// SPDX-License-Identifier: GPL-2.0 #define pr_fmt(fmt) "xen:" KBUILD_MODNAME ": " fmt #include <linux/notifier.h> #include <xen/xen.h> #include <xen/xenbus.h> #include <asm/xen/hypervisor.h> #include <asm/cpu.h> static void enable_hotplug_cpu(int cpu) { if (!cpu_present(cpu)) xen_arch_register_cpu(cpu); set_cpu_present(cpu, true); } static void disable_hotplug_cpu(int cpu) { if (!cpu_is_hotpluggable(cpu)) return; lock_device_hotplug(); if (cpu_online(cpu)) device_offline(get_cpu_device(cpu)); if (!cpu_online(cpu) && cpu_present(cpu)) { xen_arch_unregister_cpu(cpu); set_cpu_present(cpu, false); } unlock_device_hotplug(); } static int vcpu_online(unsigned int cpu) { int err; char dir[16], state[16]; sprintf(dir, "cpu/%u", cpu); err = xenbus_scanf(XBT_NIL, dir, "availability", "%15s", state); if (err != 1) { if (!xen_initial_domain()) pr_err("Unable to read cpu state\n"); return err; } if (strcmp(state, "online") == 0) return 1; else if (strcmp(state, "offline") == 0) return 0; pr_err("unknown state(%s) on CPU%d\n", state, cpu); return -EINVAL; } static void vcpu_hotplug(unsigned int cpu) { if (cpu >= nr_cpu_ids || !cpu_possible(cpu)) return; switch (vcpu_online(cpu)) { case 1: enable_hotplug_cpu(cpu); break; case 0: disable_hotplug_cpu(cpu); break; default: break; } } static void handle_vcpu_hotplug_event(struct xenbus_watch *watch, const char *path, const char *token) { unsigned int cpu; char *cpustr; cpustr = strstr(path, "cpu/"); if (cpustr != NULL) { sscanf(cpustr, "cpu/%u", &cpu); vcpu_hotplug(cpu); } } static int setup_cpu_watcher(struct notifier_block *notifier, unsigned long event, void *data) { int cpu; static struct xenbus_watch cpu_watch = { .node = "cpu", .callback = handle_vcpu_hotplug_event}; (void)register_xenbus_watch(&cpu_watch); for_each_possible_cpu(cpu) { if (vcpu_online(cpu) == 0) { (void)cpu_down(cpu); set_cpu_present(cpu, false); } } return NOTIFY_DONE; } static int __init setup_vcpu_hotplug_event(void) { static struct notifier_block xsn_cpu = { .notifier_call = setup_cpu_watcher }; #ifdef CONFIG_X86 if (!xen_pv_domain() && !xen_pvh_domain()) #else if (!xen_domain()) #endif return -ENODEV; register_xenstore_notifier(&xsn_cpu); return 0; } arch_initcall(setup_vcpu_hotplug_event);