iommu/amd: Make sure dma_ops are set for hotplug devices

commit c2a2876e upstream.

There is a bug introduced with commit 27c2127 that causes
devices which are hot unplugged and then hot-replugged to
not have per-device dma_ops set. This causes these devices
to not function correctly. Fixed with this patch.
Reported-by: Andreas Degert <andreas.degert@googlemail.com>
Signed-off-by: Joerg Roedel <joro@8bytes.org>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

drivers/iommu/amd_iommu.c

@@ -1874,16 +1874,16 @@ static int device_change_notifier(struct notifier_block *nb,
 
 		/* allocate a protection domain if a device is added */
 		dma_domain = find_protection_domain(devid);
-		if (dma_domain)
-			goto out;
-		dma_domain = dma_ops_domain_alloc();
-		if (!dma_domain)
-			goto out;
-		dma_domain->target_dev = devid;
-
-		spin_lock_irqsave(&iommu_pd_list_lock, flags);
-		list_add_tail(&dma_domain->list, &iommu_pd_list);
-		spin_unlock_irqrestore(&iommu_pd_list_lock, flags);
+		if (!dma_domain) {
+			dma_domain = dma_ops_domain_alloc();
+			if (!dma_domain)
+				goto out;
+			dma_domain->target_dev = devid;
+
+			spin_lock_irqsave(&iommu_pd_list_lock, flags);
+			list_add_tail(&dma_domain->list, &iommu_pd_list);
+			spin_unlock_irqrestore(&iommu_pd_list_lock, flags);
+		}
 
 		dev->archdata.dma_ops = &amd_iommu_dma_ops;