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