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

[Michael S. Tsirkin]

On Mon, Aug 05, 2013 at 11:16:17AM +0300, 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 <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?

Same as any PV device really. It's exactly the same problem
as with virtio: user configures the XML properly.

> What if initially guest did not have a
> driver, but the it was installed?

You can reconfigure XML and reboot.

> If device appears for old machine
> models this is bug, otherwise I fail to see any problem.

Care answering the question that Eric Blake posed (above)?

> --
> 			Gleb.