linux-kernel - Re: [Intel-wired-lan] [PATCH v2 net] ixgbe: allow to increase MTU to some extent with XDP enabled

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Date:   Wed, 1 Feb 2023 12:15:02 +0100
From:   Alexander Lobakin <alexandr.lobakin@...el.com>
To:     Jason Xing <kerneljasonxing@...il.com>
CC:     Maciej Fijalkowski <maciej.fijalkowski@...el.com>,
        <jesse.brandeburg@...el.com>, <anthony.l.nguyen@...el.com>,
        <davem@...emloft.net>, <edumazet@...gle.com>, <kuba@...nel.org>,
        <pabeni@...hat.com>, <richardcochran@...il.com>, <ast@...nel.org>,
        <daniel@...earbox.net>, <hawk@...nel.org>,
        <john.fastabend@...il.com>, <netdev@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <intel-wired-lan@...ts.osuosl.org>,
        <bpf@...r.kernel.org>, Jason Xing <kernelxing@...cent.com>
Subject: Re: [Intel-wired-lan] [PATCH v2 net] ixgbe: allow to increase MTU to
 some extent with XDP enabled

From: Jason Xing <kerneljasonxing@...il.com>
Date: Tue, 31 Jan 2023 19:23:59 +0800

> On Tue, Jan 31, 2023 at 7:08 PM Alexander Lobakin
> <alexandr.lobakin@...el.com> wrote:

[...]

>>>> You said in this thread that you've done several tests - what were they?
>>>
>>> Tests against XDP are running on the server side when MTU varies from
>>> 1500 to 3050 (not including ETH_HLEN, ETH_FCS_LEN and VLAN_HLEN) for a
>>
> 
>> BTW, if ixgbe allows you to set MTU of 3050, it needs to be fixed. Intel
>> drivers at some point didn't include the second VLAN tag into account,
> 
> Yes, I noticed that.
> 
> It should be like "int new_frame_size = new_mtu + ETH_HLEN +
> ETH_FCS_LEN + (VLAN_HLEN * 2)" instead of only one VLAN_HLEN, which is
> used to compute real size in ixgbe_change_mtu() function.
> I'm wondering if I could submit another patch to fix the issue you
> mentioned because the current patch tells a different issue. Does it
> make sense?

Yes, please send as a separate patch. It's somewhat related to the
topic, but better to keep commits atomic.

> 
> If you're available, please help me review the v3 patch I've already
> sent to the mailing-list. Thanks anyway.
> The Link is https://lore.kernel.org/lkml/20230131032357.34029-1-kerneljasonxing@gmail.com/
> .
> 
> Thanks,
> Jason

Thanks,
Olek