linux-kernel - [RFC PATCH 38/41] KVM: x86/pmu: Introduce PMU helper to increment counter

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Date: Fri, 26 Jan 2024 16:54:41 +0800
From: Xiong Zhang <xiong.y.zhang@...ux.intel.com>
To: seanjc@...gle.com,
	pbonzini@...hat.com,
	peterz@...radead.org,
	mizhang@...gle.com,
	kan.liang@...el.com,
	zhenyuw@...ux.intel.com,
	dapeng1.mi@...ux.intel.com,
	jmattson@...gle.com
Cc: kvm@...r.kernel.org,
	linux-perf-users@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	zhiyuan.lv@...el.com,
	eranian@...gle.com,
	irogers@...gle.com,
	samantha.alt@...el.com,
	like.xu.linux@...il.com,
	chao.gao@...el.com,
	xiong.y.zhang@...ux.intel.com
Subject: [RFC PATCH 38/41] KVM: x86/pmu: Introduce PMU helper to increment counter

From: Mingwei Zhang <mizhang@...gle.com>

Introduce PMU helper to increment counter for passthrough PMU because it is
able to conveniently return the overflow condition instead of deferring the
overflow check to KVM_REQ_PMU in original implementation. In addition, this
helper function can hide architecture details.

Signed-off-by: Mingwei Zhang <mizhang@...gle.com>
---
 arch/x86/include/asm/kvm_host.h |  1 +
 arch/x86/kvm/pmu.c              | 15 +++++++++++++++
 2 files changed, 16 insertions(+)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index b02688ed74f7..869de0d81055 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -501,6 +501,7 @@ struct kvm_pmc {
 	bool is_paused;
 	bool intr;
 	u64 counter;
+	u64 emulated_counter;
 	u64 prev_counter;
 	u64 eventsel;
 	u64 eventsel_hw;
diff --git a/arch/x86/kvm/pmu.c b/arch/x86/kvm/pmu.c
index e7ad97734705..7b0bac1ac4bf 100644
--- a/arch/x86/kvm/pmu.c
+++ b/arch/x86/kvm/pmu.c
@@ -434,6 +434,21 @@ static void reprogram_counter(struct kvm_pmc *pmc)
 	pmc->prev_counter = 0;
 }
 
+static bool kvm_passthrough_pmu_incr_counter(struct kvm_pmc *pmc)
+{
+	if (!pmc->emulated_counter)
+		return false;
+
+	pmc->counter += pmc->emulated_counter;
+	pmc->emulated_counter = 0;
+	pmc->counter &= pmc_bitmask(pmc);
+
+	if (!pmc->counter)
+		return true;
+
+	return false;
+}
+
 void kvm_pmu_handle_event(struct kvm_vcpu *vcpu)
 {
 	struct kvm_pmu *pmu = vcpu_to_pmu(vcpu);
-- 
2.34.1