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 int vcpu_online(unsigned int cpu)
  25 {
  26         int err;
  27         char dir[32], state[32];
  28
  29         sprintf(dir, "cpu/%u", cpu);
  30         err = xenbus_scanf(XBT_NIL, dir, "availability", "%s", state);
  31         if (err != 1) {
  32                 printk(KERN_ERR "XENBUS: Unable to read cpu state\n");
  33                 return err;
  34         }
  35
  36         if (strcmp(state, "online") == 0)
  37                 return 1;
  38         else if (strcmp(state, "offline") == 0)
  39                 return 0;
  40
  41         printk(KERN_ERR "XENBUS: unknown state(%s) on CPU%d\n", state, cpu);
  42         return -EINVAL;
  43 }
  44 static void vcpu_hotplug(unsigned int cpu)
  45 {
  46         if (!cpu_possible(cpu))
  47                 return;
  48
  49         switch (vcpu_online(cpu)) {
  50         case 1:
  51                 enable_hotplug_cpu(cpu);
  52                 break;
  53         case 0:
  54                 (void)cpu_down(cpu);
  55                 disable_hotplug_cpu(cpu);
  56                 break;
  57         default:
  58                 break;
  59         }
  60 }
  61
  62 static void handle_vcpu_hotplug_event(struct xenbus_watch *watch,
  63                                         const char **vec, unsigned int len)
  64 {
  65         unsigned int cpu;
  66         char *cpustr;
  67         const char *node = vec[XS_WATCH_PATH];
  68
  69         cpustr = strstr(node, "cpu/");
  70         if (cpustr != NULL) {
  71                 sscanf(cpustr, "cpu/%u", &cpu);
  72                 vcpu_hotplug(cpu);
  73         }
  74 }
  75
  76 static int setup_cpu_watcher(struct notifier_block *notifier,
  77                               unsigned long event, void *data)
  78 {
  79         int cpu;
  80         static struct xenbus_watch cpu_watch = {
  81                 .node = "cpu",
  82                 .callback = handle_vcpu_hotplug_event};
  83
  84         (void)register_xenbus_watch(&cpu_watch);
  85
  86         for_each_possible_cpu(cpu) {
  87                 if (vcpu_online(cpu) == 0) {
  88                         (void)cpu_down(cpu);
  89                         cpu_clear(cpu, cpu_present_map);
  90                 }
  91         }
  92
  93         return NOTIFY_DONE;
  94 }
  95
  96 static int __init setup_vcpu_hotplug_event(void)
  97 {
  98         static struct notifier_block xsn_cpu = {
  99                 .notifier_call = setup_cpu_watcher };
 100
 101         if (!xen_pv_domain())
 102                 return -ENODEV;
 103
 104         register_xenstore_notifier(&xsn_cpu);
 105
 106         return 0;
 107 }
 108
 109 arch_initcall(setup_vcpu_hotplug_event);
 110