diff --git a/sys/platform/pc64/x86_64/busdma_machdep.c b/sys/platform/pc64/x86_64/busdma_machdep.c
index 418e668..51d6ff4 100644
--- a/sys/platform/pc64/x86_64/busdma_machdep.c
+++ b/sys/platform/pc64/x86_64/busdma_machdep.c
@@ -87,11 +87,6 @@ struct bus_dma_tag {
 
 #define BUS_DMA_COULD_BOUNCE	(BUS_DMA_BOUNCE_LOWADDR | BUS_DMA_BOUNCE_ALIGN)
 
-#define BUS_DMAMEM_KMALLOC(dmat) \
-	((dmat)->maxsize <= PAGE_SIZE && \
-	 (dmat)->alignment <= PAGE_SIZE && \
-	 (dmat)->lowaddr >= ptoa(Maxmem))
-
 struct bounce_page {
 	vm_offset_t	vaddr;		/* kva of bounce buffer */
 	bus_addr_t	busaddr;	/* Physical address */
@@ -484,32 +479,6 @@ bus_dmamap_destroy(bus_dma_tag_t dmat, bus_dmamap_t map)
 	return (0);
 }
 
-static __inline bus_size_t
-check_kmalloc(bus_dma_tag_t dmat, const void *vaddr0, int verify)
-{
-	bus_size_t maxsize = 0;
-	uintptr_t vaddr = (uintptr_t)vaddr0;
-
-	if ((vaddr ^ (vaddr + dmat->maxsize - 1)) & ~PAGE_MASK) {
-		if (verify)
-			panic("boundary check failed\n");
-		if (bootverbose)
-			kprintf("boundary check failed\n");
-		maxsize = dmat->maxsize;
-	}
-	if (vaddr & (dmat->alignment - 1)) {
-		if (verify)
-			panic("alignment check failed\n");
-		if (bootverbose)
-			kprintf("alignment check failed\n");
-		if (dmat->maxsize < dmat->alignment)
-			maxsize = dmat->alignment;
-		else
-			maxsize = dmat->maxsize;
-	}
-	return maxsize;
-}
-
 /*
  * Allocate a piece of memory that can be efficiently mapped into
  * bus device space based on the constraints lited in the dma tag.
@@ -544,35 +513,13 @@ bus_dmamem_alloc(bus_dma_tag_t dmat, void **vaddr, int flags,
 	else
 		attr = VM_MEMATTR_DEFAULT;
 
-	/* XXX must alloc with correct mem attribute here */
-	if (BUS_DMAMEM_KMALLOC(dmat)) {
-		bus_size_t maxsize;
-
-		*vaddr = kmalloc(dmat->maxsize, M_DEVBUF, mflags);
+	/*
+	 * XXX must alloc with correct mem attribute here.
+	 * Until we get proper IOMMU support, we have to keep buffer in first 4GB.
+	 */
+	*vaddr = contigmalloc(dmat->maxsize, M_DEVBUF, mflags,
+	    0ul, 0xfffffffful, dmat->alignment, dmat->boundary);
 
-		/*
-		 * XXX
-		 * Check whether the allocation
-		 * - crossed a page boundary
-		 * - was not aligned
-		 * Retry with power-of-2 alignment in the above cases.
-		 */
-		maxsize = check_kmalloc(dmat, *vaddr, 0);
-		if (maxsize) {
-			kfree(*vaddr, M_DEVBUF);
-			*vaddr = kmalloc(maxsize, M_DEVBUF,
-			    mflags | M_POWEROF2);
-			check_kmalloc(dmat, *vaddr, 1);
-		}
-	} else {
-		/*
-		 * XXX Use Contigmalloc until it is merged into this facility
-		 *     and handles multi-seg allocations.  Nobody is doing
-		 *     multi-seg allocations yet though.
-		 */
-		*vaddr = contigmalloc(dmat->maxsize, M_DEVBUF, mflags,
-		    0ul, dmat->lowaddr, dmat->alignment, dmat->boundary);
-	}
 	if (*vaddr == NULL)
 		return (ENOMEM);
 
@@ -583,7 +530,7 @@ bus_dmamem_alloc(bus_dma_tag_t dmat, void **vaddr, int flags,
 
 /*
  * Free a piece of memory and it's allociated dmamap, that was allocated
- * via bus_dmamem_alloc.  Make the same choice for free/contigfree.
+ * via bus_dmamem_alloc.
  */
 void
 bus_dmamem_free(bus_dma_tag_t dmat, void *vaddr, bus_dmamap_t map)
@@ -594,10 +541,8 @@ bus_dmamem_free(bus_dma_tag_t dmat, void *vaddr, bus_dmamap_t map)
 	 */
 	if (map != NULL)
 		panic("bus_dmamem_free: Invalid map freed");
-	if (BUS_DMAMEM_KMALLOC(dmat))
-		kfree(vaddr, M_DEVBUF);
-	else
-		contigfree(vaddr, dmat->maxsize, M_DEVBUF);
+
+	contigfree(vaddr, dmat->maxsize, M_DEVBUF);
 }
 
 static __inline vm_paddr_t