Re: [v1 resend 00/12] THP support for zone device page migration

[Balbir Singh]

On 7/18/25 09:40, Matthew Brost wrote:
> On Fri, Jul 04, 2025 at 09:34:59AM +1000, Balbir Singh wrote:
...
>>
>> The nouveau dmem code has been enhanced to use the new THP migration
>> capability.
>>
>> Feedback from the RFC [2]:
>>
> 
> Thanks for the patches, results look very promising. I wanted to give
> some quick feedback:
> 

Are you seeing improvements with the patchset?

> - You appear to have missed updating hmm_range_fault, specifically
> hmm_vma_handle_pmd, to check for device-private entries and populate the
> HMM PFNs accordingly. My colleague François has a fix for this if you're
> interested.
> 

Sure, please feel free to post them. 

> - I believe copy_huge_pmd also needs to be updated to avoid installing a
> migration entry if the swap entry is device-private. I don't have an
> exact fix yet due to my limited experience with core MM. The test case
> that triggers this is fairly simple: fault in a 2MB device page on the
> GPU, then fork a process that reads the page — the kernel crashes in
> this scenario.
> 

I'd be happy to look at any traces you have or post any fixes you have

Thanks for the feedback
Balbir Singh