From: Joao Martins joao.m.martins@oracle.com
[ Upstream commit f38044e5ef58ad0346fdabd7027ea5c1e1a3b624 ]
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 avihaih@nvidia.com Tested-by: Avihai Horon avihaih@nvidia.com Signed-off-by: Joao Martins joao.m.martins@oracle.com Link: https://lore.kernel.org/r/20221025193114.58695-3-joao.m.martins@oracle.com Signed-off-by: Alex Williamson alex.williamson@redhat.com Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/vfio/iova_bitmap.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-)
diff --git a/drivers/vfio/iova_bitmap.c b/drivers/vfio/iova_bitmap.c index 6631e8befe1b..2dd65f040127 100644 --- a/drivers/vfio/iova_bitmap.c +++ b/drivers/vfio/iova_bitmap.c @@ -295,11 +295,15 @@ 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; }