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
enable_hotplug_cpu(int cpu)11 static void enable_hotplug_cpu(int cpu)
12 {
13 if (!cpu_present(cpu))
14 xen_arch_register_cpu(cpu);
15
16 set_cpu_present(cpu, true);
17 }
18
disable_hotplug_cpu(int cpu)19 static void disable_hotplug_cpu(int cpu)
20 {
21 if (!cpu_is_hotpluggable(cpu))
22 return;
23 lock_device_hotplug();
24 if (cpu_online(cpu))
25 device_offline(get_cpu_device(cpu));
26 if (!cpu_online(cpu) && cpu_present(cpu)) {
27 xen_arch_unregister_cpu(cpu);
28 set_cpu_present(cpu, false);
29 }
30 unlock_device_hotplug();
31 }
32
vcpu_online(unsigned int cpu)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 }
vcpu_hotplug(unsigned int cpu)54 static void vcpu_hotplug(unsigned int cpu)
55 {
56 if (cpu >= nr_cpu_ids || !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
handle_vcpu_hotplug_event(struct xenbus_watch * watch,const char ** vec,unsigned int len)71 static void handle_vcpu_hotplug_event(struct xenbus_watch *watch,
72 const char **vec, unsigned int len)
73 {
74 unsigned int cpu;
75 char *cpustr;
76 const char *node = vec[XS_WATCH_PATH];
77
78 cpustr = strstr(node, "cpu/");
79 if (cpustr != NULL) {
80 sscanf(cpustr, "cpu/%u", &cpu);
81 vcpu_hotplug(cpu);
82 }
83 }
84
setup_cpu_watcher(struct notifier_block * notifier,unsigned long event,void * data)85 static int setup_cpu_watcher(struct notifier_block *notifier,
86 unsigned long event, void *data)
87 {
88 int cpu;
89 static struct xenbus_watch cpu_watch = {
90 .node = "cpu",
91 .callback = handle_vcpu_hotplug_event};
92
93 (void)register_xenbus_watch(&cpu_watch);
94
95 for_each_possible_cpu(cpu) {
96 if (vcpu_online(cpu) == 0) {
97 (void)cpu_down(cpu);
98 set_cpu_present(cpu, false);
99 }
100 }
101
102 return NOTIFY_DONE;
103 }
104
setup_vcpu_hotplug_event(void)105 static int __init setup_vcpu_hotplug_event(void)
106 {
107 static struct notifier_block xsn_cpu = {
108 .notifier_call = setup_cpu_watcher };
109
110 #ifdef CONFIG_X86
111 if (!xen_pv_domain())
112 #else
113 if (!xen_domain())
114 #endif
115 return -ENODEV;
116
117 register_xenstore_notifier(&xsn_cpu);
118
119 return 0;
120 }
121
122 arch_initcall(setup_vcpu_hotplug_event);
123
124