By Martin Gräßlin - 14. October 2012 (Martin’s Blog From the land of wobbly windows)A journey through virtualization
(re OpenGL / VirtualBox / VMware)
This weekend I had a look on enabling the OpenGL compositor when running in a virtual machine. My assumption was that given that the next version of another distro is going to require OpenGL, there should be no problem with getting OpenGL running in a virtual machine.
I normally use KVM when I have need for a virtual machine running a Linux guest. As far as I know you cannot get OpenGL with this technology, so I hadn’t looked into it for quite some time.
My first attempt was to just use the project neon weekly build. Unfortunately I failed to convert it to a VirtualBox image, nevertheless I decided to run it and verify that KVM does not support OpenGL. Well I was rather surprised once the machine was up to see that OpenGL was functional, but well it was slow. Restarting KWin showed me that there is a missing slot (which I am aware of and is already fixed in one of the pending reviews) in master which makes the fallback to XRender not work, but KWin just uses llvmpipe. OK, result incorrect, but at least validated that KVM is not working.
I then decided to try VirtualBox with an install of Kubuntu Natty. Install went well but no OpenGL available. The Xorg log file told me that VirtualBox does not know the XServer version. Installed the latest version of VirtualBox, installed the latest version of guest additions in the Kubuntu guest, but no success: driver does not work.
So I decided to test with an outdated system, aka Debian Testing as I’m also running this on my workstation. Here I was more successful. After installing the system in the virtual machine OpenGL worked out-of-the-box. And what surprised me even more was that OpenGL in KWin worked when using KWIN_DIRECT_GL=1 and KWIN_COMPOSE=O. This means OpenGL works in general and it’s only blocked by KWin not knowing the driver.
The main reason is that KWin does not use direct rendering if it finds an unknown driver and VirtualBox only provides OpenGL in direct rendering mode. If LIBGL_ALWAYS_INDIRECT
is set, it falls back to Mesa’s software rasterization and KWin sets this environment variable if it doesn’t know the driver.
With VirtualBox working I decided to also look into VMware.......................Full Blog