===================================================================
@@ -36,6 +36,13 @@
uint64_t clock;
bool clock_valid;
+
+ /* whether machine type supports reliable get clock */
+ bool mach_use_reliable_get_clock;
+
+ /* whether the 'clock' value was obtained in a host with
+ * reliable KVM_GET_CLOCK */
+ bool clock_is_reliable;
} KVMClockState;
struct pvclock_vcpu_time_info {
@@ -81,6 +88,19 @@
return nsec + time.system_time;
}
+static uint64_t kvm_get_clock(void)
+{
+ struct kvm_clock_data data;
+ int ret;
+
+ ret = kvm_vm_ioctl(kvm_state, KVM_GET_CLOCK, &data);
+ if (ret < 0) {
+ fprintf(stderr, "KVM_GET_CLOCK failed: %s\n", strerror(ret));
+ abort();
+ }
+ return data.clock;
+}
+
static void kvmclock_vm_state_change(void *opaque, int running,
RunState state)
{
@@ -91,15 +111,31 @@
if (running) {
struct kvm_clock_data data = {};
- uint64_t time_at_migration = kvmclock_current_nsec(s);
+ uint64_t pvclock_via_mem = 0;
- s->clock_valid = false;
+ /*
+ * If the host where s->clock was read did not support reliable
+ * KVM_GET_CLOCK, read kvmclock value from memory.
+ */
+ if (!s->clock_is_reliable) {
+ pvclock_via_mem = kvmclock_current_nsec(s);
+ }
- /* We can't rely on the migrated clock value, just discard it */
- if (time_at_migration) {
- s->clock = time_at_migration;
+ /* migration/savevm/init restore
+ * update clock_is_reliable to match local
+ * host capabilities.
+ */
+ if (s->clock_valid == false) {
+ s->clock_is_reliable = kvm_has_adjust_clock_stable();
}
+ /* We can't rely on the saved clock value, just discard it */
+ if (pvclock_via_mem) {
+ s->clock = pvclock_via_mem;
+ }
+
+ s->clock_valid = false;
+
data.clock = s->clock;
ret = kvm_vm_ioctl(kvm_state, KVM_SET_CLOCK, &data);
if (ret < 0) {
@@ -120,8 +156,6 @@
}
}
} else {
- struct kvm_clock_data data;
- int ret;
if (s->clock_valid) {
return;
@@ -129,13 +163,7 @@
kvm_synchronize_all_tsc();
- ret = kvm_vm_ioctl(kvm_state, KVM_GET_CLOCK, &data);
- if (ret < 0) {
- fprintf(stderr, "KVM_GET_CLOCK failed: %s\n", strerror(ret));
- abort();
- }
- s->clock = data.clock;
-
+ s->clock = kvm_get_clock();
/*
* If the VM is stopped, declare the clock state valid to
* avoid re-reading it on next vmsave (which would return
@@ -149,25 +177,66 @@
{
KVMClockState *s = KVM_CLOCK(dev);
+ if (kvm_has_adjust_clock_stable()) {
+ s->clock_is_reliable = true;
+ }
+
qemu_add_vm_change_state_handler(kvmclock_vm_state_change, s);
}
+static bool kvmclock_clock_is_reliable_needed(void *opaque)
+{
+ KVMClockState *s = opaque;
+
+ return s->mach_use_reliable_get_clock;
+}
+
+static const VMStateDescription kvmclock_reliable_get_clock = {
+ .name = "kvmclock/clock_is_reliable",
+ .version_id = 1,
+ .minimum_version_id = 1,
+ .needed = kvmclock_clock_is_reliable_needed,
+ .fields = (VMStateField[]) {
+ VMSTATE_BOOL(clock_is_reliable, KVMClockState),
+ VMSTATE_END_OF_LIST()
+ }
+};
+
+static void kvmclock_pre_save(void *opaque)
+{
+ KVMClockState *s = opaque;
+
+ s->clock = kvm_get_clock();
+}
+
static const VMStateDescription kvmclock_vmsd = {
.name = "kvmclock",
.version_id = 1,
.minimum_version_id = 1,
+ .pre_save = kvmclock_pre_save,
.fields = (VMStateField[]) {
VMSTATE_UINT64(clock, KVMClockState),
VMSTATE_END_OF_LIST()
+ },
+ .subsections = (const VMStateDescription * []) {
+ &kvmclock_reliable_get_clock,
+ NULL
}
};
+static Property kvmclock_properties[] = {
+ DEFINE_PROP_BOOL("x-mach-use-reliable-get-clock", KVMClockState,
+ mach_use_reliable_get_clock, true),
+ DEFINE_PROP_END_OF_LIST(),
+};
+
static void kvmclock_class_init(ObjectClass *klass, void *data)
{
DeviceClass *dc = DEVICE_CLASS(klass);
dc->realize = kvmclock_realize;
dc->vmsd = &kvmclock_vmsd;
+ dc->props = kvmclock_properties;
}
static const TypeInfo kvmclock_info = {
===================================================================
@@ -370,6 +370,11 @@
#define PC_COMPAT_2_7 \
HW_COMPAT_2_7 \
{\
+ .driver = "kvmclock",\
+ .property = "x-mach-use-reliable-get-clock",\
+ .value = "off",\
+ },\
+ {\
.driver = TYPE_X86_CPU,\
.property = "l3-cache",\
.value = "off",\
===================================================================
@@ -117,6 +117,13 @@
return kvm_check_extension(kvm_state, KVM_CAP_X86_SMM);
}
+bool kvm_has_adjust_clock_stable(void)
+{
+ int ret = kvm_check_extension(kvm_state, KVM_CAP_ADJUST_CLOCK);
+
+ return (ret == KVM_CLOCK_TSC_STABLE);
+}
+
bool kvm_allows_irq0_override(void)
{
return !kvm_irqchip_in_kernel() || kvm_has_gsi_routing();
===================================================================
@@ -17,6 +17,7 @@
bool kvm_allows_irq0_override(void);
bool kvm_has_smm(void);
+bool kvm_has_adjust_clock_stable(void);
void kvm_synchronize_all_tsc(void);
void kvm_arch_reset_vcpu(X86CPU *cs);
void kvm_arch_do_init_vcpu(X86CPU *cs);