On Mon, Jun 02, 2014 at 10:31:44PM +0200, Marcin Gibuła wrote:
+ cpu_physical_memory_read(kvmclock_struct_pa, &time, sizeof(time));
+
+ delta = migration_tsc - time.tsc_timestamp;
Hi,
when I was testing live storage migration with libvirt I found out
that this patch can cause virtual machine to hang when completing
mirror job.
This is (probably) because kvmclock_current_nsec() is called twice
in a row and on second call time.tsc_timestamp is larger than
migration_tsc. This causes delta to be huge and sets timer to
invalid value.
The double call happens when switching from old to new disk
(pivoting in libvirt's nomenclature).
Example values:
First call: migration_tsc: 12052203518652476, time_tsc:
12052203301565676, delta 108543400
Second call: migration_tsc: 12052203518652476, time_tsc:
12052204478600322, delta 9223372036374801885
Perhaps it is worth adding:
if (time.tsc_timestamp > migration_tsc) {
return 0;
}
there? Untested though...
Hi Marcin,
Can you give this patch a try? Should read the guest TSC values after
stopping the VM.
diff --git a/hw/i386/kvm/clock.c b/hw/i386/kvm/clock.c
index 6f4ed28a..bef2504 100644
--- a/hw/i386/kvm/clock.c
+++ b/hw/i386/kvm/clock.c
@@ -17,6 +17,7 @@
#include "qemu/host-utils.h"
#include "sysemu/sysemu.h"
#include "sysemu/kvm.h"
+#include "sysemu/cpus.h"
#include "hw/sysbus.h"
#include "hw/kvm/clock.h"
@@ -65,6 +66,7 @@ static uint64_t kvmclock_current_nsec(KVMClockState *s)
cpu_physical_memory_read(kvmclock_struct_pa, &time, sizeof(time));
+ assert(time.tsc_timestamp <= migration_tsc);
delta = migration_tsc - time.tsc_timestamp;
if (time.tsc_shift < 0) {
delta >>= -time.tsc_shift;
@@ -123,6 +125,8 @@ static void kvmclock_vm_state_change(void *opaque, int
running,
if (s->clock_valid) {
return;
}
+
+ cpu_synchronize_all_states();
ret = kvm_vm_ioctl(kvm_state, KVM_GET_CLOCK, &data);
if (ret < 0) {
fprintf(stderr, "KVM_GET_CLOCK failed: %s\n", strerror(ret));