[Intel-gfx] [PATCH v9 5/7] vfio: Define vfio based dma-buf operations
Alex Williamson
alex.williamson at redhat.com
Fri Jun 23 17:15:54 UTC 2017
On Fri, 23 Jun 2017 09:26:59 +0200
Gerd Hoffmann <kraxel at redhat.com> wrote:
> Hi,
>
> > Is this only going to support accelerated driver output, not basic
> > VGA
> > modes for BIOS interaction?
>
> Right now there is no vgabios or uefi support for the vgpu.
>
> But even with that in place there still is the problem that the display
> device initialization happens before the guest runs and therefore there
> isn't an plane yet ...
>
> > > Right now the experimental intel patches throw errors in case no
> > > plane
> > > exists (yet). Maybe we should have a "bool is_enabled" field in
> > > the
> > > plane_info struct, so drivers can use that to signal whenever the
> > > guest
> > > has programmed a valid video mode or not (likewise for the cursor,
> > > which doesn't exist with fbcon, only when running xorg). With that
> > > in
> > > place using the QUERY_PLANE ioctl also for probing looks
> > > reasonable.
> >
> > Sure, or -ENOTTY for ioctl not implemented vs -EINVAL for no
> > available
> > plane, but then that might not help the user know how a plane would
> > be
> > available if it were available.
>
> So maybe a "enum plane_state" (instead of "bool is_enabled")? So we
> can clearly disturgish ENABLED, DISABLED, NOT_SUPPORTED cases?
What's the difference between NOT_SUPPORTED and -ENOTTY on the ioctl?
Perhaps a bit in a flags field could specify EN/DIS-ABLED and leave
room for things we're forgetting. Keep in mind that we need to use
explicit width fields for a uapi structure, so __u32 vs enum. Thanks,
Alex
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