[virglrenderer-devel] Some question about running a GLES backend for virgl

[Jakob Bornecrantz]

On 2018-03-22 18:01, Lepton Wu wrote:
> On Thu, Mar 22, 2018 at 10:35 AM, Jakob Bornecrantz <jakob at collabora.com> wrote:
>> On 2018-03-22 03:37, Lepton Wu wrote:
>>>
>>> On Wed, Mar 21, 2018 at 7:23 PM, Jakob Bornecrantz <jakob at collabora.com>
>>> wrote:
>>>>
>>>> On 2018-03-22 01:38, Lepton Wu wrote:
>>>>>
>>>>>
>>>>> Hi Jakob,
>>>>>
>>>>> I have seen you sent some CL to run virglrenderer with GLES backend.
>>>>> I am also interested in this and tried it and it doesn't work well for
>>>>> me. I have some questions:
>>>>>
>>>>> 1.  The current virgl code is using some functions which is not
>>>>> available in GLES, for example, it's using glFramebufferTexture2DEXT
>>>>> and glBindBufferARB,  I can't find them in header files from GLES,
>>>>> then how it works with GLES backend?
>>>>
>>>>
>>>>
>>>> Virgl is using libepoxy so it can use both GLES and desktop GL. We have
>>>> added several checks to not call functions that are not available.
>>>> Libepoxy
>>>> will sometimes map a EXT function to a ARB function or a core function.
>>>> If
>>>> you are building virglrender make sure you have master of libepoxy.
>>>>
>>>> It should all work as is, tho we have only tested on 3.2 and the many
>>>
>>> Thanks. How likely the current code will work on some old GLES backend
>>> like 3.0?
>>> Would there be lots of stuff missing or need to be fixed? Just want to
>>> have some rough
>>> idea before I put time on it.
>>
>>
>> I don't think anything major should be missing on the side of virglrenderer.
>> If it does libepoxy is very good at informing you which function is missing,
>> so you can work around it. All of the shaders we generate in GLES are 3.0
>> shaders so those should already be good.
> Thanks, actually I took a quick test with ES3.0 backend of mesa 17.3.3
> and it works fine.
> It also works with ES3.2 backend of nvidia (although I have to add a
> small patch for it)

Thanks for testing and the patch, great that its working on a different 
driver/hardware then ours.

Cheers, Jakob.

>>
>> In the guest we currently only expose Desktop GL 2.1 and GLES 2.0 when
>> running on the GLES backend.
>>
>>
>>>> extensions that a Mesa driver gives. So there can be functions missing
>>>> from
>>>> angle.
>>>>
>>>>>
>>>>> 2. Any rough estimation for how long would it take for virgl work with
>>>>> a pure GLES backend?  basically I'd like to run virglrenderer on
>>>>> windows host and it seems it's easy to get GLES on windows with angle.
>>>>> So if virglrenderer can work with GLES backend, than perhaps it's not
>>>>> far away to get qemu+virgl works under windows.
>>>>
>>>>
>>>> We have it running now on Linux Mesa intel GLES 3.2 drier, if you are
>>>> using
>>>> the master branch of virgl.
>>>>
>>>> What is not upstreamed right now is getting QEMU to give you a GLES
>>>> context.
>>>> Search and replace SDL_GL_CONTEXT_PROFILE_CORE with
>>>> SDL_GL_CONTEXT_PROFILE_ES in ui/sdl2-gl.c in the QEMU source.
>>>>
>>>> It should just work on Windows if you give virgl a GLES context, modulo
>>>> different functions being available.
>>
>>
>> Cheers, Jakob.
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