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_is_hotpluggable(cpu))
23 lock_device_hotplug();
25 device_offline(get_cpu_device(cpu));
26 if (!cpu_online(cpu) && cpu_present(cpu)) {
27 xen_arch_unregister_cpu(cpu);
28 set_cpu_present(cpu, false);
30 unlock_device_hotplug();
33 static int vcpu_online(unsigned int cpu)
36 char dir[16], state[16];
38 sprintf(dir, "cpu/%u", cpu);
39 err = xenbus_scanf(XBT_NIL, dir, "availability", "%15s", state);
41 if (!xen_initial_domain())
42 pr_err("Unable to read cpu state\n");
46 if (strcmp(state, "online") == 0)
48 else if (strcmp(state, "offline") == 0)
51 pr_err("unknown state(%s) on CPU%d\n", state, cpu);
54 static void vcpu_hotplug(unsigned int cpu)
56 if (cpu >= nr_cpu_ids || !cpu_possible(cpu))
59 switch (vcpu_online(cpu)) {
61 enable_hotplug_cpu(cpu);
64 disable_hotplug_cpu(cpu);
71 static void handle_vcpu_hotplug_event(struct xenbus_watch *watch,
72 const char **vec, unsigned int len)
76 const char *node = vec[XS_WATCH_PATH];
78 cpustr = strstr(node, "cpu/");
80 sscanf(cpustr, "cpu/%u", &cpu);
85 static int setup_cpu_watcher(struct notifier_block *notifier,
86 unsigned long event, void *data)
89 static struct xenbus_watch cpu_watch = {
91 .callback = handle_vcpu_hotplug_event};
93 (void)register_xenbus_watch(&cpu_watch);
95 for_each_possible_cpu(cpu) {
96 if (vcpu_online(cpu) == 0) {
98 set_cpu_present(cpu, false);
105 static int __init setup_vcpu_hotplug_event(void)
107 static struct notifier_block xsn_cpu = {
108 .notifier_call = setup_cpu_watcher };
111 if (!xen_pv_domain())
117 register_xenstore_notifier(&xsn_cpu);
122 arch_initcall(setup_vcpu_hotplug_event);