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

It seems, this "decoupling" of the adaptors has been removed/refected
again! All those neat switches are gone with r253845