linux-kernel - [PATCH v4 12/12] KVM: x86/cpuid: Add AMD CPUID ExtPerfMonAndDbg leaf 0x80000022

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Message-Id: <20230214050757.9623-13-likexu@tencent.com>
Date:   Tue, 14 Feb 2023 13:07:57 +0800
From:   Like Xu <like.xu.linux@...il.com>
To:     Sean Christopherson <seanjc@...gle.com>
Cc:     Paolo Bonzini <pbonzini@...hat.com>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, Sandipan Das <sandipan.das@....com>
Subject: [PATCH v4 12/12] KVM: x86/cpuid: Add AMD CPUID ExtPerfMonAndDbg leaf 0x80000022

From: Like Xu <likexu@...cent.com>

CPUID leaf 0x80000022 i.e. ExtPerfMonAndDbg advertises some new
performance monitoring features for AMD processors.

Bit 0 of EAX indicates support for Performance Monitoring Version 2
(PerfMonV2) features. If found to be set during PMU initialization,
the EBX bits of the same CPUID function can be used to determine
the number of available PMCs for different PMU types.

Expose the relevant bits via KVM_GET_SUPPORTED_CPUID so that
guests can make use of the PerfMonV2 features.

Co-developed-by: Sandipan Das <sandipan.das@....com>
Signed-off-by: Sandipan Das <sandipan.das@....com>
Signed-off-by: Like Xu <likexu@...cent.com>
---
 arch/x86/kvm/cpuid.c   | 24 +++++++++++++++++++++++-
 arch/x86/kvm/svm/svm.c |  6 ++++++
 2 files changed, 29 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index b0bb5f9f5307..274cae531d7f 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -1124,7 +1124,7 @@ static inline int __do_cpuid_func(struct kvm_cpuid_array *array, u32 function)
 		entry->edx = 0;
 		break;
 	case 0x80000000:
-		entry->eax = min(entry->eax, 0x80000021);
+		entry->eax = min(entry->eax, 0x80000022);
 		/*
 		 * Serializing LFENCE is reported in a multitude of ways, and
 		 * NullSegClearsBase is not reported in CPUID on Zen2; help
@@ -1247,6 +1247,28 @@ static inline int __do_cpuid_func(struct kvm_cpuid_array *array, u32 function)
 		if (!static_cpu_has_bug(X86_BUG_NULL_SEG))
 			entry->eax |= BIT(6);
 		break;
+	/* AMD Extended Performance Monitoring and Debug */
+	case 0x80000022: {
+		union cpuid_0x80000022_ebx ebx;
+
+		entry->ecx = entry->edx = 0;
+		if (!enable_pmu || !kvm_cpu_cap_has(X86_FEATURE_PERFMON_V2)) {
+			entry->eax = entry->ebx;
+			break;
+		}
+
+		cpuid_entry_override(entry, CPUID_8000_0022_EAX);
+
+		if (kvm_cpu_cap_has(X86_FEATURE_PERFMON_V2))
+			ebx.split.num_core_pmc = kvm_pmu_cap.num_counters_gp;
+		else if (kvm_cpu_cap_has(X86_FEATURE_PERFCTR_CORE))
+			ebx.split.num_core_pmc = AMD64_NUM_COUNTERS_CORE;
+		else
+			ebx.split.num_core_pmc = AMD64_NUM_COUNTERS;
+
+		entry->ebx = ebx.full;
+		break;
+	}
 	/*Add support for Centaur's CPUID instruction*/
 	case 0xC0000000:
 		/*Just support up to 0xC0000004 now*/
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index f4a4691b4f4e..2472fa8746c2 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -4916,6 +4916,12 @@ static __init void svm_set_cpu_caps(void)
 		} else {
 			/* AMD PMU PERFCTR_CORE CPUID */
 			kvm_cpu_cap_check_and_set(X86_FEATURE_PERFCTR_CORE);
+			/*
+			 * KVM only supports AMD PerfMon V2, even if it supports V3+.
+			 * For PerfMon V3+, it's unsafe to expect V2 bit is set or cleared.
+			 */
+			if (kvm_pmu_cap.version > 1)
+				kvm_cpu_cap_set(X86_FEATURE_PERFMON_V2);
 		}
 	}
 
-- 
2.39.1