From: Chris Lalancette

Older linux guests (in this case, 2.6.9) can attempt to
access the performance counter MSRs without a fixup section, and injecting
a GPF kills the guest. Work around by allowing the guest to write those MSRs.

Tested by me on RHEL-4 i386 and x86_64 guests, as well as F-9 guests.

Signed-off-by: Chris Lalancette
Signed-off-by: Avi Kivity
arch/x86/kvm/vmx.c | 12 ++++++++++++
1 files changed, 12 insertions(+), 0 deletions(-)

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index d7522aa..ea6bcf5 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -921,6 +921,18 @@ static int vmx_set_msr(struct kvm_vcpu *vcpu, u32 msr_index, u64 data)
+ case MSR_P6_PERFCTR0:
+ case MSR_P6_PERFCTR1:
+ case MSR_P6_EVNTSEL0:
+ case MSR_P6_EVNTSEL1:
+ /*
+ * Just discard all writes to the performance counters; this
+ * should keep both older linux and windows 64-bit guests
+ * happy
+ */
+ pr_unimpl(vcpu, "unimplemented perfctr wrmsr: 0x%x data 0x%llx\n", msr_index, data);
+ break;
msr = find_msr_entry(vmx, msr_index);

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