drivers/xen/cpu_hotplug.c

   1 #define pr_fmt(fmt) "xen:" KBUILD_MODNAME ": " fmt
   2
   3 #include <linux/notifier.h>
   4
   5 #include <xen/xen.h>
   6 #include <xen/xenbus.h>
   7
   8 #include <asm/xen/hypervisor.h>
   9 #include <asm/cpu.h>
  10
  11 static void enable_hotplug_cpu(int cpu)
  12 {
  13         if (!cpu_present(cpu))
  14                 xen_arch_register_cpu(cpu);
  15
  16         set_cpu_present(cpu, true);
  17 }
  18
  19 static void disable_hotplug_cpu(int cpu)
  20 {
  21         if (!cpu_is_hotpluggable(cpu))
  22                 return;
  23         lock_device_hotplug();
  24         if (cpu_online(cpu))
  25                 device_offline(get_cpu_device(cpu));
  26         if (!cpu_online(cpu) && cpu_present(cpu)) {
  27                 xen_arch_unregister_cpu(cpu);
  28                 set_cpu_present(cpu, false);
  29         }
  30         unlock_device_hotplug();
  31 }
  32
  33 static int vcpu_online(unsigned int cpu)
  34 {
  35         int err;
  36         char dir[16], state[16];
  37
  38         sprintf(dir, "cpu/%u", cpu);
  39         err = xenbus_scanf(XBT_NIL, dir, "availability", "%15s", state);
  40         if (err != 1) {
  41                 if (!xen_initial_domain())
  42                         pr_err("Unable to read cpu state\n");
  43                 return err;
  44         }
  45
  46         if (strcmp(state, "online") == 0)
  47                 return 1;
  48         else if (strcmp(state, "offline") == 0)
  49                 return 0;
  50
  51         pr_err("unknown state(%s) on CPU%d\n", state, cpu);
  52         return -EINVAL;
  53 }
  54 static void vcpu_hotplug(unsigned int cpu)
  55 {
  56         if (cpu >= nr_cpu_ids || !cpu_possible(cpu))
  57                 return;
  58
  59         switch (vcpu_online(cpu)) {
  60         case 1:
  61                 enable_hotplug_cpu(cpu);
  62                 break;
  63         case 0:
  64                 disable_hotplug_cpu(cpu);
  65                 break;
  66         default:
  67                 break;
  68         }
  69 }
  70
  71 static void handle_vcpu_hotplug_event(struct xenbus_watch *watch,
  72                                         const char **vec, unsigned int len)
  73 {
  74         unsigned int cpu;
  75         char *cpustr;
  76         const char *node = vec[XS_WATCH_PATH];
  77
  78         cpustr = strstr(node, "cpu/");
  79         if (cpustr != NULL) {
  80                 sscanf(cpustr, "cpu/%u", &cpu);
  81                 vcpu_hotplug(cpu);
  82         }
  83 }
  84
  85 static int setup_cpu_watcher(struct notifier_block *notifier,
  86                               unsigned long event, void *data)
  87 {
  88         int cpu;
  89         static struct xenbus_watch cpu_watch = {
  90                 .node = "cpu",
  91                 .callback = handle_vcpu_hotplug_event};
  92
  93         (void)register_xenbus_watch(&cpu_watch);
  94
  95         for_each_possible_cpu(cpu) {
  96                 if (vcpu_online(cpu) == 0) {
  97                         (void)cpu_down(cpu);
  98                         set_cpu_present(cpu, false);
  99                 }
 100         }
 101
 102         return NOTIFY_DONE;
 103 }
 104
 105 static int __init setup_vcpu_hotplug_event(void)
 106 {
 107         static struct notifier_block xsn_cpu = {
 108                 .notifier_call = setup_cpu_watcher };
 109
 110 #ifdef CONFIG_X86
 111         if (!xen_pv_domain())
 112 #else
 113         if (!xen_domain())
 114 #endif
 115                 return -ENODEV;
 116
 117         register_xenstore_notifier(&xsn_cpu);
 118
 119         return 0;
 120 }
 121
 122 arch_initcall(setup_vcpu_hotplug_event);
 123