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

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@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
index d65cf42399e8e5aa0f856a1ab6869c041adc0c48..dfc64662b386bf7f1909198bf759655050422aa2 100644 (file)
--- a/drivers/iommu/intel-iommu.c
+++ b/drivers/iommu/intel-iommu.c
@@ -4194,14 +4194,17 @@ 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) {