Messages in this thread | | | Date | Tue, 30 Dec 2008 09:14:12 +0100 | From | Nick Piggin <> | Subject | Re: early fixmap causes kmap breakage |
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On Tue, Dec 30, 2008 at 08:54:28AM +0100, Nick Piggin wrote: > On Tue, Dec 30, 2008 at 07:13:44AM +0100, Ingo Molnar wrote: > > > > * Nick Piggin <npiggin@suse.de> wrote: > > > > > On Mon, Dec 29, 2008 at 03:17:31PM -0800, Andrew Morton wrote: > > > > On Thu, 18 Dec 2008 22:15:43 +0100 > > > > Nick Piggin <npiggin@suse.de> wrote: > > > > > > > > > Hi, > > > > > > > > > > I've debugged a problem where i386+pae systems with more than a few CPUs > > > > > blow up at boot in the kmap_atomic code. > > > > > > > > ping? > > > > > > No further progress here, I'm waiting on input for how to fix this > > > "nicely". Meantime, clearing the early fixmap pte I guess works, but you > > > lose a page... is it possible to put it into .initdata or is there some > > > issue with that? (I guess on a PAE kernel, 4K isn't a big deal). > > > > yeah, 4K shouldnt be a big deal. Mind sending a patch for this? > > I don't know if we should put a warning when we encounter this condition, > to help catch other unintended uses... > > But this at least clears out the early fixmap pte and provides a contiguous > allocation... > > --- > arch/x86/mm/init_32.c | 15 ++++++++++++++- > 1 file changed, 14 insertions(+), 1 deletion(-) > > Index: linux-2.6/arch/x86/mm/init_32.c > =================================================================== > --- linux-2.6.orig/arch/x86/mm/init_32.c > +++ linux-2.6/arch/x86/mm/init_32.c > @@ -155,6 +155,7 @@ page_table_range_init(unsigned long star > unsigned long vaddr; > pgd_t *pgd; > pmd_t *pmd; > + pte_t *lastpte = NULL; > > vaddr = start; > pgd_idx = pgd_index(vaddr); > @@ -166,7 +167,19 @@ page_table_range_init(unsigned long star > pmd = pmd + pmd_index(vaddr); > for (; (pmd_idx < PTRS_PER_PMD) && (vaddr != end); > pmd++, pmd_idx++) { > - one_page_table_init(pmd); > + pte_t *pte; > + > + pte = one_page_table_init(pmd); > + if (lastpte && lastpte + PTRS_PER_PTE != pte) { > + pte_t *newpte; > + > + pmd_clear(pmd);
Hmm, no actually we do need a TLB flush here.
> + newpte = one_page_table_init(pmd); > + BUG_ON(lastpte + PTRS_PER_PTE != newpte); > + memset(newpte, pte, PAGE_SIZE);
And here we probably need a loop doing set_pte just in case the CPU speculatively loads an incomplete TLB...
> + pte = lastpte; > + } > + lastpte = pte; > > vaddr += PMD_SIZE; > }
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