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