git: 9dc7c250b8bd - main - cxgb(4): Remove assumption of physically contiguous mbufs.

[Alexander Motin]

The branch main has been updated by mav:

URL: https://cgit.FreeBSD.org/src/commit/?id=9dc7c250b8bd2d5e669c7633e189a700a02c0571

commit 9dc7c250b8bd2d5e669c7633e189a700a02c0571
Author:     Alexander Motin <mav at FreeBSD.org>
AuthorDate: 2021-01-31 17:46:57 +0000
Commit:     Alexander Motin <mav at FreeBSD.org>
CommitDate: 2021-01-31 17:55:06 +0000

    cxgb(4): Remove assumption of physically contiguous mbufs.
    
    Investigation of iSCSI target data corruption reports brought me to
    discovery that cxgb(4) expects mbufs to be physically contiguous, that
    is not true after I've started using m_extaddref() in software iSCSI
    for large zero-copy transmissions.  In case of fragmented memory the
    driver transmitted garbage from pages following the first one due to
    simple use of pmap_kextract() for the first pointer instead of proper
    bus_dmamap_load_mbuf_sg().  Seems like it was done as some optimization
    many years ago, and at very least it is wrong in a world of IOMMUs.
    
    This patch just removes that optimization, plus limits packet coalescing
    for mbufs crossing page boundary, also depending on assumption of one
    segment per packet.
    
    MFC after:      3 days
    Sponsored by:   iXsystems, Inc.
    Reviewed by:    mmacy, np
    Differential revision:  https://reviews.freebsd.org/D28428
---
 sys/dev/cxgb/cxgb_sge.c      |  3 ++-
 sys/dev/cxgb/sys/mvec.h      | 14 --------------
 sys/dev/cxgb/sys/uipc_mvec.c | 24 +++---------------------
 3 files changed, 5 insertions(+), 36 deletions(-)

diff --git a/sys/dev/cxgb/cxgb_sge.c b/sys/dev/cxgb/cxgb_sge.c
index 7f456ccff4ca..491d1a751f4a 100644
--- a/sys/dev/cxgb/cxgb_sge.c
+++ b/sys/dev/cxgb/cxgb_sge.c
@@ -322,7 +322,8 @@ coalesce_check(struct mbuf *m, void *arg)
 	int *nbytes = &ci->nbytes;
 
 	if ((*nbytes == 0) || ((*nbytes + m->m_len <= 10500) &&
-		(*count < 7) && (m->m_next == NULL))) {
+	    (*count < 7) && (m->m_next == NULL) &&
+	    ((mtod(m, vm_offset_t) & PAGE_MASK) + m->m_len <= PAGE_SIZE))) {
 		*count += 1;
 		*nbytes += m->m_len;
 		return (1);
diff --git a/sys/dev/cxgb/sys/mvec.h b/sys/dev/cxgb/sys/mvec.h
index bdd0b55c5489..4989bff29ec4 100644
--- a/sys/dev/cxgb/sys/mvec.h
+++ b/sys/dev/cxgb/sys/mvec.h
@@ -33,20 +33,6 @@
 #define _MVEC_H_
 #include <machine/bus.h>
 
-static __inline void
-busdma_map_mbuf_fast(bus_dma_tag_t tag, bus_dmamap_t map,
-    struct mbuf *m, bus_dma_segment_t *seg)
-{
-#if defined(__i386__) || defined(__amd64__)
-	seg->ds_addr = pmap_kextract(mtod(m, vm_offset_t));
-	seg->ds_len = m->m_len;
-#else
-	int nsegstmp;
-
-	bus_dmamap_load_mbuf_sg(tag, map, m, seg, &nsegstmp, 0);
-#endif
-}
-
 int busdma_map_sg_collapse(bus_dma_tag_t tag, bus_dmamap_t map,
     struct mbuf **m, bus_dma_segment_t *segs, int *nsegs);
 void busdma_map_sg_vec(bus_dma_tag_t tag, bus_dmamap_t map,
diff --git a/sys/dev/cxgb/sys/uipc_mvec.c b/sys/dev/cxgb/sys/uipc_mvec.c
index ca31cf1897c7..02f437079468 100644
--- a/sys/dev/cxgb/sys/uipc_mvec.c
+++ b/sys/dev/cxgb/sys/uipc_mvec.c
@@ -65,26 +65,7 @@ busdma_map_sg_collapse(bus_dma_tag_t tag, bus_dmamap_t map,
 retry:
 	psegs = segs;
 	seg_count = 0;
-	if (n->m_next == NULL) {
-		busdma_map_mbuf_fast(tag, map, n, segs);
-		*nsegs = 1;
-		return (0);
-	}
-#if defined(__i386__) || defined(__amd64__)
-	while (n && seg_count < TX_MAX_SEGS) {
-		/*
-		 * firmware doesn't like empty segments
-		 */
-		if (__predict_true(n->m_len != 0)) {
-			seg_count++;
-			busdma_map_mbuf_fast(tag, map, n, psegs);
-			psegs++;
-		}
-		n = n->m_next;
-	}
-#else
 	err = bus_dmamap_load_mbuf_sg(tag, map, *m, segs, &seg_count, 0);
-#endif	
 	if (seg_count == 0) {
 		if (cxgb_debug)
 			printf("empty segment chain\n");
@@ -117,8 +98,9 @@ void
 busdma_map_sg_vec(bus_dma_tag_t tag, bus_dmamap_t map,
     struct mbuf *m, bus_dma_segment_t *segs, int *nsegs)
 {
+	int n = 0;
 
-	for (*nsegs = 0; m != NULL ; segs++, *nsegs += 1, m = m->m_nextpkt)
-		busdma_map_mbuf_fast(tag, map, m, segs);
+	for (*nsegs = 0; m != NULL; segs += n, *nsegs += n, m = m->m_nextpkt)
+		bus_dmamap_load_mbuf_sg(tag, map, m, segs, &n, 0);
 }