netdev - Re: [PATCH net 1/2] mlx5: fix possible ptp queue fifo overflow

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Message-ID: <Y9GSKrk95A4/Xo68@x130>
Date:   Wed, 25 Jan 2023 12:33:46 -0800
From:   Saeed Mahameed <saeed@...nel.org>
To:     Vadim Fedorenko <vadfed@...a.com>
Cc:     Gal Pressman <gal@...dia.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        Aya Levin <ayal@...dia.com>,
        Saeed Mahameed <saeedm@...dia.com>,
        Jakub Kicinski <kuba@...nel.org>
Subject: Re: [PATCH net 1/2] mlx5: fix possible ptp queue fifo overflow

On 25 Jan 14:42, Vadim Fedorenko wrote:
>On 24/01/2023 14:39, Gal Pressman wrote:
>> Anyway, I'd like to zoom out for a second, the whole fifo was designed
>> under the assumption that completions are in-order (this is a guarantee
>> for all SQs, not just ptp ones!), this fix seems more of a bandage that
>> potentially hides a more severe issue.
>>
>>>
>>> It really shows that CQE are coming OOO sometimes.
>>
>> Can we reproduce it somehow?
>> Can you please try to update your firmware version? I'm quite confident
>> that this issue is fixed already.
>>

Hi Vadim, 

As Gal pointed out above,
we shouldn't be seeing OOO on TX data path, otherwise, what's the point
of the fifo ? Also you can't have a proper reseliency since it seems when
this OOO happen the skb_cc, which is derived from the we_counter seems to
fall out of range which makes me think it can be a completely random
value, so we can't really be protected from all OOO scenarios.

This is clearly a FW bug and we will get to the bottom of
this internally, Can you please create a bug request ?

For the SKB leak, I will take the 2nd patch as is and improve it as
necessary if that's ok with you.

Thanks,
Saeed.