[v4,03/38] iommu: add generic helper for mapping sgtable objects

Message ID 20200512090058.14910-3-m.szyprowski@samsung.com
State Superseded
Headers show
Series
  • DRM: fix struct sg_table nents vs. orig_nents misuse
Related show

Commit Message

Marek Szyprowski May 12, 2020, 9 a.m.
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>

---
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@samsung.com/T/
---
 include/linux/iommu.h | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

-- 
1.9.1

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Comments

Robin Murphy May 13, 2020, 1:27 p.m. | #1
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@arm.com>


> Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>

> ---

> 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@samsung.com/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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Patch

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,