linux-kernel - Re: [PATCH 9/9] vfio/pci: export igd support into vendor vfio

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Message-ID: <8dbe2c19-10f8-16e3-56ec-8026de84acc5@nvidia.com>
Date:   Thu, 11 Mar 2021 14:09:25 +0200
From:   Max Gurtovoy <mgurtovoy@...dia.com>
To:     Christoph Hellwig <hch@....de>, Jason Gunthorpe <jgg@...dia.com>
CC:     <alex.williamson@...hat.com>, <cohuck@...hat.com>,
        <kvm@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <liranl@...dia.com>, <oren@...dia.com>, <tzahio@...dia.com>,
        <leonro@...dia.com>, <yarong@...dia.com>, <aviadye@...dia.com>,
        <shahafs@...dia.com>, <artemp@...dia.com>, <kwankhede@...dia.com>,
        <ACurrid@...dia.com>, <cjia@...dia.com>, <yishaih@...dia.com>,
        <mjrosato@...ux.ibm.com>, <aik@...abs.ru>
Subject: Re: [PATCH 9/9] vfio/pci: export igd support into vendor vfio_pci
 driver

On 3/11/2021 1:37 PM, Christoph Hellwig wrote:
> On Wed, Mar 10, 2021 at 08:31:27AM -0400, Jason Gunthorpe wrote:
>> Yes, that needs more refactoring. I'm viewing this series as a
>> "statement of intent" and once we commit to doing this we can go
>> through the bigger effort to split up vfio_pci_core and tidy its API.
>>
>> Obviously this is a big project, given the past comments I don't want
>> to send more effort here until we see a community consensus emerge
>> that this is what we want to do. If we build a sub-driver instead the
>> work is all in the trash bin.
> So my viewpoint here is that this work doesn't seem very useful for
> the existing subdrivers given how much compat pain there is.  It
> defintively is the right way to go for a new driver.

This bring us back to the first series that introduced mlx5_vfio_pci 
driver without the igd, nvlink2 drivers.

if we leave the subdrivers/extensions in vfio_pci_core it won't be 
logically right.

If we put it in vfio_pci we'll need to maintain it and extend it if new 
functionality or bugs will be reported.

if we create a new drivers for these devices, we'll use the compat layer 
and hopefully after few years these users will be using only 
my_driver_vfio_pci and we'll be able to remove the compat layer (that is 
not so big).

We tried almost all the options and now we need to progress and agree on 
the design.

Effort is big and I wish we won't continue with experiments without a 
clear view of what exactly should be done.

So we need a plan how Jason's series and my series can live together and 
how can we start merging it gradually.