path: root/arch/x86/kvm/svm/pmu.c
diff options
authorVitaly Kuznetsov <vkuznets@redhat.com>2021-03-23 09:45:15 +0100
committerPaolo Bonzini <pbonzini@redhat.com>2021-03-30 13:07:10 -0400
commit1973cadd4cca08eaeca944f60598f04ab0d80682 (patch)
treebbac545a056e14aeabb38bef2c0145aa557f0c87 /arch/x86/kvm/svm/pmu.c
parentecaf088f53fcc893cd00c846f53042a536b9630d (diff)
KVM: x86/vPMU: Forbid writing to MSR_F15H_PERF MSRs when guest doesn't have X86_FEATURE_PERFCTR_CORE
MSR_F15H_PERF_CTL0-5, MSR_F15H_PERF_CTR0-5 MSRs are only available when X86_FEATURE_PERFCTR_CORE CPUID bit was exposed to the guest. KVM, however, allows these MSRs unconditionally because kvm_pmu_is_valid_msr() -> amd_msr_idx_to_pmc() check always passes and because kvm_pmu_set_msr() -> amd_pmu_set_msr() doesn't fail. In case of a counter (CTRn), no big harm is done as we only increase internal PMC's value but in case of an eventsel (CTLn), we go deep into perf internals with a non-existing counter. Note, kvm_get_msr_common() just returns '0' when these MSRs don't exist and this also seems to contradict architectural behavior which is #GP (I did check one old Opteron host) but changing this status quo is a bit scarier. Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com> Message-Id: <20210323084515.1346540-1-vkuznets@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'arch/x86/kvm/svm/pmu.c')
1 files changed, 8 insertions, 0 deletions
diff --git a/arch/x86/kvm/svm/pmu.c b/arch/x86/kvm/svm/pmu.c
index 035da07500e8..fdf587f19c5f 100644
--- a/arch/x86/kvm/svm/pmu.c
+++ b/arch/x86/kvm/svm/pmu.c
@@ -98,6 +98,8 @@ static enum index msr_to_index(u32 msr)
static inline struct kvm_pmc *get_gp_pmc_amd(struct kvm_pmu *pmu, u32 msr,
enum pmu_type type)
+ struct kvm_vcpu *vcpu = pmu_to_vcpu(pmu);
switch (msr) {
case MSR_F15H_PERF_CTL0:
case MSR_F15H_PERF_CTL1:
@@ -105,6 +107,9 @@ static inline struct kvm_pmc *get_gp_pmc_amd(struct kvm_pmu *pmu, u32 msr,
case MSR_F15H_PERF_CTL3:
case MSR_F15H_PERF_CTL4:
case MSR_F15H_PERF_CTL5:
+ if (!guest_cpuid_has(vcpu, X86_FEATURE_PERFCTR_CORE))
+ return NULL;
+ fallthrough;
if (type != PMU_TYPE_EVNTSEL)
return NULL;
@@ -115,6 +120,9 @@ static inline struct kvm_pmc *get_gp_pmc_amd(struct kvm_pmu *pmu, u32 msr,
case MSR_F15H_PERF_CTR3:
case MSR_F15H_PERF_CTR4:
case MSR_F15H_PERF_CTR5:
+ if (!guest_cpuid_has(vcpu, X86_FEATURE_PERFCTR_CORE))
+ return NULL;
+ fallthrough;
if (type != PMU_TYPE_COUNTER)
return NULL;