Remove _ds_boundary abuse (again)

The logic behind this change is this: a single mbuf may reference
only a contiguous chunk of memory.  When this chunk crosses a page
boundary only the first part of it has a non-zero offset while all
other chunks start at the beginning of the page.

We take advantage of this fact and calculate the offset of a first
chunk as a simple "mtod(m, vaddr_t) & PAGE_MASK".

3 files changed, 6 insertions, 17 deletions

diff --git a/sys/dev/pv/if_xnf.c b/sys/dev/pv/if_xnf.c
index 22805f52304..5e5dd4148a8 100644
--- a/sys/dev/pv/if_xnf.c
+++ b/sys/dev/pv/if_xnf.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: if_xnf.c,v 1.39 2016/09/13 10:16:22 mikeb Exp $	*/
+/*	$OpenBSD: if_xnf.c,v 1.40 2016/10/06 17:00:25 mikeb Exp $	*/
 
 /*
  * Copyright (c) 2015, 2016 Mike Belopuhov
@@ -586,7 +586,9 @@ xnf_encap(struct xnf_softc *sc, struct mbuf *m_head, uint32_t *prod)
 			/* The chunk flag will be removed from the last one */
 			txd->txd_req.txq_flags |= XNF_TXF_CHUNK;
 			txd->txd_req.txq_ref = dmap->dm_segs[n].ds_addr;
-			txd->txd_req.txq_offset = dmap->dm_segs[n].ds_offset;
+			if (n == 0)
+				txd->txd_req.txq_offset =
+				    mtod(m, vaddr_t) & PAGE_MASK;
 			(*prod)++;
 		}
 	}
diff --git a/sys/dev/pv/xen.c b/sys/dev/pv/xen.c
index 27759ffa982..602984d5905 100644
--- a/sys/dev/pv/xen.c
+++ b/sys/dev/pv/xen.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: xen.c,v 1.63 2016/09/12 17:22:45 mikeb Exp $	*/
+/*	$OpenBSD: xen.c,v 1.64 2016/10/06 17:00:25 mikeb Exp $	*/
 
 /*
  * Copyright (c) 2015 Mike Belopuhov
@@ -1191,8 +1191,6 @@ xen_bus_dmamap_load(bus_dma_tag_t t, bus_dmamap_t map, void *buf,
 		xen_grant_table_enter(sc, gm[i].gm_ref, map->dm_segs[i].ds_addr,
 		    domain, flags & BUS_DMA_WRITE ? GTF_readonly : 0);
 		gm[i].gm_paddr = map->dm_segs[i].ds_addr;
-		map->dm_segs[i].ds_offset = map->dm_segs[i].ds_addr &
-		    PAGE_MASK;
 		map->dm_segs[i].ds_addr = gm[i].gm_ref;
 	}
 	return (0);
@@ -1214,8 +1212,6 @@ xen_bus_dmamap_load_mbuf(bus_dma_tag_t t, bus_dmamap_t map, struct mbuf *m0,
 	for (i = 0; i < map->dm_nsegs; i++) {
 		xen_grant_table_enter(sc, gm[i].gm_ref, map->dm_segs[i].ds_addr,
 		    domain, flags & BUS_DMA_WRITE ? GTF_readonly : 0);
-		map->dm_segs[i].ds_offset = map->dm_segs[i].ds_addr &
-		    PAGE_MASK;
 		gm[i].gm_paddr = map->dm_segs[i].ds_addr;
 		map->dm_segs[i].ds_addr = gm[i].gm_ref;
 	}
diff --git a/sys/dev/pv/xenvar.h b/sys/dev/pv/xenvar.h
index 718880282b6..a0786b7f531 100644
--- a/sys/dev/pv/xenvar.h
+++ b/sys/dev/pv/xenvar.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: xenvar.h,v 1.38 2016/09/14 17:48:28 mikeb Exp $	*/
+/*	$OpenBSD: xenvar.h,v 1.39 2016/10/06 17:00:25 mikeb Exp $	*/
 
 /*
  * Copyright (c) 2015 Mike Belopuhov
@@ -94,15 +94,6 @@ struct xen_attach_args {
 };
 
 /*
- * Grant table references don't convey the information about an actual
- * offset of the data within the page, however Xen needs to know it.
- * We (ab)use bus_dma_segment's _ds_boundary member to store it.  Please
- * note that we don't save or restore it's original value atm because
- * neither i386 nor amd64 bus_dmamap_unload(9) code needs it.
- */
-#define ds_offset		 _ds_boundary
-
-/*
  *  Hypercalls
  */
 #define XC_MEMORY		12