iommu/amd: Initialize dma_ops for hotplug and sriov devices

commit ac1534a5 upstream.

When a device is added to the system at runtime the AMD
IOMMU driver initializes the necessary data structures to
handle translation for it. But it forgets to change the
per-device dma_ops to point to the AMD IOMMU driver. So
mapping actually never happens and all DMA accesses end in
an IO_PAGE_FAULT. Fix this.
Reported-by: Stefan Assmann <sassmann@redhat.com>
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
[bwh: Backported to 3.2:
 - Adjust context
 - Use global iommu_pass_through; there is no per-device pass_through]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

drivers/iommu/amd_iommu.c

@@ -59,6 +59,8 @@ static struct protection_domain *pt_domain;
 
 static struct iommu_ops amd_iommu_ops;
 
+static struct dma_map_ops amd_iommu_dma_ops;
+
 /*
  * general struct to manage commands send to an IOMMU
  */
@@ -1878,6 +1880,11 @@ static int device_change_notifier(struct notifier_block *nb,
 		list_add_tail(&dma_domain->list, &iommu_pd_list);
 		spin_unlock_irqrestore(&iommu_pd_list_lock, flags);
 
+		if (!iommu_pass_through)
+			dev->archdata.dma_ops = &amd_iommu_dma_ops;
+		else
+			dev->archdata.dma_ops = &nommu_dma_ops;
+
 		break;
 	case BUS_NOTIFY_DEL_DEVICE: