netdev - Re: [PATCH net-next 00/13] resource management using devlink reload

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Message-ID: <Y3ckRWtAtZU1BdXm@unreal>
Date:   Fri, 18 Nov 2022 08:20:53 +0200
From:   Leon Romanovsky <leon@...nel.org>
To:     Jakub Kicinski <kuba@...nel.org>
Cc:     Michal Swiatkowski <michal.swiatkowski@...ux.intel.com>,
        "Samudrala, Sridhar" <sridhar.samudrala@...el.com>,
        netdev@...r.kernel.org, davem@...emloft.net, pabeni@...hat.com,
        edumazet@...gle.com, intel-wired-lan@...ts.osuosl.org,
        jiri@...dia.com, anthony.l.nguyen@...el.com,
        alexandr.lobakin@...el.com, wojciech.drewek@...el.com,
        lukasz.czapnik@...el.com, shiraz.saleem@...el.com,
        jesse.brandeburg@...el.com, mustafa.ismail@...el.com,
        przemyslaw.kitszel@...el.com, piotr.raczynski@...el.com,
        jacob.e.keller@...el.com, david.m.ertman@...el.com,
        leszek.kaliszczuk@...el.com, Bjorn Helgaas <bhelgaas@...gle.com>
Subject: Re: [PATCH net-next 00/13] resource management using devlink reload

On Thu, Nov 17, 2022 at 07:36:18PM -0800, Jakub Kicinski wrote:
> On Thu, 17 Nov 2022 19:38:48 +0200 Leon Romanovsky wrote:
> > I don't think that management of PCI specific parameters in devlink is
> > right idea. PCI has his own subsystem with rules and assumptions, netdev
> > shouldn't mangle them.
> 
> Not netdev, devlink, which covers netdev, RDMA and others.

devlink is located in net/*, it is netdev.
Regarding RDMA, it is not fully accurate. We use devlink to convey
information to FW through pci device located in netdev. Some of such
parameters are RDMA related. However, we don't configure RDMA properties
through devlink, there is a special tool for that (rdmatool).

> 
> > In MSI-X case, this even more troublesome as users
> > sees these values through lspci without driver attached to it.
> 
> I'm no PCI expert either but FWIW to me the patch set seems reasonable.
> Whether management FW policies are configured via core PCI sysfs or
> subsystem-specific-ish APIs is a toss up. Adding Bjorn and please CC him
> on the next rev.

The thing is that it must be managed by FW. Earlier in this thread, I pointed
the pretty normal use case where you need to have valid PCI structure without
any driver involvement.

> 
> Link to the series:
> https://lore.kernel.org/all/20221114125755.13659-1-michal.swiatkowski@linux.intel.com/