122 lines · c
1// SPDX-License-Identifier: GPL-2.02#define pr_fmt(fmt) "xen:" KBUILD_MODNAME ": " fmt3 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_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 34static 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}55static 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 72static 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 85static 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 103static 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_X86109 if (!xen_pv_domain() && !xen_pvh_domain())110#else111 if (!xen_domain())112#endif113 return -ENODEV;114 115 register_xenstore_notifier(&xsn_cpu);116 117 return 0;118}119 120late_initcall(setup_vcpu_hotplug_event);121 122