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

[Slava Ovsiienko]

Hi, Igor

Thank you for the patch.

1. The absolute max descriptor number supported by ConnectX hardware is 32768.
2. The actual max descriptor number supported by the port (and its related representors)
    reported in log_max_wq_sz in HCA.caps.  This value should be queried and save in mlx5_devx_cmd_query_hca_attr() routine.
3. mlx5_rx_queue_pre_setup() should check requested descriptor number and reject if it exceeds log_max_wq_sz
4. Please, format your patch according to the "fix" template.

With best regards,
Slava

> -----Original Message-----
> From: Igor Gutorov <igootorov at gmail.com>
> Sent: Sunday, June 16, 2024 8:38 PM
> To: Dariusz Sosnowski <dsosnowski at nvidia.com>; Slava Ovsiienko
> <viacheslavo at nvidia.com>; Ori Kam <orika at nvidia.com>; Suanming Mou
> <suanmingm at nvidia.com>; Matan Azrad <matan at nvidia.com>
> Cc: dev at dpdk.org; Igor Gutorov <igootorov at gmail.com>
> Subject: [PATCH 1/1] net/mlx5: show rx/tx descriptor ring limitations in
> rte_eth_dev_info
> 
> 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