[dpdk-dev] [PATCH 19.11 03/12] net/e1000: fix Tx descriptor status api (igb)

Thierry Herbelot thierry.herbelot at 6wind.com
Wed Aug 7 16:37:22 CEST 2019


From: Olivier Matz <olivier.matz at 6wind.com>

The Tx descriptor status api was not behaving as expected. This API is
used to inspect the content of the descriptors in the Tx ring to
determine the length of the Tx queue.

Since the software advances the tail pointer and the hardware advances
the head pointer, the Tx queue is located before txq->tx_tail in the
ring. Therefore, a call to rte_eth_tx_descriptor_status(..., offset=20)
should inspect the 20th descriptor before the tail, not after.

Fixes: 978f8eea1719 ("net/e1000: implement descriptor status API (igb)")
Cc: stable at dpdk.org

Signed-off-by: Olivier Matz <olivier.matz at 6wind.com>
---
 drivers/net/e1000/igb_rxtx.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/drivers/net/e1000/igb_rxtx.c b/drivers/net/e1000/igb_rxtx.c
index c5606de5d7a0..c22118e59a21 100644
--- a/drivers/net/e1000/igb_rxtx.c
+++ b/drivers/net/e1000/igb_rxtx.c
@@ -1835,14 +1835,15 @@ eth_igb_tx_descriptor_status(void *tx_queue, uint16_t offset)
 {
 	struct igb_tx_queue *txq = tx_queue;
 	volatile uint32_t *status;
-	uint32_t desc;
+	int32_t desc;
 
 	if (unlikely(offset >= txq->nb_tx_desc))
 		return -EINVAL;
 
-	desc = txq->tx_tail + offset;
-	if (desc >= txq->nb_tx_desc)
-		desc -= txq->nb_tx_desc;
+	desc = txq->tx_tail - offset - 1;
+	if (desc < 0)
+		desc += txq->nb_tx_desc;
+	desc = txq->sw_ring[desc].last_id;
 
 	status = &txq->tx_ring[desc].wb.status;
 	if (*status & rte_cpu_to_le_32(E1000_TXD_STAT_DD))
-- 
2.11.0



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