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    SubjectRe: [PATCH v2 5/6] arm64/dma-mapping: Implement DMA_ATTR_PRIVILEGED_EXECUTABLE
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    On 09/07/16 03:09, Mitchel Humpherys wrote:
    > The newly added DMA_ATTR_PRIVILEGED_EXECUTABLE is useful for creating
    > mappings that are executable by 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>
    > ---
    > arch/arm64/mm/dma-mapping.c | 6 +++---
    > drivers/iommu/dma-iommu.c | 15 +++++++++++----
    > include/linux/dma-iommu.h | 3 ++-
    > 3 files changed, 16 insertions(+), 8 deletions(-)
    >
    > diff --git a/arch/arm64/mm/dma-mapping.c b/arch/arm64/mm/dma-mapping.c
    > index c566ec83719f..44f676268df6 100644
    > --- a/arch/arm64/mm/dma-mapping.c
    > +++ b/arch/arm64/mm/dma-mapping.c
    > @@ -543,7 +543,7 @@ static void *__iommu_alloc_attrs(struct device *dev, size_t size,
    > struct dma_attrs *attrs)
    > {
    > bool coherent = is_device_dma_coherent(dev);
    > - int ioprot = dma_direction_to_prot(DMA_BIDIRECTIONAL, coherent);
    > + int ioprot = dma_direction_to_prot(DMA_BIDIRECTIONAL, coherent, attrs);
    > size_t iosize = size;
    > void *addr;
    >
    > @@ -697,7 +697,7 @@ static dma_addr_t __iommu_map_page(struct device *dev, struct page *page,
    > struct dma_attrs *attrs)
    > {
    > bool coherent = is_device_dma_coherent(dev);
    > - int prot = dma_direction_to_prot(dir, coherent);
    > + int prot = dma_direction_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) &&
    > @@ -755,7 +755,7 @@ 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_direction_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 ea5a9ebf0f78..ccc6219da228 100644
    > --- a/drivers/iommu/dma-iommu.c
    > +++ b/drivers/iommu/dma-iommu.c
    > @@ -132,23 +132,30 @@ EXPORT_SYMBOL(iommu_dma_init_domain);
    > * dma_direction_to_prot - Translate DMA API directions to IOMMU API page flags

    Privilege really isn't a direction :(

    If we're going to cram more into this function it really wants renaming
    and redocumenting.

    > * @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_direction_to_prot(enum dma_data_direction dir, bool coherent,
    > + struct dma_attrs *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 (dma_get_attr(DMA_ATTR_PRIVILEGED_EXECUTABLE, attrs)) {
    > + prot &= ~IOMMU_WRITE;

    Hey, we didn't say anything anywhere about anything being privileged
    read-only! Frankly, I think this is going to create more problems that
    it solves. Implementing IOMMU_PRIV as simply unprivileged no-access
    should be sufficient.

    Robin.

    > + 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 8443bbb5c071..d5a37e58d29b 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_direction_to_prot(enum dma_data_direction dir, bool coherent,
    > + struct dma_attrs *attrs);
    >
    > /*
    > * These implement the bulk of the relevant DMA mapping callbacks, but require
    >

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