On Tue, Jul 14, 2026 at 07:29:38PM +0200, David Hildenbrand (Arm) wrote:
> On 7/14/26 18:51, Yeoreum Yun wrote:
> > On Tue, Jul 14, 2026 at 05:08:24PM +0100, Yeoreum Yun wrote:
> >> On Tue, Jul 14, 2026 at 07:35:19AM -0700, Dave Hansen wrote:
> >>>
> >>> This is indeed an improvement and a step in the right direction! Thanks
> >>> for looking at this.
> >>>
> >>> But one of my test for whether it's good x86 code is whether there's any
> >>> actually x86-specific logic in it. Isn't this basically a translation
> >>> between the integer level number and whether it is folded?
> >>>
> >>> That seems like a common helper that more than one arch could use. Could
> >>> this be stuck in a helper so that all arch/x86 has to do is:
> >>>
> >>> if (mm_pt_level_folded(mm, level))
> >>> return;
> >>
> >> Yes. at least the level semantic in ptdump (pgd is level 0,
> >> p4d is level 1, ...) is same to all archs where use ptdump.
> >> So It seems reasonable to add this common helper in ptdump.c
> >>
> >
> > Furthermore, the effective_prot() need to require to identify whether
> > it's the first pgtable to prevent the inheriting from dummy value.
> > So I think it seems to make a ptdump_pt_level_first() like:
> >
> > diff --git a/mm/ptdump.c b/mm/ptdump.c
> > index 973020000096c..2ec5700e4be5e 100644
> > --- a/mm/ptdump.c
> > +++ b/mm/ptdump.c
> > @@ -190,6 +190,23 @@ void ptdump_walk_pgd(struct ptdump_state *st, struct
> > mm_struct *mm, pgd_t *pgd)
> > st->note_page_flush(st);
> > }
> >
> > +bool pdtump_pt_level_first(struct mm_struct *mm, int level)
> > +{
> > + if (!mm || level > CONFIG_PGTABLE_LEVELS)
> > + return false;
>
> Do we actually ever get !mm ?
Yes. for the case of s390 use mm anyway for folded check.
>
> --
> Cheers,
>
> David
--
Sincerely,
Yeoreum Yun
