LXR linux/drivers/xen/cpu

   1#include <linux/notifier.h>
   2
   3#include <xen/xenbus.h>
   4
   5#include <asm/xen/hypervisor.h>
   6#include <asm/cpu.h>
   7
   8static void enable_hotplug_cpu(int cpu)
   9{
  10        if (!cpu_present(cpu))
  11                arch_register_cpu(cpu);
  12
  13        set_cpu_present(cpu, true);
  14}
  15
  16static void disable_hotplug_cpu(int cpu)
  17{
  18        if (cpu_present(cpu))
  19                arch_unregister_cpu(cpu);
  20
  21        set_cpu_present(cpu, false);
  22}
  23
  24static int vcpu_online(unsigned int cpu)
  25{
  26        int err;
  27        char dir[32], state[32];
  28
  29        sprintf(dir, "cpu/%u", cpu);
  30        err = xenbus_scanf(XBT_NIL, dir, "availability", "%s", state);
  31        if (err != 1) {
  32                printk(KERN_ERR "XENBUS: Unable to read cpu state\n");
  33                return err;
  34        }
  35
  36        if (strcmp(state, "online") == 0)
  37                return 1;
  38        else if (strcmp(state, "offline") == 0)
  39                return 0;
  40
  41        printk(KERN_ERR "XENBUS: unknown state(%s) on CPU%d\n", state, cpu);
  42        return -EINVAL;
  43}
  44static void vcpu_hotplug(unsigned int cpu)
  45{
  46        if (!cpu_possible(cpu))
  47                return;
  48
  49        switch (vcpu_online(cpu)) {
  50        case 1:
  51                enable_hotplug_cpu(cpu);
  52                break;
  53        case 0:
  54                (void)cpu_down(cpu);
  55                disable_hotplug_cpu(cpu);
  56                break;
  57        default:
  58                break;
  59        }
  60}
  61
  62static void handle_vcpu_hotplug_event(struct xenbus_watch *watch,
  63                                        const char **vec, unsigned int len)
  64{
  65        unsigned int cpu;
  66        char *cpustr;
  67        const char *node = vec[XS_WATCH_PATH];
  68
  69        cpustr = strstr(node, "cpu/");
  70        if (cpustr != NULL) {
  71                sscanf(cpustr, "cpu/%u", &cpu);
  72                vcpu_hotplug(cpu);
  73        }
  74}
  75
  76static int setup_cpu_watcher(struct notifier_block *notifier,
  77                              unsigned long event, void *data)
  78{
  79        int cpu;
  80        static struct xenbus_watch cpu_watch = {
  81                .node = "cpu",
  82                .callback = handle_vcpu_hotplug_event};
  83
  84        (void)register_xenbus_watch(&cpu_watch);
  85
  86        for_each_possible_cpu(cpu) {
  87                if (vcpu_online(cpu) == 0) {
  88                        (void)cpu_down(cpu);
  89                        cpu_clear(cpu, cpu_present_map);
  90                }
  91        }
  92
  93        return NOTIFY_DONE;
  94}
  95
  96static int __init setup_vcpu_hotplug_event(void)
  97{
  98        static struct notifier_block xsn_cpu = {
  99                .notifier_call = setup_cpu_watcher };
 100
 101        if (!xen_pv_domain())
 102                return -ENODEV;
 103
 104        register_xenstore_notifier(&xsn_cpu);
 105
 106        return 0;
 107}
 108
 109arch_initcall(setup_vcpu_hotplug_event);
 110
 111