On 7/22/26 23:00, Yeoreum Yun wrote:
> On Wed, Jul 22, 2026 at 01:20:39PM -0700, Dave Hansen wrote:
>> On 7/22/26 10:37, Yeoreum Yun wrote:
>>> However, mm_pXd_folded() requires to mm for other architecture like
>>> s390. might save the mm instead of first_level and calls the
>>> ptdump_pt_level_first() with static inline version would make the
>>> constant comparison. So it requires to save *mm* structure in here.
>>
>> I'm having a really hard time parsing that.
>>
>> I think you're trying to say that the effective_prot_p*() functions need
>> to know the first level but they don't (today) need the mm_struct. If
>> they don't get the (calculated) first_level passed in, they need the
>> mm_struct instead.
>>
>> I think you're arguing 'pg_state' needs a ->first_level or a ->mm.
>> Having a pg_state->mm doesn't seem bad to me at all.
>>
>> But, it's also a little bit silly. It would not be rocket science to
>> pass an mm_struct down to the effective_prot_p*() functions. It makes a
>> whole lot of sense to me for a page table walking function to need
>> metadata from the mm_struct to walk correctly.
>
> Yes. I mean to add pg_state->mm like:
>
> diff --git a/arch/x86/mm/dump_pagetables.c b/arch/x86/mm/dump_pagetables.c
> index 2afa7a23340e..aaf00f0c6624 100644
> --- a/arch/x86/mm/dump_pagetables.c
> +++ b/arch/x86/mm/dump_pagetables.c
> @@ -38,6 +38,7 @@ struct pg_state {
> bool check_wx;
> unsigned long wx_pages;
> struct seq_file *seq;
> + struct mm_struct *mm;
> };
>
> struct addr_marker {
> @@ -254,7 +255,7 @@ static void effective_prot(struct ptdump_state *pt_st,
> int level, u64 val)
> pgprotval_t prot = val & PTE_FLAGS_MASK;
> pgprotval_t effective;
>
> - if (level > 0) {
> + if (level > pgtable_first_level(st->mm)) {
> pgprotval_t higher_prot = st->prot_levels[level - 1];
>
> effective = (higher_prot & prot & (_PAGE_USER | _PAGE_RW)) |
> @@ -452,7 +453,8 @@ bool ptdump_walk_pgd_level_core(struct seq_file *m,
> .level = -1,
> .to_dmesg = dmesg,
> .check_wx = checkwx,
> - .seq = m
> + .seq = m,
> + .mm = mm,
> };
>
> ptdump_walk_pgd(&st.ptdump, mm, pgd);
> diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h
> index 8c093c119e5a..6e7d0580db99 100644
> --- a/include/linux/pgtable.h
> +++ b/include/linux/pgtable.h
> @@ -2490,4 +2490,15 @@ pgprot_t vm_get_page_prot(vm_flags_t vm_flags)
> \
> } \
> EXPORT_SYMBOL(vm_get_page_prot);
>
> +static inline int pgtable_first_level(struct mm_struct *mm)
> +{
> + if (mm_pmd_folded(mm))
> + return 3;
> + if (mm_pud_folded(mm))
> + return 2;
> + if (mm_p4d_folded(mm))
> + return 1;
> + return 0;
> +}
In that case the function should probably be called
"mm_first_pgtable_level"
But now it gets confusing, because we have
enum pgtable_level {
PGTABLE_LEVEL_PTE = 0,
PGTABLE_LEVEL_PMD,
PGTABLE_LEVEL_PUD,
PGTABLE_LEVEL_P4D,
PGTABLE_LEVEL_PGD,
};
But maybe we can make sense of it and do
/*
* The enum values correspond to the numerical page table level,
* starting with the highest level being level 0.
*/
enum pgtable_level {
PGTABLE_LEVEL_PGD = 0,
PGTABLE_LEVEL_P4D,
PGTABLE_LEVEL_PUD,
PGTABLE_LEVEL_PMD,
PGTABLE_LEVEL_PTE,
};
static inline enum pgtable_level mm_first_pgtable_level(struct mm_struct *mm)
{
if (mm_pmd_folded(mm))
return PGTABLE_LEVEL_PMD;
if (mm_pud_folded(mm))
return PGTABLE_LEVEL_PUD;
if (mm_p4d_folded(mm))
return PGTABLE_LEVEL_P4D;
return PGTABLE_LEVEL_PGD;
}
We could even teach effective_prot() and friends to consume enum pgtable_level
now and have it all be a bit cleaner?
--
Cheers,
David
