Re: [PATCH] KVM: x86/vPMU: Forbid reading from MSR_F15H_PERF MSRs when guest doesn't have X86_FEATURE_PERFCTR_CORE

From: Paolo Bonzini
Date: Tue Mar 30 2021 - 13:11:39 EST


On 29/03/21 14:48, Vitaly Kuznetsov wrote:
MSR_F15H_PERF_CTL0-5, MSR_F15H_PERF_CTR0-5 MSRs have a CPUID bit assigned
to them (X86_FEATURE_PERFCTR_CORE) and when it wasn't exposed to the guest
the correct behavior is to inject #GP an not just return zero.

Signed-off-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
---
arch/x86/kvm/x86.c | 6 ++++++
1 file changed, 6 insertions(+)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index fe806e894212..125453155ede 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3381,6 +3381,12 @@ int kvm_get_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
msr_info->data = 0;
break;
case MSR_F15H_PERF_CTL0 ... MSR_F15H_PERF_CTR5:
+ if (kvm_pmu_is_valid_msr(vcpu, msr_info->index))
+ return kvm_pmu_get_msr(vcpu, msr_info);
+ if (!msr_info->host_initiated)
+ return 1;
+ msr_info->data = 0;
+ break;
case MSR_K7_EVNTSEL0 ... MSR_K7_EVNTSEL3:
case MSR_K7_PERFCTR0 ... MSR_K7_PERFCTR3:
case MSR_P6_PERFCTR0 ... MSR_P6_PERFCTR1:


Queued to kvm/next, thanks (the write side goes to kvm/master instead).

Paolo