KVM: PPC: Book3S HV: kvmppc_host_rm_ops - handle offlining CPUs

The kvmppc_host_rm_ops structure keeps track of which cores are
are in the host by maintaining a bitmask of active/runnable
online CPUs that have not entered the guest. This patch adds
support to manage the bitmask when a CPU is offlined or onlined
in the host.
Signed-off-by: Suresh Warrier <warrier@linux.vnet.ibm.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>

arch/powerpc/kvm/book3s_hv.c

@@ -3053,6 +3053,36 @@ static int kvmppc_hv_setup_htab_rma(struct kvm_vcpu *vcpu)
 }
 
 #ifdef CONFIG_KVM_XICS
+static int kvmppc_cpu_notify(struct notifier_block *self, unsigned long action,
+			void *hcpu)
+{
+	unsigned long cpu = (long)hcpu;
+
+	switch (action) {
+	case CPU_UP_PREPARE:
+	case CPU_UP_PREPARE_FROZEN:
+		kvmppc_set_host_core(cpu);
+		break;
+
+#ifdef CONFIG_HOTPLUG_CPU
+	case CPU_DEAD:
+	case CPU_DEAD_FROZEN:
+	case CPU_UP_CANCELED:
+	case CPU_UP_CANCELED_FROZEN:
+		kvmppc_clear_host_core(cpu);
+		break;
+#endif
+	default:
+		break;
+	}
+
+	return NOTIFY_OK;
+}
+
+static struct notifier_block kvmppc_cpu_notifier = {
+	    .notifier_call = kvmppc_cpu_notify,
+};
+
 /*
  * Allocate a per-core structure for managing state about which cores are
  * running in the host versus the guest and for exchanging data between
@@ -3086,6 +3116,8 @@ void kvmppc_alloc_host_rm_ops(void)
 		return;
 	}
 
+	get_online_cpus();
+
 	for (cpu = 0; cpu < nr_cpu_ids; cpu += threads_per_core) {
 		if (!cpu_online(cpu))
 			continue;
@@ -3104,14 +3136,21 @@ void kvmppc_alloc_host_rm_ops(void)
 	l_ops = (unsigned long) ops;
 
 	if (cmpxchg64((unsigned long *)&kvmppc_host_rm_ops_hv, 0, l_ops)) {
+		put_online_cpus();
 		kfree(ops->rm_core);
 		kfree(ops);
+		return;
 	}
+
+	register_cpu_notifier(&kvmppc_cpu_notifier);
+
+	put_online_cpus();
 }
 
 void kvmppc_free_host_rm_ops(void)
 {
 	if (kvmppc_host_rm_ops_hv) {
+		unregister_cpu_notifier(&kvmppc_cpu_notifier);
 		kfree(kvmppc_host_rm_ops_hv->rm_core);
 		kfree(kvmppc_host_rm_ops_hv);
 		kvmppc_host_rm_ops_hv = NULL;