Re: [PATCH] mm: Update mask post pxd_clear_bad()

[Yeo Reum Yun]

Hi Dev,

> > Since pxd_clear_bad() is an operation changing the state of the page tables,
> > we should call arch_sync_kernel_mappings() post this.
> >
> > Fixes: e80d3909be42 ("mm: track page table modifications in __apply_to_page_range()")
> > Cc: <stable@xxxxxxxxxxxxxxx>
> > Signed-off-by: Dev Jain <dev.jain@xxxxxxx>
> > ---
> >   mm/memory.c | 4 ++++
> >   1 file changed, 4 insertions(+)
> >
> > diff --git a/mm/memory.c b/mm/memory.c
> > index 78c7ee62795e..9a4a8c710be0 100644
> > --- a/mm/memory.c
> > +++ b/mm/memory.c
> > @@ -2987,6 +2987,7 @@ static int apply_to_pmd_range(struct mm_struct *mm, pud_t *pud,
> >                       if (!create)
> >                               continue;
> >                       pmd_clear_bad(pmd);
> > +                     *mask = PGTBL_PMD_MODIFIED;
>
> Oh well, I guess these should have been *mask |= PGTBL_PMD_MODIFIED.
>
>
> >               }
> >               err = apply_to_pte_range(mm, pmd, addr, next,
> >                                        fn, data, create, mask);
> > @@ -3023,6 +3024,7 @@ static int apply_to_pud_range(struct mm_struct *mm, p4d_t *p4d,
> >                       if (!create)
> >                               continue;
> >                       pud_clear_bad(pud);
> > +                     *mask = PGTBL_PUD_MODIFIED;
> >               }
> >               err = apply_to_pmd_range(mm, pud, addr, next,
> >                                        fn, data, create, mask);
> > @@ -3059,6 +3061,7 @@ static int apply_to_p4d_range(struct mm_struct *mm, pgd_t *pgd,
> >                       if (!create)
> >                               continue;
> >                       p4d_clear_bad(p4d);
> > +                     *mask = PGTBL_P4D_MODIFIED;
> >               }
> >               err = apply_to_pud_range(mm, p4d, addr, next,
> >                                        fn, data, create, mask);
> > @@ -3095,6 +3098,7 @@ static int __apply_to_page_range(struct mm_struct *mm, unsigned long addr,
> >                       if (!create)
> >                               continue;
> >                       pgd_clear_bad(pgd);
> +                     mask = PGTBL_PGD_MODIFIED;
> >               }
> >               err = apply_to_p4d_range(mm, pgd, addr, next,
> >                                        fn, data, create, &mask);

I don't think this wouldn't need.
the pXd_clear_bad() is only called at creation of each level of page table,
and when it clear, the following, apply_to_pXd_range() function would be set
the make properly via pXd_alloc() and apply_to_pte_range().

Thanks.