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From: Jason Gunthorpe <jgg@nvidia.com>
To: Christoph Hellwig <hch@infradead.org>
Cc: Alex Williamson <alex.williamson@redhat.com>,
	Max Gurtovoy <mgurtovoy@nvidia.com>,
	Cornelia Huck <cohuck@redhat.com>,
	Matthew Rosato <mjrosato@linux.ibm.com>, <kvm@vger.kernel.org>,
	<linux-kernel@vger.kernel.org>, <liranl@nvidia.com>,
	<oren@nvidia.com>, <tzahio@nvidia.com>, <leonro@nvidia.com>,
	<yarong@nvidia.com>, <aviadye@nvidia.com>, <shahafs@nvidia.com>,
	<artemp@nvidia.com>, <kwankhede@nvidia.com>, <ACurrid@nvidia.com>,
	<gmataev@nvidia.com>, <cjia@nvidia.com>, <yishaih@nvidia.com>,
	<aik@ozlabs.ru>
Subject: Re: [PATCH 8/9] vfio/pci: use x86 naming instead of igd
Date: Thu, 11 Feb 2021 10:30:44 -0400	[thread overview]
Message-ID: <20210211143044.GL4247@nvidia.com> (raw)
In-Reply-To: <20210211084703.GC2378134@infradead.org>

On Thu, Feb 11, 2021 at 08:47:03AM +0000, Christoph Hellwig wrote:
> On Wed, Feb 03, 2021 at 09:54:48AM -0400, Jason Gunthorpe wrote:
> > If people are accepting that these device-specific drivers are
> > required then we need to come to a community consensus to decide what
> > direction to pursue:
> > 
> > * Do we embrace the driver core and use it to load VFIO modules like a
> >   normal subsytem (this RFC)
> > 
> > OR 
> > 
> > * Do we make a driver-core like thing inside the VFIO bus drivers and
> >   have them run their own special driver matching, binding, and loading
> >   scheme. (May RFC)
> > 
> > Haven't heard a 3rd option yet..
> 
> The third option would be to use the driver core to bind the VFIO
> submodules.  Define a new bus for it, which also uses the normal PCI IDs
> for binding, and walk through those VFIO specific drivers when vfio_pci
> is bound to a device.  That would provide a pretty clean abstraction
> and could even keep the existing behavior of say bind to all VGA devices
> with an Intel vendor ID (even if I think that is a bad idea).

I think of this as some variant to the second option above.

Maximally using the driver core to make subdrivers still means the
VFIO side needs to reimplement all the existing matcher logic for PCI
(and it means we don't generalize, so future CXL/etc, will need more
VFIO special code)  It has to put this stuff on a new special bus and
somehow make names and match tables for it.

It also means we'd have to somehow fix vfio-pci to allow hot
plug/unplug of the subdriver. The driver core doesn't really run
synchronously for binding, so late binding would have to be
accommodated somehow. It feels like adding a lot of complexity for
very little gain to me.

Personally I dislike the subdriver direction of the May RFC quite a
bit, it has a lot of unfixable negatives for the admin side. The first
option does present some challenges for userspace but I belive we can
work through them.

Jason

  reply	other threads:[~2021-02-11 14:34 UTC|newest]

Thread overview: 57+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-02-01 16:28 [PATCH v2 0/9] Introduce vfio-pci-core subsystem Max Gurtovoy
2021-02-01 16:28 ` [PATCH 1/9] vfio-pci: rename vfio_pci.c to vfio_pci_core.c Max Gurtovoy
2021-02-01 16:28 ` [PATCH 2/9] vfio-pci: introduce vfio_pci_core subsystem driver Max Gurtovoy
2021-02-01 16:28 ` [PATCH 3/9] vfio-pci-core: export vfio_pci_register_dev_region function Max Gurtovoy
2021-02-01 16:28 ` [PATCH 4/9] mlx5-vfio-pci: add new vfio_pci driver for mlx5 devices Max Gurtovoy
2021-02-01 16:28 ` [PATCH 5/9] vfio-pci/zdev: remove unused vdev argument Max Gurtovoy
2021-02-01 17:27   ` Matthew Rosato
2021-02-02  7:57   ` Cornelia Huck
2021-02-02 17:21     ` Alex Williamson
2021-02-01 16:28 ` [PATCH 6/9] vfio-pci/zdev: fix possible segmentation fault issue Max Gurtovoy
2021-02-01 16:52   ` Cornelia Huck
2021-02-01 17:08     ` Matthew Rosato
2021-02-01 20:47       ` Alex Williamson
2021-02-02  7:58         ` Cornelia Huck
2021-02-01 16:28 ` [PATCH 7/9] vfio/pci: use s390 naming instead of zdev Max Gurtovoy
2021-02-01 16:28 ` [PATCH 8/9] vfio/pci: use x86 naming instead of igd Max Gurtovoy
2021-02-01 17:14   ` Cornelia Huck
2021-02-01 17:49     ` Matthew Rosato
2021-02-01 18:42       ` Alex Williamson
2021-02-02 16:06         ` Cornelia Huck
2021-02-02 17:10           ` Jason Gunthorpe
2021-02-11 15:47             ` Max Gurtovoy
2021-02-11 16:29               ` Matthew Rosato
2021-02-11 17:39                 ` Cornelia Huck
2021-02-02 17:41           ` Max Gurtovoy
2021-02-02 17:54             ` Alex Williamson
2021-02-02 18:50               ` Jason Gunthorpe
2021-02-02 18:55                 ` Christoph Hellwig
2021-02-02 19:05                   ` Jason Gunthorpe
2021-02-02 19:37                 ` Alex Williamson
2021-02-02 20:44                   ` Jason Gunthorpe
2021-02-02 20:59                     ` Max Gurtovoy
2021-02-02 21:30                       ` Alex Williamson
2021-02-02 23:06                         ` Jason Gunthorpe
2021-02-02 23:59                           ` Alex Williamson
2021-02-03 13:54                             ` Jason Gunthorpe
2021-02-11  8:47                               ` Christoph Hellwig
2021-02-11 14:30                                 ` Jason Gunthorpe [this message]
2021-02-11  8:44                             ` Christoph Hellwig
2021-02-11 19:43                               ` Alex Williamson
     [not found]             ` <806c138e-685c-0955-7c15-93cb1d4fe0d9@ozlabs.ru>
2021-02-03 16:07               ` Max Gurtovoy
     [not found]                 ` <83ef0164-6291-c3d1-0ce5-2c9d6c97469e@ozlabs.ru>
2021-02-04 12:51                   ` Jason Gunthorpe
2021-02-05  0:42                     ` Alexey Kardashevskiy
2021-02-08 12:44                       ` Max Gurtovoy
2021-02-09  1:55                         ` Alexey Kardashevskiy
2021-02-08 18:13                       ` Jason Gunthorpe
2021-02-09  1:51                         ` Alexey Kardashevskiy
2021-02-04  9:12               ` Max Gurtovoy
2021-02-11  8:50                 ` Christoph Hellwig
2021-02-11 14:49                   ` Jason Gunthorpe
2021-02-01 16:28 ` [PATCH 9/9] vfio/pci: use powernv naming instead of nvlink2 Max Gurtovoy
2021-02-01 18:35   ` Jason Gunthorpe
2021-02-10  7:52 ` [PATCH v2 0/9] Introduce vfio-pci-core subsystem Tian, Kevin
2021-02-10 13:34   ` Jason Gunthorpe
2021-02-10 16:37     ` Alex Williamson
2021-02-10 17:08       ` Jason Gunthorpe
2021-02-11  8:36     ` Christoph Hellwig

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