On 2020-05-12 10:00 am, Marek Szyprowski wrote:
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.
Modulo Joerg's comments,
Reviewed-by: Robin Murphy <robin.murphy@xxxxxxx>
Signed-off-by: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
---
For more information, see '[PATCH v4 00/38] DRM: fix struct sg_table nents
vs. orig_nents misuse' thread:
https://lore.kernel.org/dri-devel/20200512085710.14688-1-m.szyprowski@xxxxxxxxxxx/T/
---
include/linux/iommu.h | 16 ++++++++++++++++
1 file changed, 16 insertions(+)
diff --git a/include/linux/iommu.h b/include/linux/iommu.h
index 7cfd2dd..ba662ba 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 perfor
+ * @iova: The start addrees to map the buffer
+ * @sgt: The sg_table object describing the buffer
+ * @prot: IOMMU protection bits
+ *
+ * Create 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,
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