[PATCH V4 1/3] x86/ioapic: Support hot-removal of IOAPICs present during boot

[Rui Wang <rui.y.wang@intel.com>]

v4: Add comments explaining when to call acpi_ioapic_add().
v3: Previous versions break mips. This version fixes it.

IOAPICs present during system boot aren't added to ioapic_list,
thus are unable to be hot-removed. Fix it by calling
acpi_ioapic_add() during root bus enumeration.

Signed-off-by: Rui Wang <rui.y.wang@intel.com>
---
 drivers/acpi/internal.h |  2 --
 drivers/acpi/ioapic.c   |  7 ++++---
 drivers/acpi/pci_root.c | 13 ++++++++++++-
 drivers/pci/setup-bus.c |  7 ++++++-
 include/linux/acpi.h    |  3 +++
 5 files changed, 25 insertions(+), 7 deletions(-)

diff --git a/drivers/acpi/internal.h b/drivers/acpi/internal.h
index 27cc7fe..6d8e67e 100644
--- a/drivers/acpi/internal.h
+++ b/drivers/acpi/internal.h
@@ -40,10 +40,8 @@ int acpi_sysfs_init(void);
 void acpi_container_init(void);
 void acpi_memory_hotplug_init(void);
 #ifdef	CONFIG_ACPI_HOTPLUG_IOAPIC
-int acpi_ioapic_add(struct acpi_pci_root *root);
 int acpi_ioapic_remove(struct acpi_pci_root *root);
 #else
-static inline int acpi_ioapic_add(struct acpi_pci_root *root) { return 0; }
 static inline int acpi_ioapic_remove(struct acpi_pci_root *root) { return 0; }
 #endif
 #ifdef CONFIG_ACPI_DOCK
diff --git a/drivers/acpi/ioapic.c b/drivers/acpi/ioapic.c
index ccdc8db..0f272e2 100644
--- a/drivers/acpi/ioapic.c
+++ b/drivers/acpi/ioapic.c
@@ -189,16 +189,17 @@ exit:
 	return AE_OK;
 }
 
-int acpi_ioapic_add(struct acpi_pci_root *root)
+int acpi_ioapic_add(acpi_handle root_handle)
 {
 	acpi_status status, retval = AE_OK;
 
-	status = acpi_walk_namespace(ACPI_TYPE_DEVICE, root->device->handle,
+	status = acpi_walk_namespace(ACPI_TYPE_DEVICE, root_handle,
 				     UINT_MAX, handle_ioapic_add, NULL,
-				     root->device->handle, (void **)&retval);
+				     root_handle, (void **)&retval);
 
 	return ACPI_SUCCESS(status) && ACPI_SUCCESS(retval) ? 0 : -ENODEV;
 }
+EXPORT_SYMBOL_GPL(acpi_ioapic_add);
 
 int acpi_ioapic_remove(struct acpi_pci_root *root)
 {
diff --git a/drivers/acpi/pci_root.c b/drivers/acpi/pci_root.c
index ae3fe4e..31e4440 100644
--- a/drivers/acpi/pci_root.c
+++ b/drivers/acpi/pci_root.c
@@ -614,7 +614,18 @@ static int acpi_pci_root_add(struct acpi_device *device,
 	if (hotadd) {
 		pcibios_resource_survey_bus(root->bus);
 		pci_assign_unassigned_root_bus_resources(root->bus);
-		acpi_ioapic_add(root);
+
+		/*
+ 		 * This is only called for the hotadd case. For the boot-time
+ 		 * case, we need to wait until after PCI initialization in
+ 		 * order to deal with IOAPICs mapped in on a PCI BAR.
+ 		 *
+ 		 * This is currently x86-specific, because acpi_ioapic_add()
+ 		 * is an empty function without CONFIG_ACPI_HOTPLUG_IOAPIC.
+ 		 * And CONFIG_ACPI_HOTPLUG_IOAPIC depends on CONFIG_X86_IO_APIC
+ 		 * (see drivers/acpi/Kconfig).
+ 		 */
+		acpi_ioapic_add(root->device->handle);
 	}
 
 	pci_lock_rescan_remove();
diff --git a/drivers/pci/setup-bus.c b/drivers/pci/setup-bus.c
index 55641a3..0658921 100644
--- a/drivers/pci/setup-bus.c
+++ b/drivers/pci/setup-bus.c
@@ -25,6 +25,7 @@
 #include <linux/ioport.h>
 #include <linux/cache.h>
 #include <linux/slab.h>
+#include <linux/acpi.h>
 #include "pci.h"
 
 unsigned int pci_flags;
@@ -1779,8 +1780,12 @@ void __init pci_assign_unassigned_resources(void)
 {
 	struct pci_bus *root_bus;
 
-	list_for_each_entry(root_bus, &pci_root_buses, node)
+	list_for_each_entry(root_bus, &pci_root_buses, node) {
 		pci_assign_unassigned_root_bus_resources(root_bus);
+#ifdef CONFIG_X86
+		acpi_ioapic_add(ACPI_HANDLE(root_bus->bridge));
+#endif
+	}
 }
 
 void pci_assign_unassigned_bridge_resources(struct pci_dev *bridge)
diff --git a/include/linux/acpi.h b/include/linux/acpi.h
index 288fac5..3ed22df 100644
--- a/include/linux/acpi.h
+++ b/include/linux/acpi.h
@@ -262,6 +262,9 @@ int acpi_unmap_cpu(int cpu);
 
 #ifdef CONFIG_ACPI_HOTPLUG_IOAPIC
 int acpi_get_ioapic_id(acpi_handle handle, u32 gsi_base, u64 *phys_addr);
+int acpi_ioapic_add(acpi_handle root);
+#else
+static inline int acpi_ioapic_add(acpi_handle root) { return 0; }
 #endif
 
 int acpi_register_ioapic(acpi_handle handle, u64 phys_addr, u32 gsi_base);
-- 
1.8.3.1