v4.19.13 snapshot.
diff --git a/drivers/xen/time.c b/drivers/xen/time.c
new file mode 100644
index 0000000..3e741cd
--- /dev/null
+++ b/drivers/xen/time.c
@@ -0,0 +1,183 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Xen stolen ticks accounting.
+ */
+#include <linux/kernel.h>
+#include <linux/kernel_stat.h>
+#include <linux/math64.h>
+#include <linux/gfp.h>
+#include <linux/slab.h>
+
+#include <asm/paravirt.h>
+#include <asm/xen/hypervisor.h>
+#include <asm/xen/hypercall.h>
+
+#include <xen/events.h>
+#include <xen/features.h>
+#include <xen/interface/xen.h>
+#include <xen/interface/vcpu.h>
+#include <xen/xen-ops.h>
+
+/* runstate info updated by Xen */
+static DEFINE_PER_CPU(struct vcpu_runstate_info, xen_runstate);
+
+static DEFINE_PER_CPU(u64[4], old_runstate_time);
+
+/* return an consistent snapshot of 64-bit time/counter value */
+static u64 get64(const u64 *p)
+{
+ u64 ret;
+
+ if (BITS_PER_LONG < 64) {
+ u32 *p32 = (u32 *)p;
+ u32 h, l, h2;
+
+ /*
+ * Read high then low, and then make sure high is
+ * still the same; this will only loop if low wraps
+ * and carries into high.
+ * XXX some clean way to make this endian-proof?
+ */
+ do {
+ h = READ_ONCE(p32[1]);
+ l = READ_ONCE(p32[0]);
+ h2 = READ_ONCE(p32[1]);
+ } while(h2 != h);
+
+ ret = (((u64)h) << 32) | l;
+ } else
+ ret = READ_ONCE(*p);
+
+ return ret;
+}
+
+static void xen_get_runstate_snapshot_cpu_delta(
+ struct vcpu_runstate_info *res, unsigned int cpu)
+{
+ u64 state_time;
+ struct vcpu_runstate_info *state;
+
+ BUG_ON(preemptible());
+
+ state = per_cpu_ptr(&xen_runstate, cpu);
+
+ do {
+ state_time = get64(&state->state_entry_time);
+ rmb(); /* Hypervisor might update data. */
+ *res = READ_ONCE(*state);
+ rmb(); /* Hypervisor might update data. */
+ } while (get64(&state->state_entry_time) != state_time ||
+ (state_time & XEN_RUNSTATE_UPDATE));
+}
+
+static void xen_get_runstate_snapshot_cpu(struct vcpu_runstate_info *res,
+ unsigned int cpu)
+{
+ int i;
+
+ xen_get_runstate_snapshot_cpu_delta(res, cpu);
+
+ for (i = 0; i < 4; i++)
+ res->time[i] += per_cpu(old_runstate_time, cpu)[i];
+}
+
+void xen_manage_runstate_time(int action)
+{
+ static struct vcpu_runstate_info *runstate_delta;
+ struct vcpu_runstate_info state;
+ int cpu, i;
+
+ switch (action) {
+ case -1: /* backup runstate time before suspend */
+ if (unlikely(runstate_delta))
+ pr_warn_once("%s: memory leak as runstate_delta is not NULL\n",
+ __func__);
+
+ runstate_delta = kmalloc_array(num_possible_cpus(),
+ sizeof(*runstate_delta),
+ GFP_ATOMIC);
+ if (unlikely(!runstate_delta)) {
+ pr_warn("%s: failed to allocate runstate_delta\n",
+ __func__);
+ return;
+ }
+
+ for_each_possible_cpu(cpu) {
+ xen_get_runstate_snapshot_cpu_delta(&state, cpu);
+ memcpy(runstate_delta[cpu].time, state.time,
+ sizeof(runstate_delta[cpu].time));
+ }
+
+ break;
+
+ case 0: /* backup runstate time after resume */
+ if (unlikely(!runstate_delta)) {
+ pr_warn("%s: cannot accumulate runstate time as runstate_delta is NULL\n",
+ __func__);
+ return;
+ }
+
+ for_each_possible_cpu(cpu) {
+ for (i = 0; i < 4; i++)
+ per_cpu(old_runstate_time, cpu)[i] +=
+ runstate_delta[cpu].time[i];
+ }
+
+ break;
+
+ default: /* do not accumulate runstate time for checkpointing */
+ break;
+ }
+
+ if (action != -1 && runstate_delta) {
+ kfree(runstate_delta);
+ runstate_delta = NULL;
+ }
+}
+
+/*
+ * Runstate accounting
+ */
+void xen_get_runstate_snapshot(struct vcpu_runstate_info *res)
+{
+ xen_get_runstate_snapshot_cpu(res, smp_processor_id());
+}
+
+/* return true when a vcpu could run but has no real cpu to run on */
+bool xen_vcpu_stolen(int vcpu)
+{
+ return per_cpu(xen_runstate, vcpu).state == RUNSTATE_runnable;
+}
+
+u64 xen_steal_clock(int cpu)
+{
+ struct vcpu_runstate_info state;
+
+ xen_get_runstate_snapshot_cpu(&state, cpu);
+ return state.time[RUNSTATE_runnable] + state.time[RUNSTATE_offline];
+}
+
+void xen_setup_runstate_info(int cpu)
+{
+ struct vcpu_register_runstate_memory_area area;
+
+ area.addr.v = &per_cpu(xen_runstate, cpu);
+
+ if (HYPERVISOR_vcpu_op(VCPUOP_register_runstate_memory_area,
+ xen_vcpu_nr(cpu), &area))
+ BUG();
+}
+
+void __init xen_time_setup_guest(void)
+{
+ bool xen_runstate_remote;
+
+ xen_runstate_remote = !HYPERVISOR_vm_assist(VMASST_CMD_enable,
+ VMASST_TYPE_runstate_update_flag);
+
+ pv_time_ops.steal_clock = xen_steal_clock;
+
+ static_key_slow_inc(¶virt_steal_enabled);
+ if (xen_runstate_remote)
+ static_key_slow_inc(¶virt_steal_rq_enabled);
+}