[ofa-general] Re: [PATCH for-2.6.27 1/2] RDMA/Core: Add local dma lkey support.

[Steve Wise]

Roland Dreier wrote:
> so I applied this, but now I'm starting to wonder about how ULPs would
> use this.  As I understand things, this is really working around the
> fact that cxgb3's get_dma_mr() implementation is limited to 4G.  But how
> can a ULP know if a given device has the 4G limitation?  For every other
> device (modulo iw_nes's 1 TB limitation) get_dma_mr works fine for local
> DMA.  Thoughts?
>
>  - R.
>   

RDS and NFSRDMA will use the local_dma_lkey if the device supports it.  
If not, it will use a dma_mr with local access rights.  So using the 
local_dma_lkey is just an optimization to avoid allocating a 
local-access-only dma_mr.


Steve.