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
);