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

[Lance Yang <lance.yang@linux.dev>]

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@kernel.org>
>> Date: Fri, 26 Jun 2026 12:03:40 +0200
>> Subject: [PATCH] tmp
>>
>> Signed-off-by: David Hildenbrand (Arm) <david@kernel.org>
>> ---
>> 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?

[...]