linux-kernel - RE: Use CPUID to communicate with the hypervisor.

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Message-ID: <0B53E02A2965CE4F9ADB38B34501A3A15726DBE3@orsmsx505.amr.corp.intel.com>
Date:	Mon, 29 Sep 2008 08:32:10 -0700
From:	"Nakajima, Jun" <jun.nakajima@...el.com>
To:	Avi Kivity <avi@...hat.com>, Gleb Natapov <gleb@...hat.com>
CC:	Alok Kataria <akataria@...are.com>, Ingo Molnar <mingo@...e.hu>,
	"H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	LKML <linux-kernel@...r.kernel.org>,
	the arch/x86 maintainers <x86@...nel.org>,
	Jeremy Fitzhardinge <jeremy@...p.org>,
	Rusty Russell <rusty@...tcorp.com.au>,
	Zachary Amsden <zach@...are.com>, Dan Hecht <dhecht@...are.com>
Subject: RE: Use CPUID to communicate with the hypervisor.

On 9/29/2008 12:37:23 AM, Avi Kivity wrote:
> Gleb Natapov wrote:
> > Can this interface be used to pass variable sized data from a
> > hypervisor to a gust? ACPI or DMI tables for instance.
> >
>
> In theory it can, but it would be a bad idea.  cpuid is best used to
> communicate cpu features; ACPI and DMI are (mostly) system features.

Also, we have reserved the MSRs from 0x40000000 - 0x400000FF for software use. We could use such MSRs, but what's the benefits of using those when ACPI already defined the detection mechanism?

             .
Jun Nakajima | Intel Open Source Technology Center
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