MFamd64 r204214: Enforce stronger alignment semantics (require that the

end of segments be aligned, not just the start of segments) in order to
allow Xen's blkfront driver to operate correctly.

PR:		kern/152818
MFC after:	3 days

1 files changed, 18 insertions, 12 deletions

diff --git a/sys/i386/i386/busdma_machdep.c b/sys/i386/i386/busdma_machdep.c
index 93e93c5..5c1ec92 100644
--- a/sys/i386/i386/busdma_machdep.c
+++ b/sys/i386/i386/busdma_machdep.c
@@ -246,8 +246,7 @@ bus_dma_tag_create(bus_dma_tag_t parent, bus_size_t alignment,
 	newtag->alignment = alignment;
 	newtag->boundary = boundary;
 	newtag->lowaddr = trunc_page((vm_paddr_t)lowaddr) + (PAGE_SIZE - 1);
-	newtag->highaddr = trunc_page((vm_paddr_t)highaddr) +
-	    (PAGE_SIZE - 1);
+	newtag->highaddr = trunc_page((vm_paddr_t)highaddr) + (PAGE_SIZE - 1);
 	newtag->filter = filter;
 	newtag->filterarg = filterarg;
 	newtag->maxsize = maxsize;
@@ -594,15 +593,19 @@ _bus_dmamap_count_pages(bus_dma_tag_t dmat, bus_dmamap_t map, pmap_t pmap,
 		vendaddr = (vm_offset_t)buf + buflen;
 
 		while (vaddr < vendaddr) {
+			bus_size_t sg_len;
+
+			sg_len = PAGE_SIZE - ((vm_offset_t)vaddr & PAGE_MASK);
 			if (pmap)
 				paddr = pmap_extract(pmap, vaddr);
 			else
 				paddr = pmap_kextract(vaddr);
 			if (((dmat->flags & BUS_DMA_COULD_BOUNCE) != 0) &&
 			    run_filter(dmat, paddr) != 0) {
+				sg_len = roundup2(sg_len, dmat->alignment);
 				map->pagesneeded++;
 			}
-			vaddr += (PAGE_SIZE - ((vm_offset_t)vaddr & PAGE_MASK));
+			vaddr += sg_len;
 		}
 		CTR1(KTR_BUSDMA, "pagesneeded= %d\n", map->pagesneeded);
 	}
@@ -669,6 +672,8 @@ _bus_dmamap_load_buffer(bus_dma_tag_t dmat,
 	bmask = ~(dmat->boundary - 1);
 
 	for (seg = *segp; buflen > 0 ; ) {
+		bus_size_t max_sgsize;
+
 		/*
 		 * Get the physical address for this segment.
 		 */
@@ -680,11 +685,16 @@ _bus_dmamap_load_buffer(bus_dma_tag_t dmat,
 		/*
 		 * Compute the segment size, and adjust counts.
 		 */
-		sgsize = PAGE_SIZE - ((u_long)curaddr & PAGE_MASK);
-		if (sgsize > dmat->maxsegsz)
-			sgsize = dmat->maxsegsz;
-		if (buflen < sgsize)
-			sgsize = buflen;
+		max_sgsize = MIN(buflen, dmat->maxsegsz);
+		sgsize = PAGE_SIZE - ((vm_offset_t)curaddr & PAGE_MASK);
+		if (((dmat->flags & BUS_DMA_COULD_BOUNCE) != 0) &&
+		    map->pagesneeded != 0 && run_filter(dmat, curaddr)) {
+			sgsize = roundup2(sgsize, dmat->alignment);
+			sgsize = MIN(sgsize, max_sgsize);
+			curaddr = add_bounce_page(dmat, map, vaddr, sgsize);
+		} else {
+			sgsize = MIN(sgsize, max_sgsize);
+		}
 
 		/*
 		 * Make sure we don't cross any boundaries.
@@ -695,10 +705,6 @@ _bus_dmamap_load_buffer(bus_dma_tag_t dmat,
 				sgsize = (baddr - curaddr);
 		}
 
-		if (((dmat->flags & BUS_DMA_COULD_BOUNCE) != 0) &&
-		    map->pagesneeded != 0 && run_filter(dmat, curaddr))
-			curaddr = add_bounce_page(dmat, map, vaddr, sgsize);
-
 		/*
 		 * Insert chunk into a segment, coalescing with
 		 * previous segment if possible.