[PATCH 1/1] net/mlx5: show rx/tx descriptor ring limitations in rte_eth_dev_info

[Igor Gutorov]

Currently, rte_eth_dev_info.rx_desc_lim.nb_max shows 65535 as a limit,
which results in a few problems:

* It is an incorrect value
* Allocating an RX queue and passing `rx_desc_lim.nb_max` results in an
  integer overflow and 0 ring size:

```
rte_eth_rx_queue_setup(0, 0, rx_desc_lim.nb_max, 0, NULL, mb_pool);
```

Which overflows ring size and generates the following log:
```
mlx5_net: port 0 increased number of descriptors in Rx queue 0 to the
next power of two (0)
```

This patch fixes these issues.

Signed-off-by: Igor Gutorov <igootorov at gmail.com>
---
 drivers/net/mlx5/mlx5_defs.h   | 3 +++
 drivers/net/mlx5/mlx5_ethdev.c | 5 ++++-
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/net/mlx5/mlx5_defs.h b/drivers/net/mlx5/mlx5_defs.h
index dc5216cb24..df608f0921 100644
--- a/drivers/net/mlx5/mlx5_defs.h
+++ b/drivers/net/mlx5/mlx5_defs.h
@@ -84,6 +84,9 @@
 #define MLX5_RX_DEFAULT_BURST 64U
 #define MLX5_TX_DEFAULT_BURST 64U
 
+/* Maximum number of descriptors in an RX/TX ring */
+#define MLX5_MAX_RING_DESC 8192
+
 /* Number of packets vectorized Rx can simultaneously process in a loop. */
 #define MLX5_VPMD_DESCS_PER_LOOP      4
 
diff --git a/drivers/net/mlx5/mlx5_ethdev.c b/drivers/net/mlx5/mlx5_ethdev.c
index aea799341c..d5be1ff1aa 100644
--- a/drivers/net/mlx5/mlx5_ethdev.c
+++ b/drivers/net/mlx5/mlx5_ethdev.c
@@ -22,6 +22,7 @@
 
 #include <mlx5_malloc.h>
 
+#include "mlx5_defs.h"
 #include "mlx5_rxtx.h"
 #include "mlx5_rx.h"
 #include "mlx5_tx.h"
@@ -345,6 +346,8 @@ mlx5_dev_infos_get(struct rte_eth_dev *dev, struct rte_eth_dev_info *info)
 	info->flow_type_rss_offloads = ~MLX5_RSS_HF_MASK;
 	mlx5_set_default_params(dev, info);
 	mlx5_set_txlimit_params(dev, info);
+	info->rx_desc_lim.nb_max = MLX5_MAX_RING_DESC;
+	info->tx_desc_lim.nb_max = MLX5_MAX_RING_DESC;
 	if (priv->sh->cdev->config.hca_attr.mem_rq_rmp &&
 	    priv->obj_ops.rxq_obj_new == devx_obj_ops.rxq_obj_new)
 		info->dev_capa |= RTE_ETH_DEV_CAPA_RXQ_SHARE;
@@ -774,7 +777,7 @@ mlx5_hairpin_cap_get(struct rte_eth_dev *dev, struct rte_eth_hairpin_cap *cap)
 	cap->max_nb_queues = UINT16_MAX;
 	cap->max_rx_2_tx = 1;
 	cap->max_tx_2_rx = 1;
-	cap->max_nb_desc = 8192;
+	cap->max_nb_desc = MLX5_MAX_RING_DESC;
 	hca_attr = &priv->sh->cdev->config.hca_attr;
 	cap->rx_cap.locked_device_memory = hca_attr->hairpin_data_buffer_locked;
 	cap->rx_cap.rte_memory = 0;
-- 
2.45.2