[PATCH v2 vfio 1/6] vfio/pds: Fix calculations in pds_vfio_dirty_sync

[Brett Creeley]

The incorrect check is being done for comparing the
iova/length being requested to sync. This can cause
the dirty sync operation to fail. Fix this by making
sure the iova offset added to the requested sync
length doesn't exceed the region_size.

Also, the region_start is assumed to always be at 0.
This can cause dirty tracking to fail because the
device/driver bitmap offset always starts at 0,
however, the region_start/iova may not. Fix this by
determining the iova offset from region_start to
determine the bitmap offset.

Fixes: f232836a9152 ("vfio/pds: Add support for dirty page tracking")
Signed-off-by: Brett Creeley <brett.creeley@xxxxxxx>
Signed-off-by: Shannon Nelson <shannon.nelson@xxxxxxx>
---
 drivers/vfio/pci/pds/dirty.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/vfio/pci/pds/dirty.c b/drivers/vfio/pci/pds/dirty.c
index c937aa6f3954..27607d7b9030 100644
--- a/drivers/vfio/pci/pds/dirty.c
+++ b/drivers/vfio/pci/pds/dirty.c
@@ -478,8 +478,7 @@ static int pds_vfio_dirty_sync(struct pds_vfio_pci_device *pds_vfio,
 		pds_vfio->vf_id, iova, length, pds_vfio->dirty.region_page_size,
 		pages, bitmap_size);
 
-	if (!length || ((dirty->region_start + iova + length) >
-			(dirty->region_start + dirty->region_size))) {
+	if (!length || ((iova - dirty->region_start + length) > dirty->region_size)) {
 		dev_err(dev, "Invalid iova 0x%lx and/or length 0x%lx to sync\n",
 			iova, length);
 		return -EINVAL;
@@ -496,7 +495,8 @@ static int pds_vfio_dirty_sync(struct pds_vfio_pci_device *pds_vfio,
 		return -EINVAL;
 	}
 
-	bmp_offset = DIV_ROUND_UP(iova / dirty->region_page_size, sizeof(u64));
+	bmp_offset = DIV_ROUND_UP((iova - dirty->region_start) /
+				  dirty->region_page_size, sizeof(u64));
 
 	dev_dbg(dev,
 		"Syncing dirty bitmap, iova 0x%lx length 0x%lx, bmp_offset %llu bmp_bytes %llu\n",
-- 
2.17.1