diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
index 23c24fe..80bdb4d 100644
--- a/drivers/vfio/vfio_iommu_type1.c
+++ b/drivers/vfio/vfio_iommu_type1.c
@@ -859,6 +859,8 @@ static int vfio_iommu_type1_pin_pages(void *iommu_data,
 	if (!iommu->v2)
 		return -EACCES;
 
+	WARN_ON(iommu->vaddr_invalid_count);
+
 	mutex_lock(&iommu->lock);
 
 	/*
@@ -976,6 +978,8 @@ static void vfio_iommu_type1_unpin_pages(void *iommu_data,
 
 	mutex_lock(&iommu->lock);
 
+	WARN_ON(iommu->vaddr_invalid_count);
+
 	do_accounting = list_empty(&iommu->domain_list);
 	for (i = 0; i < npage; i++) {
 		dma_addr_t iova = user_iova + PAGE_SIZE * i;
@@ -1343,6 +1347,10 @@ static int vfio_dma_do_unmap(struct vfio_iommu *iommu,
 
 	mutex_lock(&iommu->lock);
 
+	/* Cannot update vaddr if mdev is present. */
+	if (invalidate_vaddr && !list_empty(&iommu->emulated_iommu_groups))
+		goto unlock;
+
 	pgshift = __ffs(iommu->pgsize_bitmap);
 	pgsize = (size_t)1 << pgshift;
 
@@ -2189,6 +2197,10 @@ static int vfio_iommu_type1_attach_group(void *iommu_data,
 
 	mutex_lock(&iommu->lock);
 
+	/* Attach could require pinning, so disallow while vaddr is invalid. */
+	if (iommu->vaddr_invalid_count)
+		goto out_unlock;
+
 	/* Check for duplicates */
 	if (vfio_iommu_find_iommu_group(iommu, iommu_group))
 		goto out_unlock;
@@ -2660,6 +2672,16 @@ static int vfio_domains_have_enforce_cache_coherency(struct vfio_iommu *iommu)
 	return ret;
 }
 
+static int vfio_iommu_has_emulated(struct vfio_iommu *iommu)
+{
+	int ret;
+
+	mutex_lock(&iommu->lock);
+	ret = !list_empty(&iommu->emulated_iommu_groups);
+	mutex_unlock(&iommu->lock);
+	return ret;
+}
+
 static int vfio_iommu_type1_check_extension(struct vfio_iommu *iommu,
 					    unsigned long arg)
 {
@@ -2668,8 +2690,13 @@ static int vfio_iommu_type1_check_extension(struct vfio_iommu *iommu,
 	case VFIO_TYPE1v2_IOMMU:
 	case VFIO_TYPE1_NESTING_IOMMU:
 	case VFIO_UNMAP_ALL:
-	case VFIO_UPDATE_VADDR:
 		return 1;
+	case VFIO_UPDATE_VADDR:
+		/*
+		 * Disable this feature if mdevs are present.  They cannot
+		 * safely pin/unpin while vaddrs are being updated.
+		 */
+		return iommu && !vfio_iommu_has_emulated(iommu);
 	case VFIO_DMA_CC_IOMMU:
 		if (!iommu)
 			return 0;
@@ -3080,6 +3107,8 @@ static int vfio_iommu_type1_dma_rw_chunk(struct vfio_iommu *iommu,
 	size_t offset;
 	int ret;
 
+	WARN_ON(iommu->vaddr_invalid_count);
+
 	*copied = 0;
 
 	ret = vfio_find_dma_valid(iommu, user_iova, 1, &dma);
diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
index d7d8e09..4e8d344 100644
--- a/include/uapi/linux/vfio.h
+++ b/include/uapi/linux/vfio.h
@@ -49,7 +49,11 @@
 /* Supports VFIO_DMA_UNMAP_FLAG_ALL */
 #define VFIO_UNMAP_ALL			9
 
-/* Supports the vaddr flag for DMA map and unmap */
+/*
+ * Supports the vaddr flag for DMA map and unmap.  Not supported for mediated
+ * devices, so this capability is subject to change as groups are added or
+ * removed.
+ */
 #define VFIO_UPDATE_VADDR		10
 
 /*
@@ -1215,8 +1219,7 @@ struct vfio_iommu_type1_info_dma_avail {
  * Map process virtual addresses to IO virtual addresses using the
  * provided struct vfio_dma_map. Caller sets argsz. READ &/ WRITE required.
  *
- * If flags & VFIO_DMA_MAP_FLAG_VADDR, update the base vaddr for iova, and
- * unblock translation of host virtual addresses in the iova range.  The vaddr
+ * If flags & VFIO_DMA_MAP_FLAG_VADDR, update the base vaddr for iova. The vaddr
  * must have previously been invalidated with VFIO_DMA_UNMAP_FLAG_VADDR.  To
  * maintain memory consistency within the user application, the updated vaddr
  * must address the same memory object as originally mapped.  Failure to do so
@@ -1267,9 +1270,9 @@ struct vfio_bitmap {
  * must be 0.  This cannot be combined with the get-dirty-bitmap flag.
  *
  * If flags & VFIO_DMA_UNMAP_FLAG_VADDR, do not unmap, but invalidate host
- * virtual addresses in the iova range.  Tasks that attempt to translate an
- * iova's vaddr will block.  DMA to already-mapped pages continues.  This
- * cannot be combined with the get-dirty-bitmap flag.
+ * virtual addresses in the iova range.  DMA to already-mapped pages continues.
+ * Groups may not be added to the container while any addresses are invalid.
+ * This cannot be combined with the get-dirty-bitmap flag.
  */
 struct vfio_iommu_type1_dma_unmap {
 	__u32	argsz;
