From cd80c840270c7b57bc38d6e2e1647e84ce23075d Mon Sep 17 00:00:00 2001 From: Joerg Roedel Date: Thu, 28 Oct 2010 16:48:13 -0200 Subject: KVM: SVM: Adjust tsc_offset only if tsc_unstable commit 953899b659adce62cbe83d6a7527550ab8797c48 upstream. The tsc_offset adjustment in svm_vcpu_load is executed unconditionally even if Linux considers the host tsc as stable. This causes a Linux guest detecting an unstable tsc in any case. This patch removes the tsc_offset adjustment if the host tsc is stable. The guest will now get the benefit of a stable tsc too. Signed-off-by: Joerg Roedel Signed-off-by: Avi Kivity Signed-off-by: Greg Kroah-Hartman --- arch/x86/kvm/svm.c | 23 ++++++++++++----------- 1 file changed, 12 insertions(+), 11 deletions(-) diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c index 52ffdc68a60a..925c326cab5b 100644 --- a/arch/x86/kvm/svm.c +++ b/arch/x86/kvm/svm.c @@ -795,17 +795,18 @@ static void svm_vcpu_load(struct kvm_vcpu *vcpu, int cpu) int i; if (unlikely(cpu != vcpu->cpu)) { - u64 tsc_this, delta; - - /* - * Make sure that the guest sees a monotonically - * increasing TSC. - */ - rdtscll(tsc_this); - delta = vcpu->arch.host_tsc - tsc_this; - svm->vmcb->control.tsc_offset += delta; - if (is_nested(svm)) - svm->nested.hsave->control.tsc_offset += delta; + u64 delta; + + if (check_tsc_unstable()) { + /* + * Make sure that the guest sees a monotonically + * increasing TSC. + */ + delta = vcpu->arch.host_tsc - native_read_tsc(); + svm->vmcb->control.tsc_offset += delta; + if (is_nested(svm)) + svm->nested.hsave->control.tsc_offset += delta; + } vcpu->cpu = cpu; kvm_migrate_timers(vcpu); svm->asid_generation = 0; -- cgit v1.2.3