Re: [PATCH] powerpc/8xx: fix regression introduced by cache coherency rewrite

[Joakim Tjernlund <joakim.tjernlund@transmode.se>]

Benjamin Herrenschmidt <benh@kernel.crashing.org> wrote on 03/10/2009 12:57:28:
>
> On Sat, 2009-10-03 at 11:24 +0200, Joakim Tjernlund wrote:
> >
> > So yes, there is a missing _tlbil_va() missing for 8xx somewhere
> > but there is something more too.
> > Maybe your new filter functions and my
> >  powerpc, 8xx: DTLB Error must check for more errors.
> > will do the trick?
>
> Well, if we can't tell between a load and a store on a TLB miss, then
> we should probably let it create an unpopulated entry in all cases,
> so that we do take a proper DSI/ISI the second time around, which
> would then tell us where we come from...

While looking closer on 8xx TLB handling I noticed we were taking
an extra TLB Error when making a page dirty. Tracked it down to:
static inline pte_t pte_mkdirty(pte_t pte) {
	pte_val(pte) |= _PAGE_DIRTY; return pte; }
pte_mkdirty does not set HWWRITE thus forcing a new
TLB error to clear it. Adding HWWRITE to pte_mkdirty fixes the
problem.

Looking at (especially pte_mkclean):
static inline pte_t pte_wrprotect(pte_t pte) {
	pte_val(pte) &= ~(_PAGE_RW | _PAGE_HWWRITE); return pte; }
static inline pte_t pte_mkclean(pte_t pte) {
	pte_val(pte) &= ~(_PAGE_DIRTY | _PAGE_HWWRITE); return pte; }

it looks like a mistake not to include HWWRITE in pte_mkdirty(),
what do you think?

 Jocke