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

[Gleb Natapov]

On Mon, Aug 05, 2013 at 06:03:34PM +0300, Michael S. Tsirkin wrote:
> 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?
> 
They take very limited pci resources and/or provide functionality that
should not be available for all guests. We do provide ACPI hotplug
device unconditionally.

> > > > 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.
By editing XML user can shoot himself in the foot, we should not prevent
that. It should not be required though.
 
> 
> > > > 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 do not see any reasonable doubt to even question the possibility :)
But see Paolo's reply.

> I think this requires an EXE installer. Being prompted for driver makes it
> possible to install one from INF.
AFAIK INF is clickable file, but regardless I do not think even _this_
patch is needed. What is needed is Windows driver for the device.

> How about changing drivers? Selecting one driver from multiple variants?
> How do you disable it if it's causing trouble, or for testing?
> 
Again, as Paolo says you can see it if you really wish.

--
			Gleb.