linux-kernel - [PATCH v2 3/3] KVM: x86/pmu: Limit the maximum number of supported AMD GP counters

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Date:   Wed,  7 Sep 2022 18:48:38 +0800
From:   Like Xu <like.xu.linux@...il.com>
To:     Sean Christopherson <seanjc@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>
Cc:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        Jim Mattson <jmattson@...gle.com>
Subject: [PATCH v2 3/3] KVM: x86/pmu: Limit the maximum number of supported AMD GP counters

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

The AMD PerfMonV2 specification allows for a maximum of 16 GP counters,
which is clearly not supported with zero code effort in the current KVM.

A local macro (named like INTEL_PMC_MAX_GENERIC) is introduced to
take back control of this virt capability, which also makes it easier to
statically partition all available counters between hosts and guests.

Signed-off-by: Like Xu <likexu@...cent.com>
Reviewed-by: Jim Mattson <jmattson@...gle.com>
---
 arch/x86/include/asm/kvm_host.h | 1 +
 arch/x86/kvm/svm/pmu.c          | 7 ++++---
 arch/x86/kvm/x86.c              | 3 +++
 3 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 70b8266b0474..5c941ace8f67 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -506,6 +506,7 @@ struct kvm_pmc {
 #define MSR_ARCH_PERFMON_PERFCTR_MAX	(MSR_ARCH_PERFMON_PERFCTR0 + KVM_INTEL_PMC_MAX_GENERIC - 1)
 #define MSR_ARCH_PERFMON_EVENTSEL_MAX	(MSR_ARCH_PERFMON_EVENTSEL0 + KVM_INTEL_PMC_MAX_GENERIC - 1)
 #define KVM_PMC_MAX_FIXED	3
+#define KVM_AMD_PMC_MAX_GENERIC	AMD64_NUM_COUNTERS_CORE
 struct kvm_pmu {
 	unsigned nr_arch_gp_counters;
 	unsigned nr_arch_fixed_counters;
diff --git a/arch/x86/kvm/svm/pmu.c b/arch/x86/kvm/svm/pmu.c
index f24613a108c5..e696979ee395 100644
--- a/arch/x86/kvm/svm/pmu.c
+++ b/arch/x86/kvm/svm/pmu.c
@@ -271,9 +271,10 @@ static void amd_pmu_init(struct kvm_vcpu *vcpu)
 	struct kvm_pmu *pmu = vcpu_to_pmu(vcpu);
 	int i;
 
-	BUILD_BUG_ON(AMD64_NUM_COUNTERS_CORE > INTEL_PMC_MAX_GENERIC);
+	BUILD_BUG_ON(AMD64_NUM_COUNTERS_CORE > KVM_AMD_PMC_MAX_GENERIC);
+	BUILD_BUG_ON(KVM_AMD_PMC_MAX_GENERIC > INTEL_PMC_MAX_GENERIC);
 
-	for (i = 0; i < AMD64_NUM_COUNTERS_CORE ; i++) {
+	for (i = 0; i < KVM_AMD_PMC_MAX_GENERIC ; i++) {
 		pmu->gp_counters[i].type = KVM_PMC_GP;
 		pmu->gp_counters[i].vcpu = vcpu;
 		pmu->gp_counters[i].idx = i;
@@ -286,7 +287,7 @@ static void amd_pmu_reset(struct kvm_vcpu *vcpu)
 	struct kvm_pmu *pmu = vcpu_to_pmu(vcpu);
 	int i;
 
-	for (i = 0; i < AMD64_NUM_COUNTERS_CORE; i++) {
+	for (i = 0; i < KVM_AMD_PMC_MAX_GENERIC; i++) {
 		struct kvm_pmc *pmc = &pmu->gp_counters[i];
 
 		pmc_stop_counter(pmc);
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index fd64003ee0e0..1d28d147fc34 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1438,10 +1438,13 @@ static const u32 msrs_to_save_all[] = {
 
 	MSR_K7_EVNTSEL0, MSR_K7_EVNTSEL1, MSR_K7_EVNTSEL2, MSR_K7_EVNTSEL3,
 	MSR_K7_PERFCTR0, MSR_K7_PERFCTR1, MSR_K7_PERFCTR2, MSR_K7_PERFCTR3,
+
+	/* This part of MSRs should match KVM_AMD_PMC_MAX_GENERIC. */
 	MSR_F15H_PERF_CTL0, MSR_F15H_PERF_CTL1, MSR_F15H_PERF_CTL2,
 	MSR_F15H_PERF_CTL3, MSR_F15H_PERF_CTL4, MSR_F15H_PERF_CTL5,
 	MSR_F15H_PERF_CTR0, MSR_F15H_PERF_CTR1, MSR_F15H_PERF_CTR2,
 	MSR_F15H_PERF_CTR3, MSR_F15H_PERF_CTR4, MSR_F15H_PERF_CTR5,
+
 	MSR_IA32_XFD, MSR_IA32_XFD_ERR,
 };
 
-- 
2.37.3