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common: DMA-mapping: add DMA_ATTR_PRIVILEGED attribute

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This patch adds the DMA_ATTR_PRIVILEGED attribute to the DMA-mapping
subsystem.

Some advanced peripherals such as remote processors and GPUs perform
accesses to DMA buffers in both privileged "supervisor" and unprivileged
"user" modes.  This attribute is used to indicate to the DMA-mapping
subsystem that the buffer is fully accessible at the elevated privilege
level (and ideally inaccessible or at least read-only at the
lesser-privileged levels).

Cc: linux-doc@vger.kernel.org
Reviewed-by: Robin Murphy <robin.murphy@arm.com>
Tested-by: Robin Murphy <robin.murphy@arm.com>
Acked-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Mitchel Humpherys <mitchelh@codeaurora.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>
This commit is contained in:
Mitchel Humpherys 2017-01-06 18:58:11 +05:30 committed by Will Deacon
parent 5baf1e9d0b
commit b2fb366425
2 changed files with 17 additions and 0 deletions
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10
Documentation/DMA-attributes.txt
View File

@ -143,3 +143,13 @@ So, this provides a way for drivers to avoid those error messages on calls
where allocation failures are not a problem, and shouldn't bother the logs.
NOTE: At the moment DMA_ATTR_NO_WARN is only implemented on PowerPC.
DMA_ATTR_PRIVILEGED
------------------------------
Some advanced peripherals such as remote processors and GPUs perform
accesses to DMA buffers in both privileged "supervisor" and unprivileged
"user" modes. This attribute is used to indicate to the DMA-mapping
subsystem that the buffer is fully accessible at the elevated privilege
level (and ideally inaccessible or at least read-only at the
lesser-privileged levels).

7
include/linux/dma-mapping.h
View File

@ -62,6 +62,13 @@
*/
#define DMA_ATTR_NO_WARN (1UL << 8)
/*
* DMA_ATTR_PRIVILEGED: used to indicate that the buffer is fully
* accessible at an elevated privilege level (and ideally inaccessible or
* at least read-only at lesser-privileged levels).
*/
#define DMA_ATTR_PRIVILEGED (1UL << 9)
/*
* A dma_addr_t can hold any valid DMA or bus address for the platform.
* It can be given to a device to use as a DMA source or target. A CPU cannot