[PATCH 2/2] net/mlx5: update flow devarg handling for future HW

[Maayan Kashani]

Hi,
Please revert this series.

Regards,
Maayan Kashani

> -----Original Message-----
> From: Maayan Kashani <mkashani at nvidia.com>
> Sent: Thursday, 6 November 2025 10:38
> To: dev at dpdk.org
> Cc: Maayan Kashani <mkashani at nvidia.com>; Raslan Darawsheh
> <rasland at nvidia.com>; Dariusz Sosnowski <dsosnowski at nvidia.com>; Slava
> Ovsiienko <viacheslavo at nvidia.com>; Bing Zhao <bingz at nvidia.com>; Ori
> Kam <orika at nvidia.com>; Suanming Mou <suanmingm at nvidia.com>;
> Matan Azrad <matan at nvidia.com>
> Subject: [PATCH 2/2] net/mlx5: update flow devarg handling for future HW
> 
> SWS (software steering) will be disabled on future hardware generations.
> Update the defaults for the dv_flow_en and allow_duplicate_pattern devargs
> accordingly.
> 
> - Default dv_flow_en devarg value will be chosen based on whether
>   NIC supports SW steering and/or HW steering.
> - If DV flow is not supported and allow_duplicate_pattern is
>   set by the user, forcibly disable it and emit a clear log message.
> 
> This change improves reliability by ensuring only valid configurations are
> applied, and provides clear feedback to the user when fallbacks are
> triggered.
> 
> Signed-off-by: Maayan Kashani <mkashani at nvidia.com>
> Acked-by: Dariusz Sosnowski <dsosnowski at nvidia.com>
> ---
>  doc/guides/nics/mlx5.rst | 11 +++++--
>  drivers/net/mlx5/mlx5.c  | 71 ++++++++++++++++++++++++++++++++++++++-
> -
>  2 files changed, 77 insertions(+), 5 deletions(-)
> 
> diff --git a/doc/guides/nics/mlx5.rst b/doc/guides/nics/mlx5.rst index
> 37495359d4f..91983089702 100644
> --- a/doc/guides/nics/mlx5.rst
> +++ b/doc/guides/nics/mlx5.rst
> @@ -694,8 +694,11 @@ for an additional list of options shared with other
> mlx5 drivers.
>    Value 2 enables the WQE based hardware steering.
>    In this mode, only queue-based flow management is supported.
> 
> -  It is configured by default to 1 (DV flow steering) if supported.
> -  Otherwise, the value is 0 which indicates legacy Verbs flow offloading.
> +  By default, the PMD will set this value according to capability.
> +  If DV flow steering is supported, it will be set to 1.
> +  If DV flow steering is not supported and HW steering is supported,
> + then it will be set to 2.
> +  Otherwise, it will be set to 0.
> 
>  - ``dv_esw_en`` parameter [int]
> 
> @@ -838,8 +841,10 @@ for an additional list of options shared with other
> mlx5 drivers.
>    - 1. Allow insertion of rules with the same pattern items.
>      In this case, all rules are inserted but only the first rule takes effect,
>      the next rule takes effect only if the previous rules are deleted.
> +    This option is not supported in :ref:`HWS mode <mlx5_hws>`.
> +    If this option is set to 1 in HWS mode, it will be set to 0.
> 
> -  By default, the PMD will set this value to 1.
> +  By default, the PMD will set this value according to capability.
> 
> 
>  .. _mlx5_net_stats:
> diff --git a/drivers/net/mlx5/mlx5.c b/drivers/net/mlx5/mlx5.c index
> ea235cf36be..dd3460f8d4b 100644
> --- a/drivers/net/mlx5/mlx5.c
> +++ b/drivers/net/mlx5/mlx5.c
> @@ -1443,6 +1443,45 @@ mlx5_dev_args_check_handler(const char *key,
> const char *val, void *opaque)
>  	return 0;
>  }
> 
> +static bool
> +mlx5_hws_is_supported(struct mlx5_dev_ctx_shared *sh) {
> +	return (sh->cdev->config.devx &&
> +	       sh->cdev->config.hca_attr.wqe_based_flow_table_sup);
> +}
> +
> +static bool
> +mlx5_sws_is_any_supported(struct mlx5_dev_ctx_shared *sh) {
> +	struct mlx5_common_device *cdev = sh->cdev;
> +	struct mlx5_hca_attr *hca_attr = &cdev->config.hca_attr;
> +
> +	if (hca_attr->rx_sw_owner_v2 || hca_attr->rx_sw_owner)
> +		return true;
> +
> +	if (hca_attr->tx_sw_owner_v2 || hca_attr->tx_sw_owner)
> +		return true;
> +
> +	if (hca_attr->eswitch_manager && (hca_attr->esw_sw_owner_v2 ||
> hca_attr->esw_sw_owner))
> +		return true;
> +
> +	return false;
> +}
> +
> +static bool
> +mlx5_kvargs_is_used(struct mlx5_kvargs_ctrl *mkvlist, const char *key)
> +{
> +	const struct rte_kvargs_pair *pair;
> +	uint32_t i;
> +
> +	for (i = 0; i < mkvlist->kvlist->count; ++i) {
> +		pair = &mkvlist->kvlist->pairs[i];
> +		if (strcmp(pair->key, key) == 0 && mkvlist->is_used[i])
> +			return true;
> +	}
> +	return false;
> +}
> +
>  /**
>   * Parse user device parameters and adjust them according to device
>   * capabilities.
> @@ -1484,6 +1523,8 @@ mlx5_shared_dev_ctx_args_config(struct
> mlx5_dev_ctx_shared *sh,
>  	int ret = 0;
>  	size_t alignment = rte_mem_page_size();
>  	uint32_t max_queue_umem_size = MLX5_WQE_SIZE *
> mlx5_dev_get_max_wq_size(sh);
> +	bool hws_is_supported = mlx5_hws_is_supported(sh);
> +	bool sws_is_supported = mlx5_sws_is_any_supported(sh);
> 
>  	if (alignment == (size_t)-1) {
>  		alignment = (1 << MLX5_LOG_PAGE_SIZE); @@ -1494,9
> +1535,15 @@ mlx5_shared_dev_ctx_args_config(struct
> mlx5_dev_ctx_shared *sh,
>  	memset(config, 0, sizeof(*config));
>  	config->vf_nl_en = 1;
>  	config->dv_esw_en = 1;
> -	config->dv_flow_en = 1;
> +	if (!sws_is_supported && hws_is_supported)
> +		config->dv_flow_en = 2;
> +	else
> +		config->dv_flow_en = 1;
>  	config->decap_en = 1;
> -	config->allow_duplicate_pattern = 1;
> +	if (config->dv_flow_en == 2)
> +		config->allow_duplicate_pattern = 0;
> +	else
> +		config->allow_duplicate_pattern = 1;
>  	config->fdb_def_rule = 1;
>  	config->cnt_svc.cycle_time = MLX5_CNT_SVC_CYCLE_TIME_DEFAULT;
>  	config->cnt_svc.service_core = rte_get_main_lcore(); @@ -1517,6
> +1564,26 @@ mlx5_shared_dev_ctx_args_config(struct
> mlx5_dev_ctx_shared *sh,
>  		DRV_LOG(WARNING, "DV flow is not supported.");
>  		config->dv_flow_en = 0;
>  	}
> +	/* Inform user if DV flow is not supported. */
> +	if (config->dv_flow_en == 1 && !sws_is_supported &&
> hws_is_supported) {
> +		DRV_LOG(WARNING, "DV flow is not supported. Changing to
> HWS mode.");
> +		config->dv_flow_en = 2;
> +	}
> +	/* Handle allow_duplicate_pattern based on final dv_flow_en mode.
> +	 * HWS mode (dv_flow_en=2) doesn't support duplicate patterns.
> +	 * Warn only if user explicitly requested an incompatible setting.
> +	 */
> +	bool allow_dup_pattern_set = mkvlist != NULL &&
> +		mlx5_kvargs_is_used(mkvlist,
> MLX5_ALLOW_DUPLICATE_PATTERN);
> +	if (config->dv_flow_en == 2) {
> +		if (config->allow_duplicate_pattern == 1 &&
> allow_dup_pattern_set)
> +			DRV_LOG(WARNING, "Duplicate pattern is not
> supported with HWS. Disabling it.");
> +		config->allow_duplicate_pattern = 0;
> +	} else if (!allow_dup_pattern_set) {
> +		/* Non-HWS mode: set default to 1 only if not explicitly set by
> user */
> +		config->allow_duplicate_pattern = 1;
> +	}
> +
>  	if (config->dv_esw_en && !sh->dev_cap.dv_esw_en) {
>  		DRV_LOG(DEBUG, "E-Switch DV flow is not supported.");
>  		config->dv_esw_en = 0;
> --
> 2.21.0