[PATCH v4 4/6] arm64/dma-mapping: Implement DMA_ATTR_PRIVILEGED

Mitchel Humpherys
2016-07-25T19:16:41Z

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.

Signed-off-by: Mitchel Humpherys <mitchelh@codeaurora.org>
---

Notes:
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 | 16 +++++++++++-----
include/linux/dma-iommu.h | 3 ++-
3 files changed, 16 insertions(+), 9 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..5e1e495b35f8 100644
--- a/drivers/iommu/dma-iommu.c
+++ b/drivers/iommu/dma-iommu.c
@@ -129,26 +129,32 @@ 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;

switch (dir) {
case DMA_BIDIRECTIONAL:
- return prot | IOMMU_READ | IOMMU_WRITE;
+ prot |= IOMMU_READ | IOMMU_WRITE;
case DMA_TO_DEVICE:
- return prot | IOMMU_READ;
+ prot |= IOMMU_READ;
case DMA_FROM_DEVICE:
- return prot | IOMMU_WRITE;
+ prot |= IOMMU_WRITE;
default:
return 0;
}
+ if (attrs & DMA_ATTR_PRIVILEGED)
+ prot |= IOMMU_PRIV;
+ return prot;
}

static struct iova *__alloc_iova(struct iova_domain *iovad, size_t size,
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