On Mon, Aug 05, 2013 at 11:03:53AM +0200, Gerd Hoffmann wrote:
> On 08/05/13 10:16, 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 <[email protected]>
> >>> Cc: "Michael S. Tsirkin" <[email protected]>
> >>> Cc: Paolo Bonzini <[email protected]>
> >>> Cc: Gerd Hoffmann <[email protected]>
> >>> Cc: Eric Blake <[email protected]>
> >>> Cc: "Daniel P. Berrange" <[email protected]>
> >>> Cc: Andreas Färber <[email protected]>
> >>> Signed-off-by: Hu Tao <[email protected]>
> >>
> >> 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?
>
> The problem isn't new and management already does that when figuring
> whenever the guest should get ide/ahci/virtio-blk/virtio-scsi storage,
> ac97 or intel-hda sound, rtl8139/e1000/virtio nic, ...
>
All of those are multiple choses and some of then expect you to install
drivers actually since they also do not work out of the box with all guests.
> > What if initially guest did not have a
> > driver, but the it was installed?
>
> Update the machine config then? What is so special about the pvpanic
You cannot change HW after machine is installed without risking Windows
reactivation.
> device that it should be treated differently from everything else?
>
It is simple, it does not have alternative, there is not reason to not
have it. So your options are: having the device and installing driver if
functionality is needed, or never have it.
--
Gleb.
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