On 12/12/16 18:38, Sricharan R wrote: > From: Mitchel Humpherys <mitch...@codeaurora.org> > > 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-...@vger.kernel.org > Reviewed-by: Robin Murphy <robin.mur...@arm.com> > Tested-by: Robin Murphy <robin.mur...@arm.com> > Acked-by: Will Deacon <will.dea...@arm.com> > Signed-off-by: Mitchel Humpherys <mitch...@codeaurora.org> > --- > Documentation/DMA-attributes.txt | 10 ++++++++++ > include/linux/dma-mapping.h | 7 +++++++ > 2 files changed, 17 insertions(+) > > diff --git a/Documentation/DMA-attributes.txt > b/Documentation/DMA-attributes.txt > index 98bf7ac..44c6bc4 100644 > --- a/Documentation/DMA-attributes.txt > +++ b/Documentation/DMA-attributes.txt > @@ -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). > diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h > index 6f3e6ca..ee31ea1 100644 > --- a/include/linux/dma-mapping.h > +++ b/include/linux/dma-mapping.h > @@ -63,6 +63,13 @@ > #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 << 8)
Oops, I spoke slightly too soon - there's a value conflict here which has been missed in the rebase. Robin > + > +/* > * 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 > * reference a dma_addr_t directly because there may be translation between >
