Re: [PATCH net-next 03/10] devlink: Serialize access to rate domains

Jakub Kicinski
2025-03-05T00:04:15Z

On Tue, 4 Mar 2025 14:11:40 +0100 Jiri Pirko wrote:
> Mon, Mar 03, 2025 at 11:06:23PM +0100, kuba@kernel.org wrote:
> >On Thu, 27 Feb 2025 13:22:25 +0100 Jiri Pirko wrote:
> >> Depends. On normal host sr-iov, no. On smartnic where you have PF in
> >> host, yes.
> >
> >Yet another "great choice" in mlx5 other drivers have foreseen
> >problems with and avoided.
>
> What do you mean? How else to model it? Do you suggest having PF devlink
> port for the PF that instantiates? That would sound like Uroboros to me.

I reckon it was always more obvious to those of us working on
NPU-derived devices, to which a PCIe port is just a PCIe port,
with no PCIe<>MAC "pipeline" to speak of.

The reason why having the "PF port" is a good idea is exactly
why we're having this conversation. If you don't you'll assign
to the global scope attributes which are really just port attributes.

> >> Looks like pretty much all current NICs are multi-PFs, aren't they?
> >
> >Not in a way which requires cross-port state sharing, no.
> >You should know this.
>
> This is not about cross-port state sharing. This is about per-PF
> configuration. What am I missing?

Maybe we lost the thread of the conversation.. :)
I'm looking at the next patch in this series and it says:

devlink: Introduce shared rate domains

The underlying idea is modeling a piece of hardware which:
1. Exposes multiple functions as separate devlink objects.
2. Is capable of instantiating a transmit scheduling tree spanning
multiple functions.

Modeling this requires devlink rate nodes with parents across other
devlink objects.

Are these domains are not cross port?