[PATCH][RFC] powerpc/64s: Use emergency stack for 0x100 system reset interrupt

[Balbir Singh]

On 13/10/16 17:51, Nicholas Piggin wrote:
> Also use EX_NMI save space. This should give cleaner debug data in
> case kernel stacks have become corrupted.
> 
> MSR_RI is kept clear for the 0x100 handler, because we can't mask it,
> and can't tolerate a reentrant NMI. Technically the 0x100 is not really
> recoverable yet, because it could trample on another emergency stack
> user. This will require a bit more work to safely implement, but for
> now we don't need to recover after a 0x100.
> 
> A little bit of the emergency stack / MSR_RI handling differences seem
> like they can be consolidated with some other handlers. I'll split those
> into a couple more patches before submitting.
> 
> I moved the MC save area in the paca out from between the general and
> slb save areas, and put it with the nmi area because it shouldn't be used
> much.

I think we should document the limitations as discussed

One of them is that sequential system resets have unpredictable behaviour
when done in quick successions. I also don't like some of the naming like
NORI, I would rather prefer NOT_RI, but thats just nit picking

Balbir Singh.