During ioapic hotplug, acpi_register_ioapic will be called.
Now for x86, that function is blank.
Fill that will update __mp_register_ioapic to use those ioapic.

Signed-off-by: Yinghai Lu <yinghai@kernel.org>
---
 arch/x86/kernel/acpi/boot.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kernel/acpi/boot.c b/arch/x86/kernel/acpi/boot.c
index 5be15d1..4a5336d 100644
--- a/arch/x86/kernel/acpi/boot.c
+++ b/arch/x86/kernel/acpi/boot.c
@@ -707,16 +707,18 @@ EXPORT_SYMBOL(acpi_unmap_lsapic);
 
 int acpi_register_ioapic(acpi_handle handle, u64 phys_addr, u32 gsi_base)
 {
-	/* TBD */
-	return -EINVAL;
+	unsigned long long id = 0;
+
+	acpi_evaluate_integer(handle, "_UID", NULL, &id);
+
+	return	__mp_register_ioapic(id, phys_addr, gsi_base, true);
 }
 
 EXPORT_SYMBOL(acpi_register_ioapic);
 
 int acpi_unregister_ioapic(acpi_handle handle, u32 gsi_base)
 {
-	/* TBD */
-	return -EINVAL;
+	return mp_unregister_ioapic(gsi_base);
 }
 
 EXPORT_SYMBOL(acpi_unregister_ioapic);
-- 
1.8.1.4