linux-kernel - [PATCH 1/3] KVM: x86: Omit PMU MSRs from KVM_GET_MSR_INDEX_LIST if !enable

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Date:   Mon, 26 Dec 2022 19:17:08 +0800
From:   Like Xu <like.xu.linux@...il.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     Sean Christopherson <seanjc@...gle.com>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, Aaron Lewis <aaronlewis@...gle.com>
Subject: [PATCH 1/3] KVM: x86: Omit PMU MSRs from KVM_GET_MSR_INDEX_LIST if !enable_pmu

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

When the PMU is disabled, don't bother sharing the PMU MSRs with
userspace through KVM_GET_MSR_INDEX_LIST.  Instead, filter them out
so userspace doesn't have to keep track of them.

Note that 'enable_pmu' is read-only, so userspace has no control over
whether the PMU MSRs are included in the list or not.

Suggested-by: Sean Christopherson <seanjc@...gle.com>
Co-developed-by: Aaron Lewis <aaronlewis@...gle.com>
Signed-off-by: Aaron Lewis <aaronlewis@...gle.com>
Signed-off-by: Like Xu <likexu@...cent.com>
---
 arch/x86/include/asm/kvm_host.h |  1 +
 arch/x86/kvm/x86.c              | 22 ++++++++++++++++++++--
 2 files changed, 21 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index f35f1ff4427b..2ed710b393eb 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -514,6 +514,7 @@ 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 MSR_ARCH_PERFMON_FIXED_CTR_MAX	(MSR_ARCH_PERFMON_FIXED_CTR0 + KVM_PMC_MAX_FIXED - 1)
 #define KVM_AMD_PMC_MAX_GENERIC	6
 struct kvm_pmu {
 	unsigned nr_arch_gp_counters;
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 5c3ce39cdccb..f570367463c8 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -7054,15 +7054,32 @@ static void kvm_init_msr_list(void)
 				continue;
 			break;
 		case MSR_ARCH_PERFMON_PERFCTR0 ... MSR_ARCH_PERFMON_PERFCTR_MAX:
-			if (msrs_to_save_all[i] - MSR_ARCH_PERFMON_PERFCTR0 >=
+			if (!enable_pmu || msrs_to_save_all[i] - MSR_ARCH_PERFMON_PERFCTR0 >=
 			    min(KVM_INTEL_PMC_MAX_GENERIC, kvm_pmu_cap.num_counters_gp))
 				continue;
 			break;
 		case MSR_ARCH_PERFMON_EVENTSEL0 ... MSR_ARCH_PERFMON_EVENTSEL_MAX:
-			if (msrs_to_save_all[i] - MSR_ARCH_PERFMON_EVENTSEL0 >=
+			if (!enable_pmu || msrs_to_save_all[i] - MSR_ARCH_PERFMON_EVENTSEL0 >=
 			    min(KVM_INTEL_PMC_MAX_GENERIC, kvm_pmu_cap.num_counters_gp))
 				continue;
 			break;
+		case MSR_ARCH_PERFMON_FIXED_CTR0 ... MSR_ARCH_PERFMON_FIXED_CTR_MAX:
+			if (!enable_pmu || msrs_to_save_all[i] - MSR_ARCH_PERFMON_FIXED_CTR0 >=
+			    min(KVM_PMC_MAX_FIXED, kvm_pmu_cap.num_counters_fixed))
+				continue;
+			break;
+		case MSR_F15H_PERF_CTL0 ... MSR_F15H_PERF_CTR5:
+		case MSR_K7_EVNTSEL0 ... MSR_K7_PERFCTR3:
+		case MSR_CORE_PERF_FIXED_CTR_CTRL:
+		case MSR_CORE_PERF_GLOBAL_STATUS:
+		case MSR_CORE_PERF_GLOBAL_CTRL:
+		case MSR_CORE_PERF_GLOBAL_OVF_CTRL:
+		case MSR_IA32_DS_AREA:
+		case MSR_IA32_PEBS_ENABLE:
+		case MSR_PEBS_DATA_CFG:
+			if (!enable_pmu)
+				continue;
+			break;
 		case MSR_IA32_XFD:
 		case MSR_IA32_XFD_ERR:
 			if (!kvm_cpu_cap_has(X86_FEATURE_XFD))
@@ -13468,3 +13485,4 @@ static void __exit kvm_x86_exit(void)
 	 */
 }
 module_exit(kvm_x86_exit);
+
-- 
2.39.0