netdev - Re: [PATCH net-next V2 11/11] net/mlx5e: Support ethtool tcp-data-split settings

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Message-ID: <20250527091023.206faecb@kernel.org>
Date: Tue, 27 May 2025 09:10:23 -0700
From: Jakub Kicinski <kuba@...nel.org>
To: Saeed Mahameed <saeed@...nel.org>
Cc: Tariq Toukan <tariqt@...dia.com>, "David S. Miller"
 <davem@...emloft.net>, Paolo Abeni <pabeni@...hat.com>, Eric Dumazet
 <edumazet@...gle.com>, Andrew Lunn <andrew+netdev@...n.ch>, Saeed Mahameed
 <saeedm@...dia.com>, Leon Romanovsky <leon@...nel.org>, Richard Cochran
 <richardcochran@...il.com>, Alexei Starovoitov <ast@...nel.org>, Daniel
 Borkmann <daniel@...earbox.net>, Jesper Dangaard Brouer <hawk@...nel.org>,
 John Fastabend <john.fastabend@...il.com>, netdev@...r.kernel.org,
 linux-rdma@...r.kernel.org, linux-kernel@...r.kernel.org,
 bpf@...r.kernel.org, Moshe Shemesh <moshe@...dia.com>, Mark Bloch
 <mbloch@...dia.com>, Gal Pressman <gal@...dia.com>, Cosmin Ratiu
 <cratiu@...dia.com>, Dragos Tatulea <dtatulea@...dia.com>
Subject: Re: [PATCH net-next V2 11/11] net/mlx5e: Support ethtool
 tcp-data-split settings

On Thu, 22 May 2025 16:19:28 -0700 Saeed Mahameed wrote:
> >Why are you modifying wanted_features? wanted_features is what
> >*user space* wanted! You should probably operate on hw_features ?
> >Tho, may be cleaner to return an error and an extack if the user
> >tries to set HDS and GRO to conflicting values.
> >  
> 
> hw_features is hw capabilities, it doesn't mean on/off.. so no we can't
> rely on that.
> 
> To enable TCP_DATA_SPLIT we tie it to GRO_HW, so we enable GRO_HW when
> TCP_DATA_SPLIT is set to on and vise-versa. I agree not the cleanest.. 
> But it is good for user-visibility as you would see both ON if you query
> from user, which is the actual state. This is the only way to set HW_GRO
> to on by driver and not lose previous state when we turn the other bit
> on/off.

   features = on
hw_features = off

is how we indicate the feature is "on [fixed]"
Tho, I'm not sure how much precedent there is for making things fixed
at runtime.