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

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Message-ID: <91a36928-5c92-47c4-8b4d-1c0ad320671a@nvidia.com>
Date: Wed, 28 Jan 2026 10:26:55 +1100
From: Jordan Niethe <jniethe@...dia.com>
To: Zi Yan <ziy@...dia.com>
Cc: linux-mm@...ck.org, balbirs@...dia.com, matthew.brost@...el.com,
 akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
 dri-devel@...ts.freedesktop.org, david@...hat.com, apopple@...dia.com,
 lorenzo.stoakes@...cle.com, lyude@...hat.com, dakr@...nel.org,
 airlied@...il.com, simona@...ll.ch, rcampbell@...dia.com,
 mpenttil@...hat.com, jgg@...dia.com, willy@...radead.org,
 linuxppc-dev@...ts.ozlabs.org, intel-xe@...ts.freedesktop.org, jgg@...pe.ca,
 Felix.Kuehling@....com, jhubbard@...dia.com
Subject: Re: [PATCH v3 13/13] mm: Remove device private pages from the
 physical address space

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@...dia.com> # for MM changes

Thanks for reviewing.

> 
> Best Regards,
> Yan, Zi