[PATCH v2] net/mlx5: fix MPRQ stride size to accommodate the headroom

[Alexander Kozyrev]

The space for the headroom is reserved at the end of every MPRQ stride
for the next packet. The Rx burst logic is to copy any overlapping
packet data if there is an overlap with this reserved headroom space.
But it is not possible if the headroom size is bigger than the whole
stride. Adjust the stride size to make sure the stride size is greater
than the headroom size.

Fixes: 34776af600df ("net/mlx5: fix MPRQ stride devargs adjustment")

Signed-off-by: Alexander Kozyrev <akozyrev at nvidia.com>
---
 drivers/net/mlx5/mlx5.c     |  1 +
 drivers/net/mlx5/mlx5_rxq.c | 41 +++++++++++++++++++++++++------------
 2 files changed, 29 insertions(+), 13 deletions(-)

diff --git a/drivers/net/mlx5/mlx5.c b/drivers/net/mlx5/mlx5.c
index a75fa1b7f0..592e4053c5 100644
--- a/drivers/net/mlx5/mlx5.c
+++ b/drivers/net/mlx5/mlx5.c
@@ -2597,6 +2597,7 @@ mlx5_port_args_config(struct mlx5_priv *priv, struct mlx5_kvargs_ctrl *mkvlist,
 	config->mprq.max_memcpy_len = MLX5_MPRQ_MEMCPY_DEFAULT_LEN;
 	config->mprq.min_rxqs_num = MLX5_MPRQ_MIN_RXQS;
 	config->mprq.log_stride_num = MLX5_MPRQ_DEFAULT_LOG_STRIDE_NUM;
+	config->mprq.log_stride_size = MLX5_MPRQ_DEFAULT_LOG_STRIDE_SIZE;
 	config->log_hp_size = MLX5_ARG_UNSET;
 	config->std_delay_drop = 0;
 	config->hp_delay_drop = 0;
diff --git a/drivers/net/mlx5/mlx5_rxq.c b/drivers/net/mlx5/mlx5_rxq.c
index ad8fd13cbe..20e03146a5 100644
--- a/drivers/net/mlx5/mlx5_rxq.c
+++ b/drivers/net/mlx5/mlx5_rxq.c
@@ -1604,23 +1604,38 @@ mlx5_mprq_prepare(struct rte_eth_dev *dev, uint16_t idx, uint16_t desc,
 	} else {
 		*actual_log_stride_num = config->mprq.log_stride_num;
 	}
-	if (config->mprq.log_stride_size) {
-		/* Checks if chosen size of stride is in supported range. */
-		if (config->mprq.log_stride_size > log_max_stride_size ||
-		    config->mprq.log_stride_size < log_min_stride_size) {
-			*actual_log_stride_size = log_def_stride_size;
+	/* Checks if chosen size of stride is in supported range. */
+	if (config->mprq.log_stride_size > log_max_stride_size ||
+	    config->mprq.log_stride_size < log_min_stride_size) {
+		*actual_log_stride_size = log_def_stride_size;
+		DRV_LOG(WARNING,
+			"Port %u Rx queue %u size of a stride for Multi-Packet RQ is out of range, setting default value (%u)",
+			dev->data->port_id, idx,
+			RTE_BIT32(log_def_stride_size));
+	} else {
+		*actual_log_stride_size = config->mprq.log_stride_size;
+	}
+	/* Make the stride fit the mbuf size by default. */
+	if (*actual_log_stride_size == MLX5_MPRQ_DEFAULT_LOG_STRIDE_SIZE) {
+		if (min_mbuf_size <= RTE_BIT32(log_max_stride_size)) {
 			DRV_LOG(WARNING,
-				"Port %u Rx queue %u size of a stride for Multi-Packet RQ is out of range, setting default value (%u)",
-				dev->data->port_id, idx,
-				RTE_BIT32(log_def_stride_size));
+				"Port %u Rx queue %u size of a stride for Multi-Packet RQ is adjusted to match the mbuf size (%u)",
+				dev->data->port_id, idx, min_mbuf_size);
+			*actual_log_stride_size = log2above(min_mbuf_size);
 		} else {
-			*actual_log_stride_size = config->mprq.log_stride_size;
+			goto unsupport;
 		}
-	} else {
-		if (min_mbuf_size <= RTE_BIT32(log_max_stride_size))
-			*actual_log_stride_size = log2above(min_mbuf_size);
-		else
+	}
+	/* Make sure the stride size is greater than the headroom. */
+	if (RTE_BIT32(*actual_log_stride_size) < RTE_PKTMBUF_HEADROOM) {
+		if (RTE_BIT32(log_max_stride_size) > RTE_PKTMBUF_HEADROOM) {
+			DRV_LOG(WARNING,
+				"Port %u Rx queue %u size of a stride for Multi-Packet RQ is adjusted to accommodate the headroom (%u)",
+				dev->data->port_id, idx, RTE_PKTMBUF_HEADROOM);
+			*actual_log_stride_size = log2above(RTE_PKTMBUF_HEADROOM);
+		} else {
 			goto unsupport;
+		}
 	}
 	log_stride_wqe_size = *actual_log_stride_num + *actual_log_stride_size;
 	/* Check if WQE buffer size is supported by hardware. */
-- 
2.18.2