[tip:x86/apic] x86/ioapic: Ignore root bridges without a companion ACPI device

[tip-bot for Rui Wang]

Commit-ID:  d9c149d6ce1a94de578a4e323f6881fcb6b986ab
Gitweb:     http://git.kernel.org/tip/d9c149d6ce1a94de578a4e323f6881fcb6b986ab
Author:     Rui Wang <rui.y.wang@xxxxxxxxx>
AuthorDate: Sat, 10 Sep 2016 23:40:45 +0800
Committer:  Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Sat, 10 Sep 2016 20:30:31 +0200

x86/ioapic: Ignore root bridges without a companion ACPI device

Some PCI root bridges don't have a corresponding ACPI device.
This can be the case on some old platforms. Don't call acpi_ioapic_add()
on these bridges because they can't support ioapic hotplug.

Reported-and-tested-by: Borislav Petkov <bp@xxxxxxx>
Signed-off-by: Rui Wang <rui.y.wang@xxxxxxxxx>
Reviewed-by: Borislav Petkov <bp@xxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: bhelgaas@xxxxxxxxxx
Cc: helgaas@xxxxxxxxxx
Cc: linux-acpi@xxxxxxxxxxxxxxx
Cc: linux-pci@xxxxxxxxxxxxxxx
Cc: rjw@xxxxxxxxxxxxx
Cc: tony.luck@xxxxxxxxx
Link: http://lkml.kernel.org/r/1473522046-31329-1-git-send-email-rui.y.wang@xxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
 drivers/pci/setup-bus.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/pci/setup-bus.c b/drivers/pci/setup-bus.c
index ec538d3..f30ca75 100644
--- a/drivers/pci/setup-bus.c
+++ b/drivers/pci/setup-bus.c
@@ -1855,7 +1855,10 @@ void __init pci_assign_unassigned_resources(void)
 
 	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));
+
+		/* Make sure the root bridge has a companion ACPI device: */
+		if (ACPI_HANDLE(root_bus->bridge))
+			acpi_ioapic_add(ACPI_HANDLE(root_bus->bridge));
 	}
 }