From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43)
	id 1NMPVV-0006UO-Sj
	for qemu-devel@nongnu.org; Sun, 20 Dec 2009 12:23:50 -0500
Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43)
	id 1NMPVQ-0006Nb-MI
	for qemu-devel@nongnu.org; Sun, 20 Dec 2009 12:23:49 -0500
Received: from [199.232.76.173] (port=54934 helo=monty-python.gnu.org)
	by lists.gnu.org with esmtp (Exim 4.43) id 1NMPVQ-0006N4-12
	for qemu-devel@nongnu.org; Sun, 20 Dec 2009 12:23:44 -0500
Received: from mx1.redhat.com ([209.132.183.28]:4333)
	by monty-python.gnu.org with esmtp (Exim 4.60)
	(envelope-from <gleb@redhat.com>) id 1NMPVP-0005OR-Gx
	for qemu-devel@nongnu.org; Sun, 20 Dec 2009 12:23:43 -0500
Date: Sun, 20 Dec 2009 19:23:41 +0200
From: Gleb Natapov <gleb@redhat.com>
Subject: Re: [Qemu-devel] cpuid problem in upstream qemu with kvm
Message-ID: <20091220172341.GB21163@redhat.com>
References: <20091214200002.GA27769@redhat.com>
	<4B2699BB.1090302@codemonkey.ws> <20091214201049.GD6150@redhat.com>
	<4B269D99.8080404@codemonkey.ws> <4B2DF334.6030208@redhat.com>
	<20091220155101.GB31257@redhat.com> <4B2E49E5.6050709@redhat.com>
	<20091220165612.GC31257@redhat.com>
	<C9DA6F14-719C-49C2-A9B5-C74A64603026@suse.de>
	<20091220171822.GD31257@redhat.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20091220171822.GD31257@redhat.com>
List-Id: qemu-devel.nongnu.org
List-Unsubscribe: <http://lists.nongnu.org/mailman/listinfo/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=unsubscribe>
List-Archive: <http://lists.gnu.org/pipermail/qemu-devel>
List-Post: <mailto:qemu-devel@nongnu.org>
List-Help: <mailto:qemu-devel-request@nongnu.org?subject=help>
List-Subscribe: <http://lists.nongnu.org/mailman/listinfo/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=subscribe>
To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: qemu-devel@nongnu.org, Alexander Graf <agraf@suse.de>, Avi Kivity <avi@redhat.com>

On Sun, Dec 20, 2009 at 07:18:22PM +0200, Michael S. Tsirkin wrote:
> On Sun, Dec 20, 2009 at 06:17:02PM +0100, Alexander Graf wrote:
> > 
> > On 20.12.2009, at 17:56, Michael S. Tsirkin wrote:
> > 
> > > On Sun, Dec 20, 2009 at 05:59:33PM +0200, Avi Kivity wrote:
> > >> On 12/20/2009 05:51 PM, Michael S. Tsirkin wrote:
> > >>> 
> > >>>> Maybe we should make -cpu host the default.  That will give the best
> > >>>> performance for casual users, more testing for newer features, and will
> > >>>> force management apps to treat migration much more seriously.  The
> > >>>> downside is that casual users upgrading their machines might experience
> > >>>> issues with Windows.  Feature compatibility is not just about migration.
> > >>>> 
> > >>> This seems very aggressive.  Can't we whitelist features that we know
> > >>> about?  Further, doesn't KVM already do this?
> > >>> 
> > >>> 
> > >> 
> > >> It does, but without -cpuid host you're stuck with qemu64 (kvm.ko  
> > >> doesn't add features userspace didn't request).
> > > 
> > > Hmm, then, shouldn't either kvm or qemu mask features that we do not
> > > emulate well enough to make windows not crash?
> > 
> > -cpu host does that already, no?
> > 
> > Alex
> 
> I expected so, but Avi here seems to say windows will crash if you
> use a new CPU with it ...
> 
Windows _may_ crash if you'll _upgrade_ your _host_ CPU.

--
			Gleb.