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

[Michael S. Tsirkin]

On Mon, Aug 05, 2013 at 12:20:44PM +0300, Gleb Natapov wrote:
> On Mon, Aug 05, 2013 at 12:18:26PM +0300, Michael S. Tsirkin wrote:
> > 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.
> > 
> Virtio has alternatives.

I don't see why does it matter. In any case, only
*some* virtio devices have alternatives.
What about the balloon device? VIRTIO_9P? There are more examples.
What about e.g. ivshmem?

> > > What if initially guest did not have a
> > > driver, but the it was installed?
> > 
> > You can reconfigure XML and reboot.
> > 
> Will it cause Windows reactivation? Maybe after adding several devices?

I don't think it will.
https://en.wikipedia.org/wiki/Microsoft_Product_Activation
says:
    Display adapter
    SCSI adapter
    IDE adapter
    Network adapter MAC address
    RAM amount range (e.g. 0-512 MB)
    Processor type and serial number
    Hard drive device and volume serial number
    Optical drive (e.g. DVD-ROM)

As you see we do let people change many parameters
that do affect activation.

> > > 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)?
> > 
> Which one? About how to install driver if device is not shown in the
> gui? I suppose clicking on device driver installer should do the job.

Did you try?
I think this requires an EXE installer. Being prompted for driver makes it
possible to install one from INF.
How about changing drivers? Selecting one driver from multiple variants?
How do you disable it if it's causing trouble, or for testing?


> --
> 			Gleb.