Merge tag 'asm-generic-timers-5.11' of git://git.kernel.org/pub/scm/linux/kernel...
[linux-2.6-microblaze.git] / drivers / xen / cpu_hotplug.c
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
12 static 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
20 static 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
34 static 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 }
55 static 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
72 static 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
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                         disable_hotplug_cpu(cpu);
98         }
99
100         return NOTIFY_DONE;
101 }
102
103 static 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
120 late_initcall(setup_vcpu_hotplug_event);
121