linux-kernel - [PATCH 1/3] KVM: x86/pmu: Add fast-path check for per-vm vPMU disablility

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Date:   Tue, 10 May 2022 19:57:16 +0800
From:   Like Xu <like.xu.linux@...il.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     Jim Mattson <jmattson@...gle.com>, sandipan.das@....com,
        Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH 1/3] KVM: x86/pmu: Add fast-path check for per-vm vPMU disablility

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

Since vcpu->kvm->arch.enable_pmu is introduced in a generic way,
it makes more sense to move the relevant checks to generic code rather
than scattering usages around, thus saving cpu cycles from static_call()
when vPMU is disabled.

Signed-off-by: Like Xu <likexu@...cent.com>
---
 arch/x86/kvm/pmu.c           | 6 ++++++
 arch/x86/kvm/svm/pmu.c       | 3 ---
 arch/x86/kvm/vmx/pmu_intel.c | 2 +-
 3 files changed, 7 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kvm/pmu.c b/arch/x86/kvm/pmu.c
index 618f529f1c4d..522498945a4a 100644
--- a/arch/x86/kvm/pmu.c
+++ b/arch/x86/kvm/pmu.c
@@ -415,6 +415,9 @@ void kvm_pmu_deliver_pmi(struct kvm_vcpu *vcpu)
 
 bool kvm_pmu_is_valid_msr(struct kvm_vcpu *vcpu, u32 msr)
 {
+	if (!vcpu->kvm->arch.enable_pmu)
+		return false;
+
 	return static_call(kvm_x86_pmu_msr_idx_to_pmc)(vcpu, msr) ||
 		static_call(kvm_x86_pmu_is_valid_msr)(vcpu, msr);
 }
@@ -445,6 +448,9 @@ int kvm_pmu_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
  */
 void kvm_pmu_refresh(struct kvm_vcpu *vcpu)
 {
+	if (!vcpu->kvm->arch.enable_pmu)
+		return;
+
 	static_call(kvm_x86_pmu_refresh)(vcpu);
 }
 
diff --git a/arch/x86/kvm/svm/pmu.c b/arch/x86/kvm/svm/pmu.c
index 57ab4739eb19..68b9e22c84d2 100644
--- a/arch/x86/kvm/svm/pmu.c
+++ b/arch/x86/kvm/svm/pmu.c
@@ -101,9 +101,6 @@ static inline struct kvm_pmc *get_gp_pmc_amd(struct kvm_pmu *pmu, u32 msr,
 {
 	struct kvm_vcpu *vcpu = pmu_to_vcpu(pmu);
 
-	if (!vcpu->kvm->arch.enable_pmu)
-		return NULL;
-
 	switch (msr) {
 	case MSR_F15H_PERF_CTL0:
 	case MSR_F15H_PERF_CTL1:
diff --git a/arch/x86/kvm/vmx/pmu_intel.c b/arch/x86/kvm/vmx/pmu_intel.c
index 9db662399487..3f15ec2dd4b3 100644
--- a/arch/x86/kvm/vmx/pmu_intel.c
+++ b/arch/x86/kvm/vmx/pmu_intel.c
@@ -493,7 +493,7 @@ static void intel_pmu_refresh(struct kvm_vcpu *vcpu)
 	pmu->raw_event_mask = X86_RAW_EVENT_MASK;
 
 	entry = kvm_find_cpuid_entry(vcpu, 0xa, 0);
-	if (!entry || !vcpu->kvm->arch.enable_pmu)
+	if (!entry)
 		return;
 	eax.full = entry->eax;
 	edx.full = entry->edx;
-- 
2.36.1