Although we never made such commitment clear (well, to the best
of my knowledge), some people expect that two savevm issued in sequence
in a stopped machine will yield the same results. This is not a crazy
requirement, since we don't expect a stopped machine to be updating its state,
for any device.
With kvmclock, this is not the case, since the .pre_save hook will issue an
ioctl to the host to acquire a timestamp, which is always changing.
This patch moves the value acquisition to vm_stop. This should mean our
get clock ioctl is issued more times, but this should be fine since vm_stop
is not a hot path.
When we do migrate, we'll transfer that value along.
Signed-off-by: Glauber Costa <glommer@xxxxxxxxxx>
---
cpus.c | 4 ++++
qemu-kvm-x86.c | 7 ++-----
qemu-kvm.h | 2 ++
3 files changed, 8 insertions(+), 5 deletions(-)
diff --git a/cpus.c b/cpus.c
index a55c330..879a03a 100644
--- a/cpus.c
+++ b/cpus.c
@@ -112,6 +112,10 @@ static void do_vm_stop(int reason)
pause_all_vcpus();
vm_state_notify(0, reason);
monitor_protocol_event(QEVENT_STOP, NULL);
+ if (kvm_enabled()) {
+ kvmclock_update_clock();
+ }
+
}
}
diff --git a/qemu-kvm-x86.c b/qemu-kvm-x86.c
index 20b7d6d..d099d3d 100644
--- a/qemu-kvm-x86.c
+++ b/qemu-kvm-x86.c
@@ -500,11 +500,9 @@ static int kvm_enable_tpr_access_reporting(CPUState *env)
#ifdef KVM_CAP_ADJUST_CLOCK
static struct kvm_clock_data kvmclock_data;
-static void kvmclock_pre_save(void *opaque)
+void kvmclock_update_clock(void)
{
- struct kvm_clock_data *cl = opaque;
-
- kvm_vm_ioctl(kvm_state, KVM_GET_CLOCK, cl);
+ kvm_vm_ioctl(kvm_state, KVM_GET_CLOCK, &kvmclock_data);
}
static int kvmclock_post_load(void *opaque, int version_id)
@@ -519,7 +517,6 @@ static const VMStateDescription vmstate_kvmclock= {
.version_id = 1,
.minimum_version_id = 1,
.minimum_version_id_old = 1,
- .pre_save = kvmclock_pre_save,
.post_load = kvmclock_post_load,
.fields = (VMStateField []) {
VMSTATE_U64(clock, struct kvm_clock_data),
diff --git a/qemu-kvm.h b/qemu-kvm.h
index 0f3fb50..b0b7ab3 100644
--- a/qemu-kvm.h
+++ b/qemu-kvm.h
@@ -752,6 +752,8 @@ int handle_tpr_access(void *opaque, CPUState *env, uint64_t rip,
#define qemu_kvm_cpu_stop(env) do {} while(0)
#endif
+void kvmclock_update_clock(void);
+
#ifdef CONFIG_KVM
typedef struct KVMSlot {
--
1.7.2.3
--
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