RE: [PATCH V3 1/5] RDMA/core: Transport-independent access flags

Hefty, Sean
2015-07-23T18:53:19Z

> 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.
>
> Clear as mud? :)

This may be a nit, but IMO, the use of the term 'rkey' versus 'stag' matters. They convey different ways of finding a data buffer. For example, do you locate a buffer using the stag, then verify that the offset + length fits into the target buffer? Or do you locate the buffer by address, then verify that the key matches?

Consider if we allow an app to specify the rkey/stag, or reference the buffer using an offset, rather than a virtual address.

This seems to be part of the difference between an lkey and an rkey.
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