When CPUs with unstable TSCs enter deep C-state, TSC may stop running. This causes us to require resynchronization. Since we can't tell when this may potentially happen, we assume the worst by forcing re-compensation for it at every point the VCPU task is descheduled. Signed-off-by: Zachary Amsden <zamsden@xxxxxxxxxx> --- arch/x86/kvm/x86.c | 11 +++++++++++ 1 files changed, 11 insertions(+), 0 deletions(-) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index c8289d0..618c435 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -1822,7 +1822,18 @@ void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu) { kvm_x86_ops->vcpu_put(vcpu); kvm_put_guest_fpu(vcpu); + vcpu->arch.last_host_tsc = native_read_tsc(); + + /* + * When potentially leaving a CPU with unstable TSCs, we risk + * that the CPU enters deep C-state. If it does, the TSC may + * go out of sync but we will not recalibrate because the test + * vcpu->cpu != cpu can not detect this condition. So set + * vcpu->cpu = -1 to force the recalibration above. + */ + if (check_tsc_unstable()) + vcpu->cpu = -1; } static int is_efer_nx(void) -- 1.7.1 -- 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