Re: [PATCH v3 13/13] mm: Remove device private pages from the physical address space

Jordan Niethe
2026-01-27T23:27:29Z

Hi,

On 28/1/26 08:12, Zi Yan wrote:
>
>> diff --git a/mm/page_vma_mapped.c b/mm/page_vma_mapped.c
>> index 039a2d71e92f..e61a0e49a7c9 100644
>> --- a/mm/page_vma_mapped.c
>> +++ b/mm/page_vma_mapped.c
>> @@ -107,6 +107,7 @@ static bool map_pte(struct page_vma_mapped_walk *pvmw, pmd_t *pmdvalp,
>> static bool check_pte(struct page_vma_mapped_walk *pvmw, unsigned long pte_nr)
>> {
>> unsigned long pfn;
>> + bool device_private = false;
>> pte_t ptent = ptep_get(pvmw->pte);
>>
>> if (pvmw->flags & PVMW_MIGRATION) {
>> @@ -115,6 +116,9 @@ static bool check_pte(struct page_vma_mapped_walk *pvmw, unsigned long pte_nr)
>> if (!softleaf_is_migration(entry))
>> return false;
>>
>> + if (softleaf_is_migration_device_private(entry))
>> + device_private = true;
>> +
>> pfn = softleaf_to_pfn(entry);
>> } else if (pte_present(ptent)) {
>> pfn = pte_pfn(ptent);
>> @@ -127,8 +131,14 @@ static bool check_pte(struct page_vma_mapped_walk *pvmw, unsigned long pte_nr)
>> return false;
>>
>> pfn = softleaf_to_pfn(entry);
>> +
>> + if (softleaf_is_device_private(entry))
>> + device_private = true;
>> }
>>
>> + if ((device_private) ^ !!(pvmw->flags & PVMW_DEVICE_PRIVATE))
>
> Would “device_private != !!(pvmw->flags & PVMW_DEVICE_PRIVATE)” be more
> readable? Also I wonder if “!!” is needed here, since I remember modern
> C can convert “pvmw->flags & PVMW_DEVICE_PRIVATE” to bool.

Yeah, "!=" should work. I did need the "!!" - maybe because xor is bitwise?
If it's not needed with "!=" I"ll remove it.

>
>> + return false;
>> +
>> if ((pfn + pte_nr - 1) < pvmw->pfn)
>> return false;
>> if (pfn > (pvmw->pfn + pvmw->nr_pages - 1))
>> @@ -137,8 +147,11 @@ static bool check_pte(struct page_vma_mapped_walk *pvmw, unsigned long pte_nr)
>> }
>>
>> /* Returns true if the two ranges overlap. Careful to not overflow. */
>> -static bool check_pmd(unsigned long pfn, struct page_vma_mapped_walk *pvmw)
>> +static bool check_pmd(unsigned long pfn, bool device_private, struct page_vma_mapped_walk *pvmw)
>> {
>> + if ((device_private) ^ !!(pvmw->flags & PVMW_DEVICE_PRIVATE))
>
> Ditto.

ack.

>
> Feel free to add:
>
> Reviewed-by: Zi Yan <ziy@nvidia.com> # for MM changes

Thanks for reviewing.

>
> Best Regards,
> Yan, Zi