Re: Possible regression with VGA and resolutions in Windows 10?

[Gerd Hoffmann]

On Fri, Jul 24, 2020 at 03:31:23PM +0100, Daniel P. Berrangé wrote:
> On Fri, Jul 24, 2020 at 04:10:32PM +0200, Gerd Hoffmann wrote:
> >   Hi,
> > 
> > > The behavior is similar when setting a custom resolution with the xres
> > > and yres parameters. Setting it the first time works fine and it is
> > > shown along with the short list. Setting it to something different on
> > > the next boot will not be recognized unless the display adapter is
> > > uninstalled and the VM rebooted.
> > 
> > Interesting.  Seems Windows caches the list of resolutions (or the edid
> > blob) somewhere in the registry instead of loading it on every boot.
> > I've seen simliar behavior with usb device info.
> > 
> > [ something for the 5.1 release notes I think, thanks for testing this ]
> 
> Do we need to be disabling edid in the old machine types to prevent this
> change in guest ABI due to the changed BIOS ?
> 
> eg existing VMs using a versioned machine type shouldn't suddenly get edid
> enabled where previously it was not present. Only VMs using the new 5.1 or
> unversioned machine types should see the change in behaviour.

Well, the *device* feature actually is versioned, but it is present in
qemu for quite a while already.  Now the *vgabios* update makes the edid
available via bios interface.  We have two independent changes, so it
isn't that simple ...

take care,
  Gerd