[openib-general] mthca and DDR not hidden

[Sean Hefty]

On Thu, 30 Sep 2004 16:40:05 -0400
Hal Rosenstock <halr at voltaire.com> wrote:

> On Thu, 2004-09-30 at 16:32, Roland Dreier wrote:
> > Also, the
> > consumer must either create its own MR using that PD, or have access
> > to at least the L_Key for the MAD layer's MR.
> 
> That would be an acceptable solution too: to have the consumer create
> the MR based on the MAD PD. Then the lkey doesn't need exposing but
> exposing and copying the lkey seems simpler to me,

Okay - I think I got it now.  Some more thoughts on the topic:

It seems like having the consumer create the MR would be a more generic solution, but the least efficient.  The idea of exposing MR implies that the user know the access layer implementation in order to get the right virtual address when posting MADs.  (The user must know that the MR applies to all of system memory.)  Giving out only the lkey seems less desirable, since the client must also assume the starting virtual address.

Another alternative is for the access layer to set the lkey value (and adjust the addr if needed) in the SGEs when posting.  This seems somewhat equivalent to the access layer performing the memory registration on the user's behalf...  (not recommending this, just mentioning it)