Patch "iommu/vt-d: Fix passthrough mode with translation-disabled devices" has been added to the 4.0-stable tree

This is a note to let you know that I've just added the patch titled

iommu/vt-d: Fix passthrough mode with translation-disabled devices

to the 4.0-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
iommu-vt-d-fix-passthrough-mode-with-translation-disabled-devices.patch
and it can be found in the queue-4.0 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: David Woodhouse <[email protected]>
Date: Mon, 11 May 2015 14:59:20 +0100
Subject: iommu/vt-d: Fix passthrough mode with translation-disabled devices

From: David Woodhouse <[email protected]>

commit 4ed6a540fab8ea4388c1703b73ecfed68a2009d1 upstream.

When we use 'intel_iommu=igfx_off' to disable translation for the graphics, and when we discover that the BIOS has misconfigured the DMAR setup for I/OAT, we use a special DUMMY_DEVICE_DOMAIN_INFO value in dev->archdata.iommu to indicate that translation is disabled.

With passthrough mode, we were attempting to dereference that as a normal pointer to a struct device_domain_info when setting up an identity mapping for the affected device.

This fixes the problem by making device_to_iommu() explicitly check for the special value and indicate that no IOMMU was found to handle the devices in question.

---
 drivers/iommu/intel-iommu.c |   13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

@@ -673,6 +673,11 @@ static void domain_update_iommu_cap(stru
 	domain->iommu_superpage = domain_update_iommu_superpage(NULL);
 }
 
+static int iommu_dummy(struct device *dev)
+{
+	return dev->archdata.iommu == DUMMY_DEVICE_DOMAIN_INFO;
+}
+
 static struct intel_iommu *device_to_iommu(struct device *dev, u8 *bus, u8 *devfn)
 {
 	struct dmar_drhd_unit *drhd = NULL;

@@ -682,6 +687,9 @@ static struct intel_iommu *device_to_iom
 	u16 segment = 0;
 	int i;
 
+	if (iommu_dummy(dev))
+		return NULL;
+
 	if (dev_is_pci(dev)) {
 		pdev = to_pci_dev(dev);
 		segment = pci_domain_nr(pdev->bus);

@@ -2974,11 +2982,6 @@ static inline struct dmar_domain *get_va
 	return __get_valid_domain_for_dev(dev);
 }
 
-static int iommu_dummy(struct device *dev)
-{
-	return dev->archdata.iommu == DUMMY_DEVICE_DOMAIN_INFO;
-}
-
 /* Check if the dev needs to go through non-identity map and unmap process.*/
 static int iommu_no_mapping(struct device *dev)
 {

Patches currently in stable-queue which might be from [email protected] are

queue-4.0/iommu-vt-d-fix-passthrough-mode-with-translation-disabled-devices.patch queue-4.0/iommu-vt-d-allow-rmrr-on-graphics-devices-too.patch
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