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 12 static 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 20 static void disable_hotplug_cpu(int cpu) 21 { 22 if (!cpu_is_hotpluggable(cpu)) 23 return; 24 lock_device_hotplug(); 25 if (cpu_online(cpu)) 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); 30 } 31 unlock_device_hotplug(); 32 } 33 34 static int vcpu_online(unsigned int cpu) 35 { 36 int err; 37 char dir[16], state[16]; 38 39 sprintf(dir, "cpu/%u", cpu); 40 err = xenbus_scanf(XBT_NIL, dir, "availability", "%15s", state); 41 if (err != 1) { 42 if (!xen_initial_domain()) 43 pr_err("Unable to read cpu state\n"); 44 return err; 45 } 46 47 if (strcmp(state, "online") == 0) 48 return 1; 49 else if (strcmp(state, "offline") == 0) 50 return 0; 51 52 pr_err("unknown state(%s) on CPU%d\n", state, cpu); 53 return -EINVAL; 54 } 55 static void vcpu_hotplug(unsigned int cpu) 56 { 57 if (cpu >= nr_cpu_ids || !cpu_possible(cpu)) 58 return; 59 60 switch (vcpu_online(cpu)) { 61 case 1: 62 enable_hotplug_cpu(cpu); 63 break; 64 case 0: 65 disable_hotplug_cpu(cpu); 66 break; 67 default: 68 break; 69 } 70 } 71 72 static void handle_vcpu_hotplug_event(struct xenbus_watch *watch, 73 const char *path, const char *token) 74 { 75 unsigned int cpu; 76 char *cpustr; 77 78 cpustr = strstr(path, "cpu/"); 79 if (cpustr != NULL) { 80 sscanf(cpustr, "cpu/%u", &cpu); 81 vcpu_hotplug(cpu); 82 } 83 } 84 85 static int setup_cpu_watcher(struct notifier_block *notifier, 86 unsigned long event, void *data) 87 { 88 int cpu; 89 static struct xenbus_watch cpu_watch = { 90 .node = "cpu", 91 .callback = handle_vcpu_hotplug_event}; 92 93 (void)register_xenbus_watch(&cpu_watch); 94 95 for_each_possible_cpu(cpu) { 96 if (vcpu_online(cpu) == 0) 97 disable_hotplug_cpu(cpu); 98 } 99 100 return NOTIFY_DONE; 101 } 102 103 static int __init setup_vcpu_hotplug_event(void) 104 { 105 static struct notifier_block xsn_cpu = { 106 .notifier_call = setup_cpu_watcher }; 107 108 #ifdef CONFIG_X86 109 if (!xen_pv_domain() && !xen_pvh_domain()) 110 #else 111 if (!xen_domain()) 112 #endif 113 return -ENODEV; 114 115 register_xenstore_notifier(&xsn_cpu); 116 117 return 0; 118 } 119 120 late_initcall(setup_vcpu_hotplug_event); 121 122