Re: [Qemu-devel] RFC: virtio-rng and /dev/urandom

[Paolo Bonzini <pbonzini@redhat.com>]

> Also, I do not believe /dev/urandom is FIPS compliant.  Finally, the refill
> policy is different, so it is not really true the algorithm is the same.
> 
> All in all, other than a seed value it really doesn't make any sense.  Of
> course, none of this matters on newer Intel hardware ;)

Right, but there's always the point about people that use heterogeneous
hosts and cannot pass rdrand/rdseed to the guest.  For these, we should
add a QEMU driver that uses rdrand/rdseed, and thus decouples virtio-rng
from the host /dev/* completely.

>From the libvirt POV there are various possibilities:

- Libvirt can have a libvirt.conf parameter that says "ignore whatever is
specified in the guest XML if rdrand/rdseed is available, and instead use
rdrand/rdseed".

- Libvirt can allow specifying rdrand/rdseed _and_ an additional backend,
like this:

    <backend model="cpu"/>
    <backend model="random">/dev/random</backend>

and fallback to the second if rdrand/rdseed are not available.

Paolo