 'next', 'step', or
- 'cont'.
-
-
- There is a transcript of a debugging session here <debug-
- session.html> , with breakpoints being set in the scheduler and in an
- interrupt handler.
- 11.2. Examining sleeping processes
-
- Not every bug is evident in the currently running process. Sometimes,
- processes hang in the kernel when they shouldn't because they've
- deadlocked on a semaphore or something similar. In this case, when
- you ^C gdb and get a backtrace, you will see the idle thread, which
- isn't very relevant.
-
-
- What you want is the stack of whatever process is sleeping when it
- shouldn't be. You need to figure out which process that is, which is
- generally fairly easy. Then you need to get its host process id,
- which you can do either by looking at ps on the host or at
- task.thread.extern_pid in gdb.
-
-
- Now what you do is this:
-
- o detach from the current thread
-
-
- (UML gdb) det
-
-
-
-
-
- o attach to the thread you are interested in
-
-
- (UML gdb) att <host pid>
-
-
-
-
-
- o look at its stack and anything else of interest
-
-
- (UML gdb) bt
-
-
-
-
- Note that you can't do anything at this point that requires that a
- process execute, e.g. calling a function
-
- o when you're done looking at that process, reattach to the current
- thread and continue it
-
-
- (UML gdb)
- att 1
-
-
-
-
-
-
- (UML gdb)
- c
-
-
-
-
- Here, specifying any pid which is not the process id of a UML thread
- will cause gdb to reattach to the current thread. I commonly use 1,
- but any other invalid pid would work.
-
-
-
- 11.3. Running ddd on UML
-
- ddd works on UML, but requires a special kludge. The process goes
- like this:
-
- o Start ddd
-
-
- host% ddd linux
-
-
-
-
-
- o With ps, get the pid of the gdb that ddd started. You can ask the
- gdb to tell you, but for some reason that confuses things and
- causes a hang.
-
- o run UML with 'debug=parent gdb-pid=<pid>' added to the command line
- - it will just sit there after you hit return
-
- o type 'att 1' to the ddd gdb and you will see something like
-
-
- 0xa013dc51 in __kill ()
-
-
- (gdb)
-
-
-
-
-
- o At this point, type 'c', UML will boot up, and you can use ddd just
- as you do on any other process.
-
-
-
- 11.4. Debugging modules
-
- gdb has support for debugging code which is dynamically loaded into
- the process. This support is what is needed to debug kernel modules
- under UML.
-
-
- Using that support is somewhat complicated. You have to tell gdb what
- object file you just loaded into UML and where in memory it is. Then,
- it can read the symbol table, and figure out where all the symbols are
- from the load address that you provided. It gets more interesting
- when you load the module again (i.e. after an rmmod). You have to
- tell gdb to forget about all its symbols, including the main UML ones
- for some reason, then load then all back in again.
-
-
- There's an easy way and a hard way to do this. The easy way is to use
- the umlgdb expect script written by Chandan Kudige. It basically
- automates the process for you.
-
-
- First, you must tell it where your modules are. There is a list in
- the script that looks like this:
- set MODULE_PATHS {
- "fat" "/usr/src/uml/linux-2.4.18/fs/fat/fat.o"
- "isofs" "/usr/src/uml/linux-2.4.18/fs/isofs/isofs.o"
- "minix" "/usr/src/uml/linux-2.4.18/fs/minix/minix.o"
- }
-
-
-
-
- You change that to list the names and paths of the modules that you
- are going to debug. Then you run it from the toplevel directory of
- your UML pool and it basically tells you what to do:
-
-
-
-
- ******** GDB pid is 21903 ********
- Start UML as: ./linux <kernel switches> debug gdb-pid=21903
-
-
-
- GNU gdb 5.0rh-5 Red Hat Linux 7.1
- Copyright 2001 Free Software Foundation, Inc.
- GDB is free software, covered by the GNU General Public License, and you are
- welcome to change it and/or distribute copies of it under certain conditions.
- Type "show copying" to see the conditions.
- There is absolutely no warranty for GDB. Type "show warranty" for details.
- This GDB was configured as "i386-redhat-linux"...
- (gdb) b sys_init_module
- Breakpoint 1 at 0xa0011923: file module.c, line 349.
- (gdb) att 1
-
-
-
-
- After you run UML and it sits there doing nothing, you hit return at
- the 'att 1' and continue it:
-
-
- Attaching to program: /home/jdike/linux/2.4/um/./linux, process 1
- 0xa00f4221 in __kill ()
- (UML gdb) c
- Continuing.
-
-
-
-
- At this point, you debug normally. When you insmod something, the
- expect magic will kick in and you'll see something like:
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
- *** Module hostfs loaded ***
- Breakpoint 1, sys_init_module (name_user=0x805abb0 "hostfs",
- mod_user=0x8070e00) at module.c:349
- 349 char *name, *n_name, *name_tmp = NULL;
- (UML gdb) finish
- Run till exit from #0 sys_init_module (name_user=0x805abb0 "hostfs",
- mod_user=0x8070e00) at module.c:349
- 0xa00e2e23 in execute_syscall (r=0xa8140284) at syscall_kern.c:411
- 411 else res = EXECUTE_SYSCALL(syscall, regs);
- Value returned is $1 = 0
- (UML gdb)
- p/x (int)module_list + module_list->size_of_struct
-
- $2 = 0xa9021054
- (UML gdb) symbol-file ./linux
- Load new symbol table from "./linux"? (y or n) y
- Reading symbols from ./linux...
- done.
- (UML gdb)
- add-symbol-file /home/jdike/linux/2.4/um/arch/um/fs/hostfs/hostfs.o 0xa9021054
-
- add symbol table from file "/home/jdike/linux/2.4/um/arch/um/fs/hostfs/hostfs.o" at
- .text_addr = 0xa9021054
- (y or n) y
-
- Reading symbols from /home/jdike/linux/2.4/um/arch/um/fs/hostfs/hostfs.o...
- done.
- (UML gdb) p *module_list
- $1 = {size_of_struct = 84, next = 0xa0178720, name = 0xa9022de0 "hostfs",
- size = 9016, uc = {usecount = {counter = 0}, pad = 0}, flags = 1,
- nsyms = 57, ndeps = 0, syms = 0xa9023170, deps = 0x0, refs = 0x0,
- init = 0xa90221f0 <init_hostfs>, cleanup = 0xa902222c <exit_hostfs>,
- ex_table_start = 0x0, ex_table_end = 0x0, persist_start = 0x0,
- persist_end = 0x0, can_unload = 0, runsize = 0, kallsyms_start = 0x0,
- kallsyms_end = 0x0,
- archdata_start = 0x1b855 <Address 0x1b855 out of bounds>,
- archdata_end = 0xe5890000 <Address 0xe5890000 out of bounds>,
- kernel_data = 0xf689c35d <Address 0xf689c35d out of bounds>}
- >> Finished loading symbols for hostfs ...
-
-
-
-
- That's the easy way. It's highly recommended. The hard way is
- described below in case you're interested in what's going on.
-
-
- Boot the kernel under the debugger and load the module with insmod or
- modprobe. With gdb, do:
-
-
- (UML gdb) p module_list
-
-
-
-
- This is a list of modules that have been loaded into the kernel, with
- the most recently loaded module first. Normally, the module you want
- is at module_list. If it's not, walk down the next links, looking at
- the name fields until find the module you want to debug. Take the
- address of that structure, and add module.size_of_struct (which in
- 2.4.10 kernels is 96 (0x60)) to it. Gdb can make this hard addition
- for you :-):
-
-
-
- (UML gdb)
- printf "%#x\n", (int)module_list module_list->size_of_struct
-
-
-
-
- The offset from the module start occasionally changes (before 2.4.0,
- it was module.size_of_struct + 4), so it's a good idea to check the
- init and cleanup addresses once in a while, as describe below. Now
- do:
-
-
- (UML gdb)
- add-symbol-file /path/to/module/on/host that_address
-
-
-
-
- Tell gdb you really want to do it, and you're in business.
-
-
- If there's any doubt that you got the offset right, like breakpoints
- appear not to work, or they're appearing in the wrong place, you can
- check it by looking at the module structure. The init and cleanup
- fields should look like:
-
-
- init = 0x588066b0 <init_hostfs>, cleanup = 0x588066c0 <exit_hostfs>
-
-
-
-
- with no offsets on the symbol names. If the names are right, but they
- are offset, then the offset tells you how much you need to add to the
- address you gave to add-symbol-file.
-
-
- When you want to load in a new version of the module, you need to get
- gdb to forget about the old one. The only way I've found to do that
- is to tell gdb to forget about all symbols that it knows about:
-
-
- (UML gdb) symbol-file
-
-
-
-
- Then reload the symbols from the kernel binary:
-
-
- (UML gdb) symbol-file /path/to/kernel
-
-
-
-
- and repeat the process above. You'll also need to re-enable break-
- points. They were disabled when you dumped all the symbols because
- gdb couldn't figure out where they should go.
-
-
-
- 11.5. Attaching gdb to the kernel
-
- If you don't have the kernel running under gdb, you can attach gdb to
- it later by sending the tracing thread a SIGUSR1. The first line of
- the console output identifies its pid:
- tracing thread pid = 20093
-
-
-
-
- When you send it the signal:
-
-
- host% kill -USR1 20093
-
-
-
-
- you will get an xterm with gdb running in it.
-
-
- If you have the mconsole compiled into UML, then the mconsole client
- can be used to start gdb:
-
-
- (mconsole) (mconsole) config gdb=xterm
-
-
-
-
- will fire up an xterm with gdb running in it.
-
-
-
- 11.6. Using alternate debuggers
-
- UML has support for attaching to an already running debugger rather
- than starting gdb itself. This is present in CVS as of 17 Apr 2001.
- I sent it to Alan for inclusion in the ac tree, and it will be in my
- 2.4.4 release.
-
-
- This is useful when gdb is a subprocess of some UI, such as emacs or
- ddd. It can also be used to run debuggers other than gdb on UML.
- Below is an example of using strace as an alternate debugger.
-
-
- To do this, you need to get the pid of the debugger and pass it in
- with the
-
-
- If you are using gdb under some UI, then tell it to 'att 1', and
- you'll find yourself attached to UML.
-
-
- If you are using something other than gdb as your debugger, then
- you'll need to get it to do the equivalent of 'att 1' if it doesn't do
- it automatically.
-
-
- An example of an alternate debugger is strace. You can strace the
- actual kernel as follows:
-
- o Run the following in a shell
-
-
- host%
- sh -c 'echo pid=$$; echo -n hit return; read x; exec strace -p 1 -o strace.out'
-
-
-
- o Run UML with 'debug' and 'gdb-pid=<pid>' with the pid printed out
- by the previous command
-
- o Hit return in the shell, and UML will start running, and strace
- output will start accumulating in the output file.
-
- Note that this is different from running
-
-
- host% strace ./linux
-
-
-
-
- That will strace only the main UML thread, the tracing thread, which
- doesn't do any of the actual kernel work. It just oversees the vir-
- tual machine. In contrast, using strace as described above will show
- you the low-level activity of the virtual machine.
-
-
-
-
-
- 12. Kernel debugging examples
-
- 12.1. The case of the hung fsck
-
- When booting up the kernel, fsck failed, and dropped me into a shell
- to fix things up. I ran fsck -y, which hung:
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
- Setting hostname uml [ OK ]
- Checking root filesystem
- /dev/fhd0 was not cleanly unmounted, check forced.
- Error reading block 86894 (Attempt to read block from filesystem resulted in short read) while reading indirect blocks of inode 19780.
-
- /dev/fhd0: UNEXPECTED INCONSISTENCY; RUN fsck MANUALLY.
- (i.e., without -a or -p options)
- [ FAILED ]
-
- *** An error occurred during the file system check.
- *** Dropping you to a shell; the system will reboot
- *** when you leave the shell.
- Give root password for maintenance
- (or type Control-D for normal startup):
-
- [root@uml /root]# fsck -y /dev/fhd0
- fsck -y /dev/fhd0
- Parallelizing fsck version 1.14 (9-Jan-1999)
- e2fsck 1.14, 9-Jan-1999 for EXT2 FS 0.5b, 95/08/09
- /dev/fhd0 contains a file system with errors, check forced.
- Pass 1: Checking inodes, blocks, and sizes
- Error reading block 86894 (Attempt to read block from filesystem resulted in short read) while reading indirect blocks of inode 19780. Ignore error? yes
-
- Inode 19780, i_blocks is 1548, should be 540. Fix? yes
-
- Pass 2: Checking directory structure
- Error reading block 49405 (Attempt to read block from filesystem resulted in short read). Ignore error? yes
-
- Directory inode 11858, block 0, offset 0: directory corrupted
- Salvage? yes
-
- Missing '.' in directory inode 11858.
- Fix? yes
-
- Missing '..' in directory inode 11858.
- Fix? yes
-
-
-
-
-
- The standard drill in this sort of situation is to fire up gdb on the
- signal thread, which, in this case, was pid 1935. In another window,
- I run gdb and attach pid 1935.
-
-
-
-
- ~/linux/2.3.26/um 1016: gdb linux
- GNU gdb 4.17.0.11 with Linux support
- Copyright 1998 Free Software Foundation, Inc.
- GDB is free software, covered by the GNU General Public License, and you are
- welcome to change it and/or distribute copies of it under certain conditions.
- Type "show copying" to see the conditions.
- There is absolutely no warranty for GDB. Type "show warranty" for details.
- This GDB was configured as "i386-redhat-linux"...
-
- (gdb) att 1935
- Attaching to program `/home/dike/linux/2.3.26/um/linux', Pid 1935
- 0x100756d9 in __wait4 ()
-
-
-
-
-
-
- Let's see what's currently running:
-
-
-
- (gdb) p current_task.pid
- $1 = 0
-
-
-
-
-
- It's the idle thread, which means that fsck went to sleep for some
- reason and never woke up.
-
-
- Let's guess that the last process in the process list is fsck:
-
-
-
- (gdb) p current_task.prev_task.comm
- $13 = "fsck.ext2\000\000\000\000\000\000"
-
-
-
-
-
- It is, so let's see what it thinks it's up to:
-
-
-
- (gdb) p current_task.prev_task.thread
- $14 = {extern_pid = 1980, tracing = 0, want_tracing = 0, forking = 0,
- kernel_stack_page = 0, signal_stack = 1342627840, syscall = {id = 4, args = {
- 3, 134973440, 1024, 0, 1024}, have_result = 0, result = 50590720},
- request = {op = 2, u = {exec = {ip = 1350467584, sp = 2952789424}, fork = {
- regs = {1350467584, 2952789424, 0 <repeats 15 times>}, sigstack = 0,
- pid = 0}, switch_to = 0x507e8000, thread = {proc = 0x507e8000,
- arg = 0xaffffdb0, flags = 0, new_pid = 0}, input_request = {
- op = 1350467584, fd = -1342177872, proc = 0, pid = 0}}}}
-
-
-
-
-
- The interesting things here are the fact that its .thread.syscall.id
- is __NR_write (see the big switch in arch/um/kernel/syscall_kern.c or
- the defines in include/asm-um/arch/unistd.h), and that it never
- returned. Also, its .request.op is OP_SWITCH (see
- arch/um/include/user_util.h). These mean that it went into a write,
- and, for some reason, called schedule().
-
-
- The fact that it never returned from write means that its stack should
- be fairly interesting. Its pid is 1980 (.thread.extern_pid). That
- process is being ptraced by the signal thread, so it must be detached
- before gdb can attach it:
-
-
-
-
-
-
-
-
-
-
- (gdb) call detach(1980)
-
- Program received signal SIGSEGV, Segmentation fault.
- <function called from gdb>
- The program being debugged stopped while in a function called from GDB.
- When the function (detach) is done executing, GDB will silently
- stop (instead of continuing to evaluate the expression containing
- the function call).
- (gdb) call detach(1980)
- $15 = 0
-
-
-
-
-
- The first detach segfaults for some reason, and the second one
- succeeds.
-
-
- Now I detach from the signal thread, attach to the fsck thread, and
- look at its stack:
-
-
- (gdb) det
- Detaching from program: /home/dike/linux/2.3.26/um/linux Pid 1935
- (gdb) att 1980
- Attaching to program `/home/dike/linux/2.3.26/um/linux', Pid 1980
- 0x10070451 in __kill ()
- (gdb) bt
- #0 0x10070451 in __kill ()
- #1 0x10068ccd in usr1_pid (pid=1980) at process.c:30
- #2 0x1006a03f in _switch_to (prev=0x50072000, next=0x507e8000)
- at process_kern.c:156
- #3 0x1006a052 in switch_to (prev=0x50072000, next=0x507e8000, last=0x50072000)
- at process_kern.c:161
- #4 0x10001d12 in schedule () at core.c:777
- #5 0x1006a744 in __down (sem=0x507d241c) at semaphore.c:71
- #6 0x1006aa10 in __down_failed () at semaphore.c:157
- #7 0x1006c5d8 in segv_handler (sc=0x5006e940) at trap_user.c:174
- #8 0x1006c5ec in kern_segv_handler (sig=11) at trap_user.c:182
- #9 <signal handler called>
- #10 0x10155404 in errno ()
- #11 0x1006c0aa in segv (address=1342179328, is_write=2) at trap_kern.c:50
- #12 0x1006c5d8 in segv_handler (sc=0x5006eaf8) at trap_user.c:174
- #13 0x1006c5ec in kern_segv_handler (sig=11) at trap_user.c:182
- #14 <signal handler called>
- #15 0xc0fd in ?? ()
- #16 0x10016647 in sys_write (fd=3,
- buf=0x80b8800 <Address 0x80b8800 out of bounds>, count=1024)
- at read_write.c:159
- #17 0x1006d5b3 in execute_syscall (syscall=4, args=0x5006ef08)
- at syscall_kern.c:254
- #18 0x1006af87 in really_do_syscall (sig=12) at syscall_user.c:35
- #19 <signal handler called>
- #20 0x400dc8b0 in ?? ()
-
-
-
-
-
- The interesting things here are :
-
- o There are two segfaults on this stack (frames 9 and 14)
-
- o The first faulting address (frame 11) is 0x50000800
-
- (gdb) p (void *)1342179328
- $16 = (void *) 0x50000800
-
-
-
-
-
- The initial faulting address is interesting because it is on the idle
- thread's stack. I had been seeing the idle thread segfault for no
- apparent reason, and the cause looked like stack corruption. In hopes
- of catching the culprit in the act, I had turned off all protections
- to that stack while the idle thread wasn't running. This apparently
- tripped that trap.
-
-
- However, the more immediate problem is that second segfault and I'm
- going to concentrate on that. First, I want to see where the fault
- happened, so I have to go look at the sigcontent struct in frame 8:
-
-
-
- (gdb) up
- #1 0x10068ccd in usr1_pid (pid=1980) at process.c:30
- 30 kill(pid, SIGUSR1);
- (gdb)
- #2 0x1006a03f in _switch_to (prev=0x50072000, next=0x507e8000)
- at process_kern.c:156
- 156 usr1_pid(getpid());
- (gdb)
- #3 0x1006a052 in switch_to (prev=0x50072000, next=0x507e8000, last=0x50072000)
- at process_kern.c:161
- 161 _switch_to(prev, next);
- (gdb)
- #4 0x10001d12 in schedule () at core.c:777
- 777 switch_to(prev, next, prev);
- (gdb)
- #5 0x1006a744 in __down (sem=0x507d241c) at semaphore.c:71
- 71 schedule();
- (gdb)
- #6 0x1006aa10 in __down_failed () at semaphore.c:157
- 157 }
- (gdb)
- #7 0x1006c5d8 in segv_handler (sc=0x5006e940) at trap_user.c:174
- 174 segv(sc->cr2, sc->err & 2);
- (gdb)
- #8 0x1006c5ec in kern_segv_handler (sig=11) at trap_user.c:182
- 182 segv_handler(sc);
- (gdb) p *sc
- Cannot access memory at address 0x0.
-
-
-
-
- That's not very useful, so I'll try a more manual method:
-
-
- (gdb) p *((struct sigcontext *) (&sig + 1))
- $19 = {gs = 0, __gsh = 0, fs = 0, __fsh = 0, es = 43, __esh = 0, ds = 43,
- __dsh = 0, edi = 1342179328, esi = 1350378548, ebp = 1342630440,
- esp = 1342630420, ebx = 1348150624, edx = 1280, ecx = 0, eax = 0,
- trapno = 14, err = 4, eip = 268480945, cs = 35, __csh = 0, eflags = 66118,
- esp_at_signal = 1342630420, ss = 43, __ssh = 0, fpstate = 0x0, oldmask = 0,
- cr2 = 1280}
-
-
-
- The ip is in handle_mm_fault:
-
-
- (gdb) p (void *)268480945
- $20 = (void *) 0x1000b1b1
- (gdb) i sym $20
- handle_mm_fault + 57 in section .text
-
-
-
-
-
- Specifically, it's in pte_alloc:
-
-
- (gdb) i line *$20
- Line 124 of "/home/dike/linux/2.3.26/um/include/asm/pgalloc.h"
- starts at address 0x1000b1b1 <handle_mm_fault+57>
- and ends at 0x1000b1b7 <handle_mm_fault+63>.
-
-
-
-
-
- To find where in handle_mm_fault this is, I'll jump forward in the
- code until I see an address in that procedure:
-
-
-
- (gdb) i line *0x1000b1c0
- Line 126 of "/home/dike/linux/2.3.26/um/include/asm/pgalloc.h"
- starts at address 0x1000b1b7 <handle_mm_fault+63>
- and ends at 0x1000b1c3 <handle_mm_fault+75>.
- (gdb) i line *0x1000b1d0
- Line 131 of "/home/dike/linux/2.3.26/um/include/asm/pgalloc.h"
- starts at address 0x1000b1d0 <handle_mm_fault+88>
- and ends at 0x1000b1da <handle_mm_fault+98>.
- (gdb) i line *0x1000b1e0
- Line 61 of "/home/dike/linux/2.3.26/um/include/asm/pgalloc.h"
- starts at address 0x1000b1da <handle_mm_fault+98>
- and ends at 0x1000b1e1 <handle_mm_fault+105>.
- (gdb) i line *0x1000b1f0
- Line 134 of "/home/dike/linux/2.3.26/um/include/asm/pgalloc.h"
- starts at address 0x1000b1f0 <handle_mm_fault+120>
- and ends at 0x1000b200 <handle_mm_fault+136>.
- (gdb) i line *0x1000b200
- Line 135 of "/home/dike/linux/2.3.26/um/include/asm/pgalloc.h"
- starts at address 0x1000b200 <handle_mm_fault+136>
- and ends at 0x1000b208 <handle_mm_fault+144>.
- (gdb) i line *0x1000b210
- Line 139 of "/home/dike/linux/2.3.26/um/include/asm/pgalloc.h"
- starts at address 0x1000b210 <handle_mm_fault+152>
- and ends at 0x1000b219 <handle_mm_fault+161>.
- (gdb) i line *0x1000b220
- Line 1168 of "memory.c" starts at address 0x1000b21e <handle_mm_fault+166>
- and ends at 0x1000b222 <handle_mm_fault+170>.
-
-
-
-
-
- Something is apparently wrong with the page tables or vma_structs, so
- lets go back to frame 11 and have a look at them:
-
-
-
- #11 0x1006c0aa in segv (address=1342179328, is_write=2) at trap_kern.c:50
- 50 handle_mm_fault(current, vma, address, is_write);
- (gdb) call pgd_offset_proc(vma->vm_mm, address)
- $22 = (pgd_t *) 0x80a548c
-
-
-
-
-
- That's pretty bogus. Page tables aren't supposed to be in process
- text or data areas. Let's see what's in the vma:
-
-
- (gdb) p *vma
- $23 = {vm_mm = 0x507d2434, vm_start = 0, vm_end = 134512640,
- vm_next = 0x80a4f8c, vm_page_prot = {pgprot = 0}, vm_flags = 31200,
- vm_avl_height = 2058, vm_avl_left = 0x80a8c94, vm_avl_right = 0x80d1000,
- vm_next_share = 0xaffffdb0, vm_pprev_share = 0xaffffe63,
- vm_ops = 0xaffffe7a, vm_pgoff = 2952789626, vm_file = 0xafffffec,
- vm_private_data = 0x62}
- (gdb) p *vma.vm_mm
- $24 = {mmap = 0x507d2434, mmap_avl = 0x0, mmap_cache = 0x8048000,
- pgd = 0x80a4f8c, mm_users = {counter = 0}, mm_count = {counter = 134904288},
- map_count = 134909076, mmap_sem = {count = {counter = 135073792},
- sleepers = -1342177872, wait = {lock = <optimized out or zero length>,
- task_list = {next = 0xaffffe63, prev = 0xaffffe7a},
- __magic = -1342177670, __creator = -1342177300}, __magic = 98},
- page_table_lock = {}, context = 138, start_code = 0, end_code = 0,
- start_data = 0, end_data = 0, start_brk = 0, brk = 0, start_stack = 0,
- arg_start = 0, arg_end = 0, env_start = 0, env_end = 0, rss = 1350381536,
- total_vm = 0, locked_vm = 0, def_flags = 0, cpu_vm_mask = 0, swap_cnt = 0,
- swap_address = 0, segments = 0x0}
-
-
-
-
-
- This also pretty bogus. With all of the 0x80xxxxx and 0xaffffxxx
- addresses, this is looking like a stack was plonked down on top of
- these structures. Maybe it's a stack overflow from the next page:
-
-
-
- (gdb) p vma
- $25 = (struct vm_area_struct *) 0x507d2434
-
-
-
-
-
- That's towards the lower quarter of the page, so that would have to
- have been pretty heavy stack overflow:
-
-
-
-
-
-
-
-
-
-
-
-
-
-
- (gdb) x/100x $25
- 0x507d2434: 0x507d2434 0x00000000 0x08048000 0x080a4f8c
- 0x507d2444: 0x00000000 0x080a79e0 0x080a8c94 0x080d1000
- 0x507d2454: 0xaffffdb0 0xaffffe63 0xaffffe7a 0xaffffe7a
- 0x507d2464: 0xafffffec 0x00000062 0x0000008a 0x00000000
- 0x507d2474: 0x00000000 0x00000000 0x00000000 0x00000000
- 0x507d2484: 0x00000000 0x00000000 0x00000000 0x00000000
- 0x507d2494: 0x00000000 0x00000000 0x507d2fe0 0x00000000
- 0x507d24a4: 0x00000000 0x00000000 0x00000000 0x00000000
- 0x507d24b4: 0x00000000 0x00000000 0x00000000 0x00000000
- 0x507d24c4: 0x00000000 0x00000000 0x00000000 0x00000000
- 0x507d24d4: 0x00000000 0x00000000 0x00000000 0x00000000
- 0x507d24e4: 0x00000000 0x00000000 0x00000000 0x00000000
- 0x507d24f4: 0x00000000 0x00000000 0x00000000 0x00000000
- 0x507d2504: 0x00000000 0x00000000 0x00000000 0x00000000
- 0x507d2514: 0x00000000 0x00000000 0x00000000 0x00000000
- 0x507d2524: 0x00000000 0x00000000 0x00000000 0x00000000
- 0x507d2534: 0x00000000 0x00000000 0x507d25dc 0x00000000
- 0x507d2544: 0x00000000 0x00000000 0x00000000 0x00000000
- 0x507d2554: 0x00000000 0x00000000 0x00000000 0x00000000
- 0x507d2564: 0x00000000 0x00000000 0x00000000 0x00000000
- 0x507d2574: 0x00000000 0x00000000 0x00000000 0x00000000
- 0x507d2584: 0x00000000 0x00000000 0x00000000 0x00000000
- 0x507d2594: 0x00000000 0x00000000 0x00000000 0x00000000
- 0x507d25a4: 0x00000000 0x00000000 0x00000000 0x00000000
- 0x507d25b4: 0x00000000 0x00000000 0x00000000 0x00000000
-
-
-
-
-
- It's not stack overflow. The only "stack-like" piece of this data is
- the vma_struct itself.
-
-
- At this point, I don't see any avenues to pursue, so I just have to
- admit that I have no idea what's going on. What I will do, though, is
- stick a trap on the segfault handler which will stop if it sees any
- writes to the idle thread's stack. That was the thing that happened
- first, and it may be that if I can catch it immediately, what's going
- on will be somewhat clearer.
-
-
- 12.2. Episode 2: The case of the hung fsck
-
- After setting a trap in the SEGV handler for accesses to the signal
- thread's stack, I reran the kernel.
-
-
- fsck hung again, this time by hitting the trap:
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
- Setting hostname uml [ OK ]
- Checking root filesystem
- /dev/fhd0 contains a file system with errors, check forced.
- Error reading block 86894 (Attempt to read block from filesystem resulted in short read) while reading indirect blocks of inode 19780.
-
- /dev/fhd0: UNEXPECTED INCONSISTENCY; RUN fsck MANUALLY.
- (i.e., without -a or -p options)
- [ FAILED ]
-
- *** An error occurred during the file system check.
- *** Dropping you to a shell; the system will reboot
- *** when you leave the shell.
- Give root password for maintenance
- (or type Control-D for normal startup):
-
- [root@uml /root]# fsck -y /dev/fhd0
- fsck -y /dev/fhd0
- Parallelizing fsck version 1.14 (9-Jan-1999)
- e2fsck 1.14, 9-Jan-1999 for EXT2 FS 0.5b, 95/08/09
- /dev/fhd0 contains a file system with errors, check forced.
- Pass 1: Checking inodes, blocks, and sizes
- Error reading block 86894 (Attempt to read block from filesystem resulted in short read) while reading indirect blocks of inode 19780. Ignore error? yes
-
- Pass 2: Checking directory structure
- Error reading block 49405 (Attempt to read block from filesystem resulted in short read). Ignore error? yes
-
- Directory inode 11858, block 0, offset 0: directory corrupted
- Salvage? yes
-
- Missing '.' in directory inode 11858.
- Fix? yes
-
- Missing '..' in directory inode 11858.
- Fix? yes
-
- Untested (4127) [100fe44c]: trap_kern.c line 31
-
-
-
-
-
- I need to get the signal thread to detach from pid 4127 so that I can
- attach to it with gdb. This is done by sending it a SIGUSR1, which is
- caught by the signal thread, which detaches the process:
-
-
- kill -USR1 4127
-
-
-
-
-
- Now I can run gdb on it:
-
-
-
-
-
-
-
-
-
-
-
-
-
- ~/linux/2.3.26/um 1034: gdb linux
- GNU gdb 4.17.0.11 with Linux support
- Copyright 1998 Free Software Foundation, Inc.
- GDB is free software, covered by the GNU General Public License, and you are
- welcome to change it and/or distribute copies of it under certain conditions.
- Type "show copying" to see the conditions.
- There is absolutely no warranty for GDB. Type "show warranty" for details.
- This GDB was configured as "i386-redhat-linux"...
- (gdb) att 4127
- Attaching to program `/home/dike/linux/2.3.26/um/linux', Pid 4127
- 0x10075891 in __libc_nanosleep ()
-
-
-
-
-
- The backtrace shows that it was in a write and that the fault address
- (address in frame 3) is 0x50000800, which is right in the middle of
- the signal thread's stack page:
-
-
- (gdb) bt
- #0 0x10075891 in __libc_nanosleep ()
- #1 0x1007584d in __sleep (seconds=1000000)
- at ../sysdeps/unix/sysv/linux/sleep.c:78
- #2 0x1006ce9a in stop () at user_util.c:191
- #3 0x1006bf88 in segv (address=1342179328, is_write=2) at trap_kern.c:31
- #4 0x1006c628 in segv_handler (sc=0x5006eaf8) at trap_user.c:174
- #5 0x1006c63c in kern_segv_handler (sig=11) at trap_user.c:182
- #6 <signal handler called>
- #7 0xc0fd in ?? ()
- #8 0x10016647 in sys_write (fd=3, buf=0x80b8800 "R.", count=1024)
- at read_write.c:159
- #9 0x1006d603 in execute_syscall (syscall=4, args=0x5006ef08)
- at syscall_kern.c:254
- #10 0x1006af87 in really_do_syscall (sig=12) at syscall_user.c:35
- #11 <signal handler called>
- #12 0x400dc8b0 in ?? ()
- #13 <signal handler called>
- #14 0x400dc8b0 in ?? ()
- #15 0x80545fd in ?? ()
- #16 0x804daae in ?? ()
- #17 0x8054334 in ?? ()
- #18 0x804d23e in ?? ()
- #19 0x8049632 in ?? ()
- #20 0x80491d2 in ?? ()
- #21 0x80596b5 in ?? ()
- (gdb) p (void *)1342179328
- $3 = (void *) 0x50000800
-
-
-
-
-
- Going up the stack to the segv_handler frame and looking at where in
- the code the access happened shows that it happened near line 110 of
- block_dev.c:
-
-
-
-
-
-
-
-
-
- (gdb) up
- #1 0x1007584d in __sleep (seconds=1000000)
- at ../sysdeps/unix/sysv/linux/sleep.c:78
- ../sysdeps/unix/sysv/linux/sleep.c:78: No such file or directory.
- (gdb)
- #2 0x1006ce9a in stop () at user_util.c:191
- 191 while(1) sleep(1000000);
- (gdb)
- #3 0x1006bf88 in segv (address=1342179328, is_write=2) at trap_kern.c:31
- 31 KERN_UNTESTED();
- (gdb)
- #4 0x1006c628 in segv_handler (sc=0x5006eaf8) at trap_user.c:174
- 174 segv(sc->cr2, sc->err & 2);
- (gdb) p *sc
- $1 = {gs = 0, __gsh = 0, fs = 0, __fsh = 0, es = 43, __esh = 0, ds = 43,
- __dsh = 0, edi = 1342179328, esi = 134973440, ebp = 1342631484,
- esp = 1342630864, ebx = 256, edx = 0, ecx = 256, eax = 1024, trapno = 14,
- err = 6, eip = 268550834, cs = 35, __csh = 0, eflags = 66070,
- esp_at_signal = 1342630864, ss = 43, __ssh = 0, fpstate = 0x0, oldmask = 0,
- cr2 = 1342179328}
- (gdb) p (void *)268550834
- $2 = (void *) 0x1001c2b2
- (gdb) i sym $2
- block_write + 1090 in section .text
- (gdb) i line *$2
- Line 209 of "/home/dike/linux/2.3.26/um/include/asm/arch/string.h"
- starts at address 0x1001c2a1 <block_write+1073>
- and ends at 0x1001c2bf <block_write+1103>.
- (gdb) i line *0x1001c2c0
- Line 110 of "block_dev.c" starts at address 0x1001c2bf <block_write+1103>
- and ends at 0x1001c2e3 <block_write+1139>.
-
-
-
-
-
- Looking at the source shows that the fault happened during a call to
- copy_from_user to copy the data into the kernel:
-
-
- 107 count -= chars;
- 108 copy_from_user(p,buf,chars);
- 109 p += chars;
- 110 buf += chars;
-
-
-
-
-
- p is the pointer which must contain 0x50000800, since buf contains
- 0x80b8800 (frame 8 above). It is defined as:
-
-
- p = offset + bh->b_data;
-
-
-
-
-
- I need to figure out what bh is, and it just so happens that bh is
- passed as an argument to mark_buffer_uptodate and mark_buffer_dirty a
- few lines later, so I do a little disassembly:
-
-
-
-
- (gdb) disas 0x1001c2bf 0x1001c2e0
- Dump of assembler code from 0x1001c2bf to 0x1001c2d0:
- 0x1001c2bf <block_write+1103>: addl %eax,0xc(%ebp)
- 0x1001c2c2 <block_write+1106>: movl 0xfffffdd4(%ebp),%edx
- 0x1001c2c8 <block_write+1112>: btsl $0x0,0x18(%edx)
- 0x1001c2cd <block_write+1117>: btsl $0x1,0x18(%edx)
- 0x1001c2d2 <block_write+1122>: sbbl %ecx,%ecx
- 0x1001c2d4 <block_write+1124>: testl %ecx,%ecx
- 0x1001c2d6 <block_write+1126>: jne 0x1001c2e3 <block_write+1139>
- 0x1001c2d8 <block_write+1128>: pushl $0x0
- 0x1001c2da <block_write+1130>: pushl %edx
- 0x1001c2db <block_write+1131>: call 0x1001819c <__mark_buffer_dirty>
- End of assembler dump.
-
-
-
-
-
- At that point, bh is in %edx (address 0x1001c2da), which is calculated
- at 0x1001c2c2 as %ebp + 0xfffffdd4, so I figure exactly what that is,
- taking %ebp from the sigcontext_struct above:
-
-
- (gdb) p (void *)1342631484
- $5 = (void *) 0x5006ee3c
- (gdb) p 0x5006ee3c+0xfffffdd4
- $6 = 1342630928
- (gdb) p (void *)$6
- $7 = (void *) 0x5006ec10
- (gdb) p *((void **)$7)
- $8 = (void *) 0x50100200
-
-
-
-
-
- Now, I look at the structure to see what's in it, and particularly,
- what its b_data field contains:
-
-
- (gdb) p *((struct buffer_head *)0x50100200)
- $13 = {b_next = 0x50289380, b_blocknr = 49405, b_size = 1024, b_list = 0,
- b_dev = 15872, b_count = {counter = 1}, b_rdev = 15872, b_state = 24,
- b_flushtime = 0, b_next_free = 0x501001a0, b_prev_free = 0x50100260,
- b_this_page = 0x501001a0, b_reqnext = 0x0, b_pprev = 0x507fcf58,
- b_data = 0x50000800 "", b_page = 0x50004000,
- b_end_io = 0x10017f60 <end_buffer_io_sync>, b_dev_id = 0x0,
- b_rsector = 98810, b_wait = {lock = <optimized out or zero length>,
- task_list = {next = 0x50100248, prev = 0x50100248}, __magic = 1343226448,
- __creator = 0}, b_kiobuf = 0x0}
-
-
-
-
-
- The b_data field is indeed 0x50000800, so the question becomes how
- that happened. The rest of the structure looks fine, so this probably
- is not a case of data corruption. It happened on purpose somehow.
-
-
- The b_page field is a pointer to the page_struct representing the
- 0x50000000 page. Looking at it shows the kernel's idea of the state
- of that page:
-
-
-
- (gdb) p *$13.b_page
- $17 = {list = {next = 0x50004a5c, prev = 0x100c5174}, mapping = 0x0,
- index = 0, next_hash = 0x0, count = {counter = 1}, flags = 132, lru = {
- next = 0x50008460, prev = 0x50019350}, wait = {
- lock = <optimized out or zero length>, task_list = {next = 0x50004024,
- prev = 0x50004024}, __magic = 1342193708, __creator = 0},
- pprev_hash = 0x0, buffers = 0x501002c0, virtual = 1342177280,
- zone = 0x100c5160}
-
-
-
-
-
- Some sanity-checking: the virtual field shows the "virtual" address of
- this page, which in this kernel is the same as its "physical" address,
- and the page_struct itself should be mem_map[0], since it represents
- the first page of memory:
-
-
-
- (gdb) p (void *)1342177280
- $18 = (void *) 0x50000000
- (gdb) p mem_map
- $19 = (mem_map_t *) 0x50004000
-
-
-
-
-
- These check out fine.
-
-
- Now to check out the page_struct itself. In particular, the flags
- field shows whether the page is considered free or not:
-
-
- (gdb) p (void *)132
- $21 = (void *) 0x84
-
-
-
-
-
- The "reserved" bit is the high bit, which is definitely not set, so
- the kernel considers the signal stack page to be free and available to
- be used.
-
-
- At this point, I jump to conclusions and start looking at my early
- boot code, because that's where that page is supposed to be reserved.
-
-
- In my setup_arch procedure, I have the following code which looks just
- fine:
-
-
-
- bootmap_size = init_bootmem(start_pfn, end_pfn - start_pfn);
- free_bootmem(__pa(low_physmem) + bootmap_size, high_physmem - low_physmem);
-
-
-
-
-
- Two stack pages have already been allocated, and low_physmem points to
- the third page, which is the beginning of free memory.
- The init_bootmem call declares the entire memory to the boot memory
- manager, which marks it all reserved. The free_bootmem call frees up
- all of it, except for the first two pages. This looks correct to me.
-
-
- So, I decide to see init_bootmem run and make sure that it is marking
- those first two pages as reserved. I never get that far.
-
-
- Stepping into init_bootmem, and looking at bootmem_map before looking
- at what it contains shows the following:
-
-
-
- (gdb) p bootmem_map
- $3 = (void *) 0x50000000
-
-
-
-
-
- Aha! The light dawns. That first page is doing double duty as a
- stack and as the boot memory map. The last thing that the boot memory
- manager does is to free the pages used by its memory map, so this page
- is getting freed even its marked as reserved.
-
-
- The fix was to initialize the boot memory manager before allocating
- those two stack pages, and then allocate them through the boot memory
- manager. After doing this, and fixing a couple of subsequent buglets,
- the stack corruption problem disappeared.
-
-
-
-
-
- 13. What to do when UML doesn't work
-
-
-
-
- 13.1. Strange compilation errors when you build from source
-
- As of test11, it is necessary to have "ARCH=um" in the environment or
- on the make command line for all steps in building UML, including
- clean, distclean, or mrproper, config, menuconfig, or xconfig, dep,
- and linux. If you forget for any of them, the i386 build seems to
- contaminate the UML build. If this happens, start from scratch with
-
-
- host%
- make mrproper ARCH=um
-
-
-
-
- and repeat the build process with ARCH=um on all the steps.
-
-
- See ``Compiling the kernel and modules'' for more details.
-
-
- Another cause of strange compilation errors is building UML in
- /usr/src/linux. If you do this, the first thing you need to do is
- clean up the mess you made. The /usr/src/linux/asm link will now
- point to /usr/src/linux/asm-um. Make it point back to
- /usr/src/linux/asm-i386. Then, move your UML pool someplace else and
- build it there. Also see below, where a more specific set of symptoms
- is described.
-
-
-
- 13.3. A variety of panics and hangs with /tmp on a reiserfs filesys-
- tem
-
- I saw this on reiserfs 3.5.21 and it seems to be fixed in 3.5.27.
- Panics preceded by
-
-
- Detaching pid nnnn
-
-
-
- are diagnostic of this problem. This is a reiserfs bug which causes a
- thread to occasionally read stale data from a mmapped page shared with
- another thread. The fix is to upgrade the filesystem or to have /tmp
- be an ext2 filesystem.
-
-
-
- 13.4. The compile fails with errors about conflicting types for
- 'open', 'dup', and 'waitpid'
-
- This happens when you build in /usr/src/linux. The UML build makes
- the include/asm link point to include/asm-um. /usr/include/asm points
- to /usr/src/linux/include/asm, so when that link gets moved, files
- which need to include the asm-i386 versions of headers get the
- incompatible asm-um versions. The fix is to move the include/asm link
- back to include/asm-i386 and to do UML builds someplace else.
-
-
-
- 13.5. UML doesn't work when /tmp is an NFS filesystem
-
- This seems to be a similar situation with the ReiserFS problem above.
- Some versions of NFS seems not to handle mmap correctly, which UML
- depends on. The workaround is have /tmp be a non-NFS directory.
-
-
- 13.6. UML hangs on boot when compiled with gprof support
-
- If you build UML with gprof support and, early in the boot, it does
- this
-
-
- kernel BUG at page_alloc.c:100!
-
-
-
-
- you have a buggy gcc. You can work around the problem by removing
- UM_FASTCALL from CFLAGS in arch/um/Makefile-i386. This will open up
- another bug, but that one is fairly hard to reproduce.
-
-
-
- 13.7. syslogd dies with a SIGTERM on startup
-
- The exact boot error depends on the distribution that you're booting,
- but Debian produces this:
-
-
- /etc/rc2.d/S10sysklogd: line 49: 93 Terminated
- start-stop-daemon --start --quiet --exec /sbin/syslogd -- $SYSLOGD
-
-
-
-
- This is a syslogd bug. There's a race between a parent process
- installing a signal handler and its child sending the signal. See
- this uml-devel post <http://www.geocrawler.com/lists/3/Source-
- Forge/709/0/6612801> for the details.
-
-
-
- 13.8. TUN/TAP networking doesn't work on a 2.4 host
-
- There are a couple of problems which were
- <http://www.geocrawler.com/lists/3/SourceForge/597/0/> name="pointed
- out"> by Tim Robinson <timro at trkr dot net>
-
- o It doesn't work on hosts running 2.4.7 (or thereabouts) or earlier.
- The fix is to upgrade to something more recent and then read the
- next item.
-
- o If you see
-
-
- File descriptor in bad state
-
-
-
- when you bring up the device inside UML, you have a header mismatch
- between the original kernel and the upgraded one. Make /usr/src/linux
- point at the new headers. This will only be a problem if you build
- uml_net yourself.
-
-
-
- 13.9. You can network to the host but not to other machines on the
- net
-
- If you can connect to the host, and the host can connect to UML, but
- you cannot connect to any other machines, then you may need to enable
- IP Masquerading on the host. Usually this is only experienced when
- using private IP addresses (192.168.x.x or 10.x.x.x) for host/UML
- networking, rather than the public address space that your host is
- connected to. UML does not enable IP Masquerading, so you will need
- to create a static rule to enable it:
-
-
- host%
- iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE
-
-
-
-
- Replace eth0 with the interface that you use to talk to the rest of
- the world.
-
-
- Documentation on IP Masquerading, and SNAT, can be found at
- www.netfilter.org <http://www.netfilter.org> .
-
-
- If you can reach the local net, but not the outside Internet, then
- that is usually a routing problem. The UML needs a default route:
-
-
- UML#
- route add default gw gateway IP
-
-
-
-
- The gateway IP can be any machine on the local net that knows how to
- reach the outside world. Usually, this is the host or the local net-
- work's gateway.
-
-
- Occasionally, we hear from someone who can reach some machines, but
- not others on the same net, or who can reach some ports on other
- machines, but not others. These are usually caused by strange
- firewalling somewhere between the UML and the other box. You track
- this down by running tcpdump on every interface the packets travel
- over and see where they disappear. When you find a machine that takes
- the packets in, but does not send them onward, that's the culprit.
-
-
-
- 13.10. I have no root and I want to scream
-
- Thanks to Birgit Wahlich for telling me about this strange one. It
- turns out that there's a limit of six environment variables on the
- kernel command line. When that limit is reached or exceeded, argument
- processing stops, which means that the 'root=' argument that UML
- usually adds is not seen. So, the filesystem has no idea what the
- root device is, so it panics.
-
-
- The fix is to put less stuff on the command line. Glomming all your
- setup variables into one is probably the best way to go.
-
-
-
- 13.11. UML build conflict between ptrace.h and ucontext.h
-
- On some older systems, /usr/include/asm/ptrace.h and
- /usr/include/sys/ucontext.h define the same names. So, when they're
- included together, the defines from one completely mess up the parsing
- of the other, producing errors like:
- /usr/include/sys/ucontext.h:47: parse error before
- `10'
-
-
-
-
- plus a pile of warnings.
-
-
- This is a libc botch, which has since been fixed, and I don't see any
- way around it besides upgrading.
-
-
-
- 13.12. The UML BogoMips is exactly half the host's BogoMips
-
- On i386 kernels, there are two ways of running the loop that is used
- to calculate the BogoMips rating, using the TSC if it's there or using
- a one-instruction loop. The TSC produces twice the BogoMips as the
- loop. UML uses the loop, since it has nothing resembling a TSC, and
- will get almost exactly the same BogoMips as a host using the loop.
- However, on a host with a TSC, its BogoMips will be double the loop
- BogoMips, and therefore double the UML BogoMips.
-
-
-
- 13.13. When you run UML, it immediately segfaults
-
- If the host is configured with the 2G/2G address space split, that's
- why. See ``UML on 2G/2G hosts'' for the details on getting UML to
- run on your host.
-
-
-
- 13.14. xterms appear, then immediately disappear
-
- If you're running an up to date kernel with an old release of
- uml_utilities, the port-helper program will not work properly, so
- xterms will exit straight after they appear. The solution is to
- upgrade to the latest release of uml_utilities. Usually this problem
- occurs when you have installed a packaged release of UML then compiled
- your own development kernel without upgrading the uml_utilities from
- the source distribution.
-
-
-
- 13.15. Any other panic, hang, or strange behavior
-
- If you're seeing truly strange behavior, such as hangs or panics that
- happen in random places, or you try running the debugger to see what's
- happening and it acts strangely, then it could be a problem in the
- host kernel. If you're not running a stock Linus or -ac kernel, then
- try that. An early version of the preemption patch and a 2.4.10 SuSE
- kernel have caused very strange problems in UML.
-
-
- Otherwise, let me know about it. Send a message to one of the UML
- mailing lists - either the developer list - user-mode-linux-devel at
- lists dot sourceforge dot net (subscription info) or the user list -
- user-mode-linux-user at lists dot sourceforge do net (subscription
- info), whichever you prefer. Don't assume that everyone knows about
- it and that a fix is imminent.
-
-
- If you want to be super-helpful, read ``Diagnosing Problems'' and
- follow the instructions contained therein.
- 14. Diagnosing Problems
-
-
- If you get UML to crash, hang, or otherwise misbehave, you should
- report this on one of the project mailing lists, either the developer
- list - user-mode-linux-devel at lists dot sourceforge dot net
- (subscription info) or the user list - user-mode-linux-user at lists
- dot sourceforge dot net (subscription info). When you do, it is
- likely that I will want more information. So, it would be helpful to
- read the stuff below, do whatever is applicable in your case, and
- report the results to the list.
-
-
- For any diagnosis, you're going to need to build a debugging kernel.
- The binaries from this site aren't debuggable. If you haven't done
- this before, read about ``Compiling the kernel and modules'' and
- ``Kernel debugging'' UML first.
-
-
- 14.1. Case 1 : Normal kernel panics
-
- The most common case is for a normal thread to panic. To debug this,
- you will need to run it under the debugger (add 'debug' to the command
- line). An xterm will start up with gdb running inside it. Continue
- it when it stops in start_kernel and make it crash. Now ^C gdb and
-
-
- If the panic was a "Kernel mode fault", then there will be a segv
- frame on the stack and I'm going to want some more information. The
- stack might look something like this:
-
-
- (UML gdb) backtrace
- #0 0x1009bf76 in __sigprocmask (how=1, set=0x5f347940, oset=0x0)
- at ../sysdeps/unix/sysv/linux/sigprocmask.c:49
- #1 0x10091411 in change_sig (signal=10, on=1) at process.c:218
- #2 0x10094785 in timer_handler (sig=26) at time_kern.c:32
- #3 0x1009bf38 in __restore ()
- at ../sysdeps/unix/sysv/linux/i386/sigaction.c:125
- #4 0x1009534c in segv (address=8, ip=268849158, is_write=2, is_user=0)
- at trap_kern.c:66
- #5 0x10095c04 in segv_handler (sig=11) at trap_user.c:285
- #6 0x1009bf38 in __restore ()
-
-
-
-
- I'm going to want to see the symbol and line information for the value
- of ip in the segv frame. In this case, you would do the following:
-
-
- (UML gdb) i sym 268849158
-
-
-
-
- and
-
-
- (UML gdb) i line *268849158
-
-
-
-
- The reason for this is the __restore frame right above the segv_han-
- dler frame is hiding the frame that actually segfaulted. So, I have
- to get that information from the faulting ip.
-
-
- 14.2. Case 2 : Tracing thread panics
-
- The less common and more painful case is when the tracing thread
- panics. In this case, the kernel debugger will be useless because it
- needs a healthy tracing thread in order to work. The first thing to
- do is get a backtrace from the tracing thread. This is done by
- figuring out what its pid is, firing up gdb, and attaching it to that
- pid. You can figure out the tracing thread pid by looking at the
- first line of the console output, which will look like this:
-
-
- tracing thread pid = 15851
-
-
-
-
- or by running ps on the host and finding the line that looks like
- this:
-
-
- jdike 15851 4.5 0.4 132568 1104 pts/0 S 21:34 0:05 ./linux [(tracing thread)]
-
-
-
-
- If the panic was 'segfault in signals', then follow the instructions
- above for collecting information about the location of the seg fault.
-
-
- If the tracing thread flaked out all by itself, then send that
- backtrace in and wait for our crack debugging team to fix the problem.
-
-
- 14.3. Case 3 : Tracing thread panics caused by other threads
-
- However, there are cases where the misbehavior of another thread
- caused the problem. The most common panic of this type is:
-
-
- wait_for_stop failed to wait for <pid> to stop with <signal number>
-
-
-
-
- In this case, you'll need to get a backtrace from the process men-
- tioned in the panic, which is complicated by the fact that the kernel
- debugger is defunct and without some fancy footwork, another gdb can't
- attach to it. So, this is how the fancy footwork goes:
-
- In a shell:
-
-
- host% kill -STOP pid
-
-
-
-
- Run gdb on the tracing thread as described in case 2 and do:
-
-
- (host gdb) call detach(pid)
-
-
- If you get a segfault, do it again. It always works the second time.
-
- Detach from the tracing thread and attach to that other thread:
-
-
- (host gdb) detach
-
-
-
-
-
-
- (host gdb) attach pid
-
-
-
-
- If gdb hangs when attaching to that process, go back to a shell and
- do:
-
-
- host%
- kill -CONT pid
-
-
-
-
- And then get the backtrace:
-
-
- (host gdb) backtrace
-
-
-
-
-
- 14.4. Case 4 : Hangs
-
- Hangs seem to be fairly rare, but they sometimes happen. When a hang
- happens, we need a backtrace from the offending process. Run the
- kernel debugger as described in case 1 and get a backtrace. If the
- current process is not the idle thread, then send in the backtrace.
- You can tell that it's the idle thread if the stack looks like this:
-
-
- #0 0x100b1401 in __libc_nanosleep ()
- #1 0x100a2885 in idle_sleep (secs=10) at time.c:122
- #2 0x100a546f in do_idle () at process_kern.c:445
- #3 0x100a5508 in cpu_idle () at process_kern.c:471
- #4 0x100ec18f in start_kernel () at init/main.c:592
- #5 0x100a3e10 in start_kernel_proc (unused=0x0) at um_arch.c:71
- #6 0x100a383f in signal_tramp (arg=0x100a3dd8) at trap_user.c:50
-
-
-
-
- If this is the case, then some other process is at fault, and went to
- sleep when it shouldn't have. Run ps on the host and figure out which
- process should not have gone to sleep and stayed asleep. Then attach
- to it with gdb and get a backtrace as described in case 3.
-
-
-
-
-
-
- 15. Thanks
-
-
- A number of people have helped this project in various ways, and this
- page gives recognition where recognition is due.
-
-
- If you're listed here and you would prefer a real link on your name,
- or no link at all, instead of the despammed email address pseudo-link,
- let me know.
-
-
- If you're not listed here and you think maybe you should be, please
- let me know that as well. I try to get everyone, but sometimes my
- bookkeeping lapses and I forget about contributions.
-
-
- 15.1. Code and Documentation
-
- Rusty Russell <rusty at linuxcare.com.au> -
-
- o wrote the HOWTO <http://user-mode-
- linux.sourceforge.net/UserModeLinux-HOWTO.html>
-
- o prodded me into making this project official and putting it on
- SourceForge
-
- o came up with the way cool UML logo <http://user-mode-
- linux.sourceforge.net/uml-small.png>
-
- o redid the config process
-
-
- Peter Moulder <reiter at netspace.net.au> - Fixed my config and build
- processes, and added some useful code to the block driver
-
-
- Bill Stearns <wstearns at pobox.com> -
-
- o HOWTO updates
-
- o lots of bug reports
-
- o lots of testing
-
- o dedicated a box (uml.ists.dartmouth.edu) to support UML development
-
- o wrote the mkrootfs script, which allows bootable filesystems of
- RPM-based distributions to be cranked out
-
- o cranked out a large number of filesystems with said script
-
-
- Jim Leu <jleu at mindspring.com> - Wrote the virtual ethernet driver
- and associated usermode tools
-
- Lars Brinkhoff <http://lars.nocrew.org/> - Contributed the ptrace
- proxy from his own project <http://a386.nocrew.org/> to allow easier
- kernel debugging
-
-
- Andrea Arcangeli <andrea at suse.de> - Redid some of the early boot
- code so that it would work on machines with Large File Support
-
-
- Chris Emerson <http://www.chiark.greenend.org.uk/~cemerson/> - Did
- the first UML port to Linux/ppc
-
-
- Harald Welte <laforge at gnumonks.org> - Wrote the multicast
- transport for the network driver
-
-
- Jorgen Cederlof - Added special file support to hostfs
-
-
- Greg Lonnon <glonnon at ridgerun dot com> - Changed the ubd driver
- to allow it to layer a COW file on a shared read-only filesystem and
- wrote the iomem emulation support
-
-
- Henrik Nordstrom <http://hem.passagen.se/hno/> - Provided a variety
- of patches, fixes, and clues
-
-
- Lennert Buytenhek - Contributed various patches, a rewrite of the
- network driver, the first implementation of the mconsole driver, and
- did the bulk of the work needed to get SMP working again.
-
-
- Yon Uriarte - Fixed the TUN/TAP network backend while I slept.
-
-
- Adam Heath - Made a bunch of nice cleanups to the initialization code,
- plus various other small patches.
-
-
- Matt Zimmerman - Matt volunteered to be the UML Debian maintainer and
- is doing a real nice job of it. He also noticed and fixed a number of
- actually and potentially exploitable security holes in uml_net. Plus
- the occasional patch. I like patches.
-
-
- James McMechan - James seems to have taken over maintenance of the ubd
- driver and is doing a nice job of it.
-
-
- Chandan Kudige - wrote the umlgdb script which automates the reloading
- of module symbols.
-
-
- Steve Schmidtke - wrote the UML slirp transport and hostaudio drivers,
- enabling UML processes to access audio devices on the host. He also
- submitted patches for the slip transport and lots of other things.
-
-
- David Coulson <http://davidcoulson.net> -
-
- o Set up the usermodelinux.org <http://usermodelinux.org> site,
- which is a great way of keeping the UML user community on top of
- UML goings-on.
-
- o Site documentation and updates
-
- o Nifty little UML management daemon UMLd
- <http://uml.openconsultancy.com/umld/>
-
- o Lots of testing and bug reports
-
-
-
-
- 15.2. Flushing out bugs
-
-
-
- o Yuri Pudgorodsky
-
- o Gerald Britton
-
- o Ian Wehrman
-
- o Gord Lamb
-
- o Eugene Koontz
-
- o John H. Hartman
-
- o Anders Karlsson
-
- o Daniel Phillips
-
- o John Fremlin
-
- o Rainer Burgstaller
-
- o James Stevenson
-
- o Matt Clay
-
- o Cliff Jefferies
-
- o Geoff Hoff
-
- o Lennert Buytenhek
-
- o Al Viro
-
- o Frank Klingenhoefer
-
- o Livio Baldini Soares
-
- o Jon Burgess
-
- o Petru Paler
-
- o Paul
-
- o Chris Reahard
-
- o Sverker Nilsson
-
- o Gong Su
-
- o johan verrept
-
- o Bjorn Eriksson
-
- o Lorenzo Allegrucci
-
- o Muli Ben-Yehuda
-
- o David Mansfield
-
- o Howard Goff
-
- o Mike Anderson
-
- o John Byrne
-
- o Sapan J. Batia
-
- o Iris Huang
-
- o Jan Hudec
-
- o Voluspa
-
-
-
-
- 15.3. Buglets and clean-ups
-
-
-
- o Dave Zarzycki
-
- o Adam Lazur
-
- o Boria Feigin
-
- o Brian J. Murrell
-
- o JS
-
- o Roman Zippel
-
- o Wil Cooley
-
- o Ayelet Shemesh
-
- o Will Dyson
-
- o Sverker Nilsson
-
- o dvorak
-
- o v.naga srinivas
-
- o Shlomi Fish
-
- o Roger Binns
-
- o johan verrept
-
- o MrChuoi
-
- o Peter Cleve
-
- o Vincent Guffens
-
- o Nathan Scott
-
- o Patrick Caulfield
-
- o jbearce
-
- o Catalin Marinas
-
- o Shane Spencer
-
- o Zou Min
-
-
- o Ryan Boder
-
- o Lorenzo Colitti
-
- o Gwendal Grignou
-
- o Andre' Breiler
-
- o Tsutomu Yasuda
-
-
-
- 15.4. Case Studies
-
-
- o Jon Wright
-
- o William McEwan
-
- o Michael Richardson
-
-
-
- 15.5. Other contributions
-
-
- Bill Carr <Bill.Carr at compaq.com> made the Red Hat mkrootfs script
- work with RH 6.2.
-
- Michael Jennings <mikejen at hevanet.com> sent in some material which
- is now gracing the top of the index page <http://user-mode-
- linux.sourceforge.net/> of this site.
-
- SGI <http://www.sgi.com> (and more specifically Ralf Baechle <ralf at
- uni-koblenz.de> ) gave me an account on oss.sgi.com
- <http://www.oss.sgi.com> . The bandwidth there made it possible to
- produce most of the filesystems available on the project download
- page.
-
- Laurent Bonnaud <Laurent.Bonnaud at inpg.fr> took the old grotty
- Debian filesystem that I've been distributing and updated it to 2.2.
- It is now available by itself here.
-
- Rik van Riel gave me some ftp space on ftp.nl.linux.org so I can make
- releases even when Sourceforge is broken.
-
- Rodrigo de Castro looked at my broken pte code and told me what was
- wrong with it, letting me fix a long-standing (several weeks) and
- serious set of bugs.
-
- Chris Reahard built a specialized root filesystem for running a DNS
- server jailed inside UML. It's available from the download
- <http://user-mode-linux.sourceforge.net/dl-sf.html> page in the Jail
- Filesystems section.
-
-
-
-
-
-
-
-
-
-
-
-
diff --git a/Documentation/virt/uml/user_mode_linux_howto_v2.rst b/Documentation/virt/uml/user_mode_linux_howto_v2.rst
new file mode 100644
index 0000000..312e431
--- /dev/null
+++ b/Documentation/virt/uml/user_mode_linux_howto_v2.rst
@@ -0,0 +1,1209 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+#########
+UML HowTo
+#########
+
+.. contents:: :local:
+
+************
+Introduction
+************
+
+Welcome to User Mode Linux
+
+User Mode Linux is the first Open Source virtualization platform (first
+release date 1991) and second virtualization platform for an x86 PC.
+
+How is UML Different from a VM using Virtualization package X?
+==============================================================
+
+We have come to assume that virtualization also means some level of
+hardware emulation. In fact, it does not. As long as a virtualization
+package provides the OS with devices which the OS can recognize and
+has a driver for, the devices do not need to emulate real hardware.
+Most OSes today have built-in support for a number of "fake"
+devices used only under virtualization.
+User Mode Linux takes this concept to the ultimate extreme - there
+is not a single real device in sight. It is 100% artificial or if
+we use the correct term 100% paravirtual. All UML devices are abstract
+concepts which map onto something provided by the host - files, sockets,
+pipes, etc.
+
+The other major difference between UML and various virtualization
+packages is that there is a distinct difference between the way the UML
+kernel and the UML programs operate.
+The UML kernel is just a process running on Linux - same as any other
+program. It can be run by an unprivileged user and it does not require
+anything in terms of special CPU features.
+The UML userspace, however, is a bit different. The Linux kernel on the
+host machine assists UML in intercepting everything the program running
+on a UML instance is trying to do and making the UML kernel handle all
+of its requests.
+This is different from other virtualization packages which do not make any
+difference between the guest kernel and guest programs. This difference
+results in a number of advantages and disadvantages of UML over let's say
+QEMU which we will cover later in this document.
+
+
+Why Would I Want User Mode Linux?
+=================================
+
+
+* If User Mode Linux kernel crashes, your host kernel is still fine. It
+ is not accelerated in any way (vhost, kvm, etc) and it is not trying to
+ access any devices directly. It is, in fact, a process like any other.
+
+* You can run a usermode kernel as a non-root user (you may need to
+ arrange appropriate permissions for some devices).
+
+* You can run a very small VM with a minimal footprint for a specific
+ task (for example 32M or less).
+
+* You can get extremely high performance for anything which is a "kernel
+ specific task" such as forwarding, firewalling, etc while still being
+ isolated from the host kernel.
+
+* You can play with kernel concepts without breaking things.
+
+* You are not bound by "emulating" hardware, so you can try weird and
+ wonderful concepts which are very difficult to support when emulating
+ real hardware such as time travel and making your system clock
+ dependent on what UML does (very useful for things like tests).
+
+* It's fun.
+
+Why not to run UML
+==================
+
+* The syscall interception technique used by UML makes it inherently
+ slower for any userspace applications. While it can do kernel tasks
+ on par with most other virtualization packages, its userspace is
+ **slow**. The root cause is that UML has a very high cost of creating
+ new processes and threads (something most Unix/Linux applications
+ take for granted).
+
+* UML is strictly uniprocessor at present. If you want to run an
+ application which needs many CPUs to function, it is clearly the
+ wrong choice.
+
+***********************
+Building a UML instance
+***********************
+
+There is no UML installer in any distribution. While you can use off
+the shelf install media to install into a blank VM using a virtualization
+package, there is no UML equivalent. You have to use appropriate tools on
+your host to build a viable filesystem image.
+
+This is extremely easy on Debian - you can do it using debootstrap. It is
+also easy on OpenWRT - the build process can build UML images. All other
+distros - YMMV.
+
+Creating an image
+=================
+
+Create a sparse raw disk image::
+
+ # dd if=/dev/zero of=disk_image_name bs=1 count=1 seek=16G
+
+This will create a 16G disk image. The OS will initially allocate only one
+block and will allocate more as they are written by UML. As of kernel
+version 4.19 UML fully supports TRIM (as usually used by flash drives).
+Using TRIM inside the UML image by specifying discard as a mount option
+or by running ``tune2fs -o discard /dev/ubdXX`` will request UML to
+return any unused blocks to the OS.
+
+Create a filesystem on the disk image and mount it::
+
+ # mkfs.ext4 ./disk_image_name && mount ./disk_image_name /mnt
+
+This example uses ext4, any other filesystem such as ext3, btrfs, xfs,
+jfs, etc will work too.
+
+Create a minimal OS installation on the mounted filesystem::
+
+ # debootstrap buster /mnt http://deb.debian.org/debian
+
+debootstrap does not set up the root password, fstab, hostname or
+anything related to networking. It is up to the user to do that.
+
+Set the root password -t he easiest way to do that is to chroot into the
+mounted image::
+
+ # chroot /mnt
+ # passwd
+ # exit
+
+Edit key system files
+=====================
+
+UML block devices are called ubds. The fstab created by debootstrap
+will be empty and it needs an entry for the root file system::
+
+ /dev/ubd0 ext4 discard,errors=remount-ro 0 1
+
+The image hostname will be set to the same as the host on which you
+are creating it image. It is a good idea to change that to avoid
+"Oh, bummer, I rebooted the wrong machine".
+
+UML supports two classes of network devices - the older uml_net ones
+which are scheduled for obsoletion. These are called ethX. It also
+supports the newer vector IO devices which are significantly faster
+and have support for some standard virtual network encapsulations like
+Ethernet over GRE and Ethernet over L2TPv3. These are called vec0.
+
+Depending on which one is in use, ``/etc/network/interfaces`` will
+need entries like::
+
+ # legacy UML network devices
+ auto eth0
+ iface eth0 inet dhcp
+
+ # vector UML network devices
+ auto vec0
+ iface eth0 inet dhcp
+
+We now have a UML image which is nearly ready to run, all we need is a
+UML kernel and modules for it.
+
+Most distributions have a UML package. Even if you intend to use your own
+kernel, testing the image with a stock one is always a good start. These
+packages come with a set of modules which should be copied to the target
+filesystem. The location is distribution dependent. For Debian these
+reside under /usr/lib/uml/modules. Copy recursively the content of this
+directory to the mounted UML filesystem::
+
+ # cp -rax /usr/lib/uml/modules /mnt/lib/modules
+
+If you have compiled your own kernel, you need to use the usual "install
+modules to a location" procedure by running::
+
+ # make install MODULES_DIR=/mnt/lib/modules
+
+At this point the image is ready to be brought up.
+
+*************************
+Setting Up UML Networking
+*************************
+
+UML networking is designed to emulate an Ethernet connection. This
+connection may be either a point-to-point (similar to a connection
+between machines using a back-to-back cable) or a connection to a
+switch. UML supports a wide variety of means to build these
+connections to all of: local machine, remote machine(s), local and
+remote UML and other VM instances.
+
+
++-----------+--------+------------------------------------+------------+
+| Transport | Type | Capabilities | Throughput |
++===========+========+====================================+============+
+| tap | vector | checksum, tso | > 8Gbit |
++-----------+--------+------------------------------------+------------+
+| hybrid | vector | checksum, tso, multipacket rx | > 6GBit |
++-----------+--------+------------------------------------+------------+
+| raw | vector | checksum, tso, multipacket rx, tx" | > 6GBit |
++-----------+--------+------------------------------------+------------+
+| EoGRE | vector | multipacket rx, tx | > 3Gbit |
++-----------+--------+------------------------------------+------------+
+| Eol2tpv3 | vector | multipacket rx, tx | > 3Gbit |
++-----------+--------+------------------------------------+------------+
+| bess | vector | multipacket rx, tx | > 3Gbit |
++-----------+--------+------------------------------------+------------+
+| fd | vector | dependent on fd type | varies |
++-----------+--------+------------------------------------+------------+
+| tuntap | legacy | none | ~ 500Mbit |
++-----------+--------+------------------------------------+------------+
+| daemon | legacy | none | ~ 450Mbit |
++-----------+--------+------------------------------------+------------+
+| socket | legacy | none | ~ 450Mbit |
++-----------+--------+------------------------------------+------------+
+| pcap | legacy | rx only | ~ 450Mbit |
++-----------+--------+------------------------------------+------------+
+| ethertap | legacy | obsolete | ~ 500Mbit |
++-----------+--------+------------------------------------+------------+
+| vde | legacy | obsolete | ~ 500Mbit |
++-----------+--------+------------------------------------+------------+
+
+* All transports which have tso and checksum offloads can deliver speeds
+ approaching 10G on TCP streams.
+
+* All transports which have multi-packet rx and/or tx can deliver pps
+ rates of up to 1Mps or more.
+
+* All legacy transports are generally limited to ~600-700MBit and 0.05Mps
+
+* GRE and L2TPv3 allow connections to all of: local machine, remote
+ machines, remote network devices and remote UML instances.
+
+* Socket allows connections only between UML instances.
+
+* Daemon and bess require running a local switch. This switch may be
+ connected to the host as well.
+
+
+Network configuration privileges
+================================
+
+The majority of the supported networking modes need ``root`` privileges.
+For example, in the legacy tuntap networking mode, users were required
+to be part of the group associated with the tunnel device.
+
+For newer network drivers like the vector transports, ``root`` privilege
+is required to fire an ioctl to setup the tun interface and/or use
+raw sockets where needed.
+
+This can be achieved by granting the user a particular capability instead
+of running UML as root. In case of vector transport, a user can add the
+capability ``CAP_NET_ADMIN`` or ``CAP_NET_RAW``, to the uml binary.
+Thenceforth, UML can be run with normal user privilges, along with
+full networking.
+
+For example::
+
+ # sudo setcap cap_net_raw,cap_net_admin+ep linux
+
+Configuring vector transports
+===============================
+
+All vector transports support a similar syntax:
+
+If X is the interface number as in vec0, vec1, vec2, etc, the general
+syntax for options is::
+
+ vecX:transport="Transport Name",option=value,option=value,...,option=value
+
+Common options
+--------------
+
+These options are common for all transports:
+
+* ``depth=int`` - sets the queue depth for vector IO. This is the
+ amount of packets UML will attempt to read or write in a single
+ system call. The default number is 64 and is generally sufficient
+ for most applications that need throughput in the 2-4 Gbit range.
+ Higher speeds may require larger values.
+
+* ``mac=XX:XX:XX:XX:XX`` - sets the interface MAC address value.
+
+* ``gro=[0,1]`` - sets GRO on or off. Enables receive/transmit offloads.
+ The effect of this option depends on the host side support in the transport
+ which is being configured. In most cases it will enable TCP segmentation and
+ RX/TX checksumming offloads. The setting must be identical on the host side
+ and the UML side. The UML kernel will produce warnings if it is not.
+ For example, GRO is enabled by default on local machine interfaces
+ (e.g. veth pairs, bridge, etc), so it should be enabled in UML in the
+ corresponding UML transports (raw, tap, hybrid) in order for networking to
+ operate correctly.
+
+* ``mtu=int`` - sets the interface MTU
+
+* ``headroom=int`` - adjusts the default headroom (32 bytes) reserved
+ if a packet will need to be re-encapsulated into for instance VXLAN.
+
+* ``vec=0`` - disable multipacket io and fall back to packet at a
+ time mode
+
+Shared Options
+--------------
+
+* ``ifname=str`` Transports which bind to a local network interface
+ have a shared option - the name of the interface to bind to.
+
+* ``src, dst, src_port, dst_port`` - all transports which use sockets
+ which have the notion of source and destination and/or source port
+ and destination port use these to specify them.
+
+* ``v6=[0,1]`` to specify if a v6 connection is desired for all
+ transports which operate over IP. Additionally, for transports that
+ have some differences in the way they operate over v4 and v6 (for example
+ EoL2TPv3), sets the correct mode of operation. In the absense of this
+ option, the socket type is determined based on what do the src and dst
+ arguments resolve/parse to.
+
+tap transport
+-------------
+
+Example::
+
+ vecX:transport=tap,ifname=tap0,depth=128,gro=1
+
+This will connect vec0 to tap0 on the host. Tap0 must already exist (for example
+created using tunctl) and UP.
+
+tap0 can be configured as a point-to-point interface and given an ip
+address so that UML can talk to the host. Alternatively, it is possible
+to connect UML to a tap interface which is connected to a bridge.
+
+While tap relies on the vector infrastructure, it is not a true vector
+transport at this point, because Linux does not support multi-packet
+IO on tap file descriptors for normal userspace apps like UML. This
+is a privilege which is offered only to something which can hook up
+to it at kernel level via specialized interfaces like vhost-net. A
+vhost-net like helper for UML is planned at some point in the future.
+
+Privileges required: tap transport requires either:
+
+* tap interface to exist and be created persistent and owned by the
+ UML user using tunctl. Example ``tunctl -u uml-user -t tap0``
+
+* binary to have ``CAP_NET_ADMIN`` privilege
+
+hybrid transport
+----------------
+
+Example::
+
+ vecX:transport=hybrid,ifname=tap0,depth=128,gro=1
+
+This is an experimental/demo transport which couples tap for transmit
+and a raw socket for receive. The raw socket allows multi-packet
+receive resulting in significantly higher packet rates than normal tap
+
+Privileges required: hybrid requires ``CAP_NET_RAW`` capability by
+the UML user as well as the requirements for the tap transport.
+
+raw socket transport
+--------------------
+
+Example::
+
+ vecX:transport=raw,ifname=p-veth0,depth=128,gro=1
+
+
+This transport uses vector IO on raw sockets. While you can bind to any
+interface including a physical one, the most common use it to bind to
+the "peer" side of a veth pair with the other side configured on the
+host.
+
+Example host configuration for Debian:
+
+**/etc/network/interfaces**::
+
+ auto veth0
+ iface veth0 inet static
+ address 192.168.4.1
+ netmask 255.255.255.252
+ broadcast 192.168.4.3
+ pre-up ip link add veth0 type veth peer name p-veth0 && \
+ ifconfig p-veth0 up
+
+UML can now bind to p-veth0 like this::
+
+ vec0:transport=raw,ifname=p-veth0,depth=128,gro=1
+
+
+If the UML guest is configured with 192.168.4.2 and netmask 255.255.255.0
+it can talk to the host on 192.168.4.1
+
+The raw transport also provides some support for offloading some of the
+filtering to the host. The two options to control it are:
+
+* ``bpffile=str`` filename of raw bpf code to be loaded as a socket filter
+
+* ``bpfflash=int`` 0/1 allow loading of bpf from inside User Mode Linux.
+ This option allows the use of the ethtool load firmware command to
+ load bpf code.
+
+In either case the bpf code is loaded into the host kernel. While this is
+presently limited to legacy bpf syntax (not ebpf), it is still a security
+risk. It is not recommended to allow this unless the User Mode Linux
+instance is considered trusted.
+
+Privileges required: raw socket transport requires `CAP_NET_RAW`
+capability.
+
+GRE socket transport
+--------------------
+
+Example::
+
+ vecX:transport=gre,src=$src_host,dst=$dst_host
+
+
+This will configure an Ethernet over ``GRE`` (aka ``GRETAP`` or
+``GREIRB``) tunnel which will connect the UML instance to a ``GRE``
+endpoint at host dst_host. ``GRE`` supports the following additional
+options:
+
+* ``rx_key=int`` - GRE 32 bit integer key for rx packets, if set,
+ ``txkey`` must be set too
+
+* ``tx_key=int`` - GRE 32 bit integer key for tx packets, if set
+ ``rx_key`` must be set too
+
+* ``sequence=[0,1]`` - enable GRE sequence
+
+* ``pin_sequence=[0,1]`` - pretend that the sequence is always reset
+ on each packet (needed to interoperate with some really broken
+ implementations)
+
+* ``v6=[0,1]`` - force IPv4 or IPv6 sockets respectively
+
+* GRE checksum is not presently supported
+
+GRE has a number of caveats:
+
+* You can use only one GRE connection per ip address. There is no way to
+ multiplex connections as each GRE tunnel is terminated directly on
+ the UML instance.
+
+* The key is not really a security feature. While it was intended as such
+ it's "security" is laughable. It is, however, a useful feature to
+ ensure that the tunnel is not misconfigured.
+
+An example configuration for a Linux host with a local address of
+192.168.128.1 to connect to a UML instance at 192.168.129.1
+
+**/etc/network/interfaces**::
+
+ auto gt0
+ iface gt0 inet static
+ address 10.0.0.1
+ netmask 255.255.255.0
+ broadcast 10.0.0.255
+ mtu 1500
+ pre-up ip link add gt0 type gretap local 192.168.128.1 \
+ remote 192.168.129.1 || true
+ down ip link del gt0 || true
+
+Additionally, GRE has been tested versus a variety of network equipment.
+
+Privileges required: GRE requires ``CAP_NET_RAW``
+
+l2tpv3 socket transport
+-----------------------
+
+_Warning_. L2TPv3 has a "bug". It is the "bug" known as "has more
+options than GNU ls". While it has some advantages, there are usually
+easier (and less verbose) ways to connect a UML instance to something.
+For example, most devices which support L2TPv3 also support GRE.
+
+Example::
+
+ vec0:transport=l2tpv3,udp=1,src=$src_host,dst=$dst_host,srcport=$src_port,dstport=$dst_port,depth=128,rx_session=0xffffffff,tx_session=0xffff
+
+This will configure an Ethernet over L2TPv3 fixed tunnel which will
+connect the UML instance to a L2TPv3 endpoint at host $dst_host using
+the L2TPv3 UDP flavour and UDP destination port $dst_port.
+
+L2TPv3 always requires the following additional options:
+
+* ``rx_session=int`` - l2tpv3 32 bit integer session for rx packets
+
+* ``tx_session=int`` - l2tpv3 32 bit integer session for tx packets
+
+As the tunnel is fixed these are not negotiated and they are
+preconfigured on both ends.
+
+Additionally, L2TPv3 supports the following optional parameters
+
+* ``rx_cookie=int`` - l2tpv3 32 bit integer cookie for rx packets - same
+ functionality as GRE key, more to prevent misconfiguration than provide
+ actual security
+
+* ``tx_cookie=int`` - l2tpv3 32 bit integer cookie for tx packets
+
+* ``cookie64=[0,1]`` - use 64 bit cookies instead of 32 bit.
+
+* ``counter=[0,1]`` - enable l2tpv3 counter
+
+* ``pin_counter=[0,1]`` - pretend that the counter is always reset on
+ each packet (needed to interoperate with some really broken
+ implementations)
+
+* ``v6=[0,1]`` - force v6 sockets
+
+* ``udp=[0,1]`` - use raw sockets (0) or UDP (1) version of the protocol
+
+L2TPv3 has a number of caveats:
+
+* you can use only one connection per ip address in raw mode. There is
+ no way to multiplex connections as each L2TPv3 tunnel is terminated
+ directly on the UML instance. UDP mode can use different ports for
+ this purpose.
+
+Here is an example of how to configure a linux host to connect to UML
+via L2TPv3:
+
+**/etc/network/interfaces**::
+
+ auto l2tp1
+ iface l2tp1 inet static
+ address 192.168.126.1
+ netmask 255.255.255.0
+ broadcast 192.168.126.255
+ mtu 1500
+ pre-up ip l2tp add tunnel remote 127.0.0.1 \
+ local 127.0.0.1 encap udp tunnel_id 2 \
+ peer_tunnel_id 2 udp_sport 1706 udp_dport 1707 && \
+ ip l2tp add session name l2tp1 tunnel_id 2 \
+ session_id 0xffffffff peer_session_id 0xffffffff
+ down ip l2tp del session tunnel_id 2 session_id 0xffffffff && \
+ ip l2tp del tunnel tunnel_id 2
+
+
+Privileges required: L2TPv3 requires ``CAP_NET_RAW`` for raw IP mode and
+no special privileges for the UDP mode.
+
+BESS socket transport
+---------------------
+
+BESS is a high performance modular network switch.
+
+https://github.com/NetSys/bess
+
+It has support for a simple sequential packet socket mode which in the
+more recent versions is using vector IO for high performance.
+
+Example::
+
+ vecX:transport=bess,src=$unix_src,dst=$unix_dst
+
+This will configure a BESS transport using the unix_src Unix domain
+socket address as source and unix_dst socket address as destination.
+
+For BESS configuration and how to allocate a BESS Unix domain socket port
+please see the BESS documentation.
+
+https://github.com/NetSys/bess/wiki/Built-In-Modules-and-Ports
+
+BESS transport does not require any special privileges.
+
+Configuring Legacy transports
+=============================
+
+Legacy transports are now considered obsolete. Please use the vector
+versions.
+
+***********
+Running UML
+***********
+
+This section assumes that either the user-mode-linux package from the
+distribution or a custom built kernel has been installed on the host.
+
+These add an executable called linux to the system. This is the UML
+kernel. It can be run just like any other executable.
+It will take most normal linux kernel arguments as command line
+arguments. Additionally, it will need some UML specific arguments
+in order to do something useful.
+
+Arguments
+=========
+
+Mandatory Arguments:
+--------------------
+
+* ``mem=int[K,M,G]`` - amount of memory. By default bytes. It will
+ also accept K, M or G qualifiers.
+
+* ``ubdX[s,d,c,t]=`` virtual disk specification. This is not really
+ mandatory, but it is likely to be needed in nearly all cases so we can
+ specify a root file system.
+ The simplest possible image specification is the name of the image
+ file for the filesystem (created using one of the methods described
+ in `Creating an image`_)
+
+ * UBD devices support copy on write (COW). The changes are kept in
+ a separate file which can be discarded allowing a rollback to the
+ original pristine image. If COW is desired, the UBD image is
+ specified as: ``cow_file,master_image``.
+ Example:``ubd0=Filesystem.cow,Filesystem.img``
+
+ * UBD devices can be set to use synchronous IO. Any writes are
+ immediately flushed to disk. This is done by adding ``s`` after
+ the ``ubdX`` specification
+
+ * UBD performs some euristics on devices specified as a single
+ filename to make sure that a COW file has not been specified as
+ the image. To turn them off, use the ``d`` flag after ``ubdX``
+
+ * UBD supports TRIM - asking the Host OS to reclaim any unused
+ blocks in the image. To turn it off, specify the ``t`` flag after
+ ``ubdX``
+
+* ``root=`` root device - most likely ``/dev/ubd0`` (this is a Linux
+ filesystem image)
+
+Important Optional Arguments
+----------------------------
+
+If UML is run as "linux" with no extra arguments, it will try to start an
+xterm for every console configured inside the image (up to 6 in most
+linux distributions). Each console is started inside an
+xterm. This makes it nice and easy to use UML on a host with a GUI. It is,
+however, the wrong approach if UML is to be used as a testing harness or run
+in a text-only environment.
+
+In order to change this behaviour we need to specify an alternative console
+and wire it to one of the supported "line" channels. For this we need to map a
+console to use something different from the default xterm.
+
+Example which will divert console number 1 to stdin/stdout::
+
+ con1=fd:0,fd:1
+
+UML supports a wide variety of serial line channels which are specified using
+the following syntax
+
+ conX=channel_type:options[,channel_type:options]
+
+
+If the channel specification contains two parts separated by comma, the first
+one is input, the second one output.
+
+* The null channel - Discard all input or output. Example ``con=null`` will set
+ all consoles to null by default.
+
+* The fd channel - use file descriptor numbers for input/out. Example:
+ ``con1=fd:0,fd:1.``
+
+* The port channel - listen on tcp port number. Example: ``con1=port:4321``
+
+* The pty and pts channels - use system pty/pts.
+
+* The tty channel - bind to an existing system tty. Example: ``con1=/dev/tty8``
+ will make UML use the host 8th console (usually unused).
+
+* The xterm channel - this is the default - bring up an xterm on this channel
+ and direct IO to it. Note, that in order for xterm to work, the host must
+ have the UML distribution package installed. This usually contains the
+ port-helper and other utilities needed for UML to communicate with the xterm.
+ Alternatively, these need to be complied and installed from source. All
+ options applicable to consoles also apply to UML serial lines which are
+ presented as ttyS inside UML.
+
+Starting UML
+============
+
+We can now run UML.
+::
+
+ # linux mem=2048M umid=TEST \
+ ubd0=Filesystem.img \
+ vec0:transport=tap,ifname=tap0,depth=128,gro=1 \
+ root=/dev/ubda con=null con0=null,fd:2 con1=fd:0,fd:1
+
+This will run an instance with ``2048M RAM``, try to use the image file
+called ``Filesystem.img`` as root. It will connect to the host using tap0.
+All consoles except ``con1`` will be disabled and console 1 will
+use standard input/output making it appear in the same terminal it was started.
+
+Logging in
+============
+
+If you have not set up a password when generating the image, you will have to
+shut down the UML instance, mount the image, chroot into it and set it - as
+described in the Generating an Image section. If the password is already set,
+you can just log in.
+
+The UML Management Console
+============================
+
+In addition to managing the image from "the inside" using normal sysadmin tools,
+it is possible to perform a number of low level operations using the UML
+management console. The UML management console is a low-level interface to the
+kernel on a running UML instance, somewhat like the i386 SysRq interface. Since
+there is a full-blown operating system under UML, there is much greater
+flexibility possible than with the SysRq mechanism.
+
+There are a number of things you can do with the mconsole interface:
+
+* get the kernel version
+* add and remove devices
+* halt or reboot the machine
+* Send SysRq commands
+* Pause and resume the UML
+* Inspect processes running inside UML
+* Inspect UML internal /proc state
+
+You need the mconsole client (uml\_mconsole) which is a part of the UML
+tools package available in most Linux distritions.
+
+You also need ``CONFIG_MCONSOLE`` (under 'General Setup') enabled in the UML
+kernel. When you boot UML, you'll see a line like::
+
+ mconsole initialized on /home/jdike/.uml/umlNJ32yL/mconsole
+
+If you specify a unique machine id one the UML command line, i.e.
+``umid=debian``, you'll see this::
+
+ mconsole initialized on /home/jdike/.uml/debian/mconsole
+
+
+That file is the socket that uml_mconsole will use to communicate with
+UML. Run it with either the umid or the full path as its argument::
+
+ # uml_mconsole debian
+
+or
+
+ # uml_mconsole /home/jdike/.uml/debian/mconsole
+
+
+You'll get a prompt, at which you can run one of these commands:
+
+* version
+* help
+* halt
+* reboot
+* config
+* remove
+* sysrq
+* help
+* cad
+* stop
+* go
+* proc
+* stack
+
+version
+-------
+
+This command takes no arguments. It prints the UML version::
+
+ (mconsole) version
+ OK Linux OpenWrt 4.14.106 #0 Tue Mar 19 08:19:41 2019 x86_64
+
+
+There are a couple actual uses for this. It's a simple no-op which
+can be used to check that a UML is running. It's also a way of
+sending a device interrupt to the UML. UML mconsole is treated internally as
+a UML device.
+
+help
+----
+
+This command takes no arguments. It prints a short help screen with the
+supported mconsole commands.
+
+
+halt and reboot
+---------------
+
+These commands take no arguments. They shut the machine down immediately, with
+no syncing of disks and no clean shutdown of userspace. So, they are
+pretty close to crashing the machine::
+
+ (mconsole) halt
+ OK
+
+config
+------
+
+"config" adds a new device to the virtual machine. This is supported
+by most UML device drivers. It takes one argument, which is the
+device to add, with the same syntax as the kernel command line::
+
+ (mconsole) config ubd3=/home/jdike/incoming/roots/root_fs_debian22
+
+remove
+------
+
+"remove" deletes a device from the system. Its argument is just the
+name of the device to be removed. The device must be idle in whatever
+sense the driver considers necessary. In the case of the ubd driver,
+the removed block device must not be mounted, swapped on, or otherwise
+open, and in the case of the network driver, the device must be down::
+
+ (mconsole) remove ubd3
+
+sysrq
+-----
+
+This command takes one argument, which is a single letter. It calls the
+generic kernel's SysRq driver, which does whatever is called for by
+that argument. See the SysRq documentation in
+Documentation/admin-guide/sysrq.rst in your favorite kernel tree to
+see what letters are valid and what they do.
+
+cad
+---
+
+This invokes the ``Ctl-Alt-Del`` action in the running image. What exactly
+this ends up doing is up to init, systemd, etc. Normally, it reboots the
+machine.
+
+stop
+----
+
+This puts the UML in a loop reading mconsole requests until a 'go'
+mconsole command is received. This is very useful as a
+debugging/snapshotting tool.
+
+go
+--
+
+This resumes a UML after being paused by a 'stop' command. Note that
+when the UML has resumed, TCP connections may have timed out and if
+the UML is paused for a long period of time, crond might go a little
+crazy, running all the jobs it didn't do earlier.
+
+proc
+----
+
+This takes one argument - the name of a file in /proc which is printed
+to the mconsole standard output
+
+stack
+-----
+
+This takes one argument - the pid number of a process. Its stack is
+printed to a standard output.
+
+*******************
+Advanced UML Topics
+*******************
+
+Sharing Filesystems between Virtual Machines
+============================================
+
+Don't attempt to share filesystems simply by booting two UMLs from the
+same file. That's the same thing as booting two physical machines
+from a shared disk. It will result in filesystem corruption.
+
+Using layered block devices
+---------------------------
+
+The way to share a filesystem between two virtual machines is to use
+the copy-on-write (COW) layering capability of the ubd block driver.
+Any changed blocks are stored in the private COW file, while reads come
+from either device - the private one if the requested block is valid in
+it, the shared one if not. Using this scheme, the majority of data
+which is unchanged is shared between an arbitrary number of virtual
+machines, each of which has a much smaller file containing the changes
+that it has made. With a large number of UMLs booting from a large root
+filesystem, this leads to a huge disk space saving.
+
+Sharing file system data will also help performance, since the host will
+be able to cache the shared data using a much smaller amount of memory,
+so UML disk requests will be served from the host's memory rather than
+its disks. There is a major caveat in doing this on multisocket NUMA
+machines. On such hardware, running many UML instances with a shared
+master image and COW changes may caise issues like NMIs from excess of
+inter-socket traffic.
+
+If you are running UML on high end hardware like this, make sure to
+bind UML to a set of logical cpus residing on the same socket using the
+``taskset`` command or have a look at the "tuning" section.
+
+To add a copy-on-write layer to an existing block device file, simply
+add the name of the COW file to the appropriate ubd switch::
+
+ ubd0=root_fs_cow,root_fs_debian_22
+
+where ``root_fs_cow`` is the private COW file and ``root_fs_debian_22`` is
+the existing shared filesystem. The COW file need not exist. If it
+doesn't, the driver will create and initialize it.
+
+Disk Usage
+----------
+
+UML has TRIM support which will release any unused space in its disk
+image files to the underlying OS. It is important to use either ls -ls
+or du to verify the actual file size.
+
+COW validity.
+-------------
+
+Any changes to the master image will invalidate all COW files. If this
+happens, UML will *NOT* automatically delete any of the COW files and
+will refuse to boot. In this case the only solution is to either
+restore the old image (including its last modified timestamp) or remove
+all COW files which will result in their recreation. Any changes in
+the COW files will be lost.
+
+Cows can moo - uml_moo : Merging a COW file with its backing file
+-----------------------------------------------------------------
+
+Depending on how you use UML and COW devices, it may be advisable to
+merge the changes in the COW file into the backing file every once in
+a while.
+
+The utility that does this is uml_moo. Its usage is::
+
+ uml_moo COW_file new_backing_file
+
+
+There's no need to specify the backing file since that information is
+already in the COW file header. If you're paranoid, boot the new
+merged file, and if you're happy with it, move it over the old backing
+file.
+
+``uml_moo`` creates a new backing file by default as a safety measure.
+It also has a destructive merge option which will merge the COW file
+directly into its current backing file. This is really only usable
+when the backing file only has one COW file associated with it. If
+there are multiple COWs associated with a backing file, a -d merge of
+one of them will invalidate all of the others. However, it is
+convenient if you're short of disk space, and it should also be
+noticeably faster than a non-destructive merge.
+
+``uml_moo`` is installed with the UML distribution packages and is
+available as a part of UML utilities.
+
+Host file access
+==================
+
+If you want to access files on the host machine from inside UML, you
+can treat it as a separate machine and either nfs mount directories
+from the host or copy files into the virtual machine with scp.
+However, since UML is running on the host, it can access those
+files just like any other process and make them available inside the
+virtual machine without the need to use the network.
+This is possible with the hostfs virtual filesystem. With it, you
+can mount a host directory into the UML filesystem and access the
+files contained in it just as you would on the host.
+
+*SECURITY WARNING*
+
+Hostfs without any parameters to the UML Image will allow the image
+to mount any part of the host filesystem and write to it. Always
+confine hostfs to a specific "harmless" directory (for example ``/var/tmp``)
+if running UML. This is especially important if UML is being run as root.
+
+Using hostfs
+------------
+
+To begin with, make sure that hostfs is available inside the virtual
+machine with::
+
+ # cat /proc/filesystems
+
+``hostfs`` should be listed. If it's not, either rebuild the kernel
+with hostfs configured into it or make sure that hostfs is built as a
+module and available inside the virtual machine, and insmod it.
+
+
+Now all you need to do is run mount::
+
+ # mount none /mnt/host -t hostfs
+
+will mount the host's ``/`` on the virtual machine's ``/mnt/host``.
+If you don't want to mount the host root directory, then you can
+specify a subdirectory to mount with the -o switch to mount::
+
+ # mount none /mnt/home -t hostfs -o /home
+
+will mount the hosts's /home on the virtual machine's /mnt/home.
+
+hostfs as the root filesystem
+-----------------------------
+
+It's possible to boot from a directory hierarchy on the host using
+hostfs rather than using the standard filesystem in a file.
+To start, you need that hierarchy. The easiest way is to loop mount
+an existing root_fs file::
+
+ # mount root_fs uml_root_dir -o loop
+
+
+You need to change the filesystem type of ``/`` in ``etc/fstab`` to be
+'hostfs', so that line looks like this::
+
+ /dev/ubd/0 / hostfs defaults 1 1
+
+Then you need to chown to yourself all the files in that directory
+that are owned by root. This worked for me::
+
+ # find . -uid 0 -exec chown jdike {} \;
+
+Next, make sure that your UML kernel has hostfs compiled in, not as a
+module. Then run UML with the boot device pointing at that directory::
+
+ ubd0=/path/to/uml/root/directory
+
+UML should then boot as it does normally.
+
+Hostfs Caveats
+--------------
+
+Hostfs does not support keeping track of host filesystem changes on the
+host (outside UML). As a result, if a file is changed without UML's
+knowledge, UML will not know about it and its own in-memory cache of
+the file may be corrupt. While it is possible to fix this, it is not
+something which is being worked on at present.
+
+Tuning UML
+============
+
+UML at present is strictly uniprocessor. It will, however spin up a
+number of threads to handle various functions.
+
+The UBD driver, SIGIO and the MMU emulation do that. If the system is
+idle, these threads will be migrated to other processors on a SMP host.
+This, unfortunately, will usually result in LOWER performance because of
+all of the cache/memory synchronization traffic between cores. As a
+result, UML will usually benefit from being pinned on a single CPU
+especially on a large system. This can result in performance differences
+of 5 times or higher on some benchmarks.
+
+Similarly, on large multi-node NUMA systems UML will benefit if all of
+its memory is allocated from the same NUMA node it will run on. The
+OS will *NOT* do that by default. In order to do that, the sysadmin
+needs to create a suitable tmpfs ramdisk bound to a particular node
+and use that as the source for UML RAM allocation by specifying it
+in the TMP or TEMP environment variables. UML will look at the values
+of ``TMPDIR``, ``TMP`` or ``TEMP`` for that. If that fails, it will
+look for shmfs mounted under ``/dev/shm``. If everything else fails use
+``/tmp/`` regardless of the filesystem type used for it::
+
+ mount -t tmpfs -ompol=bind:X none /mnt/tmpfs-nodeX
+ TEMP=/mnt/tmpfs-nodeX taskset -cX linux options options options..
+
+*******************************************
+Contributing to UML and Developing with UML
+*******************************************
+
+UML is an excellent platform to develop new Linux kernel concepts -
+filesystems, devices, virtualization, etc. It provides unrivalled
+opportunities to create and test them without being constrained to
+emulating specific hardware.
+
+Example - want to try how linux will work with 4096 "proper" network
+devices?
+
+Not an issue with UML. At the same time, this is something which
+is difficult with other virtualization packages - they are
+constrained by the number of devices allowed on the hardware bus
+they are trying to emulate (for example 16 on a PCI bus in qemu).
+
+If you have something to contribute such as a patch, a bugfix, a
+new feature, please send it to ``linux-um@lists.infradead.org``
+
+Please follow all standard Linux patch guidelines such as cc-ing
+relevant maintainers and run ``./sripts/checkpatch.pl`` on your patch.
+For more details see ``Documentation/process/submitting-patches.rst``
+
+Note - the list does not accept HTML or attachments, all emails must
+be formatted as plain text.
+
+Developing always goes hand in hand with debugging. First of all,
+you can always run UML under gdb and there will be a whole section
+later on on how to do that. That, however, is not the only way to
+debug a linux kernel. Quite often adding tracing statements and/or
+using UML specific approaches such as ptracing the UML kernel process
+are significantly more informative.
+
+Tracing UML
+=============
+
+When running UML consists of a main kernel thread and a number of
+helper threads. The ones of interest for tracing are NOT the ones
+that are already ptraced by UML as a part of its MMU emulation.
+
+These are usually the first three threads visible in a ps display.
+The one with the lowest PID number and using most CPU is usually the
+kernel thread. The other threads are the disk
+(ubd) device helper thread and the sigio helper thread.
+Running ptrace on this thread usually results in the following picture::
+
+ host$ strace -p 16566
+ --- SIGIO {si_signo=SIGIO, si_code=POLL_IN, si_band=65} ---
+ epoll_wait(4, [{EPOLLIN, {u32=3721159424, u64=3721159424}}], 64, 0) = 1
+ epoll_wait(4, [], 64, 0) = 0
+ rt_sigreturn({mask=[PIPE]}) = 16967
+ ptrace(PTRACE_GETREGS, 16967, NULL, 0xd5f34f38) = 0
+ ptrace(PTRACE_GETREGSET, 16967, NT_X86_XSTATE, [{iov_base=0xd5f35010, iov_len=832}]) = 0
+ ptrace(PTRACE_GETSIGINFO, 16967, NULL, {si_signo=SIGTRAP, si_code=0x85, si_pid=16967, si_uid=0}) = 0
+ ptrace(PTRACE_SETREGS, 16967, NULL, 0xd5f34f38) = 0
+ ptrace(PTRACE_SETREGSET, 16967, NT_X86_XSTATE, [{iov_base=0xd5f35010, iov_len=2696}]) = 0
+ ptrace(PTRACE_SYSEMU, 16967, NULL, 0) = 0
+ --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_TRAPPED, si_pid=16967, si_uid=0, si_status=SIGTRAP, si_utime=65, si_stime=89} ---
+ wait4(16967, [{WIFSTOPPED(s) && WSTOPSIG(s) == SIGTRAP | 0x80}], WSTOPPED|__WALL, NULL) = 16967
+ ptrace(PTRACE_GETREGS, 16967, NULL, 0xd5f34f38) = 0
+ ptrace(PTRACE_GETREGSET, 16967, NT_X86_XSTATE, [{iov_base=0xd5f35010, iov_len=832}]) = 0
+ ptrace(PTRACE_GETSIGINFO, 16967, NULL, {si_signo=SIGTRAP, si_code=0x85, si_pid=16967, si_uid=0}) = 0
+ timer_settime(0, 0, {it_interval={tv_sec=0, tv_nsec=0}, it_value={tv_sec=0, tv_nsec=2830912}}, NULL) = 0
+ getpid() = 16566
+ clock_nanosleep(CLOCK_MONOTONIC, 0, {tv_sec=1, tv_nsec=0}, NULL) = ? ERESTART_RESTARTBLOCK (Interrupted by signal)
+ --- SIGALRM {si_signo=SIGALRM, si_code=SI_TIMER, si_timerid=0, si_overrun=0, si_value={int=1631716592, ptr=0x614204f0}} ---
+ rt_sigreturn({mask=[PIPE]}) = -1 EINTR (Interrupted system call)
+
+This is a typical picture from a mostly idle UML instance
+
+* UML interrupt controller uses epoll - this is UML waiting for IO
+ interrupts:
+
+ epoll_wait(4, [{EPOLLIN, {u32=3721159424, u64=3721159424}}], 64, 0) = 1
+
+* The sequence of ptrace calls is part of MMU emulation and runnin the
+ UML userspace
+* ``timer_settime`` is part of the UML high res timer subsystem mapping
+ timer requests from inside UML onto the host high resultion timers.
+* ``clock_nanosleep`` is UML going into idle (similar to the way a PC
+ will execute an ACPI idle).
+
+As you can see UML will generate quite a bit of output even in idle.The output
+can be very informative when observing IO. It shows the actual IO calls, their
+arguments and returns values.
+
+Kernel debugging
+================
+
+You can run UML under gdb now, though it will not necessarily agree to
+be started under it. If you are trying to track a runtime bug, it is
+much better to attach gdb to a running UML instance and let UML run.
+
+Assuming the same PID number as in the previous example, this would be::
+
+ # gdb -p 16566
+
+This will STOP the UML instance, so you must enter `cont` at the GDB
+command line to request it to continue. It may be a good idea to make
+this into a gdb script and pass it to gdb as an argument.
+
+Developing Device Drivers
+=========================
+
+Nearly all UML drivers are monolithic. While it is possible to build a
+UML driver as a kernel module, that limits the possible functionality
+to in-kernel only and non-UML specific. The reason for this is that
+in order to really leverage UML, one needs to write a piece of
+userspace code which maps driver concepts onto actual userspace host
+calls.
+
+This forms the so called "user" portion of the driver. While it can
+reuse a lot of kernel concepts, it is generally just another piece of
+userspace code. This portion needs some matching "kernel" code which
+resides inside the UML image and which implements the Linux kernel part.
+
+*Note: There are very few limitations in the way "kernel" and "user" interact*.
+
+UML does not have a strictly defined kernel to host API. It does not
+try to emulate a specific architecture or bus. UML's "kernel" and
+"user" can share memory, code and interact as needed to implement
+whatever design the software developer has in mind. The only
+limitations are purely technical. Due to a lot of functions and
+variables having the same names, the developer should be careful
+which includes and libraries they are trying to refer to.
+
+As a result a lot of userspace code consists of simple wrappers.
+F.e. ``os_close_file()`` is just a wrapper around ``close()``
+which ensures that the userspace function close does not clash
+with similarly named function(s) in the kernel part.
+
+Security Considerations
+-----------------------
+
+Drivers or any new functionality should default to not
+accepting arbitrary filename, bpf code or other parameters
+which can affect the host from inside the UML instance.
+For example, specifying the socket used for IPC communication
+between a driver and the host at the UML command line is OK
+security-wise. Allowing it as a loadable module parameter
+isn't.
+
+If such functionality is desireable for a particular application
+(e.g. loading BPF "firmware" for raw socket network transports),
+it should be off by default and should be explicitly turned on
+as a command line parameter at startup.
+
+Even with this in mind, the level of isolation between UML
+and the host is relatively weak. If the UML userspace is
+allowed to load arbitrary kernel drivers, an attacker can
+use this to break out of UML. Thus, if UML is used in
+a production application, it is recommended that all modules
+are loaded at boot and kernel module loading is disabled
+afterwards.