linux-kernel - [PATCH] x86/ioapic: Ignore root bridges without a companion ACPI device

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Date:   Sat, 10 Sep 2016 23:40:45 +0800
From:   Rui Wang <rui.y.wang@...el.com>
To:     bhelgaas@...gle.com, tglx@...utronix.de, rjw@...ysocki.net,
        mingo@...nel.org, bp@...en8.de
Cc:     torvalds@...ux-foundation.org, peterz@...radead.org,
        helgaas@...nel.org, linux-acpi@...r.kernel.org,
        linux-pci@...r.kernel.org, tony.luck@...el.com, x86@...nel.org,
        linux-kernel@...r.kernel.org, rui.y.wang@...el.com
Subject: [PATCH] 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.

v2: Per Boris's review, removed the unnecessary local var; refined comment

Signed-off-by: Rui Wang <rui.y.wang@...el.com>
Reviewed-by: Borislav Petkov <bp@...en8.de>
---
 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..8b4e231 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));
 	}
 }
 
-- 
1.8.3.1