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SubjectRe: [HMM 12/15] mm/migrate: new memory migration helper for use with device memory v4
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On 6/30/17 5:57 PM, Jerome Glisse wrote:

> On Fri, Jun 30, 2017 at 04:19:25PM -0700, Evgeny Baskakov wrote:
>> Hi Jerome,
>>
>> It seems that the kernel can pass 0 in src_pfns for pages that it cannot
>> migrate (i.e. the kernel knows that they cannot migrate prior to calling
>> alloc_and_copy).
>>
>> So, a zero in src_pfns can mean either "the page is not allocated yet" or
>> "the page cannot migrate".
>>
>> Can migrate_vma set the MIGRATE_PFN_MIGRATE flag for not allocated pages? On
>> the driver side it is difficult to differentiate between the cases.
> So this is what is happening in v24. For thing that can not be migrated you
> get 0 and for things that are not allocated you get MIGRATE_PFN_MIGRATE like
> the updated comments in migrate.h explain.
>
> Cheers,
> Jérôme

Yes, I see the updated documentation in migrate.h. The issue seems to be gone now in v24.

Thanks!

Evgeny Baskakov
NVIDIA

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