Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
tjh.dev
kernel
os
linux
1#include <linux/notifier.h>
2
3#include <xen/xenbus.h>
4
5#include <asm/xen/hypervisor.h>
6#include <asm/cpu.h>
7
8static void enable_hotplug_cpu(int cpu)
9{
10 if (!cpu_present(cpu))
11 arch_register_cpu(cpu);
12
13 cpu_set(cpu, cpu_present_map);
14}
15
16static void disable_hotplug_cpu(int cpu)
17{
18 if (cpu_present(cpu))
19 arch_unregister_cpu(cpu);
20
21 cpu_clear(cpu, cpu_present_map);
22}
23
24static void vcpu_hotplug(unsigned int cpu)
25{
26 int err;
27 char dir[32], state[32];
28
29 if (!cpu_possible(cpu))
30 return;
31
32 sprintf(dir, "cpu/%u", cpu);
33 err = xenbus_scanf(XBT_NIL, dir, "availability", "%s", state);
34 if (err != 1) {
35 printk(KERN_ERR "XENBUS: Unable to read cpu state\n");
36 return;
37 }
38
39 if (strcmp(state, "online") == 0) {
40 enable_hotplug_cpu(cpu);
41 } else if (strcmp(state, "offline") == 0) {
42 (void)cpu_down(cpu);
43 disable_hotplug_cpu(cpu);
44 } else {
45 printk(KERN_ERR "XENBUS: unknown state(%s) on CPU%d\n",
46 state, cpu);
47 }
48}
49
50static void handle_vcpu_hotplug_event(struct xenbus_watch *watch,
51 const char **vec, unsigned int len)
52{
53 unsigned int cpu;
54 char *cpustr;
55 const char *node = vec[XS_WATCH_PATH];
56
57 cpustr = strstr(node, "cpu/");
58 if (cpustr != NULL) {
59 sscanf(cpustr, "cpu/%u", &cpu);
60 vcpu_hotplug(cpu);
61 }
62}
63
64static int setup_cpu_watcher(struct notifier_block *notifier,
65 unsigned long event, void *data)
66{
67 static struct xenbus_watch cpu_watch = {
68 .node = "cpu",
69 .callback = handle_vcpu_hotplug_event};
70
71 (void)register_xenbus_watch(&cpu_watch);
72
73 return NOTIFY_DONE;
74}
75
76static int __init setup_vcpu_hotplug_event(void)
77{
78 static struct notifier_block xsn_cpu = {
79 .notifier_call = setup_cpu_watcher };
80
81 if (!xen_pv_domain())
82 return -ENODEV;
83
84 register_xenstore_notifier(&xsn_cpu);
85
86 return 0;
87}
88
89arch_initcall(setup_vcpu_hotplug_event);
90