[PATCH v2 2/5] KVM: arm64: PMU: Disallow vPMU on non-uniform PMUVer systems

[Reiji Watanabe]

Disallow userspace from configuring vPMU for guests on systems
where the PMUVer is not uniform across all PEs.
KVM has not been advertising PMUv3 to the guests with vPMU on
such systems anyway, and such systems would be extremely
uncommon and unlikely to even use KVM.

Signed-off-by: Reiji Watanabe <reijiw at google.com>
---
 arch/arm64/kvm/arm.c      |  1 +
 arch/arm64/kvm/pmu-emul.c | 11 ++++++++---
 include/kvm/arm_pmu.h     |  3 +++
 3 files changed, 12 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index 72dc53a75d1c..1d410dea21ac 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -2053,6 +2053,7 @@ static int __init init_subsystems(void)
 		goto out;
 
 	kvm_register_perf_callbacks(NULL);
+	kvm_pmu_init();
 
 out:
 	if (err)
diff --git a/arch/arm64/kvm/pmu-emul.c b/arch/arm64/kvm/pmu-emul.c
index dee83119e112..6fb5c59948a8 100644
--- a/arch/arm64/kvm/pmu-emul.c
+++ b/arch/arm64/kvm/pmu-emul.c
@@ -685,9 +685,6 @@ void kvm_host_pmu_init(struct arm_pmu *pmu)
 	entry->arm_pmu = pmu;
 	list_add_tail(&entry->entry, &arm_pmus);
 
-	if (list_is_singular(&arm_pmus))
-		static_branch_enable(&kvm_arm_pmu_available);
-
 out_unlock:
 	mutex_unlock(&arm_pmus_lock);
 }
@@ -1057,3 +1054,11 @@ u8 kvm_arm_pmu_get_pmuver_limit(void)
 					      ID_AA64DFR0_EL1_PMUVer_V3P5);
 	return FIELD_GET(ARM64_FEATURE_MASK(ID_AA64DFR0_EL1_PMUVer), tmp);
 }
+
+void kvm_pmu_init(void)
+{
+	u8 pmuver = kvm_arm_pmu_get_pmuver_limit();
+
+	if (pmuv3_implemented(pmuver))
+		static_branch_enable(&kvm_arm_pmu_available);
+}
diff --git a/include/kvm/arm_pmu.h b/include/kvm/arm_pmu.h
index 847da6fc2713..9cf50e16305a 100644
--- a/include/kvm/arm_pmu.h
+++ b/include/kvm/arm_pmu.h
@@ -74,6 +74,7 @@ int kvm_arm_pmu_v3_enable(struct kvm_vcpu *vcpu);
 struct kvm_pmu_events *kvm_get_pmu_events(void);
 void kvm_vcpu_pmu_restore_guest(struct kvm_vcpu *vcpu);
 void kvm_vcpu_pmu_restore_host(struct kvm_vcpu *vcpu);
+void kvm_pmu_init(void);
 
 #define kvm_vcpu_has_pmu(vcpu)					\
 	(test_bit(KVM_ARM_VCPU_PMU_V3, (vcpu)->arch.features))
@@ -110,6 +111,8 @@ static inline bool kvm_arm_support_pmu_v3(void)
 	return false;
 }
 
+static inline void kvm_pmu_init(void) {};
+
 #define kvm_arm_pmu_irq_initialized(v)	(false)
 static inline u64 kvm_pmu_get_counter_value(struct kvm_vcpu *vcpu,
 					    u64 select_idx)
-- 
2.41.0.585.gd2178a4bd4-goog