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 <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.
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