lkml.org 
[lkml]   [2010]   [Nov]   [19]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
Subject[19/45] KVM: SVM: Adjust tsc_offset only if tsc_unstable
2.6.32-stable review patch.  If anyone has any objections, please let us know.

------------------
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;



\
 
 \ /
  Last update: 2010-11-19 22:53    [from the cache]
©2003-2014 Jasper Spaans. Advertise on this site