Commit b663f0b5 authored by Sean Christopherson's avatar Sean Christopherson Committed by Paolo Bonzini
Browse files

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: default avatarSean Christopherson <seanjc@google.com>
Message-Id: <20220722224409.1336532-4-seanjc@google.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 93255bf9

arch/x86/kvm/vmx/pmu_intel.c

+2 −2
Original line number Diff line number Diff line
@@ -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;

arch/x86/kvm/vmx/vmx.h

+12 −0
Original line number Diff line number Diff line
@@ -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)