[PATCH] SLB shadow buffer

[Benjamin Herrenschmidt]

On Sat, 2006-08-05 at 14:45 +0200, Christoph Hellwig wrote:
> On Fri, Aug 04, 2006 at 03:53:19PM +1000, Michael Neuling wrote:
> > This adds a shadow buffer for the SLBs and regsiters it with PHYP.
> > Only the bolted SLB entries (first 3) are saved.
> 
> What is a SLB shadow buffer and why do we need it?  (I don't want to
> question the patch but rather learn a little more about lowlevel ppc64
> mmu details)

Yeah, same question :) I don't have my PAPR at hand and I'm still
travellling but I'm curious about that one... 

I would suspect it allows the HV to save/restore SLBs when sharing a
processor between partitions but then... the kernel requires that anyway
so either the current code is bogus and that's pretty bad (which I don't
think so) or maybe the fact that we didn't register the shadow caused HV
to always save/restore the entire SLB, while by using the shadow, we let
it save/restore only the bolted entries we put in there (and just
re-fault the other ones). If it's not that, then what ? :)

Ben.