Yes there is, I ignore it on the desktop (which isn't good)[0] and run a script to reseed, but on the server/gateway I'd completely avoid freezing.

To make it worse, I never install the VM tools on any machine because i've always felt they are all crappy and insecure (and make VM detection easy). Most of the VM drivers try and fix this problem, but it would be best fixed with either virtualization hooks where commends are run in the client by the host whenever you freeze/unfreeze.

[0] this understanding the pros/cons of each approach and weighing them up. i'd rather have a good known snapshot to start off with each time I use it (and deal with side effects such as time sync, rng seed, handling updates, etc.) than have a long-running machine.

Does the VirtIO-RNG functionality provided by qemu help here? Linux will use it as a hardware RNG.