Re: [PATCH] SLB shadow buffer

quoted

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 ? :)

Yep, that's it (and I do have a PAPR at hand ;-) )

Note that we could also store "volatile" entries in the shadow buffer;
that's supposed to improve performance.


Segher