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From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
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Date: Fri, 09 Sep 2005 07:53:52 +1000
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Cc: ppc64-dev <linuxppc64-dev@ozlabs.org>,
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Subject: Re: r13 is non-volatile?
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> There's a different value in R13 depending on which cpu you're on,
> so one mustn't save R13 on one CPU and attempt to restore it on
> another.
> 
> Maybe, for ppc32, you can pretend that r13 "is like a paca"? So
> that instead of saving/restoring r13 like this, you could set it up
> at the same time/instead of setting up the paca r13?

ppc32 uses r2 for that, it contains "current".

I don't think we need to bother merging those low level CPU specific
things. We need to have a cpu32 and a cpu64 subdirs in there for things
like these, memory management, etc... imho.

Ben.