From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754806Ab0ISAiV (ORCPT ); Sat, 18 Sep 2010 20:38:21 -0400 Received: from mx1.redhat.com ([209.132.183.28]:21066 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753661Ab0ISAiU (ORCPT ); Sat, 18 Sep 2010 20:38:20 -0400 From: Zachary Amsden To: kvm@vger.kernel.org Cc: Zachary Amsden , Avi Kivity , Marcelo Tosatti , Glauber Costa , linux-kernel@vger.kernel.org Subject: [KVM timekeeping fixes 1/4] Fix kvmclock bug Date: Sat, 18 Sep 2010 14:38:12 -1000 Message-Id: <1284856695-19438-1-git-send-email-zamsden@redhat.com> Organization: Frobozz Magic Timekeeping Company Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org If preempted after kvmclock values are updated, but before hardware virtualization is entered, the last tsc time as read by the guest is never set. It underflows the next time kvmclock is updated if there has not yet been a successful entry / exit into hardware virt. Fix this by simply setting last_tsc to the newly read tsc value so that any computed nsec advance of kvmclock is nulled. Signed-off-by: Zachary Amsden --- arch/x86/kvm/x86.c | 1 + 1 files changed, 1 insertions(+), 0 deletions(-) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index a51635e..0b021e1 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -1095,6 +1095,7 @@ static int kvm_write_guest_time(struct kvm_vcpu *v) vcpu->hv_clock.tsc_timestamp = tsc_timestamp; vcpu->hv_clock.system_time = kernel_ns + v->kvm->arch.kvmclock_offset; vcpu->last_kernel_ns = kernel_ns; + vcpu->last_guest_tsc = tsc_timestamp; vcpu->hv_clock.flags = 0; /* -- 1.6.6.1