[PATCH 2/4] KVM: arm64: PMU: Set the default PMU for the guest on vCPU reset

[Reiji Watanabe <reijiw@google.com>]

Set the default PMU for the guest on the first vCPU reset,
not when userspace initially uses KVM_ARM_VCPU_PMU_V3_CTRL.
The following patches will use the PMUVer of the PMU as the
default value of the ID_AA64DFR0_EL1.PMUVer for vCPUs with
PMU configured.

Signed-off-by: Reiji Watanabe <reijiw@google.com>
---
 arch/arm64/kvm/pmu-emul.c | 10 +---------
 arch/arm64/kvm/reset.c    | 20 +++++++++++++-------
 include/kvm/arm_pmu.h     |  6 ++++++
 3 files changed, 20 insertions(+), 16 deletions(-)

diff --git a/arch/arm64/kvm/pmu-emul.c b/arch/arm64/kvm/pmu-emul.c
index d50c8f7a2410..0194a94c4bae 100644
--- a/arch/arm64/kvm/pmu-emul.c
+++ b/arch/arm64/kvm/pmu-emul.c
@@ -869,7 +869,7 @@ static bool pmu_irq_is_valid(struct kvm *kvm, int irq)
 	return true;
 }
 
-static int kvm_arm_set_vm_pmu(struct kvm *kvm, struct arm_pmu *arm_pmu)
+int kvm_arm_set_vm_pmu(struct kvm *kvm, struct arm_pmu *arm_pmu)
 {
 	lockdep_assert_held(&kvm->arch.config_lock);
 
@@ -926,14 +926,6 @@ int kvm_arm_pmu_v3_set_attr(struct kvm_vcpu *vcpu, struct kvm_device_attr *attr)
 	if (vcpu->arch.pmu.created)
 		return -EBUSY;
 
-	if (!kvm->arch.arm_pmu) {
-		/* No PMU set, get the default one */
-		int ret = kvm_arm_set_vm_pmu(kvm, NULL);
-
-		if (ret)
-			return ret;
-	}
-
 	switch (attr->attr) {
 	case KVM_ARM_VCPU_PMU_V3_IRQ: {
 		int __user *uaddr = (int __user *)(long)attr->addr;
diff --git a/arch/arm64/kvm/reset.c b/arch/arm64/kvm/reset.c
index b5dee8e57e77..f5e24492926c 100644
--- a/arch/arm64/kvm/reset.c
+++ b/arch/arm64/kvm/reset.c
@@ -258,13 +258,24 @@ static int kvm_set_vm_width(struct kvm_vcpu *vcpu)
 int kvm_reset_vcpu(struct kvm_vcpu *vcpu)
 {
 	struct vcpu_reset_state reset_state;
+	struct kvm *kvm = vcpu->kvm;
 	int ret;
 	bool loaded;
 	u32 pstate;
 
-	mutex_lock(&vcpu->kvm->arch.config_lock);
+	mutex_lock(&kvm->arch.config_lock);
 	ret = kvm_set_vm_width(vcpu);
-	mutex_unlock(&vcpu->kvm->arch.config_lock);
+	if (!ret && kvm_vcpu_has_pmu(vcpu)) {
+		if (!kvm_arm_support_pmu_v3())
+			ret = -EINVAL;
+		else if (unlikely(!kvm->arch.arm_pmu))
+			/*
+			 * As no PMU is set for the guest yet,
+			 * set the default one.
+			 */
+			ret = kvm_arm_set_vm_pmu(kvm, NULL);
+	}
+	mutex_unlock(&kvm->arch.config_lock);
 
 	if (ret)
 		return ret;
@@ -315,11 +326,6 @@ int kvm_reset_vcpu(struct kvm_vcpu *vcpu)
 		} else {
 			pstate = VCPU_RESET_PSTATE_EL1;
 		}
-
-		if (kvm_vcpu_has_pmu(vcpu) && !kvm_arm_support_pmu_v3()) {
-			ret = -EINVAL;
-			goto out;
-		}
 		break;
 	}
 
diff --git a/include/kvm/arm_pmu.h b/include/kvm/arm_pmu.h
index 1a6a695ca67a..5ece2a3c1858 100644
--- a/include/kvm/arm_pmu.h
+++ b/include/kvm/arm_pmu.h
@@ -96,6 +96,7 @@ void kvm_vcpu_pmu_restore_host(struct kvm_vcpu *vcpu);
 	(vcpu->kvm->arch.dfr0_pmuver.imp >= ID_AA64DFR0_EL1_PMUVer_V3P5)
 
 u8 kvm_arm_pmu_get_pmuver_limit(void);
+int kvm_arm_set_vm_pmu(struct kvm *kvm, struct arm_pmu *arm_pmu);
 
 #else
 struct kvm_pmu {
@@ -168,6 +169,11 @@ static inline u8 kvm_arm_pmu_get_pmuver_limit(void)
 	return 0;
 }
 
+static inline int kvm_arm_set_vm_pmu(struct kvm *kvm, struct arm_pmu *arm_pmu)
+{
+	return 0;
+}
+
 #endif
 
 #endif
-- 
2.41.0.rc0.172.g3f132b7071-goog