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

[Roland Dreier]

 > I see. Just wondering, in the mlx4 case, is it a must to use dma
 > consistent memory allocation or dma mapping would work too?

dma mapping would work too but then handling the map/unmap becomes an
issue.  I think it is way too complicated too add new verbs for
map/unmap fastreg page list (in addition to the alloc/free fastreg page
list that we are already adding) and force the consumer to do it.  And
if we expect the low-level driver to do it, then the map is easy (can be
done while posting the send) but the unmap is a pain -- it would have to
be done inside poll_cq when reapind the completion, and the low-level
driver would have to keep some complicated extra data structure to go
back from the completion to the original fast reg page list structure.