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From:   Like Xu <like.xu.linux@gmail.com>
To:     Sean Christopherson <seanjc@google.com>,
        Paolo Bonzini <pbonzini@redhat.com>
Cc:     kvm@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH v3 3/8] KVM: x86/pmu: Rewrite reprogram_counters() to improve performance
Date:   Fri, 11 Nov 2022 18:26:40 +0800
Message-Id: <20221111102645.82001-4-likexu@tencent.com>
In-Reply-To: <20221111102645.82001-1-likexu@tencent.com>
References: <20221111102645.82001-1-likexu@tencent.com>
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From: Like Xu <likexu@tencent.com>

A valid pmc is always tested before using pmu->reprogram_pmi. Eliminate
this part of the redundancy by setting the counter's bitmask directly,
and in addition, trigger KVM_REQ_PMU only once to save more cpu cycles.

Signed-off-by: Like Xu <likexu@tencent.com>
---
 arch/x86/kvm/pmu.h           | 11 +++++++++++
 arch/x86/kvm/vmx/pmu_intel.c | 12 ------------
 2 files changed, 11 insertions(+), 12 deletions(-)

diff --git a/arch/x86/kvm/pmu.h b/arch/x86/kvm/pmu.h
index 2b5376ba66ea..be552c8217a0 100644
--- a/arch/x86/kvm/pmu.h
+++ b/arch/x86/kvm/pmu.h
@@ -189,6 +189,17 @@ static inline void kvm_pmu_request_counter_reprogam(struct kvm_pmc *pmc)
 	kvm_make_request(KVM_REQ_PMU, pmc->vcpu);
 }
 
+static inline void reprogram_counters(struct kvm_pmu *pmu, u64 diff)
+{
+	int bit;
+
+	if (diff) {
+		for_each_set_bit(bit, (unsigned long *)&diff, X86_PMC_IDX_MAX)
+			__set_bit(bit, pmu->reprogram_pmi);
+		kvm_make_request(KVM_REQ_PMU, pmu_to_vcpu(pmu));
+	}
+}
+
 void kvm_pmu_deliver_pmi(struct kvm_vcpu *vcpu);
 void kvm_pmu_handle_event(struct kvm_vcpu *vcpu);
 int kvm_pmu_rdpmc(struct kvm_vcpu *vcpu, unsigned pmc, u64 *data);
diff --git a/arch/x86/kvm/vmx/pmu_intel.c b/arch/x86/kvm/vmx/pmu_intel.c
index 2f7cd388859c..db704eea2d7c 100644
--- a/arch/x86/kvm/vmx/pmu_intel.c
+++ b/arch/x86/kvm/vmx/pmu_intel.c
@@ -68,18 +68,6 @@ static struct kvm_pmc *intel_pmc_idx_to_pmc(struct kvm_pmu *pmu, int pmc_idx)
 	}
 }
 
-static void reprogram_counters(struct kvm_pmu *pmu, u64 diff)
-{
-	int bit;
-	struct kvm_pmc *pmc;
-
-	for_each_set_bit(bit, (unsigned long *)&diff, X86_PMC_IDX_MAX) {
-		pmc = intel_pmc_idx_to_pmc(pmu, bit);
-		if (pmc)
-			kvm_pmu_request_counter_reprogam(pmc);
-	}
-}
-
 static bool intel_hw_event_available(struct kvm_pmc *pmc)
 {
 	struct kvm_pmu *pmu = pmc_to_pmu(pmc);
-- 
2.38.1