Re: [Patch mm-hotfixes v4] mm/page_vma_mapped: fix device-private PMD handling

[Lance Yang]

On 2026/6/27 10:07, Wei Yang wrote:
[...]
> Hi David
>
> I did a little adjustment like below. Want to check with you at first.
>
> > >From 048ecd33673ec649e168fbbb97749a7c0e344fcd Mon Sep 17 00:00:00 2001
> > From: "David Hildenbrand (Arm)" <david@xxxxxxxxxx>
> > Date: Fri, 26 Jun 2026 12:03:40 +0200
> > Subject: [PATCH] tmp
> >
> > Signed-off-by: David Hildenbrand (Arm) <david@xxxxxxxxxx>
> > ---
> > mm/page_vma_mapped.c | 29 +++++++++++++++++------------
> > 1 file changed, 17 insertions(+), 12 deletions(-)
> >
> > diff --git a/mm/page_vma_mapped.c b/mm/page_vma_mapped.c
> > index 2ccbabfb2cc17..ed2a23a90e8dd 100644
> > --- a/mm/page_vma_mapped.c
> > +++ b/mm/page_vma_mapped.c
> > @@ -243,21 +243,31 @@ bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw)
> > 		 */
> > 		pmde = pmdp_get_lockless(pvmw->pmd);
> >
> > -		if (pmd_trans_huge(pmde) || pmd_is_migration_entry(pmde)) {
> > +		if (pmd_trans_huge(pmde) || pmd_is_migration_entry(pmde) ||
> > +		    pmd_is_device_private_entry(pmde)) {
> > 			pvmw->ptl = pmd_lock(mm, pvmw->pmd);
> > 			pmde = *pvmw->pmd;
> > -			if (!pmd_present(pmde)) {
> > +			if (pmd_is_migration_entry(pmde)) {
> > 				softleaf_t entry;
>
> How about:
> 				const softleaf_t entry = softleaf_from_pmd(pmde);
>
> > -				if (!thp_migration_supported() ||
> > -				    !(pvmw->flags & PVMW_MIGRATION))
> > +				if (!(pvmw->flags & PVMW_MIGRATION))
> > 					return not_found(pvmw);
> > 				entry = softleaf_from_pmd(pmde);
>
> could be removed.
>
> > +				if (!check_pmd(softleaf_to_pfn(entry), pvmw))
> > +					return not_found(pvmw);
> > +				return true;
> > +			} else if (pmd_is_device_private_entry(pmde)) {
> > +				softleaf_t entry;
>
> The same.
>
> > -				if (!softleaf_is_migration(entry) ||
> > -				    !check_pmd(softleaf_to_pfn(entry), pvmw))
> > +				if (pvmw->flags & PVMW_MIGRATION)
> > +					return not_found(pvmw);
> > +				entry = softleaf_from_pmd(pmde);
> > +				if (!check_pmd(softleaf_to_pfn(entry), pvmw))
> > 					return not_found(pvmw);
> > 				return true;
> > +			} else if (!pmd_present(pmde) ){
> > +				return not_found(pvmw);
> > 			}
> > 			if (likely(pmd_trans_huge(pmde))) {
> > 				if (pvmw->flags & PVMW_MIGRATION)
>
> How about merge this with above? And put at the first case?
>
> Below is what it looks like:

Why add more churn to a fix with a stable tag? Cleanup can come later no?

[...]