1 #define pr_fmt(fmt) "xen:" KBUILD_MODNAME ": " fmt
3 #include <linux/notifier.h>
6 #include <xen/xenbus.h>
8 #include <asm/xen/hypervisor.h>
11 static void enable_hotplug_cpu(int cpu)
13 if (!cpu_present(cpu))
14 xen_arch_register_cpu(cpu);
16 set_cpu_present(cpu, true);
19 static void disable_hotplug_cpu(int cpu)
21 if (cpu_online(cpu)) {
22 lock_device_hotplug();
23 device_offline(get_cpu_device(cpu));
24 unlock_device_hotplug();
27 xen_arch_unregister_cpu(cpu);
29 set_cpu_present(cpu, false);
32 static int vcpu_online(unsigned int cpu)
35 char dir[16], state[16];
37 sprintf(dir, "cpu/%u", cpu);
38 err = xenbus_scanf(XBT_NIL, dir, "availability", "%15s", state);
40 if (!xen_initial_domain())
41 pr_err("Unable to read cpu state\n");
45 if (strcmp(state, "online") == 0)
47 else if (strcmp(state, "offline") == 0)
50 pr_err("unknown state(%s) on CPU%d\n", state, cpu);
53 static void vcpu_hotplug(unsigned int cpu)
55 if (!cpu_possible(cpu))
58 switch (vcpu_online(cpu)) {
60 enable_hotplug_cpu(cpu);
63 disable_hotplug_cpu(cpu);
70 static void handle_vcpu_hotplug_event(struct xenbus_watch *watch,
71 const char *path, const char *token)
76 cpustr = strstr(path, "cpu/");
78 sscanf(cpustr, "cpu/%u", &cpu);
83 static int setup_cpu_watcher(struct notifier_block *notifier,
84 unsigned long event, void *data)
87 static struct xenbus_watch cpu_watch = {
89 .callback = handle_vcpu_hotplug_event};
91 (void)register_xenbus_watch(&cpu_watch);
93 for_each_possible_cpu(cpu) {
94 if (vcpu_online(cpu) == 0) {
96 set_cpu_present(cpu, false);
103 static int __init setup_vcpu_hotplug_event(void)
105 static struct notifier_block xsn_cpu = {
106 .notifier_call = setup_cpu_watcher };
109 if (!xen_pv_domain() && !xen_pvh_domain())
115 register_xenstore_notifier(&xsn_cpu);
120 arch_initcall(setup_vcpu_hotplug_event);