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From: Daniel Vetter <daniel@ffwll.ch>
To: Christoph Hellwig <hch@lst.de>
Cc: Jason Gunthorpe <jgg@nvidia.com>,
	"dri-devel@lists.freedesktop.org"
	<dri-devel@lists.freedesktop.org>,
	Greg KH <gregkh@linuxfoundation.org>,
	"intel-gfx@lists.freedesktop.org"
	<intel-gfx@lists.freedesktop.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Gerd Hoffmann <kraxel@redhat.com>,
	"intel-gvt-dev@lists.freedesktop.org" 
	<intel-gvt-dev@lists.freedesktop.org>
Subject: Re: [Intel-gfx] refactor the i915 GVT support
Date: Thu, 29 Jul 2021 09:30:19 +0200	[thread overview]
Message-ID: <YQJZCwyT9YSZWLnO@phenom.ffwll.local> (raw)
In-Reply-To: <20210729072022.GB31896@lst.de>

On Thu, Jul 29, 2021 at 09:20:22AM +0200, Christoph Hellwig wrote:
> On Wed, Jul 28, 2021 at 02:59:25PM -0300, Jason Gunthorpe wrote:
> > On Wed, Jul 28, 2021 at 01:38:58PM +0000, Wang, Zhi A wrote:
> > 
> > > I guess those APIs you were talking about are KVM-only. For other
> > > hypervisors, e.g. Xen, ARCN cannot use the APIs you mentioned. Not
> > > sure if you have already noticed that VFIO is KVM-only right now.
> > 
> > There is very little hard connection between VFIO and KVM, so no, I
> > don't think that is completely true.
> 
> The only connection is the SET_KVM notifier as far as I can tell.
> Which is used by a total of two drivers, including i915/gvt.  That
> being said gvt does not only use vfio, but also does quite a few
> direct cals to KVM.
> 
> > In an event, an in-tree version of other hypervisor support for GVT
> > needs to go through enabling VFIO support so that the existing API
> > multiplexers we have can be used properly, not adding a shim layer
> > trying to recreate VFIO inside a GPU driver.
> 
> Yes.  And if we go back to actually looking at the series a lot of
> it just removes entirely pointless indirect calls that go to generic
> code and not even the kvm code, or questionable data structure designs.
> If we were to support another upstream hypervisor we'd just need to
> union a few fields in struct intel_gpu and maybe introduce a few
> methods.  Preferably in a way that avoids expensive indirect calls
> in the fast path.

fwiw I concur with the direction of this series. gvt landed 5 years ago,
that should have been plenty of time to merge at least one of the other
backends that float around. If it didn't happen in 5 years it aint
suddenly happening in the next few, and the abstraction layer should be
sunset.

Also yes structuring it more as a helper layer with some
unions/subclassing than full blown backend abstractor layer would be a
good idea too I guess (it usually is the right thing to do).
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch

  reply	other threads:[~2021-07-29  7:30 UTC|newest]

Thread overview: 60+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-21 15:53 Christoph Hellwig
2021-07-21 15:53 ` [PATCH 01/21] drm/i915/gvt: integrate into the main Makefile Christoph Hellwig
2021-08-03  9:27   ` Zhenyu Wang
2021-07-21 15:53 ` [PATCH 02/21] drm/i915/gvt: remove module refcounting in intel_gvt_{,un}register_hypervisor Christoph Hellwig
2021-07-21 15:53 ` [PATCH 03/21] drm/i915/gvt: remove enum hypervisor_type Christoph Hellwig
2021-07-21 15:53 ` [PATCH 04/21] drm/i915/gvt: move the gvt code into kvmgt.ko Christoph Hellwig
2021-08-09 11:29   ` Joonas Lahtinen
2021-08-09 14:29     ` Christoph Hellwig
2021-07-21 15:53 ` [PATCH 05/21] drm/i915/gvt: remove intel_gvt_ops Christoph Hellwig
2021-07-21 15:53 ` [PATCH 06/21] drm/i915/gvt: remove the map_gfn_to_mfn and set_trap_area ops Christoph Hellwig
2021-07-21 15:53 ` [PATCH 07/21] drm/i915/gvt: remove the unused from_virt_to_mfn op Christoph Hellwig
2021-07-21 15:53 ` [PATCH 08/21] drm/i915/gvt: merge struct kvmgt_vdev into struct intel_vgpu Christoph Hellwig
2021-07-21 15:53 ` [PATCH 09/21] drm/i915/gvt: merge struct kvmgt_guest_info into strut intel_vgpu Christoph Hellwig
2021-07-21 15:53 ` [PATCH 10/21] drm/i915/gvt: remove vgpu->handle Christoph Hellwig
2021-07-21 15:53 ` [PATCH 11/21] drm/i915/gvt: devirtualize ->{read,write}_gpa Christoph Hellwig
2021-07-21 15:53 ` [PATCH 12/21] drm/i915/gvt: devirtualize ->{get,put}_vfio_device Christoph Hellwig
2021-07-21 15:53 ` [PATCH 13/21] drm/i915/gvt: devirtualize ->set_edid and ->set_opregion Christoph Hellwig
2021-07-21 15:53 ` [PATCH 14/21] drm/i915/gvt: devirtualize ->detach_vgpu Christoph Hellwig
2021-07-21 15:53 ` [PATCH 15/21] drm/i915/gvt: devirtualize ->inject_msi Christoph Hellwig
2021-07-21 15:53 ` [PATCH 16/21] drm/i915/gvt: devirtualize ->is_valid_gfn Christoph Hellwig
2021-07-21 15:53 ` [PATCH 17/21] drm/i915/gvt: devirtualize ->gfn_to_mfn Christoph Hellwig
2021-07-21 15:53 ` [PATCH 18/21] drm/i915/gvt: devirtualize ->{enable,disable}_page_track Christoph Hellwig
2021-07-21 15:53 ` [PATCH 19/21] drm/i915/gvt: devirtualize ->dma_{,un}map_guest_page Christoph Hellwig
2021-07-21 15:53 ` [PATCH 20/21] drm/i915/gvt: devirtualize dma_pin_guest_page Christoph Hellwig
2021-07-21 15:53 ` [PATCH 21/21] drm/i915/gvt: remove struct intel_gvt_mpt Christoph Hellwig
2021-07-22  9:45 ` refactor the i915 GVT support Zhenyu Wang
2021-07-22 12:55   ` Christoph Hellwig
2021-07-22 10:49 ` Wang, Zhi A
2021-07-22 11:26   ` Gerd Hoffmann
2021-07-27 12:12     ` Jason Gunthorpe
2021-07-28 13:38       ` Wang, Zhi A
2021-07-28 13:43         ` Greg KH
2021-07-28 17:59         ` Jason Gunthorpe
2021-07-29  7:20           ` Christoph Hellwig
2021-07-29  7:30             ` Daniel Vetter [this message]
2021-08-03  9:43             ` Zhenyu Wang
2021-08-03 14:30               ` Jason Gunthorpe
2021-08-04  5:26                 ` Zhenyu Wang
2021-08-16 17:34                   ` Christoph Hellwig
2021-08-17  1:08                     ` Zhenyu Wang
2021-08-17  5:22                       ` Zhenyu Wang
2021-08-19  8:29                         ` Zhenyu Wang
2021-08-19 14:43                           ` Joonas Lahtinen
2021-08-26  6:04                             ` Zhenyu Wang
2021-08-20 14:17                           ` Christoph Hellwig
2021-08-20 19:56                             ` Luis Chamberlain
2021-08-26  6:12                               ` Zhenyu Wang
2021-09-28  7:41                                 ` Wang, Zhi A
2021-09-28 14:00                                   ` Luis Chamberlain
2021-09-28 14:35                                     ` Wang, Zhi A
2021-09-28 15:05                                       ` Jason Gunthorpe
2021-09-29 18:27                                         ` Wang, Zhi A
2021-09-29 18:55                                           ` Jason Gunthorpe
2021-10-01 13:01                                             ` Wang, Zhi A
2021-10-05  7:33                                               ` Wang, Zhi A
2021-09-30  5:24                                           ` Christoph Hellwig
2021-08-26  6:08                             ` Zhenyu Wang
2021-08-04  5:40                 ` Christoph Hellwig
2021-07-29  8:19           ` Wang, Zhi A
2021-07-22 13:16   ` Greg KH

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