[libvirt] virtio-rng and fd passing

[Anthony Liguori]

Eric Blake <eblake at redhat.com> writes:

> [adding libvirt]
>
> On 03/03/2013 02:05 PM, Anthony Liguori wrote:
>> Paolo Bonzini <pbonzini at redhat.com> writes:
>> 
>>> Il 02/03/2013 04:13, Anthony Liguori ha scritto:
>>>> There is no valid use-case of rng-random other than using /dev/random.
>>>> In fact, it was probably a mistake to even allow a filename to be
>>>> specified because it lets people do silly things (like /dev/urandom).
>>>>
>>>> If you want anything other than /dev/random, you should use rng-egd.
>>>
>>> /dev/hwrng makes sense too.
>> 
>> Good point.  Perhaps we should issue a warning when anything is used
>> other than /dev/random or /dev/hwrng to discourage people from doing the
>> wrong thing.  I completely understand the confusion and I think we
>> should try a bit harder to prevent people from getting it wrong.
>
> Then libvirt should also make sure that the XML we allow for non-egd
> virtio-rng is restricted to the two filenames that won't cause a qemu
> warning, or even modify the XML to not expose a filename in the first
> place.  We haven't released libvirt 1.0.3 yet, so we still have a few
> hours in which such a change could be made before the XML becomes baked
> by a release.

We've already released QEMU accepting any file name so we can't remove
that functionality but I'm very much leaning toward producing such a
warning for 1.5.

It's such an easy mistake to make and it's extremely difficult to find
good information on what you should and shouldn't do.  I think that we
(QEMU and libvirt) should try hard to steer people in the right
direction.

Regards,

Anthony Liguori

>
> -- 
> Eric Blake   eblake redhat com    +1-919-301-3266
> Libvirt virtualization library http://libvirt.org