Architectures like ppc64, use privilege access bit to mark pte non accessible. This implies that kernel can do a copy_to_user to an address marked for numa fault. This also implies that there can be a parallel hardware update for the pte. set_pte_at cannot be used in such scenarios. Hence switch the pte update to use ptep_get_and_clear and set_pte_at combination.
Signed-off-by: Aneesh Kumar K.V <[email protected]> --- arch/powerpc/mm/pgtable.c | 7 +------ mm/memory.c | 18 +++++++++--------- 2 files changed, 10 insertions(+), 15 deletions(-) diff --git a/arch/powerpc/mm/pgtable.c b/arch/powerpc/mm/pgtable.c index cb39c8bd2436..b8ac81a16389 100644 --- a/arch/powerpc/mm/pgtable.c +++ b/arch/powerpc/mm/pgtable.c @@ -186,12 +186,7 @@ static pte_t set_access_flags_filter(pte_t pte, struct vm_area_struct *vma, void set_pte_at(struct mm_struct *mm, unsigned long addr, pte_t *ptep, pte_t pte) { - /* - * When handling numa faults, we already have the pte marked - * _PAGE_PRESENT, but we can be sure that it is not in hpte. - * Hence we can use set_pte_at for them. - */ - VM_WARN_ON(pte_present(*ptep) && !pte_protnone(*ptep)); + VM_WARN_ON(pte_present(*ptep)); /* * Add the pte bit when tryint set a pte diff --git a/mm/memory.c b/mm/memory.c index 6bf2b471e30c..e78bf72f30dd 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -3387,32 +3387,32 @@ static int do_numa_page(struct vm_fault *vmf) int last_cpupid; int target_nid; bool migrated = false; - pte_t pte = vmf->orig_pte; - bool was_writable = pte_write(pte); + pte_t pte; + bool was_writable = pte_write(vmf->orig_pte); int flags = 0; /* * The "pte" at this point cannot be used safely without * validation through pte_unmap_same(). It's of NUMA type but * the pfn may be screwed if the read is non atomic. - * - * We can safely just do a "set_pte_at()", because the old - * page table entry is not accessible, so there would be no - * concurrent hardware modifications to the PTE. */ vmf->ptl = pte_lockptr(vma->vm_mm, vmf->pmd); spin_lock(vmf->ptl); - if (unlikely(!pte_same(*vmf->pte, pte))) { + if (unlikely(!pte_same(*vmf->pte, vmf->orig_pte))) { pte_unmap_unlock(vmf->pte, vmf->ptl); goto out; } - /* Make it present again */ + /* + * Make it present again, Depending on how arch implementes non + * accessible ptes, some can allow access by kernel mode. + */ + pte = ptep_modify_prot_start(vma->vm_mm, vmf->address, vmf->pte); pte = pte_modify(pte, vma->vm_page_prot); pte = pte_mkyoung(pte); if (was_writable) pte = pte_mkwrite(pte); - set_pte_at(vma->vm_mm, vmf->address, vmf->pte, pte); + ptep_modify_prot_commit(vma->vm_mm, vmf->address, vmf->pte, pte); update_mmu_cache(vma, vmf->address, vmf->pte); page = vm_normal_page(vma, vmf->address, pte); -- 2.7.4
