[PATCH 5.18 1040/1095] KVM: VMX: Add helper to check if the guest PMU has PERF_GLOBAL_CTRL

[Greg Kroah-Hartman]

From: Sean Christopherson <seanjc@xxxxxxxxxx>

[ 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>
---
 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 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)
 
-- 
2.35.1