linux-kernel - Re: [RFC] CPUID usage for interaction between Hypervisors and Linux.

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Message-ID: <48E41C94.7040904@kernel.org>
Date:	Wed, 01 Oct 2008 17:57:56 -0700
From:	"H. Peter Anvin" <hpa@...nel.org>
To:	Zachary Amsden <zach@...are.com>
CC:	Anthony Liguori <anthony@...emonkey.ws>,
	Jeremy Fitzhardinge <jeremy@...p.org>,
	Alok Kataria <akataria@...are.com>,
	"avi@...hat.com" <avi@...hat.com>,
	Rusty Russell <rusty@...tcorp.com.au>,
	Gerd Hoffmann <kraxel@...hat.com>, Ingo Molnar <mingo@...e.hu>,
	the arch/x86 maintainers <x86@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	"Nakajima, Jun" <jun.nakajima@...el.com>,
	Daniel Hecht <dhecht@...are.com>,
	"virtualization@...ts.linux-foundation.org" 
	<virtualization@...ts.linux-foundation.org>,
	"kvm@...r.kernel.org" <kvm@...r.kernel.org>
Subject: Re: [RFC] CPUID usage for interaction between Hypervisors	and	Linux.

H. Peter Anvin wrote:
> 
> Ah, if it was only that simple.  Transmeta actually did this, but it's 
> not as useful as you think.
> 

For what it's worth, Transmeta's implementation used CPUID leaf 
0x80860001.ECX to give the TSC frequency rounded to the nearest MHz. 
The caveat of spread-spectrum modulation applies.

	-hpa
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