This is a note to let you know that I've just added the patch titled vfio/iova_bitmap: refactor iova_bitmap_set() to better handle page boundaries to the 6.1-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: vfio-iova_bitmap-refactor-iova_bitmap_set-to-better-.patch and it can be found in the queue-6.1 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. commit e6f74d23bd7e34fccf8846f735bb7b78ee6f8059 Author: Joao Martins <joao.m.martins@xxxxxxxxxx> Date: Tue Nov 29 13:12:35 2022 +0000 vfio/iova_bitmap: refactor iova_bitmap_set() to better handle page boundaries [ Upstream commit b058ea3ab5afea873ab8d976277539ca9e43869a ] Commit f38044e5ef58 ("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@xxxxxxxxxx> Fixes: f38044e5ef58 ("vfio/iova_bitmap: Fix PAGE_SIZE unaligned bitmaps") Co-developed-by: Jason Gunthorpe <jgg@xxxxxxxxxx> Signed-off-by: Jason Gunthorpe <jgg@xxxxxxxxxx> Signed-off-by: Joao Martins <joao.m.martins@xxxxxxxxxx> Reviewed-by: Jason Gunthorpe <jgg@xxxxxxxxxx> Tested-by: Avihai Horon <avihaih@xxxxxxxxxx> Link: https://lore.kernel.org/r/20221129131235.38880-1-joao.m.martins@xxxxxxxxxx Signed-off-by: Alex Williamson <alex.williamson@xxxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> diff --git a/drivers/vfio/iova_bitmap.c b/drivers/vfio/iova_bitmap.c index 2dd65f040127..0f19d502f351 100644 --- a/drivers/vfio/iova_bitmap.c +++ b/drivers/vfio/iova_bitmap.c @@ -297,9 +297,7 @@ 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, @@ -398,29 +396,27 @@ 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);