Re: [Qemu-devel] [PATCH] vl: allow "cont" from panicked state

[Michael S. Tsirkin]

On Thu, Aug 22, 2013 at 11:19:44AM +0200, Paolo Bonzini wrote:
> Il 22/08/2013 10:38, Laszlo Ersek ha scritto:
> >> > To support 1.5, libvirt should simply be ready to react to unanticipated
> >> > GUEST_PANICKED events.  reboot-on-panic will simply be broken for 1.5
> >> > and Linux 3.10+ guests. :(
> > I'm probably misunderstanding the discussion, but it might be possible
> > to disable pvpanic even in 1.5 from the host side, with the following hack:
> > 
> >   -global pvpanic.ioport=0
> > 
> > In qemu, this will either configure a working pvpanic device on ioport
> > 0, or the pvpanic device will be genuinely broken. At least it doesn't
> > (obviously) break other stuff (in v1.5.2):
> > 
> > (qemu) info mtree
> > I/O
> > 0000000000000000-000000000000ffff (prio 0, RW): io
> >   0000000000000000-0000000000000000 (prio 0, RW): pvpanic
> >   0000000000000000-0000000000000007 (prio 0, RW): dma-chan
> 
> No, you're not misunderstanding the discussion.
> 
> Depending on the priorities of the pvpanic and legacy-DMA regions, it
> would break DMA channel 0.  Channel 0 is (was) used for DRAM refresh, so
> it should not have any visible effect.  However, it may not be entirely
> disabling pvpanic, just making it mostly invisible.
> 
> Paolo

Ugh.

And now that Paolo pointed out that nothing terrible
happens even when migrating from host with pvpanic
enabled to host with pvpanic disabled, I'm inclined
to think we should just disable pvpanic in 1.5.X.

Thoughts?

-- 
MST