netdev - Re: [PATCH 0/8] Introduce fwctl subystem

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Date: Thu, 6 Jun 2024 21:02:49 -0300
From: Jason Gunthorpe <jgg@...dia.com>
To: Dan Williams <dan.j.williams@...el.com>
Cc: Leon Romanovsky <leon@...nel.org>, Jakub Kicinski <kuba@...nel.org>,
	David Ahern <dsahern@...nel.org>, Jonathan Corbet <corbet@....net>,
	Itay Avraham <itayavr@...dia.com>, linux-doc@...r.kernel.org,
	linux-rdma@...r.kernel.org, netdev@...r.kernel.org,
	Paolo Abeni <pabeni@...hat.com>, Saeed Mahameed <saeedm@...dia.com>,
	Tariq Toukan <tariqt@...dia.com>,
	Andy Gospodarek <andrew.gospodarek@...adcom.com>,
	Aron Silverton <aron.silverton@...cle.com>,
	Christoph Hellwig <hch@...radead.org>, Jiri Pirko <jiri@...dia.com>,
	Leonid Bloch <lbloch@...dia.com>, linux-cxl@...r.kernel.org,
	patches@...ts.linux.dev
Subject: Re: [PATCH 0/8] Introduce fwctl subystem

On Thu, Jun 06, 2024 at 03:11:21PM -0700, Dan Williams wrote:
> Leon Romanovsky wrote:
> > On Wed, Jun 05, 2024 at 09:56:14PM -0700, Dan Williams wrote:
> > > Jason Gunthorpe wrote:
> > 
> > <...>
> > 
> > > So my questions to try to understand the specific sticking points more
> > > are:
> > > 
> > > 1/ Can you think of a Command Effect that the device could enumerate to
> > > address the specific shenanigan's that netdev is worried about? In other
> > > words if every command a device enables has the stated effect of
> > > "Configuration Change after Reset" does that cut out a significant
> > > portion of the concern? 
> > 
> > It will prevent SR-IOV devices (or more accurate their VFs)
> > to be configured through the fwctl, as they are destroyed in HW
> > during reboot.
> 
> Right, but between zero configurability and losing live SR-IOV
> configurabilitiy is there still value? Note, this is just a thought
> experiment on what if any Command Effects Linux can comfortably tolerate
> vs those that start to be more spicy and dip into removing stimulus /
> focus on the commons, or otherwise injuring collaboration.

I like the idea of "takes effect on _function_ reset". VFs and PFs
both often have configuration that can become current once the fuction
is reset. A VF is usually reset by something like VFIO while a PF is
usually reset by a power cycle.

The fact configuration doesn't change until reset is, IMHO, a very
strong barrier from making some backdoor into a subsystem driver.

Jason