FAILED: patch "[PATCH] KVM: VMX: Add helper to check if the guest PMU has" failed to apply to 4.19-stable tree

PATCH [email protected] 1 participant 1 message Aug 12, 2022

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Stable branch x86 KVM x86

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2022-08-12 15:33 UTC #0 lore raw

The patch below does not apply to the 4.19-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From b663f0b5f3d665c261256d1f76e98f077c6e56af Mon Sep 17 00:00:00 2001
From: Sean Christopherson <[email protected]>
Date: Fri, 22 Jul 2022 22:44:07 +0000
Subject: [PATCH] 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 [email protected]

Signed-off-by Sean Christopherson <[email protected]>

Message-Id: <[email protected]>

Signed-off-by Paolo Bonzini <[email protected]>

arch/x86/kvm/vmx/pmu_intel.c +2 -2

index 6e355c5d2f40..78f2800fd850 100644
@@ -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

index 286c88e285ea..2a0b94e0fda7 100644
@@ -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)