netdev - Re: [PATCH] net/mlx5: reduce stack usage in qp_read

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Date:   Thu, 30 Apr 2020 08:21:57 +0300
From:   Leon Romanovsky <leon@...nel.org>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     Saeed Mahameed <saeedm@...lanox.com>,
        "David S. Miller" <davem@...emloft.net>,
        Moshe Shemesh <moshe@...lanox.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        netdev@...r.kernel.org, linux-rdma@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] net/mlx5: reduce stack usage in qp_read_field

On Tue, Apr 28, 2020 at 11:23:47PM +0200, Arnd Bergmann wrote:
> Moving the mlx5_ifc_query_qp_out_bits structure on the stack was a bit
> excessive and now causes the compiler to complain on 32-bit architectures:
>
> drivers/net/ethernet/mellanox/mlx5/core/debugfs.c: In function 'qp_read_field':
> drivers/net/ethernet/mellanox/mlx5/core/debugfs.c:274:1: error: the frame size of 1104 bytes is larger than 1024 bytes [-Werror=frame-larger-than=]
>
> Revert the previous patch partially to use dynamically allocation as
> the code did before. Unfortunately there is no good error handling
> in case the allocation fails.
>
> Fixes: 57a6c5e992f5 ("net/mlx5: Replace hand written QP context struct with automatic getters")
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> ---
>  drivers/net/ethernet/mellanox/mlx5/core/debugfs.c | 12 +++++++++---
>  1 file changed, 9 insertions(+), 3 deletions(-)

Thanks Arnd, I'll pick it to mlx5-next.

I was under impression that the frame size was increased a long
time ago. Is this 1K limit still effective for all archs?
Or is it is 32-bit leftover?

Thanks