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

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Date:	Wed, 01 Oct 2008 10:33:51 -0700
From:	Alok Kataria <akataria@...are.com>
To:	"H. Peter Anvin" <hpa@...or.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.

On Wed, 2008-10-01 at 10:21 -0700, H. Peter Anvin wrote:
> Alok Kataria wrote:
> >
> > (This proposal may be adopted by other guest OSes.  However, that is not
> > a requirement because a hypervisor can expose a different CPUID
> > interface depending on the guest OS type that is specified by the VM
> > configuration.)
> >
> 
> Excuse me, but that is blatantly idiotic.  Expecting the user having to
> configure a VM to match the target OS is *exactly* as stupid as
> expecting the user to reconfigure the BIOS.  It's totally the wrong
> thing to do.

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).

Alok.
> 
>         -hpa

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