[dpdk-stable] patch 'net/mlx5: fix Tx doorbell' has been queued to stable release 16.11.1

[Yuanhan Liu]

Hi,

FYI, your patch has been queued to stable release 16.11.1

Note it hasn't been pushed to http://dpdk.org/browse/dpdk-stable
yet. It will be pushed if I get no objections before 01/28/17.
So please shout if anyone has objections.

---

Note 16.11 is a LTS release. v16.11.1 is planned to be released
shortly (about 2-3 weeks) after v17.02.

---

Thanks.

	--yliu

---
>From df2f335b0ad275115937cba7019d50453c9e51e1 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?N=C3=A9lio=20Laranjeiro?= <nelio.laranjeiro at 6wind.com>
Date: Fri, 9 Dec 2016 14:27:58 +0100
Subject: [PATCH] net/mlx5: fix Tx doorbell

[ upstream commit 30807f62b288a738141b20c19caf72fa5e00faed ]

Too much data is uselessly written to the Tx doorbell, which since v16.11
may also cause Tx queues to behave erratically and crash applications.

This regression was seen on VF devices when the BlueFlame buffer size is
zero (txq->bf_buf_size) due to the following change:

 -       txq->bf_offset ^= txq->bf_buf_size;
 +       txq->bf_offset ^= (1 << txq->bf_buf_size);

Fixes: 1d88ba171942 ("net/mlx5: refactor Tx data path")
Fixes: d5793daefec8 ("net/mlx5: reduce memory overhead for BF handling")

Signed-off-by: Nelio Laranjeiro <nelio.laranjeiro at 6wind.com>
Acked-by: Adrien Mazarguil <adrien.mazarguil at 6wind.com>
---
 drivers/net/mlx5/mlx5_rxtx.c | 26 ++++++++++++--------------
 drivers/net/mlx5/mlx5_rxtx.h |  2 --
 drivers/net/mlx5/mlx5_txq.c  |  2 --
 3 files changed, 12 insertions(+), 18 deletions(-)

diff --git a/drivers/net/mlx5/mlx5_rxtx.c b/drivers/net/mlx5/mlx5_rxtx.c
index 0eb1c94..e31d985 100644
--- a/drivers/net/mlx5/mlx5_rxtx.c
+++ b/drivers/net/mlx5/mlx5_rxtx.c
@@ -79,7 +79,8 @@ txq_mp2mr(struct txq *txq, struct rte_mempool *mp)
 	__attribute__((always_inline));
 
 static inline void
-mlx5_tx_dbrec(struct txq *txq) __attribute__((always_inline));
+mlx5_tx_dbrec(struct txq *txq, volatile struct mlx5_wqe *wqe)
+	__attribute__((always_inline));
 
 static inline uint32_t
 rxq_cq_to_pkt_type(volatile struct mlx5_cqe *cqe)
@@ -308,23 +309,20 @@ txq_mp2mr(struct txq *txq, struct rte_mempool *mp)
  *
  * @param txq
  *   Pointer to TX queue structure.
+ * @param wqe
+ *   Pointer to the last WQE posted in the NIC.
  */
 static inline void
-mlx5_tx_dbrec(struct txq *txq)
+mlx5_tx_dbrec(struct txq *txq, volatile struct mlx5_wqe *wqe)
 {
-	uint8_t *dst = (uint8_t *)((uintptr_t)txq->bf_reg + txq->bf_offset);
-	uint32_t data[4] = {
-		htonl((txq->wqe_ci << 8) | MLX5_OPCODE_SEND),
-		htonl(txq->qp_num_8s),
-		0,
-		0,
-	};
+	uint64_t *dst = (uint64_t *)((uintptr_t)txq->bf_reg);
+	volatile uint64_t *src = ((volatile uint64_t *)wqe);
+
 	rte_wmb();
 	*txq->qp_db = htonl(txq->wqe_ci);
 	/* Ensure ordering between DB record and BF copy. */
 	rte_wmb();
-	memcpy(dst, (uint8_t *)data, 16);
-	txq->bf_offset ^= (1 << txq->bf_buf_size);
+	*dst = *src;
 }
 
 /**
@@ -610,7 +608,7 @@ next_pkt:
 	txq->stats.opackets += i;
 #endif
 	/* Ring QP doorbell. */
-	mlx5_tx_dbrec(txq);
+	mlx5_tx_dbrec(txq, (volatile struct mlx5_wqe *)wqe);
 	txq->elts_head = elts_head;
 	return i;
 }
@@ -818,7 +816,7 @@ mlx5_tx_burst_mpw(void *dpdk_txq, struct rte_mbuf **pkts, uint16_t pkts_n)
 	/* Ring QP doorbell. */
 	if (mpw.state == MLX5_MPW_STATE_OPENED)
 		mlx5_mpw_close(txq, &mpw);
-	mlx5_tx_dbrec(txq);
+	mlx5_tx_dbrec(txq, mpw.wqe);
 	txq->elts_head = elts_head;
 	return i;
 }
@@ -1087,7 +1085,7 @@ mlx5_tx_burst_mpw_inline(void *dpdk_txq, struct rte_mbuf **pkts,
 		mlx5_mpw_inline_close(txq, &mpw);
 	else if (mpw.state == MLX5_MPW_STATE_OPENED)
 		mlx5_mpw_close(txq, &mpw);
-	mlx5_tx_dbrec(txq);
+	mlx5_tx_dbrec(txq, mpw.wqe);
 	txq->elts_head = elts_head;
 	return i;
 }
diff --git a/drivers/net/mlx5/mlx5_rxtx.h b/drivers/net/mlx5/mlx5_rxtx.h
index 5708c2a..909d80e 100644
--- a/drivers/net/mlx5/mlx5_rxtx.h
+++ b/drivers/net/mlx5/mlx5_rxtx.h
@@ -251,8 +251,6 @@ struct txq {
 	uint16_t elts_n:4; /* (*elts)[] length (in log2). */
 	uint16_t cqe_n:4; /* Number of CQ elements (in log2). */
 	uint16_t wqe_n:4; /* Number of of WQ elements (in log2). */
-	uint16_t bf_buf_size:4; /* Log2 Blueflame size. */
-	uint16_t bf_offset; /* Blueflame offset. */
 	uint16_t max_inline; /* Multiple of RTE_CACHE_LINE_SIZE to inline. */
 	uint32_t qp_num_8s; /* QP number shifted by 8. */
 	volatile struct mlx5_cqe (*cqes)[]; /* Completion queue. */
diff --git a/drivers/net/mlx5/mlx5_txq.c b/drivers/net/mlx5/mlx5_txq.c
index 053665d..439908f 100644
--- a/drivers/net/mlx5/mlx5_txq.c
+++ b/drivers/net/mlx5/mlx5_txq.c
@@ -220,8 +220,6 @@ txq_setup(struct txq_ctrl *tmpl, struct txq_ctrl *txq_ctrl)
 	tmpl->txq.wqe_n = log2above(qp->sq.wqe_cnt);
 	tmpl->txq.qp_db = &qp->gen_data.db[MLX5_SND_DBR];
 	tmpl->txq.bf_reg = qp->gen_data.bf->reg;
-	tmpl->txq.bf_offset = qp->gen_data.bf->offset;
-	tmpl->txq.bf_buf_size = log2above(qp->gen_data.bf->buf_size);
 	tmpl->txq.cq_db = cq->dbrec;
 	tmpl->txq.cqes =
 		(volatile struct mlx5_cqe (*)[])
-- 
1.9.0