tjh.dev
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
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 *path, const char *token)
72{
73 unsigned int cpu;
74 char *cpustr;
75
76 cpustr = strstr(path, "cpu/");
77 if (cpustr != NULL) {
78 sscanf(cpustr, "cpu/%u", &cpu);
79 vcpu_hotplug(cpu);
80 }
81}
82
83static int setup_cpu_watcher(struct notifier_block *notifier,
84 unsigned long event, void *data)
85{
86 int cpu;
87 static struct xenbus_watch cpu_watch = {
88 .node = "cpu",
89 .callback = handle_vcpu_hotplug_event};
90
91 (void)register_xenbus_watch(&cpu_watch);
92
93 for_each_possible_cpu(cpu) {
94 if (vcpu_online(cpu) == 0) {
95 (void)cpu_down(cpu);
96 set_cpu_present(cpu, false);
97 }
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
120arch_initcall(setup_vcpu_hotplug_event);
121