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authorJoerg Roedel <joerg.roedel@amd.com>2010-10-28 16:48:13 -0200
committerGreg Kroah-Hartman <gregkh@suse.de>2010-11-22 10:47:34 -0800
commitcd80c840270c7b57bc38d6e2e1647e84ce23075d (patch)
tree14a8ed02bde77ca9b2e5c5ecd8fdcbe690948475 /arch
parentffc109c28a6a4cb5047df82b1d18ad7a13d3e247 (diff)
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 <joerg.roedel@amd.com> Signed-off-by: Avi Kivity <avi@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Diffstat (limited to 'arch')
-rw-r--r--arch/x86/kvm/svm.c23
1 files 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;