From 145dfad998eac74abc59219d936e905766ba2d98 Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Thu, 6 Oct 2022 00:03:08 +0000 Subject: 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 Signed-off-by: Sean Christopherson Message-Id: <20221006000314.73240-3-seanjc@google.com> Cc: stable@vger.kernel.org Signed-off-by: Paolo Bonzini --- arch/x86/kvm/vmx/capabilities.h | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) (limited to 'arch/x86') 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; -- cgit v1.2.3