Re: [PATCH net-next 2/2] net/mlx5e: Add DCB_CAP_DCBX_LLD_MANAGED support in setdcbx

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] net/mlx5e: DCBX capabilities update silently ignored and LLD_MANAGED missing on boot
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commit 64b98b95142563c858de976f308b2006891e9c00
Author: Alexei Lazar <alazar@nvidia.com>

net/mlx5e: Add DCB_CAP_DCBX_LLD_MANAGED support in setdcbx

Add support for DCB_CAP_DCBX_LLD_MANAGED, which indicates that DCBX
negotiation is performed by the firmware/LLD agent rather than the host.
When DCB_CAP_DCBX_LLD_MANAGED is requested, switch to
firmware-controlled DCBX mode.

> diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_dcbnl.c b/drivers/net/ethernet/mellanox/mlx5/core/en_dcbnl.c
> index 4eef929f5ae9b..68deedb6f82ec 100644
> --- a/drivers/net/ethernet/mellanox/mlx5/core/en_dcbnl.c
> +++ b/drivers/net/ethernet/mellanox/mlx5/core/en_dcbnl.c
> @@ -439,9 +439,6 @@ static u8 mlx5e_dcbnl_setdcbx(struct net_device *dev, u8 mode)
>  	struct mlx5e_dcbx *dcbx = &priv->dcbx;
>  	enum mlx5_dcbx_oper_mode target_mode;
>  
> -	if (mode & DCB_CAP_DCBX_LLD_MANAGED)
> -		return 1;
> -

[Severity: Medium]
If a user issues a setdcbx request to modify capabilities (like CEE/IEEE)
but keeps the same DCB_CAP_DCBX_HOST bit, target_mode won't change.  Will
this cause the function to return 0 early and skip the dcbx->cap update?

drivers/net/ethernet/mellanox/mlx5/core/en_dcbnl.c:mlx5e_dcbnl_setdcbx() {
	target_mode = new_is_host ? MLX5E_DCBX_PARAM_VER_OPER_HOST :
				    MLX5E_DCBX_PARAM_VER_OPER_AUTO;
	if (dcbx->mode == target_mode)
		return 0;
	...
	dcbx->cap = mode;
}

This appears to be a functional regression introduced when the switch-to-host
and switch-to-auto logic was folded into one path.

Additionally, since DCB_CAP_DCBX_LLD_MANAGED is now supported, does the
initialization logic need to be updated to report it in AUTO mode on boot?

drivers/net/ethernet/mellanox/mlx5/core/en_dcbnl.c:mlx5e_dcbnl_initialize() {
	priv->dcbx.cap = DCB_CAP_DCBX_VER_CEE |
			 DCB_CAP_DCBX_VER_IEEE;
	if (priv->dcbx.mode == MLX5E_DCBX_PARAM_VER_OPER_HOST)
		priv->dcbx.cap |= DCB_CAP_DCBX_HOST;
	...
}

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Sashiko AI review · https://sashiko.dev/#/patchset/20261011112900.802150-1-tariqt@nvidia.com?part=2