[tip:x86/apic] x86/ioapic: Support hot-removal of IOAPICs present during boot

[tip-bot for Rui Wang <tipbot@zytor.com>]

Commit-ID:  584c5c422f6c749ced1e0bc3c6837f650f64e1e1
Gitweb:     http://git.kernel.org/tip/584c5c422f6c749ced1e0bc3c6837f650f64e1e1
Author:     Rui Wang <rui.y.wang@intel.com>
AuthorDate: Wed, 17 Aug 2016 16:00:34 +0800
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Thu, 18 Aug 2016 11:45:18 +0200

x86/ioapic: Support hot-removal of IOAPICs present during boot

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>
Acked-by: Bjorn Helgaas <bhelgaas@google.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: helgaas@kernel.org
Cc: linux-acpi@vger.kernel.org
Cc: linux-pci@vger.kernel.org
Cc: rjw@rjwysocki.net
Cc: tony.luck@intel.com
Link: http://lkml.kernel.org/r/1471420837-31003-3-git-send-email-rui.y.wang@intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 drivers/acpi/pci_root.c | 10 ++++++++++
 drivers/pci/setup-bus.c |  5 ++++-
 2 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/drivers/acpi/pci_root.c b/drivers/acpi/pci_root.c
index b07eda1..bf601d4 100644
--- a/drivers/acpi/pci_root.c
+++ b/drivers/acpi/pci_root.c
@@ -614,6 +614,16 @@ 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);
+		/*
+		 * 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);
 	}
 
diff --git a/drivers/pci/setup-bus.c b/drivers/pci/setup-bus.c
index c74059e..ec538d3 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;
@@ -1852,8 +1853,10 @@ 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);
+		acpi_ioapic_add(ACPI_HANDLE(root_bus->bridge));
+	}
 }
 
 void pci_assign_unassigned_bridge_resources(struct pci_dev *bridge)