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    Subject[PATCH v5 09/24] dma-mapping: add flags to dma_map_ops to indicate PCI P2PDMA support
    Add a flags member to the dma_map_ops structure with one flag to
    indicate support for PCI P2PDMA.

    Also, add a helper to check if a device supports PCI P2PDMA.

    Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
    Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
    ---
    include/linux/dma-map-ops.h | 10 ++++++++++
    include/linux/dma-mapping.h | 5 +++++
    kernel/dma/mapping.c | 18 ++++++++++++++++++
    3 files changed, 33 insertions(+)

    diff --git a/include/linux/dma-map-ops.h b/include/linux/dma-map-ops.h
    index 752f91e5eb5d..4d4161d58ce0 100644
    --- a/include/linux/dma-map-ops.h
    +++ b/include/linux/dma-map-ops.h
    @@ -11,7 +11,17 @@

    struct cma;

    +/*
    + * Values for struct dma_map_ops.flags:
    + *
    + * DMA_F_PCI_P2PDMA_SUPPORTED: Indicates the dma_map_ops implementation can
    + * handle PCI P2PDMA pages in the map_sg/unmap_sg operation.
    + */
    +#define DMA_F_PCI_P2PDMA_SUPPORTED (1 << 0)
    +
    struct dma_map_ops {
    + unsigned int flags;
    +
    void *(*alloc)(struct device *dev, size_t size,
    dma_addr_t *dma_handle, gfp_t gfp,
    unsigned long attrs);
    diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
    index dca2b1355bb1..f7c61b2b4b5e 100644
    --- a/include/linux/dma-mapping.h
    +++ b/include/linux/dma-mapping.h
    @@ -140,6 +140,7 @@ int dma_mmap_attrs(struct device *dev, struct vm_area_struct *vma,
    unsigned long attrs);
    bool dma_can_mmap(struct device *dev);
    int dma_supported(struct device *dev, u64 mask);
    +bool dma_pci_p2pdma_supported(struct device *dev);
    int dma_set_mask(struct device *dev, u64 mask);
    int dma_set_coherent_mask(struct device *dev, u64 mask);
    u64 dma_get_required_mask(struct device *dev);
    @@ -250,6 +251,10 @@ static inline int dma_supported(struct device *dev, u64 mask)
    {
    return 0;
    }
    +static inline bool dma_pci_p2pdma_supported(struct device *dev)
    +{
    + return false;
    +}
    static inline int dma_set_mask(struct device *dev, u64 mask)
    {
    return -EIO;
    diff --git a/kernel/dma/mapping.c b/kernel/dma/mapping.c
    index c056a1468189..74858326ef94 100644
    --- a/kernel/dma/mapping.c
    +++ b/kernel/dma/mapping.c
    @@ -724,6 +724,24 @@ int dma_supported(struct device *dev, u64 mask)
    }
    EXPORT_SYMBOL(dma_supported);

    +bool dma_pci_p2pdma_supported(struct device *dev)
    +{
    + const struct dma_map_ops *ops = get_dma_ops(dev);
    +
    + /* if ops is not set, dma direct will be used which supports P2PDMA */
    + if (!ops)
    + return true;
    +
    + /*
    + * Note: dma_ops_bypass is not checked here because P2PDMA should
    + * not be used with dma mapping ops that do not have support even
    + * if the specific device is bypassing them.
    + */
    +
    + return ops->flags & DMA_F_PCI_P2PDMA_SUPPORTED;
    +}
    +EXPORT_SYMBOL_GPL(dma_pci_p2pdma_supported);
    +
    #ifdef CONFIG_ARCH_HAS_DMA_SET_MASK
    void arch_dma_set_mask(struct device *dev, u64 mask);
    #else
    --
    2.30.2
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