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    Subject[PATCH kernel v10 13/34] powerpc/powernv: Do not set "read" flag if direction==DMA_NONE
    Date
    Normally a bitmap from the iommu_table is used to track what TCE entry
    is in use. Since we are going to use iommu_table without its locks and
    do xchg() instead, it becomes essential not to put bits which are not
    implied in the direction flag as the old TCE value (more precisely -
    the permission bits) will be used to decide whether to put the page or not.

    This adds iommu_direction_to_tce_perm() (its counterpart is there already)
    and uses it for powernv's pnv_tce_build().

    Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
    Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
    ---
    Changes:
    v9:
    * added comment why we must put only valid permission bits
    ---
    arch/powerpc/include/asm/iommu.h | 1 +
    arch/powerpc/kernel/iommu.c | 15 +++++++++++++++
    arch/powerpc/platforms/powernv/pci.c | 7 +------
    3 files changed, 17 insertions(+), 6 deletions(-)

    diff --git a/arch/powerpc/include/asm/iommu.h b/arch/powerpc/include/asm/iommu.h
    index e94a5e3..d91bd69 100644
    --- a/arch/powerpc/include/asm/iommu.h
    +++ b/arch/powerpc/include/asm/iommu.h
    @@ -200,6 +200,7 @@ extern int iommu_take_ownership(struct iommu_table *tbl);
    extern void iommu_release_ownership(struct iommu_table *tbl);

    extern enum dma_data_direction iommu_tce_direction(unsigned long tce);
    +extern unsigned long iommu_direction_to_tce_perm(enum dma_data_direction dir);

    #endif /* __KERNEL__ */
    #endif /* _ASM_IOMMU_H */
    diff --git a/arch/powerpc/kernel/iommu.c b/arch/powerpc/kernel/iommu.c
    index 8673c94..31319f8 100644
    --- a/arch/powerpc/kernel/iommu.c
    +++ b/arch/powerpc/kernel/iommu.c
    @@ -863,6 +863,21 @@ void iommu_free_coherent(struct iommu_table *tbl, size_t size,
    }
    }

    +unsigned long iommu_direction_to_tce_perm(enum dma_data_direction dir)
    +{
    + switch (dir) {
    + case DMA_BIDIRECTIONAL:
    + return TCE_PCI_READ | TCE_PCI_WRITE;
    + case DMA_FROM_DEVICE:
    + return TCE_PCI_WRITE;
    + case DMA_TO_DEVICE:
    + return TCE_PCI_READ;
    + default:
    + return 0;
    + }
    +}
    +EXPORT_SYMBOL_GPL(iommu_direction_to_tce_perm);
    +
    #ifdef CONFIG_IOMMU_API
    /*
    * SPAPR TCE API
    diff --git a/arch/powerpc/platforms/powernv/pci.c b/arch/powerpc/platforms/powernv/pci.c
    index bca2aeb..b7ea245 100644
    --- a/arch/powerpc/platforms/powernv/pci.c
    +++ b/arch/powerpc/platforms/powernv/pci.c
    @@ -576,15 +576,10 @@ static int pnv_tce_build(struct iommu_table *tbl, long index, long npages,
    unsigned long uaddr, enum dma_data_direction direction,
    struct dma_attrs *attrs, bool rm)
    {
    - u64 proto_tce;
    + u64 proto_tce = iommu_direction_to_tce_perm(direction);
    __be64 *tcep, *tces;
    u64 rpn;

    - proto_tce = TCE_PCI_READ; // Read allowed
    -
    - if (direction != DMA_TO_DEVICE)
    - proto_tce |= TCE_PCI_WRITE;
    -
    tces = tcep = ((__be64 *)tbl->it_base) + index - tbl->it_offset;
    rpn = __pa(uaddr) >> tbl->it_page_shift;

    --
    2.4.0.rc3.8.gfb3e7d5


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