HW_RANDOM_VIRTIO is enabled in the default kernel. Starting the vm like this enables the hwrng: /gnu/store/3rqbwx34kfa789jbywfbxl90nids08cf-run-vm.sh -device virtio-rng-pci and it works as can be verified by cat /dev/hwrng
The only missing components from what I can tell is packaging rng-tools and adding a service to add /dev/hwrng to the entropy pool on boot. https://git.kernel.org/cgit/utils/kernel/rng-tools/rng-tools.git/ > We should look into QEMU's VirtIO RNG, which could help here: > http://wiki.qemu-project.org/Features-Done/VirtIORNG
