Benjamin Herrenschmidt <b...@kernel.crashing.org> wrote on 06/10/2009 01:15:39: > > On Tue, 2009-10-06 at 00:55 +0200, Joakim Tjernlund wrote: > > > Sure but if dirty is cleared by the kernel, then you also need to > > remove > > > write permission in the TLB or it will miss setting dirty on the > > next > > > store to the page. > > > > Dirty map to HW changed bit so if kernel clears it, the next > > store will trap to DTLB error. There I will check RW and clear it > > again > > without trapping to C. Is that OK? Not if I read you correcly below .. > > Well, if the HW has the ability to enforce trap when store with !DIRTY,
Yes, provided that the kernel invalidates the TLB too so the next access will provoke a TLB Miss, which will then provoke a TLB error. The TLB error routine checks VALID, RW and USER(if not a kernel access), then sets ACCESSED & DIRTY and writes the TLB(RPN reg). Perhaps the missing invalidate is haunting us here? > then that's fine, just map it that way, but you shouldn't have to handle > it in the DTLB error neither, the kernel will fix it up for you in > handle_pte_fault(). Does not all ppc have the Changed bit? > > I think I need to get myself an 8xx manual and figure out what that damn > MMU actually does :-) Please do, get the mpc862 users manual :) > > > No it's really !(RW _AND_ DIRTY) -> no store permitted, and > > > > .. hmm, I don't do that. I should do a > > if ( store && !(pte & (RW | DIRTY)) > > goto DSI > > in DTLB error? > > Well, if the HW does the test of DIRTY, then it's fine, as you seem to > suggest above. _something_ needs to do it, either SW or HW, ie, we need > to catch any attempt to store to a non-dirty page to set dirty. Yes, I think I do this. > > > > !(PRESENT _AND_ ACCESSED) -> no access permitted. > > > > Yes, how about those pinned kernel ptes. Do they have ACCESSED from > > start? > > They should. > > Cheers, > Ben. > > > > _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
