Merge branch 'linus' into perfcounters/core
[linux-2.6.git] / drivers / xen / cpu_hotplug.c
1 #include <linux/notifier.h>
2
3 #include <xen/xenbus.h>
4
5 #include <asm/xen/hypervisor.h>
6 #include <asm/cpu.h>
7
8 static void enable_hotplug_cpu(int cpu)
9 {
10         if (!cpu_present(cpu))
11                 arch_register_cpu(cpu);
12
13         cpu_set(cpu, cpu_present_map);
14 }
15
16 static void disable_hotplug_cpu(int cpu)
17 {
18         if (cpu_present(cpu))
19                 arch_unregister_cpu(cpu);
20
21         cpu_clear(cpu, cpu_present_map);
22 }
23
24 static void vcpu_hotplug(unsigned int cpu)
25 {
26         int err;
27         char dir[32], state[32];
28
29         if (!cpu_possible(cpu))
30                 return;
31
32         sprintf(dir, "cpu/%u", cpu);
33         err = xenbus_scanf(XBT_NIL, dir, "availability", "%s", state);
34         if (err != 1) {
35                 printk(KERN_ERR "XENBUS: Unable to read cpu state\n");
36                 return;
37         }
38
39         if (strcmp(state, "online") == 0) {
40                 enable_hotplug_cpu(cpu);
41         } else if (strcmp(state, "offline") == 0) {
42                 (void)cpu_down(cpu);
43                 disable_hotplug_cpu(cpu);
44         } else {
45                 printk(KERN_ERR "XENBUS: unknown state(%s) on CPU%d\n",
46                        state, cpu);
47         }
48 }
49
50 static void handle_vcpu_hotplug_event(struct xenbus_watch *watch,
51                                         const char **vec, unsigned int len)
52 {
53         unsigned int cpu;
54         char *cpustr;
55         const char *node = vec[XS_WATCH_PATH];
56
57         cpustr = strstr(node, "cpu/");
58         if (cpustr != NULL) {
59                 sscanf(cpustr, "cpu/%u", &cpu);
60                 vcpu_hotplug(cpu);
61         }
62 }
63
64 static int setup_cpu_watcher(struct notifier_block *notifier,
65                               unsigned long event, void *data)
66 {
67         static struct xenbus_watch cpu_watch = {
68                 .node = "cpu",
69                 .callback = handle_vcpu_hotplug_event};
70
71         (void)register_xenbus_watch(&cpu_watch);
72
73         return NOTIFY_DONE;
74 }
75
76 static int __init setup_vcpu_hotplug_event(void)
77 {
78         static struct notifier_block xsn_cpu = {
79                 .notifier_call = setup_cpu_watcher };
80
81         if (!xen_pv_domain())
82                 return -ENODEV;
83
84         register_xenstore_notifier(&xsn_cpu);
85
86         return 0;
87 }
88
89 arch_initcall(setup_vcpu_hotplug_event);
90