On Wed, Jul 22, 2026 at 01:20:39PM -0700, Dave Hansen wrote:
> On 7/22/26 10:37, Yeoreum Yun wrote:
> >> On 7/22/26 08:30, Yeoreum Yun wrote:
> >>> struct pg_state {
> >>> struct ptdump_state ptdump;
> >>> + int first_level;
> >>> int level;
> >>> pgprotval_t current_prot;
> >>> pgprotval_t effective_prot;
> >> There is zero reason on x86 to hold this value in a data structure. It
> >> is 100% determined at boot time or earlier. Pre-5-level-paging it's a
> >> compile-time constant.
> >>
> >> On x86, it never varies per-mm.
> > 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;
+}
+
#endif /* _LINUX_PGTABLE_H */
--
Sincerely,
Yeoreum Yun
