KVM: arm64: Let kvm_vcpu_read_pmcr() return an EL-dependent value for PMCR_EL0.N

Marc Zyngier · Marc Zyngier · commit 600f6fa5c90c · 2025-04-11T13:08:24.000+01:00
When EL2 is present, PMCR_EL0.N is the effective value of MDCR_EL2.HPMN
when accessed from EL1 or EL0.

Make sure we honor this requirement.

Reviewed-by: Oliver Upton &lt;oliver.upton@linux.dev&gt;
Signed-off-by: Marc Zyngier &lt;maz@kernel.org&gt;
diff --git a/arch/arm64/kvm/pmu-emul.c b/arch/arm64/kvm/pmu-emul.c
@@ -1300,8 +1300,12 @@ u8 kvm_arm_pmu_get_pmuver_limit(void)
 u64 kvm_vcpu_read_pmcr(struct kvm_vcpu *vcpu)
 {
 	u64 pmcr = __vcpu_sys_reg(vcpu, PMCR_EL0);
+	u64 n = vcpu->kvm->arch.nr_pmu_counters;
 
-	return u64_replace_bits(pmcr, vcpu->kvm->arch.nr_pmu_counters, ARMV8_PMU_PMCR_N);
+	if (vcpu_has_nv(vcpu) && !vcpu_is_el2(vcpu))
+		n = FIELD_GET(MDCR_EL2_HPMN, __vcpu_sys_reg(vcpu, MDCR_EL2));
+
+	return u64_replace_bits(pmcr, n, ARMV8_PMU_PMCR_N);
 }
 
 void kvm_pmu_nested_transition(struct kvm_vcpu *vcpu)

Original file line number	Diff line number	Diff line change
`@@ -1300,8 +1300,12 @@ u8 kvm_arm_pmu_get_pmuver_limit(void)`
`1300`	`1300`	`u64 kvm_vcpu_read_pmcr(struct kvm_vcpu *vcpu)`
`1301`	`1301`	`{`
`1302`	`1302`	`u64 pmcr = __vcpu_sys_reg(vcpu, PMCR_EL0);`
	`1303`	`+ u64 n = vcpu->kvm->arch.nr_pmu_counters;`
`1303`	`1304`
`1304`		`- return u64_replace_bits(pmcr, vcpu->kvm->arch.nr_pmu_counters, ARMV8_PMU_PMCR_N);`
	`1305`	`+ if (vcpu_has_nv(vcpu) && !vcpu_is_el2(vcpu))`
	`1306`	`+ n = FIELD_GET(MDCR_EL2_HPMN, __vcpu_sys_reg(vcpu, MDCR_EL2));`
	`1307`	`+`
	`1308`	`+ return u64_replace_bits(pmcr, n, ARMV8_PMU_PMCR_N);`
`1305`	`1309`	`}`
`1306`	`1310`
`1307`	`1311`	`void kvm_pmu_nested_transition(struct kvm_vcpu *vcpu)`