Re: [Qemu-devel] [PATCH 0/6] add paravirtualization hwrng support

[H. Peter Anvin]

On 10/31/2012 12:29 AM, Paolo Bonzini wrote:
> Related to this, rdrand's "entropy content" in the worst case will be
> only 1/255th of the data it produces: Intel documents that one 256-bit
> seed will result in up to 1022 64-bit random numbers.  Yet, it is good
> enough to drive rngd.  Would it make sense for QEMU to implement the
> same kind of stretching of /dev/random data, to avoid depleting the
> host's entropy pool too fast?

Absolutely not; in fact, we have to do data reduction in rngd for 
exactly this reason (and a Qemu backend would have to do the same). 
There is a new RDSEED instruction in newer CPUs to correct this.

        -hpa

--
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.