===== drivers/block/DAC960.c 1.60 vs edited =====
--- 1.60/drivers/block/DAC960.c	Fri Jun  6 01:37:51 2003
+++ edited/drivers/block/DAC960.c	Tue Jul  1 10:51:21 2003
@@ -2475,6 +2475,8 @@
   RequestQueue = &Controller->RequestQueue;
   blk_init_queue(RequestQueue, DAC960_RequestFunction, &Controller->queue_lock);
   blk_queue_bounce_limit(RequestQueue, Controller->BounceBufferLimit);
+  blk_queue_dma_mask(RequestQueue, Controller->BounceBufferLimit);
+
   RequestQueue->queuedata = Controller;
   blk_queue_max_hw_segments(RequestQueue,
 			    Controller->DriverScatterGatherLimit);
===== drivers/block/cciss.c 1.82 vs edited =====
--- 1.82/drivers/block/cciss.c	Thu Jun  5 08:17:28 2003
+++ edited/drivers/block/cciss.c	Tue Jul  1 10:49:56 2003
@@ -2541,6 +2541,7 @@
 	spin_lock_init(&hba[i]->lock);
         blk_init_queue(q, do_cciss_request, &hba[i]->lock);
 	blk_queue_bounce_limit(q, hba[i]->pdev->dma_mask);
+	blk_queue_dma_mask(q, hba[i]->pdev->dma_mask);
 
 	/* This is a hardware imposed limit. */
 	blk_queue_max_hw_segments(q, MAXSGENTRIES);
===== drivers/block/cpqarray.c 1.77 vs edited =====
--- 1.77/drivers/block/cpqarray.c	Wed Jun 11 01:33:24 2003
+++ edited/drivers/block/cpqarray.c	Tue Jul  1 10:51:52 2003
@@ -389,6 +389,7 @@
 		spin_lock_init(&hba[i]->lock);
 		blk_init_queue(q, do_ida_request, &hba[i]->lock);
 		blk_queue_bounce_limit(q, hba[i]->pci_dev->dma_mask);
+		blk_queue_dma_mask(q, hba[i]->pci_dev->dma_mask);
 
 		/* This is a hardware imposed limit. */
 		blk_queue_max_hw_segments(q, SG_MAX);
===== drivers/block/ll_rw_blk.c 1.174 vs edited =====
--- 1.174/drivers/block/ll_rw_blk.c	Mon Jun  2 20:32:46 2003
+++ edited/drivers/block/ll_rw_blk.c	Tue Jul  1 10:39:46 2003
@@ -213,12 +213,32 @@
 	 * by default assume old behaviour and bounce for any highmem page
 	 */
 	blk_queue_bounce_limit(q, BLK_BOUNCE_HIGH);
+	/*
+	 * and assume a 32 bit dma mask 
+	 */
+	blk_queue_dma_mask(q, 0xffffffff);
 
 	init_waitqueue_head(&q->queue_wait);
 	INIT_LIST_HEAD(&q->plug_list);
 }
 
 /**
+ * blk_queue_dma_mask - set queue dma mask
+ * @q:	the request queue for the device
+ * @dma_addr:	bus address limit
+ *
+ * Description:
+ *    This will set the device physical DMA mask.  This is used by
+ *    the bio layer to arrange the segments correctly for IOMMUs that
+ *    can be programmed in bypass mode.  Note: setting this does *not*
+ *    change whether the device goes through an IOMMU or not
+ **/
+void blk_queue_dma_mask(request_queue_t *q, u64 dma_mask)
+{
+	q->dma_mask = dma_mask;
+}
+
+/**
  * blk_queue_bounce_limit - set bounce buffer limit for queue
  * @q:  the request queue for the device
  * @dma_addr:   bus address limit
@@ -746,7 +766,7 @@
 			continue;
 		}
 new_segment:
-		if (!bvprv || !BIOVEC_VIRT_MERGEABLE(bvprv, bv))
+		if (!bvprv || !BIOVEC_VIRT_MERGEABLE(q, bvprv, bv))
 			nr_hw_segs++;
 
 		nr_phys_segs++;
@@ -787,7 +807,7 @@
 	if (!(q->queue_flags & (1 << QUEUE_FLAG_CLUSTER)))
 		return 0;
 
-	if (!BIOVEC_VIRT_MERGEABLE(__BVEC_END(bio), __BVEC_START(nxt)))
+	if (!BIOVEC_VIRT_MERGEABLE(q, __BVEC_END(bio), __BVEC_START(nxt)))
 		return 0;
 	if (bio->bi_size + nxt->bi_size > q->max_segment_size)
 		return 0;
@@ -909,7 +929,7 @@
 		return 0;
 	}
 
-	if (BIOVEC_VIRT_MERGEABLE(__BVEC_END(req->biotail), __BVEC_START(bio)))
+	if (BIOVEC_VIRT_MERGEABLE(q, __BVEC_END(req->biotail), __BVEC_START(bio)))
 		return ll_new_mergeable(q, req, bio);
 
 	return ll_new_hw_segment(q, req, bio);
@@ -924,7 +944,7 @@
 		return 0;
 	}
 
-	if (BIOVEC_VIRT_MERGEABLE(__BVEC_END(bio), __BVEC_START(req->bio)))
+	if (BIOVEC_VIRT_MERGEABLE(q, __BVEC_END(bio), __BVEC_START(req->bio)))
 		return ll_new_mergeable(q, req, bio);
 
 	return ll_new_hw_segment(q, req, bio);
===== drivers/ide/ide-lib.c 1.8 vs edited =====
--- 1.8/drivers/ide/ide-lib.c	Thu Mar  6 17:27:52 2003
+++ edited/drivers/ide/ide-lib.c	Tue Jul  1 10:49:14 2003
@@ -406,6 +406,9 @@
 			addr = HWIF(drive)->pci_dev->dma_mask;
 	}
 
+	if((HWIF(drive)->pci_dev))
+		blk_queue_dma_mask(&drive->queue,
+				   HWIF(drive)->pci_dev->dma_mask);
 	blk_queue_bounce_limit(&drive->queue, addr);
 }
 
===== drivers/scsi/scsi_lib.c 1.99 vs edited =====
--- 1.99/drivers/scsi/scsi_lib.c	Sun Jun 29 20:14:44 2003
+++ edited/drivers/scsi/scsi_lib.c	Tue Jul  1 10:54:19 2003
@@ -1256,6 +1256,8 @@
 	blk_queue_max_phys_segments(q, MAX_PHYS_SEGMENTS);
 	blk_queue_max_sectors(q, shost->max_sectors);
 	blk_queue_bounce_limit(q, scsi_calculate_bounce_limit(shost));
+	if(scsi_get_device(shost) && scsi_get_device(shost)->dma_mask)
+		blk_queue_dma_mask(q, *scsi_get_device(shost)->dma_mask);
 
 	if (!shost->use_clustering)
 		clear_bit(QUEUE_FLAG_CLUSTER, &q->queue_flags);
===== include/linux/bio.h 1.32 vs edited =====
--- 1.32/include/linux/bio.h	Tue Jun 10 07:54:25 2003
+++ edited/include/linux/bio.h	Tue Jul  1 11:20:26 2003
@@ -30,6 +30,11 @@
 #define BIO_VMERGE_BOUNDARY	0
 #endif
 
+/* Can the IOMMU (if any) work in bypass mode */
+#ifndef BIO_VMERGE_BYPASS_MASK
+#define BIO_VMERGE_BYPASS_MASK	0
+#endif
+
 #define BIO_DEBUG
 
 #ifdef BIO_DEBUG
@@ -156,6 +161,13 @@
 
 #define __bio_kunmap_atomic(addr, kmtype) kunmap_atomic(addr, kmtype)
 
+/* can the bio vec be directly physically addressed by the device */
+#define __BVEC_PHYS_DIRECT_OK(q, vec) \
+	((bvec_to_phys(vec) & (q)->dma_mask) == bvec_to_phys(vec))
+/* Is the queue dma_mask eligible to be bypassed */
+#define __BIO_CAN_BYPASS(q) \
+	((BIO_VMERGE_BYPASS_MASK) && ((q)->dma_mask & (BIO_VMERGE_BYPASS_MASK)) == (BIO_VMERGE_BYPASS_MASK))
+
 /*
  * merge helpers etc
  */
@@ -164,8 +176,10 @@
 #define __BVEC_START(bio)	bio_iovec_idx((bio), 0)
 #define BIOVEC_PHYS_MERGEABLE(vec1, vec2)	\
 	((bvec_to_phys((vec1)) + (vec1)->bv_len) == bvec_to_phys((vec2)))
-#define BIOVEC_VIRT_MERGEABLE(vec1, vec2)	\
-	((((bvec_to_phys((vec1)) + (vec1)->bv_len) | bvec_to_phys((vec2))) & (BIO_VMERGE_BOUNDARY - 1)) == 0)
+#define BIOVEC_VIRT_MERGEABLE(q, vec1, vec2)	\
+	(((((bvec_to_phys((vec1)) + (vec1)->bv_len) | bvec_to_phys((vec2))) & (BIO_VMERGE_BOUNDARY - 1)) == 0) \
+	&& !( __BIO_CAN_BYPASS(q) && (__BVEC_PHYS_DIRECT_OK(q, vec1) \
+				      || __BVEC_PHYS_DIRECT_OK(q, vec2))))
 #define __BIO_SEG_BOUNDARY(addr1, addr2, mask) \
 	(((addr1) | (mask)) == (((addr2) - 1) | (mask)))
 #define BIOVEC_SEG_BOUNDARY(q, b1, b2) \
===== include/linux/blkdev.h 1.109 vs edited =====
--- 1.109/include/linux/blkdev.h	Wed Jun 11 20:17:55 2003
+++ edited/include/linux/blkdev.h	Tue Jul  1 10:39:18 2003
@@ -255,6 +255,12 @@
 	unsigned long		bounce_pfn;
 	int			bounce_gfp;
 
+	/*
+	 * The physical dma_mask for the queue (used to make IOMMU
+	 * bypass decisions)
+	 */
+	u64			dma_mask;
+
 	struct list_head	plug_list;
 
 	/*
@@ -458,6 +464,7 @@
 extern void blk_cleanup_queue(request_queue_t *);
 extern void blk_queue_make_request(request_queue_t *, make_request_fn *);
 extern void blk_queue_bounce_limit(request_queue_t *, u64);
+extern void blk_queue_dma_mask(request_queue_t *, u64);
 extern void blk_queue_max_sectors(request_queue_t *, unsigned short);
 extern void blk_queue_max_phys_segments(request_queue_t *, unsigned short);
 extern void blk_queue_max_hw_segments(request_queue_t *, unsigned short);