Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
tjh.dev
kernel
os
linux
1// SPDX-License-Identifier: GPL-2.0
2#define pr_fmt(fmt) "xen:" KBUILD_MODNAME ": " fmt
3
4#include <linux/notifier.h>
5
6#include <xen/xen.h>
7#include <xen/xenbus.h>
8
9#include <asm/xen/hypervisor.h>
10#include <asm/cpu.h>
11
12static void enable_hotplug_cpu(int cpu)
13{
14 if (!cpu_present(cpu))
15 xen_arch_register_cpu(cpu);
16
17 set_cpu_present(cpu, true);
18}
19
20static void disable_hotplug_cpu(int cpu)
21{
22 if (cpu_online(cpu)) {
23 lock_device_hotplug();
24 device_offline(get_cpu_device(cpu));
25 unlock_device_hotplug();
26 }
27 if (cpu_present(cpu))
28 xen_arch_unregister_cpu(cpu);
29
30 set_cpu_present(cpu, false);
31}
32
33static int vcpu_online(unsigned int cpu)
34{
35 int err;
36 char dir[16], state[16];
37
38 sprintf(dir, "cpu/%u", cpu);
39 err = xenbus_scanf(XBT_NIL, dir, "availability", "%15s", state);
40 if (err != 1) {
41 if (!xen_initial_domain())
42 pr_err("Unable to read cpu state\n");
43 return err;
44 }
45
46 if (strcmp(state, "online") == 0)
47 return 1;
48 else if (strcmp(state, "offline") == 0)
49 return 0;
50
51 pr_err("unknown state(%s) on CPU%d\n", state, cpu);
52 return -EINVAL;
53}
54static void vcpu_hotplug(unsigned int cpu)
55{
56 if (!cpu_possible(cpu))
57 return;
58
59 switch (vcpu_online(cpu)) {
60 case 1:
61 enable_hotplug_cpu(cpu);
62 break;
63 case 0:
64 disable_hotplug_cpu(cpu);
65 break;
66 default:
67 break;
68 }
69}
70
71static void handle_vcpu_hotplug_event(struct xenbus_watch *watch,
72 const char *path, const char *token)
73{
74 unsigned int cpu;
75 char *cpustr;
76
77 cpustr = strstr(path, "cpu/");
78 if (cpustr != NULL) {
79 sscanf(cpustr, "cpu/%u", &cpu);
80 vcpu_hotplug(cpu);
81 }
82}
83
84static int setup_cpu_watcher(struct notifier_block *notifier,
85 unsigned long event, void *data)
86{
87 int cpu;
88 static struct xenbus_watch cpu_watch = {
89 .node = "cpu",
90 .callback = handle_vcpu_hotplug_event};
91
92 (void)register_xenbus_watch(&cpu_watch);
93
94 for_each_possible_cpu(cpu) {
95 if (vcpu_online(cpu) == 0) {
96 (void)cpu_down(cpu);
97 set_cpu_present(cpu, false);
98 }
99 }
100
101 return NOTIFY_DONE;
102}
103
104static int __init setup_vcpu_hotplug_event(void)
105{
106 static struct notifier_block xsn_cpu = {
107 .notifier_call = setup_cpu_watcher };
108
109#ifdef CONFIG_X86
110 if (!xen_pv_domain() && !xen_pvh_domain())
111#else
112 if (!xen_domain())
113#endif
114 return -ENODEV;
115
116 register_xenstore_notifier(&xsn_cpu);
117
118 return 0;
119}
120
121arch_initcall(setup_vcpu_hotplug_event);
122