[PATCH 21.11] net/mlx5: fix MPRQ stride size to accommodate the headroom

[Alexander Kozyrev <akozyrev@nvidia.com>]

[ upstream commit e6479f009fbd9c8e873807cc928dcf91a151aba9  ]

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: 	34776af600 ("net/mlx5: fix MPRQ stride devargs adjustment")

Signed-off-by: Alexander Kozyrev <akozyrev@nvidia.com>
Acked-by: Viacheslav Ovsiienko <viacheslavo@nvidia.com>
---
 drivers/net/mlx5/linux/mlx5_os.c |  1 +
 drivers/net/mlx5/mlx5_rxq.c      | 41 ++++++++++++++++++++++----------
 2 files changed, 29 insertions(+), 13 deletions(-)

diff --git a/drivers/net/mlx5/linux/mlx5_os.c b/drivers/net/mlx5/linux/mlx5_os.c
index e79b1a275c..ab69ee21ad 100644
--- a/drivers/net/mlx5/linux/mlx5_os.c
+++ b/drivers/net/mlx5/linux/mlx5_os.c
@@ -1202,6 +1202,7 @@ mlx5_dev_spawn(struct rte_device *dpdk_dev,
 	config->mprq.log_min_stride_wqe_size =
 			MLX5_MPRQ_LOG_MIN_STRIDE_WQE_SIZE;
 	config->mprq.log_stride_num = MLX5_MPRQ_DEFAULT_LOG_STRIDE_NUM;
+	config->mprq.log_stride_size = MLX5_MPRQ_DEFAULT_LOG_STRIDE_SIZE;
 	if (config->devx) {
 		config->mprq.log_min_stride_wqe_size =
 				config->hca_attr.log_min_stride_wqe_sz;
diff --git a/drivers/net/mlx5/mlx5_rxq.c b/drivers/net/mlx5/mlx5_rxq.c
index 47db585042..4a8fc8721d 100644
--- a/drivers/net/mlx5/mlx5_rxq.c
+++ b/drivers/net/mlx5/mlx5_rxq.c
@@ -1446,23 +1446,38 @@ 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