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

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Message-ID: <20251201134954.6b8a8d48@kernel.org>
Date: Mon, 1 Dec 2025 13:49:54 -0800
From: Jakub Kicinski <kuba@...nel.org>
To: Jiri Pirko <jiri@...nulli.us>
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

On Mon, 1 Dec 2025 11:50:08 +0100 Jiri Pirko wrote:
> >> I'm not sure I follow. If there is only one PF bound, there is 1:1
> >> relationship. Depends on how many PFs of the same ASIC you have.  
> >
> >I'm talking about multi-PF devices. mlx5 supports multi-PF setup for
> >NUMA locality IIUC. In such configurations per-PF parameters can be
> >configured on PCI PF ports.  
> 
> 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.

> 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, the mutex protect the list of instances which are managed in the
> >> driver. If you want to move the mutex, I don't see how to do it without
> >> moving all the code related to shared devlink instances, including faux
> >> probe etc. Is that what you suggest?  
> >
> >Multiple ways you can solve it, but drivers should have to duplicate
> >all the instance management and locking. BTW please don't use guard().  
> 
> I'm having troubles to undestand what you say, sorry :/ Do you prefer to
> move the code from driver to devlink core or not?

I missed a "not".. drivers should _not_ have to duplicate, sorry.

> Regarding guard(), sure. I wonder how much more time it's gonna take
> since this resistentance fades out :)

guard() locks code instead of data accesses. We used to make fun of
Java in this community, you know.