Re: [Qemu-devel] pvpanic device should not be automatically included as an internal device

[Eric Blake]

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.

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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