Re: [Qemu-ppc] [Qemu-devel] [PATCH 2/4] ppc: add CPU IRQ state to PPC VMStateDescription

[David Gibson]

On Wed, Sep 13, 2017 at 12:23:13PM +1000, Alexey Kardashevskiy wrote:
> On 13/09/17 02:46, Mark Cave-Ayland wrote:
> > On 12/09/17 17:41, Mark Cave-Ayland wrote:
> > 
> >> The commit message mentions that prior to the conversion some CPU state
> >> was missing but it doesn't mention anything about dropping existing
> >> fields as part of the conversion process so I suspect that this was an
> >> accidental side-effect.
> > 
> > Actually I've clicked send a little too early here since re-reading the
> > last paragraph of a90db15 I can see the inference here: "Exactly what
> > needs to be saved in what configurations has been more carefully
> > examined, too".
> > 
> > Alexey - do you recall from your analysis why these fields were no
> > longer deemed necessary, and how your TCG tests were configured?
> 
> I most certainly did not do analysis (my bad. sorry) - I took the patch
> from David as he left the team, fixed to compile and pushed away. I am also
> very suspicions we did not try migrating TCG or anything but pseries. My
> guest that things did not break (if they did not which I am not sure about,
> for the TCG case) because the interrupt controller (XICS) or the
> pseries-guest took care of resending an interrupt which does not seem to be
> the case for mac99.

Right, that's probably true.  The main point, though, is that these
fields were dropped a *long* time ago, when migration was barely
working to begin with.  In particular I'm pretty sure most of the
non-pseries platforms were already pretty broken for migration
(amongst other things).

Polishing the mac platforms up to working again, including migration,
is a reasonable goal.  But it can't be at the expense of pseries,
which is already working, used in production, and much better tested
than mac99 or g3beige ever were.

-- 
David Gibson                    | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au  | minimalist, thank you.  NOT _the_ _other_
                                | _way_ _around_!
http://www.ozlabs.org/~dgibson

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