@@ -35,6 +35,13 @@ typedef struct KVMClockState {
/*< public >*/
uint64_t clock;
+ /* whether the value in 'clock' is reliable (i.e. was set by a host
+ * with reliable KVM_GET_CLOCK) */
+ bool clock_is_reliable;
+ /* Enable migration of clock_is_reliable. Some machine-types
+ * will disable it for compatibility with older QEMU versions.
+ */
+ bool migrate_reliable_flag;
bool clock_valid;
} KVMClockState;
@@ -81,6 +88,20 @@ static uint64_t kvmclock_current_nsec(KVMClockState *s)
return nsec + time.system_time;
}
+static void kvm_get_clock(KVMClockState *s)
+{
+ 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();
+ }
+ s->clock = data.clock;
+ s->clock_is_reliable = kvm_has_adjust_clock_stable();
+}
+
static void kvmclock_vm_state_change(void *opaque, int running,
RunState state)
{
@@ -91,16 +112,18 @@ static void kvmclock_vm_state_change(void *opaque, int running,
if (running) {
struct kvm_clock_data data = {};
- uint64_t time_at_migration = kvmclock_current_nsec(s);
s->clock_valid = false;
- /* We can't rely on the migrated clock value, just discard it */
- if (time_at_migration) {
- s->clock = time_at_migration;
+ /* if host that set s->clock did not support reliable KVM_GET_CLOCK,
+ * read kvmclock value from memory
+ */
+ if (!s->clock_is_reliable) {
+ data.clock = kvmclock_current_nsec(s);
+ } else {
+ data.clock = s->clock;
}
- data.clock = s->clock;
ret = kvm_vm_ioctl(kvm_state, KVM_SET_CLOCK, &data);
if (ret < 0) {
fprintf(stderr, "KVM_SET_CLOCK failed: %s\n", strerror(ret));
@@ -120,22 +143,23 @@ static void kvmclock_vm_state_change(void *opaque, int running,
}
}
} else {
- struct kvm_clock_data data;
- int ret;
+ /*FIXME: is this really possible to happen?
+ * Can kvmclock_vm_state_change(s, 0) be called twice without
+ * a kvmclock_vm_state_change(s, 1) call in between?
+ */
if (s->clock_valid) {
return;
}
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;
-
+ kvm_get_clock(s);
+ /* FIXME: the comment below doesn't match what is done at
+ * kvmclock_pre_save(). The comment must be updated, or
+ * kvmclock_pre_save() must be changed. I don't know what's
+ * the right thing to do.
+ */
/*
* If the VM is stopped, declare the clock state valid to
* avoid re-reading it on next vmsave (which would return
@@ -152,22 +176,65 @@ static void kvmclock_realize(DeviceState *dev, Error **errp)
qemu_add_vm_change_state_handler(kvmclock_vm_state_change, s);
}
+static bool kvmclock_src_use_reliable_get_clock(void *opaque)
+{
+ KVMClockState *s = opaque;
+
+ return s->migrate_reliable_flag;
+}
+
+static const VMStateDescription kvmclock_reliable_get_clock = {
+ .name = "kvmclock/clock_is_reliable",
+ .version_id = 1,
+ .minimum_version_id = 1,
+ .needed = kvmclock_src_use_reliable_get_clock,
+ .fields = (VMStateField[]) {
+ VMSTATE_BOOL(clock_is_reliable, KVMClockState),
+ VMSTATE_END_OF_LIST()
+ }
+};
+
+static void kvmclock_pre_save(void *opaque)
+{
+ KVMClockState *s = opaque;
+ /*TODO: add comment explaining why this is here:
+ * "re-read clock value here because [...]"" */
+
+ /*XXX: is it correct to call kvm_get_clock() here
+ * if s->clock_is_valid is true? (meaning the kvmclock was
+ * already stopped)
+ */
+ kvm_get_clock(s);
+}
+
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-migrate-reliable-flag", KVMClockState,
+ migrate_reliable_flag, 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 = {
@@ -372,6 +372,11 @@ bool e820_get_entry(int, uint32_t, uint64_t *, uint64_t *);
#define PC_COMPAT_2_7 \
HW_COMPAT_2_7 \
{\
+ .driver = "kvmclock",\
+ .property = "x-migrate-reliable-flag",\
+ .value = "off",\
+ },\
+ {\
.driver = TYPE_X86_CPU,\
.property = "l3-cache",\
.value = "off",\
@@ -117,6 +117,13 @@ bool kvm_has_smm(void)
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);