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

From: Alok Kataria <akataria@vmware.com>
To: "H. Peter Anvin" <hpa@zytor.com>
Cc: Jeremy Fitzhardinge <jeremy@goop.org>,
	"avi@redhat.com" <avi@redhat.com>,
	Rusty Russell <rusty@rustcorp.com.au>,
	Gerd Hoffmann <kraxel@redhat.com>, Ingo Molnar <mingo@elte.hu>,
	the arch/x86 maintainers <x86@kernel.org>,
	LKML <linux-kernel@vger.kernel.org>,
	"Nakajima, Jun" <jun.nakajima@intel.com>,
	Daniel Hecht <dhecht@vmware.com>, Zach Amsden <zach@vmware.com>,
	"virtualization@lists.linux-foundation.org" 
	<virtualization@lists.linux-foundation.org>,
	"kvm@vger.kernel.org" <kvm@vger.kernel.org>
Subject: Re: [RFC] CPUID usage for interaction between Hypervisors and Linux.
Date: Wed, 01 Oct 2008 10:33:51 -0700	[thread overview]
Message-ID: <1222882431.9381.23.camel@alok-dev1> (raw)
In-Reply-To: <48E3B19D.6060905@zytor.com>

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