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

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Message-ID: <48E3B753.7000309@zytor.com>
Date:	Wed, 01 Oct 2008 10:45:55 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	akataria@...are.com
CC:	Jeremy Fitzhardinge <jeremy@...p.org>,
	"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>,
	Zach Amsden <zach@...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.

Alok Kataria wrote:
> 
> Hi Peter, 
> 
> Its not a user who has to do anything special here.
> There are *intelligent* VM developers out there who can export a
> different CPUid interface depending on the guest OS type. And this is
> what most of the hypervisors do (not necessarily for CPUID, but for
> other things right now).
> 

It doesn't matter, really; it's still the wrong thing to do, for the 
same reason it's the wrong thing in -- for example -- ACPI, which has 
similar "cleverness".

If we want to have a "Linux standard CPUID interface" suite we should 
just put them on a different set of numbers and let a hypervisor export 
all the interfaces.

	-hpa
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