[SeaBIOS] [PATCH] don't expose pvpanic device in the UI

[Gleb Natapov]

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 <marcel.a at redhat.com>
> > Cc: "Michael S. Tsirkin" <mst at redhat.com>
> > Cc: Paolo Bonzini <pbonzini at redhat.com>
> > Cc: Gerd Hoffmann <kraxel at redhat.com>
> > Cc: Eric Blake <eblake at redhat.com>
> > Cc: "Daniel P. Berrange" <berrange at redhat.com>
> > Cc: Andreas Färber <afaerber at suse.de>
> > Signed-off-by: Hu Tao <hutao at cn.fujitsu.com>
> 
> 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? What if initially guest did not have a
driver, but the it was installed? If device appears for old machine
models this is bug, otherwise I fail to see any problem.

--
			Gleb.