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From: Cole Robinson <crobinso@redhat.com>
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Date: Fri, 15 Apr 2016 06:41:34 -0400
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Subject: [Qemu-devel] RFC: virtio-rng and /dev/urandom
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To: libvirt-list@redhat.com, qemu-devel <qemu-devel@nongnu.org>
Cc: "Richard W.M. Jones" <rjones@redhat.com>, "Daniel P. Berrange" <berrange@redhat.com>, Peter Krempa <pkrempa@redhat.com>, Amit Shah <amit.shah@redhat.com>, mik@miknet.net, jjaburek@redhat.com, hkario@redhat.com, sgrubb@redhat.com, hpa@zytor.com, Paolo Bonzini <pbonzini@redhat.com>, Eric Blake <eblake@redhat.com>

Libvirt currently rejects using host /dev/urandom as an input source for a
virtio-rng device. The only accepted sources are /dev/random and /dev/hwrng.
This is the result of discussions on qemu-devel around when the feature was
first added (2013). Examples:

http://lists.gnu.org/archive/html/qemu-devel/2012-09/msg02387.html
https://lists.gnu.org/archive/html/qemu-devel/2013-03/threads.html#00023

libvirt's rejection of /dev/urandom has generated some complaints from users:

https://bugzilla.redhat.com/show_bug.cgi?id=1074464
* cited: http://www.2uo.de/myths-about-urandom/
http://www.redhat.com/archives/libvir-list/2016-March/msg01062.html
http://www.redhat.com/archives/libvir-list/2016-April/msg00186.html

I think it's worth having another discussion about this, at least with a
recent argument in one place so we can put it to bed. I'm CCing a bunch of
people. I think the questions are:

1) is the original recommendation to never use virtio-rng+/dev/urandom correct?

2) regardless of #1, should we continue to reject that config in libvirt?

Thanks,
Cole