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 (void)cpu_down(cpu);
98 set_cpu_present(cpu, false);
99 }
100 }
101
102 return NOTIFY_DONE;
103}
104
105static 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() && !xen_pvh_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
122arch_initcall(setup_vcpu_hotplug_event);
123
124