drivers/xen/cpu_hotplug.c

   1 #include <linux/notifier.h>
   2
   3 #include <xen/xenbus.h>
   4
   5 #include <asm/xen/hypervisor.h>
   6 #include <asm/cpu.h>
   7
   8 static void enable_hotplug_cpu(int cpu)
   9 {
  10         if (!cpu_present(cpu))
  11                 arch_register_cpu(cpu);
  12
  13         set_cpu_present(cpu, true);
  14 }
  15
  16 static void disable_hotplug_cpu(int cpu)
  17 {
  18         if (cpu_present(cpu))
  19                 arch_unregister_cpu(cpu);
  20
  21         set_cpu_present(cpu, false);
  22 }
  23
  24 static void vcpu_hotplug(unsigned int cpu)
  25 {
  26         int err;
  27         char dir[32], state[32];
  28
  29         if (!cpu_possible(cpu))
  30                 return;
  31
  32         sprintf(dir, "cpu/%u", cpu);
  33         err = xenbus_scanf(XBT_NIL, dir, "availability", "%s", state);
  34         if (err != 1) {
  35                 printk(KERN_ERR "XENBUS: Unable to read cpu state\n");
  36                 return;
  37         }
  38
  39         if (strcmp(state, "online") == 0) {
  40                 enable_hotplug_cpu(cpu);
  41         } else if (strcmp(state, "offline") == 0) {
  42                 (void)cpu_down(cpu);
  43                 disable_hotplug_cpu(cpu);
  44         } else {
  45                 printk(KERN_ERR "XENBUS: unknown state(%s) on CPU%d\n",
  46                        state, cpu);
  47         }
  48 }
  49
  50 static void handle_vcpu_hotplug_event(struct xenbus_watch *watch,
  51                                         const char **vec, unsigned int len)
  52 {
  53         unsigned int cpu;
  54         char *cpustr;
  55         const char *node = vec[XS_WATCH_PATH];
  56
  57         cpustr = strstr(node, "cpu/");
  58         if (cpustr != NULL) {
  59                 sscanf(cpustr, "cpu/%u", &cpu);
  60                 vcpu_hotplug(cpu);
  61         }
  62 }
  63
  64 static int setup_cpu_watcher(struct notifier_block *notifier,
  65                               unsigned long event, void *data)
  66 {
  67         static struct xenbus_watch cpu_watch = {
  68                 .node = "cpu",
  69                 .callback = handle_vcpu_hotplug_event};
  70
  71         (void)register_xenbus_watch(&cpu_watch);
  72
  73         return NOTIFY_DONE;
  74 }
  75
  76 static int __init setup_vcpu_hotplug_event(void)
  77 {
  78         static struct notifier_block xsn_cpu = {
  79                 .notifier_call = setup_cpu_watcher };
  80
  81         if (!xen_pv_domain())
  82                 return -ENODEV;
  83
  84         register_xenstore_notifier(&xsn_cpu);
  85
  86         return 0;
  87 }
  88
  89 arch_initcall(setup_vcpu_hotplug_event);
  90