ConnectX HCA supports shrinking WQEs, so that a single work request
can be made of multiple units of wqe_shift. This way, WRs can differ
in size, and do not have to be a power of 2 in size, saving memory and
speeding up send WR posting. Unfortunately, if we do this then the
wqe_index field in CQEs can't be used to look up the WR ID anymore, so
our implementation does this only if selective signaling is off.
Further, on 32-bit platforms, we can't use vmap() to make the QP
buffer virtually contigious. Thus we have to use constant-sized WRs to
make sure a WR is always fully within a single page-sized chunk.
Finally, we use WRs with the NOP opcode to avoid wrapping around the
queue buffer in the middle of posting a WR, and we set the
NoErrorCompletion bit to avoid getting completions with error for NOP
WRs. However, NEC is only supported starting with firmware 2.2.232,
so we use constant-sized WRs for older firmware. And, since MLX QPs
only support SEND, we use constant-sized WRs in this case.
When stamping during NOP posting, do stamping following setting of the
NOP WQE valid bit.
Signed-off-by: Michael S. Tsirkin <mst@dev.mellanox.co.il>
Signed-off-by: Jack Morgenstein <jackm@dev.mellanox.co.il>
Signed-off-by: Roland Dreier <rolandd@cisco.com>
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