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authorSean Christopherson <seanjc@google.com>2022-10-06 03:03:08 +0300
committerPaolo Bonzini <pbonzini@redhat.com>2022-11-02 20:17:58 +0300
commit145dfad998eac74abc59219d936e905766ba2d98 (patch)
tree2f3c21c089436c57917e234640f1ceee2bf4633d /arch
parent7353633814f6e5b4899fb9ee1483709d6bb0e1cd (diff)
downloadlinux-145dfad998eac74abc59219d936e905766ba2d98.tar.xz
KVM: VMX: Advertise PMU LBRs if and only if perf supports LBRs
Advertise LBR support to userspace via MSR_IA32_PERF_CAPABILITIES if and only if perf fully supports LBRs. Perf may disable LBRs (by zeroing the number of LBRs) even on platforms the allegedly support LBRs, e.g. if probing any LBR MSRs during setup fails. Fixes: be635e34c284 ("KVM: vmx/pmu: Expose LBR_FMT in the MSR_IA32_PERF_CAPABILITIES") Reported-by: Like Xu <like.xu.linux@gmail.com> Signed-off-by: Sean Christopherson <seanjc@google.com> Message-Id: <20221006000314.73240-3-seanjc@google.com> Cc: stable@vger.kernel.org Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'arch')
-rw-r--r--arch/x86/kvm/vmx/capabilities.h4
1 files changed, 3 insertions, 1 deletions
diff --git a/arch/x86/kvm/vmx/capabilities.h b/arch/x86/kvm/vmx/capabilities.h
index 87c4e46daf37..3bd7a8970618 100644
--- a/arch/x86/kvm/vmx/capabilities.h
+++ b/arch/x86/kvm/vmx/capabilities.h
@@ -400,6 +400,7 @@ static inline bool vmx_pebs_supported(void)
static inline u64 vmx_get_perf_capabilities(void)
{
u64 perf_cap = PMU_CAP_FW_WRITES;
+ struct x86_pmu_lbr lbr;
u64 host_perf_cap = 0;
if (!enable_pmu)
@@ -408,7 +409,8 @@ static inline u64 vmx_get_perf_capabilities(void)
if (boot_cpu_has(X86_FEATURE_PDCM))
rdmsrl(MSR_IA32_PERF_CAPABILITIES, host_perf_cap);
- perf_cap |= host_perf_cap & PMU_CAP_LBR_FMT;
+ if (x86_perf_get_lbr(&lbr) >= 0 && lbr.nr)
+ perf_cap |= host_perf_cap & PMU_CAP_LBR_FMT;
if (vmx_pebs_supported()) {
perf_cap |= host_perf_cap & PERF_CAP_PEBS_MASK;