[PATCH v5 02/12] KVM: arm64: PMU: Set the default PMU for the guest on vCPU reset

[Raghavendra Rao Ananta <rananta@xxxxxxxxxx>]

From: Reiji Watanabe <reijiw@xxxxxxxxxx>

The following patches will use the number of counters information
from the arm_pmu and use this to set the PMCR.N for the guest
during vCPU reset. However, since the guest is not associated
with any arm_pmu until userspace configures the vPMU device
attributes, and a reset can happen before this event, call
kvm_arm_support_pmu_v3() just before doing the reset.

No functional change intended.

Signed-off-by: Reiji Watanabe <reijiw@xxxxxxxxxx>
Signed-off-by: Raghavendra Rao Ananta <rananta@xxxxxxxxxx>
---
 arch/arm64/kvm/pmu-emul.c |  9 +--------
 arch/arm64/kvm/reset.c    | 18 +++++++++++++-----
 include/kvm/arm_pmu.h     |  6 ++++++
 3 files changed, 20 insertions(+), 13 deletions(-)

diff --git a/arch/arm64/kvm/pmu-emul.c b/arch/arm64/kvm/pmu-emul.c
index 0ffd1efa90c07..b87822024828a 100644
--- a/arch/arm64/kvm/pmu-emul.c
+++ b/arch/arm64/kvm/pmu-emul.c
@@ -865,7 +865,7 @@ 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);
 
@@ -937,13 +937,6 @@ 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) {
-		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 bc8556b6f4590..4c20f1ccd0789 100644
--- a/arch/arm64/kvm/reset.c
+++ b/arch/arm64/kvm/reset.c
@@ -206,6 +206,7 @@ static int kvm_vcpu_enable_ptrauth(struct kvm_vcpu *vcpu)
  */
 int kvm_reset_vcpu(struct kvm_vcpu *vcpu)
 {
+	struct kvm *kvm = vcpu->kvm;
 	struct vcpu_reset_state reset_state;
 	int ret;
 	bool loaded;
@@ -216,6 +217,18 @@ int kvm_reset_vcpu(struct kvm_vcpu *vcpu)
 	vcpu->arch.reset_state.reset = false;
 	spin_unlock(&vcpu->arch.mp_state_lock);
 
+	/*
+	 * When the vCPU has a PMU, but no PMU is set for the guest
+	 * yet, set the default one.
+	 */
+	if (kvm_vcpu_has_pmu(vcpu) && unlikely(!kvm->arch.arm_pmu)) {
+		ret = -EINVAL;
+		if (kvm_arm_support_pmu_v3())
+			ret = kvm_arm_set_vm_pmu(kvm, NULL);
+		if (ret)
+			return ret;
+	}
+
 	/* Reset PMU outside of the non-preemptible section */
 	kvm_pmu_vcpu_reset(vcpu);
 
@@ -257,11 +270,6 @@ 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 847da6fc27139..66a2f8477641e 100644
--- a/include/kvm/arm_pmu.h
+++ b/include/kvm/arm_pmu.h
@@ -100,6 +100,7 @@ void kvm_vcpu_pmu_restore_host(struct kvm_vcpu *vcpu);
 })
 
 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 {
@@ -172,6 +173,11 @@ 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 -ENODEV;
+}
+
 #endif
 
 #endif
-- 
2.41.0.694.ge786442a9b-goog