KVM: arm64: Add unified helper for reprogramming counters by mask

Having separate helpers for enabling/disabling counters provides the
wrong abstraction, as the state of each counter needs to be evaluated
independently and, in some cases, use a different global enable bit.

Collapse the enable/disable accessors into a single, common helper that
reconfigures every counter set in @mask, leaving the complexity of
determining if an event is actually enabled in
kvm_pmu_counter_is_enabled().

Reviewed-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20241217175513.3658056-1-oliver.upton@linux.dev
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>

arch/arm64/kvm/pmu-emul.c

@@ -24,6 +24,7 @@ static DEFINE_MUTEX(arm_pmus_lock);
 
 static void kvm_pmu_create_perf_event(struct kvm_pmc *pmc);
 static void kvm_pmu_release_perf_event(struct kvm_pmc *pmc);
+static bool kvm_pmu_counter_is_enabled(struct kvm_pmc *pmc);
 
 static struct kvm_vcpu *kvm_pmc_to_vcpu(const struct kvm_pmc *pmc)
 {
@@ -327,65 +328,44 @@ u64 kvm_pmu_implemented_counter_mask(struct kvm_vcpu *vcpu)
 		return GENMASK(val - 1, 0) | BIT(ARMV8_PMU_CYCLE_IDX);
 }
 
-/**
- * kvm_pmu_enable_counter_mask - enable selected PMU counters
- * @vcpu: The vcpu pointer
- * @val: the value guest writes to PMCNTENSET register
- *
- * Call perf_event_enable to start counting the perf event
- */
-void kvm_pmu_enable_counter_mask(struct kvm_vcpu *vcpu, u64 val)
+static void kvm_pmc_enable_perf_event(struct kvm_pmc *pmc)
 {
-	int i;
-	if (!kvm_vcpu_has_pmu(vcpu))
-		return;
-
-	if (!(kvm_vcpu_read_pmcr(vcpu) & ARMV8_PMU_PMCR_E) || !val)
+	if (!pmc->perf_event) {
+		kvm_pmu_create_perf_event(pmc);
 		return;
+	}
 
-	for (i = 0; i < KVM_ARMV8_PMU_MAX_COUNTERS; i++) {
-		struct kvm_pmc *pmc;
-
-		if (!(val & BIT(i)))
-			continue;
-
-		pmc = kvm_vcpu_idx_to_pmc(vcpu, i);
+	perf_event_enable(pmc->perf_event);
+	if (pmc->perf_event->state != PERF_EVENT_STATE_ACTIVE)
+		kvm_debug("fail to enable perf event\n");
+}
 
-		if (!pmc->perf_event) {
-			kvm_pmu_create_perf_event(pmc);
-		} else {
-			perf_event_enable(pmc->perf_event);
-			if (pmc->perf_event->state != PERF_EVENT_STATE_ACTIVE)
-				kvm_debug("fail to enable perf event\n");
-		}
-	}
+static void kvm_pmc_disable_perf_event(struct kvm_pmc *pmc)
+{
+	if (pmc->perf_event)
+		perf_event_disable(pmc->perf_event);
 }
 
-/**
- * kvm_pmu_disable_counter_mask - disable selected PMU counters
- * @vcpu: The vcpu pointer
- * @val: the value guest writes to PMCNTENCLR register
- *
- * Call perf_event_disable to stop counting the perf event
- */
-void kvm_pmu_disable_counter_mask(struct kvm_vcpu *vcpu, u64 val)
+void kvm_pmu_reprogram_counter_mask(struct kvm_vcpu *vcpu, u64 val)
 {
 	int i;
 
 	if (!kvm_vcpu_has_pmu(vcpu) || !val)
 		return;
 
 	for (i = 0; i < KVM_ARMV8_PMU_MAX_COUNTERS; i++) {
-		struct kvm_pmc *pmc;
+		struct kvm_pmc *pmc = kvm_vcpu_idx_to_pmc(vcpu, i);
 
 		if (!(val & BIT(i)))
 			continue;
 
-		pmc = kvm_vcpu_idx_to_pmc(vcpu, i);
-
-		if (pmc->perf_event)
-			perf_event_disable(pmc->perf_event);
+		if (kvm_pmu_counter_is_enabled(pmc))
+			kvm_pmc_enable_perf_event(pmc);
+		else
+			kvm_pmc_disable_perf_event(pmc);
 	}
+
+	kvm_vcpu_pmu_restore_guest(vcpu);
 }
 
 /*
@@ -630,10 +610,10 @@ void kvm_pmu_handle_pmcr(struct kvm_vcpu *vcpu, u64 val)
 	__vcpu_sys_reg(vcpu, PMCR_EL0) = val & ~(ARMV8_PMU_PMCR_C | ARMV8_PMU_PMCR_P);
 
 	if (val & ARMV8_PMU_PMCR_E) {
-		kvm_pmu_enable_counter_mask(vcpu,
+		kvm_pmu_reprogram_counter_mask(vcpu,
 		       __vcpu_sys_reg(vcpu, PMCNTENSET_EL0));
 	} else {
-		kvm_pmu_disable_counter_mask(vcpu,
+		kvm_pmu_reprogram_counter_mask(vcpu,
 		       __vcpu_sys_reg(vcpu, PMCNTENSET_EL0));
 	}
 

arch/arm64/kvm/sys_regs.c

@@ -1208,16 +1208,14 @@ static bool access_pmcnten(struct kvm_vcpu *vcpu, struct sys_reg_params *p,
 	mask = kvm_pmu_accessible_counter_mask(vcpu);
 	if (p->is_write) {
 		val = p->regval & mask;
-		if (r->Op2 & 0x1) {
+		if (r->Op2 & 0x1)
 			/* accessing PMCNTENSET_EL0 */
 			__vcpu_sys_reg(vcpu, PMCNTENSET_EL0) |= val;
-			kvm_pmu_enable_counter_mask(vcpu, val);
-			kvm_vcpu_pmu_restore_guest(vcpu);
-		} else {
+		else
 			/* accessing PMCNTENCLR_EL0 */
 			__vcpu_sys_reg(vcpu, PMCNTENSET_EL0) &= ~val;
-			kvm_pmu_disable_counter_mask(vcpu, val);
-		}
+
+		kvm_pmu_reprogram_counter_mask(vcpu, val);
 	} else {
 		p->regval = __vcpu_sys_reg(vcpu, PMCNTENSET_EL0);
 	}

include/kvm/arm_pmu.h

@@ -53,8 +53,7 @@ u64 kvm_pmu_get_pmceid(struct kvm_vcpu *vcpu, bool pmceid1);
 void kvm_pmu_vcpu_init(struct kvm_vcpu *vcpu);
 void kvm_pmu_vcpu_reset(struct kvm_vcpu *vcpu);
 void kvm_pmu_vcpu_destroy(struct kvm_vcpu *vcpu);
-void kvm_pmu_disable_counter_mask(struct kvm_vcpu *vcpu, u64 val);
-void kvm_pmu_enable_counter_mask(struct kvm_vcpu *vcpu, u64 val);
+void kvm_pmu_reprogram_counter_mask(struct kvm_vcpu *vcpu, u64 val);
 void kvm_pmu_flush_hwstate(struct kvm_vcpu *vcpu);
 void kvm_pmu_sync_hwstate(struct kvm_vcpu *vcpu);
 bool kvm_pmu_should_notify_user(struct kvm_vcpu *vcpu);
@@ -127,8 +126,7 @@ static inline u64 kvm_pmu_accessible_counter_mask(struct kvm_vcpu *vcpu)
 static inline void kvm_pmu_vcpu_init(struct kvm_vcpu *vcpu) {}
 static inline void kvm_pmu_vcpu_reset(struct kvm_vcpu *vcpu) {}
 static inline void kvm_pmu_vcpu_destroy(struct kvm_vcpu *vcpu) {}
-static inline void kvm_pmu_disable_counter_mask(struct kvm_vcpu *vcpu, u64 val) {}
-static inline void kvm_pmu_enable_counter_mask(struct kvm_vcpu *vcpu, u64 val) {}
+static inline void kvm_pmu_reprogram_counter_mask(struct kvm_vcpu *vcpu, u64 val) {}
 static inline void kvm_pmu_flush_hwstate(struct kvm_vcpu *vcpu) {}
 static inline void kvm_pmu_sync_hwstate(struct kvm_vcpu *vcpu) {}
 static inline bool kvm_pmu_should_notify_user(struct kvm_vcpu *vcpu)