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cxgb(4): Remove assumption of physically contiguous mbufs.

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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
This commit is contained in:
Alexander Motin 2021-01-31 12:46:57 -05:00
parent 8eeeee38f4
commit 9dc7c250b8
3 changed files with 5 additions and 36 deletions
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3
sys/dev/cxgb/cxgb_sge.c
View File

@ -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);

14
sys/dev/cxgb/sys/mvec.h
View File

@ -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,

24
sys/dev/cxgb/sys/uipc_mvec.c
View File

@ -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);
}