struct sg_table is a common structure used for describing a memory buffer. It consists of a scatterlist with memory pages and DMA addresses (sgl entry), as well as the number of scatterlist entries: CPU pages (orig_nents entry) and DMA mapped pages (nents entry).
It turned out that it was a common mistake to misuse nents and orig_nents entries, calling mapping functions with a wrong number of entries.
To avoid such issues, lets introduce a common wrapper operating directly on the struct sg_table objects, which take care of the proper use of the nents and orig_nents entries.
Signed-off-by: Marek Szyprowski m.szyprowski@samsung.com Reviewed-by: Christoph Hellwig hch@lst.de Acked-by: Joerg Roedel jroedel@suse.de Reviewed-by: Robin Murphy robin.murphy@arm.com --- For more information, see '[PATCH v5 00/38] DRM: fix struct sg_table nents vs. orig_nents misuse' thread: https://lore.kernel.org/linux-iommu/20200513132114.6046-1-m.szyprowski@samsu... --- include/linux/iommu.h | 16 ++++++++++++++++ 1 file changed, 16 insertions(+)
diff --git a/include/linux/iommu.h b/include/linux/iommu.h index 7cfd2dd..5bed18a 100644 --- a/include/linux/iommu.h +++ b/include/linux/iommu.h @@ -478,6 +478,22 @@ extern size_t iommu_map_sg_atomic(struct iommu_domain *domain, extern void iommu_set_fault_handler(struct iommu_domain *domain, iommu_fault_handler_t handler, void *token);
+/** + * iommu_map_sgtable - Map the given buffer to the IOMMU domain + * @domain: The IOMMU domain to perform the mapping + * @iova: The start address to map the buffer + * @sgt: The sg_table object describing the buffer + * @prot: IOMMU protection bits + * + * Creates a mapping at @iova for the buffer described by a scatterlist + * stored in the given sg_table object in the provided IOMMU domain. + */ +static inline size_t iommu_map_sgtable(struct iommu_domain *domain, + unsigned long iova, struct sg_table *sgt, int prot) +{ + return iommu_map_sg(domain, iova, sgt->sgl, sgt->orig_nents, prot); +} + extern void iommu_get_resv_regions(struct device *dev, struct list_head *list); extern void iommu_put_resv_regions(struct device *dev, struct list_head *list); extern void generic_iommu_put_resv_regions(struct device *dev,