On Wed, 3 Oct 2007, Nick Piggin wrote:
> On Tue, Oct 02, 2007 at 05:20:03PM -0500, Matt Mackall wrote:
> > In lib/pagewalk.c, I've been using the various forms of
> > {pgd,pud,pmd}_none_or_clear_bad while walking page tables as that
> > seemed the canonical way to do things. Lately (eg with -rc7-mm1),
> > these have been triggering messages like "bad pgd 0x01e3" and causing
> > nasty double faults. It appears this is actually triggered at the pmd
> > level (mm/memory.c:116), though it appears to produce the wrong
> > message.I guess the "wrong message" is an artifact of pud/pmd folding; but I get too confused by the different levels myself to want to think more about it - I'll just assume it's "right" somehow ;) > > > > Has something changed here? I'm pretty sure this used to work! Is this I don't know of anything changing here, sorry. > > not a kosher thing to do? Does it make any sense I'd repeatedly run > > into a bad pmd in the middle of bash's page table right after boot? > > The simple _none variant seems to work, but I worry that it's papering > > over a real problem. > > No, I think that should be the right thing to do for userspace pages. > You're not walking into a hugetlb area or a kernel mapping are you? > (the bad pgd: line could be important... 0x01e3 would be a linear kernel > mapping I think?). I should have spent more time reading Nick's reply and less time trying to work it out for myself! Yes, that's the conclusion I came to, for some reason you're now going beyond the user vmas and walking into the linear kernel mapping, which has _PAGE_GLOBAL and _PAGE_PSE bits set. Hugh - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
