Re: [PATCH 2/2] x86/random: Issue a warning if RDRAND or RDSEED fails

Daniel P. Berrangé
2024-02-06T08:05:13Z

On Mon, Feb 05, 2024 at 07:12:47PM -0600, Dr. Greg wrote:
>
> Actually, I now believe there is clear evidence that the problem is
> indeed Intel specific. In light of our testing, it will be
> interesting to see what your 'AR' returns with respect to an official
> response from Intel engineering on this issue.
>
> One of the very bright young engineers collaborating on Quixote, who
> has been following this conversation, took it upon himself to do some
> very methodical engineering analysis on this issue. I'm the messenger
> but this is very much his work product.
>
> Executive summary is as follows:
>
> - No RDRAND depletion failures were observable with either the Intel
> or AMD hardware that was load tested.
>
> - RDSEED depletion is an Intel specific issue, AMD's RDSEED
> implementation could not be provoked into failure.

My colleague ran a multithread parallel stress test program on
his 16core/2HT AMD Ryzen (Zen4 uarch) and saw a 80% failure rate
in RDSEED.

> - AMD's RDRAND/RDSEED implementation is significantly slower than
> Intel's.

Yes, we also noticed the AMD impl is horribly slow compared to Intel,
had to cut test iterations x100

With regards,
Daniel
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