Get rid of 'fast path' for HVC calls.
It is unlikely to be much faster in practice, and complicates the code.
Bug: 141469322
Change-Id: I3d12edf6096fff5a1a14b4fc5336084b90ff90ac
diff --git a/src/arch/aarch64/hypervisor/exceptions.S b/src/arch/aarch64/hypervisor/exceptions.S
index 1e30fe1..4a89f47 100644
--- a/src/arch/aarch64/hypervisor/exceptions.S
+++ b/src/arch/aarch64/hypervisor/exceptions.S
@@ -18,19 +18,15 @@
#include "exception_macros.S"
/**
- * Saves the volatile registers into the register buffer of the current vcpu. It
- * allocates space on the stack for x18 and saves it if "also_save_x18" is
- * specified; otherwise the caller is expected to have saved x18 in a similar
- * fashion.
+ * Saves the volatile registers into the register buffer of the current vcpu.
*/
-.macro save_volatile_to_vcpu also_save_x18
-.ifnb \also_save_x18
+.macro save_volatile_to_vcpu
/*
* Save x18 since we're about to clobber it. We subtract 16 instead of
* 8 from the stack pointer to keep it 16-byte aligned.
*/
str x18, [sp, #-16]!
-.endif
+
/* Get the current vcpu. */
mrs x18, tpidr_el2
stp x0, x1, [x18, #VCPU_REGS + 8 * 0]
@@ -63,7 +59,7 @@
* registers from the new vcpu.
*/
.macro lower_exception handler:req
- save_volatile_to_vcpu also_save_x18
+ save_volatile_to_vcpu
/* Call C handler. */
bl \handler
@@ -77,67 +73,29 @@
.endm
/**
- * This is the handler for a sync exception taken at a lower EL. If the reason
- * for the exception is an HVC call, it calls the faster hvc_handler without
- * saving a lot of the registers, otherwise it goes to slow_sync_lower, which is
- * the slow path where all registers needs to be saved/restored.
+ * This is the handler for a sync exception taken at a lower EL.
*/
.macro lower_sync_exception
- /* Save x18 as save_volatile_to_vcpu would have. */
- str x18, [sp, #-16]!
+ save_volatile_to_vcpu
/* Extract the exception class (EC) from exception syndrome register. */
mrs x18, esr_el2
lsr x18, x18, #26
- /* Take the slow path if exception is not due to an HVC instruction. */
- sub x18, x18, #0x16
- cbnz x18, slow_sync_lower
+ /* Take the system register path for EC 0x18. */
+ sub x18, x18, #0x18
+ cbz x18, system_register_access
- /*
- * Save x4-x17, x29 and x30, which are not saved by the callee, then jump to
- * HVC handler.
- */
- stp x4, x5, [sp, #-16]!
- stp x6, x7, [sp, #-16]!
- stp x8, x9, [sp, #-16]!
- stp x10, x11, [sp, #-16]!
- stp x12, x13, [sp, #-16]!
- stp x14, x15, [sp, #-16]!
- stp x16, x17, [sp, #-16]!
- stp x29, x30, [sp, #-16]!
+ /* Read syndrome register and call C handler. */
+ mrs x0, esr_el2
+ bl sync_lower_exception
- /*
- * Make room for hvc_handler_return on stack, and point x8 (the indirect
- * result location register in the AAPCS64 standard) to it.
- * hvc_handler_return is returned this way according to paragraph
- * 5.4.2.B.3 and section 5.5 because it is larger than 16 bytes.
- */
- stp xzr, xzr, [sp, #-16]!
- stp xzr, xzr, [sp, #-16]!
- stp xzr, xzr, [sp, #-16]!
- mov x8, sp
+ /* Switch vcpu if requested by handler. */
+ cbnz x0, vcpu_switch
- bl hvc_handler
-
- /* Get the hvc_handler_return back off the stack. */
- ldp x0, x1, [sp], #16
- ldp x2, x3, [sp], #16
- ldr x18, [sp], #16
-
- ldp x29, x30, [sp], #16
- ldp x16, x17, [sp], #16
- ldp x14, x15, [sp], #16
- ldp x12, x13, [sp], #16
- ldp x10, x11, [sp], #16
- ldp x8, x9, [sp], #16
- ldp x6, x7, [sp], #16
- ldp x4, x5, [sp], #16
-
- cbnz x18, sync_lower_switch
- /* Restore x18, which was saved on the stack. */
- ldr x18, [sp], #16
- eret
+ /* vcpu is not changing. */
+ mrs x0, tpidr_el2
+ b vcpu_restore_volatile_and_run
.endm
/**
@@ -212,26 +170,6 @@
lower_exception serr_lower
.balign 0x40
-slow_sync_lower:
- /* The caller must have saved x18, so we don't save it here. */
- save_volatile_to_vcpu
-
- /* Extract the exception class (EC) from exception syndrome register. */
- mrs x18, esr_el2
- lsr x18, x18, #26
-
- /* Take the system register path for EC 0x18. */
- sub x18, x18, #0x18
- cbz x18, system_register_access
-
- /* Read syndrome register and call C handler. */
- mrs x0, esr_el2
- bl sync_lower_exception
- cbnz x0, vcpu_switch
-
- /* vcpu is not changing. */
- mrs x0, tpidr_el2
- b vcpu_restore_volatile_and_run
/**
* Handle accesses to system registers (EC=0x18) and return to original caller.