iommu/intel: Fix ACS path checking

SR-IOV can create buses without a bridge.  There may be other cases
where this happens as well.  In these cases skip to the parent bus
and continue testing devices there.

Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Tested-by: David Ahern <dsahern@gmail.com>
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>

diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
index 0204b62..2297ec1 100644 (file)
--- a/drivers/iommu/intel-iommu.c
+++ b/drivers/iommu/intel-iommu.c
@@ -4125,8 +4125,13 @@ static int intel_iommu_add_device(struct device *dev)
        } else
                dma_pdev = pci_dev_get(pdev);
 
+       /* Account for quirked devices */
        swap_pci_ref(&dma_pdev, pci_get_dma_source(dma_pdev));
 
+       /*
+        * If it's a multifunction device that does not support our
+        * required ACS flags, add to the same group as function 0.
+        */
        if (dma_pdev->multifunction &&
            !pci_acs_enabled(dma_pdev, REQ_ACS_FLAGS))
                swap_pci_ref(&dma_pdev,
@@ -4134,14 +4139,28 @@ static int intel_iommu_add_device(struct device *dev)
                                          PCI_DEVFN(PCI_SLOT(dma_pdev->devfn),
                                          0)));
 
+       /*
+        * Devices on the root bus go through the iommu.  If that's not us,
+        * find the next upstream device and test ACS up to the root bus.
+        * Finding the next device may require skipping virtual buses.
+        */
        while (!pci_is_root_bus(dma_pdev->bus)) {
-               if (pci_acs_path_enabled(dma_pdev->bus->self,
-                                        NULL, REQ_ACS_FLAGS))
+               struct pci_bus *bus = dma_pdev->bus;
+
+               while (!bus->self) {
+                       if (!pci_is_root_bus(bus))
+                               bus = bus->parent;
+                       else
+                               goto root_bus;
+               }
+
+               if (pci_acs_path_enabled(bus->self, NULL, REQ_ACS_FLAGS))
                        break;
 
-               swap_pci_ref(&dma_pdev, pci_dev_get(dma_pdev->bus->self));
+               swap_pci_ref(&dma_pdev, pci_dev_get(bus->self));
        }
 
+root_bus:
        group = iommu_group_get(&dma_pdev->dev);
        pci_dev_put(dma_pdev);
        if (!group) {