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 ?
--
Cheers,
David
