linux-kernel - Re: [PATCH v4 3/3] vfio/type1: optimize vfio_unpin_pages

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Message-ID: <b88d58d2-59f8-4007-a6c5-d32ba4972bea@redhat.com>
Date: Tue, 17 Jun 2025 11:49:43 +0200
From: David Hildenbrand <david@...hat.com>
To: lizhe.67@...edance.com
Cc: akpm@...ux-foundation.org, alex.williamson@...hat.com,
 kvm@...r.kernel.org, linux-kernel@...r.kernel.org, linux-mm@...ck.org,
 peterx@...hat.com
Subject: Re: [PATCH v4 3/3] vfio/type1: optimize vfio_unpin_pages_remote() for
 large folio

On 17.06.25 11:47, lizhe.67@...edance.com wrote:
> On Tue, 17 Jun 2025 09:43:56 +0200, david@...hat.com wrote:
>   
>>> diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
>>> index e952bf8bdfab..d7653f4c10d5 100644
>>> --- a/drivers/vfio/vfio_iommu_type1.c
>>> +++ b/drivers/vfio/vfio_iommu_type1.c
>>> @@ -801,16 +801,43 @@ static long vfio_pin_pages_remote(struct vfio_dma *dma, unsigned long vaddr,
>>>           return pinned;
>>>    }
>>>    
>>> +/* Returned number includes the provided current page. */
>>> +static inline unsigned long folio_remaining_pages(struct folio *folio,
>>> +               struct page *page, unsigned long max_pages)
>>> +{
>>> +       if (!folio_test_large(folio))
>>> +               return 1;
>>> +       return min_t(unsigned long, max_pages,
>>> +                    folio_nr_pages(folio) - folio_page_idx(folio, page));
>>> +}
>>
>> Note that I think that should go somewhere into mm.h, and also get used
>> by GUP. So factoring it out from GUP and then using it here.
> 
> I think I need to separate this out into a distinct patch within the
> patchset. Is that correct?

Yes, that's what I would do.

-- 
Cheers,

David / dhildenb