diff --git a/drivers/iommu/arm-smmu-v3.c b/drivers/iommu/arm-smmu-v3.c
index 15c01c3cd540b6b0416002ca39c8a72951b3cc75..e6f9b2d745ca0eefbe02cb5e9c2680dcff60af46 100644
--- a/drivers/iommu/arm-smmu-v3.c
+++ b/drivers/iommu/arm-smmu-v3.c
@@ -2636,17 +2636,26 @@ static int arm_smmu_device_dt_probe(struct platform_device *pdev)
 	/* And we're up. Go go go! */
 	of_iommu_set_ops(dev->of_node, &arm_smmu_ops);
 #ifdef CONFIG_PCI
-	pci_request_acs();
-	ret = bus_set_iommu(&pci_bus_type, &arm_smmu_ops);
-	if (ret)
-		return ret;
+	if (pci_bus_type.iommu_ops != &arm_smmu_ops) {
+		pci_request_acs();
+		ret = bus_set_iommu(&pci_bus_type, &arm_smmu_ops);
+		if (ret)
+			return ret;
+	}
 #endif
 #ifdef CONFIG_ARM_AMBA
-	ret = bus_set_iommu(&amba_bustype, &arm_smmu_ops);
-	if (ret)
-		return ret;
+	if (amba_bustype.iommu_ops != &arm_smmu_ops) {
+		ret = bus_set_iommu(&amba_bustype, &arm_smmu_ops);
+		if (ret)
+			return ret;
+	}
 #endif
-	return bus_set_iommu(&platform_bus_type, &arm_smmu_ops);
+	if (platform_bus_type.iommu_ops != &arm_smmu_ops) {
+		ret = bus_set_iommu(&platform_bus_type, &arm_smmu_ops);
+		if (ret)
+			return ret;
+	}
+	return 0;
 }
 
 static int arm_smmu_device_remove(struct platform_device *pdev)
diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c
index c841eb7a1a7417af301e6c51a9ba464d05b1472a..8f7281444551dfc8a7b1a1bbfdb66a81f28e01ca 100644
--- a/drivers/iommu/arm-smmu.c
+++ b/drivers/iommu/arm-smmu.c
@@ -324,8 +324,10 @@ struct arm_smmu_master_cfg {
 #define INVALID_SMENDX			-1
 #define __fwspec_cfg(fw) ((struct arm_smmu_master_cfg *)fw->iommu_priv)
 #define fwspec_smmu(fw)  (__fwspec_cfg(fw)->smmu)
+#define fwspec_smendx(fw, i) \
+	(i >= fw->num_ids ? INVALID_SMENDX : __fwspec_cfg(fw)->smendx[i])
 #define for_each_cfg_sme(fw, i, idx) \
-	for (i = 0; idx = __fwspec_cfg(fw)->smendx[i], i < fw->num_ids; ++i)
+	for (i = 0; idx = fwspec_smendx(fw, i), i < fw->num_ids; ++i)
 
 struct arm_smmu_device {
 	struct device			*dev;
@@ -1228,6 +1230,16 @@ static int arm_smmu_attach_dev(struct iommu_domain *domain, struct device *dev)
 		return -ENXIO;
 	}
 
+	/*
+	 * FIXME: The arch/arm DMA API code tries to attach devices to its own
+	 * domains between of_xlate() and add_device() - we have no way to cope
+	 * with that, so until ARM gets converted to rely on groups and default
+	 * domains, just say no (but more politely than by dereferencing NULL).
+	 * This should be at least a WARN_ON once that's sorted.
+	 */
+	if (!fwspec->iommu_priv)
+		return -ENODEV;
+
 	smmu = fwspec_smmu(fwspec);
 	/* Ensure that the domain is finalised */
 	ret = arm_smmu_init_domain_context(domain, smmu);
@@ -1390,7 +1402,7 @@ static int arm_smmu_add_device(struct device *dev)
 		fwspec = dev->iommu_fwspec;
 		if (ret)
 			goto out_free;
-	} else if (fwspec) {
+	} else if (fwspec && fwspec->ops == &arm_smmu_ops) {
 		smmu = arm_smmu_get_by_node(to_of_node(fwspec->iommu_fwnode));
 	} else {
 		return -ENODEV;
diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
index a4407eabf0e64fbacba5573bc3eb91204c97a19c..3965e73db51cef0f3d3b5593da18c9d9fe25fd9e 100644
--- a/drivers/iommu/intel-iommu.c
+++ b/drivers/iommu/intel-iommu.c
@@ -1711,6 +1711,7 @@ static void disable_dmar_iommu(struct intel_iommu *iommu)
 	if (!iommu->domains || !iommu->domain_ids)
 		return;
 
+again:
 	spin_lock_irqsave(&device_domain_lock, flags);
 	list_for_each_entry_safe(info, tmp, &device_domain_list, global) {
 		struct dmar_domain *domain;
@@ -1723,10 +1724,19 @@ static void disable_dmar_iommu(struct intel_iommu *iommu)
 
 		domain = info->domain;
 
-		dmar_remove_one_dev_info(domain, info->dev);
+		__dmar_remove_one_dev_info(info);
 
-		if (!domain_type_is_vm_or_si(domain))
+		if (!domain_type_is_vm_or_si(domain)) {
+			/*
+			 * The domain_exit() function  can't be called under
+			 * device_domain_lock, as it takes this lock itself.
+			 * So release the lock here and re-run the loop
+			 * afterwards.
+			 */
+			spin_unlock_irqrestore(&device_domain_lock, flags);
 			domain_exit(domain);
+			goto again;
+		}
 	}
 	spin_unlock_irqrestore(&device_domain_lock, flags);