Windows QXL Display Driver

Windows QXL Display Driver

[Geoffrey McRae]

Hi Gerd,

Over the past few weeks I have been adding spice display support to 
Looking Glass as a fallback mechanism for during system boot (or diags) 
before our application is loaded in the guest VM. The idea is to have 
the VFIO GPU duplicate it's output to the QXL device, which works fine 
until you load the QXL display driver.

The issue is that once the driver is loaded windows removes the option 
to duplicate the output. Is this something that needs to be tweaked in 
the driver to allow this? or is there a technical reason why this can't 
be done?

Kind Regards,
Geoffrey McRae

Re: Windows QXL Display Driver

[Gerd Hoffmann]

On Tue, May 24, 2022 at 12:35:49AM +1000, Geoffrey McRae wrote:
> Hi Gerd,
> 
> Over the past few weeks I have been adding spice display support to Looking
> Glass as a fallback mechanism for during system boot (or diags) before our
> application is loaded in the guest VM. The idea is to have the VFIO GPU
> duplicate it's output to the QXL device, which works fine until you load the
> QXL display driver.
> 
> The issue is that once the driver is loaded windows removes the option to
> duplicate the output.

Just don't load the driver then?  Or use stdvga instead?  Shouldn't make
a big difference performance-wise given that qxl supports 2d accel only
which is pretty much dead these days.

> Is this something that needs to be tweaked in the
> driver to allow this? or is there a technical reason why this can't be done?

I don't have much insight into the inner workings of the qxl windows
driver, sorry.

take care,
  Gerd

Re: Windows QXL Display Driver

[Geoffrey McRae]

On 2022-05-24 01:28, Gerd Hoffmann wrote:
> On Tue, May 24, 2022 at 12:35:49AM +1000, Geoffrey McRae wrote:
>> Hi Gerd,
>> 
>> Over the past few weeks I have been adding spice display support to 
>> Looking
>> Glass as a fallback mechanism for during system boot (or diags) before 
>> our
>> application is loaded in the guest VM. The idea is to have the VFIO 
>> GPU
>> duplicate it's output to the QXL device, which works fine until you 
>> load the
>> QXL display driver.
>> 
>> The issue is that once the driver is loaded windows removes the option 
>> to
>> duplicate the output.
> 
> Just don't load the driver then?  Or use stdvga instead?  Shouldn't 
> make
> a big difference performance-wise given that qxl supports 2d accel only
> which is pretty much dead these days.

This is what we will advise people but if possible we would like to 
avoid doing so as we know we are going to get people insisting on 
installing the driver anyway. We are basically trying to make this work 
in a way that we don't have to deal with a lot of support issues.

> 
>> Is this something that needs to be tweaked in the
>> driver to allow this? or is there a technical reason why this can't be 
>> done?
> 
> I don't have much insight into the inner workings of the qxl windows
> driver, sorry.

No worries, thanks for your time.

> 
> take care,
>   Gerd