From c2b01cfec1f1426d95c27abacc3ea5b5fbb9a57e Mon Sep 17 00:00:00 2001 From: Michael Chapman Date: Fri, 6 Apr 2018 15:34:06 +1000 Subject: [PATCH] kvmclock: fix clock_is_reliable on migration from QEMU < 2.9 When migrating from a pre-2.9 QEMU, no clock_is_reliable flag is transferred. We should assume that the source host has an unreliable KVM_GET_CLOCK, rather than using whatever was determined locally, to ensure that any drift from the TSC-based value calculated by the guest is corrected. Signed-off-by: Michael Chapman Message-Id: <20180406053406.774-1-mike@very.puzzling.org> Signed-off-by: Paolo Bonzini --- hw/i386/kvm/clock.c | 14 ++++++++++++++ 1 file changed, 14 insertions(+) diff --git a/hw/i386/kvm/clock.c b/hw/i386/kvm/clock.c index 1707434db3..7dac319403 100644 --- a/hw/i386/kvm/clock.c +++ b/hw/i386/kvm/clock.c @@ -241,6 +241,19 @@ static const VMStateDescription kvmclock_reliable_get_clock = { } }; +/* + * When migrating, assume the source has an unreliable + * KVM_GET_CLOCK unless told otherwise. + */ +static int kvmclock_pre_load(void *opaque) +{ + KVMClockState *s = opaque; + + s->clock_is_reliable = false; + + return 0; +} + /* * When migrating, read the clock just before migration, * so that the guest clock counts during the events @@ -268,6 +281,7 @@ static const VMStateDescription kvmclock_vmsd = { .name = "kvmclock", .version_id = 1, .minimum_version_id = 1, + .pre_load = kvmclock_pre_load, .pre_save = kvmclock_pre_save, .fields = (VMStateField[]) { VMSTATE_UINT64(clock, KVMClockState), -- GitLab