1 #include <linux/notifier.h>
2
3 #include <xen/xen.h>
4 #include <xen/xenbus.h>
5
6 #include <asm/xen/hypervisor.h>
7 #include <asm/cpu.h>
8
enable_hotplug_cpu(int cpu)9 static void enable_hotplug_cpu(int cpu)
10 {
11 if (!cpu_present(cpu))
12 arch_register_cpu(cpu);
13
14 set_cpu_present(cpu, true);
15 }
16
disable_hotplug_cpu(int cpu)17 static void disable_hotplug_cpu(int cpu)
18 {
19 if (cpu_present(cpu))
20 arch_unregister_cpu(cpu);
21
22 set_cpu_present(cpu, false);
23 }
24
vcpu_online(unsigned int cpu)25 static int vcpu_online(unsigned int cpu)
26 {
27 int err;
28 char dir[32], state[32];
29
30 sprintf(dir, "cpu/%u", cpu);
31 err = xenbus_scanf(XBT_NIL, dir, "availability", "%s", state);
32 if (err != 1) {
33 printk(KERN_ERR "XENBUS: Unable to read cpu state\n");
34 return err;
35 }
36
37 if (strcmp(state, "online") == 0)
38 return 1;
39 else if (strcmp(state, "offline") == 0)
40 return 0;
41
42 printk(KERN_ERR "XENBUS: unknown state(%s) on CPU%d\n", state, cpu);
43 return -EINVAL;
44 }
vcpu_hotplug(unsigned int cpu)45 static void vcpu_hotplug(unsigned int cpu)
46 {
47 if (!cpu_possible(cpu))
48 return;
49
50 switch (vcpu_online(cpu)) {
51 case 1:
52 enable_hotplug_cpu(cpu);
53 break;
54 case 0:
55 (void)cpu_down(cpu);
56 disable_hotplug_cpu(cpu);
57 break;
58 default:
59 break;
60 }
61 }
62
handle_vcpu_hotplug_event(struct xenbus_watch * watch,const char ** vec,unsigned int len)63 static void handle_vcpu_hotplug_event(struct xenbus_watch *watch,
64 const char **vec, unsigned int len)
65 {
66 unsigned int cpu;
67 char *cpustr;
68 const char *node = vec[XS_WATCH_PATH];
69
70 cpustr = strstr(node, "cpu/");
71 if (cpustr != NULL) {
72 sscanf(cpustr, "cpu/%u", &cpu);
73 vcpu_hotplug(cpu);
74 }
75 }
76
setup_cpu_watcher(struct notifier_block * notifier,unsigned long event,void * data)77 static int setup_cpu_watcher(struct notifier_block *notifier,
78 unsigned long event, void *data)
79 {
80 int cpu;
81 static struct xenbus_watch cpu_watch = {
82 .node = "cpu",
83 .callback = handle_vcpu_hotplug_event};
84
85 (void)register_xenbus_watch(&cpu_watch);
86
87 for_each_possible_cpu(cpu) {
88 if (vcpu_online(cpu) == 0) {
89 (void)cpu_down(cpu);
90 set_cpu_present(cpu, false);
91 }
92 }
93
94 return NOTIFY_DONE;
95 }
96
setup_vcpu_hotplug_event(void)97 static int __init setup_vcpu_hotplug_event(void)
98 {
99 static struct notifier_block xsn_cpu = {
100 .notifier_call = setup_cpu_watcher };
101
102 if (!xen_pv_domain())
103 return -ENODEV;
104
105 register_xenstore_notifier(&xsn_cpu);
106
107 return 0;
108 }
109
110 arch_initcall(setup_vcpu_hotplug_event);
111
112