[gentoo-user] Running gentoo ~amd64 as a virtualbox guest

[walt]

I have a persistent problem (described below) with my ~amd64 guest
machine and I can't figure it out.

I run all the major linux distros as virtualbox guests so I can keep
track of what's happening on planet non-gentoo, but only the ~amd64
gentoo guest machine is having this problem:

When I start an X session in the gentoo guest machine, the 3D video
acceleration is emulated with the "Software Rasterizer" function of
mesa, as shown below:

# glxinfo | grep renderer
OpenGL renderer string: Software Rasterizer

The problem is that "Software Rasterizer" is so slow and inefficient
that the gnome3 shell specifically tests for it and refuses to start
if it's found.

Other guest linux distros report the "Chromium" rasterizer or maybe
the "llvmpipe" rasterizer, both of which are fast enough to satisfy
the gnome3 shell.

So, could the problem be caused by the vbox package on my gentoo host
machines?  I don't know, but I can propose a test:

I know some of you have access to (real) machines that run non-gentoo
distros (I'm too lazy to install a non-gentoo distro on my real boxes
just to debug this silly problem) and so I thought maybe you could try
the same test and report back your results :)

Thanks!