From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from eggs.gnu.org ([2001:4830:134:3::10]:41657)
	by lists.gnu.org with esmtp (Exim 4.71)
	(envelope-from <marcel.a@redhat.com>) id 1V4vxK-0005X8-MQ
	for qemu-devel@nongnu.org; Thu, 01 Aug 2013 12:42:35 -0400
Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71)
	(envelope-from <marcel.a@redhat.com>) id 1V4vxD-0002Ru-RC
	for qemu-devel@nongnu.org; Thu, 01 Aug 2013 12:42:26 -0400
Received: from mx1.redhat.com ([209.132.183.28]:14674)
	by eggs.gnu.org with esmtp (Exim 4.71)
	(envelope-from <marcel.a@redhat.com>) id 1V4vxD-0002Rg-HP
	for qemu-devel@nongnu.org; Thu, 01 Aug 2013 12:42:19 -0400
Message-ID: <1375375312.4891.33.camel@localhost.localdomain>
From: Marcel Apfelbaum <marcel.a@redhat.com>
Date: Thu, 01 Aug 2013 19:41:52 +0300
In-Reply-To: <20130801163144.GA18241@redhat.com>
References: <1375362537.4891.28.camel@localhost.localdomain>
	<51FA6E34.5000404@redhat.com> <51FA8C4D.70308@redhat.com>
	<20130801163144.GA18241@redhat.com>
Content-Type: text/plain; charset="UTF-8"
Mime-Version: 1.0
Content-Transfer-Encoding: 7bit
Subject: Re: [Qemu-devel] pvpanic device should not be automatically
 included as an internal device
List-Id: <qemu-devel.nongnu.org>
List-Unsubscribe: <https://lists.nongnu.org/mailman/options/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=unsubscribe>
List-Archive: <http://lists.nongnu.org/archive/html/qemu-devel>
List-Post: <mailto:qemu-devel@nongnu.org>
List-Help: <mailto:qemu-devel-request@nongnu.org?subject=help>
List-Subscribe: <https://lists.nongnu.org/mailman/listinfo/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=subscribe>
To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Anthony Liguori <aliguori@us.ibm.com>, "libvir-list@redhat.com" <libvir-list@redhat.com>, Hu Tao <hutao@cn.fujitsu.com>, Markus Armbruster <armbru@redhat.com>, qemu-devel@nongnu.org, Gerd Hoffmann <kraxel@redhat.com>

On Thu, 2013-08-01 at 19:31 +0300, Michael S. Tsirkin wrote:
> On Thu, Aug 01, 2013 at 10:26:53AM -0600, Eric Blake wrote:
> > On 08/01/2013 08:18 AM, Gerd Hoffmann wrote:
> > > On 08/01/13 15:08, Marcel Apfelbaum wrote:
> > >> Hi,
> > >>
> > >> The problem with pvpanic being an internal device is that VMs running
> > >> operating systems without a driver for this device will have problems
> > >> when qemu will be upgraded (from qemu without this pvpanic).
> > >>
> > >> The outcome may be, for example: in Windows(let's say XP) the Device manager
> > >> will open a "new device" wizard and the device will appear as an unrecognized device.
> > > 
> > > Only happens when also changing the machine type on upgrade as it is
> > > turned off on old machine types.
> > > 
> > > But, yes, pvpanic will show up as "Unknown device" without driver and
> > > with the funky yellow exclamation mark in device manager in windows
> > > guests.  Newer windows versions don't kick the "new device" wizard.  But
> > > still I have my doubts that it is a good idea to add it unconditionally ...
> > 
> > Automatic devices with no command line argument have proven to be a
> > nightmare for libvirt as well.  Although the just-released libvirt 1.1.1
> > now supports the <on_crash> element for controlling the command line
> > parameters of qemu related to how qemu will behave when the pvpanic
> > device is triggered, I would also welcome having the ability to control
> > whether the guest even has a pvpanic device exposed, just as we can
> > control whether a guest has a memballoon device exposed.
> 
> 
> A natural way to do this would be with -device pvpanic.
> I'm not sure why it wasn't done like this from the beginning,
> but it shouldn't be hard to redo, hopefully we can fix this
> bug in time for 1.6.
> 
I'll come up with something, hopefully in time.
Marcel