This is a note to let you know that I've just added the patch titled
iommufd/iova_bitmap: Consider page offset for the pages to be pinned
to the 6.6-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
iommufd-iova_bitmap-consider-page-offset-for-the-pag.patch
and it can be found in the queue-6.6 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 45eae25d68400f3a1506b398032dd75658884ddc
Author: Joao Martins <joao.m.martins@xxxxxxxxxx>
Date: Fri Feb 2 13:34:15 2024 +0000
iommufd/iova_bitmap: Consider page offset for the pages to be pinned
[ Upstream commit 4bbcbc6ea2fa379632a24c14cfb47aa603816ac6 ]
For small bitmaps that aren't PAGE_SIZE aligned *and* that are less than
512 pages in bitmap length, use an extra page to be able to cover the
entire range e.g. [1M..3G] which would be iterated more efficiently in a
single iteration, rather than two.
Fixes: b058ea3ab5af ("vfio/iova_bitmap: refactor iova_bitmap_set() to better handle page boundaries")
Link: https://lore.kernel.org/r/20240202133415.23819-10-joao.m.martins@xxxxxxxxxx
Signed-off-by: Joao Martins <joao.m.martins@xxxxxxxxxx>
Tested-by: Avihai Horon <avihaih@xxxxxxxxxx>
Signed-off-by: Jason Gunthorpe <jgg@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/drivers/vfio/iova_bitmap.c b/drivers/vfio/iova_bitmap.c
index 26ad0912cfea4..7af5b204990bb 100644
--- a/drivers/vfio/iova_bitmap.c
+++ b/drivers/vfio/iova_bitmap.c
@@ -175,18 +175,19 @@ static int iova_bitmap_get(struct iova_bitmap *bitmap)
bitmap->mapped_base_index) *
sizeof(*bitmap->bitmap), PAGE_SIZE);
- /*
- * We always cap at max number of 'struct page' a base page can fit.
- * This is, for example, on x86 means 2M of bitmap data max.
- */
- npages = min(npages, PAGE_SIZE / sizeof(struct page *));
-
/*
* Bitmap address to be pinned is calculated via pointer arithmetic
* with bitmap u64 word index.
*/
addr = bitmap->bitmap + bitmap->mapped_base_index;
+ /*
+ * We always cap at max number of 'struct page' a base page can fit.
+ * This is, for example, on x86 means 2M of bitmap data max.
+ */
+ npages = min(npages + !!offset_in_page(addr),
+ PAGE_SIZE / sizeof(struct page *));
+
ret = pin_user_pages_fast((unsigned long)addr, npages,
FOLL_WRITE, mapped->pages);
if (ret <= 0)
