Linux Virtualization - Aug 2014 - [PATCH 1/2] rngd: add udev rule to source from hwrng if virtio-rng present

On 08/08/2014 02:07 AM, Amit Shah wrote:
>
> 
>>  To
>> some degree the above is obsolete when we get khwrngd widely deployed,
>> but that is a new-kernel-only kind of thing.
> 
> Right - I'm wondering if any such changes as propsed here are now
> obsolted already by khwrngd?
> 
In this case, yes, khwrngd would be a better solution for current kernels.

	-hpa

On (Fri) 08 Aug 2014 [14:46:27], H. Peter Anvin wrote:
> On 08/08/2014 02:07 AM, Amit Shah wrote:
> >
> > 
> >>  To
> >> some degree the above is obsolete when we get khwrngd widely
deployed,
> >> but that is a new-kernel-only kind of thing.
> > 
> > Right - I'm wondering if any such changes as propsed here are now
> > obsolted already by khwrngd?
> > 
> 
> In this case, yes, khwrngd would be a better solution for current kernels.
I think that's OK with me.

What's the suggested value for rng->quality, though, for virtio-rng
that I can use to ensure the kthread starts?

Should I use the 700 (70%) as proposed in the original patchset?  I'm
not exactly sure how that value will be used as well..


		Amit

On Mon, Aug 11, 2014 at 12:45:27PM +0530, Amit Shah
wrote:
> 
> What's the suggested value for rng->quality, though, for virtio-rng
> that I can use to ensure the kthread starts?
> 
> Should I use the 700 (70%) as proposed in the original patchset?  I'm
> not exactly sure how that value will be used as well..
There is no such thing as a suggested value, every number is wrong
to some degree.  The quality is an estimation of how random your
source really is; it's a property of your hardware. If the device is
virtual you're in trouble ;-)

Either you have a way to query the underlying real hardware, or
you do your whitening and entropy estimation in the backend driver --
then you can claim 100%.

	Torsten