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Revert "vfio/type1: Unpin zero pages"

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This reverts commit 873aefb376.

This was a heinous workaround and it turns out it's been fixed in mm
twice since it was introduced.  Most recently, commit c8070b7875
("mm: Don't pin ZERO_PAGE in pin_user_pages()") would have prevented
running up the zeropage refcount, but even before that commit
84209e87c6 ("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 <david@redhat.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Link: https://lore.kernel.org/r/20240229223544.257207-1-alex.williamson@redhat.com
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
This commit is contained in:
Alex Williamson 2024-02-29 15:35:40 -07:00
parent 81617c17bf
commit 5b99241277
1 changed files with 0 additions and 12 deletions
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12
drivers/vfio/vfio_iommu_type1.c
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@ -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;
}