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* [PATCH] net/nfp: fix the Tx descriptor free logic of nfd3
@ 2023-05-12  2:07 Chaoyong He
  2023-05-18 10:33 ` Ferruh Yigit
  2023-05-18 11:02 ` [PATCH v2] " Chaoyong He
  0 siblings, 2 replies; 5+ messages in thread
From: Chaoyong He @ 2023-05-12  2:07 UTC (permalink / raw)
  To: dev; +Cc: oss-drivers, niklas.soderlund, Chaoyong He, stable

In the tx descriptor free logic of nfd3, the former logic might force
cast a negative number into a very big unsigned number, and which will
cause potential problem in the xmit loop.

The xmit loop will continue in the place where it should break, and will
overwrite the Tx descriptor which is not free to use by the PMD.

Fixes: 74a640dac864 ("net/nfp: avoid modulo operations for handling ring wrapping")
Cc: stable@dpdk.org

Signed-off-by: Chaoyong He <chaoyong.he@corigine.com>
Reviewed-by: Niklas Söderlund <niklas.soderlund@corigine.com>
---
 drivers/net/nfp/nfp_rxtx.h | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/net/nfp/nfp_rxtx.h b/drivers/net/nfp/nfp_rxtx.h
index 5e651518ed..e642bc970a 100644
--- a/drivers/net/nfp/nfp_rxtx.h
+++ b/drivers/net/nfp/nfp_rxtx.h
@@ -401,10 +401,14 @@ nfp_net_mbuf_alloc_failed(struct nfp_net_rxq *rxq)
 static inline uint32_t
 nfp_net_nfd3_free_tx_desc(struct nfp_net_txq *txq)
 {
+	uint32_t free_desc;
+
 	if (txq->wr_p >= txq->rd_p)
-		return txq->tx_count - (txq->wr_p - txq->rd_p) - 8;
+		free_desc = txq->tx_count - (txq->wr_p - txq->rd_p);
 	else
-		return txq->rd_p - txq->wr_p - 8;
+		free_desc = txq->rd_p - txq->wr_p;
+
+	return (free_desc > 8) ? (free_desc - 8) : 0;
 }
 
 /*
-- 
2.39.1


^ permalink raw reply	[flat|nested] 5+ messages in thread

end of thread, other threads:[~2023-05-18 14:43 UTC | newest]

Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2023-05-12  2:07 [PATCH] net/nfp: fix the Tx descriptor free logic of nfd3 Chaoyong He
2023-05-18 10:33 ` Ferruh Yigit
2023-05-18 10:49   ` Chaoyong He
2023-05-18 11:02 ` [PATCH v2] " Chaoyong He
2023-05-18 14:43   ` Ferruh Yigit

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