KVM: VMX: Add helper to check if the guest PMU has PERF_GLOBAL_CTRL

[ Upstream commit 825db332ac1a23d0d50265b43090f7929d8d03ef ]

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>

diff --git a/arch/x86/kvm/vmx/pmu_intel.c b/arch/x86/kvm/vmx/pmu_intel.c
index f9054e7ec89ed2db382cb3b389544e358b81d890..e624a39365ecb517fb588e97800d0bcaa2cc8a90 100644 (file)
--- a/arch/x86/kvm/vmx/pmu_intel.c
+++ b/arch/x86/kvm/vmx/pmu_intel.c
@@ -104,7 +104,7 @@ 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);
@@ -222,7 +222,7 @@ 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 a8b8150252bb76a32b3b1abf50885618d5e35cd9..20f1213a93685f4378b34b2bcf728528e45cbab2 100644 (file)
--- 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)