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    SubjectRe: [ofa-general] iommu dma mapping alignment requirements
     > It appears that my problem boils down to a single host page of memory
    > that is mapped for dma, and the dma address returned by dma_map_sg()
    > is _not_ 64KB aligned. Here is an example:

    > My first question is: Is there an assumption or requirement in linux
    > that dma_addressess should have the same alignment as the host address
    > they are mapped to? IE the rdma core is mapping the entire 64KB page,
    > but the mapping doesn't begin on a 64KB page boundary.

    I don't think this is explicitly documented anywhere, but it certainly
    seems that we want the bus address to be page-aligned in this case.
    For mthca/mlx4 at least, we tell the adapter what the host page size
    is (so that it knows how to align doorbell pages etc) and I think this
    sort of thing would confuse the HW.

    - R.

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      Last update: 2007-12-20 19:19    [W:0.022 / U:4.168 seconds]
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