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Message-ID: <d9529518-c6f5-c64f-d635-95da64ed6d65@intel.com>
Date: Wed, 6 Mar 2024 16:27:36 -0800
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Subject: Re: [PATCH] i40e: Prevent setting MTU if greater than MFS
To: Erwan Velu <erwanaliasr1@gmail.com>
CC: Erwan Velu <e.velu@criteo.com>, Jesse Brandeburg
	<jesse.brandeburg@intel.com>, "David S. Miller" <davem@davemloft.net>, "Eric
 Dumazet" <edumazet@google.com>, Jakub Kicinski <kuba@kernel.org>, Paolo Abeni
	<pabeni@redhat.com>, <intel-wired-lan@lists.osuosl.org>,
	<netdev@vger.kernel.org>, <linux-kernel@vger.kernel.org>
References: <20240227192704.376176-1-e.velu@criteo.com>
 <827d22da-fb32-1012-422d-d283b28ce5ec@intel.com>
 <CAL2Jzuzf54qcsCM4CAUOLaogWrBL=Mm4ma_4pRbaf8A=dZeOFQ@mail.gmail.com>
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From: Tony Nguyen <anthony.l.nguyen@intel.com>
In-Reply-To: <CAL2Jzuzf54qcsCM4CAUOLaogWrBL=Mm4ma_4pRbaf8A=dZeOFQ@mail.gmail.com>
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On 3/4/2024 6:22 PM, Erwan Velu wrote:
> I was also wondering if I shouldn't subtract I40E_PACKET_HDR_PAD from
> the mfs to be more accurate, can you confirm this ?

Yes, you're correct, we should take the packet header out however...

> If one can have a look at what is the exact procedure to fix the MFS
> size when too small, that would be lovely/ideal in addition to my
> patch.

.. as you allude to here, we should resolve the MFS size issue.

You were on that right track (as mentioned in your commit message)

 > To fix this case, it would have been ideal to increase the MFS,
 > via i40e_aqc_opc_set_mac_config, but I didn't found a reliable way to 
do it.

The ice driver is doing this with the ice_aq_set_mac_cfg() call. You 
should be able to model the same here.

Thanks,
Tony