On Mon, Aug 11, 2014 at 03:45:50PM -0700, Olav Haugan wrote:

Mapping and unmapping are more often than not in the critical path.
map_sg and unmap_sg allows IOMMU driver implementations to optimize
the process of mapping and unmapping buffers into the IOMMU page tables.

Instead of mapping a buffer one page at a time and requiring potentially
expensive TLB operations for each page, this function allows the driver
to map all pages in one go and defer TLB maintenance until after all
pages have been mapped.

Additionally, the mapping operation would be faster in general since
clients does not have to keep calling map API over and over again for
each physically contiguous chunk of memory that needs to be mapped to a
virtually contiguous region.

Signed-off-by: Olav Haugan <redacted>

Thank you for changing it this way.


.. snip..

+	for_each_sg(sg, s, nents, i) {
+		phys_addr_t phys = page_to_phys(sg_page(s));
+		size_t page_len = s->offset + s->length;
+
+		ret = iommu_map(domain, iova + offset, phys, page_len,
+				prot);
+		if (ret) {
+			/* undo mappings already done */
+			iommu_unmap(domain, iova, offset);

Don't we want then to unmap all of the scatter list instead of just
the last one?

+			break;
+		}
+		offset += page_len;
+	}
+
+	return ret;
+}