SharedGL

SharedGL is an OpenGL implementation built for streaming OpenGL commands over shared memory and networks, allowing for accelerated graphics within QEMU/KVM guests and across devices over LAN. The project is designed to be compatible with Windows and Linux, allowing for 3D acceleration without the need for GPU passthrough or a GPU present. For future plans, click here for the roadmap.

Click to reveal: Table of contents

1. Getting started
2. Usage
   • Environment variables
   • Shared memory or network
   • Linux
     • Linux in a VM
   • Windows in a VM
3. Networking
4. Virtual machines
5. Supported GL versions
6. Limitations / Issues
7. Troubleshooting
8. Showcase

Getting started

The following libraries are required for building the server and client on linux:

• libepoxy
• SDL2
• libx11

The following script builds: sglrenderer and libGL for Linux:

git clone https://github.com/dmaivel/sharedgl.git
cd sharedgl
mkdir build
cd build
cmake ..
cmake --build . --config Release

If on Windows (Visual Studio required), you must specify that you only want to build the library, sharedglXX.dll:

cmake --build . --target sharedgl-core --config Release

For additional build instructions for Windows, visit the Windows section.

Usage

The server must be started on the host before running any clients. Note that the server can only be ran on Linux.

usage: sglrenderer [-h] [-v] [-o] [-n] [-x] [-g MAJOR.MINOR] [-r WIDTHxHEIGHT] [-m SIZE] [-p PORT]
    
options:
    -h                 display help information
    -v                 display virtual machine arguments
    -o                 enables fps overlay on clients (shows server side fps)
    -n                 enable networking instead of shared memory
    -x                 remove shared memory file
    -g [MAJOR.MINOR]   report specific opengl version (default: 2.1)
    -r [WIDTHxHEIGHT]  set max resolution (default: 1920x1080)
    -m [SIZE]          max amount of megabytes program may allocate (default: 16mib)
    -p [PORT]          if networking is enabled, specify which port to use (default: 3000)

Environment variables

When running clients, a user may specify one or more of the following environment variables for version control:

GL_VERSION_OVERRIDE=X.X
GLX_VERSION_OVERRIDE=X.X
GLSL_VERSION_OVERRIDE=X.X

If networking on the server is enabled (using -n), the client must be aware of the address and port (both of which are outputted by the server):

SGL_NET_OVER_SHARED=HOST_ADDRESS:PORT

Shared memory or network

Starting from 0.5.0, SharedGL offers two methods of communication between a client and the host:

	Shared memory	Network
Requires additional drivers	:white_check_mark:	:x:
Requires additional host renderer arguments	:x:	:white_check_mark:
Requires additional environment variables for client	:x:	:white_check_mark:
Able to run/debug clients on host	:white_check_mark:	:white_check_mark:
Able to run clients in VMs	:white_check_mark:	:white_check_mark:
Able to run clients over LAN	:x:	:white_check_mark:

Linux

For your OpenGL application to communicate with the server, the client library must be specified in your library path. Upon exporting, any program you run in the terminal where you inputted this command will run with the SGL binary.

$ export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:/path/to/sharedgl/build
$ glxgears
$ ...

[!NOTE]
The client library for linux is not exclusive to virtual machines, meaning you can run it on your host for debugging.

Linux in a VM

Click here for virtual machine configuring, which is required for the guest to see SharedGL's shared memory

For virtual linux clients, an additional kernel module needs to be compiled (preferably in the vm). The compiled result, sharedgl.ko, needs to be loaded. There is a script within this directory (install.sh) for ease of use. It is recommended that you add sharedgl to your modprobe config following installation, otherwise it must be loaded manually on each boot.

# within 'sharedgl' directory
cd kernel/linux
make

[!WARNING]
If you move the client library to the guest from the host instead of compiling it in the guest, you may encounter the SIGILL exception in the virtual machine as the build compiles with the native (host) architecture. To fix, either change your cpu model to host-model/host-passthrough or comment out the -march=native line in the cmake script (will most likely reduce performance).

Windows (in a VM)

Windows is only supported as a guest: Click here for virtual machine configuring, which is required for the guest to see SharedGL's shared memory

Two things must be done for the windows installation:

1. Install a compatible driver
2. Install the clients

Kernel driver

There are two possible drivers one may use:

1. VirtIO's IVSHMEM driver (no multiclient support)
   1. Download and extract the upstream virtio win drivers, found here.
   2. Navigate into ...\virtio-win-upstream\Win10\amd64\.
   3. Right click on ivshmem.inf and press Install.

[!WARNING]
If you use the included driver, test signing must be on. Enable it by running the following command in an elevated command prompt: bcdedit.exe -set testsigning on and restart.

2. Included driver (multiclient support)
   1. Use the release (>= 0.4.0) (Windows 10 only)
      1. Download the latest release for windows and extract the zip file.
      2. Navigate into the extracted folder.
      3. Right click on ksgldrv.inf and press Install.
   2. Compile from source (use Visual Studio Developer Command Prompt)
      1. Ensure you have installed the WDK, which can be found here.

      2. :: git clone https://github.com/dmaivel/sharedgl.git
         :: cd sharedgl
         mkdir build
         cd build
         cmake -DCMAKE_GENERATOR_PLATFORM=x64 ..
         cmake --build . --target ksgldrv --config Release
         cd ..
         xcopy .\scripts\kcertify.bat .\build\Release\kcertify.bat
         xcopy .\scripts\ksgldrv.inf .\build\Release\ksgldrv.inf
         cd build\Release
         call kcertify.bat 10_X64
         
         :: requires admin privs, you may right click on the file and press install instead
         pnputil -i -a ksgldrv.inf
         

      3. By default, this builds for Windows 10 x64 (10_X64). If you wish to compile for a different version or multiple versions, you must provide it through the command line like so: kcertify.bat 10_X64,10_NI_X64. A list of OS versions is provided on MSDN here.

Library / ICD

There are two ways to install the library on windows:

1. Use a release (>= 0.3.1)
   1. Download the latest release for windows and extract the zip file.
   2. Navigate into the extracted folder and run wininstall.bat and allow admin privledges.
   3. The libraries should now be installed, meaning any application that uses OpenGL (32-bit and 64-bit) will use SharedGL.
2. Compile from source (use Visual Studio Developer Command Prompt)

   1. :: git clone https://github.com/dmaivel/sharedgl.git
      :: cd sharedgl
      mkdir build
      cd build
      cmake -DCMAKE_GENERATOR_PLATFORM=x64 ..
      cmake --build . --target sharedgl-core --config Release
      cmake -DCMAKE_GENERATOR_PLATFORM=Win32 ..
      cmake --build . --target sharedgl-core --config Release
      cd ..
      xcopy .\scripts\wininstall.bat .\build\Release\wininstall.bat
      cd build\Release
      call wininstall.bat
      

Networking

[!WARNING]
The network protocol is currently in active early development and is prone to bugs.

Starting from 0.5.0, SharedGL offers a networking feature that may be used in place of shared memory. No additional drivers are required for the network feature, meaning if you wish to have a driverless experience in your virtual machine, networking is the given alternative. The user still needs to install the ICD for either Linux or Windows (depending on the guest), however the kernel drivers/module do not need be compiled/installed. All the user needs to do is:

• Start the server using -n (and provide a port if the default is not available through -p PORT)
• Ensure the client libraries are installed
• Ensure that the environment variable SGL_NET_OVER_SHARED=ADDRESS:PORT exists (ADDRESS being the host's IP address)

Virtual machines

[!IMPORTANT]
This step is not required if you intend on only using SharedGL's network capabilities instead of the shared memory device. This means you do not need to compile the OS-specific kernel drivers or pass a shared memory device.

Before you start up your virtual machine, you must pass a shared memory device and start the server before starting the virtual machine. This can be done within libvirt's XML editor or the command line. Use the -v command line argument when starting the server and place the output in its respective location, depending on whether you use libvirt or qemu.

libvirt:

<!--> THIS IS A SAMPLE; ONLY USE THIS AS A GUIDE ON WHERE TO PLACE THE OUTPUT <-->
...
<devices>
    ...
    <shmem name="sharedgl_shared_memory">
        <model type="ivshmem-plain"/>
        <size unit="M">??</size>
    </shmem>
</devices>

qemu:

# THIS IS A SAMPLE; ONLY USE THIS AS A GUIDE ON WHERE TO PLACE THE OUTPUT
qemu-system-x86_64 -object memory-backend-file,size=??M,share,mem-path=/dev/shm/sharedgl_shared_memory,id=sharedgl_shared_memory

Supported GL versions

This list describes the amount of functions left from each standard to implement. This excludes EXT/ARB functions. This list may be inaccurate in terms of totals and also counts stubs as implementations.

• OpenGL 1
  • 1.0 (~306 total)
  • 1.1 (~30 total)
  • 1.2 (~4 total)
  • 1.3 (~46 total)
  • 1.4 (~47 total)
  • 1.5 (~19 total)
• OpenGL 2
  • 2.0 (~93 total)
  • 2.1 (~6 total)
• OpenGL 3
  • 3.0 (~23 remaining) (~84 total)
  • 3.1 (~7 remaining) (~15 total)
  • 3.2 (~14 remaining) (~19 total)
  • 3.3 (~29 remaining) (~58 total)
• OpenGL 4
  • 4.0 (~24 remaining) (~46 total)
  • 4.1 (~36 remaining) (~89 total)
  • 4.2 (~4 remaining) (~12 total)
  • 4.3 (~24 remaining) (~44 total)
  • 4.4 (~8 remaining) (~9 total)
  • 4.5 (~51 remaining) (~122 total)
  • 4.6 (~4 total)

Limitations / Issues

• Running several clients at once results in buggy frames
• Clients will allocate the same amount of memory as the server's command buffer for their internal buffer
• Vsync hasnt been implemented
• Resizing is not handled
• Inaccurate FPS in overlay (to-do: move timings from server to client)
• GLFW cant request OpenGL profiles
• Networking causes lock-ups (within server and client)

Troubleshooting

You may encounter weird crashes/faults/errors such as IOT instruction or No provider of glXXX found.. Although the code base is buggy, these are some tips to try to further attempts to get an application to work:

• Change the GL version (i.e -g 2.0)
• Allocate more memory (i.e -m 256)

---

Application shows a blank window in the virtual machine?

• Make sure the shared memory device passes through all the memory (check the size)

---

Application doesn't run in the virtual machine? (Process exists but stalls)

• Make sure the server is running
  • If you start the server and it still won't run, shut down the VM, run sudo ./sglrenderer -x, start the server, start the VM
• Make sure the drivers are installed (VirtIO IVSHMEM for Windows, custom kernel must be compiled for linux)

---

Server reports, err: failed to open shared memory 'sharedgl_shared_memory'

• This (usually) happens when the shared memory file is created before the server runs, meaning the file was created with different privileges. You may either:
  • Run the server as sudo
  • Shutdown the VM, run sudo ./sglrenderer -x, start the server, then start the VM

---

Client outputs, glimpl_init: failed to find memory to the terminal

• This occurs in VMs when you do not pass a shared memory device, which is required for the clients to see the shared memory

Showcase

Click to reveal: Running minetest in a windows virtual machine

https://github.com/dmaivel/sharedgl/assets/38770072/26c6216d-72f7-45b4-9c4f-1734de0d1c6d

Click to reveal: Running glxgears in a windows virtual machine (outdated)

https://github.com/dmaivel/sharedgl/assets/38770072/a774db97-807e-46b9-a453-fa2ee3f4ea84

Click to reveal: Running glxgears in a linux virtual machine (outdated)

https://github.com/dmaivel/sharedgl/assets/38770072/0d46bf46-5693-4842-a81f-2f186c396e26

Click to reveal: Running a compute shader in a linux virtual machine (outdated)

https://github.com/dmaivel/sharedgl/assets/38770072/ded179b8-23dc-491d-ba34-4108e014f296