[virglrenderer-devel] Guest chosen host context types

[Dave Airlie]

> So currently we have a couple of bugs and a fairly big pile of code related
> to various texture formats that are not supported by the core GL context but
> is needed to support GLES and compatibility GL. For instance alpha and
> luminescence.
>
> So my thought was that he guest could mark a context as a GLES context and
> the host would then create GLES context on the host and have those formats
> supported without any workarounds.
>
> Now I'm guessing there are several things that will go wrong with trying to
> mix GLES and D-GL (Desktop GL) in virgl. Sharing textures will need to be
> worked around. Format table and some have_foo needs to be per-context. Caps
> will probably be made per context type. And a whole bunch of other things
> might explode.
>
> That said a lot of these things will probably have to be solved if we ever
> want to do vulkan virgl. So maybe we can do a bunch of ground work and
> experiment with GLES vs D-GL without having to deal with Vulkan on top of
> all that.
>
> Initially just opening a Vulkan Device, allocating all resources from it and
> importing them into D-GL and GLES would enable sharing between the different
> profiles at least. And be something we could build Vulkan support on top of.
>
> Thoughts and comments, please?

I've no major objections, but it's going to be churny. I wonder do we need to
try and get GLES3.1 merged first, and maybe cut a release before taking
something like this on.

For vulkan we'd have to route at least all shared object allocs via vulkan
memory allocation, the question for GL vs GLES is what would context 0
need to be.

I'd really like to minimise these "fourth wall" breaches though, exposing
the host stack internals to the guest makes me weary exposing host
contexts made me annoyed but GL couldn't do certain things without them
(like transform feedback).

I expect I'd need to see the solution is better than the problem :-) I don't
even think in gallium we have the info to know if we want a GLES or GL
context at that level.

Dave.