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[16], state[16];
  29
  30         sprintf(dir, "cpu/%u", cpu);
  31         err = xenbus_scanf(XBT_NIL, dir, "availability", "%15s", state);
  32         if (err != 1) {
  33                 if (!xen_initial_domain())
  34                         printk(KERN_ERR "XENBUS: Unable to read cpu state\n");
  35                 return err;
  36         }
  37
  38         if (strcmp(state, "online") == 0)
  39                 return 1;
  40         else if (strcmp(state, "offline") == 0)
  41                 return 0;
  42
  43         printk(KERN_ERR "XENBUS: unknown state(%s) on CPU%d\n", state, cpu);
  44         return -EINVAL;
  45 }
  46 static void vcpu_hotplug(unsigned int cpu)
  47 {
  48         if (!cpu_possible(cpu))
  49                 return;
  50
  51         switch (vcpu_online(cpu)) {
  52         case 1:
  53                 enable_hotplug_cpu(cpu);
  54                 break;
  55         case 0:
  56                 (void)cpu_down(cpu);
  57                 disable_hotplug_cpu(cpu);
  58                 break;
  59         default:
  60                 break;
  61         }
  62 }
  63
  64 static void handle_vcpu_hotplug_event(struct xenbus_watch *watch,
  65                                         const char **vec, unsigned int len)
  66 {
  67         unsigned int cpu;
  68         char *cpustr;
  69         const char *node = vec[XS_WATCH_PATH];
  70
  71         cpustr = strstr(node, "cpu/");
  72         if (cpustr != NULL) {
  73                 sscanf(cpustr, "cpu/%u", &cpu);
  74                 vcpu_hotplug(cpu);
  75         }
  76 }
  77
  78 static int setup_cpu_watcher(struct notifier_block *notifier,
  79                               unsigned long event, void *data)
  80 {
  81         int cpu;
  82         static struct xenbus_watch cpu_watch = {
  83                 .node = "cpu",
  84                 .callback = handle_vcpu_hotplug_event};
  85
  86         (void)register_xenbus_watch(&cpu_watch);
  87
  88         for_each_possible_cpu(cpu) {
  89                 if (vcpu_online(cpu) == 0) {
  90                         (void)cpu_down(cpu);
  91                         set_cpu_present(cpu, false);
  92                 }
  93         }
  94
  95         return NOTIFY_DONE;
  96 }
  97
  98 static int __init setup_vcpu_hotplug_event(void)
  99 {
 100         static struct notifier_block xsn_cpu = {
 101                 .notifier_call = setup_cpu_watcher };
 102
 103         if (!xen_pv_domain())
 104                 return -ENODEV;
 105
 106         register_xenstore_notifier(&xsn_cpu);
 107
 108         return 0;
 109 }
 110
 111 arch_initcall(setup_vcpu_hotplug_event);
 112