1 files changed, 26 insertions, 5 deletions

diff --git a/drivers/iommu/amd_iommu.c b/drivers/iommu/amd_iommu.c
index 6d1cbdfc9b2a..e89daf1b21b4 100644
--- a/drivers/iommu/amd_iommu.c
+++ b/drivers/iommu/amd_iommu.c
@@ -266,7 +266,7 @@ static void swap_pci_ref(struct pci_dev **from, struct pci_dev *to)
 
 static int iommu_init_device(struct device *dev)
 {
-	struct pci_dev *dma_pdev, *pdev = to_pci_dev(dev);
+	struct pci_dev *dma_pdev = NULL, *pdev = to_pci_dev(dev);
 	struct iommu_dev_data *dev_data;
 	struct iommu_group *group;
 	u16 alias;
@@ -293,11 +293,18 @@ static int iommu_init_device(struct device *dev)
 		dev_data->alias_data = alias_data;
 
 		dma_pdev = pci_get_bus_and_slot(alias >> 8, alias & 0xff);
-	} else
+	}
+
+	if (dma_pdev == NULL)
 		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,
@@ -305,14 +312,28 @@ static int iommu_init_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) {