xen: implement CPU hotplugging

[linux-2.6-block.git] / drivers / xen / cpu_hotplug.c

diff --git a/drivers/xen/cpu_hotplug.c b/drivers/xen/cpu_hotplug.c
new file mode 100644 (file)
index 0000000..1bc0035
--- /dev/null
+++ b/drivers/xen/cpu_hotplug.c
@@ -0,0 +1,90 @@
+#include <linux/notifier.h>
+
+#include <xen/xenbus.h>
+
+#include <asm-x86/xen/hypervisor.h>
+#include <asm/cpu.h>
+
+static void enable_hotplug_cpu(int cpu)
+{
+       if (!cpu_present(cpu))
+               arch_register_cpu(cpu);
+
+       cpu_set(cpu, cpu_present_map);
+}
+
+static void disable_hotplug_cpu(int cpu)
+{
+       if (cpu_present(cpu))
+               arch_unregister_cpu(cpu);
+
+       cpu_clear(cpu, cpu_present_map);
+}
+
+static void vcpu_hotplug(unsigned int cpu)
+{
+       int err;
+       char dir[32], state[32];
+
+       if (!cpu_possible(cpu))
+               return;
+
+       sprintf(dir, "cpu/%u", cpu);
+       err = xenbus_scanf(XBT_NIL, dir, "availability", "%s", state);
+       if (err != 1) {
+               printk(KERN_ERR "XENBUS: Unable to read cpu state\n");
+               return;
+       }
+
+       if (strcmp(state, "online") == 0) {
+               enable_hotplug_cpu(cpu);
+       } else if (strcmp(state, "offline") == 0) {
+               (void)cpu_down(cpu);
+               disable_hotplug_cpu(cpu);
+       } else {
+               printk(KERN_ERR "XENBUS: unknown state(%s) on CPU%d\n",
+                      state, cpu);
+       }
+}
+
+static void handle_vcpu_hotplug_event(struct xenbus_watch *watch,
+                                       const char **vec, unsigned int len)
+{
+       unsigned int cpu;
+       char *cpustr;
+       const char *node = vec[XS_WATCH_PATH];
+
+       cpustr = strstr(node, "cpu/");
+       if (cpustr != NULL) {
+               sscanf(cpustr, "cpu/%u", &cpu);
+               vcpu_hotplug(cpu);
+       }
+}
+
+static int setup_cpu_watcher(struct notifier_block *notifier,
+                             unsigned long event, void *data)
+{
+       static struct xenbus_watch cpu_watch = {
+               .node = "cpu",
+               .callback = handle_vcpu_hotplug_event};
+
+       (void)register_xenbus_watch(&cpu_watch);
+
+       return NOTIFY_DONE;
+}
+
+static int __init setup_vcpu_hotplug_event(void)
+{
+       static struct notifier_block xsn_cpu = {
+               .notifier_call = setup_cpu_watcher };
+
+       if (!is_running_on_xen())
+               return -ENODEV;
+
+       register_xenstore_notifier(&xsn_cpu);
+
+       return 0;
+}
+
+arch_initcall(setup_vcpu_hotplug_event);
+