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    SubjectRE: [PATCH 06/16] ntb: add check and comment for link up to mw_count and mw_get_align
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    From: Logan Gunthorpe
    > On 6/29/2017 2:13 PM, Allen Hubbe wrote:
    > > Unfortunately, it is to work around hardware errata. That is not so trivial to fix.
    >
    > Can you describe more what the work around is doing? Can you share the
    > code? It seems odd that a workaround is based on the alignment
    > restrictions of the mws.

    Sure, while not making any claim that this is ready for upstream.

    It is not a workaround for alignment restrictions of the mws. It is a restriction to avoid the use of doorbells and scratchpads. Memory windows are used exclusively.

    Read msi-x local <addr,data> and send that to the peer:
    https://github.com/ntrdma/ntrdma/blob/master/drivers/ntc/ntc_ntb_msi.c#L603

    Transform peer's addr to the memory window region:
    https://github.com/ntrdma/ntrdma/blob/master/drivers/ntc/ntc_ntb_msi.c#L622

    Append a dma immediate value operation after other operations, to write the data at addr:
    https://github.com/ntrdma/ntrdma/blob/master/drivers/ntc/ntc_ntb_msi.c#L1208

    Above describes the workaround.

    Used in the context of a rdma-over-ntb driver here:
    https://github.com/ntrdma/ntrdma/blob/master/drivers/infiniband/hw/ntrdma/ntrdma_qp.c#L1585

    >
    > Logan
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