On Tue, Jul 14, 2015 at 02:58:23PM -0500, Steve Wise wrote: > The local_dma_lkey can be used in any rdma sge that requires an > lkey. No, this is where iWarp doesn't follow the generic API - a local dma lkey cannot be used with iWarp's RDMA_READ WR lkey. In effect RDMA READ requires an *rkey* (confusingly stuck into the lkey slot) for iWarp. (Right?) *THAT* is really the core difference between IB and iWarp in this area, not that the access flags are different. (cap_rmda_read_lkey_is_rkey ?) > domain. But I claim for lkeys, the PD doesn't really protect > anything since the remote peers can't use it anyway. I agree. To use a PD properly I'd have thought it should be created on a client by client basis. The risk is tiny, but client X should not be able to guess Y's RKey and then corrupt a data transfer. *Especially* on a server if client X hasn't auth'd yet .... That is what the PD is for. > There is confusion about lkeys and rkeys with regard to iWARP. In > the iWARP verbs, there is no distinction between an lkey and rkey: > they are the same key, called a Steering Tag or STAG. When you > create a MR, the lkey == rkey == STAG for iwarp transports. > Somewhat related, but really a different issue, is that SGEs that > are the target of a read need REMOTE_WRITE access flags on their > STAG for iWARP. That is the clearest explanation for the iWarp difference I've seen so far, thanks! Christoph: The take away from all this is that on iWarp RDMA_READ requires a restricted temporary MR to provide the lkey value in the WC. It cannot use local_dma_lkey. Everything else is the same between IB and iWarp: local_dma_lkey can be used as the lkey for SEND, RECV, WRITE. Jason -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
