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ipath_rc.c

/*
 * Copyright (c) 2006, 2007 QLogic Corporation. All rights reserved.
 * Copyright (c) 2005, 2006 PathScale, 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 "ipath_verbs.h"
#include "ipath_kernel.h"

/* cut down ridiculously long IB macro names */
#define OP(x) IB_OPCODE_RC_##x

static u32 restart_sge(struct ipath_sge_state *ss, struct ipath_swqe *wqe,
                   u32 psn, u32 pmtu)
{
      u32 len;

      len = ((psn - wqe->psn) & IPATH_PSN_MASK) * pmtu;
      ss->sge = wqe->sg_list[0];
      ss->sg_list = wqe->sg_list + 1;
      ss->num_sge = wqe->wr.num_sge;
      ipath_skip_sge(ss, len);
      return wqe->length - len;
}

/**
 * ipath_init_restart- initialize the qp->s_sge after a restart
 * @qp: the QP who's SGE we're restarting
 * @wqe: the work queue to initialize the QP's SGE from
 *
 * The QP s_lock should be held and interrupts disabled.
 */
static void ipath_init_restart(struct ipath_qp *qp, struct ipath_swqe *wqe)
{
      struct ipath_ibdev *dev;

      qp->s_len = restart_sge(&qp->s_sge, wqe, qp->s_psn,
                        ib_mtu_enum_to_int(qp->path_mtu));
      dev = to_idev(qp->ibqp.device);
      spin_lock(&dev->pending_lock);
      if (list_empty(&qp->timerwait))
            list_add_tail(&qp->timerwait,
                        &dev->pending[dev->pending_index]);
      spin_unlock(&dev->pending_lock);
}

/**
 * ipath_make_rc_ack - construct a response packet (ACK, NAK, or RDMA read)
 * @qp: a pointer to the QP
 * @ohdr: a pointer to the IB header being constructed
 * @pmtu: the path MTU
 *
 * Return 1 if constructed; otherwise, return 0.
 * Note that we are in the responder's side of the QP context.
 * Note the QP s_lock must be held.
 */
static int ipath_make_rc_ack(struct ipath_ibdev *dev, struct ipath_qp *qp,
                       struct ipath_other_headers *ohdr, u32 pmtu)
{
      struct ipath_ack_entry *e;
      u32 hwords;
      u32 len;
      u32 bth0;
      u32 bth2;

      /* header size in 32-bit words LRH+BTH = (8+12)/4. */
      hwords = 5;

      switch (qp->s_ack_state) {
      case OP(RDMA_READ_RESPONSE_LAST):
      case OP(RDMA_READ_RESPONSE_ONLY):
      case OP(ATOMIC_ACKNOWLEDGE):
            /*
             * We can increment the tail pointer now that the last
             * response has been sent instead of only being
             * constructed.
             */
            if (++qp->s_tail_ack_queue > IPATH_MAX_RDMA_ATOMIC)
                  qp->s_tail_ack_queue = 0;
            /* FALLTHROUGH */
      case OP(SEND_ONLY):
      case OP(ACKNOWLEDGE):
            /* Check for no next entry in the queue. */
            if (qp->r_head_ack_queue == qp->s_tail_ack_queue) {
                  if (qp->s_flags & IPATH_S_ACK_PENDING)
                        goto normal;
                  qp->s_ack_state = OP(ACKNOWLEDGE);
                  goto bail;
            }

            e = &qp->s_ack_queue[qp->s_tail_ack_queue];
            if (e->opcode == OP(RDMA_READ_REQUEST)) {
                  /* Copy SGE state in case we need to resend */
                  qp->s_ack_rdma_sge = e->rdma_sge;
                  qp->s_cur_sge = &qp->s_ack_rdma_sge;
                  len = e->rdma_sge.sge.sge_length;
                  if (len > pmtu) {
                        len = pmtu;
                        qp->s_ack_state = OP(RDMA_READ_RESPONSE_FIRST);
                  } else {
                        qp->s_ack_state = OP(RDMA_READ_RESPONSE_ONLY);
                        e->sent = 1;
                  }
                  ohdr->u.aeth = ipath_compute_aeth(qp);
                  hwords++;
                  qp->s_ack_rdma_psn = e->psn;
                  bth2 = qp->s_ack_rdma_psn++ & IPATH_PSN_MASK;
            } else {
                  /* COMPARE_SWAP or FETCH_ADD */
                  qp->s_cur_sge = NULL;
                  len = 0;
                  qp->s_ack_state = OP(ATOMIC_ACKNOWLEDGE);
                  ohdr->u.at.aeth = ipath_compute_aeth(qp);
                  ohdr->u.at.atomic_ack_eth[0] =
                        cpu_to_be32(e->atomic_data >> 32);
                  ohdr->u.at.atomic_ack_eth[1] =
                        cpu_to_be32(e->atomic_data);
                  hwords += sizeof(ohdr->u.at) / sizeof(u32);
                  bth2 = e->psn;
                  e->sent = 1;
            }
            bth0 = qp->s_ack_state << 24;
            break;

      case OP(RDMA_READ_RESPONSE_FIRST):
            qp->s_ack_state = OP(RDMA_READ_RESPONSE_MIDDLE);
            /* FALLTHROUGH */
      case OP(RDMA_READ_RESPONSE_MIDDLE):
            len = qp->s_ack_rdma_sge.sge.sge_length;
            if (len > pmtu)
                  len = pmtu;
            else {
                  ohdr->u.aeth = ipath_compute_aeth(qp);
                  hwords++;
                  qp->s_ack_state = OP(RDMA_READ_RESPONSE_LAST);
                  qp->s_ack_queue[qp->s_tail_ack_queue].sent = 1;
            }
            bth0 = qp->s_ack_state << 24;
            bth2 = qp->s_ack_rdma_psn++ & IPATH_PSN_MASK;
            break;

      default:
      normal:
            /*
             * Send a regular ACK.
             * Set the s_ack_state so we wait until after sending
             * the ACK before setting s_ack_state to ACKNOWLEDGE
             * (see above).
             */
            qp->s_ack_state = OP(SEND_ONLY);
            qp->s_flags &= ~IPATH_S_ACK_PENDING;
            qp->s_cur_sge = NULL;
            if (qp->s_nak_state)
                  ohdr->u.aeth =
                        cpu_to_be32((qp->r_msn & IPATH_MSN_MASK) |
                                  (qp->s_nak_state <<
                                   IPATH_AETH_CREDIT_SHIFT));
            else
                  ohdr->u.aeth = ipath_compute_aeth(qp);
            hwords++;
            len = 0;
            bth0 = OP(ACKNOWLEDGE) << 24;
            bth2 = qp->s_ack_psn & IPATH_PSN_MASK;
      }
      qp->s_hdrwords = hwords;
      qp->s_cur_size = len;
      ipath_make_ruc_header(dev, qp, ohdr, bth0, bth2);
      return 1;

bail:
      return 0;
}

/**
 * ipath_make_rc_req - construct a request packet (SEND, RDMA r/w, ATOMIC)
 * @qp: a pointer to the QP
 *
 * Return 1 if constructed; otherwise, return 0.
 */
int ipath_make_rc_req(struct ipath_qp *qp)
{
      struct ipath_ibdev *dev = to_idev(qp->ibqp.device);
      struct ipath_other_headers *ohdr;
      struct ipath_sge_state *ss;
      struct ipath_swqe *wqe;
      u32 hwords;
      u32 len;
      u32 bth0;
      u32 bth2;
      u32 pmtu = ib_mtu_enum_to_int(qp->path_mtu);
      char newreq;
      unsigned long flags;
      int ret = 0;

      ohdr = &qp->s_hdr.u.oth;
      if (qp->remote_ah_attr.ah_flags & IB_AH_GRH)
            ohdr = &qp->s_hdr.u.l.oth;

      /*
       * The lock is needed to synchronize between the sending tasklet,
       * the receive interrupt handler, and timeout resends.
       */
      spin_lock_irqsave(&qp->s_lock, flags);

      /* Sending responses has higher priority over sending requests. */
      if ((qp->r_head_ack_queue != qp->s_tail_ack_queue ||
           (qp->s_flags & IPATH_S_ACK_PENDING) ||
           qp->s_ack_state != OP(ACKNOWLEDGE)) &&
          ipath_make_rc_ack(dev, qp, ohdr, pmtu))
            goto done;

      if (!(ib_ipath_state_ops[qp->state] & IPATH_PROCESS_SEND_OK) ||
          qp->s_rnr_timeout || qp->s_wait_credit)
            goto bail;

      /* Limit the number of packets sent without an ACK. */
      if (ipath_cmp24(qp->s_psn, qp->s_last_psn + IPATH_PSN_CREDIT) > 0) {
            qp->s_wait_credit = 1;
            dev->n_rc_stalls++;
            goto bail;
      }

      /* header size in 32-bit words LRH+BTH = (8+12)/4. */
      hwords = 5;
      bth0 = 1 << 22; /* Set M bit */

      /* Send a request. */
      wqe = get_swqe_ptr(qp, qp->s_cur);
      switch (qp->s_state) {
      default:
            /*
             * Resend an old request or start a new one.
             *
             * We keep track of the current SWQE so that
             * we don't reset the "furthest progress" state
             * if we need to back up.
             */
            newreq = 0;
            if (qp->s_cur == qp->s_tail) {
                  /* Check if send work queue is empty. */
                  if (qp->s_tail == qp->s_head)
                        goto bail;
                  /*
                   * If a fence is requested, wait for previous
                   * RDMA read and atomic operations to finish.
                   */
                  if ((wqe->wr.send_flags & IB_SEND_FENCE) &&
                      qp->s_num_rd_atomic) {
                        qp->s_flags |= IPATH_S_FENCE_PENDING;
                        goto bail;
                  }
                  wqe->psn = qp->s_next_psn;
                  newreq = 1;
            }
            /*
             * Note that we have to be careful not to modify the
             * original work request since we may need to resend
             * it.
             */
            len = wqe->length;
            ss = &qp->s_sge;
            bth2 = 0;
            switch (wqe->wr.opcode) {
            case IB_WR_SEND:
            case IB_WR_SEND_WITH_IMM:
                  /* If no credit, return. */
                  if (qp->s_lsn != (u32) -1 &&
                      ipath_cmp24(wqe->ssn, qp->s_lsn + 1) > 0)
                        goto bail;
                  wqe->lpsn = wqe->psn;
                  if (len > pmtu) {
                        wqe->lpsn += (len - 1) / pmtu;
                        qp->s_state = OP(SEND_FIRST);
                        len = pmtu;
                        break;
                  }
                  if (wqe->wr.opcode == IB_WR_SEND)
                        qp->s_state = OP(SEND_ONLY);
                  else {
                        qp->s_state = OP(SEND_ONLY_WITH_IMMEDIATE);
                        /* Immediate data comes after the BTH */
                        ohdr->u.imm_data = wqe->wr.imm_data;
                        hwords += 1;
                  }
                  if (wqe->wr.send_flags & IB_SEND_SOLICITED)
                        bth0 |= 1 << 23;
                  bth2 = 1 << 31;   /* Request ACK. */
                  if (++qp->s_cur == qp->s_size)
                        qp->s_cur = 0;
                  break;

            case IB_WR_RDMA_WRITE:
                  if (newreq && qp->s_lsn != (u32) -1)
                        qp->s_lsn++;
                  /* FALLTHROUGH */
            case IB_WR_RDMA_WRITE_WITH_IMM:
                  /* If no credit, return. */
                  if (qp->s_lsn != (u32) -1 &&
                      ipath_cmp24(wqe->ssn, qp->s_lsn + 1) > 0)
                        goto bail;
                  ohdr->u.rc.reth.vaddr =
                        cpu_to_be64(wqe->wr.wr.rdma.remote_addr);
                  ohdr->u.rc.reth.rkey =
                        cpu_to_be32(wqe->wr.wr.rdma.rkey);
                  ohdr->u.rc.reth.length = cpu_to_be32(len);
                  hwords += sizeof(struct ib_reth) / sizeof(u32);
                  wqe->lpsn = wqe->psn;
                  if (len > pmtu) {
                        wqe->lpsn += (len - 1) / pmtu;
                        qp->s_state = OP(RDMA_WRITE_FIRST);
                        len = pmtu;
                        break;
                  }
                  if (wqe->wr.opcode == IB_WR_RDMA_WRITE)
                        qp->s_state = OP(RDMA_WRITE_ONLY);
                  else {
                        qp->s_state =
                              OP(RDMA_WRITE_ONLY_WITH_IMMEDIATE);
                        /* Immediate data comes after RETH */
                        ohdr->u.rc.imm_data = wqe->wr.imm_data;
                        hwords += 1;
                        if (wqe->wr.send_flags & IB_SEND_SOLICITED)
                              bth0 |= 1 << 23;
                  }
                  bth2 = 1 << 31;   /* Request ACK. */
                  if (++qp->s_cur == qp->s_size)
                        qp->s_cur = 0;
                  break;

            case IB_WR_RDMA_READ:
                  /*
                   * Don't allow more operations to be started
                   * than the QP limits allow.
                   */
                  if (newreq) {
                        if (qp->s_num_rd_atomic >=
                            qp->s_max_rd_atomic) {
                              qp->s_flags |= IPATH_S_RDMAR_PENDING;
                              goto bail;
                        }
                        qp->s_num_rd_atomic++;
                        if (qp->s_lsn != (u32) -1)
                              qp->s_lsn++;
                        /*
                         * Adjust s_next_psn to count the
                         * expected number of responses.
                         */
                        if (len > pmtu)
                              qp->s_next_psn += (len - 1) / pmtu;
                        wqe->lpsn = qp->s_next_psn++;
                  }
                  ohdr->u.rc.reth.vaddr =
                        cpu_to_be64(wqe->wr.wr.rdma.remote_addr);
                  ohdr->u.rc.reth.rkey =
                        cpu_to_be32(wqe->wr.wr.rdma.rkey);
                  ohdr->u.rc.reth.length = cpu_to_be32(len);
                  qp->s_state = OP(RDMA_READ_REQUEST);
                  hwords += sizeof(ohdr->u.rc.reth) / sizeof(u32);
                  ss = NULL;
                  len = 0;
                  if (++qp->s_cur == qp->s_size)
                        qp->s_cur = 0;
                  break;

            case IB_WR_ATOMIC_CMP_AND_SWP:
            case IB_WR_ATOMIC_FETCH_AND_ADD:
                  /*
                   * Don't allow more operations to be started
                   * than the QP limits allow.
                   */
                  if (newreq) {
                        if (qp->s_num_rd_atomic >=
                            qp->s_max_rd_atomic) {
                              qp->s_flags |= IPATH_S_RDMAR_PENDING;
                              goto bail;
                        }
                        qp->s_num_rd_atomic++;
                        if (qp->s_lsn != (u32) -1)
                              qp->s_lsn++;
                        wqe->lpsn = wqe->psn;
                  }
                  if (wqe->wr.opcode == IB_WR_ATOMIC_CMP_AND_SWP) {
                        qp->s_state = OP(COMPARE_SWAP);
                        ohdr->u.atomic_eth.swap_data = cpu_to_be64(
                              wqe->wr.wr.atomic.swap);
                        ohdr->u.atomic_eth.compare_data = cpu_to_be64(
                              wqe->wr.wr.atomic.compare_add);
                  } else {
                        qp->s_state = OP(FETCH_ADD);
                        ohdr->u.atomic_eth.swap_data = cpu_to_be64(
                              wqe->wr.wr.atomic.compare_add);
                        ohdr->u.atomic_eth.compare_data = 0;
                  }
                  ohdr->u.atomic_eth.vaddr[0] = cpu_to_be32(
                        wqe->wr.wr.atomic.remote_addr >> 32);
                  ohdr->u.atomic_eth.vaddr[1] = cpu_to_be32(
                        wqe->wr.wr.atomic.remote_addr);
                  ohdr->u.atomic_eth.rkey = cpu_to_be32(
                        wqe->wr.wr.atomic.rkey);
                  hwords += sizeof(struct ib_atomic_eth) / sizeof(u32);
                  ss = NULL;
                  len = 0;
                  if (++qp->s_cur == qp->s_size)
                        qp->s_cur = 0;
                  break;

            default:
                  goto bail;
            }
            qp->s_sge.sge = wqe->sg_list[0];
            qp->s_sge.sg_list = wqe->sg_list + 1;
            qp->s_sge.num_sge = wqe->wr.num_sge;
            qp->s_len = wqe->length;
            if (newreq) {
                  qp->s_tail++;
                  if (qp->s_tail >= qp->s_size)
                        qp->s_tail = 0;
            }
            bth2 |= qp->s_psn & IPATH_PSN_MASK;
            if (wqe->wr.opcode == IB_WR_RDMA_READ)
                  qp->s_psn = wqe->lpsn + 1;
            else {
                  qp->s_psn++;
                  if (ipath_cmp24(qp->s_psn, qp->s_next_psn) > 0)
                        qp->s_next_psn = qp->s_psn;
            }
            /*
             * Put the QP on the pending list so lost ACKs will cause
             * a retry.  More than one request can be pending so the
             * QP may already be on the dev->pending list.
             */
            spin_lock(&dev->pending_lock);
            if (list_empty(&qp->timerwait))
                  list_add_tail(&qp->timerwait,
                              &dev->pending[dev->pending_index]);
            spin_unlock(&dev->pending_lock);
            break;

      case OP(RDMA_READ_RESPONSE_FIRST):
            /*
             * This case can only happen if a send is restarted.
             * See ipath_restart_rc().
             */
            ipath_init_restart(qp, wqe);
            /* FALLTHROUGH */
      case OP(SEND_FIRST):
            qp->s_state = OP(SEND_MIDDLE);
            /* FALLTHROUGH */
      case OP(SEND_MIDDLE):
            bth2 = qp->s_psn++ & IPATH_PSN_MASK;
            if (ipath_cmp24(qp->s_psn, qp->s_next_psn) > 0)
                  qp->s_next_psn = qp->s_psn;
            ss = &qp->s_sge;
            len = qp->s_len;
            if (len > pmtu) {
                  len = pmtu;
                  break;
            }
            if (wqe->wr.opcode == IB_WR_SEND)
                  qp->s_state = OP(SEND_LAST);
            else {
                  qp->s_state = OP(SEND_LAST_WITH_IMMEDIATE);
                  /* Immediate data comes after the BTH */
                  ohdr->u.imm_data = wqe->wr.imm_data;
                  hwords += 1;
            }
            if (wqe->wr.send_flags & IB_SEND_SOLICITED)
                  bth0 |= 1 << 23;
            bth2 |= 1 << 31;  /* Request ACK. */
            qp->s_cur++;
            if (qp->s_cur >= qp->s_size)
                  qp->s_cur = 0;
            break;

      case OP(RDMA_READ_RESPONSE_LAST):
            /*
             * This case can only happen if a RDMA write is restarted.
             * See ipath_restart_rc().
             */
            ipath_init_restart(qp, wqe);
            /* FALLTHROUGH */
      case OP(RDMA_WRITE_FIRST):
            qp->s_state = OP(RDMA_WRITE_MIDDLE);
            /* FALLTHROUGH */
      case OP(RDMA_WRITE_MIDDLE):
            bth2 = qp->s_psn++ & IPATH_PSN_MASK;
            if (ipath_cmp24(qp->s_psn, qp->s_next_psn) > 0)
                  qp->s_next_psn = qp->s_psn;
            ss = &qp->s_sge;
            len = qp->s_len;
            if (len > pmtu) {
                  len = pmtu;
                  break;
            }
            if (wqe->wr.opcode == IB_WR_RDMA_WRITE)
                  qp->s_state = OP(RDMA_WRITE_LAST);
            else {
                  qp->s_state = OP(RDMA_WRITE_LAST_WITH_IMMEDIATE);
                  /* Immediate data comes after the BTH */
                  ohdr->u.imm_data = wqe->wr.imm_data;
                  hwords += 1;
                  if (wqe->wr.send_flags & IB_SEND_SOLICITED)
                        bth0 |= 1 << 23;
            }
            bth2 |= 1 << 31;  /* Request ACK. */
            qp->s_cur++;
            if (qp->s_cur >= qp->s_size)
                  qp->s_cur = 0;
            break;

      case OP(RDMA_READ_RESPONSE_MIDDLE):
            /*
             * This case can only happen if a RDMA read is restarted.
             * See ipath_restart_rc().
             */
            ipath_init_restart(qp, wqe);
            len = ((qp->s_psn - wqe->psn) & IPATH_PSN_MASK) * pmtu;
            ohdr->u.rc.reth.vaddr =
                  cpu_to_be64(wqe->wr.wr.rdma.remote_addr + len);
            ohdr->u.rc.reth.rkey =
                  cpu_to_be32(wqe->wr.wr.rdma.rkey);
            ohdr->u.rc.reth.length = cpu_to_be32(qp->s_len);
            qp->s_state = OP(RDMA_READ_REQUEST);
            hwords += sizeof(ohdr->u.rc.reth) / sizeof(u32);
            bth2 = qp->s_psn++ & IPATH_PSN_MASK;
            if (ipath_cmp24(qp->s_psn, qp->s_next_psn) > 0)
                  qp->s_next_psn = qp->s_psn;
            ss = NULL;
            len = 0;
            qp->s_cur++;
            if (qp->s_cur == qp->s_size)
                  qp->s_cur = 0;
            break;
      }
      if (ipath_cmp24(qp->s_psn, qp->s_last_psn + IPATH_PSN_CREDIT - 1) >= 0)
            bth2 |= 1 << 31;  /* Request ACK. */
      qp->s_len -= len;
      qp->s_hdrwords = hwords;
      qp->s_cur_sge = ss;
      qp->s_cur_size = len;
      ipath_make_ruc_header(dev, qp, ohdr, bth0 | (qp->s_state << 24), bth2);
done:
      ret = 1;
bail:
      spin_unlock_irqrestore(&qp->s_lock, flags);
      return ret;
}

/**
 * send_rc_ack - Construct an ACK packet and send it
 * @qp: a pointer to the QP
 *
 * This is called from ipath_rc_rcv() and only uses the receive
 * side QP state.
 * Note that RDMA reads and atomics are handled in the
 * send side QP state and tasklet.
 */
static void send_rc_ack(struct ipath_qp *qp)
{
      struct ipath_ibdev *dev = to_idev(qp->ibqp.device);
      u16 lrh0;
      u32 bth0;
      u32 hwords;
      struct ipath_ib_header hdr;
      struct ipath_other_headers *ohdr;
      unsigned long flags;

      /* Don't send ACK or NAK if a RDMA read or atomic is pending. */
      if (qp->r_head_ack_queue != qp->s_tail_ack_queue ||
          (qp->s_flags & IPATH_S_ACK_PENDING) ||
          qp->s_ack_state != OP(ACKNOWLEDGE))
            goto queue_ack;

      /* Construct the header. */
      ohdr = &hdr.u.oth;
      lrh0 = IPATH_LRH_BTH;
      /* header size in 32-bit words LRH+BTH+AETH = (8+12+4)/4. */
      hwords = 6;
      if (unlikely(qp->remote_ah_attr.ah_flags & IB_AH_GRH)) {
            hwords += ipath_make_grh(dev, &hdr.u.l.grh,
                               &qp->remote_ah_attr.grh,
                               hwords, 0);
            ohdr = &hdr.u.l.oth;
            lrh0 = IPATH_LRH_GRH;
      }
      /* read pkey_index w/o lock (its atomic) */
      bth0 = ipath_get_pkey(dev->dd, qp->s_pkey_index) |
            (OP(ACKNOWLEDGE) << 24) | (1 << 22);
      if (qp->r_nak_state)
            ohdr->u.aeth = cpu_to_be32((qp->r_msn & IPATH_MSN_MASK) |
                                  (qp->r_nak_state <<
                                   IPATH_AETH_CREDIT_SHIFT));
      else
            ohdr->u.aeth = ipath_compute_aeth(qp);
      lrh0 |= qp->remote_ah_attr.sl << 4;
      hdr.lrh[0] = cpu_to_be16(lrh0);
      hdr.lrh[1] = cpu_to_be16(qp->remote_ah_attr.dlid);
      hdr.lrh[2] = cpu_to_be16(hwords + SIZE_OF_CRC);
      hdr.lrh[3] = cpu_to_be16(dev->dd->ipath_lid);
      ohdr->bth[0] = cpu_to_be32(bth0);
      ohdr->bth[1] = cpu_to_be32(qp->remote_qpn);
      ohdr->bth[2] = cpu_to_be32(qp->r_ack_psn & IPATH_PSN_MASK);

      /*
       * If we can send the ACK, clear the ACK state.
       */
      if (ipath_verbs_send(qp, &hdr, hwords, NULL, 0) == 0) {
            dev->n_unicast_xmit++;
            goto done;
      }

      /*
       * We are out of PIO buffers at the moment.
       * Pass responsibility for sending the ACK to the
       * send tasklet so that when a PIO buffer becomes
       * available, the ACK is sent ahead of other outgoing
       * packets.
       */
      dev->n_rc_qacks++;

queue_ack:
      spin_lock_irqsave(&qp->s_lock, flags);
      qp->s_flags |= IPATH_S_ACK_PENDING;
      qp->s_nak_state = qp->r_nak_state;
      qp->s_ack_psn = qp->r_ack_psn;
      spin_unlock_irqrestore(&qp->s_lock, flags);

      /* Call ipath_do_rc_send() in another thread. */
      tasklet_hi_schedule(&qp->s_task);

done:
      return;
}

/**
 * reset_psn - reset the QP state to send starting from PSN
 * @qp: the QP
 * @psn: the packet sequence number to restart at
 *
 * This is called from ipath_rc_rcv() to process an incoming RC ACK
 * for the given QP.
 * Called at interrupt level with the QP s_lock held.
 */
static void reset_psn(struct ipath_qp *qp, u32 psn)
{
      u32 n = qp->s_last;
      struct ipath_swqe *wqe = get_swqe_ptr(qp, n);
      u32 opcode;

      qp->s_cur = n;

      /*
       * If we are starting the request from the beginning,
       * let the normal send code handle initialization.
       */
      if (ipath_cmp24(psn, wqe->psn) <= 0) {
            qp->s_state = OP(SEND_LAST);
            goto done;
      }

      /* Find the work request opcode corresponding to the given PSN. */
      opcode = wqe->wr.opcode;
      for (;;) {
            int diff;

            if (++n == qp->s_size)
                  n = 0;
            if (n == qp->s_tail)
                  break;
            wqe = get_swqe_ptr(qp, n);
            diff = ipath_cmp24(psn, wqe->psn);
            if (diff < 0)
                  break;
            qp->s_cur = n;
            /*
             * If we are starting the request from the beginning,
             * let the normal send code handle initialization.
             */
            if (diff == 0) {
                  qp->s_state = OP(SEND_LAST);
                  goto done;
            }
            opcode = wqe->wr.opcode;
      }

      /*
       * Set the state to restart in the middle of a request.
       * Don't change the s_sge, s_cur_sge, or s_cur_size.
       * See ipath_do_rc_send().
       */
      switch (opcode) {
      case IB_WR_SEND:
      case IB_WR_SEND_WITH_IMM:
            qp->s_state = OP(RDMA_READ_RESPONSE_FIRST);
            break;

      case IB_WR_RDMA_WRITE:
      case IB_WR_RDMA_WRITE_WITH_IMM:
            qp->s_state = OP(RDMA_READ_RESPONSE_LAST);
            break;

      case IB_WR_RDMA_READ:
            qp->s_state = OP(RDMA_READ_RESPONSE_MIDDLE);
            break;

      default:
            /*
             * This case shouldn't happen since its only
             * one PSN per req.
             */
            qp->s_state = OP(SEND_LAST);
      }
done:
      qp->s_psn = psn;
}

/**
 * ipath_restart_rc - back up requester to resend the last un-ACKed request
 * @qp: the QP to restart
 * @psn: packet sequence number for the request
 * @wc: the work completion request
 *
 * The QP s_lock should be held and interrupts disabled.
 */
void ipath_restart_rc(struct ipath_qp *qp, u32 psn, struct ib_wc *wc)
{
      struct ipath_swqe *wqe = get_swqe_ptr(qp, qp->s_last);
      struct ipath_ibdev *dev;

      if (qp->s_retry == 0) {
            wc->wr_id = wqe->wr.wr_id;
            wc->status = IB_WC_RETRY_EXC_ERR;
            wc->opcode = ib_ipath_wc_opcode[wqe->wr.opcode];
            wc->vendor_err = 0;
            wc->byte_len = 0;
            wc->qp = &qp->ibqp;
            wc->imm_data = 0;
            wc->src_qp = qp->remote_qpn;
            wc->wc_flags = 0;
            wc->pkey_index = 0;
            wc->slid = qp->remote_ah_attr.dlid;
            wc->sl = qp->remote_ah_attr.sl;
            wc->dlid_path_bits = 0;
            wc->port_num = 0;
            ipath_sqerror_qp(qp, wc);
            goto bail;
      }
      qp->s_retry--;

      /*
       * Remove the QP from the timeout queue.
       * Note: it may already have been removed by ipath_ib_timer().
       */
      dev = to_idev(qp->ibqp.device);
      spin_lock(&dev->pending_lock);
      if (!list_empty(&qp->timerwait))
            list_del_init(&qp->timerwait);
      spin_unlock(&dev->pending_lock);

      if (wqe->wr.opcode == IB_WR_RDMA_READ)
            dev->n_rc_resends++;
      else
            dev->n_rc_resends += (qp->s_psn - psn) & IPATH_PSN_MASK;

      reset_psn(qp, psn);
      tasklet_hi_schedule(&qp->s_task);

bail:
      return;
}

static inline void update_last_psn(struct ipath_qp *qp, u32 psn)
{
      if (qp->s_wait_credit) {
            qp->s_wait_credit = 0;
            tasklet_hi_schedule(&qp->s_task);
      }
      qp->s_last_psn = psn;
}

/**
 * do_rc_ack - process an incoming RC ACK
 * @qp: the QP the ACK came in on
 * @psn: the packet sequence number of the ACK
 * @opcode: the opcode of the request that resulted in the ACK
 *
 * This is called from ipath_rc_rcv_resp() to process an incoming RC ACK
 * for the given QP.
 * Called at interrupt level with the QP s_lock held and interrupts disabled.
 * Returns 1 if OK, 0 if current operation should be aborted (NAK).
 */
static int do_rc_ack(struct ipath_qp *qp, u32 aeth, u32 psn, int opcode,
                 u64 val)
{
      struct ipath_ibdev *dev = to_idev(qp->ibqp.device);
      struct ib_wc wc;
      struct ipath_swqe *wqe;
      int ret = 0;
      u32 ack_psn;
      int diff;

      /*
       * Remove the QP from the timeout queue (or RNR timeout queue).
       * If ipath_ib_timer() has already removed it,
       * it's OK since we hold the QP s_lock and ipath_restart_rc()
       * just won't find anything to restart if we ACK everything.
       */
      spin_lock(&dev->pending_lock);
      if (!list_empty(&qp->timerwait))
            list_del_init(&qp->timerwait);
      spin_unlock(&dev->pending_lock);

      /*
       * Note that NAKs implicitly ACK outstanding SEND and RDMA write
       * requests and implicitly NAK RDMA read and atomic requests issued
       * before the NAK'ed request.  The MSN won't include the NAK'ed
       * request but will include an ACK'ed request(s).
       */
      ack_psn = psn;
      if (aeth >> 29)
            ack_psn--;
      wqe = get_swqe_ptr(qp, qp->s_last);

      /*
       * The MSN might be for a later WQE than the PSN indicates so
       * only complete WQEs that the PSN finishes.
       */
      while ((diff = ipath_cmp24(ack_psn, wqe->lpsn)) >= 0) {
            /*
             * RDMA_READ_RESPONSE_ONLY is a special case since
             * we want to generate completion events for everything
             * before the RDMA read, copy the data, then generate
             * the completion for the read.
             */
            if (wqe->wr.opcode == IB_WR_RDMA_READ &&
                opcode == OP(RDMA_READ_RESPONSE_ONLY) &&
                diff == 0) {
                  ret = 1;
                  goto bail;
            }
            /*
             * If this request is a RDMA read or atomic, and the ACK is
             * for a later operation, this ACK NAKs the RDMA read or
             * atomic.  In other words, only a RDMA_READ_LAST or ONLY
             * can ACK a RDMA read and likewise for atomic ops.  Note
             * that the NAK case can only happen if relaxed ordering is
             * used and requests are sent after an RDMA read or atomic
             * is sent but before the response is received.
             */
            if ((wqe->wr.opcode == IB_WR_RDMA_READ &&
                 (opcode != OP(RDMA_READ_RESPONSE_LAST) || diff != 0)) ||
                ((wqe->wr.opcode == IB_WR_ATOMIC_CMP_AND_SWP ||
                  wqe->wr.opcode == IB_WR_ATOMIC_FETCH_AND_ADD) &&
                 (opcode != OP(ATOMIC_ACKNOWLEDGE) || diff != 0))) {
                  /*
                   * The last valid PSN seen is the previous
                   * request's.
                   */
                  update_last_psn(qp, wqe->psn - 1);
                  /* Retry this request. */
                  ipath_restart_rc(qp, wqe->psn, &wc);
                  /*
                   * No need to process the ACK/NAK since we are
                   * restarting an earlier request.
                   */
                  goto bail;
            }
            if (wqe->wr.opcode == IB_WR_ATOMIC_CMP_AND_SWP ||
                wqe->wr.opcode == IB_WR_ATOMIC_FETCH_AND_ADD)
                  *(u64 *) wqe->sg_list[0].vaddr = val;
            if (qp->s_num_rd_atomic &&
                (wqe->wr.opcode == IB_WR_RDMA_READ ||
                 wqe->wr.opcode == IB_WR_ATOMIC_CMP_AND_SWP ||
                 wqe->wr.opcode == IB_WR_ATOMIC_FETCH_AND_ADD)) {
                  qp->s_num_rd_atomic--;
                  /* Restart sending task if fence is complete */
                  if ((qp->s_flags & IPATH_S_FENCE_PENDING) &&
                      !qp->s_num_rd_atomic) {
                        qp->s_flags &= ~IPATH_S_FENCE_PENDING;
                        tasklet_hi_schedule(&qp->s_task);
                  } else if (qp->s_flags & IPATH_S_RDMAR_PENDING) {
                        qp->s_flags &= ~IPATH_S_RDMAR_PENDING;
                        tasklet_hi_schedule(&qp->s_task);
                  }
            }
            /* Post a send completion queue entry if requested. */
            if (!(qp->s_flags & IPATH_S_SIGNAL_REQ_WR) ||
                (wqe->wr.send_flags & IB_SEND_SIGNALED)) {
                  wc.wr_id = wqe->wr.wr_id;
                  wc.status = IB_WC_SUCCESS;
                  wc.opcode = ib_ipath_wc_opcode[wqe->wr.opcode];
                  wc.vendor_err = 0;
                  wc.byte_len = wqe->length;
                  wc.imm_data = 0;
                  wc.qp = &qp->ibqp;
                  wc.src_qp = qp->remote_qpn;
                  wc.wc_flags = 0;
                  wc.pkey_index = 0;
                  wc.slid = qp->remote_ah_attr.dlid;
                  wc.sl = qp->remote_ah_attr.sl;
                  wc.dlid_path_bits = 0;
                  wc.port_num = 0;
                  ipath_cq_enter(to_icq(qp->ibqp.send_cq), &wc, 0);
            }
            qp->s_retry = qp->s_retry_cnt;
            /*
             * If we are completing a request which is in the process of
             * being resent, we can stop resending it since we know the
             * responder has already seen it.
             */
            if (qp->s_last == qp->s_cur) {
                  if (++qp->s_cur >= qp->s_size)
                        qp->s_cur = 0;
                  qp->s_last = qp->s_cur;
                  if (qp->s_last == qp->s_tail)
                        break;
                  wqe = get_swqe_ptr(qp, qp->s_cur);
                  qp->s_state = OP(SEND_LAST);
                  qp->s_psn = wqe->psn;
            } else {
                  if (++qp->s_last >= qp->s_size)
                        qp->s_last = 0;
                  if (qp->s_last == qp->s_tail)
                        break;
                  wqe = get_swqe_ptr(qp, qp->s_last);
            }
      }

      switch (aeth >> 29) {
      case 0:           /* ACK */
            dev->n_rc_acks++;
            /* If this is a partial ACK, reset the retransmit timer. */
            if (qp->s_last != qp->s_tail) {
                  spin_lock(&dev->pending_lock);
                  if (list_empty(&qp->timerwait))
                        list_add_tail(&qp->timerwait,
                              &dev->pending[dev->pending_index]);
                  spin_unlock(&dev->pending_lock);
                  /*
                   * If we get a partial ACK for a resent operation,
                   * we can stop resending the earlier packets and
                   * continue with the next packet the receiver wants.
                   */
                  if (ipath_cmp24(qp->s_psn, psn) <= 0) {
                        reset_psn(qp, psn + 1);
                        tasklet_hi_schedule(&qp->s_task);
                  }
            } else if (ipath_cmp24(qp->s_psn, psn) <= 0) {
                  qp->s_state = OP(SEND_LAST);
                  qp->s_psn = psn + 1;
            }
            ipath_get_credit(qp, aeth);
            qp->s_rnr_retry = qp->s_rnr_retry_cnt;
            qp->s_retry = qp->s_retry_cnt;
            update_last_psn(qp, psn);
            ret = 1;
            goto bail;

      case 1:           /* RNR NAK */
            dev->n_rnr_naks++;
            if (qp->s_last == qp->s_tail)
                  goto bail;
            if (qp->s_rnr_retry == 0) {
                  wc.status = IB_WC_RNR_RETRY_EXC_ERR;
                  goto class_b;
            }
            if (qp->s_rnr_retry_cnt < 7)
                  qp->s_rnr_retry--;

            /* The last valid PSN is the previous PSN. */
            update_last_psn(qp, psn - 1);

            if (wqe->wr.opcode == IB_WR_RDMA_READ)
                  dev->n_rc_resends++;
            else
                  dev->n_rc_resends +=
                        (qp->s_psn - psn) & IPATH_PSN_MASK;

            reset_psn(qp, psn);

            qp->s_rnr_timeout =
                  ib_ipath_rnr_table[(aeth >> IPATH_AETH_CREDIT_SHIFT) &
                                 IPATH_AETH_CREDIT_MASK];
            ipath_insert_rnr_queue(qp);
            goto bail;

      case 3:           /* NAK */
            if (qp->s_last == qp->s_tail)
                  goto bail;
            /* The last valid PSN is the previous PSN. */
            update_last_psn(qp, psn - 1);
            switch ((aeth >> IPATH_AETH_CREDIT_SHIFT) &
                  IPATH_AETH_CREDIT_MASK) {
            case 0:     /* PSN sequence error */
                  dev->n_seq_naks++;
                  /*
                   * Back up to the responder's expected PSN.
                   * Note that we might get a NAK in the middle of an
                   * RDMA READ response which terminates the RDMA
                   * READ.
                   */
                  ipath_restart_rc(qp, psn, &wc);
                  break;

            case 1:     /* Invalid Request */
                  wc.status = IB_WC_REM_INV_REQ_ERR;
                  dev->n_other_naks++;
                  goto class_b;

            case 2:     /* Remote Access Error */
                  wc.status = IB_WC_REM_ACCESS_ERR;
                  dev->n_other_naks++;
                  goto class_b;

            case 3:     /* Remote Operation Error */
                  wc.status = IB_WC_REM_OP_ERR;
                  dev->n_other_naks++;
            class_b:
                  wc.wr_id = wqe->wr.wr_id;
                  wc.opcode = ib_ipath_wc_opcode[wqe->wr.opcode];
                  wc.vendor_err = 0;
                  wc.byte_len = 0;
                  wc.qp = &qp->ibqp;
                  wc.imm_data = 0;
                  wc.src_qp = qp->remote_qpn;
                  wc.wc_flags = 0;
                  wc.pkey_index = 0;
                  wc.slid = qp->remote_ah_attr.dlid;
                  wc.sl = qp->remote_ah_attr.sl;
                  wc.dlid_path_bits = 0;
                  wc.port_num = 0;
                  ipath_sqerror_qp(qp, &wc);
                  break;

            default:
                  /* Ignore other reserved NAK error codes */
                  goto reserved;
            }
            qp->s_rnr_retry = qp->s_rnr_retry_cnt;
            goto bail;

      default:          /* 2: reserved */
      reserved:
            /* Ignore reserved NAK codes. */
            goto bail;
      }

bail:
      return ret;
}

/**
 * ipath_rc_rcv_resp - process an incoming RC response packet
 * @dev: the device this packet came in on
 * @ohdr: the other headers for this packet
 * @data: the packet data
 * @tlen: the packet length
 * @qp: the QP for this packet
 * @opcode: the opcode for this packet
 * @psn: the packet sequence number for this packet
 * @hdrsize: the header length
 * @pmtu: the path MTU
 * @header_in_data: true if part of the header data is in the data buffer
 *
 * This is called from ipath_rc_rcv() to process an incoming RC response
 * packet for the given QP.
 * Called at interrupt level.
 */
static inline void ipath_rc_rcv_resp(struct ipath_ibdev *dev,
                             struct ipath_other_headers *ohdr,
                             void *data, u32 tlen,
                             struct ipath_qp *qp,
                             u32 opcode,
                             u32 psn, u32 hdrsize, u32 pmtu,
                             int header_in_data)
{
      struct ipath_swqe *wqe;
      unsigned long flags;
      struct ib_wc wc;
      int diff;
      u32 pad;
      u32 aeth;
      u64 val;

      spin_lock_irqsave(&qp->s_lock, flags);

      /* Ignore invalid responses. */
      if (ipath_cmp24(psn, qp->s_next_psn) >= 0)
            goto ack_done;

      /* Ignore duplicate responses. */
      diff = ipath_cmp24(psn, qp->s_last_psn);
      if (unlikely(diff <= 0)) {
            /* Update credits for "ghost" ACKs */
            if (diff == 0 && opcode == OP(ACKNOWLEDGE)) {
                  if (!header_in_data)
                        aeth = be32_to_cpu(ohdr->u.aeth);
                  else {
                        aeth = be32_to_cpu(((__be32 *) data)[0]);
                        data += sizeof(__be32);
                  }
                  if ((aeth >> 29) == 0)
                        ipath_get_credit(qp, aeth);
            }
            goto ack_done;
      }

      if (unlikely(qp->s_last == qp->s_tail))
            goto ack_done;
      wqe = get_swqe_ptr(qp, qp->s_last);

      switch (opcode) {
      case OP(ACKNOWLEDGE):
      case OP(ATOMIC_ACKNOWLEDGE):
      case OP(RDMA_READ_RESPONSE_FIRST):
            if (!header_in_data)
                  aeth = be32_to_cpu(ohdr->u.aeth);
            else {
                  aeth = be32_to_cpu(((__be32 *) data)[0]);
                  data += sizeof(__be32);
            }
            if (opcode == OP(ATOMIC_ACKNOWLEDGE)) {
                  if (!header_in_data) {
                        __be32 *p = ohdr->u.at.atomic_ack_eth;

                        val = ((u64) be32_to_cpu(p[0]) << 32) |
                              be32_to_cpu(p[1]);
                  } else
                        val = be64_to_cpu(((__be64 *) data)[0]);
            } else
                  val = 0;
            if (!do_rc_ack(qp, aeth, psn, opcode, val) ||
                opcode != OP(RDMA_READ_RESPONSE_FIRST))
                  goto ack_done;
            hdrsize += 4;
            wqe = get_swqe_ptr(qp, qp->s_last);
            if (unlikely(wqe->wr.opcode != IB_WR_RDMA_READ))
                  goto ack_op_err;
            /*
             * If this is a response to a resent RDMA read, we
             * have to be careful to copy the data to the right
             * location.
             */
            qp->s_rdma_read_len = restart_sge(&qp->s_rdma_read_sge,
                                      wqe, psn, pmtu);
            goto read_middle;

      case OP(RDMA_READ_RESPONSE_MIDDLE):
            /* no AETH, no ACK */
            if (unlikely(ipath_cmp24(psn, qp->s_last_psn + 1))) {
                  dev->n_rdma_seq++;
                  ipath_restart_rc(qp, qp->s_last_psn + 1, &wc);
                  goto ack_done;
            }
            if (unlikely(wqe->wr.opcode != IB_WR_RDMA_READ))
                  goto ack_op_err;
      read_middle:
            if (unlikely(tlen != (hdrsize + pmtu + 4)))
                  goto ack_len_err;
            if (unlikely(pmtu >= qp->s_rdma_read_len))
                  goto ack_len_err;

            /* We got a response so update the timeout. */
            spin_lock(&dev->pending_lock);
            if (qp->s_rnr_timeout == 0 && !list_empty(&qp->timerwait))
                  list_move_tail(&qp->timerwait,
                               &dev->pending[dev->pending_index]);
            spin_unlock(&dev->pending_lock);
            /*
             * Update the RDMA receive state but do the copy w/o
             * holding the locks and blocking interrupts.
             */
            qp->s_rdma_read_len -= pmtu;
            update_last_psn(qp, psn);
            spin_unlock_irqrestore(&qp->s_lock, flags);
            ipath_copy_sge(&qp->s_rdma_read_sge, data, pmtu);
            goto bail;

      case OP(RDMA_READ_RESPONSE_ONLY):
            if (!header_in_data)
                  aeth = be32_to_cpu(ohdr->u.aeth);
            else
                  aeth = be32_to_cpu(((__be32 *) data)[0]);
            if (!do_rc_ack(qp, aeth, psn, opcode, 0))
                  goto ack_done;
            /* Get the number of bytes the message was padded by. */
            pad = (be32_to_cpu(ohdr->bth[0]) >> 20) & 3;
            /*
             * Check that the data size is >= 0 && <= pmtu.
             * Remember to account for the AETH header (4) and
             * ICRC (4).
             */
            if (unlikely(tlen < (hdrsize + pad + 8)))
                  goto ack_len_err;
            /*
             * If this is a response to a resent RDMA read, we
             * have to be careful to copy the data to the right
             * location.
             */
            wqe = get_swqe_ptr(qp, qp->s_last);
            qp->s_rdma_read_len = restart_sge(&qp->s_rdma_read_sge,
                                      wqe, psn, pmtu);
            goto read_last;

      case OP(RDMA_READ_RESPONSE_LAST):
            /* ACKs READ req. */
            if (unlikely(ipath_cmp24(psn, qp->s_last_psn + 1))) {
                  dev->n_rdma_seq++;
                  ipath_restart_rc(qp, qp->s_last_psn + 1, &wc);
                  goto ack_done;
            }
            if (unlikely(wqe->wr.opcode != IB_WR_RDMA_READ))
                  goto ack_op_err;
            /* Get the number of bytes the message was padded by. */
            pad = (be32_to_cpu(ohdr->bth[0]) >> 20) & 3;
            /*
             * Check that the data size is >= 1 && <= pmtu.
             * Remember to account for the AETH header (4) and
             * ICRC (4).
             */
            if (unlikely(tlen <= (hdrsize + pad + 8)))
                  goto ack_len_err;
      read_last:
            tlen -= hdrsize + pad + 8;
            if (unlikely(tlen != qp->s_rdma_read_len))
                  goto ack_len_err;
            if (!header_in_data)
                  aeth = be32_to_cpu(ohdr->u.aeth);
            else {
                  aeth = be32_to_cpu(((__be32 *) data)[0]);
                  data += sizeof(__be32);
            }
            ipath_copy_sge(&qp->s_rdma_read_sge, data, tlen);
            (void) do_rc_ack(qp, aeth, psn,
                         OP(RDMA_READ_RESPONSE_LAST), 0);
            goto ack_done;
      }

ack_done:
      spin_unlock_irqrestore(&qp->s_lock, flags);
      goto bail;

ack_op_err:
      wc.status = IB_WC_LOC_QP_OP_ERR;
      goto ack_err;

ack_len_err:
      wc.status = IB_WC_LOC_LEN_ERR;
ack_err:
      wc.wr_id = wqe->wr.wr_id;
      wc.opcode = ib_ipath_wc_opcode[wqe->wr.opcode];
      wc.vendor_err = 0;
      wc.byte_len = 0;
      wc.imm_data = 0;
      wc.qp = &qp->ibqp;
      wc.src_qp = qp->remote_qpn;
      wc.wc_flags = 0;
      wc.pkey_index = 0;
      wc.slid = qp->remote_ah_attr.dlid;
      wc.sl = qp->remote_ah_attr.sl;
      wc.dlid_path_bits = 0;
      wc.port_num = 0;
      ipath_sqerror_qp(qp, &wc);
      spin_unlock_irqrestore(&qp->s_lock, flags);
bail:
      return;
}

/**
 * ipath_rc_rcv_error - process an incoming duplicate or error RC packet
 * @dev: the device this packet came in on
 * @ohdr: the other headers for this packet
 * @data: the packet data
 * @qp: the QP for this packet
 * @opcode: the opcode for this packet
 * @psn: the packet sequence number for this packet
 * @diff: the difference between the PSN and the expected PSN
 * @header_in_data: true if part of the header data is in the data buffer
 *
 * This is called from ipath_rc_rcv() to process an unexpected
 * incoming RC packet for the given QP.
 * Called at interrupt level.
 * Return 1 if no more processing is needed; otherwise return 0 to
 * schedule a response to be sent.
 */
static inline int ipath_rc_rcv_error(struct ipath_ibdev *dev,
                             struct ipath_other_headers *ohdr,
                             void *data,
                             struct ipath_qp *qp,
                             u32 opcode,
                             u32 psn,
                             int diff,
                             int header_in_data)
{
      struct ipath_ack_entry *e;
      u8 i, prev;
      int old_req;
      unsigned long flags;

      if (diff > 0) {
            /*
             * Packet sequence error.
             * A NAK will ACK earlier sends and RDMA writes.
             * Don't queue the NAK if we already sent one.
             */
            if (!qp->r_nak_state) {
                  qp->r_nak_state = IB_NAK_PSN_ERROR;
                  /* Use the expected PSN. */
                  qp->r_ack_psn = qp->r_psn;
                  goto send_ack;
            }
            goto done;
      }

      /*
       * Handle a duplicate request.  Don't re-execute SEND, RDMA
       * write or atomic op.  Don't NAK errors, just silently drop
       * the duplicate request.  Note that r_sge, r_len, and
       * r_rcv_len may be in use so don't modify them.
       *
       * We are supposed to ACK the earliest duplicate PSN but we
       * can coalesce an outstanding duplicate ACK.  We have to
       * send the earliest so that RDMA reads can be restarted at
       * the requester's expected PSN.
       *
       * First, find where this duplicate PSN falls within the
       * ACKs previously sent.
       */
      psn &= IPATH_PSN_MASK;
      e = NULL;
      old_req = 1;
      spin_lock_irqsave(&qp->s_lock, flags);
      for (i = qp->r_head_ack_queue; ; i = prev) {
            if (i == qp->s_tail_ack_queue)
                  old_req = 0;
            if (i)
                  prev = i - 1;
            else
                  prev = IPATH_MAX_RDMA_ATOMIC;
            if (prev == qp->r_head_ack_queue) {
                  e = NULL;
                  break;
            }
            e = &qp->s_ack_queue[prev];
            if (!e->opcode) {
                  e = NULL;
                  break;
            }
            if (ipath_cmp24(psn, e->psn) >= 0) {
                  if (prev == qp->s_tail_ack_queue)
                        old_req = 0;
                  break;
            }
      }
      switch (opcode) {
      case OP(RDMA_READ_REQUEST): {
            struct ib_reth *reth;
            u32 offset;
            u32 len;

            /*
             * If we didn't find the RDMA read request in the ack queue,
             * or the send tasklet is already backed up to send an
             * earlier entry, we can ignore this request.
             */
            if (!e || e->opcode != OP(RDMA_READ_REQUEST) || old_req)
                  goto unlock_done;
            /* RETH comes after BTH */
            if (!header_in_data)
                  reth = &ohdr->u.rc.reth;
            else {
                  reth = (struct ib_reth *)data;
                  data += sizeof(*reth);
            }
            /*
             * Address range must be a subset of the original
             * request and start on pmtu boundaries.
             * We reuse the old ack_queue slot since the requester
             * should not back up and request an earlier PSN for the
             * same request.
             */
            offset = ((psn - e->psn) & IPATH_PSN_MASK) *
                  ib_mtu_enum_to_int(qp->path_mtu);
            len = be32_to_cpu(reth->length);
            if (unlikely(offset + len > e->rdma_sge.sge.sge_length))
                  goto unlock_done;
            if (len != 0) {
                  u32 rkey = be32_to_cpu(reth->rkey);
                  u64 vaddr = be64_to_cpu(reth->vaddr);
                  int ok;

                  ok = ipath_rkey_ok(qp, &e->rdma_sge,
                                 len, vaddr, rkey,
                                 IB_ACCESS_REMOTE_READ);
                  if (unlikely(!ok))
                        goto unlock_done;
            } else {
                  e->rdma_sge.sg_list = NULL;
                  e->rdma_sge.num_sge = 0;
                  e->rdma_sge.sge.mr = NULL;
                  e->rdma_sge.sge.vaddr = NULL;
                  e->rdma_sge.sge.length = 0;
                  e->rdma_sge.sge.sge_length = 0;
            }
            e->psn = psn;
            qp->s_ack_state = OP(ACKNOWLEDGE);
            qp->s_tail_ack_queue = prev;
            break;
      }

      case OP(COMPARE_SWAP):
      case OP(FETCH_ADD): {
            /*
             * If we didn't find the atomic request in the ack queue
             * or the send tasklet is already backed up to send an
             * earlier entry, we can ignore this request.
             */
            if (!e || e->opcode != (u8) opcode || old_req)
                  goto unlock_done;
            qp->s_ack_state = OP(ACKNOWLEDGE);
            qp->s_tail_ack_queue = prev;
            break;
      }

      default:
            if (old_req)
                  goto unlock_done;
            /*
             * Resend the most recent ACK if this request is
             * after all the previous RDMA reads and atomics.
             */
            if (i == qp->r_head_ack_queue) {
                  spin_unlock_irqrestore(&qp->s_lock, flags);
                  qp->r_nak_state = 0;
                  qp->r_ack_psn = qp->r_psn - 1;
                  goto send_ack;
            }
            /*
             * Try to send a simple ACK to work around a Mellanox bug
             * which doesn't accept a RDMA read response or atomic
             * response as an ACK for earlier SENDs or RDMA writes.
             */
            if (qp->r_head_ack_queue == qp->s_tail_ack_queue &&
                !(qp->s_flags & IPATH_S_ACK_PENDING) &&
                qp->s_ack_state == OP(ACKNOWLEDGE)) {
                  spin_unlock_irqrestore(&qp->s_lock, flags);
                  qp->r_nak_state = 0;
                  qp->r_ack_psn = qp->s_ack_queue[i].psn - 1;
                  goto send_ack;
            }
            /*
             * Resend the RDMA read or atomic op which
             * ACKs this duplicate request.
             */
            qp->s_ack_state = OP(ACKNOWLEDGE);
            qp->s_tail_ack_queue = i;
            break;
      }
      qp->r_nak_state = 0;
      tasklet_hi_schedule(&qp->s_task);

unlock_done:
      spin_unlock_irqrestore(&qp->s_lock, flags);
done:
      return 1;

send_ack:
      return 0;
}

static void ipath_rc_error(struct ipath_qp *qp, enum ib_wc_status err)
{
      unsigned long flags;
      int lastwqe;

      spin_lock_irqsave(&qp->s_lock, flags);
      qp->state = IB_QPS_ERR;
      lastwqe = ipath_error_qp(qp, err);
      spin_unlock_irqrestore(&qp->s_lock, flags);

      if (lastwqe) {
            struct ib_event ev;

            ev.device = qp->ibqp.device;
            ev.element.qp = &qp->ibqp;
            ev.event = IB_EVENT_QP_LAST_WQE_REACHED;
            qp->ibqp.event_handler(&ev, qp->ibqp.qp_context);
      }
}

static inline void ipath_update_ack_queue(struct ipath_qp *qp, unsigned n)
{
      unsigned long flags;
      unsigned next;

      next = n + 1;
      if (next > IPATH_MAX_RDMA_ATOMIC)
            next = 0;
      spin_lock_irqsave(&qp->s_lock, flags);
      if (n == qp->s_tail_ack_queue) {
            qp->s_tail_ack_queue = next;
            qp->s_ack_state = OP(ACKNOWLEDGE);
      }
      spin_unlock_irqrestore(&qp->s_lock, flags);
}

/**
 * ipath_rc_rcv - process an incoming RC packet
 * @dev: the device this packet came in on
 * @hdr: the header of this packet
 * @has_grh: true if the header has a GRH
 * @data: the packet data
 * @tlen: the packet length
 * @qp: the QP for this packet
 *
 * This is called from ipath_qp_rcv() to process an incoming RC packet
 * for the given QP.
 * Called at interrupt level.
 */
void ipath_rc_rcv(struct ipath_ibdev *dev, struct ipath_ib_header *hdr,
              int has_grh, void *data, u32 tlen, struct ipath_qp *qp)
{
      struct ipath_other_headers *ohdr;
      u32 opcode;
      u32 hdrsize;
      u32 psn;
      u32 pad;
      struct ib_wc wc;
      u32 pmtu = ib_mtu_enum_to_int(qp->path_mtu);
      int diff;
      struct ib_reth *reth;
      int header_in_data;

      /* Validate the SLID. See Ch. 9.6.1.5 */
      if (unlikely(be16_to_cpu(hdr->lrh[3]) != qp->remote_ah_attr.dlid))
            goto done;

      /* Check for GRH */
      if (!has_grh) {
            ohdr = &hdr->u.oth;
            hdrsize = 8 + 12; /* LRH + BTH */
            psn = be32_to_cpu(ohdr->bth[2]);
            header_in_data = 0;
      } else {
            ohdr = &hdr->u.l.oth;
            hdrsize = 8 + 40 + 12;  /* LRH + GRH + BTH */
            /*
             * The header with GRH is 60 bytes and the core driver sets
             * the eager header buffer size to 56 bytes so the last 4
             * bytes of the BTH header (PSN) is in the data buffer.
             */
            header_in_data = dev->dd->ipath_rcvhdrentsize == 16;
            if (header_in_data) {
                  psn = be32_to_cpu(((__be32 *) data)[0]);
                  data += sizeof(__be32);
            } else
                  psn = be32_to_cpu(ohdr->bth[2]);
      }

      /*
       * Process responses (ACKs) before anything else.  Note that the
       * packet sequence number will be for something in the send work
       * queue rather than the expected receive packet sequence number.
       * In other words, this QP is the requester.
       */
      opcode = be32_to_cpu(ohdr->bth[0]) >> 24;
      if (opcode >= OP(RDMA_READ_RESPONSE_FIRST) &&
          opcode <= OP(ATOMIC_ACKNOWLEDGE)) {
            ipath_rc_rcv_resp(dev, ohdr, data, tlen, qp, opcode, psn,
                          hdrsize, pmtu, header_in_data);
            goto done;
      }

      /* Compute 24 bits worth of difference. */
      diff = ipath_cmp24(psn, qp->r_psn);
      if (unlikely(diff)) {
            if (ipath_rc_rcv_error(dev, ohdr, data, qp, opcode,
                               psn, diff, header_in_data))
                  goto done;
            goto send_ack;
      }

      /* Check for opcode sequence errors. */
      switch (qp->r_state) {
      case OP(SEND_FIRST):
      case OP(SEND_MIDDLE):
            if (opcode == OP(SEND_MIDDLE) ||
                opcode == OP(SEND_LAST) ||
                opcode == OP(SEND_LAST_WITH_IMMEDIATE))
                  break;
      nack_inv:
            ipath_rc_error(qp, IB_WC_REM_INV_REQ_ERR);
            qp->r_nak_state = IB_NAK_INVALID_REQUEST;
            qp->r_ack_psn = qp->r_psn;
            goto send_ack;

      case OP(RDMA_WRITE_FIRST):
      case OP(RDMA_WRITE_MIDDLE):
            if (opcode == OP(RDMA_WRITE_MIDDLE) ||
                opcode == OP(RDMA_WRITE_LAST) ||
                opcode == OP(RDMA_WRITE_LAST_WITH_IMMEDIATE))
                  break;
            goto nack_inv;

      default:
            if (opcode == OP(SEND_MIDDLE) ||
                opcode == OP(SEND_LAST) ||
                opcode == OP(SEND_LAST_WITH_IMMEDIATE) ||
                opcode == OP(RDMA_WRITE_MIDDLE) ||
                opcode == OP(RDMA_WRITE_LAST) ||
                opcode == OP(RDMA_WRITE_LAST_WITH_IMMEDIATE))
                  goto nack_inv;
            /*
             * Note that it is up to the requester to not send a new
             * RDMA read or atomic operation before receiving an ACK
             * for the previous operation.
             */
            break;
      }

      wc.imm_data = 0;
      wc.wc_flags = 0;

      /* OK, process the packet. */
      switch (opcode) {
      case OP(SEND_FIRST):
            if (!ipath_get_rwqe(qp, 0)) {
            rnr_nak:
                  /*
                   * A RNR NAK will ACK earlier sends and RDMA writes.
                   * Don't queue the NAK if a RDMA read or atomic
                   * is pending though.
                   */
                  if (qp->r_nak_state)
                        goto done;
                  qp->r_nak_state = IB_RNR_NAK | qp->r_min_rnr_timer;
                  qp->r_ack_psn = qp->r_psn;
                  goto send_ack;
            }
            qp->r_rcv_len = 0;
            /* FALLTHROUGH */
      case OP(SEND_MIDDLE):
      case OP(RDMA_WRITE_MIDDLE):
      send_middle:
            /* Check for invalid length PMTU or posted rwqe len. */
            if (unlikely(tlen != (hdrsize + pmtu + 4)))
                  goto nack_inv;
            qp->r_rcv_len += pmtu;
            if (unlikely(qp->r_rcv_len > qp->r_len))
                  goto nack_inv;
            ipath_copy_sge(&qp->r_sge, data, pmtu);
            break;

      case OP(RDMA_WRITE_LAST_WITH_IMMEDIATE):
            /* consume RWQE */
            if (!ipath_get_rwqe(qp, 1))
                  goto rnr_nak;
            goto send_last_imm;

      case OP(SEND_ONLY):
      case OP(SEND_ONLY_WITH_IMMEDIATE):
            if (!ipath_get_rwqe(qp, 0))
                  goto rnr_nak;
            qp->r_rcv_len = 0;
            if (opcode == OP(SEND_ONLY))
                  goto send_last;
            /* FALLTHROUGH */
      case OP(SEND_LAST_WITH_IMMEDIATE):
      send_last_imm:
            if (header_in_data) {
                  wc.imm_data = *(__be32 *) data;
                  data += sizeof(__be32);
            } else {
                  /* Immediate data comes after BTH */
                  wc.imm_data = ohdr->u.imm_data;
            }
            hdrsize += 4;
            wc.wc_flags = IB_WC_WITH_IMM;
            /* FALLTHROUGH */
      case OP(SEND_LAST):
      case OP(RDMA_WRITE_LAST):
      send_last:
            /* Get the number of bytes the message was padded by. */
            pad = (be32_to_cpu(ohdr->bth[0]) >> 20) & 3;
            /* Check for invalid length. */
            /* XXX LAST len should be >= 1 */
            if (unlikely(tlen < (hdrsize + pad + 4)))
                  goto nack_inv;
            /* Don't count the CRC. */
            tlen -= (hdrsize + pad + 4);
            wc.byte_len = tlen + qp->r_rcv_len;
            if (unlikely(wc.byte_len > qp->r_len))
                  goto nack_inv;
            ipath_copy_sge(&qp->r_sge, data, tlen);
            qp->r_msn++;
            if (!qp->r_wrid_valid)
                  break;
            qp->r_wrid_valid = 0;
            wc.wr_id = qp->r_wr_id;
            wc.status = IB_WC_SUCCESS;
            wc.opcode = IB_WC_RECV;
            wc.vendor_err = 0;
            wc.qp = &qp->ibqp;
            wc.src_qp = qp->remote_qpn;
            wc.pkey_index = 0;
            wc.slid = qp->remote_ah_attr.dlid;
            wc.sl = qp->remote_ah_attr.sl;
            wc.dlid_path_bits = 0;
            wc.port_num = 0;
            /* Signal completion event if the solicited bit is set. */
            ipath_cq_enter(to_icq(qp->ibqp.recv_cq), &wc,
                         (ohdr->bth[0] &
                        __constant_cpu_to_be32(1 << 23)) != 0);
            break;

      case OP(RDMA_WRITE_FIRST):
      case OP(RDMA_WRITE_ONLY):
      case OP(RDMA_WRITE_ONLY_WITH_IMMEDIATE):
            if (unlikely(!(qp->qp_access_flags &
                         IB_ACCESS_REMOTE_WRITE)))
                  goto nack_inv;
            /* consume RWQE */
            /* RETH comes after BTH */
            if (!header_in_data)
                  reth = &ohdr->u.rc.reth;
            else {
                  reth = (struct ib_reth *)data;
                  data += sizeof(*reth);
            }
            hdrsize += sizeof(*reth);
            qp->r_len = be32_to_cpu(reth->length);
            qp->r_rcv_len = 0;
            if (qp->r_len != 0) {
                  u32 rkey = be32_to_cpu(reth->rkey);
                  u64 vaddr = be64_to_cpu(reth->vaddr);
                  int ok;

                  /* Check rkey & NAK */
                  ok = ipath_rkey_ok(qp, &qp->r_sge,
                                 qp->r_len, vaddr, rkey,
                                 IB_ACCESS_REMOTE_WRITE);
                  if (unlikely(!ok))
                        goto nack_acc;
            } else {
                  qp->r_sge.sg_list = NULL;
                  qp->r_sge.sge.mr = NULL;
                  qp->r_sge.sge.vaddr = NULL;
                  qp->r_sge.sge.length = 0;
                  qp->r_sge.sge.sge_length = 0;
            }
            if (opcode == OP(RDMA_WRITE_FIRST))
                  goto send_middle;
            else if (opcode == OP(RDMA_WRITE_ONLY))
                  goto send_last;
            if (!ipath_get_rwqe(qp, 1))
                  goto rnr_nak;
            goto send_last_imm;

      case OP(RDMA_READ_REQUEST): {
            struct ipath_ack_entry *e;
            u32 len;
            u8 next;

            if (unlikely(!(qp->qp_access_flags &
                         IB_ACCESS_REMOTE_READ)))
                  goto nack_inv;
            next = qp->r_head_ack_queue + 1;
            if (next > IPATH_MAX_RDMA_ATOMIC)
                  next = 0;
            if (unlikely(next == qp->s_tail_ack_queue)) {
                  if (!qp->s_ack_queue[next].sent)
                        goto nack_inv;
                  ipath_update_ack_queue(qp, next);
            }
            e = &qp->s_ack_queue[qp->r_head_ack_queue];
            /* RETH comes after BTH */
            if (!header_in_data)
                  reth = &ohdr->u.rc.reth;
            else {
                  reth = (struct ib_reth *)data;
                  data += sizeof(*reth);
            }
            len = be32_to_cpu(reth->length);
            if (len) {
                  u32 rkey = be32_to_cpu(reth->rkey);
                  u64 vaddr = be64_to_cpu(reth->vaddr);
                  int ok;

                  /* Check rkey & NAK */
                  ok = ipath_rkey_ok(qp, &e->rdma_sge, len, vaddr,
                                 rkey, IB_ACCESS_REMOTE_READ);
                  if (unlikely(!ok))
                        goto nack_acc;
                  /*
                   * Update the next expected PSN.  We add 1 later
                   * below, so only add the remainder here.
                   */
                  if (len > pmtu)
                        qp->r_psn += (len - 1) / pmtu;
            } else {
                  e->rdma_sge.sg_list = NULL;
                  e->rdma_sge.num_sge = 0;
                  e->rdma_sge.sge.mr = NULL;
                  e->rdma_sge.sge.vaddr = NULL;
                  e->rdma_sge.sge.length = 0;
                  e->rdma_sge.sge.sge_length = 0;
            }
            e->opcode = opcode;
            e->sent = 0;
            e->psn = psn;
            /*
             * We need to increment the MSN here instead of when we
             * finish sending the result since a duplicate request would
             * increment it more than once.
             */
            qp->r_msn++;
            qp->r_psn++;
            qp->r_state = opcode;
            qp->r_nak_state = 0;
            barrier();
            qp->r_head_ack_queue = next;

            /* Call ipath_do_rc_send() in another thread. */
            tasklet_hi_schedule(&qp->s_task);

            goto done;
      }

      case OP(COMPARE_SWAP):
      case OP(FETCH_ADD): {
            struct ib_atomic_eth *ateth;
            struct ipath_ack_entry *e;
            u64 vaddr;
            atomic64_t *maddr;
            u64 sdata;
            u32 rkey;
            u8 next;

            if (unlikely(!(qp->qp_access_flags &
                         IB_ACCESS_REMOTE_ATOMIC)))
                  goto nack_inv;
            next = qp->r_head_ack_queue + 1;
            if (next > IPATH_MAX_RDMA_ATOMIC)
                  next = 0;
            if (unlikely(next == qp->s_tail_ack_queue)) {
                  if (!qp->s_ack_queue[next].sent)
                        goto nack_inv;
                  ipath_update_ack_queue(qp, next);
            }
            if (!header_in_data)
                  ateth = &ohdr->u.atomic_eth;
            else
                  ateth = (struct ib_atomic_eth *)data;
            vaddr = ((u64) be32_to_cpu(ateth->vaddr[0]) << 32) |
                  be32_to_cpu(ateth->vaddr[1]);
            if (unlikely(vaddr & (sizeof(u64) - 1)))
                  goto nack_inv;
            rkey = be32_to_cpu(ateth->rkey);
            /* Check rkey & NAK */
            if (unlikely(!ipath_rkey_ok(qp, &qp->r_sge,
                                  sizeof(u64), vaddr, rkey,
                                  IB_ACCESS_REMOTE_ATOMIC)))
                  goto nack_acc;
            /* Perform atomic OP and save result. */
            maddr = (atomic64_t *) qp->r_sge.sge.vaddr;
            sdata = be64_to_cpu(ateth->swap_data);
            e = &qp->s_ack_queue[qp->r_head_ack_queue];
            e->atomic_data = (opcode == OP(FETCH_ADD)) ?
                  (u64) atomic64_add_return(sdata, maddr) - sdata :
                  (u64) cmpxchg((u64 *) qp->r_sge.sge.vaddr,
                              be64_to_cpu(ateth->compare_data),
                              sdata);
            e->opcode = opcode;
            e->sent = 0;
            e->psn = psn & IPATH_PSN_MASK;
            qp->r_msn++;
            qp->r_psn++;
            qp->r_state = opcode;
            qp->r_nak_state = 0;
            barrier();
            qp->r_head_ack_queue = next;

            /* Call ipath_do_rc_send() in another thread. */
            tasklet_hi_schedule(&qp->s_task);

            goto done;
      }

      default:
            /* NAK unknown opcodes. */
            goto nack_inv;
      }
      qp->r_psn++;
      qp->r_state = opcode;
      qp->r_ack_psn = psn;
      qp->r_nak_state = 0;
      /* Send an ACK if requested or required. */
      if (psn & (1 << 31))
            goto send_ack;
      goto done;

nack_acc:
      ipath_rc_error(qp, IB_WC_REM_ACCESS_ERR);
      qp->r_nak_state = IB_NAK_REMOTE_ACCESS_ERROR;
      qp->r_ack_psn = qp->r_psn;

send_ack:
      send_rc_ack(qp);

done:
      return;
}

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