drivers/infiniband/hw/ipath/ipath_ud.c

   1 /*
   2  * Copyright (c) 2006 QLogic, Inc. All rights reserved.
   3  * Copyright (c) 2005, 2006 PathScale, Inc. All rights reserved.
   4  *
   5  * This software is available to you under a choice of one of two
   6  * licenses.  You may choose to be licensed under the terms of the GNU
   7  * General Public License (GPL) Version 2, available from the file
   8  * COPYING in the main directory of this source tree, or the
   9  * OpenIB.org BSD license below:
  10  *
  11  *     Redistribution and use in source and binary forms, with or
  12  *     without modification, are permitted provided that the following
  13  *     conditions are met:
  14  *
  15  *      - Redistributions of source code must retain the above
  16  *        copyright notice, this list of conditions and the following
  17  *        disclaimer.
  18  *
  19  *      - Redistributions in binary form must reproduce the above
  20  *        copyright notice, this list of conditions and the following
  21  *        disclaimer in the documentation and/or other materials
  22  *        provided with the distribution.
  23  *
  24  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  25  * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  26  * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  27  * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
  28  * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
  29  * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
  30  * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  31  * SOFTWARE.
  32  */
  33
  34 #include <rdma/ib_smi.h>
  35
  36 #include "ipath_verbs.h"
  37 #include "ipath_common.h"
  38
  39 /**
  40  * ipath_ud_loopback - handle send on loopback QPs
  41  * @sqp: the QP
  42  * @ss: the SGE state
  43  * @length: the length of the data to send
  44  * @wr: the work request
  45  * @wc: the work completion entry
  46  *
  47  * This is called from ipath_post_ud_send() to forward a WQE addressed
  48  * to the same HCA.
  49  */
  50 static void ipath_ud_loopback(struct ipath_qp *sqp,
  51                               struct ipath_sge_state *ss,
  52                               u32 length, struct ib_send_wr *wr,
  53                               struct ib_wc *wc)
  54 {
  55         struct ipath_ibdev *dev = to_idev(sqp->ibqp.device);
  56         struct ipath_qp *qp;
  57         struct ib_ah_attr *ah_attr;
  58         unsigned long flags;
  59         struct ipath_rq *rq;
  60         struct ipath_srq *srq;
  61         struct ipath_sge_state rsge;
  62         struct ipath_sge *sge;
  63         struct ipath_rwqe *wqe;
  64
  65         qp = ipath_lookup_qpn(&dev->qp_table, wr->wr.ud.remote_qpn);
  66         if (!qp)
  67                 return;
  68
  69         /*
  70          * Check that the qkey matches (except for QP0, see 9.6.1.4.1).
  71          * Qkeys with the high order bit set mean use the
  72          * qkey from the QP context instead of the WR (see 10.2.5).
  73          */
  74         if (unlikely(qp->ibqp.qp_num &&
  75                      ((int) wr->wr.ud.remote_qkey < 0
  76                       ? qp->qkey : wr->wr.ud.remote_qkey) != qp->qkey)) {
  77                 /* XXX OK to lose a count once in a while. */
  78                 dev->qkey_violations++;
  79                 dev->n_pkt_drops++;
  80                 goto done;
  81         }
  82
  83         /*
  84          * A GRH is expected to preceed the data even if not
  85          * present on the wire.
  86          */
  87         wc->byte_len = length + sizeof(struct ib_grh);
  88
  89         if (wr->opcode == IB_WR_SEND_WITH_IMM) {
  90                 wc->wc_flags = IB_WC_WITH_IMM;
  91                 wc->imm_data = wr->imm_data;
  92         } else {
  93                 wc->wc_flags = 0;
  94                 wc->imm_data = 0;
  95         }
  96
  97         /*
  98          * Get the next work request entry to find where to put the data.
  99          * Note that it is safe to drop the lock after changing rq->tail
 100          * since ipath_post_receive() won't fill the empty slot.
 101          */
 102         if (qp->ibqp.srq) {
 103                 srq = to_isrq(qp->ibqp.srq);
 104                 rq = &srq->rq;
 105         } else {
 106                 srq = NULL;
 107                 rq = &qp->r_rq;
 108         }
 109         spin_lock_irqsave(&rq->lock, flags);
 110         if (rq->tail == rq->head) {
 111                 spin_unlock_irqrestore(&rq->lock, flags);
 112                 dev->n_pkt_drops++;
 113                 goto done;
 114         }
 115         /* Silently drop packets which are too big. */
 116         wqe = get_rwqe_ptr(rq, rq->tail);
 117         if (wc->byte_len > wqe->length) {
 118                 spin_unlock_irqrestore(&rq->lock, flags);
 119                 dev->n_pkt_drops++;
 120                 goto done;
 121         }
 122         wc->wr_id = wqe->wr_id;
 123         rsge.sge = wqe->sg_list[0];
 124         rsge.sg_list = wqe->sg_list + 1;
 125         rsge.num_sge = wqe->num_sge;
 126         if (++rq->tail >= rq->size)
 127                 rq->tail = 0;
 128         if (srq && srq->ibsrq.event_handler) {
 129                 u32 n;
 130
 131                 if (rq->head < rq->tail)
 132                         n = rq->size + rq->head - rq->tail;
 133                 else
 134                         n = rq->head - rq->tail;
 135                 if (n < srq->limit) {
 136                         struct ib_event ev;
 137
 138                         srq->limit = 0;
 139                         spin_unlock_irqrestore(&rq->lock, flags);
 140                         ev.device = qp->ibqp.device;
 141                         ev.element.srq = qp->ibqp.srq;
 142                         ev.event = IB_EVENT_SRQ_LIMIT_REACHED;
 143                         srq->ibsrq.event_handler(&ev,
 144                                                  srq->ibsrq.srq_context);
 145                 } else
 146                         spin_unlock_irqrestore(&rq->lock, flags);
 147         } else
 148                 spin_unlock_irqrestore(&rq->lock, flags);
 149         ah_attr = &to_iah(wr->wr.ud.ah)->attr;
 150         if (ah_attr->ah_flags & IB_AH_GRH) {
 151                 ipath_copy_sge(&rsge, &ah_attr->grh, sizeof(struct ib_grh));
 152                 wc->wc_flags |= IB_WC_GRH;
 153         } else
 154                 ipath_skip_sge(&rsge, sizeof(struct ib_grh));
 155         sge = &ss->sge;
 156         while (length) {
 157                 u32 len = sge->length;
 158
 159                 if (len > length)
 160                         len = length;
 161                 BUG_ON(len == 0);
 162                 ipath_copy_sge(&rsge, sge->vaddr, len);
 163                 sge->vaddr += len;
 164                 sge->length -= len;
 165                 sge->sge_length -= len;
 166                 if (sge->sge_length == 0) {
 167                         if (--ss->num_sge)
 168                                 *sge = *ss->sg_list++;
 169                 } else if (sge->length == 0 && sge->mr != NULL) {
 170                         if (++sge->n >= IPATH_SEGSZ) {
 171                                 if (++sge->m >= sge->mr->mapsz)
 172                                         break;
 173                                 sge->n = 0;
 174                         }
 175                         sge->vaddr =
 176                                 sge->mr->map[sge->m]->segs[sge->n].vaddr;
 177                         sge->length =
 178                                 sge->mr->map[sge->m]->segs[sge->n].length;
 179                 }
 180                 length -= len;
 181         }
 182         wc->status = IB_WC_SUCCESS;
 183         wc->opcode = IB_WC_RECV;
 184         wc->vendor_err = 0;
 185         wc->qp_num = qp->ibqp.qp_num;
 186         wc->src_qp = sqp->ibqp.qp_num;
 187         /* XXX do we know which pkey matched? Only needed for GSI. */
 188         wc->pkey_index = 0;
 189         wc->slid = ipath_layer_get_lid(dev->dd) |
 190                 (ah_attr->src_path_bits &
 191                  ((1 << (dev->mkeyprot_resv_lmc & 7)) - 1));
 192         wc->sl = ah_attr->sl;
 193         wc->dlid_path_bits =
 194                 ah_attr->dlid & ((1 << (dev->mkeyprot_resv_lmc & 7)) - 1);
 195         /* Signal completion event if the solicited bit is set. */
 196         ipath_cq_enter(to_icq(qp->ibqp.recv_cq), wc,
 197                        wr->send_flags & IB_SEND_SOLICITED);
 198
 199 done:
 200         if (atomic_dec_and_test(&qp->refcount))
 201                 wake_up(&qp->wait);
 202 }
 203
 204 /**
 205  * ipath_post_ud_send - post a UD send on QP
 206  * @qp: the QP
 207  * @wr: the work request
 208  *
 209  * Note that we actually send the data as it is posted instead of putting
 210  * the request into a ring buffer.  If we wanted to use a ring buffer,
 211  * we would need to save a reference to the destination address in the SWQE.
 212  */
 213 int ipath_post_ud_send(struct ipath_qp *qp, struct ib_send_wr *wr)
 214 {
 215         struct ipath_ibdev *dev = to_idev(qp->ibqp.device);
 216         struct ipath_other_headers *ohdr;
 217         struct ib_ah_attr *ah_attr;
 218         struct ipath_sge_state ss;
 219         struct ipath_sge *sg_list;
 220         struct ib_wc wc;
 221         u32 hwords;
 222         u32 nwords;
 223         u32 len;
 224         u32 extra_bytes;
 225         u32 bth0;
 226         u16 lrh0;
 227         u16 lid;
 228         int i;
 229         int ret;
 230
 231         if (!(ib_ipath_state_ops[qp->state] & IPATH_PROCESS_SEND_OK)) {
 232                 ret = 0;
 233                 goto bail;
 234         }
 235
 236         /* IB spec says that num_sge == 0 is OK. */
 237         if (wr->num_sge > qp->s_max_sge) {
 238                 ret = -EINVAL;
 239                 goto bail;
 240         }
 241
 242         if (wr->num_sge > 1) {
 243                 sg_list = kmalloc((qp->s_max_sge - 1) * sizeof(*sg_list),
 244                                   GFP_ATOMIC);
 245                 if (!sg_list) {
 246                         ret = -ENOMEM;
 247                         goto bail;
 248                 }
 249         } else
 250                 sg_list = NULL;
 251
 252         /* Check the buffer to send. */
 253         ss.sg_list = sg_list;
 254         ss.sge.mr = NULL;
 255         ss.sge.vaddr = NULL;
 256         ss.sge.length = 0;
 257         ss.sge.sge_length = 0;
 258         ss.num_sge = 0;
 259         len = 0;
 260         for (i = 0; i < wr->num_sge; i++) {
 261                 /* Check LKEY */
 262                 if (to_ipd(qp->ibqp.pd)->user && wr->sg_list[i].lkey == 0) {
 263                         ret = -EINVAL;
 264                         goto bail;
 265                 }
 266
 267                 if (wr->sg_list[i].length == 0)
 268                         continue;
 269                 if (!ipath_lkey_ok(&dev->lk_table, ss.num_sge ?
 270                                    sg_list + ss.num_sge - 1 : &ss.sge,
 271                                    &wr->sg_list[i], 0)) {
 272                         ret = -EINVAL;
 273                         goto bail;
 274                 }
 275                 len += wr->sg_list[i].length;
 276                 ss.num_sge++;
 277         }
 278         /* Check for invalid packet size. */
 279         if (len > ipath_layer_get_ibmtu(dev->dd)) {
 280                 ret = -EINVAL;
 281                 goto bail;
 282         }
 283         extra_bytes = (4 - len) & 3;
 284         nwords = (len + extra_bytes) >> 2;
 285
 286         /* Construct the header. */
 287         ah_attr = &to_iah(wr->wr.ud.ah)->attr;
 288         if (ah_attr->dlid == 0) {
 289                 ret = -EINVAL;
 290                 goto bail;
 291         }
 292         if (ah_attr->dlid >= IPATH_MULTICAST_LID_BASE) {
 293                 if (ah_attr->dlid != IPATH_PERMISSIVE_LID)
 294                         dev->n_multicast_xmit++;
 295                 else
 296                         dev->n_unicast_xmit++;
 297         } else {
 298                 dev->n_unicast_xmit++;
 299                 lid = ah_attr->dlid &
 300                         ~((1 << (dev->mkeyprot_resv_lmc & 7)) - 1);
 301                 if (unlikely(lid == ipath_layer_get_lid(dev->dd))) {
 302                         /*
 303                          * Pass in an uninitialized ib_wc to save stack
 304                          * space.
 305                          */
 306                         ipath_ud_loopback(qp, &ss, len, wr, &wc);
 307                         goto done;
 308                 }
 309         }
 310         if (ah_attr->ah_flags & IB_AH_GRH) {
 311                 /* Header size in 32-bit words. */
 312                 hwords = 17;
 313                 lrh0 = IPATH_LRH_GRH;
 314                 ohdr = &qp->s_hdr.u.l.oth;
 315                 qp->s_hdr.u.l.grh.version_tclass_flow =
 316                         cpu_to_be32((6 << 28) |
 317                                     (ah_attr->grh.traffic_class << 20) |
 318                                     ah_attr->grh.flow_label);
 319                 qp->s_hdr.u.l.grh.paylen =
 320                         cpu_to_be16(((wr->opcode ==
 321                                       IB_WR_SEND_WITH_IMM ? 6 : 5) +
 322                                      nwords + SIZE_OF_CRC) << 2);
 323                 /* next_hdr is defined by C8-7 in ch. 8.4.1 */
 324                 qp->s_hdr.u.l.grh.next_hdr = 0x1B;
 325                 qp->s_hdr.u.l.grh.hop_limit = ah_attr->grh.hop_limit;
 326                 /* The SGID is 32-bit aligned. */
 327                 qp->s_hdr.u.l.grh.sgid.global.subnet_prefix =
 328                         dev->gid_prefix;
 329                 qp->s_hdr.u.l.grh.sgid.global.interface_id =
 330                         ipath_layer_get_guid(dev->dd);
 331                 qp->s_hdr.u.l.grh.dgid = ah_attr->grh.dgid;
 332                 /*
 333                  * Don't worry about sending to locally attached multicast
 334                  * QPs.  It is unspecified by the spec. what happens.
 335                  */
 336         } else {
 337                 /* Header size in 32-bit words. */
 338                 hwords = 7;
 339                 lrh0 = IPATH_LRH_BTH;
 340                 ohdr = &qp->s_hdr.u.oth;
 341         }
 342         if (wr->opcode == IB_WR_SEND_WITH_IMM) {
 343                 ohdr->u.ud.imm_data = wr->imm_data;
 344                 wc.imm_data = wr->imm_data;
 345                 hwords += 1;
 346                 bth0 = IB_OPCODE_UD_SEND_ONLY_WITH_IMMEDIATE << 24;
 347         } else if (wr->opcode == IB_WR_SEND) {
 348                 wc.imm_data = 0;
 349                 bth0 = IB_OPCODE_UD_SEND_ONLY << 24;
 350         } else {
 351                 ret = -EINVAL;
 352                 goto bail;
 353         }
 354         lrh0 |= ah_attr->sl << 4;
 355         if (qp->ibqp.qp_type == IB_QPT_SMI)
 356                 lrh0 |= 0xF000; /* Set VL (see ch. 13.5.3.1) */
 357         qp->s_hdr.lrh[0] = cpu_to_be16(lrh0);
 358         qp->s_hdr.lrh[1] = cpu_to_be16(ah_attr->dlid);  /* DEST LID */
 359         qp->s_hdr.lrh[2] = cpu_to_be16(hwords + nwords + SIZE_OF_CRC);
 360         lid = ipath_layer_get_lid(dev->dd);
 361         if (lid) {
 362                 lid |= ah_attr->src_path_bits &
 363                         ((1 << (dev->mkeyprot_resv_lmc & 7)) - 1);
 364                 qp->s_hdr.lrh[3] = cpu_to_be16(lid);
 365         } else
 366                 qp->s_hdr.lrh[3] = IB_LID_PERMISSIVE;
 367         if (wr->send_flags & IB_SEND_SOLICITED)
 368                 bth0 |= 1 << 23;
 369         bth0 |= extra_bytes << 20;
 370         bth0 |= qp->ibqp.qp_type == IB_QPT_SMI ? IPATH_DEFAULT_P_KEY :
 371                 ipath_layer_get_pkey(dev->dd, qp->s_pkey_index);
 372         ohdr->bth[0] = cpu_to_be32(bth0);
 373         /*
 374          * Use the multicast QP if the destination LID is a multicast LID.
 375          */
 376         ohdr->bth[1] = ah_attr->dlid >= IPATH_MULTICAST_LID_BASE &&
 377                 ah_attr->dlid != IPATH_PERMISSIVE_LID ?
 378                 __constant_cpu_to_be32(IPATH_MULTICAST_QPN) :
 379                 cpu_to_be32(wr->wr.ud.remote_qpn);
 380         /* XXX Could lose a PSN count but not worth locking */
 381         ohdr->bth[2] = cpu_to_be32(qp->s_next_psn++ & IPATH_PSN_MASK);
 382         /*
 383          * Qkeys with the high order bit set mean use the
 384          * qkey from the QP context instead of the WR (see 10.2.5).
 385          */
 386         ohdr->u.ud.deth[0] = cpu_to_be32((int)wr->wr.ud.remote_qkey < 0 ?
 387                                          qp->qkey : wr->wr.ud.remote_qkey);
 388         ohdr->u.ud.deth[1] = cpu_to_be32(qp->ibqp.qp_num);
 389         if (ipath_verbs_send(dev->dd, hwords, (u32 *) &qp->s_hdr,
 390                              len, &ss))
 391                 dev->n_no_piobuf++;
 392
 393 done:
 394         /* Queue the completion status entry. */
 395         if (!test_bit(IPATH_S_SIGNAL_REQ_WR, &qp->s_flags) ||
 396             (wr->send_flags & IB_SEND_SIGNALED)) {
 397                 wc.wr_id = wr->wr_id;
 398                 wc.status = IB_WC_SUCCESS;
 399                 wc.vendor_err = 0;
 400                 wc.opcode = IB_WC_SEND;
 401                 wc.byte_len = len;
 402                 wc.qp_num = qp->ibqp.qp_num;
 403                 wc.src_qp = 0;
 404                 wc.wc_flags = 0;
 405                 /* XXX initialize other fields? */
 406                 ipath_cq_enter(to_icq(qp->ibqp.send_cq), &wc, 0);
 407         }
 408         kfree(sg_list);
 409
 410         ret = 0;
 411
 412 bail:
 413         return ret;
 414 }
 415
 416 /**
 417  * ipath_ud_rcv - receive an incoming UD packet
 418  * @dev: the device the packet came in on
 419  * @hdr: the packet header
 420  * @has_grh: true if the packet has a GRH
 421  * @data: the packet data
 422  * @tlen: the packet length
 423  * @qp: the QP the packet came on
 424  *
 425  * This is called from ipath_qp_rcv() to process an incoming UD packet
 426  * for the given QP.
 427  * Called at interrupt level.
 428  */
 429 void ipath_ud_rcv(struct ipath_ibdev *dev, struct ipath_ib_header *hdr,
 430                   int has_grh, void *data, u32 tlen, struct ipath_qp *qp)
 431 {
 432         struct ipath_other_headers *ohdr;
 433         int opcode;
 434         u32 hdrsize;
 435         u32 pad;
 436         unsigned long flags;
 437         struct ib_wc wc;
 438         u32 qkey;
 439         u32 src_qp;
 440         struct ipath_rq *rq;
 441         struct ipath_srq *srq;
 442         struct ipath_rwqe *wqe;
 443         u16 dlid;
 444         int header_in_data;
 445
 446         /* Check for GRH */
 447         if (!has_grh) {
 448                 ohdr = &hdr->u.oth;
 449                 hdrsize = 8 + 12 + 8;   /* LRH + BTH + DETH */
 450                 qkey = be32_to_cpu(ohdr->u.ud.deth[0]);
 451                 src_qp = be32_to_cpu(ohdr->u.ud.deth[1]);
 452                 header_in_data = 0;
 453         } else {
 454                 ohdr = &hdr->u.l.oth;
 455                 hdrsize = 8 + 40 + 12 + 8; /* LRH + GRH + BTH + DETH */
 456                 /*
 457                  * The header with GRH is 68 bytes and the core driver sets
 458                  * the eager header buffer size to 56 bytes so the last 12
 459                  * bytes of the IB header is in the data buffer.
 460                  */
 461                 header_in_data =
 462                         ipath_layer_get_rcvhdrentsize(dev->dd) == 16;
 463                 if (header_in_data) {
 464                         qkey = be32_to_cpu(((__be32 *) data)[1]);
 465                         src_qp = be32_to_cpu(((__be32 *) data)[2]);
 466                         data += 12;
 467                 } else {
 468                         qkey = be32_to_cpu(ohdr->u.ud.deth[0]);
 469                         src_qp = be32_to_cpu(ohdr->u.ud.deth[1]);
 470                 }
 471         }
 472         src_qp &= IPATH_QPN_MASK;
 473
 474         /*
 475          * Check that the permissive LID is only used on QP0
 476          * and the QKEY matches (see 9.6.1.4.1 and 9.6.1.5.1).
 477          */
 478         if (qp->ibqp.qp_num) {
 479                 if (unlikely(hdr->lrh[1] == IB_LID_PERMISSIVE ||
 480                              hdr->lrh[3] == IB_LID_PERMISSIVE)) {
 481                         dev->n_pkt_drops++;
 482                         goto bail;
 483                 }
 484                 if (unlikely(qkey != qp->qkey)) {
 485                         /* XXX OK to lose a count once in a while. */
 486                         dev->qkey_violations++;
 487                         dev->n_pkt_drops++;
 488                         goto bail;
 489                 }
 490         } else if (hdr->lrh[1] == IB_LID_PERMISSIVE ||
 491                    hdr->lrh[3] == IB_LID_PERMISSIVE) {
 492                 struct ib_smp *smp = (struct ib_smp *) data;
 493
 494                 if (smp->mgmt_class != IB_MGMT_CLASS_SUBN_DIRECTED_ROUTE) {
 495                         dev->n_pkt_drops++;
 496                         goto bail;
 497                 }
 498         }
 499
 500         /* Get the number of bytes the message was padded by. */
 501         pad = (be32_to_cpu(ohdr->bth[0]) >> 20) & 3;
 502         if (unlikely(tlen < (hdrsize + pad + 4))) {
 503                 /* Drop incomplete packets. */
 504                 dev->n_pkt_drops++;
 505                 goto bail;
 506         }
 507         tlen -= hdrsize + pad + 4;
 508
 509         /* Drop invalid MAD packets (see 13.5.3.1). */
 510         if (unlikely((qp->ibqp.qp_num == 0 &&
 511                       (tlen != 256 ||
 512                        (be16_to_cpu(hdr->lrh[0]) >> 12) != 15)) ||
 513                      (qp->ibqp.qp_num == 1 &&
 514                       (tlen != 256 ||
 515                        (be16_to_cpu(hdr->lrh[0]) >> 12) == 15)))) {
 516                 dev->n_pkt_drops++;
 517                 goto bail;
 518         }
 519
 520         /*
 521          * A GRH is expected to preceed the data even if not
 522          * present on the wire.
 523          */
 524         wc.byte_len = tlen + sizeof(struct ib_grh);
 525
 526         /*
 527          * The opcode is in the low byte when its in network order
 528          * (top byte when in host order).
 529          */
 530         opcode = be32_to_cpu(ohdr->bth[0]) >> 24;
 531         if (qp->ibqp.qp_num > 1 &&
 532             opcode == IB_OPCODE_UD_SEND_ONLY_WITH_IMMEDIATE) {
 533                 if (header_in_data) {
 534                         wc.imm_data = *(__be32 *) data;
 535                         data += sizeof(__be32);
 536                 } else
 537                         wc.imm_data = ohdr->u.ud.imm_data;
 538                 wc.wc_flags = IB_WC_WITH_IMM;
 539                 hdrsize += sizeof(u32);
 540         } else if (opcode == IB_OPCODE_UD_SEND_ONLY) {
 541                 wc.imm_data = 0;
 542                 wc.wc_flags = 0;
 543         } else {
 544                 dev->n_pkt_drops++;
 545                 goto bail;
 546         }
 547
 548         /*
 549          * Get the next work request entry to find where to put the data.
 550          * Note that it is safe to drop the lock after changing rq->tail
 551          * since ipath_post_receive() won't fill the empty slot.
 552          */
 553         if (qp->ibqp.srq) {
 554                 srq = to_isrq(qp->ibqp.srq);
 555                 rq = &srq->rq;
 556         } else {
 557                 srq = NULL;
 558                 rq = &qp->r_rq;
 559         }
 560         spin_lock_irqsave(&rq->lock, flags);
 561         if (rq->tail == rq->head) {
 562                 spin_unlock_irqrestore(&rq->lock, flags);
 563                 /*
 564                  * Count VL15 packets dropped due to no receive buffer.
 565                  * Otherwise, count them as buffer overruns since usually,
 566                  * the HW will be able to receive packets even if there are
 567                  * no QPs with posted receive buffers.
 568                  */
 569                 if (qp->ibqp.qp_num == 0)
 570                         dev->n_vl15_dropped++;
 571                 else
 572                         dev->rcv_errors++;
 573                 goto bail;
 574         }
 575         /* Silently drop packets which are too big. */
 576         wqe = get_rwqe_ptr(rq, rq->tail);
 577         if (wc.byte_len > wqe->length) {
 578                 spin_unlock_irqrestore(&rq->lock, flags);
 579                 dev->n_pkt_drops++;
 580                 goto bail;
 581         }
 582         wc.wr_id = wqe->wr_id;
 583         qp->r_sge.sge = wqe->sg_list[0];
 584         qp->r_sge.sg_list = wqe->sg_list + 1;
 585         qp->r_sge.num_sge = wqe->num_sge;
 586         if (++rq->tail >= rq->size)
 587                 rq->tail = 0;
 588         if (srq && srq->ibsrq.event_handler) {
 589                 u32 n;
 590
 591                 if (rq->head < rq->tail)
 592                         n = rq->size + rq->head - rq->tail;
 593                 else
 594                         n = rq->head - rq->tail;
 595                 if (n < srq->limit) {
 596                         struct ib_event ev;
 597
 598                         srq->limit = 0;
 599                         spin_unlock_irqrestore(&rq->lock, flags);
 600                         ev.device = qp->ibqp.device;
 601                         ev.element.srq = qp->ibqp.srq;
 602                         ev.event = IB_EVENT_SRQ_LIMIT_REACHED;
 603                         srq->ibsrq.event_handler(&ev,
 604                                                  srq->ibsrq.srq_context);
 605                 } else
 606                         spin_unlock_irqrestore(&rq->lock, flags);
 607         } else
 608                 spin_unlock_irqrestore(&rq->lock, flags);
 609         if (has_grh) {
 610                 ipath_copy_sge(&qp->r_sge, &hdr->u.l.grh,
 611                                sizeof(struct ib_grh));
 612                 wc.wc_flags |= IB_WC_GRH;
 613         } else
 614                 ipath_skip_sge(&qp->r_sge, sizeof(struct ib_grh));
 615         ipath_copy_sge(&qp->r_sge, data,
 616                        wc.byte_len - sizeof(struct ib_grh));
 617         wc.status = IB_WC_SUCCESS;
 618         wc.opcode = IB_WC_RECV;
 619         wc.vendor_err = 0;
 620         wc.qp_num = qp->ibqp.qp_num;
 621         wc.src_qp = src_qp;
 622         /* XXX do we know which pkey matched? Only needed for GSI. */
 623         wc.pkey_index = 0;
 624         wc.slid = be16_to_cpu(hdr->lrh[3]);
 625         wc.sl = (be16_to_cpu(hdr->lrh[0]) >> 4) & 0xF;
 626         dlid = be16_to_cpu(hdr->lrh[1]);
 627         /*
 628          * Save the LMC lower bits if the destination LID is a unicast LID.
 629          */
 630         wc.dlid_path_bits = dlid >= IPATH_MULTICAST_LID_BASE ? 0 :
 631                 dlid & ((1 << (dev->mkeyprot_resv_lmc & 7)) - 1);
 632         /* Signal completion event if the solicited bit is set. */
 633         ipath_cq_enter(to_icq(qp->ibqp.recv_cq), &wc,
 634                        (ohdr->bth[0] &
 635                         __constant_cpu_to_be32(1 << 23)) != 0);
 636
 637 bail:;
 638 }