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
9static 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
17static 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
25static 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		if (!xen_initial_domain())
34			printk(KERN_ERR "XENBUS: Unable to read cpu state\n");
35		return err;
36	}
37
38	if (strcmp(state, "online") == 0)
39		return 1;
40	else if (strcmp(state, "offline") == 0)
41		return 0;
42
43	printk(KERN_ERR "XENBUS: unknown state(%s) on CPU%d\n", state, cpu);
44	return -EINVAL;
45}
46static void vcpu_hotplug(unsigned int cpu)
47{
48	if (!cpu_possible(cpu))
49		return;
50
51	switch (vcpu_online(cpu)) {
52	case 1:
53		enable_hotplug_cpu(cpu);
54		break;
55	case 0:
56		(void)cpu_down(cpu);
57		disable_hotplug_cpu(cpu);
58		break;
59	default:
60		break;
61	}
62}
63
64static void handle_vcpu_hotplug_event(struct xenbus_watch *watch,
65					const char **vec, unsigned int len)
66{
67	unsigned int cpu;
68	char *cpustr;
69	const char *node = vec[XS_WATCH_PATH];
70
71	cpustr = strstr(node, "cpu/");
72	if (cpustr != NULL) {
73		sscanf(cpustr, "cpu/%u", &cpu);
74		vcpu_hotplug(cpu);
75	}
76}
77
78static int setup_cpu_watcher(struct notifier_block *notifier,
79			      unsigned long event, void *data)
80{
81	int cpu;
82	static struct xenbus_watch cpu_watch = {
83		.node = "cpu",
84		.callback = handle_vcpu_hotplug_event};
85
86	(void)register_xenbus_watch(&cpu_watch);
87
88	for_each_possible_cpu(cpu) {
89		if (vcpu_online(cpu) == 0) {
90			(void)cpu_down(cpu);
91			set_cpu_present(cpu, false);
92		}
93	}
94
95	return NOTIFY_DONE;
96}
97
98static int __init setup_vcpu_hotplug_event(void)
99{
100	static struct notifier_block xsn_cpu = {
101		.notifier_call = setup_cpu_watcher };
102
103	if (!xen_pv_domain())
104		return -ENODEV;
105
106	register_xenstore_notifier(&xsn_cpu);
107
108	return 0;
109}
110
111arch_initcall(setup_vcpu_hotplug_event);
112
113