Index: sys/dev/iommu/busdma_iommu.c
===================================================================
--- sys/dev/iommu/busdma_iommu.c
+++ sys/dev/iommu/busdma_iommu.c
@@ -584,7 +584,7 @@
 		}
 		buflen1 = buflen > tag->common.maxsegsz ?
 		    tag->common.maxsegsz : buflen;
-		size = round_page(offset + buflen1);
+		size = round_page(buflen1);
 
 		/*
 		 * (Too) optimistically allow split if there are more
@@ -600,22 +600,7 @@
 		    gas_flags, ma + idx, &entry);
 		if (error != 0)
 			break;
-		if ((gas_flags & IOMMU_MF_CANSPLIT) != 0) {
-			KASSERT(size >= entry->end - entry->start,
-			    ("split increased entry size %jx %jx %jx",
-			    (uintmax_t)size, (uintmax_t)entry->start,
-			    (uintmax_t)entry->end));
-			size = entry->end - entry->start;
-			if (buflen1 > size)
-				buflen1 = size;
-		} else {
-			KASSERT(entry->end - entry->start == size,
-			    ("no split allowed %jx %jx %jx",
-			    (uintmax_t)size, (uintmax_t)entry->start,
-			    (uintmax_t)entry->end));
-		}
-		if (offset + buflen1 > size)
-			buflen1 = size - offset;
+		buflen1 = entry->end - entry->start;
 		if (buflen1 > tag->common.maxsegsz)
 			buflen1 = tag->common.maxsegsz;