netdev - Re: Potential regression/bug in net/mlx5 driver

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Message-ID: <ZDiDbQL5ksMwaMeB@x130>
Date:   Thu, 13 Apr 2023 15:34:21 -0700
From:   Saeed Mahameed <saeedm@...dia.com>
To:     Jakub Kicinski <kuba@...nel.org>
Cc:     Paul Moore <paul@...l-moore.com>,
        Leon Romanovsky <leon@...nel.org>,
        Linux regressions mailing list <regressions@...ts.linux.dev>,
        Saeed Mahameed <saeed@...nel.org>,
        Shay Drory <shayd@...dia.com>, netdev@...r.kernel.org,
        selinux@...r.kernel.org, Tariq Toukan <tariqt@...dia.com>
Subject: Re: Potential regression/bug in net/mlx5 driver

On 13 Apr 15:21, Jakub Kicinski wrote:
>On Thu, 13 Apr 2023 14:12:49 -0700 Saeed Mahameed wrote:
>> This is a high priority and we are working on this, unfortunately for mlx5
>> we don't check FW versions since we support more than 6 different devices
>> already, with different FW production lines.
>>
>> So we believe that this bug is very hard to solve without breaking backward
>> compatibility with the currently supported working FWs, the issue exists only
>> on very old firmwares and we will recommend a firmware upgrade to resolve this
>> issue.
>
>On a closer read I don't like what this patch is doing at all.
>I'm not sure we have precedent for "management connection" functions.
>This requires a larger discussion. And after looking up the patch set

But this management connection function has the same architecture as other
"Normal" mlx5 functions, from the driver pov. The same way mlx5 
doesn't care if the underlaying function is CX4/5/6 we don't care if it was
a "management function".

We are currently working on enabling a subset of netdev functionality using
the same mlx5 constructs and current mlx5e code to load up a mlx5e netdev
on it.. 

>it went in, it seems to have been one of the hastily merged ones.
>I'm sending a revert.

But let's discuss what's wrong with it, and what are your thoughts ? 
the fact that it breaks a 6 years OLD FW, doesn't make it so horrible.

The patchset is a bug fix where previous mlx5 load on such function failed 
with some nasty kernel log messages, so the patchset only provides a fix to
make mlx5 load on such function go smooth and avoid loading any interface
on that function until we provide the patches for that which is a WIP right
now.