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
11static 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
19static void disable_hotplug_cpu(int cpu)
20{
21	if (cpu_online(cpu)) {
22		lock_device_hotplug();
23		device_offline(get_cpu_device(cpu));
24		unlock_device_hotplug();
25	}
26	if (cpu_present(cpu))
27		xen_arch_unregister_cpu(cpu);
28
29	set_cpu_present(cpu, false);
30}
31
32static int vcpu_online(unsigned int cpu)
33{
34	int err;
35	char dir[16], state[16];
36
37	sprintf(dir, "cpu/%u", cpu);
38	err = xenbus_scanf(XBT_NIL, dir, "availability", "%15s", state);
39	if (err != 1) {
40		if (!xen_initial_domain())
41			pr_err("Unable to read cpu state\n");
42		return err;
43	}
44
45	if (strcmp(state, "online") == 0)
46		return 1;
47	else if (strcmp(state, "offline") == 0)
48		return 0;
49
50	pr_err("unknown state(%s) on CPU%d\n", state, cpu);
51	return -EINVAL;
52}
53static void vcpu_hotplug(unsigned int cpu)
54{
55	if (!cpu_possible(cpu))
56		return;
57
58	switch (vcpu_online(cpu)) {
59	case 1:
60		enable_hotplug_cpu(cpu);
61		break;
62	case 0:
63		disable_hotplug_cpu(cpu);
64		break;
65	default:
66		break;
67	}
68}
69
70static void handle_vcpu_hotplug_event(struct xenbus_watch *watch,
71					const char **vec, unsigned int len)
72{
73	unsigned int cpu;
74	char *cpustr;
75	const char *node = vec[XS_WATCH_PATH];
76
77	cpustr = strstr(node, "cpu/");
78	if (cpustr != NULL) {
79		sscanf(cpustr, "cpu/%u", &cpu);
80		vcpu_hotplug(cpu);
81	}
82}
83
84static int setup_cpu_watcher(struct notifier_block *notifier,
85			      unsigned long event, void *data)
86{
87	int cpu;
88	static struct xenbus_watch cpu_watch = {
89		.node = "cpu",
90		.callback = handle_vcpu_hotplug_event};
91
92	(void)register_xenbus_watch(&cpu_watch);
93
94	for_each_possible_cpu(cpu) {
95		if (vcpu_online(cpu) == 0) {
96			(void)cpu_down(cpu);
97			set_cpu_present(cpu, false);
98		}
99	}
100
101	return NOTIFY_DONE;
102}
103
104static int __init setup_vcpu_hotplug_event(void)
105{
106	static struct notifier_block xsn_cpu = {
107		.notifier_call = setup_cpu_watcher };
108
109#ifdef CONFIG_X86
110	if (!xen_pv_domain())
111#else
112	if (!xen_domain())
113#endif
114		return -ENODEV;
115
116	register_xenstore_notifier(&xsn_cpu);
117
118	return 0;
119}
120
121arch_initcall(setup_vcpu_hotplug_event);
122
123