1 files changed, 57 insertions, 2 deletions

diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c
index ad9c719bd078..5e18fbcee9a2 100644
--- a/arch/arm64/kernel/smp.c
+++ b/arch/arm64/kernel/smp.c
@@ -129,7 +129,8 @@ int __cpu_up(unsigned int cpu, struct task_struct *idle)
 	/* Now bring the CPU into our world */
 	ret = boot_secondary(cpu, idle);
 	if (ret) {
-		pr_err("CPU%u: failed to boot: %d\n", cpu, ret);
+		if (ret != -EPERM)
+			pr_err("CPU%u: failed to boot: %d\n", cpu, ret);
 		return ret;
 	}
 
@@ -507,6 +508,59 @@ 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];
 
@@ -527,7 +581,8 @@ acpi_map_gic_cpu_interface(struct acpi_madt_generic_interrupt *processor)
 {
 	u64 hwid = processor->arm_mpidr;
 
-	if (!acpi_gicc_is_usable(processor)) {
+	if (!(processor->flags &
+	      (ACPI_MADT_ENABLED | ACPI_MADT_GICC_ONLINE_CAPABLE))) {
 		pr_debug("skipping disabled CPU entry with 0x%llx MPIDR\n", hwid);
 		return;
 	}