netdev - Re: [net-next PATCH v3 1/3] act_skbedit: skbedit queue mapping for receive queue

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Date:   Thu, 27 Oct 2022 10:12:37 +0300
From:   Roi Dayan <roid@...dia.com>
To:     Jakub Kicinski <kuba@...nel.org>
Cc:     Amritha Nambiar <amritha.nambiar@...el.com>,
        netdev@...r.kernel.org, alexander.duyck@...il.com,
        jhs@...atatu.com, jiri@...nulli.us, xiyou.wangcong@...il.com,
        vinicius.gomes@...el.com, sridhar.samudrala@...el.com,
        Maor Dickman <maord@...dia.com>,
        Tariq Toukan <tariqt@...dia.com>,
        Saeed Mahameed <saeedm@...dia.com>,
        Leon Romanovsky <leon@...nel.org>,
        Pablo Neira Ayuso <pablo@...filter.org>
Subject: Re: [net-next PATCH v3 1/3] act_skbedit: skbedit queue mapping for
 receive queue

On 26/10/2022 19:17, Jakub Kicinski wrote:
> On Wed, 26 Oct 2022 14:40:39 +0300 Roi Dayan wrote:
>> This patch broke mlx5_core TC offloads.
>> We have a generic code part going over the enum values and have a list
>> of action pointers to handle parsing each action without knowing the action.
>> The list of actions depends on being aligned with the values order of
>> the enum which I think usually new values should go to the end of the list.
>> I'm not sure if other code parts are broken from this change but at
>> least one part is.
>> New values were always inserted at the end.
>>
>> Can you make a fixup patch to move FLOW_ACTION_RX_QUEUE_MAPPING to
>> the end of the enum list?
>> i.e. right before NUM_FLOW_ACTIONS.
> 
> Odd, can you point us to the exact code that got broken?
> There are no guarantees on ordering of kernel-internal enum
> and I think it's a bad idea to make such precedent.

ok. I were in the thought order is kept.

You can see our usage in drivers/net/ethernet/mellanox/mlx5/core/en_tc.c
in function parse_tc_actions().
we loop over the actions and get a struct with function pointers
that represent the flow action and we use those function pointers
to parse whats needed without parse_tc_actions() knowing the action.

the function pointers are in drivers/net/ethernet/mellanox/mlx5/core/en/tc/act/act.c
see static struct mlx5e_tc_act *tc_acts_fdb[NUM_FLOW_ACTIONS].
each function handling code is in a different file under that sub folder.

if order is not important i guess i'll do a function to return the ops i need
per enum value.
please let me know if to continue this road.
thanks