Commit b058ea3a authored by Joao Martins's avatar Joao Martins Committed by Alex Williamson
Browse files

vfio/iova_bitmap: refactor iova_bitmap_set() to better handle page boundaries 



Commit f38044e5 ("vfio/iova_bitmap: Fix PAGE_SIZE unaligned bitmaps")
had fixed the unaligned bitmaps by capping the remaining iterable set at
the start of the bitmap. Although, that mistakenly worked around
iova_bitmap_set() incorrectly setting bits across page boundary.

Fix this by reworking the loop inside iova_bitmap_set() to iterate over a
range of bits to set (cur_bit .. last_bit) which may span different pinned
pages, thus updating @page_idx and @offset as it sets the bits. The
previous cap to the first page is now adjusted to be always accounted
rather than when there's only a non-zero pgoff.

While at it, make @page_idx , @offset and @nbits to be unsigned int given
that it won't be more than 512 and 4096 respectively (even a bigger
PAGE_SIZE or a smaller struct page size won't make this bigger than the
above 32-bit max). Also, delete the stale kdoc on Return type.

Cc: Avihai Horon <avihaih@nvidia.com>
Fixes: f38044e5 ("vfio/iova_bitmap: Fix PAGE_SIZE unaligned bitmaps")
Co-developed-by: default avatarJason Gunthorpe <jgg@nvidia.com>
Signed-off-by: default avatarJason Gunthorpe <jgg@nvidia.com>
Signed-off-by: default avatarJoao Martins <joao.m.martins@oracle.com>
Reviewed-by: default avatarJason Gunthorpe <jgg@nvidia.com>
Tested-by: default avatarAvihai Horon <avihaih@nvidia.com>
Link: https://lore.kernel.org/r/20221129131235.38880-1-joao.m.martins@oracle.com


Signed-off-by: default avatarAlex Williamson <alex.williamson@redhat.com>
parent 2f5d8cef

drivers/vfio/iova_bitmap.c

+13 −17
Original line number Diff line number Diff line
@@ -298,9 +298,7 @@ static unsigned long iova_bitmap_mapped_remaining(struct iova_bitmap *bitmap) 
{

	unsigned long remaining, bytes;



	/* Cap to one page in the first iteration, if PAGE_SIZE unaligned. */

	bytes = !bitmap->mapped.pgoff ? bitmap->mapped.npages << PAGE_SHIFT :

					PAGE_SIZE - bitmap->mapped.pgoff;

	bytes = (bitmap->mapped.npages << PAGE_SHIFT) - bitmap->mapped.pgoff;



	remaining = bitmap->mapped_total_index - bitmap->mapped_base_index;

	remaining = min_t(unsigned long, remaining,
@@ -399,29 +397,27 @@ int iova_bitmap_for_each(struct iova_bitmap *bitmap, void *opaque, 
 * Set the bits corresponding to the range [iova .. iova+length-1] in

 * the user bitmap.

 *

 * Return: The number of bits set.

 */

void iova_bitmap_set(struct iova_bitmap *bitmap,

		     unsigned long iova, size_t length)

{

	struct iova_bitmap_map *mapped = &bitmap->mapped;

	unsigned long offset = (iova - mapped->iova) >> mapped->pgshift;

	unsigned long nbits = max_t(unsigned long, 1, length >> mapped->pgshift);

	unsigned long page_idx = offset / BITS_PER_PAGE;

	unsigned long page_offset = mapped->pgoff;

	void *kaddr;



	offset = offset % BITS_PER_PAGE;

	unsigned long cur_bit = ((iova - mapped->iova) >>

			mapped->pgshift) + mapped->pgoff * BITS_PER_BYTE;

	unsigned long last_bit = (((iova + length - 1) - mapped->iova) >>

			mapped->pgshift) + mapped->pgoff * BITS_PER_BYTE;



	do {

		unsigned long size = min(BITS_PER_PAGE - offset, nbits);

		unsigned int page_idx = cur_bit / BITS_PER_PAGE;

		unsigned int offset = cur_bit % BITS_PER_PAGE;

		unsigned int nbits = min(BITS_PER_PAGE - offset,

					 last_bit - cur_bit + 1);

		void *kaddr;



		kaddr = kmap_local_page(mapped->pages[page_idx]);

		bitmap_set(kaddr + page_offset, offset, size);

		bitmap_set(kaddr, offset, nbits);

		kunmap_local(kaddr);

		page_offset = offset = 0;

		nbits -= size;

		page_idx++;

	} while (nbits > 0);

		cur_bit += nbits;

	} while (cur_bit <= last_bit);

}

EXPORT_SYMBOL_GPL(iova_bitmap_set);