[patch v2 26/37] add rxe_req.c

[rpearson-klaOcWyJdxkshyMvu7JE4pqQE7yCjDx5@public.gmane.org]

[-- Attachment #1: add-rxe_req.c --]
[-- Type: text/plain, Size: 19140 bytes --]

QP request logic.

Signed-off-by: Bob Pearson <rpearson-klaOcWyJdxkshyMvu7JE4pqQE7yCjDx5@public.gmane.org>

---
 drivers/infiniband/hw/rxe/rxe_req.c |  711 ++++++++++++++++++++++++++++++++++++
 1 file changed, 711 insertions(+)

Index: infiniband/drivers/infiniband/hw/rxe/rxe_req.c
===================================================================
--- /dev/null
+++ infiniband/drivers/infiniband/hw/rxe/rxe_req.c
@@ -0,0 +1,711 @@
+/*
+ * Copyright (c) 2009-2011 Mellanox Technologies Ltd. All rights reserved.
+ * Copyright (c) 2009-2011 System Fabric Works, Inc. All rights reserved.
+ *
+ * This software is available to you under a choice of one of two
+ * licenses.  You may choose to be licensed under the terms of the GNU
+ * General Public License (GPL) Version 2, available from the file
+ * COPYING in the main directory of this source tree, or the
+ * OpenIB.org BSD license below:
+ *
+ *     Redistribution and use in source and binary forms, with or
+ *     without modification, are permitted provided that the following
+ *     conditions are met:
+ *
+ *	- Redistributions of source code must retain the above
+ *	  copyright notice, this list of conditions and the following
+ *	  disclaimer.
+ *
+ *	- Redistributions in binary form must reproduce the above
+ *	  copyright notice, this list of conditions and the following
+ *	  disclaimer in the documentation and/or other materials
+ *	  provided with the distribution.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+#include <linux/skbuff.h>
+
+#include "rxe.h"
+#include "rxe_loc.h"
+#include "rxe_queue.h"
+
+static int next_opcode(struct rxe_qp *qp, struct rxe_send_wqe *wqe,
+		       unsigned opcode);
+
+static inline void retry_first_write_send(struct rxe_qp *qp,
+					  struct rxe_send_wqe *wqe,
+					  unsigned mask, int npsn)
+{
+	int i;
+
+	for (i = 0; i < npsn; i++) {
+		int to_send = (wqe->dma.resid > qp->mtu) ?
+				qp->mtu : wqe->dma.resid;
+
+		qp->req.opcode = next_opcode(qp, wqe,
+					     wqe->ibwr.opcode);
+
+		if (wqe->ibwr.send_flags & IB_SEND_INLINE) {
+			wqe->dma.resid -= to_send;
+			wqe->dma.sge_offset += to_send;
+		} else
+			advance_dma_data(&wqe->dma, to_send);
+
+		if (mask & WR_WRITE_MASK)
+			wqe->iova += qp->mtu;
+	}
+}
+
+static void req_retry(struct rxe_qp *qp)
+{
+	struct rxe_send_wqe *wqe;
+	unsigned int wqe_index;
+	unsigned int mask;
+	int npsn;
+	int first = 1;
+
+	wqe = queue_head(qp->sq.queue);
+	npsn = (qp->comp.psn - wqe->first_psn) & BTH_PSN_MASK;
+
+	qp->req.wqe_index	= consumer_index(qp->sq.queue);
+	qp->req.psn		= qp->comp.psn;
+	qp->req.opcode		= -1;
+
+	for (wqe_index = consumer_index(qp->sq.queue);
+		wqe_index != producer_index(qp->sq.queue);
+		wqe_index = next_index(qp->sq.queue, wqe_index)) {
+
+		wqe = addr_from_index(qp->sq.queue, wqe_index);
+		mask = wr_opcode_mask(wqe->ibwr.opcode, qp);
+
+		if (wqe->state == wqe_state_posted)
+			break;
+
+		if (wqe->state == wqe_state_done)
+			continue;
+
+		wqe->iova = (mask & WR_ATOMIC_MASK) ?
+			wqe->ibwr.wr.atomic.remote_addr :
+			wqe->ibwr.wr.rdma.remote_addr;
+
+		if (!first || (mask & WR_READ_MASK) == 0) {
+			wqe->dma.resid = wqe->dma.length;
+			wqe->dma.cur_sge = 0;
+			wqe->dma.sge_offset = 0;
+		}
+
+		if (first) {
+			first = 0;
+
+			if (mask & WR_WRITE_OR_SEND_MASK)
+				retry_first_write_send(qp, wqe, mask, npsn);
+
+			if (mask & WR_READ_MASK)
+				wqe->iova += npsn*qp->mtu;
+		}
+
+		wqe->state = wqe_state_posted;
+	}
+}
+
+void rnr_nak_timer(unsigned long data)
+{
+	struct rxe_qp *qp = (struct rxe_qp *)data;
+	pr_debug("rnr nak timer fired\n");
+	rxe_run_task(&qp->req.task, 1);
+}
+
+static struct rxe_send_wqe *req_next_wqe(struct rxe_qp *qp)
+{
+	struct rxe_send_wqe *wqe = queue_head(qp->sq.queue);
+	unsigned long flags;
+
+	if (unlikely(qp->req.state == QP_STATE_DRAIN)) {
+		/* check to see if we are drained;
+		 * state_lock used by requester and completer */
+		spin_lock_irqsave(&qp->state_lock, flags);
+		do {
+			if (qp->req.state != QP_STATE_DRAIN) {
+				/* comp just finished */
+				spin_unlock_irqrestore(&qp->state_lock,
+						       flags);
+				break;
+			}
+
+			if (wqe && ((qp->req.wqe_index !=
+				consumer_index(qp->sq.queue)) ||
+				(wqe->state != wqe_state_posted))) {
+				/* comp not done yet */
+				spin_unlock_irqrestore(&qp->state_lock,
+							   flags);
+				break;
+			}
+
+			qp->req.state = QP_STATE_DRAINED;
+			spin_unlock_irqrestore(&qp->state_lock, flags);
+
+			if (qp->ibqp.event_handler) {
+				struct ib_event ev;
+
+				ev.device = qp->ibqp.device;
+				ev.element.qp = &qp->ibqp;
+				ev.event = IB_EVENT_SQ_DRAINED;
+				qp->ibqp.event_handler(&ev,
+					qp->ibqp.qp_context);
+			}
+		} while (0);
+	}
+
+	if (qp->req.wqe_index == producer_index(qp->sq.queue))
+		return NULL;
+
+	wqe = addr_from_index(qp->sq.queue, qp->req.wqe_index);
+
+	if (qp->req.state == QP_STATE_DRAIN ||
+	    qp->req.state == QP_STATE_DRAINED)
+		if (wqe->state != wqe_state_processing)
+			return NULL;
+
+	if ((wqe->ibwr.send_flags & IB_SEND_FENCE) &&
+	    (qp->req.wqe_index != consumer_index(qp->sq.queue))) {
+		qp->req.wait_fence = 1;
+		return NULL;
+	}
+
+	wqe->mask = wr_opcode_mask(wqe->ibwr.opcode, qp);
+	return wqe;
+}
+
+static int next_opcode_rc(struct rxe_qp *qp, unsigned opcode, int fits)
+{
+	switch (opcode) {
+	case IB_WR_RDMA_WRITE:
+		if (qp->req.opcode == IB_OPCODE_RC_RDMA_WRITE_FIRST ||
+		    qp->req.opcode == IB_OPCODE_RC_RDMA_WRITE_MIDDLE)
+			return fits ?
+				IB_OPCODE_RC_RDMA_WRITE_LAST :
+				IB_OPCODE_RC_RDMA_WRITE_MIDDLE;
+		else
+			return fits ?
+				IB_OPCODE_RC_RDMA_WRITE_ONLY :
+				IB_OPCODE_RC_RDMA_WRITE_FIRST;
+
+	case IB_WR_RDMA_WRITE_WITH_IMM:
+		if (qp->req.opcode == IB_OPCODE_RC_RDMA_WRITE_FIRST ||
+		    qp->req.opcode == IB_OPCODE_RC_RDMA_WRITE_MIDDLE)
+			return fits ?
+				IB_OPCODE_RC_RDMA_WRITE_LAST_WITH_IMMEDIATE :
+				IB_OPCODE_RC_RDMA_WRITE_MIDDLE;
+		else
+			return fits ?
+				IB_OPCODE_RC_RDMA_WRITE_ONLY_WITH_IMMEDIATE :
+				IB_OPCODE_RC_RDMA_WRITE_FIRST;
+
+	case IB_WR_SEND:
+		if (qp->req.opcode == IB_OPCODE_RC_SEND_FIRST ||
+		    qp->req.opcode == IB_OPCODE_RC_SEND_MIDDLE)
+			return fits ?
+				IB_OPCODE_RC_SEND_LAST :
+				IB_OPCODE_RC_SEND_MIDDLE;
+		else
+			return fits ?
+				IB_OPCODE_RC_SEND_ONLY :
+				IB_OPCODE_RC_SEND_FIRST;
+
+	case IB_WR_SEND_WITH_IMM:
+		if (qp->req.opcode == IB_OPCODE_RC_SEND_FIRST ||
+		    qp->req.opcode == IB_OPCODE_RC_SEND_MIDDLE)
+			return fits ?
+				IB_OPCODE_RC_SEND_LAST_WITH_IMMEDIATE :
+				IB_OPCODE_RC_SEND_MIDDLE;
+		else
+			return fits ?
+				IB_OPCODE_RC_SEND_ONLY_WITH_IMMEDIATE :
+				IB_OPCODE_RC_SEND_FIRST;
+
+	case IB_WR_RDMA_READ:
+		return IB_OPCODE_RC_RDMA_READ_REQUEST;
+
+	case IB_WR_ATOMIC_CMP_AND_SWP:
+		return IB_OPCODE_RC_COMPARE_SWAP;
+
+	case IB_WR_ATOMIC_FETCH_AND_ADD:
+		return IB_OPCODE_RC_FETCH_ADD;
+
+	case IB_WR_SEND_WITH_INV:
+		if (qp->req.opcode == IB_OPCODE_RC_SEND_FIRST ||
+		    qp->req.opcode == IB_OPCODE_RC_SEND_MIDDLE)
+			return fits ? IB_OPCODE_RC_SEND_LAST_INV :
+				IB_OPCODE_RC_SEND_MIDDLE;
+		else
+			return fits ? IB_OPCODE_RC_SEND_ONLY_INV :
+				IB_OPCODE_RC_SEND_FIRST;
+	}
+
+	return -EINVAL;
+}
+
+static int next_opcode_uc(struct rxe_qp *qp, unsigned opcode, int fits)
+{
+	switch (opcode) {
+	case IB_WR_RDMA_WRITE:
+		if (qp->req.opcode == IB_OPCODE_UC_RDMA_WRITE_FIRST ||
+		    qp->req.opcode == IB_OPCODE_UC_RDMA_WRITE_MIDDLE)
+			return fits ?
+				IB_OPCODE_UC_RDMA_WRITE_LAST :
+				IB_OPCODE_UC_RDMA_WRITE_MIDDLE;
+		else
+			return fits ?
+				IB_OPCODE_UC_RDMA_WRITE_ONLY :
+				IB_OPCODE_UC_RDMA_WRITE_FIRST;
+
+	case IB_WR_RDMA_WRITE_WITH_IMM:
+		if (qp->req.opcode == IB_OPCODE_UC_RDMA_WRITE_FIRST ||
+		    qp->req.opcode == IB_OPCODE_UC_RDMA_WRITE_MIDDLE)
+			return fits ?
+				IB_OPCODE_UC_RDMA_WRITE_LAST_WITH_IMMEDIATE :
+				IB_OPCODE_UC_RDMA_WRITE_MIDDLE;
+		else
+			return fits ?
+				IB_OPCODE_UC_RDMA_WRITE_ONLY_WITH_IMMEDIATE :
+				IB_OPCODE_UC_RDMA_WRITE_FIRST;
+
+	case IB_WR_SEND:
+		if (qp->req.opcode == IB_OPCODE_UC_SEND_FIRST ||
+		    qp->req.opcode == IB_OPCODE_UC_SEND_MIDDLE)
+			return fits ?
+				IB_OPCODE_UC_SEND_LAST :
+				IB_OPCODE_UC_SEND_MIDDLE;
+		else
+			return fits ?
+				IB_OPCODE_UC_SEND_ONLY :
+				IB_OPCODE_UC_SEND_FIRST;
+
+	case IB_WR_SEND_WITH_IMM:
+		if (qp->req.opcode == IB_OPCODE_UC_SEND_FIRST ||
+		    qp->req.opcode == IB_OPCODE_UC_SEND_MIDDLE)
+			return fits ?
+				IB_OPCODE_UC_SEND_LAST_WITH_IMMEDIATE :
+				IB_OPCODE_UC_SEND_MIDDLE;
+		else
+			return fits ?
+				IB_OPCODE_UC_SEND_ONLY_WITH_IMMEDIATE :
+				IB_OPCODE_UC_SEND_FIRST;
+	}
+
+	return -EINVAL;
+}
+
+static int next_opcode(struct rxe_qp *qp, struct rxe_send_wqe *wqe,
+		       unsigned opcode)
+{
+	int fits = (wqe->dma.resid <= qp->mtu);
+
+	switch (qp_type(qp)) {
+	case IB_QPT_RC:
+		return next_opcode_rc(qp, opcode, fits);
+
+	case IB_QPT_UC:
+		return next_opcode_uc(qp, opcode, fits);
+
+	case IB_QPT_SMI:
+	case IB_QPT_UD:
+	case IB_QPT_GSI:
+		switch (opcode) {
+		case IB_WR_SEND:
+			return IB_OPCODE_UD_SEND_ONLY;
+
+		case IB_WR_SEND_WITH_IMM:
+			return IB_OPCODE_UD_SEND_ONLY_WITH_IMMEDIATE;
+		}
+		break;
+
+	default:
+		break;
+	}
+
+	return -EINVAL;
+}
+
+static inline int check_init_depth(struct rxe_qp *qp, struct rxe_send_wqe *wqe)
+{
+	int depth;
+
+	if (wqe->has_rd_atomic)
+		return 0;
+
+	qp->req.need_rd_atomic = 1;
+	depth = atomic_dec_return(&qp->req.rd_atomic);
+
+	if (depth >= 0) {
+		qp->req.need_rd_atomic = 0;
+		wqe->has_rd_atomic = 1;
+		return 0;
+	} else {
+		atomic_inc(&qp->req.rd_atomic);
+		return -EAGAIN;
+	}
+}
+
+static inline int get_mtu(struct rxe_qp *qp, struct rxe_send_wqe *wqe)
+{
+	struct rxe_dev *rxe = to_rdev(qp->ibqp.device);
+
+	if ((qp_type(qp) == IB_QPT_RC) || (qp_type(qp) == IB_QPT_UC)) {
+		return qp->mtu;
+	} else {
+		struct rxe_av *av = &wqe->av;
+		struct rxe_port *port = &rxe->port[av->attr.port_num - 1];
+		return port->mtu_cap;
+	}
+}
+
+static struct rxe_pkt_info *init_req_packet(struct rxe_qp *qp,
+					    struct rxe_send_wqe *wqe,
+					    int opcode, int payload)
+{
+	struct rxe_dev		*rxe = to_rdev(qp->ibqp.device);
+	struct rxe_port		*port = &rxe->port[qp->attr.port_num - 1];
+	struct rxe_pkt_info	*pkt;
+	struct sk_buff		*skb;
+	struct ib_send_wr	*ibwr = &wqe->ibwr;
+	struct rxe_av		*av;
+	int			pad = (-payload) & 0x3;
+	int			paylen;
+	int			solicited;
+	u16			pkey;
+	u32			qp_num;
+	int			ack_req;
+	unsigned int		lnh;
+	unsigned int		length;
+
+	/* length from start of bth to end of icrc */
+	paylen = rxe_opcode[opcode].length + payload + pad + RXE_ICRC_SIZE;
+
+	/* TODO support APM someday */
+	if (qp_type(qp) == IB_QPT_RC || qp_type(qp) == IB_QPT_UC)
+		av = &qp->pri_av;
+	else
+		av = &wqe->av;
+
+	/* init skb
+	 * ifc layer must set lrh/grh flags */
+	skb = rxe->ifc_ops->init_packet(rxe, av, paylen);
+	if (!skb)
+		return NULL;
+
+	atomic_inc(&qp->req_skb_out);
+	atomic_inc(&rxe->req_skb_out);
+
+	/* pkt->hdr, rxe, port_num, paylen and
+	   mask are initialized in ifc layer */
+	pkt		= SKB_TO_PKT(skb);
+	pkt->opcode	= opcode;
+	pkt->qp		= qp;
+	pkt->psn	= qp->req.psn;
+	pkt->mask	|= rxe_opcode[opcode].mask;
+	pkt->paylen	= paylen;
+	pkt->offset	= 0;
+
+	/* init lrh */
+	if (pkt->mask & RXE_LRH_MASK) {
+		pkt->offset += RXE_LRH_BYTES;
+		lnh = (pkt->mask & RXE_GRH_MASK) ? LRH_LNH_IBA_GBL
+						 : LRH_LNH_IBA_LOC;
+		length = paylen + RXE_LRH_BYTES;
+		if (pkt->mask & RXE_GRH_MASK)
+			length += RXE_GRH_BYTES;
+
+		/* TODO currently we do not implement SL->VL
+		   table so just force VL=SL */
+		lrh_init(pkt, av->attr.sl, av->attr.sl,
+			 lnh, length/4,
+			 av->attr.dlid,
+			 port->attr.lid);
+	}
+
+	/* init grh */
+	if (pkt->mask & RXE_GRH_MASK) {
+		pkt->offset += RXE_GRH_BYTES;
+
+		/* TODO set class flow hopcount */
+		grh_init(pkt, 0, 0, paylen, 0);
+
+		grh_set_sgid(pkt, port->subnet_prefix,
+			     port->guid_tbl[av->attr.grh.sgid_index]);
+		grh_set_dgid(pkt, av->attr.grh.dgid.global.subnet_prefix,
+			     av->attr.grh.dgid.global.interface_id);
+	}
+
+	/* init bth */
+	solicited = (ibwr->send_flags & IB_SEND_SOLICITED) &&
+			(pkt->mask & RXE_END_MASK) &&
+			((pkt->mask & (RXE_SEND_MASK)) ||
+			(pkt->mask & (RXE_WRITE_MASK | RXE_IMMDT_MASK)) ==
+			(RXE_WRITE_MASK | RXE_IMMDT_MASK));
+
+	pkey = (qp_type(qp) == IB_QPT_GSI) ?
+		 port->pkey_tbl[ibwr->wr.ud.pkey_index] :
+		 port->pkey_tbl[qp->attr.pkey_index];
+
+	qp_num = (pkt->mask & RXE_DETH_MASK) ? ibwr->wr.ud.remote_qpn :
+					 qp->attr.dest_qp_num;
+
+	ack_req = ((pkt->mask & RXE_END_MASK) ||
+		(qp->req.noack_pkts++ > rxe_max_pkt_per_ack));
+	if (ack_req)
+		qp->req.noack_pkts = 0;
+
+	bth_init(pkt, pkt->opcode, solicited, 0, pad, pkey, qp_num,
+		 ack_req, pkt->psn);
+
+	/* init optional headers */
+	if (pkt->mask & RXE_RETH_MASK) {
+		reth_set_rkey(pkt, ibwr->wr.rdma.rkey);
+		reth_set_va(pkt, wqe->iova);
+		reth_set_len(pkt, wqe->dma.length);
+	}
+
+	if (pkt->mask & RXE_IMMDT_MASK)
+		immdt_set_imm(pkt, ibwr->ex.imm_data);
+
+	if (pkt->mask & RXE_IETH_MASK)
+		ieth_set_rkey(pkt, ibwr->ex.invalidate_rkey);
+
+	if (pkt->mask & RXE_ATMETH_MASK) {
+		atmeth_set_va(pkt, wqe->iova);
+		if (opcode == IB_OPCODE_RC_COMPARE_SWAP ||
+		    opcode == IB_OPCODE_RD_COMPARE_SWAP) {
+			atmeth_set_swap_add(pkt, ibwr->wr.atomic.swap);
+			atmeth_set_comp(pkt, ibwr->wr.atomic.compare_add);
+		} else {
+			atmeth_set_swap_add(pkt, ibwr->wr.atomic.compare_add);
+		}
+		atmeth_set_rkey(pkt, ibwr->wr.atomic.rkey);
+	}
+
+	if (pkt->mask & RXE_DETH_MASK) {
+		if (qp->ibqp.qp_num == 1)
+			deth_set_qkey(pkt, GSI_QKEY);
+		else
+			deth_set_qkey(pkt, ibwr->wr.ud.remote_qkey);
+		deth_set_sqp(pkt, qp->ibqp.qp_num);
+	}
+
+	return pkt;
+}
+
+static int fill_packet(struct rxe_qp *qp, struct rxe_send_wqe *wqe,
+		       struct rxe_pkt_info *pkt, int payload)
+{
+	struct rxe_dev *rxe = to_rdev(qp->ibqp.device);
+	static const uint8_t zerobuf[4] = {0,};
+	int pad;
+	u32 crc = 0;
+	u8 *p;
+
+	if (!rxe_crc_disable)
+		crc = rxe_icrc_hdr(pkt);
+
+	if (pkt->mask & RXE_WRITE_OR_SEND) {
+		if (wqe->ibwr.send_flags & IB_SEND_INLINE) {
+			p = &wqe->dma.inline_data[wqe->dma.sge_offset];
+
+			if (!rxe_crc_disable)
+				crc = crc32_le(crc, p, payload);
+
+			memcpy(payload_addr(pkt), p, payload);
+
+			wqe->dma.resid -= payload;
+			wqe->dma.sge_offset += payload;
+		} else {
+			if (copy_data(rxe, qp->pd, 0, &wqe->dma,
+				      payload_addr(pkt), payload,
+				      direction_out, !rxe_crc_disable ?
+				      &crc : NULL)) {
+				return -1;
+			}
+		}
+	}
+
+	p = payload_addr(pkt) + payload;
+	pad = (-payload) & 0x3;
+	if (pad) {
+		if (!rxe_crc_disable)
+			crc = crc32_le(crc, zerobuf, pad);
+
+		memcpy(p, zerobuf, pad);
+
+		p += pad;
+	}
+
+	*p = ~crc;
+
+	return 0;
+}
+
+static void update_state(struct rxe_qp *qp, struct rxe_send_wqe *wqe,
+			 struct rxe_pkt_info *pkt, int payload)
+{
+	/* number of packets left to send including current one */
+	int num_pkt = (wqe->dma.resid + payload + qp->mtu - 1) / qp->mtu;
+
+	/* handle zero length packet case */
+	if (num_pkt == 0)
+		num_pkt = 1;
+
+	if (pkt->mask & RXE_START_MASK) {
+		wqe->first_psn = qp->req.psn;
+		wqe->last_psn = (qp->req.psn + num_pkt - 1) & BTH_PSN_MASK;
+	}
+
+	if (pkt->mask & RXE_READ_MASK)
+		qp->req.psn = (wqe->first_psn + num_pkt) & BTH_PSN_MASK;
+	else
+		qp->req.psn = (qp->req.psn + 1) & BTH_PSN_MASK;
+
+	qp->req.opcode = pkt->opcode;
+
+	if (pkt->mask & RXE_END_MASK) {
+		if (qp_type(qp) == IB_QPT_RC)
+			wqe->state = wqe_state_pending;
+		else
+			wqe->state = wqe_state_done;
+
+		qp->req.wqe_index = next_index(qp->sq.queue,
+						qp->req.wqe_index);
+	} else
+		wqe->state = wqe_state_processing;
+
+	if (qp->qp_timeout_jiffies && !timer_pending(&qp->retrans_timer))
+		mod_timer(&qp->retrans_timer,
+			  jiffies + qp->qp_timeout_jiffies);
+}
+
+int rxe_requester(void *arg)
+{
+	struct rxe_qp *qp = (struct rxe_qp *)arg;
+	struct rxe_pkt_info *pkt;
+	struct rxe_send_wqe *wqe;
+	unsigned mask;
+	int payload;
+	int mtu;
+	int opcode;
+
+	if (!qp->valid || qp->req.state == QP_STATE_ERROR)
+		goto exit;
+
+	if (qp->req.state == QP_STATE_RESET) {
+		qp->req.wqe_index = consumer_index(qp->sq.queue);
+		qp->req.opcode = -1;
+		qp->req.need_rd_atomic = 0;
+		qp->req.wait_psn = 0;
+		qp->req.need_retry = 0;
+		goto exit;
+	}
+
+	if (qp->req.need_retry) {
+		req_retry(qp);
+		qp->req.need_retry = 0;
+	}
+
+	wqe = req_next_wqe(qp);
+	if (!wqe)
+		goto exit;
+
+	/* heuristic sliding window algorithm to keep
+	   sender from overrunning receiver queues */
+	if (qp_type(qp) == IB_QPT_RC)  {
+		if (psn_compare(qp->req.psn, qp->comp.psn +
+				rxe_max_req_comp_gap) > 0) {
+			qp->req.wait_psn = 1;
+			goto exit;
+		}
+	}
+
+	/* heuristic algorithm to prevent sender from
+	   overrunning the output queue. to not overrun
+	   the receiver's input queue (UC/UD) requires
+	   rate control or application level flow control */
+	if (atomic_read(&qp->req_skb_out) > rxe_max_skb_per_qp) {
+		qp->need_req_skb = 1;
+		goto exit;
+	}
+
+	opcode = next_opcode(qp, wqe, wqe->ibwr.opcode);
+	if (opcode < 0) {
+		wqe->status = IB_WC_LOC_QP_OP_ERR;
+		/* TODO most be more to do here ?? */
+		goto exit;
+	}
+
+	mask = rxe_opcode[opcode].mask;
+	if (unlikely(mask & RXE_READ_OR_ATOMIC)) {
+		if (check_init_depth(qp, wqe))
+			goto exit;
+	}
+
+	mtu = get_mtu(qp, wqe);
+	payload = (mask & RXE_WRITE_OR_SEND) ? wqe->dma.resid : 0;
+	if (payload > mtu) {
+		if (qp_type(qp) == IB_QPT_UD) {
+			/* believe it or not this is
+			   what the spec says to do */
+			/* TODO handle > 1 ports */
+
+			/*
+			 * fake a successful UD send
+			 */
+			wqe->first_psn = qp->req.psn;
+			wqe->last_psn = qp->req.psn;
+			qp->req.psn = (qp->req.psn + 1) & BTH_PSN_MASK;
+			qp->req.opcode = IB_OPCODE_UD_SEND_ONLY;
+			qp->req.wqe_index = next_index(qp->sq.queue,
+						       qp->req.wqe_index);
+			wqe->state = wqe_state_done;
+			wqe->status = IB_WC_SUCCESS;
+			goto complete;
+		}
+		payload = mtu;
+	}
+
+	pkt = init_req_packet(qp, wqe, opcode, payload);
+	if (!pkt) {
+		qp->need_req_skb = 1;
+		goto exit;
+	}
+
+	if (fill_packet(qp, wqe, pkt, payload)) {
+		wqe->status = IB_WC_LOC_PROT_ERR;
+		wqe->state = wqe_state_error;
+		goto complete;
+	}
+
+	update_state(qp, wqe, pkt, payload);
+
+	arbiter_skb_queue(to_rdev(qp->ibqp.device), qp, PKT_TO_SKB(pkt));
+
+	if (mask & RXE_END_MASK)
+		goto complete;
+	else
+		goto done;
+
+complete:
+	if (qp_type(qp) != IB_QPT_RC) {
+		while (rxe_completer(qp) == 0)
+			;
+	}
+done:
+	return 0;
+
+exit:
+	return -EAGAIN;
+}


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