[dpdk-dev] [PATCH 26/28] net/mlx5: zero the LRO mbuf headroom

[Matan Azrad <matan@mellanox.com>]

LRO packet may consume all the stride memory, hence the PMD cannot
guaranty head-room for the LRO mbuf.

The issue is lack in HW support to write the packet in offset from the
stride start.

A new striding RQ feature may be added in CX6 DX to allow head-room and
tail-room for the LRO strides.

Signed-off-by: Matan Azrad <matan@mellanox.com>
---
 drivers/net/mlx5/mlx5_rxq.c  | 16 +++++++++++-----
 drivers/net/mlx5/mlx5_rxtx.c |  6 ++++--
 drivers/net/mlx5/mlx5_rxtx.h |  3 ++-
 3 files changed, 17 insertions(+), 8 deletions(-)

diff --git a/drivers/net/mlx5/mlx5_rxq.c b/drivers/net/mlx5/mlx5_rxq.c
index 344ff90..7c252e3 100644
--- a/drivers/net/mlx5/mlx5_rxq.c
+++ b/drivers/net/mlx5/mlx5_rxq.c
@@ -1569,6 +1569,12 @@ struct mlx5_rxq_ctrl *
 	unsigned int mprq_stride_size;
 	struct mlx5_dev_config *config = &priv->config;
 	/*
+	 * LRO packet may consume all the stride memory, hence we cannot
+	 * guaranty head-room. A new striding RQ feature may be added in CX6 DX
+	 * to allow head-room and tail-room for the LRO packets.
+	 */
+	unsigned int strd_headroom_en = mlx5_lro_on(dev) ? 0 : 1;
+	/*
 	 * Always allocate extra slots, even if eventually
 	 * the vector Rx will not be used.
 	 */
@@ -1603,9 +1609,9 @@ struct mlx5_rxq_ctrl *
 	 *    stride.
 	 *  Otherwise, enable Rx scatter if necessary.
 	 */
-	assert(mb_len >= RTE_PKTMBUF_HEADROOM);
+	assert(mb_len >= RTE_PKTMBUF_HEADROOM * strd_headroom_en);
 	mprq_stride_size = dev->data->dev_conf.rxmode.max_rx_pkt_len +
-				RTE_PKTMBUF_HEADROOM;
+				RTE_PKTMBUF_HEADROOM * strd_headroom_en;
 	if (mprq_en &&
 	    desc > (1U << config->mprq.stride_num_n) &&
 	    mprq_stride_size <= (1U << config->mprq.max_stride_size_n)) {
@@ -1617,9 +1623,9 @@ struct mlx5_rxq_ctrl *
 		tmpl->rxq.strd_sz_n = RTE_MAX(log2above(mprq_stride_size),
 					      config->mprq.min_stride_size_n);
 		tmpl->rxq.strd_shift_en = MLX5_MPRQ_TWO_BYTE_SHIFT;
-		tmpl->rxq.mprq_max_memcpy_len =
-			RTE_MIN(mb_len - RTE_PKTMBUF_HEADROOM,
-				config->mprq.max_memcpy_len);
+		tmpl->rxq.strd_headroom_en = strd_headroom_en;
+		tmpl->rxq.mprq_max_memcpy_len = RTE_MIN(mb_len -
+			    RTE_PKTMBUF_HEADROOM, config->mprq.max_memcpy_len);
 		DRV_LOG(DEBUG,
 			"port %u Rx queue %u: Multi-Packet RQ is enabled"
 			" strd_num_n = %u, strd_sz_n = %u",
diff --git a/drivers/net/mlx5/mlx5_rxtx.c b/drivers/net/mlx5/mlx5_rxtx.c
index c7487ac..3872966 100644
--- a/drivers/net/mlx5/mlx5_rxtx.c
+++ b/drivers/net/mlx5/mlx5_rxtx.c
@@ -1540,6 +1540,7 @@ enum mlx5_txcmp_code {
 	unsigned int i = 0;
 	uint32_t rq_ci = rxq->rq_ci;
 	uint16_t consumed_strd = rxq->consumed_strd;
+	uint16_t headroom_sz = rxq->strd_headroom_en * RTE_PKTMBUF_HEADROOM;
 	struct mlx5_mprq_buf *buf = (*rxq->mprq_bufs)[rq_ci & wq_mask];
 
 	while (i < pkts_n) {
@@ -1650,7 +1651,7 @@ enum mlx5_txcmp_code {
 			rte_atomic16_add_return(&buf->refcnt, 1);
 			assert((uint16_t)rte_atomic16_read(&buf->refcnt) <=
 			       strd_n + 1);
-			buf_addr = RTE_PTR_SUB(addr, RTE_PKTMBUF_HEADROOM);
+			buf_addr = RTE_PTR_SUB(addr, headroom_sz);
 			/*
 			 * MLX5 device doesn't use iova but it is necessary in a
 			 * case where the Rx packet is transmitted via a
@@ -1668,7 +1669,8 @@ enum mlx5_txcmp_code {
 			 */
 			rte_pktmbuf_attach_extbuf(pkt, buf_addr, buf_iova,
 						  buf_len, shinfo);
-			rte_pktmbuf_reset_headroom(pkt);
+			/* Set mbuf head-room. */
+			pkt->data_off = headroom_sz;
 			assert(pkt->ol_flags == EXT_ATTACHED_MBUF);
 			/*
 			 * Prevent potential overflow due to MTU change through
diff --git a/drivers/net/mlx5/mlx5_rxtx.h b/drivers/net/mlx5/mlx5_rxtx.h
index bbd9b31..4252832 100644
--- a/drivers/net/mlx5/mlx5_rxtx.h
+++ b/drivers/net/mlx5/mlx5_rxtx.h
@@ -114,7 +114,8 @@ struct mlx5_rxq_data {
 	unsigned int strd_sz_n:4; /* Log 2 of stride size. */
 	unsigned int strd_shift_en:1; /* Enable 2bytes shift on a stride. */
 	unsigned int err_state:2; /* enum mlx5_rxq_err_state. */
-	unsigned int :4; /* Remaining bits. */
+	unsigned int strd_headroom_en:1; /* Enable mbuf headroom in MPRQ. */
+	unsigned int :3; /* Remaining bits. */
 	volatile uint32_t *rq_db;
 	volatile uint32_t *cq_db;
 	uint16_t port_id;
-- 
1.8.3.1