Hello.
Windows 10 Host.
Both 32 and 64 bit architecture doesn't make difference.
This problem happen with ANY Linux guest. I try with Fedora 21/23 and 24, Archlinux, Gentoo, Mint. I'm sure it happen with other Linux guests too.
After installing and configuring Virtualbox Guest Additions (in this case later version 5.1.4) I boot the Linux guest and when the system load Plasma 5 desktop, KDE windows manager kwin-x11 suddenly crash. You can't even switch to a terminal to kill it, becouse all the other terminal show a dead picture of Plasma desktop, so you can't even operate terminals in other instances. Just pushing the virtual poweroff button allow to cleanly shutdown the virtual linux guest machine,
You blacklist vboxvideo.ko module and you can use Plasma 5 desktop and kwin-x11 do not crash. In this case accelleration is software and it is provided by Gallium on lvmpipe.
I googled this problem and I found some reply were it was suggested to just disable Composite/effect component in Plasma 5/kwin-x11 then it wasn't enough on any of my Linux guest.
Now, it is pretty much clear vboxvideo.ko and kwin-x11 doesn't get along for any good, so what should I do to run Plasma 5 desktop under hardware accelleration provided by vboxvideo.ko avoiding the kwin-x11 crash waiting someone will fix this annoying bug?