1 // SPDX-License-Identifier: GPL-2.0
2 #define pr_fmt(fmt) "xen:" KBUILD_MODNAME ": " fmt
4 #include <linux/notifier.h>
7 #include <xen/xenbus.h>
9 #include <asm/xen/hypervisor.h>
12 static void enable_hotplug_cpu(int cpu)
14 if (!cpu_present(cpu))
15 xen_arch_register_cpu(cpu);
17 set_cpu_present(cpu, true);
20 static void disable_hotplug_cpu(int cpu)
22 if (!cpu_is_hotpluggable(cpu))
24 lock_device_hotplug();
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);
31 unlock_device_hotplug();
34 static int vcpu_online(unsigned int cpu)
37 char dir[16], state[16];
39 sprintf(dir, "cpu/%u", cpu);
40 err = xenbus_scanf(XBT_NIL, dir, "availability", "%15s", state);
42 if (!xen_initial_domain())
43 pr_err("Unable to read cpu state\n");
47 if (strcmp(state, "online") == 0)
49 else if (strcmp(state, "offline") == 0)
52 pr_err("unknown state(%s) on CPU%d\n", state, cpu);
55 static void vcpu_hotplug(unsigned int cpu)
57 if (cpu >= nr_cpu_ids || !cpu_possible(cpu))
60 switch (vcpu_online(cpu)) {
62 enable_hotplug_cpu(cpu);
65 disable_hotplug_cpu(cpu);
72 static void handle_vcpu_hotplug_event(struct xenbus_watch *watch,
73 const char *path, const char *token)
78 cpustr = strstr(path, "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)
97 disable_hotplug_cpu(cpu);
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 late_initcall(setup_vcpu_hotplug_event);