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authorJoerg Roedel <joerg.roedel@amd.com>2009-12-14 12:22:20 +0100
committerMarcelo Tosatti <mtosatti@redhat.com>2010-03-01 12:35:41 -0300
commit953899b659adce62cbe83d6a7527550ab8797c48 (patch)
tree5eb465ea6b419ba58d310fec6c3e619fd4dd148d
parent4e47c7a6d714cf352b719db92a924b6ec487acc5 (diff)
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 <joerg.roedel@amd.com> Signed-off-by: Avi Kivity <avi@redhat.com>
-rw-r--r--arch/x86/kvm/svm.c18
1 files changed, 10 insertions, 8 deletions
diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index 7f4e225feeb..b373ae6fb97 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;