This is really no problem now that Intel chips ship with RDRAND instructions. Linux should follow BSD/Mac's footsteps and incorporate a good CSPRNG non-blocking devices (after seed). I believe BSD is moving towards Fortuna, which is perfect for this use-case.

With these instructions you'll always get a "good"[1] seed for your CSPRNG, and that includes virtual machines and clones.

[1] Of course that depends on how much you trust Intel. Don't ask the crypto mailing lists whether this is a good idea :-)