1 #include <linux/notifier.h> 2 3 #include <xen/xenbus.h> 4 5 #include <asm/xen/hypervisor.h> 6 #include <asm/cpu.h> 7 8 static void enable_hotplug_cpu(int cpu) 9 { 10 if (!cpu_present(cpu)) 11 arch_register_cpu(cpu); 12 13 cpu_set(cpu, cpu_present_map); 14 } 15 16 static void disable_hotplug_cpu(int cpu) 17 { 18 if (cpu_present(cpu)) 19 arch_unregister_cpu(cpu); 20 21 cpu_clear(cpu, cpu_present_map); 22 } 23 24 static void vcpu_hotplug(unsigned int cpu) 25 { 26 int err; 27 char dir[32], state[32]; 28 29 if (!cpu_possible(cpu)) 30 return; 31 32 sprintf(dir, "cpu/%u", cpu); 33 err = xenbus_scanf(XBT_NIL, dir, "availability", "%s", state); 34 if (err != 1) { 35 printk(KERN_ERR "XENBUS: Unable to read cpu state\n"); 36 return; 37 } 38 39 if (strcmp(state, "online") == 0) { 40 enable_hotplug_cpu(cpu); 41 } else if (strcmp(state, "offline") == 0) { 42 (void)cpu_down(cpu); 43 disable_hotplug_cpu(cpu); 44 } else { 45 printk(KERN_ERR "XENBUS: unknown state(%s) on CPU%d\n", 46 state, cpu); 47 } 48 } 49 50 static void handle_vcpu_hotplug_event(struct xenbus_watch *watch, 51 const char **vec, unsigned int len) 52 { 53 unsigned int cpu; 54 char *cpustr; 55 const char *node = vec[XS_WATCH_PATH]; 56 57 cpustr = strstr(node, "cpu/"); 58 if (cpustr != NULL) { 59 sscanf(cpustr, "cpu/%u", &cpu); 60 vcpu_hotplug(cpu); 61 } 62 } 63 64 static int setup_cpu_watcher(struct notifier_block *notifier, 65 unsigned long event, void *data) 66 { 67 static struct xenbus_watch cpu_watch = { 68 .node = "cpu", 69 .callback = handle_vcpu_hotplug_event}; 70 71 (void)register_xenbus_watch(&cpu_watch); 72 73 return NOTIFY_DONE; 74 } 75 76 static int __init setup_vcpu_hotplug_event(void) 77 { 78 static struct notifier_block xsn_cpu = { 79 .notifier_call = setup_cpu_watcher }; 80 81 if (!xen_pv_domain()) 82 return -ENODEV; 83 84 register_xenstore_notifier(&xsn_cpu); 85 86 return 0; 87 } 88 89 arch_initcall(setup_vcpu_hotplug_event); 90 91