Re: CURRENT: Ivy Bridge CPU (i3-3220) and Intel Bull Mountain RNG (options RDRAND_RNG)

On Tue, 30 Jul 2013 16:07:48 +0200
Julian Stecklina <jsteckli_at_os.inf.tu-dresden.de> wrote:

> On 07/30/2013 01:46 PM, O. Hartmann wrote:
> > 
> > I tried the new option "options RDRAND_RNG" on my SOHO server,
> > equipted with a Intel i3-3220 "Ivy Brdige" CPU, which is supposed
> > to have the Bull Mountain random number generator as a piece of
> > hardware in its uncore.
> >
> > Enabling the kernel option doesn't reveal any presence of such a
> > hardware number generator. "sysct kern.random" always reports 
> > 
> > kern.random.adaptors:  yarrow
> > 
> > By intentionally disallowing yarrow via commenting out options
> > YARROW_RNG, the box reports "no adaptors loaded". So, either this
> > Ivy Bridge has been castrated and ripped off by Intel of its RNG or
> > FreeBSD isn't capable of detecting it properly or I'm incapable of
> > properly configure the kernel.
> 
> This might be Erratum BV54:
> 
> Problem:
> On processors that support the RDRAND instruction, that capability
> should be reported via the setting of CPUID.01H:ECX.RDRAND[bit 30].
> Due to this erratum, that bit will not be set, and the execution of
> the RDRAND instruction will result in a #UD exception.
> 
> Implication:
> Software will not be able to utilize the RDRAND instruction
> 
> http://www.intel.de/content/dam/www/public/us/en/documents/specification-updates/3rd-gen-core-desktop-specification-update.pdf
> 
> Julian

Hello Julian,

thanks for this insight.

This sounds like I bought something which isn't functional. Well done,
Intel!

On the other hand, some places I read that the entropy generated by the
RDRAND generator is put to AES for number generating. could it be that
with no AESNI, there is implicitely no RDRAND? Just an idea. 

Oliver