linux-kernel - [PATCH v4 03/12] KVM: x86/pmu: Rewrite reprogram

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Message-Id: <20230214050757.9623-4-likexu@tencent.com>
Date:   Tue, 14 Feb 2023 13:07:48 +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
Subject: [PATCH v4 03/12] KVM: x86/pmu: Rewrite reprogram_counters() to improve performance

From: Like Xu <likexu@...cent.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@...cent.com>
---
 arch/x86/kvm/vmx/pmu_intel.c | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/arch/x86/kvm/vmx/pmu_intel.c b/arch/x86/kvm/vmx/pmu_intel.c
index 6a2f8b4ed061..069e1aae418c 100644
--- a/arch/x86/kvm/vmx/pmu_intel.c
+++ b/arch/x86/kvm/vmx/pmu_intel.c
@@ -73,16 +73,16 @@ 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)
+static inline 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);
-	}
+	if (!diff)
+		return;
+
+	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));
 }
 
 static bool intel_hw_event_available(struct kvm_pmc *pmc)
-- 
2.39.1