From 44cd613c0e4cd93079ea2a93aa06649d8ca0830a Mon Sep 17 00:00:00 2001
From: David Woodhouse <David.Woodhouse@intel.com>
Date: Wed, 2 Dec 2009 10:18:30 +0000
Subject: [PATCH] intel-iommu: Fix oops with intel_iommu=igfx_off

The hotplug notifier will call find_domain() to see if the device in
question has been assigned an IOMMU domain. However, this should never
be called for devices with a "dummy" domain, such as graphics devices
when intel_iommu=igfx_off is set and the corresponding IOMMU isn't even
initialised. If you do that, it'll oops as it dereferences the (-1)
pointer.

The notifier function should check iommu_no_mapping() for the
device before doing anything else.

Cc: stable@kernel.org
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
---
 drivers/pci/intel-iommu.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/pci/intel-iommu.c b/drivers/pci/intel-iommu.c
index 83cabdc118db..e3e84cac0e98 100644
--- a/drivers/pci/intel-iommu.c
+++ b/drivers/pci/intel-iommu.c
@@ -3247,6 +3247,9 @@ static int device_notifier(struct notifier_block *nb,
 	struct pci_dev *pdev = to_pci_dev(dev);
 	struct dmar_domain *domain;
 
+	if (iommu_no_mapping(dev))
+		return 0;
+
 	domain = find_domain(pdev);
 	if (!domain)
 		return 0;