Index: sys/arm64/iommu/iommu.c
===================================================================
--- sys/arm64/iommu/iommu.c
+++ sys/arm64/iommu/iommu.c
@@ -136,8 +136,9 @@
 	if (iodom == NULL)
 		return (NULL);
 
+	KASSERT(iodom->end != 0, ("domain end is not set"));
+
 	iommu_domain_init(iommu, iodom, &domain_map_ops);
-	iodom->end = VM_MAXUSER_ADDRESS;
 	iodom->iommu = iommu;
 	iommu_gas_init_domain(iodom);
 
@@ -168,11 +169,11 @@
 }
 
 static void
-iommu_tag_init(struct bus_dma_tag_iommu *t)
+iommu_tag_init(struct iommu_domain *iodom, struct bus_dma_tag_iommu *t)
 {
 	bus_addr_t maxaddr;
 
-	maxaddr = BUS_SPACE_MAXADDR;
+	maxaddr = MIN(iodom->end, BUS_SPACE_MAXADDR);
 
 	t->common.ref_count = 0;
 	t->common.impl = &bus_dma_iommu_impl;
@@ -223,7 +224,7 @@
 	tag->ctx = ioctx;
 	tag->ctx->domain = iodom;
 
-	iommu_tag_init(tag);
+	iommu_tag_init(iodom, tag);
 
 	return (error);
 }
Index: sys/arm64/iommu/smmu.c
===================================================================
--- sys/arm64/iommu/smmu.c
+++ sys/arm64/iommu/smmu.c
@@ -149,6 +149,9 @@
 
 #define	SMMU_Q_ALIGN		(64 * 1024)
 
+#define		MAXADDR_48BIT	0xFFFFFFFFFFFFUL
+#define		MAXADDR_52BIT	0xFFFFFFFFFFFFFUL
+
 static struct resource_spec smmu_spec[] = {
 	{ SYS_RES_MEMORY, 0, RF_ACTIVE },
 	{ SYS_RES_IRQ, 0, RF_ACTIVE },
@@ -1702,6 +1705,7 @@
 static struct iommu_domain *
 smmu_domain_alloc(device_t dev, struct iommu_unit *iommu)
 {
+	struct iommu_domain *iodom;
 	struct smmu_domain *domain;
 	struct smmu_unit *unit;
 	struct smmu_softc *sc;
@@ -1742,7 +1746,14 @@
 	LIST_INSERT_HEAD(&unit->domain_list, domain, next);
 	IOMMU_UNLOCK(iommu);
 
-	return (&domain->iodom);
+	iodom = &domain->iodom;
+
+	if (sc->features & SMMU_FEATURE_VAX)
+		iodom->end = MAXADDR_52BIT;
+	else
+		iodom->end = MAXADDR_48BIT;
+
+	return (iodom);
 }
 
 static void