Re: [Qemu-devel] pvpanic plans?

[Michael S. Tsirkin]

On Thu, Oct 31, 2013 at 03:56:42PM +0100, Paolo Bonzini wrote:
> Il 31/10/2013 15:52, Michael S. Tsirkin ha scritto:
> >> > Yes, it does.
> > What does it break exactly?
> 
> The point of a panicked event is to examine the guest at a particular
> moment in time (e.g. host-initiated crash dump).  If you let the guest
> run, it may reboot and prevent you from getting a meaningful dump.

Well we trust guest anyway, so I think we can trust it to call halt.


> >> > But I think that, once we make the pvpanic device is
> >> > optional, to a large extent there is no bug.  Adding the pvpanic
> >> > device to the VM will make libvirt obey <oncrash> instead of the
> >> > in-guest setting, and that's it.
> >> > 
> >> > Two months have passed and no casualties have been reported due to
> >> > pvpanic.  Let's just remove the auto-pvpanic from all machine types in
> >> > 1.7 (yes, that's backwards incompatible in a strict sense), document
> >> > it in the release notes, and hope that the old QEMU versions with
> >> > mandatory pvpanic die of old age.
> > 
> > Nod. I'm fine with that.
> > 
> > I think we still need to do get rid of the PANICKED state somehow.
> > If we can't replace it with RUNNING state, let's replace it with PAUSED.
> > 
> > For example, you can't continue from panicked for some reason.
> > You can't do a reset.  But you can pause and then continue.
> 
> We need to keep the PANICKED state, but we can make it a normal
> "resumable" state.

If it's resumable how is it different from PAUSED?

> Basically it's patches 1 and 2 at
> http://permalink.gmane.org/gmane.comp.emulators.qemu/229131.  Rebasing
> will fix the problem highlighted in the commit message of patch 2.
> 
> Paolo

Looks like all transitions from paused state should be allowed from panicked
state. So why keep it separate?