This is a note to let you know that I've just added the patch titled KVM: VMX: Add helper to check if the guest PMU has PERF_GLOBAL_CTRL to the 5.18-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: kvm-vmx-add-helper-to-check-if-the-guest-pmu-has-per.patch and it can be found in the queue-5.18 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. commit d297e223ab3f71968097240e39d44fb5cc478e26 Author: Sean Christopherson <seanjc@xxxxxxxxxx> Date: Fri Jul 22 22:44:07 2022 +0000 KVM: VMX: Add helper to check if the guest PMU has PERF_GLOBAL_CTRL [ Upstream commit b663f0b5f3d665c261256d1f76e98f077c6e56af ] 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@xxxxxxxxxxxxxxx Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx> Message-Id: <20220722224409.1336532-4-seanjc@xxxxxxxxxx> Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> diff --git a/arch/x86/kvm/vmx/pmu_intel.c b/arch/x86/kvm/vmx/pmu_intel.c index 2cbd5f183ab5..8bd154f8c966 100644 --- a/arch/x86/kvm/vmx/pmu_intel.c +++ b/arch/x86/kvm/vmx/pmu_intel.c @@ -98,7 +98,7 @@ 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); @@ -215,7 +215,7 @@ 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; default: ret = get_gp_pmc(pmu, msr, MSR_IA32_PERFCTR0) || diff --git a/arch/x86/kvm/vmx/vmx.h b/arch/x86/kvm/vmx/vmx.h index 1e7f9453894b..93aa1f3ea01e 100644 --- a/arch/x86/kvm/vmx/vmx.h +++ b/arch/x86/kvm/vmx/vmx.h @@ -92,6 +92,18 @@ 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)