LXR linux/drivers/xen/cpu

   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
  11static 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
  19static 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
  27static 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}
  48static 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
  66static 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
  80static 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
 100static 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
 113arch_initcall(setup_vcpu_hotplug_event);
 114
 115