[4.2.y-ckt stable] Patch "iommu/vt-d: Fix ATSR handling for Root-Complex integrated endpoints" has been added to staging queue

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

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

to the linux-4.2.y-queue branch of the 4.2.y-ckt extended stable tree 
which can be found at:

    http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-4.2.y-queue

This patch is scheduled to be released in version 4.2.8-ckt1.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 4.2.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From fe1f2d39900624c044f8e346aaeab6579eeb86d0 Mon Sep 17 00:00:00 2001
From: David Woodhouse <David.Woodhouse at intel.com>
Date: Thu, 15 Oct 2015 09:28:06 +0100
Subject: iommu/vt-d: Fix ATSR handling for Root-Complex integrated endpoints
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

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.

Signed-off-by: David Woodhouse <David.Woodhouse at intel.com>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 drivers/iommu/intel-iommu.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
index bd1b8ad..66e94b8 100644
--- a/drivers/iommu/intel-iommu.c
+++ b/drivers/iommu/intel-iommu.c
@@ -4231,14 +4231,17 @@ int dmar_find_matched_atsr_unit(struct pci_dev *dev)
 	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) {
--
1.9.1