IB/mlx4: Use multiple WQ blocks to post smaller send WQEs

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>

1 files changed, 4 insertions, 0 deletions

diff --git a/include/linux/mlx4/qp.h b/include/linux/mlx4/qp.h
index 3968b943259a..09a2230923f2 100644
--- a/include/linux/mlx4/qp.h
+++ b/include/linux/mlx4/qp.h
@@ -154,7 +154,11 @@ struct mlx4_qp_context {
 	u32			reserved5[10];
 };
 
+/* Which firmware version adds support for NEC (NoErrorCompletion) bit */
+#define MLX4_FW_VER_WQE_CTRL_NEC mlx4_fw_ver(2, 2, 232)
+
 enum {
+	MLX4_WQE_CTRL_NEC	= 1 << 29,
 	MLX4_WQE_CTRL_FENCE	= 1 << 6,
 	MLX4_WQE_CTRL_CQ_UPDATE	= 3 << 2,
 	MLX4_WQE_CTRL_SOLICITED	= 1 << 1,