From 953899b659adce62cbe83d6a7527550ab8797c48 Mon Sep 17 00:00:00 2001 From: Joerg Roedel Date: Mon, 14 Dec 2009 12:22:20 +0100 Subject: [PATCH] KVM: SVM: Adjust tsc_offset only if tsc_unstable 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 --- arch/x86/kvm/svm.c | 18 ++++++++++-------- 1 file changed, 10 insertions(+), 8 deletions(-) diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c index 7f4e225feebf..b373ae6fb974 100644 --- a/arch/x86/kvm/svm.c +++ b/arch/x86/kvm/svm.c @@ -765,14 +765,16 @@ static void svm_vcpu_load(struct kvm_vcpu *vcpu, int cpu) if (unlikely(cpu != vcpu->cpu)) { u64 delta; - /* - * 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; + 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; -- 2.20.1