On Mon, Aug 05, 2013 at 11:03:53AM +0200, Gerd Hoffmann wrote:
On 08/05/13 10:16, Gleb Natapov wrote:
On Mon, Aug 05, 2013 at 11:10:55AM +0300, Michael S. Tsirkin wrote:
On Mon, Aug 05, 2013 at 03:47:23PM +0800, Hu Tao wrote:
pvpanic device is an internal default device in qemu. It may cause problem when upgrading qemu from a version without pvpanic.
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. On a cluster with hundreds of such VMs, If that cluster has a health monitoring service it may show all the VMs in a "not healthy" state.
This patch is a workaround to not show pvpanic in UI to avoid the problem in Windows.
Cc: Marcel Apfelbaum email@example.com Cc: "Michael S. Tsirkin" firstname.lastname@example.org Cc: Paolo Bonzini email@example.com Cc: Gerd Hoffmann firstname.lastname@example.org Cc: Eric Blake email@example.com Cc: "Daniel P. Berrange" firstname.lastname@example.org Cc: Andreas Färber email@example.com Signed-off-by: Hu Tao firstname.lastname@example.org
Quoting from this discussion:
That may "fix" the issue of a windows guest showing the yellow ! mark, but what if, down the road, someone writes an actual windows driver that is aware of that port and how to make a windows BSOD write a panic notification to the port? How does a user go about installing such a driver if the device is not exposed in the user interface list of devices?
I think the correct way to address this is:
- don't create the device by default, only when -device pvpanic is present
- teach management to supply said -device pvpanic for guests which support the pvpanic device
That's just pushing the problem elsewhere. How management suppose to know if guest support pvpanic device?
The problem isn't new and management already does that when figuring whenever the guest should get ide/ahci/virtio-blk/virtio-scsi storage, ac97 or intel-hda sound, rtl8139/e1000/virtio nic, ...
All of those are multiple choses and some of then expect you to install drivers actually since they also do not work out of the box with all guests.
What if initially guest did not have a driver, but the it was installed?
Update the machine config then? What is so special about the pvpanic
You cannot change HW after machine is installed without risking Windows reactivation.
device that it should be treated differently from everything else?
It is simple, it does not have alternative, there is not reason to not have it. So your options are: having the device and installing driver if functionality is needed, or never have it.