This reverts commit 873aefb376bbc0ed1dd2381ea1d6ec88106fdbd4.
This was a heinous workaround and it turns out it's been fixed in mm
twice since it was introduced. Most recently, commit c8070b787519
("mm: Don't pin ZERO_PAGE in pin_user_pages()") would have prevented
running up the zeropage refcount, but even before that commit
84209e87c696 ("mm/gup: reliable R/O long-term pinning in COW mappings")
avoids the vfio use case from pinning the zeropage at all, instead
replacing it with exclusive anonymous pages.
Remove this now useless overhead.
Suggested-by: David Hildenbrand <[email protected]>
Signed-off-by: Alex Williamson <[email protected]>
---
drivers/vfio/vfio_iommu_type1.c | 12 ------------
1 file changed, 12 deletions(-)
diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
index b2854d7939ce..b5c15fe8f9fc 100644
--- a/drivers/vfio/vfio_iommu_type1.c
+++ b/drivers/vfio/vfio_iommu_type1.c
@@ -567,18 +567,6 @@ static int vaddr_get_pfns(struct mm_struct *mm, unsigned long vaddr,
ret = pin_user_pages_remote(mm, vaddr, npages, flags | FOLL_LONGTERM,
pages, NULL);
if (ret > 0) {
- int i;
-
- /*
- * The zero page is always resident, we don't need to pin it
- * and it falls into our invalid/reserved test so we don't
- * unpin in put_pfn(). Unpin all zero pages in the batch here.
- */
- for (i = 0 ; i < ret; i++) {
- if (unlikely(is_zero_pfn(page_to_pfn(pages[i]))))
- unpin_user_page(pages[i]);
- }
-
*pfn = page_to_pfn(pages[0]);
goto done;
}
--
2.43.2
On 29.02.24 23:35, Alex Williamson wrote:
> This reverts commit 873aefb376bbc0ed1dd2381ea1d6ec88106fdbd4.
>
> This was a heinous workaround and it turns out it's been fixed in mm
> twice since it was introduced. Most recently, commit c8070b787519
> ("mm: Don't pin ZERO_PAGE in pin_user_pages()") would have prevented
> running up the zeropage refcount, but even before that commit
> 84209e87c696 ("mm/gup: reliable R/O long-term pinning in COW mappings")
> avoids the vfio use case from pinning the zeropage at all, instead
> replacing it with exclusive anonymous pages.
>
> Remove this now useless overhead.
>
> Suggested-by: David Hildenbrand <[email protected]>
> Signed-off-by: Alex Williamson <[email protected]>
> ---
> drivers/vfio/vfio_iommu_type1.c | 12 ------------
> 1 file changed, 12 deletions(-)
>
> diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
> index b2854d7939ce..b5c15fe8f9fc 100644
> --- a/drivers/vfio/vfio_iommu_type1.c
> +++ b/drivers/vfio/vfio_iommu_type1.c
> @@ -567,18 +567,6 @@ static int vaddr_get_pfns(struct mm_struct *mm, unsigned long vaddr,
> ret = pin_user_pages_remote(mm, vaddr, npages, flags | FOLL_LONGTERM,
> pages, NULL);
> if (ret > 0) {
> - int i;
> -
> - /*
> - * The zero page is always resident, we don't need to pin it
> - * and it falls into our invalid/reserved test so we don't
> - * unpin in put_pfn(). Unpin all zero pages in the batch here.
> - */
> - for (i = 0 ; i < ret; i++) {
> - if (unlikely(is_zero_pfn(page_to_pfn(pages[i]))))
> - unpin_user_page(pages[i]);
> - }
> -
> *pfn = page_to_pfn(pages[0]);
> goto done;
> }
Reviewed-by: David Hildenbrand <[email protected]>
--
Cheers,
David / dhildenb
> From: Alex Williamson <[email protected]>
> Sent: Friday, March 1, 2024 6:36 AM
>
> This reverts commit 873aefb376bbc0ed1dd2381ea1d6ec88106fdbd4.
>
> This was a heinous workaround and it turns out it's been fixed in mm
> twice since it was introduced. Most recently, commit c8070b787519
> ("mm: Don't pin ZERO_PAGE in pin_user_pages()") would have prevented
> running up the zeropage refcount, but even before that commit
> 84209e87c696 ("mm/gup: reliable R/O long-term pinning in COW mappings")
> avoids the vfio use case from pinning the zeropage at all, instead
> replacing it with exclusive anonymous pages.
>
> Remove this now useless overhead.
>
> Suggested-by: David Hildenbrand <[email protected]>
> Signed-off-by: Alex Williamson <[email protected]>
Reviewed-by: Kevin Tian <[email protected]>