The patch below does not apply to the 4.19-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From b663f0b5f3d665c261256d1f76e98f077c6e56af Mon Sep 17 00:00:00 2001 From: Sean Christopherson seanjc@google.com Date: Fri, 22 Jul 2022 22:44:07 +0000 Subject: [PATCH] KVM: VMX: Add helper to check if the guest PMU has PERF_GLOBAL_CTRL
Add a helper to check of the guest PMU has PERF_GLOBAL_CTRL, which is unintuitive _and_ diverges from Intel's architecturally defined behavior. Even worse, KVM currently implements the check using two different (but equivalent) checks, _and_ there has been at least one attempt to add a _third_ flavor.
Cc: stable@vger.kernel.org Signed-off-by: Sean Christopherson seanjc@google.com Message-Id: 20220722224409.1336532-4-seanjc@google.com Signed-off-by: Paolo Bonzini pbonzini@redhat.com
diff --git a/arch/x86/kvm/vmx/pmu_intel.c b/arch/x86/kvm/vmx/pmu_intel.c index 6e355c5d2f40..78f2800fd850 100644 --- a/arch/x86/kvm/vmx/pmu_intel.c +++ b/arch/x86/kvm/vmx/pmu_intel.c @@ -111,7 +111,7 @@ static bool intel_pmc_is_enabled(struct kvm_pmc *pmc) { struct kvm_pmu *pmu = pmc_to_pmu(pmc);
- if (pmu->version < 2) + if (!intel_pmu_has_perf_global_ctrl(pmu)) return true;
return test_bit(pmc->idx, (unsigned long *)&pmu->global_ctrl); @@ -207,7 +207,7 @@ static bool intel_is_valid_msr(struct kvm_vcpu *vcpu, u32 msr) case MSR_CORE_PERF_GLOBAL_STATUS: case MSR_CORE_PERF_GLOBAL_CTRL: case MSR_CORE_PERF_GLOBAL_OVF_CTRL: - ret = pmu->version > 1; + return intel_pmu_has_perf_global_ctrl(pmu); break; case MSR_IA32_PEBS_ENABLE: ret = vcpu_get_perf_capabilities(vcpu) & PERF_CAP_PEBS_FORMAT; diff --git a/arch/x86/kvm/vmx/vmx.h b/arch/x86/kvm/vmx/vmx.h index 286c88e285ea..2a0b94e0fda7 100644 --- a/arch/x86/kvm/vmx/vmx.h +++ b/arch/x86/kvm/vmx/vmx.h @@ -91,6 +91,18 @@ union vmx_exit_reason { u32 full; };
+static inline bool intel_pmu_has_perf_global_ctrl(struct kvm_pmu *pmu) +{ + /* + * Architecturally, Intel's SDM states that IA32_PERF_GLOBAL_CTRL is + * supported if "CPUID.0AH: EAX[7:0] > 0", i.e. if the PMU version is + * greater than zero. However, KVM only exposes and emulates the MSR + * to/for the guest if the guest PMU supports at least "Architectural + * Performance Monitoring Version 2". + */ + return pmu->version > 1; +} + #define vcpu_to_lbr_desc(vcpu) (&to_vmx(vcpu)->lbr_desc) #define vcpu_to_lbr_records(vcpu) (&to_vmx(vcpu)->lbr_desc.records)