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 <[email protected]>
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;
> +}
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