Re: [Qemu-devel] [PATCH v2] rng-builtin: add an RNG backend that uses qemu_guest_getrandom()

["Daniel P. Berrangé" <berrange@redhat.com>]

On Fri, May 10, 2019 at 02:37:41PM +0200, Laurent Vivier wrote:
> On 10/05/2019 14:27, Markus Armbruster wrote:
> > Laurent Vivier <lvivier@redhat.com> writes:
> > The new rng-builtin is considerably simpler than both rng-random and
> > rng-egd.  Moreover, it just works, whereas rng-random is limited to
> > CONFIG_POSIX, and rng-egd needs egd running (which I suspect basically
> > nobody does).  Have we considered deprecating these two backends in
> > favor of rng-builtin?
> 
> I have several bugzilla involving these backends: as there are blocking, the
> virtio-rng device in the guest can hang, or crash during hot-unplug. From my
> point of view, life would be easier without them...

Are you sure about that ?

The EGD impl looks like it is requesting entropy in an async manner.

Any problem with rng-random would also affect rng-builtin, as depending
on platform / build options,  rng-builtin may just use /dev/urandom
directly.  It should only block with /dev/random really and that's only
with Linux's impl of /dev/random - some OS effectively have /dev/random
behave identically to /dev/urandom.

Regards,
Daniel
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