Re: [PATCH] net/mlx5e: allocate 'indirection_rqt' buffer dynamically

[Tariq Toukan <ttoukan.linux@xxxxxxxxx>]

On 3/8/2021 5:32 PM, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@xxxxxxxx>
>
> Increasing the size of the indirection_rqt array from 128 to 256 bytes
> pushed the stack usage of the mlx5e_hairpin_fill_rqt_rqns() function
> over the warning limit when building with clang and CONFIG_KASAN:
>
> drivers/net/ethernet/mellanox/mlx5/core/en_tc.c:970:1: error: stack frame size of 1180 bytes in function 'mlx5e_tc_add_nic_flow' [-Werror,-Wframe-larger-than=]
>
> Using dynamic allocation here is safe because the caller does the
> same, and it reduces the stack usage of the function to just a few
> bytes.
>
> Fixes: 1dd55ba2fb70 ("net/mlx5e: Increase indirection RQ table size to 256")
> Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
> ---
>   drivers/net/ethernet/mellanox/mlx5/core/en_tc.c | 16 +++++++++++++---
>   1 file changed, 13 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_tc.c b/drivers/net/ethernet/mellanox/mlx5/core/en_tc.c
> index 0da69b98f38f..66f98618dc13 100644
> --- a/drivers/net/ethernet/mellanox/mlx5/core/en_tc.c
> +++ b/drivers/net/ethernet/mellanox/mlx5/core/en_tc.c
> @@ -445,12 +445,16 @@ static void mlx5e_hairpin_destroy_transport(struct mlx5e_hairpin *hp)
>   	mlx5_core_dealloc_transport_domain(hp->func_mdev, hp->tdn);
>   }
>   
> -static void mlx5e_hairpin_fill_rqt_rqns(struct mlx5e_hairpin *hp, void *rqtc)
> +static int mlx5e_hairpin_fill_rqt_rqns(struct mlx5e_hairpin *hp, void *rqtc)
>   {
> -	u32 indirection_rqt[MLX5E_INDIR_RQT_SIZE], rqn;
> +	u32 *indirection_rqt, rqn;
>   	struct mlx5e_priv *priv = hp->func_priv;
>   	int i, ix, sz = MLX5E_INDIR_RQT_SIZE;
>   
> +	indirection_rqt = kzalloc(sz, GFP_KERNEL);
> +	if (!indirection_rqt)
> +		return -ENOMEM;
> +
>   	mlx5e_build_default_indir_rqt(indirection_rqt, sz,
>   				      hp->num_channels);
>   
> @@ -462,6 +466,9 @@ static void mlx5e_hairpin_fill_rqt_rqns(struct mlx5e_hairpin *hp, void *rqtc)
>   		rqn = hp->pair->rqn[ix];
>   		MLX5_SET(rqtc, rqtc, rq_num[i], rqn);
>   	}
> +
> +	kfree(indirection_rqt);
> +	return 0;
>   }
>   
>   static int mlx5e_hairpin_create_indirect_rqt(struct mlx5e_hairpin *hp)
> @@ -482,12 +489,15 @@ static int mlx5e_hairpin_create_indirect_rqt(struct mlx5e_hairpin *hp)
>   	MLX5_SET(rqtc, rqtc, rqt_actual_size, sz);
>   	MLX5_SET(rqtc, rqtc, rqt_max_size, sz);
>   
> -	mlx5e_hairpin_fill_rqt_rqns(hp, rqtc);
> +	err = mlx5e_hairpin_fill_rqt_rqns(hp, rqtc);
> +	if (err)
> +		goto out;
>   
>   	err = mlx5_core_create_rqt(mdev, in, inlen, &hp->indir_rqt.rqtn);
>   	if (!err)
>   		hp->indir_rqt.enabled = true;
>   
> +out:
>   	kvfree(in);
>   	return err;
>   }

Reviewed-by: Tariq Toukan <tariqt@xxxxxxxxxx>
Thanks for your patch.

Tariq