Re: GET_RNG_SEED hypercall ABI? (Re: [PATCH v5 0/5] random,x86,kvm: Rework arch RNG seeds and get some from kvm)

From: H. Peter Anvin
Date: Wed Aug 27 2014 - 03:08:03 EST

On 08/27/2014 12:00 AM, Paolo Bonzini wrote:
> Il 27/08/2014 01:58, Andy Lutomirski ha scritto:
>> hpa pointed out that the ABI that I chose (an MSR from the KVM range
>> and a KVM cpuid bit) is unnecessarily KVM-specific. It would be nice
>> to allocate an MSR that everyone involved can agree on and, rather
>> than relying on a cpuid bit, just have the guest probe for the MSR.
>> This leads to a few questions:
>> 1. How do we allocate an MSR? (For background, this would be an MSR
>> that either returns 64 bits of best-effort cryptographically secure
>> random data or fails with #GP.)
> Ask Intel? :)

I'm going to poke around internally. Intel might as a matter of policy
be reluctant to assign an MSR index specifically for software use, but
I'll try to find out.


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