KVM: arm64: Disable PMU support in protected mode

The host currently writes directly in EL2 per-CPU data sections from
the PMU code when running in nVHE. In preparation for unmapping the EL2
sections from the host stage 2, disable PMU support in protected mode as
we currently do not have a use-case for it.
Acked-by: Will Deacon <will@kernel.org>
Signed-off-by: Quentin Perret <qperret@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20210319100146.1149909-38-qperret@google.com

arch/arm64/kvm/perf.c

@@ -55,7 +55,8 @@ int kvm_perf_init(void)
 	 * hardware performance counters. This could ensure the presence of
 	 * a physical PMU and CONFIG_PERF_EVENT is selected.
 	 */
-	if (IS_ENABLED(CONFIG_ARM_PMU) && perf_num_counters() > 0)
+	if (IS_ENABLED(CONFIG_ARM_PMU) && perf_num_counters() > 0
+				       && !is_protected_kvm_enabled())
 		static_branch_enable(&kvm_arm_pmu_available);
 
 	return perf_register_guest_info_callbacks(&kvm_guest_cbs);

arch/arm64/kvm/pmu.c

@@ -33,7 +33,7 @@ void kvm_set_pmu_events(u32 set, struct perf_event_attr *attr)
 {
 	struct kvm_host_data *ctx = this_cpu_ptr_hyp_sym(kvm_host_data);
 
-	if (!ctx || !kvm_pmu_switch_needed(attr))
+	if (!kvm_arm_support_pmu_v3() || !ctx || !kvm_pmu_switch_needed(attr))
 		return;
 
 	if (!attr->exclude_host)
@@ -49,7 +49,7 @@ void kvm_clr_pmu_events(u32 clr)
 {
 	struct kvm_host_data *ctx = this_cpu_ptr_hyp_sym(kvm_host_data);
 
-	if (!ctx)
+	if (!kvm_arm_support_pmu_v3() || !ctx)
 		return;
 
 	ctx->pmu_events.events_host &= ~clr;
@@ -172,7 +172,7 @@ void kvm_vcpu_pmu_restore_guest(struct kvm_vcpu *vcpu)
 	struct kvm_host_data *host;
 	u32 events_guest, events_host;
 
-	if (!has_vhe())
+	if (!kvm_arm_support_pmu_v3() || !has_vhe())
 		return;
 
 	preempt_disable();
@@ -193,7 +193,7 @@ void kvm_vcpu_pmu_restore_host(struct kvm_vcpu *vcpu)
 	struct kvm_host_data *host;
 	u32 events_guest, events_host;
 
-	if (!has_vhe())
+	if (!kvm_arm_support_pmu_v3() || !has_vhe())
 		return;
 
 	host = this_cpu_ptr_hyp_sym(kvm_host_data);