netdev - Re: [PATCH net-next v3 2/7] bnxt_en: add support for tcp-data-split ethtool command

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Message-ID: <CAMArcTWQijQ5S44rJzrpNWrbgo6hyJiyUddcuA6ZoegZmkvTLg@mail.gmail.com>
Date: Sat, 2 Nov 2024 02:11:00 +0900
From: Taehee Yoo <ap420073@...il.com>
To: Jakub Kicinski <kuba@...nel.org>
Cc: davem@...emloft.net, pabeni@...hat.com, edumazet@...gle.com, 
	almasrymina@...gle.com, netdev@...r.kernel.org, linux-doc@...r.kernel.org, 
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Subject: Re: [PATCH net-next v3 2/7] bnxt_en: add support for tcp-data-split
 ethtool command

On Fri, Nov 1, 2024 at 8:56 AM Jakub Kicinski <kuba@...nel.org> wrote:
>
> On Fri, 1 Nov 2024 02:34:59 +0900 Taehee Yoo wrote:
> > While I'm writing a patch I face an ambiguous problem here.
> > ethnl_set_ring() first calls .get_ringparam() to get current config.
> > Then it calls .set_ringparam() after it sets the current config + new
> > config to param structures.
> > The bnxt_set_ringparam() may receive ETHTOOL_TCP_DATA_SPLIT_ENABLED
> > because two cases.
> > 1. from user
> > 2. from bnxt_get_ringparam() because of UNKNWON.
> > The problem is that the bnxt_set_ringparam() can't distinguish them.
> > The problem scenario is here.
> > 1. tcp-data-split is UNKNOWN mode.
> > 2. HDS is automatically enabled because one of LRO or GRO is enabled.
> > 3. user changes ring parameter with following command
> > `ethtool -G eth0 rx 1024`
> > 4. ethnl_set_rings() calls .get_ringparam() to get current config.
> > 5. bnxt_get_ringparam() returns ENABLE of HDS because of UNKNWON mode.
> > 6. ethnl_set_rings() calls .set_ringparam() after setting param with
> > configs comes from .get_ringparam().
> > 7. bnxt_set_ringparam() is passed ETHTOOL_TCP_DATA_SPLIT_ENABLED but
> > the user didn't set it explicitly.
> > 8. bnxt_set_ringparam() eventually force enables tcp-data-split.
> >
> > I couldn't find a way to distinguish them so far.
> > I'm not sure if this is acceptable or not.
> > Maybe we need to modify a scenario?
>
> I thought we discussed this, but I may be misremembering.
> You may need to record in the core whether the setting came
> from the user or not (similarly to IFF_RXFH_CONFIGURED).
> User setting UNKNWON would mean "reset".
> Maybe I'm misunderstanding..

Thanks a lot for that!
I will try to add a new variable, that indicates tcp-data-split is set by
user. It would be the tcp_data_split_mod in the
kernel_ethtool_ringparam structure.

Thanks a lot!
Taehee Yoo