| Message ID | 20240229223544.257207-1-alex.williamson@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Revert "vfio/type1: Unpin zero pages" | expand |
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 <david@redhat.com> > Signed-off-by: Alex Williamson <alex.williamson@redhat.com> > --- > 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 <david@redhat.com>
> From: Alex Williamson <alex.williamson@redhat.com> > 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 <david@redhat.com> > Signed-off-by: Alex Williamson <alex.williamson@redhat.com> Reviewed-by: Kevin Tian <kevin.tian@intel.com>
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; }
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 <david@redhat.com> Signed-off-by: Alex Williamson <alex.williamson@redhat.com> --- drivers/vfio/vfio_iommu_type1.c | 12 ------------ 1 file changed, 12 deletions(-)