Messages in this thread | | | Date | Mon, 27 Feb 2006 10:09:03 +1100 | From | David Gibson <> | Subject | Re: [PATCH] Enable mprotect on huge pages |
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On Fri, Feb 24, 2006 at 02:28:44PM -0800, Andrew Morton wrote: > "Zhang, Yanmin" <yanmin_zhang@linux.intel.com> wrote: > > > > From: Zhang, Yanmin <yanmin.zhang@intel.com> > > > > 2.6.16-rc3 uses hugetlb on-demand paging, but it doesn_t support hugetlb > > mprotect. My patch against 2.6.16-rc3 enables this capability. > > > > Well I suppose that makes sense. It does assume that the normal pte > protection-changing APIs do the right thing on all architectures which > implement huge pages. That's quite possibly the case, but we should > confirm that.
Well, it will need to be huge_ptep_get_and_clear() below, not the normal version. But pte_modify should be ok. I'm not sure pte_present() is safe, either, !pte_none() is what we use elsewhere in hugetlb.c.
And.. looks like lazy_mmu_prot_update() is unsafe, too. The only arch which has something here (ia64) has a function which does icache flushes on PAGE_SIZE only.
> > + > > +void hugetlb_change_protection(struct vm_area_struct *vma, > > + unsigned long address, unsigned long end, pgprot_t newprot) > > +{ > > + struct mm_struct *mm = vma->vm_mm; > > + unsigned long start = address; > > + pte_t *ptep; > > + pte_t pte; > > + > > + BUG_ON(address >= end); > > + flush_cache_range(vma, address, end); > > + > > + spin_lock(&mm->page_table_lock); > > + for (; address < end; address += HPAGE_SIZE) { > > + ptep = huge_pte_offset(mm, address); > > + if (!ptep) > > + continue; > > + if (pte_present(*ptep)) { > > + pte = ptep_get_and_clear(mm, address, ptep); > > + pte = pte_modify(pte, newprot); > > + set_huge_pte_at(mm, addr, ptep, pte); > > + lazy_mmu_prot_update(pte); > > + } > > + } > > + spin_unlock(&mm->page_table_lock); > > + > > + flush_tlb_range(vma, start, end); > > +} >
-- David Gibson | I'll have my music baroque, and my code david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_ | _way_ _around_! http://www.ozlabs.org/~dgibson - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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