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