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    Subject[PATCH 5.19 1107/1157] KVM: VMX: Add helper to check if the guest PMU has PERF_GLOBAL_CTRL
    Date
    From: Sean Christopherson <seanjc@google.com>

    [ 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@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>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    arch/x86/kvm/vmx/pmu_intel.c | 4 ++--
    arch/x86/kvm/vmx/vmx.h | 12 ++++++++++++
    2 files changed, 14 insertions(+), 2 deletions(-)

    diff --git a/arch/x86/kvm/vmx/pmu_intel.c b/arch/x86/kvm/vmx/pmu_intel.c
    index 8faac421171f..a9280ebf78f5 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)

    --
    2.35.1


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