No thanks to Sony support, of course. I have had several email conversations with them, but in the end they always said: 'look, we don't support this and therefore we do not know how to turn it on'. With that they conveniently forgot they were the ones to build the stupid and broken BIOS image in the first place...
Anyway, if you own an Vaio from the FW-series (or a few other types), you might want to read this thread on the forums of notebookreview.com. It fixed my problem!
I can *finally* run kvm on this things, which is the one thing I originally bought it for!
$ lsmod | grep kvm
kvm_intel 52944 1
kvm 137976 1 kvm_intel