Re: [Qemu-devel] [PATCH for-1.6 V2 0/2] pvpanic: Separate pvpanic from machine type

[Marcel Apfelbaum <marcel.a@redhat.com>]

On Mon, 2013-08-12 at 09:53 -0600, Eric Blake wrote:
> On 08/11/2013 09:10 AM, Marcel Apfelbaum wrote:
> > Creating the pvpanic device as part of the machine type has the
> > potential to trigger guest OS, guest firmware and driver bugs.
> > The potential of such was originally viewed as minimal.
> > However, since releasing 1.5 with pvpanic as part
> > of the builtin machine type, several issues were observed
> > in the field:
> >  - Some Windows versions triggered 'New Hardware Wizard' and
> >    an unidentified device appeared in Device Manager.
> >  - Issue reported off list: on Linux >= 3.10
> >    the pvpanic driver breaks the reset on crash option:
> >    VM stops instead of being reset.
> > 
> > pvpanic device also changes monitor command behaviour in some cases,
> > such silent incompatible changes aren't expected by management tools:
> >  - Monitor command requires 'cont' before 'system_reset'
> >    in order to restart the VM after kernel panic/BSOD 
> > 
> > Note that 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.
> > 
> > These issues were raised at last KVM call. The agreement reached
> > there was that we were a bit too rash to make the device
> > a builtin, and that for 1.6 we should drop the pvpanic device from the
> > default machine type, instead teach management tools to add it by
> > default using -device pvpanic.
> > It's not clear whether changing 1.5 behaviour at this point
> > is a sane thing, so this patchset doesn't touch 1.5 machine type.
> 
> Thanks for doing this; it makes sense to get this in for 1.6.  From the
> libvirt point of view:
Eric, my pleasure!
And I really think that using "-device pvpanic" is the right thing to to do.
Marcel

> 
> Series: Reviewed-by: Eric Blake <eblake@redhat.com>
>