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

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Message-ID: <53FD83B4.1030507@zytor.com>
Date:	Wed, 27 Aug 2014 00:07:32 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Paolo Bonzini <pbonzini@...hat.com>,
	Andy Lutomirski <luto@...capital.net>
CC:	Raghavendra K T <raghavendra.kt@...ux.vnet.ibm.com>,
	"Theodore Ts'o" <tytso@....edu>, Kees Cook <keescook@...omium.org>,
	kvm list <kvm@...r.kernel.org>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	Gleb Natapov <gleb@...nel.org>,
	Andrew Honig <ahonig@...gle.com>,
	Haiyang Zhang <haiyangz@...rosoft.com>,
	X86 ML <x86@...nel.org>, Bandan Das <bsd@...hat.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Srivatsa Vaddagiri <vatsa@...ux.vnet.ibm.com>,
	Daniel Borkmann <dborkman@...hat.com>,
	Alok Kataria <akataria@...are.com>,
	virtualization@...ts.linux-foundation.org
Subject: Re: GET_RNG_SEED hypercall ABI? (Re: [PATCH v5 0/5] random,x86,kvm:
 Rework arch RNG seeds and get some from kvm)

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.

	-hpa

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