[PATCH v5 4/6] arm64/dma-mapping: Implement DMA_ATTR_PRIVILEGED

[Mitchel Humpherys]

The newly added DMA_ATTR_PRIVILEGED is useful for creating mappings that
are only accessible to privileged DMA engines.  Implement it in
dma-iommu.c so that the ARM64 DMA IOMMU mapper can make use of it.

Reviewed-by: Robin Murphy <robin.murphy@xxxxxxx>
Tested-by: Robin Murphy <robin.murphy@xxxxxxx>
Signed-off-by: Mitchel Humpherys <mitchelh@xxxxxxxxxxxxxx>
---

Notes:
    v4..v5
    
      - Simplified (suggested by Robin Murphy)
    
    v3..v4
    
      - Reworked against the new dma attrs format
    
    v2..v3
    
      - Renamed and redocumented dma_direction_to_prot.
      - Dropped the stuff making all privileged mappings read-only.

 arch/arm64/mm/dma-mapping.c |  6 +++---
 drivers/iommu/dma-iommu.c   | 10 ++++++++--
 include/linux/dma-iommu.h   |  3 ++-
 3 files changed, 13 insertions(+), 6 deletions(-)

diff --git a/arch/arm64/mm/dma-mapping.c b/arch/arm64/mm/dma-mapping.c
index c4284c432ae8..1c6f85c56115 100644
--- a/arch/arm64/mm/dma-mapping.c
+++ b/arch/arm64/mm/dma-mapping.c
@@ -556,7 +556,7 @@ static void *__iommu_alloc_attrs(struct device *dev, size_t size,
 				 unsigned long attrs)
 {
 	bool coherent = is_device_dma_coherent(dev);
-	int ioprot = dma_direction_to_prot(DMA_BIDIRECTIONAL, coherent);
+	int ioprot = dma_info_to_prot(DMA_BIDIRECTIONAL, coherent, attrs);
 	size_t iosize = size;
 	void *addr;
 
@@ -710,7 +710,7 @@ static dma_addr_t __iommu_map_page(struct device *dev, struct page *page,
 				   unsigned long attrs)
 {
 	bool coherent = is_device_dma_coherent(dev);
-	int prot = dma_direction_to_prot(dir, coherent);
+	int prot = dma_info_to_prot(dir, coherent, attrs);
 	dma_addr_t dev_addr = iommu_dma_map_page(dev, page, offset, size, prot);
 
 	if (!iommu_dma_mapping_error(dev, dev_addr) &&
@@ -768,7 +768,7 @@ static int __iommu_map_sg_attrs(struct device *dev, struct scatterlist *sgl,
 		__iommu_sync_sg_for_device(dev, sgl, nelems, dir);
 
 	return iommu_dma_map_sg(dev, sgl, nelems,
-			dma_direction_to_prot(dir, coherent));
+				dma_info_to_prot(dir, coherent, attrs));
 }
 
 static void __iommu_unmap_sg_attrs(struct device *dev,
diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
index 08a1e2f3690f..279764305005 100644
--- a/drivers/iommu/dma-iommu.c
+++ b/drivers/iommu/dma-iommu.c
@@ -129,16 +129,22 @@ int iommu_dma_init_domain(struct iommu_domain *domain, dma_addr_t base, u64 size
 EXPORT_SYMBOL(iommu_dma_init_domain);
 
 /**
- * dma_direction_to_prot - Translate DMA API directions to IOMMU API page flags
+ * dma_info_to_prot - Translate DMA API directions and attributes to IOMMU API
+ *                    page flags.
  * @dir: Direction of DMA transfer
  * @coherent: Is the DMA master cache-coherent?
+ * @attrs: DMA attributes for the mapping
  *
  * Return: corresponding IOMMU API page protection flags
  */
-int dma_direction_to_prot(enum dma_data_direction dir, bool coherent)
+int dma_info_to_prot(enum dma_data_direction dir, bool coherent,
+		     unsigned long attrs)
 {
 	int prot = coherent ? IOMMU_CACHE : 0;
 
+	if (attrs & DMA_ATTR_PRIVILEGED)
+		prot |= IOMMU_PRIV;
+
 	switch (dir) {
 	case DMA_BIDIRECTIONAL:
 		return prot | IOMMU_READ | IOMMU_WRITE;
diff --git a/include/linux/dma-iommu.h b/include/linux/dma-iommu.h
index 81c5c8d167ad..b367613d49ba 100644
--- a/include/linux/dma-iommu.h
+++ b/include/linux/dma-iommu.h
@@ -32,7 +32,8 @@ void iommu_put_dma_cookie(struct iommu_domain *domain);
 int iommu_dma_init_domain(struct iommu_domain *domain, dma_addr_t base, u64 size);
 
 /* General helpers for DMA-API <-> IOMMU-API interaction */
-int dma_direction_to_prot(enum dma_data_direction dir, bool coherent);
+int dma_info_to_prot(enum dma_data_direction dir, bool coherent,
+		     unsigned long attrs);
 
 /*
  * These implement the bulk of the relevant DMA mapping callbacks, but require
-- 
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