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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 30.09.25 06:37, Dev Jain wrote: > > On 30/09/25 8:22 am, Anshuman Khandual wrote: >> Replace READ_ONCE() with standard page table accessors i.e pxdp_get() which >> anyways default into READ_ONCE() in cases where platform does not override. >> >> Cc: Andrew Morton >> Cc: David Hildenbrand >> Cc: linux-mm@kvack.org >> Cc: linux-kernel@vger.kernel.org >> Signed-off-by: Anshuman Khandual >> --- >> mm/ptdump.c | 8 ++++---- >> 1 file changed, 4 insertions(+), 4 deletions(-) >> >> diff --git a/mm/ptdump.c b/mm/ptdump.c >> index b600c7f864b8..18861501b533 100644 >> --- a/mm/ptdump.c >> +++ b/mm/ptdump.c >> @@ -31,7 +31,7 @@ static int ptdump_pgd_entry(pgd_t *pgd, unsigned long addr, >> unsigned long next, struct mm_walk *walk) >> { >> struct ptdump_state *st = walk->private; >> - pgd_t val = READ_ONCE(*pgd); >> + pgd_t val = pgdp_get(pgd); >> >> #if CONFIG_PGTABLE_LEVELS > 4 && \ >> (defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS)) >> @@ -54,7 +54,7 @@ static int ptdump_p4d_entry(p4d_t *p4d, unsigned long addr, >> unsigned long next, struct mm_walk *walk) >> { >> struct ptdump_state *st = walk->private; >> - p4d_t val = READ_ONCE(*p4d); >> + p4d_t val = p4dp_get(p4d); >> >> #if CONFIG_PGTABLE_LEVELS > 3 && \ >> (defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS)) >> @@ -77,7 +77,7 @@ static int ptdump_pud_entry(pud_t *pud, unsigned long addr, >> unsigned long next, struct mm_walk *walk) >> { >> struct ptdump_state *st = walk->private; >> - pud_t val = READ_ONCE(*pud); >> + pud_t val = pudp_get(pud); >> >> #if CONFIG_PGTABLE_LEVELS > 2 && \ >> (defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS)) >> @@ -100,7 +100,7 @@ static int ptdump_pmd_entry(pmd_t *pmd, unsigned long addr, >> unsigned long next, struct mm_walk *walk) >> { >> struct ptdump_state *st = walk->private; >> - pmd_t val = READ_ONCE(*pmd); >> + pmd_t val = pmdp_get(pmd); > > I believe this should go through pmdp_get_lockless(). I can see in pgtable.h that > some magic is required on some arches to decode the pmd correctly in case walking > without locks. pmdp_get_lockless() is a nasty thingy to handle selected 32bit architectures. But given that we're using ptep_get_lockless() in ptdump_pmd_entry() it probably wouldn't hurt to use pmdp_get_lockless() here. Staring at ARCH_HAS_PTDUMP, I don't think any 32bit arch would actually end up compiling ptdump.c. E.g., on x86 only X86_64 ends up selecting ARCH_HAS_PTDUMP. -- Cheers David / dhildenb