Patch "iommu/vt-d: Fix ATSR handling for Root-Complex integrated endpoints" has been added to the 4.3-stable tree

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

iommu/vt-d: Fix ATSR handling for Root-Complex integrated endpoints

to the 4.3-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-atsr-handling-for-root-complex-integrated-endpoints.patch
and it can be found in the queue-4.3 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: Thu, 15 Oct 2015 09:28:06 +0100
Subject: iommu/vt-d: Fix ATSR handling for Root-Complex integrated endpoints
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From: David Woodhouse <[email protected]>

commit d14053b3c714178525f22660e6aaf41263d00056 upstream.

The VT-d specification says that "Software must enable ATS on endpoint devices behind a Root Port only if the Root Port is reported as supporting ATS transactions."

We walk up the tree to find a Root Port, but for integrated devices we don't find one — we get to the host bridge. In that case we *should* allow ATS. Currently we don't, which means that we are incorrectly failing to use ATS for the integrated graphics. Fix that.

We should never break out of this loop "naturally" with bus==NULL, since we'll always find bridge==NULL in that case (and now return 1).

So remove the check for (!bridge) after the loop, since it can never happen. If it did, it would be worthy of a BUG_ON(!bridge). But since it'll oops anyway in that case, that'll do just as well.

---
 drivers/iommu/intel-iommu.c |    9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

@@ -4194,14 +4194,17 @@ int dmar_find_matched_atsr_unit(struct p
 	dev = pci_physfn(dev);
 	for (bus = dev->bus; bus; bus = bus->parent) {
 		bridge = bus->self;
-		if (!bridge || !pci_is_pcie(bridge) ||
+		/* If it's an integrated device, allow ATS */
+		if (!bridge)
+			return 1;
+		/* Connected via non-PCIe: no ATS */
+		if (!pci_is_pcie(bridge) ||
 		    pci_pcie_type(bridge) == PCI_EXP_TYPE_PCI_BRIDGE)
 			return 0;
+		/* If we found the root port, look it up in the ATSR */
 		if (pci_pcie_type(bridge) == PCI_EXP_TYPE_ROOT_PORT)
 			break;
 	}
-	if (!bridge)
-		return 0;
 
 	rcu_read_lock();
 	list_for_each_entry_rcu(atsru, &dmar_atsr_units, list) {

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

queue-4.3/iommu-vt-d-fix-atsr-handling-for-root-complex-integrated-endpoints.patch