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

[Lepton Wu]

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)
>
> 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.