drivers/xen/cpu_hotplug.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 #define pr_fmt(fmt) "xen:" KBUILD_MODNAME ": " fmt
   3
   4 #include <linux/notifier.h>
   5
   6 #include <xen/xen.h>
   7 #include <xen/xenbus.h>
   8
   9 #include <asm/xen/hypervisor.h>
  10 #include <asm/cpu.h>
  11
  12 static void enable_hotplug_cpu(int cpu)
  13 {
  14         if (!cpu_present(cpu))
  15                 xen_arch_register_cpu(cpu);
  16
  17         set_cpu_present(cpu, true);
  18 }
  19
  20 static void disable_hotplug_cpu(int cpu)
  21 {
  22         if (cpu_online(cpu)) {
  23                 lock_device_hotplug();
  24                 device_offline(get_cpu_device(cpu));
  25                 unlock_device_hotplug();
  26         }
  27         if (cpu_present(cpu))
  28                 xen_arch_unregister_cpu(cpu);
  29
  30         set_cpu_present(cpu, false);
  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_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 *path, const char *token)
  73 {
  74         unsigned int cpu;
  75         char *cpustr;
  76
  77         cpustr = strstr(path, "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() && !xen_pvh_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