The citation is we're building a GPU cloud and have tested almost every GPU in existence :) Just kidding, here are a few examples:

http://vfio.blogspot.com.au/2014/08/vfiovga-faq.html https://www.reddit.com/r/linux/comments/2twq7q/nvidia_appare... https://www.redhat.com/archives/libvirt-users/2014-October/m...

I just quickly googled this so there are probably better sources. Some of these are old but I can tell you firsthand that this is still the case.

There are workarounds for certain hypervisors (KVM mainly) but it's very unlikely that this would be deployed in a production environment.