drivers/xen/cpu_hotplug.c

   1 #include <linux/notifier.h>
   2
   3 #include <xen/xen.h>
   4 #include <xen/xenbus.h>
   5
   6 #include <asm/xen/hypervisor.h>
   7 #include <asm/cpu.h>
   8
   9 static void enable_hotplug_cpu(int cpu)
  10 {
  11         if (!cpu_present(cpu))
  12                 arch_register_cpu(cpu);
  13
  14         set_cpu_present(cpu, true);
  15 }
  16
  17 static void disable_hotplug_cpu(int cpu)
  18 {
  19         if (cpu_present(cpu))
  20                 arch_unregister_cpu(cpu);
  21
  22         set_cpu_present(cpu, false);
  23 }
  24
  25 static int vcpu_online(unsigned int cpu)
  26 {
  27         int err;
  28         char dir[32], state[32];
  29
  30         sprintf(dir, "cpu/%u", cpu);
  31         err = xenbus_scanf(XBT_NIL, dir, "availability", "%s", state);
  32         if (err != 1) {
  33                 printk(KERN_ERR "XENBUS: Unable to read cpu state\n");
  34                 return err;
  35         }
  36
  37         if (strcmp(state, "online") == 0)
  38                 return 1;
  39         else if (strcmp(state, "offline") == 0)
  40                 return 0;
  41
  42         printk(KERN_ERR "XENBUS: unknown state(%s) on CPU%d\n", state, cpu);
  43         return -EINVAL;
  44 }
  45 static void vcpu_hotplug(unsigned int cpu)
  46 {
  47         if (!cpu_possible(cpu))
  48                 return;
  49
  50         switch (vcpu_online(cpu)) {
  51         case 1:
  52                 enable_hotplug_cpu(cpu);
  53                 break;
  54         case 0:
  55                 (void)cpu_down(cpu);
  56                 disable_hotplug_cpu(cpu);
  57                 break;
  58         default:
  59                 break;
  60         }
  61 }
  62
  63 static void handle_vcpu_hotplug_event(struct xenbus_watch *watch,
  64                                         const char **vec, unsigned int len)
  65 {
  66         unsigned int cpu;
  67         char *cpustr;
  68         const char *node = vec[XS_WATCH_PATH];
  69
  70         cpustr = strstr(node, "cpu/");
  71         if (cpustr != NULL) {
  72                 sscanf(cpustr, "cpu/%u", &cpu);
  73                 vcpu_hotplug(cpu);
  74         }
  75 }
  76
  77 static int setup_cpu_watcher(struct notifier_block *notifier,
  78                               unsigned long event, void *data)
  79 {
  80         int cpu;
  81         static struct xenbus_watch cpu_watch = {
  82                 .node = "cpu",
  83                 .callback = handle_vcpu_hotplug_event};
  84
  85         (void)register_xenbus_watch(&cpu_watch);
  86
  87         for_each_possible_cpu(cpu) {
  88                 if (vcpu_online(cpu) == 0) {
  89                         (void)cpu_down(cpu);
  90                         cpu_clear(cpu, cpu_present_map);
  91                 }
  92         }
  93
  94         return NOTIFY_DONE;
  95 }
  96
  97 static int __init setup_vcpu_hotplug_event(void)
  98 {
  99         static struct notifier_block xsn_cpu = {
 100                 .notifier_call = setup_cpu_watcher };
 101
 102         if (!xen_pv_domain())
 103                 return -ENODEV;
 104
 105         register_xenstore_notifier(&xsn_cpu);
 106
 107         return 0;
 108 }
 109
 110 arch_initcall(setup_vcpu_hotplug_event);
 111