Messages in this thread Patch in this message | | | Date | Fri, 19 Nov 2010 13:42:59 -0800 | From | Greg KH <> | Subject | [19/45] KVM: SVM: Adjust tsc_offset only if tsc_unstable |
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2.6.32-stable review patch. If anyone has any objections, please let us know.
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From: Joerg Roedel <joerg.roedel@amd.com>
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 <joerg.roedel@amd.com> Signed-off-by: Avi Kivity <avi@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
--- arch/x86/kvm/svm.c | 21 +++++++++++---------- 1 file changed, 11 insertions(+), 10 deletions(-)
--- a/arch/x86/kvm/svm.c +++ b/arch/x86/kvm/svm.c @@ -795,17 +795,18 @@ static void svm_vcpu_load(struct kvm_vcp int i; if (unlikely(cpu != vcpu->cpu)) { - u64 tsc_this, delta; + u64 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; + 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;
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