netdev - Re: [PATCH] net/mlx5e: Fix zero table prio set by user.

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Date:   Thu, 25 Jul 2019 21:22:36 +0000
From:   Saeed Mahameed <saeedm@...lanox.com>
To:     "wenxu@...oud.cn" <wenxu@...oud.cn>, Roi Dayan <roid@...lanox.com>,
        Or Gerlitz <ogerlitz@...lanox.com>,
        Mark Bloch <markb@...lanox.com>,
        Paul Blakey <paulb@...lanox.com>
CC:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [PATCH] net/mlx5e: Fix zero table prio set by user.

On Thu, 2019-07-25 at 19:24 +0800, wenxu@...oud.cn wrote:
> From: wenxu <wenxu@...oud.cn>
> 
> The flow_cls_common_offload prio is zero
> 
> It leads the invalid table prio in hw.
> 
> Error: Could not process rule: Invalid argument
> 
> kernel log:
> mlx5_core 0000:81:00.0: E-Switch: Failed to create FDB Table err -22
> (table prio: 65535, level: 0, size: 4194304)
> 
> table_prio = (chain * FDB_MAX_PRIO) + prio - 1;
> should check (chain * FDB_MAX_PRIO) + prio is not 0
> 
> Signed-off-by: wenxu <wenxu@...oud.cn>
> ---
>  drivers/net/ethernet/mellanox/mlx5/core/eswitch_offloads.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git
> a/drivers/net/ethernet/mellanox/mlx5/core/eswitch_offloads.c
> b/drivers/net/ethernet/mellanox/mlx5/core/eswitch_offloads.c
> index 089ae4d..64ca90f 100644
> --- a/drivers/net/ethernet/mellanox/mlx5/core/eswitch_offloads.c
> +++ b/drivers/net/ethernet/mellanox/mlx5/core/eswitch_offloads.c
> @@ -970,7 +970,9 @@ static int esw_add_fdb_miss_rule(struct 

this piece of code isn't in this function, weird how it got to the
diff, patch applies correctly though !

> mlx5_eswitch *esw)
>  		flags |= (MLX5_FLOW_TABLE_TUNNEL_EN_REFORMAT |
>  			  MLX5_FLOW_TABLE_TUNNEL_EN_DECAP);
>  
> -	table_prio = (chain * FDB_MAX_PRIO) + prio - 1;
> +	table_prio = (chain * FDB_MAX_PRIO) + prio;
> +	if (table_prio)
> +		table_prio = table_prio - 1;
>  

This is black magic, even before this fix.
this -1 seems to be needed in order to call
create_next_size_table(table_prio) with the previous "table prio" ?
(table_prio - 1)  ?

The whole thing looks wrong to me since when prio is 0 and chain is 0,
there is not such thing table_prio - 1.

mlnx eswitch guys in the cc, please advise.

Thanks,
Saeed.

>  	/* create earlier levels for correct fs_core lookup when
>  	 * connecting tables