Re: [Qemu-devel] [PATCH for-1.6 1/2] don't create pvpanic device by default.

[Michael S. Tsirkin]

On Fri, Aug 02, 2013 at 10:27:31AM +0200, Paolo Bonzini wrote:
> On 08/02/2013 09:04 AM, Hu Tao wrote:
> >The problem with pvpanic being an internal device is that VMs running
> >operating systems without a driver for this device will have problems
> >when qemu will be upgraded (from qemu without this pvpanic).
> >
> >The outcome may be, 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.
> >
> >Reported-by: Marcel Apfelbaum <address@hidden>
> >Signed-off-by: Hu Tao <address@hidden>
> 
> NACK,
> 
> this is premature.  It is fundamentally a firmware problem.
> 
> We have time to apply an even smaller patch that doesn't set
> has_pvpanic to true, and delay the whole feature to 1.7, if we do
> not fix the firmware in the next two weeks.
> 
> Paolo

I think this is not just a firmware problem.  Adding device by default
was too rush, assumption was risk of guest bugs was 0.

We are now seeing problems with bios guest code and with linux guest
drivers as well.  Yes they all can be fixed, but we simply shouldn't
force this risk of broken guests on everyone.

libvirt is the main user and libvirt people
indicated their preference to creating device with
-device pvpanic rather than a built-in one that
can't be removed.

So please reconsider, and here's an ack from me.

Acked-by: Michael S. Tsirkin <address@hidden>