+/*
+ * Make sure that a cpu that is being hot-unplugged does not have any vcpus
+ * cached on it.
+ */
+static void decache_vcpus_on_cpu(int cpu)
+{
+ struct kvm *vm;
+ struct kvm_vcpu *vcpu;
+ int i;
+
+ spin_lock(&kvm_lock);
+ list_for_each_entry(vm, &vm_list, vm_list)
+ for (i = 0; i < KVM_MAX_VCPUS; ++i) {
+ vcpu = &vm->vcpus[i];
+ /*
+ * If the vcpu is locked, then it is running on some
+ * other cpu and therefore it is not cached on the
+ * cpu in question.
+ *
+ * If it's not locked, check the last cpu it executed
+ * on.
+ */
+ if (mutex_trylock(&vcpu->mutex)) {
+ if (vcpu->cpu == cpu) {
+ kvm_arch_ops->vcpu_decache(vcpu);
+ vcpu->cpu = -1;
+ }
+ mutex_unlock(&vcpu->mutex);
+ }
+ }
+ spin_unlock(&kvm_lock);
+}
+
+static int kvm_cpu_hotplug(struct notifier_block *notifier, unsigned long val,
+ void *v)
+{
+ int cpu = (long)v;
+
+ switch (val) {
+ case CPU_DEAD:
+ case CPU_UP_CANCELED:
+ decache_vcpus_on_cpu(cpu);
+ smp_call_function_single(cpu, kvm_arch_ops->hardware_disable,
+ NULL, 0, 1);
+ break;
+ case CPU_UP_PREPARE:
+ smp_call_function_single(cpu, kvm_arch_ops->hardware_enable,
+ NULL, 0, 1);
+ break;
+ }
+ return NOTIFY_OK;
+}
+
+static struct notifier_block kvm_cpu_notifier = {
+ .notifier_call = kvm_cpu_hotplug,
+ .priority = 20, /* must be > scheduler priority */
+};
+