When a guest migrates to a new host, the system time difference from the previous host is used in the updates to the kvmclock system time visible to the guest, resulting in a continuation of correct kvmclock based guest timekeeping. The wall clock component of the kvmclock provided time is currently not updated with this same time offset. Since the Linux guest caches the wall clock based time, this discrepency is not noticed until the guest is rebooted. After reboot the guest's time calculations are off. This patch adjusts the wall clock by the kvmclock_offset, resulting in correct guest time after a reboot. Cc: Glauber Costa <glommer@xxxxxxxxxx> Cc: Zachary Amsden <zamsden@xxxxxxxxxx> Signed-off-by: Bruce Rogers <brogers@xxxxxxxx> --- arch/x86/kvm/x86.c | 4 ++++ 1 files changed, 4 insertions(+), 0 deletions(-) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index be6d549..14c290d 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -907,6 +907,10 @@ static void kvm_write_wall_clock(struct kvm *kvm, gpa_t wall_clock) */ getboottime(&boot); + if (kvm->arch.kvmclock_offset) { + struct timespec ts = ns_to_timespec(kvm->arch.kvmclock_offset); + boot = timespec_sub(boot, ts); + } wc.sec = boot.tv_sec; wc.nsec = boot.tv_nsec; wc.version = version; -- 1.7.7 -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html