RNDR/SS vs. SMCCC

[Andre Przywara]

On Thu, 03 Jun 2021 08:04:43 +1000
Benjamin Herrenschmidt <benh at kernel.crashing.org> wrote:

> On Mon, 2021-05-31 at 07:24 +0200, Ard Biesheuvel wrote:
> > 
> > The SMCCC interface was created not as an alternative/complement to
> > RNDR/RNDRRS, but to codify what several partners (including AWS) were
> > doing at the time:  
> 
> Talking of which, any particular reasons not to have (happy to
> contribute ours) a /dev/hwrng wrapper around SMCCC ? For various "gov
> compliance" kind of thing it's useful in addition to seeding the kernel
> CRNG.

You mean like this?
https://gitlab.arm.com/linux-arm/linux-ap/-/commit/87e3722f437f9c3f09397e0e9812e6509c94786a
This is not reviewed nor widely tested, but I used it for assessing the
quality of the SMCCC provided numbers on the Juno board using rngtest.
I think one problem was that this opens the SMCCC to userland, so the
entropy could be depleted from there (again under the assumption that
this is really a problem in practice).

I would be interested to hear opinions on this.

Cheers,
Andre