From mboxrd@z Thu Jan  1 00:00:00 1970
From: Paolo Bonzini <pbonzini@redhat.com>
Subject: Re: Standardizing an MSR or other hypercall to get an RNG seed?
Date: Thu, 18 Sep 2014 19:17:44 +0200
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Cc: Mathew John <mathewj@microsoft.com>, Theodore Ts'o <tytso@mit.edu>,
	John Starks <John.Starks@microsoft.com>,
	kvm list <kvm@vger.kernel.org>, Gleb Natapov <gleb@kernel.org>,
	Niels Ferguson <niels@microsoft.com>,
	Andy Lutomirski <luto@amacapital.net>,
	David Hepkin <davidhep@microsoft.com>,
	"H. Peter Anvin" <hpa@zytor.com>,
	Jake Oshins <jakeo@microsoft.com>,
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To: "Nakajima, Jun" <jun.nakajima@intel.com>,
	KY Srinivasan <kys@microsoft.com>
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Il 18/09/2014 19:13, Nakajima, Jun ha scritto:
> In terms of the address for the MSR, I suggest that you choose one
> from the range between 40000000H - 400000FFH. The SDM (35.1
> ARCHITECTURAL MSRS) says "All existing and
> future processors will not implement any features using any MSR in
> this range." Hyper-V already defines many synthetic MSRs in this
> range, and I think it would be reasonable for you to pick one for this
> to avoid a conflict?

KVM is not using any MSR in that range.

However, I think it would be better to have the MSR (and perhaps CPUID)
outside the hypervisor-reserved ranges, so that it becomes
architecturally defined.  In some sense it is similar to the HYPERVISOR
CPUID feature.

Paolo