netdev - Re: [PATCH net-next V4 02/14] documentation: networking: add shared devlink documentation

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Message-ID: <vwdbowwy3eivqwwypwo2klexhu47qpvb6nevjg3st7a43ucmxl@tllljudder3l>
Date: Wed, 3 Dec 2025 11:36:13 +0100
From: Jiri Pirko <jiri@...nulli.us>
To: Jakub Kicinski <kuba@...nel.org>
Cc: Tariq Toukan <tariqt@...dia.com>, Eric Dumazet <edumazet@...gle.com>, 
	Paolo Abeni <pabeni@...hat.com>, Andrew Lunn <andrew+netdev@...n.ch>, 
	"David S. Miller" <davem@...emloft.net>, Donald Hunter <donald.hunter@...il.com>, 
	Jonathan Corbet <corbet@....net>, Saeed Mahameed <saeedm@...dia.com>, 
	Leon Romanovsky <leon@...nel.org>, Mark Bloch <mbloch@...dia.com>, netdev@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org, linux-rdma@...r.kernel.org, 
	Gal Pressman <gal@...dia.com>, Moshe Shemesh <moshe@...dia.com>, 
	Carolina Jubran <cjubran@...dia.com>, Cosmin Ratiu <cratiu@...dia.com>, Jiri Pirko <jiri@...dia.com>, 
	Randy Dunlap <rdunlap@...radead.org>
Subject: Re: [PATCH net-next V4 02/14] documentation: networking: add shared
 devlink documentation

Tue, Dec 02, 2025 at 07:14:44PM +0100, kuba@...nel.org wrote:
>On Tue, 2 Dec 2025 08:43:49 +0100 Jiri Pirko wrote:
>> Mon, Dec 01, 2025 at 10:49:54PM +0100, kuba@...nel.org wrote:
>> >On Mon, 1 Dec 2025 11:50:08 +0100 Jiri Pirko wrote:  
>> >> Correct. IFAIK there is one PF devlink instance per NUMA node.  
>> >
>> >You say "correct" and then disagree with what I'm saying. I said
>> >ports because a port is a devlink object. Not a devlink instance.  
>> 
>> Okay, you mean devlink_port. You would like to see NUMA node leg as
>> devlink_port? Having troubles to undestand exactly what you mean, lot of
>> guessing on my side. Probably I'm slow, sorry.
>> 
>> But there is a PCI device per NUMA node leg. Not sure how to model it.
>> Devink instances have 1:1 relationship with bus devices.
>> 
>> Care to draw a picture perhaps?
>> 
>> >> The shared instance on top would make sense to me. That was one of
>> >> motivations to introduce it. Then this shared instance would hold
>> >> netdev, vf representors etc.  
>> >
>> >I don't understand what the shared instance is representing and how
>> >user is expect to find their way thru the maze of devlink instanced,
>> >for real bus, aux bus, and now shared instanced.  
>> 
>> Well, I tried to desrtibe it in the documentation path, Not sure what is
>> not clear :/
>> 
>> Nested devlinks expose the connections between devlink instances.
>
>To be clear -- I understand how you're laying things out. My point is
>not about that. My question is how can user make intuitive sense of this
>mess of random object floating around. Every SW engineering problem can
>be solved by another layer of abstraction, that's not the challenge. 
>The challenge is to design those layers so that they make intuitive
>sense (to people who don't spend their life programming against mlx FW
>interfaces).

Well, this really has no relation to mlx FW interfaces. It is a generic
issue of having multiple PFs backed by 1 physical device sharing
resources. How to make things more intuitive, I don't know :/ Any
suggestion?