@@ -504,6 +504,59 @@ static int __init smp_cpu_setup(int cpu)
static bool bootcpu_valid __initdata;
static unsigned int cpu_count = 1;
+int arch_register_cpu(int cpu)
+{
+ acpi_handle acpi_handle = acpi_get_processor_handle(cpu);
+ struct cpu *c = &per_cpu(cpu_devices, cpu);
+
+ if (!acpi_disabled && !acpi_handle &&
+ IS_ENABLED(CONFIG_ACPI_HOTPLUG_CPU))
+ return -EPROBE_DEFER;
+
+#ifdef CONFIG_ACPI_HOTPLUG_CPU
+ /* For now block anything that looks like physical CPU Hotplug */
+ if (invalid_logical_cpuid(cpu) || !cpu_present(cpu)) {
+ pr_err_once("Changing CPU present bit is not supported\n");
+ return -ENODEV;
+ }
+#endif
+
+ /*
+ * Availability of the acpi handle is sufficient to establish
+ * that _STA has aleady been checked. No need to recheck here.
+ */
+ c->hotpluggable = arch_cpu_is_hotpluggable(cpu);
+
+ return register_cpu(c, cpu);
+}
+
+#ifdef CONFIG_ACPI_HOTPLUG_CPU
+void arch_unregister_cpu(int cpu)
+{
+ acpi_handle acpi_handle = acpi_get_processor_handle(cpu);
+ struct cpu *c = &per_cpu(cpu_devices, cpu);
+ acpi_status status;
+ unsigned long long sta;
+
+ if (!acpi_handle) {
+ pr_err_once("Removing a CPU without associated ACPI handle\n");
+ return;
+ }
+
+ status = acpi_evaluate_integer(acpi_handle, "_STA", NULL, &sta);
+ if (ACPI_FAILURE(status))
+ return;
+
+ /* For now do not allow anything that looks like physical CPU HP */
+ if (cpu_present(cpu) && !(sta & ACPI_STA_DEVICE_PRESENT)) {
+ pr_err_once("Changing CPU present bit is not supported\n");
+ return;
+ }
+
+ unregister_cpu(c);
+}
+#endif /* CONFIG_ACPI_HOTPLUG_CPU */
+
#ifdef CONFIG_ACPI
static struct acpi_madt_generic_interrupt cpu_madt_gicc[NR_CPUS];