From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:60560) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1V51Hl-0001XM-RK for qemu-devel@nongnu.org; Thu, 01 Aug 2013 18:24:04 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1V51Hd-0000nz-4e for qemu-devel@nongnu.org; Thu, 01 Aug 2013 18:23:53 -0400 Received: from mail-ee0-x236.google.com ([2a00:1450:4013:c00::236]:58555) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1V51Hc-0000na-V9 for qemu-devel@nongnu.org; Thu, 01 Aug 2013 18:23:45 -0400 Received: by mail-ee0-f54.google.com with SMTP id e53so1282248eek.27 for ; Thu, 01 Aug 2013 15:23:43 -0700 (PDT) Sender: Paolo Bonzini Message-ID: <51FADFEB.1080804@redhat.com> Date: Fri, 02 Aug 2013 00:23:39 +0200 From: Paolo Bonzini MIME-Version: 1.0 References: <1375362537.4891.28.camel@localhost.localdomain> <51FA6E34.5000404@redhat.com> <51FA8C4D.70308@redhat.com> In-Reply-To: <51FA8C4D.70308@redhat.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] pvpanic device should not be automatically included as an internal device List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Eric Blake , aliguori@us.ibm.com, mst@redhat.com, hutao@cn.fujitsu.com, libvir-list@redhat.com, marcel.a@redhat.com, qemu-devel@nongnu.org, kraxel@redhat.com On 08/01/2013 06:26 PM, 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 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. This is quite different from memballoon. pvpanic is a single I/O port, it doesn't use up a PCI slot (thus causing conflicts with other devices at the same address). Perhaps this issue is simply fixed by making the _STA method return 0x0B instead of 0x0F (i.e. turning off the "show in user interface" bit). Paolo