[RFC/WIP] powerpc: Fix 32-bit handling of MSR_EE on exceptions

[Benjamin Herrenschmidt]

> >   /*
> >    * MSR_KERNEL is > 0x10000 on 4xx/Book-E since it include MSR_CE.
> > @@ -205,20 +208,46 @@ transfer_to_handler_cont:
> >   	mflr	r9
> >   	lwz	r11,0(r9)		/* virtual address of handler */
> >   	lwz	r9,4(r9)		/* where to go when done */
> > +#if defined(CONFIG_PPC_8xx) && defined(CONFIG_PERF_EVENTS)
> > +	mtspr	SPRN_NRI, r0
> > +#endif
> 
> That's not part of your patch, it's already in the tree.

Yup rebase glitch.

 .../...

> I tested it on the 8xx with the below changes in addition. No issue seen 
> so far.

Thanks !

I'll merge that in.

The main obscure area is that business with the irqsoff tracer and thus
the need to create stack frames around calls to trace_hardirqs_* ... we
do it in some places and not others, but I've not managed to make it
crash either. I need to get to the bottom of that, and possibly provide
proper macro helpers like ppc64 has to do it.

Cheers,
Ben.