executor: arm64: Init PMUs if enabling the feature

KVM requires initializing PMUs (via KVM_SET_DEVICE_ATTR) if the PMU
feature is enabled in a VCPU (via KVM_ARM_VCPU_INIT). This fix ensures
that whenever we enable the PMU feature, we also initialize PMUs.

Author: marpom

executor/common_kvm_arm64.h

@@ -177,6 +177,7 @@ static void install_user_code(int cpufd, void* user_text_slot, int cpu_id, const
 static void setup_cpu_with_opts(int vmfd, int cpufd, const struct kvm_opt* opt, int opt_count)
 {
 	uint32 features = 0;
+        const uint32 pmu_bit = (1 << KVM_ARM_VCPU_PMU_V3);
 	if (opt_count > 1)
 		opt_count = 1;
 	for (int i = 0; i < opt_count; i++) {
@@ -195,6 +196,14 @@ static void setup_cpu_with_opts(int vmfd, int cpufd, const struct kvm_opt* opt,
 	init.features[0] = features;
 	// Use the modified struct kvm_vcpu_init to initialize the virtual CPU.
 	ioctl(cpufd, KVM_ARM_VCPU_INIT, &init);
+        // Make sure that PMUs are initialized if enabled
+        if (opt_count == 1 && (features & pmu_bit)) {
+                struct kvm_device_attr attrs = {
+                    .group = KVM_ARM_VCPU_PMU_V3_CTRL,
+                    .attr = KVM_ARM_VCPU_PMU_V3_INIT
+                };
+                ioctl(cpufd, KVM_SET_DEVICE_ATTR, &attrs);
+        }
 }
 
 #endif