From mboxrd@z Thu Jan 1 00:00:00 1970 From: robin.murphy@arm.com (Robin Murphy) Date: Tue, 25 Nov 2014 17:50:55 +0000 Subject: [PATCH] iommu: Decouple iommu_map_sg from CPU page size Message-ID: <2d38d270a532b52f73a720572f8f085dfa08321e.1416936761.git.robin.murphy@arm.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org If the IOMMU supports pages smaller than the CPU page size, segments which lie at offsets within the CPU page may be mapped based on the finer-grained IOMMU page boundaries. This minimises the amount of non-buffer memory between the CPU page boundary and the start of the segment which must be mapped and therefore exposed to the device, and brings the default iommu_map_sg implementation in line with iommu_map/unmap with respect to alignment. Signed-off-by: Robin Murphy --- Hi Joerg, I noticed this whilst wiring up DMA mapping to this new API - on arm64 we anticipate running 4k IOMMU pages with 64k CPU pages, in which case the alignment check ends up being unnecessarily strict. Regards, Robin. drivers/iommu/iommu.c | 18 ++++++++++++++---- 1 file changed, 14 insertions(+), 4 deletions(-) diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c index 08c53c5..5c4101a 100644 --- a/drivers/iommu/iommu.c +++ b/drivers/iommu/iommu.c @@ -1129,14 +1129,24 @@ size_t default_iommu_map_sg(struct iommu_domain *domain, unsigned long iova, { struct scatterlist *s; size_t mapped = 0; - unsigned int i; + unsigned int i, min_pagesz; int ret; + if (unlikely(domain->ops->pgsize_bitmap == 0UL)) + return 0; + + min_pagesz = 1 << __ffs(domain->ops->pgsize_bitmap); + for_each_sg(sg, s, nents, i) { - phys_addr_t phys = page_to_phys(sg_page(s)); + phys_addr_t phys = page_to_phys(sg_page(s)) + s->offset; - /* We are mapping on page boundarys, so offset must be 0 */ - if (s->offset) + /* + * 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; ret = iommu_map(domain, iova + mapped, phys, s->length, prot); -- 1.9.1