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OpenGL streaming

This software provides an implementation of the EGL and GLES2 APIs, which forwards an application's (client-side) graphics calls to a remote (server-side) EGL/GLES2 implementation, which typically renders using a GPU. Any display operations are done by the server, on its own screen.

It is expected to get extended in the future to support more graphics APIs (eg. desktop OpenGL, GLX, Vulkan), as very few apps work with GLES2.

The motivation for this project is to provide GPU acceleration to virtual machines, with rendering on their host, especially to be usable on QubesOS to securely provide decent GPU acceleration to Qubes containers.

The GPU server should be able to run on most UNIX-like systems. The client library will be adapted to work on various plaforms suitable to be used in a Qube. Either way, today it is only tested on GNU/Linux platforms.

Current status

This is still a work in progress. See current software support status for detailed per-application compatibility information. While the core functionnality (support for forwarding GL calls) is there, the problem with window handling (described below) is critical enough to postpone work on security improvements. In short: consider this version as a PoC, test in controlled environment, and don't deploy it.

Notable information:

  • A number of APIs are still stubbed, and some are known to have bugs, the holes are plugged progressively to add support for more client apps. Very few extensions are already supported.

  • APIs for EGL 1.4 are present, though some 1.1 and 1.2 APIs are not even stubbed. Version 1.0 is advertised, even though it is not fully implemented yet.

  • Only EGL/X11 is properly supported for now

  • The client still creates a window on its own, which is used for interaction with the app (input events, window resize, etc). When running locally (ie. GPU server and app on the same display) it gets quite awkward, as both windows must share the same screen. However, resizing the local window will allow some apps to be used, at the cost of using a smaller window so they both fit into the screen, as long as the "input window" keeps the focus. This trick can be extended to apps that don't use the mouse at all.

    Both application classes can be easier to use remotely.

    However, applications making real use of the mouse and not drawing their own mouse cursor cannot realistically be used yet.

  • Application relying on SDL2 to get an OpenGL context need an additional trick, as the SDL2 library shipped in most Linux distributions will prefer the use of Desktop OpenGL. SDL2 ought to obey SDL_RENDER_DRIVER=opengles2 in the environment but apparently doesn't, so for now we have to build our own libsdl2 without desktop GL support.

  • Unfortunately very few 3D applications for the Desktop use GLES2. Please open a ticket if have one at hand.

  • There are security concerns, notably:

    • usage of pointer types in the protocol must be cured
    • when using the TCP transport (which mostly exists for testing purposes today), any app can connect to the server (somewhat mitigated by listening only on localhost by default, but you'd better trust other users of a system before launching gl_server on it)

  • Usage of pointer types in the protocol also implies that only 64bit builds can work now. We should not only be able to build 32bit versions too, but to have them interoperate.

  • A rather unsorted TODO list has a summary of things to be done, as well as those already done: it's important to see that despite the large amount of work to be done, things are really progressing.

  • Essentially tested both client and server sides on GNU/Linux.

  • Apps which do not control vsync using eglSwapInterval() (eg. es2gears), which need to set vblank_mode=0 to force disable vsync rendering, need to do so on the gl_server process.

How to use

See usage instructions, and especially a QubesOS test setup.

High-level roadmap

This is my own personal roadmap. Contributors welcome, to help with those items or add their own in the picture.

  • bring EGL/GLES2 support to a satisfying state
    • add extension support
    • solve structural security issues
      • use separate processes to isolate clients' contexts on server
      • remove pointers from protocol
    • implement a satisfying window/input experience
      • on-demand window, properly sized
      • no extra client-side window
    • bring to decent performance level
  • add Vulkan support

Performance and conformance information

Very few preliminary benchmarks were run.

Other sources of information

Reporting bugs

If you find a bug, wish to report success/failure with a given app, or submit any other relevant item, see the project issues on Github.

Thanks

This work builds on previous efforts:

Shodruky Rhyammer wrote the original PoC, client-side requiring patching apps to use streaming, and server-side rendering on a Raspberry Pi GPU. Cites meaningful help from OpenGL forum (notably from user The Little Body).

ArtDev implemented server-side rendering on Android devices (abandonning support for proprietary RPi-specific APIs), and started support for a rendering on a Linux-based server.

Mittorn implemented emulation of client arrays with VBO's (later apparently reused by Duy Tran Khanh forgetting to credit the author of original code).

Duy Tran Khanh greatly enhanced API covererage, turned the client side into a real EGL/GLES2 shared lib allowing existing apps to run unmodified.