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
