From: Joao Martins Date: Tue, 25 Oct 2022 19:31:14 +0000 (+0100) Subject: vfio/iova_bitmap: Fix PAGE_SIZE unaligned bitmaps X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=f38044e5ef58ad0346fdabd7027ea5c1e1a3b624;p=linux.git vfio/iova_bitmap: Fix PAGE_SIZE unaligned bitmaps iova_bitmap_set() doesn't consider the end of the page boundary when the first bitmap page offset isn't zero, and wrongly changes the consecutive page right after. Consequently this leads to missing dirty pages from reported by the device as seen from the VMM. The current logic iterates over a given number of base pages and clamps it to the remaining indexes to iterate in the last page. Instead of having to consider extra pages to pin (e.g. first and extra pages), just handle the first page as its own range and let the rest of the bitmap be handled as if it was base page aligned. This is done by changing iova_bitmap_mapped_remaining() to return PAGE_SIZE - pgoff (on the first bitmap page), and leads to pgoff being set to 0 on following iterations. Fixes: 58ccf0190d19 ("vfio: Add an IOVA bitmap support") Reported-by: Avihai Horon Tested-by: Avihai Horon Signed-off-by: Joao Martins Link: https://lore.kernel.org/r/20221025193114.58695-3-joao.m.martins@oracle.com Signed-off-by: Alex Williamson --- diff --git a/drivers/vfio/iova_bitmap.c b/drivers/vfio/iova_bitmap.c index 56816ba1be9b1..de6d6ea5c4967 100644 --- a/drivers/vfio/iova_bitmap.c +++ b/drivers/vfio/iova_bitmap.c @@ -296,11 +296,15 @@ void iova_bitmap_free(struct iova_bitmap *bitmap) */ static unsigned long iova_bitmap_mapped_remaining(struct iova_bitmap *bitmap) { - unsigned long remaining; + 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; remaining = bitmap->mapped_total_index - bitmap->mapped_base_index; remaining = min_t(unsigned long, remaining, - (bitmap->mapped.npages << PAGE_SHIFT) / sizeof(*bitmap->bitmap)); + bytes / sizeof(*bitmap->bitmap)); return remaining; }