RfC: vfio: add vgpu edid support?

[Zhenyu Wang]

On 2018.09.10 12:43:04 +0200, Gerd Hoffmann wrote:
>   Hi,
> 
> > > Ideally qemu would also be able to update the edid blob at any time, and
> > > the vgpu will notify the guest about it (probably by emulating a monitor
> > > hotplug event).  The guest can react on qemu window resizing then and
> > > adapt automatically, simliar to how it works with qxl and virtio-gpu.
> > 
> > What's the frequency for those edid update during resizing? Looks it's
> > possible to bring hotplug storm that I'm not sure if all guest drivers
> > for gvt has proper handling.
> 
> At most once per second.
> 
> The window resize typically creates a flood of the these events.  qemu
> doesn't forward them to the guest as-is, but instead sets up a timer,
> firing one second later.  The next event coming in just rearms the
> timer.  When the timer goes off the guest is actually notified.
>

Then that should be fine. Current intel display driver has 5 hotplug
irq threshold within one second.

> > > The guest and the vgpu should be able to handle "odd" non-standard
> > > display resolutions like this (coming from random window resizing):
> > > 
> > >    Detailed mode: Clock 106.620 MHz, 477 mm x 330 mm
> > >                   1212 1515 1551 1636 hborder 0
> > >                    840  844  848  869 vborder 0
> > >                   -hsync -vsync 
> > >                   VertFreq: 74 Hz, HorFreq: 65171 Hz
> > >
> > 
> > Some odd timing might not be supported, e.g can't get a sane PLL setting
> > calculation for clock required. As gvt exposes a virtual display pipeline
> > following hw definition, so guest driver still depend on sane output, I
> > think that may just go wrong with arbitrary mode..
> 
> I've suspected that might become an issue.
> What kind of restrictions exist for the clock?
>

I need to double check this with our display developer on current supported HW.

> > > +struct vfio_device_gfx_edid_set {
> > > +	__u32 argsz;
> > > +	__u32 flags;
> > > +	/* in */
> > > +	__u8  edid[256];
> > > +};
> > > +
> > 
> > I assume you have defined return value for the set too right? In case
> > for driver can't handle or invalid edid blob, etc.
> 
> Just return -EINVAL then, as usual (but I can update the comment
> explicitly saying so).
> 

thanks

-- 
Open Source Technology Center, Intel ltd.

$gpg --keyserver wwwkeys.pgp.net --recv-keys 4D781827
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 195 bytes
Desc: not available
URL: <https://lists.freedesktop.org/archives/intel-gvt-dev/attachments/20180911/8abd2256/attachment.sig>