[ofa-general] [PATCH RFC v3 1/2] RDMA/Core: MEM_MGT_EXTENSIONS support

[Roland Dreier]

 > BTW:  a single capability bit doesn't allow apps to decide at run time
 > whether to use read-with-inv, which is iwarp-only.  Perhaps we need
 > that as its own capbility bit?  Or perhaps we can load detailed
 > support/no support into the query device logic?  What it some devices
 > can only support part of the suite of MEM_MGT_EXTENSIONS?

I think RDMA read with invalidate can be tested for as iWARP vs. IB.
The reason IB doesn't have it is kind of inherent in the IB protocol,
since remote access is not required for the RDMA target.

I think making the capability flags really fine-grained isn't worth
it -- we went too far in that direction historically, and no one checks
any capability flags at all.  It's just complexity.

So any device that supports only part of the IB base memory mgt
extensions (or doesn't support the full IWARP spec) just shouldn't
advertise MEM_MGT_EXTENSIONS I think.  Implementing such a device would
be kind of dumb anyway at this point.

 - R.