[PATCH 2/6] 8xx: get rid of _PAGE_HWWRITE dependency in MMU.
benh at kernel.crashing.org
Thu Oct 8 09:20:17 EST 2009
On Thu, 2009-10-08 at 00:08 +0200, Joakim Tjernlund wrote:
> Benjamin Herrenschmidt <benh at kernel.crashing.org> wrote on 07/10/2009 23:14:52:
> > On Wed, 2009-10-07 at 22:46 +0200, Joakim Tjernlund wrote:
> > > + andi. r11, r10, _PAGE_USER | _PAGE_ACCESSED
> > > + cmpwi cr0, r11, _PAGE_USER | _PAGE_ACCESSED
> > > + bne- cr0, 2f
> > Did you mean _PAGE_PRESENT | _PAGE_ACCESSED ?
> > > +2:
> > > + mfspr r11, SRR1
> > > + rlwinm r11, r11, 0, 5, 3 /* clear guarded */
> > > + mtspr SRR1, r11
> > What is the above for ?
> TLB Miss will set that bit unconditionally and that is
> the same bit as protection error in TLB error.
And ? Big deal :-) IE. Once you get to InstructionAccess, it doesn't
matter if that bit is set, does it ?
> Lets start simple, shall we? :)
> Anyhow, I looked some more at that and I don't the best thing is
> to use shifts. All bits are correct if you invert RW and add an exception
> for extended coding.
Right, as long as you avoid doing a conditional branch :-)
> Because if you go to C with a protection fault, you are in trouble.
> So deal with it here. Now, I got another idea too that will make this go away
> if it work out
I don't understand your point about protection faults.
You should be able to go straight to C with -anything-, that's what I do
for all other platforms.
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