iommu/dma: Restore scatterlist offsets correctly

With the change to stashing just the IOVA-page-aligned remainder of the
CPU-page offset rather than the whole thing, the failure path in
__invalidate_sg() also needs tweaking to account for that in the case of
differing page sizes where the two offsets may not be equivalent.
Similarly in __finalise_sg(), lest the architecture-specific wrappers
later get the wrong address for cache maintenance on sync or unmap.

Fixes: 164afb1d ("iommu/dma: Use correct offset in map_sg")
Reported-by: Magnus Damm <damm+renesas@opensource.se>
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Cc: stable@ver.kernel.org # v4.4+
Signed-off-by: Joerg Roedel <jroedel@suse.de>

drivers/iommu/dma-iommu.c

@@ -403,7 +403,7 @@ static int __finalise_sg(struct device *dev, struct scatterlist *sg, int nents,
 		unsigned int s_length = sg_dma_len(s);
 		unsigned int s_dma_len = s->length;
 
-		s->offset = s_offset;
+		s->offset += s_offset;
 		s->length = s_length;
 		sg_dma_address(s) = dma_addr + s_offset;
 		dma_addr += s_dma_len;
@@ -422,7 +422,7 @@ static void __invalidate_sg(struct scatterlist *sg, int nents)
 
 	for_each_sg(sg, s, nents, i) {
 		if (sg_dma_address(s) != DMA_ERROR_CODE)
-			s->offset = sg_dma_address(s);
+			s->offset += sg_dma_address(s);
 		if (sg_dma_len(s))
 			s->length = sg_dma_len(s);
 		sg_dma_address(s) = DMA_ERROR_CODE;