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