I installed Gentoo on a virtual machine and guest addition too.
I checked that it works. For example, I can drag and drop a file from the host to the virtual machine and back. I also have a shared clipboard. But the screen resolution has not changed. I would like to put at least 1920x1080, help me fix this problem ;-)
Here is xrandr output:
user@localhost ~ $ xrandr
xrandr: Failed to get size of gamma for output default
Screen 0: minimum 640 x 480, current 1024 x 768, maximum 1024 x 768
default connected 1024x768+0+0 0mm x 0mm
1024x768 0.00*
800x600 0.00
640x480 0.00
