1// SPDX-License-Identifier: GPL-2.0
2#define pr_fmt(fmt) "xen:" KBUILD_MODNAME ": " fmt
3
4#include <linux/notifier.h>
5
6#include <xen/xen.h>
7#include <xen/xenbus.h>
8
9#include <asm/xen/hypervisor.h>
10#include <asm/cpu.h>
11
12static void enable_hotplug_cpu(int cpu)
13{
14	if (!cpu_present(cpu))
15		xen_arch_register_cpu(cpu);
16
17	set_cpu_present(cpu, true);
18}
19
20static void disable_hotplug_cpu(int cpu)
21{
22	if (!cpu_is_hotpluggable(cpu))
23		return;
24	lock_device_hotplug();
25	if (cpu_online(cpu))
26		device_offline(get_cpu_device(cpu));
27	if (!cpu_online(cpu) && cpu_present(cpu)) {
28		xen_arch_unregister_cpu(cpu);
29		set_cpu_present(cpu, false);
30	}
31	unlock_device_hotplug();
32}
33
34static int vcpu_online(unsigned int cpu)
35{
36	int err;
37	char dir[16], state[16];
38
39	sprintf(dir, "cpu/%u", cpu);
40	err = xenbus_scanf(XBT_NIL, dir, "availability", "%15s", state);
41	if (err != 1) {
42		if (!xen_initial_domain())
43			pr_err("Unable to read cpu state\n");
44		return err;
45	}
46
47	if (strcmp(state, "online") == 0)
48		return 1;
49	else if (strcmp(state, "offline") == 0)
50		return 0;
51
52	pr_err("unknown state(%s) on CPU%d\n", state, cpu);
53	return -EINVAL;
54}
55static void vcpu_hotplug(unsigned int cpu)
56{
57	if (cpu >= nr_cpu_ids || !cpu_possible(cpu))
58		return;
59
60	switch (vcpu_online(cpu)) {
61	case 1:
62		enable_hotplug_cpu(cpu);
63		break;
64	case 0:
65		disable_hotplug_cpu(cpu);
66		break;
67	default:
68		break;
69	}
70}
71
72static void handle_vcpu_hotplug_event(struct xenbus_watch *watch,
73				      const char *path, const char *token)
74{
75	unsigned int cpu;
76	char *cpustr;
77
78	cpustr = strstr(path, "cpu/");
79	if (cpustr != NULL) {
80		sscanf(cpustr, "cpu/%u", &cpu);
81		vcpu_hotplug(cpu);
82	}
83}
84
85static 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			disable_hotplug_cpu(cpu);
98	}
99
100	return NOTIFY_DONE;
101}
102
103static int __init setup_vcpu_hotplug_event(void)
104{
105	static struct notifier_block xsn_cpu = {
106		.notifier_call = setup_cpu_watcher };
107
108#ifdef CONFIG_X86
109	if (!xen_pv_domain() && !xen_pvh_domain())
110#else
111	if (!xen_domain())
112#endif
113		return -ENODEV;
114
115	register_xenstore_notifier(&xsn_cpu);
116
117	return 0;
118}
119
120late_initcall(setup_vcpu_hotplug_event);
121
122