Re: [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 
> > > Cc: "Michael S. Tsirkin" 
> > > Cc: Paolo Bonzini 
> > > Cc: Gerd Hoffmann 
> > > Cc: Eric Blake 
> > > Cc: "Daniel P. Berrange" 
> > > Cc: Andreas Färber 
> > > Signed-off-by: Hu Tao
> >
> > 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)?
>