arm64: KVM: Add access handler for PMCNTENSET and PMCNTENCLR register

Since the reset value of PMCNTENSET and PMCNTENCLR is UNKNOWN, use
reset_unknown for its reset handler. Add a handler to emulate writing
PMCNTENSET or PMCNTENCLR register.

When writing to PMCNTENSET, call perf_event_enable to enable the perf
event. When writing to PMCNTENCLR, call perf_event_disable to disable
the perf event.

Signed-off-by: Shannon Zhao <shannon.zhao@linaro.org>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>

arch/arm64/include/asm/kvm_host.h

@@ -123,6 +123,7 @@ enum vcpu_sysreg {
 	PMEVCNTR0_EL0,	/* Event Counter Register (0-30) */
 	PMEVCNTR30_EL0 = PMEVCNTR0_EL0 + 30,
 	PMCCNTR_EL0,	/* Cycle Counter Register */
+	PMCNTENSET_EL0,	/* Count Enable Set Register */
 
 	/* 32bit specific registers. Keep them at the end of the range */
 	DACR32_EL2,	/* Domain Access Control Register */

arch/arm64/kvm/sys_regs.c

@@ -563,6 +563,33 @@ static bool access_pmu_evcntr(struct kvm_vcpu *vcpu,
 	return true;
 }
 
+static bool access_pmcnten(struct kvm_vcpu *vcpu, struct sys_reg_params *p,
+			   const struct sys_reg_desc *r)
+{
+	u64 val, mask;
+
+	if (!kvm_arm_pmu_v3_ready(vcpu))
+		return trap_raz_wi(vcpu, p, r);
+
+	mask = kvm_pmu_valid_counter_mask(vcpu);
+	if (p->is_write) {
+		val = p->regval & mask;
+		if (r->Op2 & 0x1) {
+			/* accessing PMCNTENSET_EL0 */
+			vcpu_sys_reg(vcpu, PMCNTENSET_EL0) |= val;
+			kvm_pmu_enable_counter(vcpu, val);
+		} else {
+			/* accessing PMCNTENCLR_EL0 */
+			vcpu_sys_reg(vcpu, PMCNTENSET_EL0) &= ~val;
+			kvm_pmu_disable_counter(vcpu, val);
+		}
+	} else {
+		p->regval = vcpu_sys_reg(vcpu, PMCNTENSET_EL0) & mask;
+	}
+
+	return true;
+}
+
 /* Silly macro to expand the DBG{BCR,BVR,WVR,WCR}n_EL1 registers in one go */
 #define DBG_BCR_BVR_WCR_WVR_EL1(n)					\
 	/* DBGBVRn_EL1 */						\
@@ -757,10 +784,10 @@ static const struct sys_reg_desc sys_reg_descs[] = {
 	  access_pmcr, reset_pmcr, },
 	/* PMCNTENSET_EL0 */
 	{ Op0(0b11), Op1(0b011), CRn(0b1001), CRm(0b1100), Op2(0b001),
-	  trap_raz_wi },
+	  access_pmcnten, reset_unknown, PMCNTENSET_EL0 },
 	/* PMCNTENCLR_EL0 */
 	{ Op0(0b11), Op1(0b011), CRn(0b1001), CRm(0b1100), Op2(0b010),
-	  trap_raz_wi },
+	  access_pmcnten, NULL, PMCNTENSET_EL0 },
 	/* PMOVSCLR_EL0 */
 	{ Op0(0b11), Op1(0b011), CRn(0b1001), CRm(0b1100), Op2(0b011),
 	  trap_raz_wi },
@@ -1057,8 +1084,8 @@ static const struct sys_reg_desc cp15_regs[] = {
 
 	/* PMU */
 	{ Op1( 0), CRn( 9), CRm(12), Op2( 0), access_pmcr },
-	{ Op1( 0), CRn( 9), CRm(12), Op2( 1), trap_raz_wi },
-	{ Op1( 0), CRn( 9), CRm(12), Op2( 2), trap_raz_wi },
+	{ Op1( 0), CRn( 9), CRm(12), Op2( 1), access_pmcnten },
+	{ Op1( 0), CRn( 9), CRm(12), Op2( 2), access_pmcnten },
 	{ Op1( 0), CRn( 9), CRm(12), Op2( 3), trap_raz_wi },
 	{ Op1( 0), CRn( 9), CRm(12), Op2( 5), access_pmselr },
 	{ Op1( 0), CRn( 9), CRm(12), Op2( 6), access_pmceid },

include/kvm/arm_pmu.h

@@ -40,6 +40,9 @@ struct kvm_pmu {
 #define kvm_arm_pmu_v3_ready(v)		((v)->arch.pmu.ready)
 u64 kvm_pmu_get_counter_value(struct kvm_vcpu *vcpu, u64 select_idx);
 void kvm_pmu_set_counter_value(struct kvm_vcpu *vcpu, u64 select_idx, u64 val);
+u64 kvm_pmu_valid_counter_mask(struct kvm_vcpu *vcpu);
+void kvm_pmu_disable_counter(struct kvm_vcpu *vcpu, u64 val);
+void kvm_pmu_enable_counter(struct kvm_vcpu *vcpu, u64 val);
 #else
 struct kvm_pmu {
 };
@@ -52,6 +55,12 @@ static inline u64 kvm_pmu_get_counter_value(struct kvm_vcpu *vcpu,
 }
 static inline void kvm_pmu_set_counter_value(struct kvm_vcpu *vcpu,
 					     u64 select_idx, u64 val) {}
+static inline u64 kvm_pmu_valid_counter_mask(struct kvm_vcpu *vcpu)
+{
+	return 0;
+}
+static inline void kvm_pmu_disable_counter(struct kvm_vcpu *vcpu, u64 val) {}
+static inline void kvm_pmu_enable_counter(struct kvm_vcpu *vcpu, u64 val) {}
 #endif
 
 #endif

virt/kvm/arm/pmu.c

@@ -61,3 +61,69 @@ void kvm_pmu_set_counter_value(struct kvm_vcpu *vcpu, u64 select_idx, u64 val)
 	      ? PMCCNTR_EL0 : PMEVCNTR0_EL0 + select_idx;
 	vcpu_sys_reg(vcpu, reg) += (s64)val - kvm_pmu_get_counter_value(vcpu, select_idx);
 }
+
+u64 kvm_pmu_valid_counter_mask(struct kvm_vcpu *vcpu)
+{
+	u64 val = vcpu_sys_reg(vcpu, PMCR_EL0) >> ARMV8_PMU_PMCR_N_SHIFT;
+
+	val &= ARMV8_PMU_PMCR_N_MASK;
+	if (val == 0)
+		return BIT(ARMV8_PMU_CYCLE_IDX);
+	else
+		return GENMASK(val - 1, 0) | BIT(ARMV8_PMU_CYCLE_IDX);
+}
+
+/**
+ * kvm_pmu_enable_counter - enable selected PMU counter
+ * @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(struct kvm_vcpu *vcpu, u64 val)
+{
+	int i;
+	struct kvm_pmu *pmu = &vcpu->arch.pmu;
+	struct kvm_pmc *pmc;
+
+	if (!(vcpu_sys_reg(vcpu, PMCR_EL0) & ARMV8_PMU_PMCR_E) || !val)
+		return;
+
+	for (i = 0; i < ARMV8_PMU_MAX_COUNTERS; i++) {
+		if (!(val & BIT(i)))
+			continue;
+
+		pmc = &pmu->pmc[i];
+		if (pmc->perf_event) {
+			perf_event_enable(pmc->perf_event);
+			if (pmc->perf_event->state != PERF_EVENT_STATE_ACTIVE)
+				kvm_debug("fail to enable perf event\n");
+		}
+	}
+}
+
+/**
+ * kvm_pmu_disable_counter - disable selected PMU counter
+ * @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(struct kvm_vcpu *vcpu, u64 val)
+{
+	int i;
+	struct kvm_pmu *pmu = &vcpu->arch.pmu;
+	struct kvm_pmc *pmc;
+
+	if (!val)
+		return;
+
+	for (i = 0; i < ARMV8_PMU_MAX_COUNTERS; i++) {
+		if (!(val & BIT(i)))
+			continue;
+
+		pmc = &pmu->pmc[i];
+		if (pmc->perf_event)
+			perf_event_disable(pmc->perf_event);
+	}
+}