Re: [QEMU PATCH v4 12/13] virtio-gpu: Initialize Venus

[Dmitry Osipenko <dmitry.osipenko@xxxxxxxxxxxxx>]

On 8/31/23 13:40, Antonio Caggiano wrote:
> Hi Huang,
> 
> Thank you for pushing this forward!
> 
> On 31/08/2023 11:32, Huang Rui wrote:
>> From: Antonio Caggiano <antonio.caggiano@xxxxxxxxxxxxx>
>>
>> Request Venus when initializing VirGL.
>>
>> Signed-off-by: Antonio Caggiano <antonio.caggiano@xxxxxxxxxxxxx>
>> Signed-off-by: Huang Rui <ray.huang@xxxxxxx>
>> ---
>>
>> v1->v2:
>>      - Rebase to latest version
>>
>>   hw/display/virtio-gpu-virgl.c | 2 ++
>>   1 file changed, 2 insertions(+)
>>
>> diff --git a/hw/display/virtio-gpu-virgl.c
>> b/hw/display/virtio-gpu-virgl.c
>> index 83cd8c8fd0..c5a62665bd 100644
>> --- a/hw/display/virtio-gpu-virgl.c
>> +++ b/hw/display/virtio-gpu-virgl.c
>> @@ -887,6 +887,8 @@ int virtio_gpu_virgl_init(VirtIOGPU *g)
>>       }
>>   #endif
>>   +    flags |= VIRGL_RENDERER_VENUS;
>> +
> 
> VIRGL_RENDERER_VENUS is a symbol only available from virglrenderer 0.9.1
> [0] and only if VIRGL_RENDERER_UNSTABLE_APIS is defined.
> 
> Luckily for us, VIRGL_RENDERER_UNSTABLE_APIS is defined unconditionally
> from virglrenderer 0.9.0 [1], so we could check for that in
> qemu/meson.build
> 
> e.g.
> 
> 
>   if virgl.version().version_compare('>= 0.9.0')
>     message('Enabling virglrenderer unstable APIs')
>     virgl = declare_dependency(compile_args:
> '-DVIRGL_RENDERER_UNSTABLE_APIS',
>                                dependencies: virgl)
>   endif
> 
> 
> Also, while testing this with various versions of virglrenderer, I
> realized there are no guarantees for Venus backend to be available in
> the linked library. Virglrenderer should be built with
> -Dvenus_experimental=true, and if that is not the case, the following
> virgl_renderer_init would fail for previous versions of virglrenderer or
> in case it has not been built with venus support.
> 
> I would suggest another approach for that which tries initializing Venus
> only if VIRGL_RENDERER_VENUS is actually defined. Then, if it fails
> cause virglrenderer has not been built with venus support, try again
> falling back to virgl only.

All the APIs will be stabilized with the upcoming virglrender 1.0
release that will happen soon. There is also a venus protocol bump, qemu
will have to bump virglrenderer's version dependency to 1.0 for venus
and other new features.

-- 
Best regards,
Dmitry