1 files changed, 25 insertions, 0 deletions

diff --git a/drivers/iommu/amd_iommu.c b/drivers/iommu/amd_iommu.c
index 60ea92065d31..49172393d6ec 100644
--- a/drivers/iommu/amd_iommu.c
+++ b/drivers/iommu/amd_iommu.c
@@ -254,6 +254,14 @@ static bool check_device(struct device *dev)
         return true;
 }
 
+static void swap_pci_ref(struct pci_dev **from, struct pci_dev *to)
+{
+        pci_dev_put(*from);
+        *from = to;
+}
+
+#define REQ_ACS_FLAGS   (PCI_ACS_SV | PCI_ACS_RR | PCI_ACS_CR | PCI_ACS_UF)
+
 static int iommu_init_device(struct device *dev)
 {
         struct pci_dev *dma_pdev, *pdev = to_pci_dev(dev);
@@ -286,6 +294,23 @@ static int iommu_init_device(struct device *dev)
         } else
                 dma_pdev = pci_dev_get(pdev);
 
+        swap_pci_ref(&dma_pdev, pci_get_dma_source(dma_pdev));
+
+        if (dma_pdev->multifunction &&
+            !pci_acs_enabled(dma_pdev, REQ_ACS_FLAGS))
+                swap_pci_ref(&dma_pdev,
+                             pci_get_slot(dma_pdev->bus,
+                                          PCI_DEVFN(PCI_SLOT(dma_pdev->devfn),
+                                          0)));
+
+        while (!pci_is_root_bus(dma_pdev->bus)) {
+                if (pci_acs_path_enabled(dma_pdev->bus->self,
+                                         NULL, REQ_ACS_FLAGS))
+                        break;
+
+                swap_pci_ref(&dma_pdev, pci_dev_get(dma_pdev->bus->self));
+        }
+
         group = iommu_group_get(&dma_pdev->dev);
         pci_dev_put(dma_pdev);
         if (!group) {