The original motivation for iommu_map_sg() was to give IOMMU drivers the chance to map an IOVA-contiguous scatterlist as efficiently as they could. It turns out that there isn't really much driver-specific business involved there, so now that the default implementation is mandatory let's just improve that - the main thing we're after is to use larger pages wherever possible, and as long as domain->pgsize_bitmap reflects reality, iommu_map() can already do that in a generic way. All we need to do is detect physically-contiguous segments and batch them into a single map operation, since whatever we do here is transparent to our caller and not bound by any segment-length restrictions on the list itself.
Speaking of efficiency, there's really very little point in duplicating the checks that iommu_map() is going to do anyway, so those get cleared up in the process. Signed-off-by: Robin Murphy <[email protected]> --- One final attempt at a clean-ish loop without descending into real code-golf madness... drivers/iommu/iommu.c | 41 ++++++++++++++++++++--------------------- 1 file changed, 20 insertions(+), 21 deletions(-) diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c index 8c15c5980299..ea8ce6322714 100644 --- a/drivers/iommu/iommu.c +++ b/drivers/iommu/iommu.c @@ -1676,33 +1676,32 @@ EXPORT_SYMBOL_GPL(iommu_unmap_fast); size_t iommu_map_sg(struct iommu_domain *domain, unsigned long iova, struct scatterlist *sg, unsigned int nents, int prot) { - struct scatterlist *s; - size_t mapped = 0; - unsigned int i, min_pagesz; + size_t len = 0, mapped = 0; + phys_addr_t start; + unsigned int i = 0; int ret; - if (unlikely(domain->pgsize_bitmap == 0UL)) - return 0; + while (i <= nents) { + phys_addr_t s_phys = sg_phys(sg); - min_pagesz = 1 << __ffs(domain->pgsize_bitmap); + if (len && s_phys != start + len) { + ret = iommu_map(domain, iova + mapped, start, len, prot); + if (ret) + goto out_err; - for_each_sg(sg, s, nents, i) { - phys_addr_t phys = page_to_phys(sg_page(s)) + s->offset; + mapped += len; + len = 0; + } - /* - * We are mapping on IOMMU page boundaries, so offset within - * the page must be 0. However, the IOMMU may support pages - * smaller than PAGE_SIZE, so s->offset may still represent - * an offset of that boundary within the CPU page. - */ - if (!IS_ALIGNED(s->offset, min_pagesz)) - goto out_err; + if (len) { + len += sg->length; + } else { + len = sg->length; + start = s_phys; + } - ret = iommu_map(domain, iova + mapped, phys, s->length, prot); - if (ret) - goto out_err; - - mapped += s->length; + if (++i < nents) + sg = sg_next(sg); } return mapped; -- 2.19.0.dirty _______________________________________________ iommu mailing list [email protected] https://lists.linuxfoundation.org/mailman/listinfo/iommu
