linux-kernel - Re: [RFC net-next v2 1/2] devlink: add whole device devlink instance

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Message-ID: <wf5ugq4h4lv2uic3622xurjbfwf534gj2jx6jbhaxoncingb3z@ceo4xkikjbdn>
Date: Mon, 24 Feb 2025 14:03:39 +0100
From: Jiri Pirko <jiri@...nulli.us>
To: Jakub Kicinski <kuba@...nel.org>
Cc: Przemek Kitszel <przemyslaw.kitszel@...el.com>, 
	intel-wired-lan@...ts.osuosl.org, Tony Nguyen <anthony.l.nguyen@...el.com>, 
	Cosmin Ratiu <cratiu@...dia.com>, Tariq Toukan <tariqt@...dia.com>, netdev@...r.kernel.org, 
	Konrad Knitter <konrad.knitter@...el.com>, Jacob Keller <jacob.e.keller@...el.com>, davem@...emloft.net, 
	Eric Dumazet <edumazet@...gle.com>, Paolo Abeni <pabeni@...hat.com>, Andrew Lunn <andrew@...n.ch>, 
	linux-kernel@...r.kernel.org, ITP Upstream <nxne.cnse.osdt.itp.upstreaming@...el.com>, 
	Carolina Jubran <cjubran@...dia.com>
Subject: Re: [RFC net-next v2 1/2] devlink: add whole device devlink instance

Fri, Feb 21, 2025 at 02:45:12AM +0100, kuba@...nel.org wrote:
>On Wed, 19 Feb 2025 17:32:54 +0100 Przemek Kitszel wrote:
>> Add a support for whole device devlink instance. Intented as a entity
>> over all PF devices on given physical device.
>> 
>> In case of ice driver we have multiple PF devices (with their devlink
>> dev representation), that have separate drivers loaded. However those
>> still do share lots of resources due to being the on same HW. Examples
>> include PTP clock and RSS LUT. Historically such stuff was assigned to
>> PF0, but that was both not clear and not working well. Now such stuff
>> is moved to be covered into struct ice_adapter, there is just one instance
>> of such per HW.
>> 
>> This patch adds a devlink instance that corresponds to that ice_adapter,
>> to allow arbitrage over resources (as RSS LUT) via it (further in the
>> series (RFC NOTE: stripped out so far)).
>> 
>> Thanks to Wojciech Drewek for very nice naming of the devlink instance:
>> PF0:		pci/0000:00:18.0
>> whole-dev:	pci/0000:00:18
>> But I made this a param for now (driver is free to pass just "whole-dev").
>
>Which only works nicely if you're talking about functions not full
>separate links :) When I was thinking about it a while back my
>intuition was that we should have a single instance, just accessible
>under multiple names. But I'm not married to that direction if there
>are problems with it.

I kind of agree. Like multiple channels to one entity, each labeled by a
different name (handle in devlink case).

>
>> $ devlink dev # (Interesting part of output only)
>> pci/0000:af:00:
>>   nested_devlink:
>>     pci/0000:af:00.0
>>     pci/0000:af:00.1
>>     pci/0000:af:00.2
>>     pci/0000:af:00.3
>>     pci/0000:af:00.4
>>     pci/0000:af:00.5
>>     pci/0000:af:00.6
>>     pci/0000:af:00.7
>
>Could you go into more details on what stays on the "nested" instances
>and what moves to the "whole-dev"? Jiri recently pointed out to y'all
>cases where stuff that should be a port attribute was an instance
>attribute.