vdpa/mlx5: Fix PA offset with unaligned starting iotlb map

When calculating the physical address range based on the iotlb and mr
[start,end) ranges, the offset of mr->start relative to map->start
is not taken into account. This leads to some incorrect and duplicate
mappings.

For the case when mr->start < map->start the code is already correct:
the range in [mr->start, map->start) was handled by a different
iteration.

Fixes: 94abbcc ("vdpa/mlx5: Add shared memory registration code")
Cc: stable@vger.kernel.org
Signed-off-by: Si-Wei Liu <si-wei.liu@oracle.com>
Signed-off-by: Dragos Tatulea <dtatulea@nvidia.com>
Message-Id: <20241021134040.975221-2-dtatulea@nvidia.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Jason Wang <jasowang@redhat.com>

Author: siwliu-kernel

drivers/vdpa/mlx5/core/mr.c

@@ -373,7 +373,7 @@ static int map_direct_mr(struct mlx5_vdpa_dev *mvdev, struct mlx5_vdpa_direct_mr
 	struct page *pg;
 	unsigned int nsg;
 	int sglen;
-	u64 pa;
+	u64 pa, offset;
 	u64 paend;
 	struct scatterlist *sg;
 	struct device *dma = mvdev->vdev.dma_dev;
@@ -396,8 +396,10 @@ static int map_direct_mr(struct mlx5_vdpa_dev *mvdev, struct mlx5_vdpa_direct_mr
 	sg = mr->sg_head.sgl;
 	for (map = vhost_iotlb_itree_first(iotlb, mr->start, mr->end - 1);
 	     map; map = vhost_iotlb_itree_next(map, mr->start, mr->end - 1)) {
-		paend = map->addr + maplen(map, mr);
-		for (pa = map->addr; pa < paend; pa += sglen) {
+		offset = mr->start > map->start ? mr->start - map->start : 0;
+		pa = map->addr + offset;
+		paend = map->addr + offset + maplen(map, mr);
+		for (; pa < paend; pa += sglen) {
 			pg = pfn_to_page(__phys_to_pfn(pa));
 			if (!sg) {
 				mlx5_vdpa_warn(mvdev, "sg null. start 0x%llx, end 0x%llx\n",