lib/librte_vhost/virtio_net.c

   1 /*-
   2  *   BSD LICENSE
   3  *
   4  *   Copyright(c) 2010-2016 Intel Corporation. All rights reserved.
   5  *   All rights reserved.
   6  *
   7  *   Redistribution and use in source and binary forms, with or without
   8  *   modification, are permitted provided that the following conditions
   9  *   are met:
  10  *
  11  *     * Redistributions of source code must retain the above copyright
  12  *       notice, this list of conditions and the following disclaimer.
  13  *     * Redistributions in binary form must reproduce the above copyright
  14  *       notice, this list of conditions and the following disclaimer in
  15  *       the documentation and/or other materials provided with the
  16  *       distribution.
  17  *     * Neither the name of Intel Corporation nor the names of its
  18  *       contributors may be used to endorse or promote products derived
  19  *       from this software without specific prior written permission.
  20  *
  21  *   THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  22  *   "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  23  *   LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  24  *   A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  25  *   OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  26  *   SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  27  *   LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  28  *   DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  29  *   THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  30  *   (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  31  *   OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  32  */
  33
  34 #include <stdint.h>
  35 #include <stdbool.h>
  36 #include <linux/virtio_net.h>
  37
  38 #include <rte_mbuf.h>
  39 #include <rte_memcpy.h>
  40 #include <rte_ether.h>
  41 #include <rte_ip.h>
  42 #include <rte_vhost.h>
  43 #include <rte_tcp.h>
  44 #include <rte_udp.h>
  45 #include <rte_sctp.h>
  46 #include <rte_arp.h>
  47
  48 #include "vhost.h"
  49
  50 #define MAX_PKT_BURST 32
  51
  52 static bool
  53 is_valid_virt_queue_idx(uint32_t idx, int is_tx, uint32_t nr_vring)
  54 {
  55         return (is_tx ^ (idx & 1)) == 0 && idx < nr_vring;
  56 }
  57
  58 static __rte_always_inline void
  59 do_flush_shadow_used_ring(struct virtio_net *dev, struct vhost_virtqueue *vq,
  60                           uint16_t to, uint16_t from, uint16_t size)
  61 {
  62         rte_memcpy(&vq->used->ring[to],
  63                         &vq->shadow_used_ring[from],
  64                         size * sizeof(struct vring_used_elem));
  65         vhost_log_used_vring(dev, vq,
  66                         offsetof(struct vring_used, ring[to]),
  67                         size * sizeof(struct vring_used_elem));
  68 }
  69
  70 static __rte_always_inline void
  71 flush_shadow_used_ring(struct virtio_net *dev, struct vhost_virtqueue *vq)
  72 {
  73         uint16_t used_idx = vq->last_used_idx & (vq->size - 1);
  74
  75         if (used_idx + vq->shadow_used_idx <= vq->size) {
  76                 do_flush_shadow_used_ring(dev, vq, used_idx, 0,
  77                                           vq->shadow_used_idx);
  78         } else {
  79                 uint16_t size;
  80
  81                 /* update used ring interval [used_idx, vq->size] */
  82                 size = vq->size - used_idx;
  83                 do_flush_shadow_used_ring(dev, vq, used_idx, 0, size);
  84
  85                 /* update the left half used ring interval [0, left_size] */
  86                 do_flush_shadow_used_ring(dev, vq, 0, size,
  87                                           vq->shadow_used_idx - size);
  88         }
  89         vq->last_used_idx += vq->shadow_used_idx;
  90
  91         rte_smp_wmb();
  92
  93         *(volatile uint16_t *)&vq->used->idx += vq->shadow_used_idx;
  94         vhost_log_used_vring(dev, vq, offsetof(struct vring_used, idx),
  95                 sizeof(vq->used->idx));
  96 }
  97
  98 static __rte_always_inline void
  99 update_shadow_used_ring(struct vhost_virtqueue *vq,
 100                          uint16_t desc_idx, uint16_t len)
 101 {
 102         uint16_t i = vq->shadow_used_idx++;
 103
 104         vq->shadow_used_ring[i].id  = desc_idx;
 105         vq->shadow_used_ring[i].len = len;
 106 }
 107
 108 /* avoid write operation when necessary, to lessen cache issues */
 109 #define ASSIGN_UNLESS_EQUAL(var, val) do {      \
 110         if ((var) != (val))                     \
 111                 (var) = (val);                  \
 112 } while (0)
 113
 114 static void
 115 virtio_enqueue_offload(struct rte_mbuf *m_buf, struct virtio_net_hdr *net_hdr)
 116 {
 117         uint64_t csum_l4 = m_buf->ol_flags & PKT_TX_L4_MASK;
 118
 119         if (m_buf->ol_flags & PKT_TX_TCP_SEG)
 120                 csum_l4 |= PKT_TX_TCP_CKSUM;
 121
 122         if (csum_l4) {
 123                 net_hdr->flags = VIRTIO_NET_HDR_F_NEEDS_CSUM;
 124                 net_hdr->csum_start = m_buf->l2_len + m_buf->l3_len;
 125
 126                 switch (csum_l4) {
 127                 case PKT_TX_TCP_CKSUM:
 128                         net_hdr->csum_offset = (offsetof(struct tcp_hdr,
 129                                                 cksum));
 130                         break;
 131                 case PKT_TX_UDP_CKSUM:
 132                         net_hdr->csum_offset = (offsetof(struct udp_hdr,
 133                                                 dgram_cksum));
 134                         break;
 135                 case PKT_TX_SCTP_CKSUM:
 136                         net_hdr->csum_offset = (offsetof(struct sctp_hdr,
 137                                                 cksum));
 138                         break;
 139                 }
 140         } else {
 141                 ASSIGN_UNLESS_EQUAL(net_hdr->csum_start, 0);
 142                 ASSIGN_UNLESS_EQUAL(net_hdr->csum_offset, 0);
 143                 ASSIGN_UNLESS_EQUAL(net_hdr->flags, 0);
 144         }
 145
 146         if (m_buf->ol_flags & PKT_TX_TCP_SEG) {
 147                 if (m_buf->ol_flags & PKT_TX_IPV4)
 148                         net_hdr->gso_type = VIRTIO_NET_HDR_GSO_TCPV4;
 149                 else
 150                         net_hdr->gso_type = VIRTIO_NET_HDR_GSO_TCPV6;
 151                 net_hdr->gso_size = m_buf->tso_segsz;
 152                 net_hdr->hdr_len = m_buf->l2_len + m_buf->l3_len
 153                                         + m_buf->l4_len;
 154         } else {
 155                 ASSIGN_UNLESS_EQUAL(net_hdr->gso_type, 0);
 156                 ASSIGN_UNLESS_EQUAL(net_hdr->gso_size, 0);
 157                 ASSIGN_UNLESS_EQUAL(net_hdr->hdr_len, 0);
 158         }
 159 }
 160
 161 static __rte_always_inline int
 162 copy_mbuf_to_desc(struct virtio_net *dev, struct vring_desc *descs,
 163                   struct rte_mbuf *m, uint16_t desc_idx, uint32_t size)
 164 {
 165         uint32_t desc_avail, desc_offset;
 166         uint32_t mbuf_avail, mbuf_offset;
 167         uint32_t cpy_len;
 168         struct vring_desc *desc;
 169         uint64_t desc_addr;
 170         /* A counter to avoid desc dead loop chain */
 171         uint16_t nr_desc = 1;
 172
 173         desc = &descs[desc_idx];
 174         desc_addr = rte_vhost_gpa_to_vva(dev->mem, desc->addr);
 175         /*
 176          * Checking of 'desc_addr' placed outside of 'unlikely' macro to avoid
 177          * performance issue with some versions of gcc (4.8.4 and 5.3.0) which
 178          * otherwise stores offset on the stack instead of in a register.
 179          */
 180         if (unlikely(desc->len < dev->vhost_hlen) || !desc_addr)
 181                 return -1;
 182
 183         rte_prefetch0((void *)(uintptr_t)desc_addr);
 184
 185         virtio_enqueue_offload(m, (struct virtio_net_hdr *)(uintptr_t)desc_addr);
 186         vhost_log_write(dev, desc->addr, dev->vhost_hlen);
 187         PRINT_PACKET(dev, (uintptr_t)desc_addr, dev->vhost_hlen, 0);
 188
 189         desc_offset = dev->vhost_hlen;
 190         desc_avail  = desc->len - dev->vhost_hlen;
 191
 192         mbuf_avail  = rte_pktmbuf_data_len(m);
 193         mbuf_offset = 0;
 194         while (mbuf_avail != 0 || m->next != NULL) {
 195                 /* done with current mbuf, fetch next */
 196                 if (mbuf_avail == 0) {
 197                         m = m->next;
 198
 199                         mbuf_offset = 0;
 200                         mbuf_avail  = rte_pktmbuf_data_len(m);
 201                 }
 202
 203                 /* done with current desc buf, fetch next */
 204                 if (desc_avail == 0) {
 205                         if ((desc->flags & VRING_DESC_F_NEXT) == 0) {
 206                                 /* Room in vring buffer is not enough */
 207                                 return -1;
 208                         }
 209                         if (unlikely(desc->next >= size || ++nr_desc > size))
 210                                 return -1;
 211
 212                         desc = &descs[desc->next];
 213                         desc_addr = rte_vhost_gpa_to_vva(dev->mem, desc->addr);
 214                         if (unlikely(!desc_addr))
 215                                 return -1;
 216
 217                         desc_offset = 0;
 218                         desc_avail  = desc->len;
 219                 }
 220
 221                 cpy_len = RTE_MIN(desc_avail, mbuf_avail);
 222                 rte_memcpy((void *)((uintptr_t)(desc_addr + desc_offset)),
 223                         rte_pktmbuf_mtod_offset(m, void *, mbuf_offset),
 224                         cpy_len);
 225                 vhost_log_write(dev, desc->addr + desc_offset, cpy_len);
 226                 PRINT_PACKET(dev, (uintptr_t)(desc_addr + desc_offset),
 227                              cpy_len, 0);
 228
 229                 mbuf_avail  -= cpy_len;
 230                 mbuf_offset += cpy_len;
 231                 desc_avail  -= cpy_len;
 232                 desc_offset += cpy_len;
 233         }
 234
 235         return 0;
 236 }
 237
 238 /**
 239  * This function adds buffers to the virtio devices RX virtqueue. Buffers can
 240  * be received from the physical port or from another virtio device. A packet
 241  * count is returned to indicate the number of packets that are successfully
 242  * added to the RX queue. This function works when the mbuf is scattered, but
 243  * it doesn't support the mergeable feature.
 244  */
 245 static __rte_always_inline uint32_t
 246 virtio_dev_rx(struct virtio_net *dev, uint16_t queue_id,
 247               struct rte_mbuf **pkts, uint32_t count)
 248 {
 249         struct vhost_virtqueue *vq;
 250         uint16_t avail_idx, free_entries, start_idx;
 251         uint16_t desc_indexes[MAX_PKT_BURST];
 252         struct vring_desc *descs;
 253         uint16_t used_idx;
 254         uint32_t i, sz;
 255
 256         LOG_DEBUG(VHOST_DATA, "(%d) %s\n", dev->vid, __func__);
 257         if (unlikely(!is_valid_virt_queue_idx(queue_id, 0, dev->nr_vring))) {
 258                 RTE_LOG(ERR, VHOST_DATA, "(%d) %s: invalid virtqueue idx %d.\n",
 259                         dev->vid, __func__, queue_id);
 260                 return 0;
 261         }
 262
 263         vq = dev->virtqueue[queue_id];
 264         if (unlikely(vq->enabled == 0))
 265                 return 0;
 266
 267         avail_idx = *((volatile uint16_t *)&vq->avail->idx);
 268         start_idx = vq->last_used_idx;
 269         free_entries = avail_idx - start_idx;
 270         count = RTE_MIN(count, free_entries);
 271         count = RTE_MIN(count, (uint32_t)MAX_PKT_BURST);
 272         if (count == 0)
 273                 return 0;
 274
 275         LOG_DEBUG(VHOST_DATA, "(%d) start_idx %d | end_idx %d\n",
 276                 dev->vid, start_idx, start_idx + count);
 277
 278         /* Retrieve all of the desc indexes first to avoid caching issues. */
 279         rte_prefetch0(&vq->avail->ring[start_idx & (vq->size - 1)]);
 280         for (i = 0; i < count; i++) {
 281                 used_idx = (start_idx + i) & (vq->size - 1);
 282                 desc_indexes[i] = vq->avail->ring[used_idx];
 283                 vq->used->ring[used_idx].id = desc_indexes[i];
 284                 vq->used->ring[used_idx].len = pkts[i]->pkt_len +
 285                                                dev->vhost_hlen;
 286                 vhost_log_used_vring(dev, vq,
 287                         offsetof(struct vring_used, ring[used_idx]),
 288                         sizeof(vq->used->ring[used_idx]));
 289         }
 290
 291         rte_prefetch0(&vq->desc[desc_indexes[0]]);
 292         for (i = 0; i < count; i++) {
 293                 uint16_t desc_idx = desc_indexes[i];
 294                 int err;
 295
 296                 if (vq->desc[desc_idx].flags & VRING_DESC_F_INDIRECT) {
 297                         descs = (struct vring_desc *)(uintptr_t)
 298                                 rte_vhost_gpa_to_vva(dev->mem,
 299                                         vq->desc[desc_idx].addr);
 300                         if (unlikely(!descs)) {
 301                                 count = i;
 302                                 break;
 303                         }
 304
 305                         desc_idx = 0;
 306                         sz = vq->desc[desc_idx].len / sizeof(*descs);
 307                 } else {
 308                         descs = vq->desc;
 309                         sz = vq->size;
 310                 }
 311
 312                 err = copy_mbuf_to_desc(dev, descs, pkts[i], desc_idx, sz);
 313                 if (unlikely(err)) {
 314                         used_idx = (start_idx + i) & (vq->size - 1);
 315                         vq->used->ring[used_idx].len = dev->vhost_hlen;
 316                         vhost_log_used_vring(dev, vq,
 317                                 offsetof(struct vring_used, ring[used_idx]),
 318                                 sizeof(vq->used->ring[used_idx]));
 319                 }
 320
 321                 if (i + 1 < count)
 322                         rte_prefetch0(&vq->desc[desc_indexes[i+1]]);
 323         }
 324
 325         rte_smp_wmb();
 326
 327         *(volatile uint16_t *)&vq->used->idx += count;
 328         vq->last_used_idx += count;
 329         vhost_log_used_vring(dev, vq,
 330                 offsetof(struct vring_used, idx),
 331                 sizeof(vq->used->idx));
 332
 333         /* flush used->idx update before we read avail->flags. */
 334         rte_mb();
 335
 336         /* Kick the guest if necessary. */
 337         if (!(vq->avail->flags & VRING_AVAIL_F_NO_INTERRUPT)
 338                         && (vq->callfd >= 0))
 339                 eventfd_write(vq->callfd, (eventfd_t)1);
 340         return count;
 341 }
 342
 343 static __rte_always_inline int
 344 fill_vec_buf(struct virtio_net *dev, struct vhost_virtqueue *vq,
 345                          uint32_t avail_idx, uint32_t *vec_idx,
 346                          struct buf_vector *buf_vec, uint16_t *desc_chain_head,
 347                          uint16_t *desc_chain_len)
 348 {
 349         uint16_t idx = vq->avail->ring[avail_idx & (vq->size - 1)];
 350         uint32_t vec_id = *vec_idx;
 351         uint32_t len    = 0;
 352         struct vring_desc *descs = vq->desc;
 353
 354         *desc_chain_head = idx;
 355
 356         if (vq->desc[idx].flags & VRING_DESC_F_INDIRECT) {
 357                 descs = (struct vring_desc *)(uintptr_t)
 358                         rte_vhost_gpa_to_vva(dev->mem, vq->desc[idx].addr);
 359                 if (unlikely(!descs))
 360                         return -1;
 361
 362                 idx = 0;
 363         }
 364
 365         while (1) {
 366                 if (unlikely(vec_id >= BUF_VECTOR_MAX || idx >= vq->size))
 367                         return -1;
 368
 369                 len += descs[idx].len;
 370                 buf_vec[vec_id].buf_addr = descs[idx].addr;
 371                 buf_vec[vec_id].buf_len  = descs[idx].len;
 372                 buf_vec[vec_id].desc_idx = idx;
 373                 vec_id++;
 374
 375                 if ((descs[idx].flags & VRING_DESC_F_NEXT) == 0)
 376                         break;
 377
 378                 idx = descs[idx].next;
 379         }
 380
 381         *desc_chain_len = len;
 382         *vec_idx = vec_id;
 383
 384         return 0;
 385 }
 386
 387 /*
 388  * Returns -1 on fail, 0 on success
 389  */
 390 static inline int
 391 reserve_avail_buf_mergeable(struct virtio_net *dev, struct vhost_virtqueue *vq,
 392                                 uint32_t size, struct buf_vector *buf_vec,
 393                                 uint16_t *num_buffers, uint16_t avail_head)
 394 {
 395         uint16_t cur_idx;
 396         uint32_t vec_idx = 0;
 397         uint16_t tries = 0;
 398
 399         uint16_t head_idx = 0;
 400         uint16_t len = 0;
 401
 402         *num_buffers = 0;
 403         cur_idx  = vq->last_avail_idx;
 404
 405         while (size > 0) {
 406                 if (unlikely(cur_idx == avail_head))
 407                         return -1;
 408
 409                 if (unlikely(fill_vec_buf(dev, vq, cur_idx, &vec_idx, buf_vec,
 410                                                 &head_idx, &len) < 0))
 411                         return -1;
 412                 len = RTE_MIN(len, size);
 413                 update_shadow_used_ring(vq, head_idx, len);
 414                 size -= len;
 415
 416                 cur_idx++;
 417                 tries++;
 418                 *num_buffers += 1;
 419
 420                 /*
 421                  * if we tried all available ring items, and still
 422                  * can't get enough buf, it means something abnormal
 423                  * happened.
 424                  */
 425                 if (unlikely(tries >= vq->size))
 426                         return -1;
 427         }
 428
 429         return 0;
 430 }
 431
 432 static __rte_always_inline int
 433 copy_mbuf_to_desc_mergeable(struct virtio_net *dev, struct rte_mbuf *m,
 434                             struct buf_vector *buf_vec, uint16_t num_buffers)
 435 {
 436         uint32_t vec_idx = 0;
 437         uint64_t desc_addr;
 438         uint32_t mbuf_offset, mbuf_avail;
 439         uint32_t desc_offset, desc_avail;
 440         uint32_t cpy_len;
 441         uint64_t hdr_addr, hdr_phys_addr;
 442         struct rte_mbuf *hdr_mbuf;
 443
 444         if (unlikely(m == NULL))
 445                 return -1;
 446
 447         desc_addr = rte_vhost_gpa_to_vva(dev->mem, buf_vec[vec_idx].buf_addr);
 448         if (buf_vec[vec_idx].buf_len < dev->vhost_hlen || !desc_addr)
 449                 return -1;
 450
 451         hdr_mbuf = m;
 452         hdr_addr = desc_addr;
 453         hdr_phys_addr = buf_vec[vec_idx].buf_addr;
 454         rte_prefetch0((void *)(uintptr_t)hdr_addr);
 455
 456         LOG_DEBUG(VHOST_DATA, "(%d) RX: num merge buffers %d\n",
 457                 dev->vid, num_buffers);
 458
 459         desc_avail  = buf_vec[vec_idx].buf_len - dev->vhost_hlen;
 460         desc_offset = dev->vhost_hlen;
 461
 462         mbuf_avail  = rte_pktmbuf_data_len(m);
 463         mbuf_offset = 0;
 464         while (mbuf_avail != 0 || m->next != NULL) {
 465                 /* done with current desc buf, get the next one */
 466                 if (desc_avail == 0) {
 467                         vec_idx++;
 468                         desc_addr = rte_vhost_gpa_to_vva(dev->mem,
 469                                         buf_vec[vec_idx].buf_addr);
 470                         if (unlikely(!desc_addr))
 471                                 return -1;
 472
 473                         /* Prefetch buffer address. */
 474                         rte_prefetch0((void *)(uintptr_t)desc_addr);
 475                         desc_offset = 0;
 476                         desc_avail  = buf_vec[vec_idx].buf_len;
 477                 }
 478
 479                 /* done with current mbuf, get the next one */
 480                 if (mbuf_avail == 0) {
 481                         m = m->next;
 482
 483                         mbuf_offset = 0;
 484                         mbuf_avail  = rte_pktmbuf_data_len(m);
 485                 }
 486
 487                 if (hdr_addr) {
 488                         struct virtio_net_hdr_mrg_rxbuf *hdr;
 489
 490                         hdr = (struct virtio_net_hdr_mrg_rxbuf *)(uintptr_t)
 491                                 hdr_addr;
 492                         virtio_enqueue_offload(hdr_mbuf, &hdr->hdr);
 493                         ASSIGN_UNLESS_EQUAL(hdr->num_buffers, num_buffers);
 494
 495                         vhost_log_write(dev, hdr_phys_addr, dev->vhost_hlen);
 496                         PRINT_PACKET(dev, (uintptr_t)hdr_addr,
 497                                      dev->vhost_hlen, 0);
 498
 499                         hdr_addr = 0;
 500                 }
 501
 502                 cpy_len = RTE_MIN(desc_avail, mbuf_avail);
 503                 rte_memcpy((void *)((uintptr_t)(desc_addr + desc_offset)),
 504                         rte_pktmbuf_mtod_offset(m, void *, mbuf_offset),
 505                         cpy_len);
 506                 vhost_log_write(dev, buf_vec[vec_idx].buf_addr + desc_offset,
 507                         cpy_len);
 508                 PRINT_PACKET(dev, (uintptr_t)(desc_addr + desc_offset),
 509                         cpy_len, 0);
 510
 511                 mbuf_avail  -= cpy_len;
 512                 mbuf_offset += cpy_len;
 513                 desc_avail  -= cpy_len;
 514                 desc_offset += cpy_len;
 515         }
 516
 517         return 0;
 518 }
 519
 520 static __rte_always_inline uint32_t
 521 virtio_dev_merge_rx(struct virtio_net *dev, uint16_t queue_id,
 522         struct rte_mbuf **pkts, uint32_t count)
 523 {
 524         struct vhost_virtqueue *vq;
 525         uint32_t pkt_idx = 0;
 526         uint16_t num_buffers;
 527         struct buf_vector buf_vec[BUF_VECTOR_MAX];
 528         uint16_t avail_head;
 529
 530         LOG_DEBUG(VHOST_DATA, "(%d) %s\n", dev->vid, __func__);
 531         if (unlikely(!is_valid_virt_queue_idx(queue_id, 0, dev->nr_vring))) {
 532                 RTE_LOG(ERR, VHOST_DATA, "(%d) %s: invalid virtqueue idx %d.\n",
 533                         dev->vid, __func__, queue_id);
 534                 return 0;
 535         }
 536
 537         vq = dev->virtqueue[queue_id];
 538         if (unlikely(vq->enabled == 0))
 539                 return 0;
 540
 541         count = RTE_MIN((uint32_t)MAX_PKT_BURST, count);
 542         if (count == 0)
 543                 return 0;
 544
 545         rte_prefetch0(&vq->avail->ring[vq->last_avail_idx & (vq->size - 1)]);
 546
 547         vq->shadow_used_idx = 0;
 548         avail_head = *((volatile uint16_t *)&vq->avail->idx);
 549         for (pkt_idx = 0; pkt_idx < count; pkt_idx++) {
 550                 uint32_t pkt_len = pkts[pkt_idx]->pkt_len + dev->vhost_hlen;
 551
 552                 if (unlikely(reserve_avail_buf_mergeable(dev, vq,
 553                                                 pkt_len, buf_vec, &num_buffers,
 554                                                 avail_head) < 0)) {
 555                         LOG_DEBUG(VHOST_DATA,
 556                                 "(%d) failed to get enough desc from vring\n",
 557                                 dev->vid);
 558                         vq->shadow_used_idx -= num_buffers;
 559                         break;
 560                 }
 561
 562                 LOG_DEBUG(VHOST_DATA, "(%d) current index %d | end index %d\n",
 563                         dev->vid, vq->last_avail_idx,
 564                         vq->last_avail_idx + num_buffers);
 565
 566                 if (copy_mbuf_to_desc_mergeable(dev, pkts[pkt_idx],
 567                                                 buf_vec, num_buffers) < 0) {
 568                         vq->shadow_used_idx -= num_buffers;
 569                         break;
 570                 }
 571
 572                 vq->last_avail_idx += num_buffers;
 573         }
 574
 575         if (likely(vq->shadow_used_idx)) {
 576                 flush_shadow_used_ring(dev, vq);
 577
 578                 /* flush used->idx update before we read avail->flags. */
 579                 rte_mb();
 580
 581                 /* Kick the guest if necessary. */
 582                 if (!(vq->avail->flags & VRING_AVAIL_F_NO_INTERRUPT)
 583                                 && (vq->callfd >= 0))
 584                         eventfd_write(vq->callfd, (eventfd_t)1);
 585         }
 586
 587         return pkt_idx;
 588 }
 589
 590 uint16_t
 591 rte_vhost_enqueue_burst(int vid, uint16_t queue_id,
 592         struct rte_mbuf **pkts, uint16_t count)
 593 {
 594         struct virtio_net *dev = get_device(vid);
 595
 596         if (!dev)
 597                 return 0;
 598
 599         if (dev->features & (1 << VIRTIO_NET_F_MRG_RXBUF))
 600                 return virtio_dev_merge_rx(dev, queue_id, pkts, count);
 601         else
 602                 return virtio_dev_rx(dev, queue_id, pkts, count);
 603 }
 604
 605 static inline bool
 606 virtio_net_with_host_offload(struct virtio_net *dev)
 607 {
 608         if (dev->features &
 609                         (VIRTIO_NET_F_CSUM | VIRTIO_NET_F_HOST_ECN |
 610                          VIRTIO_NET_F_HOST_TSO4 | VIRTIO_NET_F_HOST_TSO6 |
 611                          VIRTIO_NET_F_HOST_UFO))
 612                 return true;
 613
 614         return false;
 615 }
 616
 617 static void
 618 parse_ethernet(struct rte_mbuf *m, uint16_t *l4_proto, void **l4_hdr)
 619 {
 620         struct ipv4_hdr *ipv4_hdr;
 621         struct ipv6_hdr *ipv6_hdr;
 622         void *l3_hdr = NULL;
 623         struct ether_hdr *eth_hdr;
 624         uint16_t ethertype;
 625
 626         eth_hdr = rte_pktmbuf_mtod(m, struct ether_hdr *);
 627
 628         m->l2_len = sizeof(struct ether_hdr);
 629         ethertype = rte_be_to_cpu_16(eth_hdr->ether_type);
 630
 631         if (ethertype == ETHER_TYPE_VLAN) {
 632                 struct vlan_hdr *vlan_hdr = (struct vlan_hdr *)(eth_hdr + 1);
 633
 634                 m->l2_len += sizeof(struct vlan_hdr);
 635                 ethertype = rte_be_to_cpu_16(vlan_hdr->eth_proto);
 636         }
 637
 638         l3_hdr = (char *)eth_hdr + m->l2_len;
 639
 640         switch (ethertype) {
 641         case ETHER_TYPE_IPv4:
 642                 ipv4_hdr = l3_hdr;
 643                 *l4_proto = ipv4_hdr->next_proto_id;
 644                 m->l3_len = (ipv4_hdr->version_ihl & 0x0f) * 4;
 645                 *l4_hdr = (char *)l3_hdr + m->l3_len;
 646                 m->ol_flags |= PKT_TX_IPV4;
 647                 break;
 648         case ETHER_TYPE_IPv6:
 649                 ipv6_hdr = l3_hdr;
 650                 *l4_proto = ipv6_hdr->proto;
 651                 m->l3_len = sizeof(struct ipv6_hdr);
 652                 *l4_hdr = (char *)l3_hdr + m->l3_len;
 653                 m->ol_flags |= PKT_TX_IPV6;
 654                 break;
 655         default:
 656                 m->l3_len = 0;
 657                 *l4_proto = 0;
 658                 *l4_hdr = NULL;
 659                 break;
 660         }
 661 }
 662
 663 static __rte_always_inline void
 664 vhost_dequeue_offload(struct virtio_net_hdr *hdr, struct rte_mbuf *m)
 665 {
 666         uint16_t l4_proto = 0;
 667         void *l4_hdr = NULL;
 668         struct tcp_hdr *tcp_hdr = NULL;
 669
 670         if (hdr->flags == 0 && hdr->gso_type == VIRTIO_NET_HDR_GSO_NONE)
 671                 return;
 672
 673         parse_ethernet(m, &l4_proto, &l4_hdr);
 674         if (hdr->flags == VIRTIO_NET_HDR_F_NEEDS_CSUM) {
 675                 if (hdr->csum_start == (m->l2_len + m->l3_len)) {
 676                         switch (hdr->csum_offset) {
 677                         case (offsetof(struct tcp_hdr, cksum)):
 678                                 if (l4_proto == IPPROTO_TCP)
 679                                         m->ol_flags |= PKT_TX_TCP_CKSUM;
 680                                 break;
 681                         case (offsetof(struct udp_hdr, dgram_cksum)):
 682                                 if (l4_proto == IPPROTO_UDP)
 683                                         m->ol_flags |= PKT_TX_UDP_CKSUM;
 684                                 break;
 685                         case (offsetof(struct sctp_hdr, cksum)):
 686                                 if (l4_proto == IPPROTO_SCTP)
 687                                         m->ol_flags |= PKT_TX_SCTP_CKSUM;
 688                                 break;
 689                         default:
 690                                 break;
 691                         }
 692                 }
 693         }
 694
 695         if (l4_hdr && hdr->gso_type != VIRTIO_NET_HDR_GSO_NONE) {
 696                 switch (hdr->gso_type & ~VIRTIO_NET_HDR_GSO_ECN) {
 697                 case VIRTIO_NET_HDR_GSO_TCPV4:
 698                 case VIRTIO_NET_HDR_GSO_TCPV6:
 699                         tcp_hdr = l4_hdr;
 700                         m->ol_flags |= PKT_TX_TCP_SEG;
 701                         m->tso_segsz = hdr->gso_size;
 702                         m->l4_len = (tcp_hdr->data_off & 0xf0) >> 2;
 703                         break;
 704                 default:
 705                         RTE_LOG(WARNING, VHOST_DATA,
 706                                 "unsupported gso type %u.\n", hdr->gso_type);
 707                         break;
 708                 }
 709         }
 710 }
 711
 712 #define RARP_PKT_SIZE   64
 713
 714 static int
 715 make_rarp_packet(struct rte_mbuf *rarp_mbuf, const struct ether_addr *mac)
 716 {
 717         struct ether_hdr *eth_hdr;
 718         struct arp_hdr  *rarp;
 719
 720         if (rarp_mbuf->buf_len < 64) {
 721                 RTE_LOG(WARNING, VHOST_DATA,
 722                         "failed to make RARP; mbuf size too small %u (< %d)\n",
 723                         rarp_mbuf->buf_len, RARP_PKT_SIZE);
 724                 return -1;
 725         }
 726
 727         /* Ethernet header. */
 728         eth_hdr = rte_pktmbuf_mtod_offset(rarp_mbuf, struct ether_hdr *, 0);
 729         memset(eth_hdr->d_addr.addr_bytes, 0xff, ETHER_ADDR_LEN);
 730         ether_addr_copy(mac, &eth_hdr->s_addr);
 731         eth_hdr->ether_type = htons(ETHER_TYPE_RARP);
 732
 733         /* RARP header. */
 734         rarp = (struct arp_hdr *)(eth_hdr + 1);
 735         rarp->arp_hrd = htons(ARP_HRD_ETHER);
 736         rarp->arp_pro = htons(ETHER_TYPE_IPv4);
 737         rarp->arp_hln = ETHER_ADDR_LEN;
 738         rarp->arp_pln = 4;
 739         rarp->arp_op  = htons(ARP_OP_REVREQUEST);
 740
 741         ether_addr_copy(mac, &rarp->arp_data.arp_sha);
 742         ether_addr_copy(mac, &rarp->arp_data.arp_tha);
 743         memset(&rarp->arp_data.arp_sip, 0x00, 4);
 744         memset(&rarp->arp_data.arp_tip, 0x00, 4);
 745
 746         rarp_mbuf->pkt_len  = rarp_mbuf->data_len = RARP_PKT_SIZE;
 747
 748         return 0;
 749 }
 750
 751 static __rte_always_inline void
 752 put_zmbuf(struct zcopy_mbuf *zmbuf)
 753 {
 754         zmbuf->in_use = 0;
 755 }
 756
 757 static __rte_always_inline int
 758 copy_desc_to_mbuf(struct virtio_net *dev, struct vring_desc *descs,
 759                   uint16_t max_desc, struct rte_mbuf *m, uint16_t desc_idx,
 760                   struct rte_mempool *mbuf_pool)
 761 {
 762         struct vring_desc *desc;
 763         uint64_t desc_addr;
 764         uint32_t desc_avail, desc_offset;
 765         uint32_t mbuf_avail, mbuf_offset;
 766         uint32_t cpy_len;
 767         struct rte_mbuf *cur = m, *prev = m;
 768         struct virtio_net_hdr *hdr = NULL;
 769         /* A counter to avoid desc dead loop chain */
 770         uint32_t nr_desc = 1;
 771
 772         desc = &descs[desc_idx];
 773         if (unlikely((desc->len < dev->vhost_hlen)) ||
 774                         (desc->flags & VRING_DESC_F_INDIRECT))
 775                 return -1;
 776
 777         desc_addr = rte_vhost_gpa_to_vva(dev->mem, desc->addr);
 778         if (unlikely(!desc_addr))
 779                 return -1;
 780
 781         if (virtio_net_with_host_offload(dev)) {
 782                 hdr = (struct virtio_net_hdr *)((uintptr_t)desc_addr);
 783                 rte_prefetch0(hdr);
 784         }
 785
 786         /*
 787          * A virtio driver normally uses at least 2 desc buffers
 788          * for Tx: the first for storing the header, and others
 789          * for storing the data.
 790          */
 791         if (likely((desc->len == dev->vhost_hlen) &&
 792                    (desc->flags & VRING_DESC_F_NEXT) != 0)) {
 793                 desc = &descs[desc->next];
 794                 if (unlikely(desc->flags & VRING_DESC_F_INDIRECT))
 795                         return -1;
 796
 797                 desc_addr = rte_vhost_gpa_to_vva(dev->mem, desc->addr);
 798                 if (unlikely(!desc_addr))
 799                         return -1;
 800
 801                 desc_offset = 0;
 802                 desc_avail  = desc->len;
 803                 nr_desc    += 1;
 804         } else {
 805                 desc_avail  = desc->len - dev->vhost_hlen;
 806                 desc_offset = dev->vhost_hlen;
 807         }
 808
 809         rte_prefetch0((void *)(uintptr_t)(desc_addr + desc_offset));
 810
 811         PRINT_PACKET(dev, (uintptr_t)(desc_addr + desc_offset), desc_avail, 0);
 812
 813         mbuf_offset = 0;
 814         mbuf_avail  = m->buf_len - RTE_PKTMBUF_HEADROOM;
 815         while (1) {
 816                 uint64_t hpa;
 817
 818                 cpy_len = RTE_MIN(desc_avail, mbuf_avail);
 819
 820                 /*
 821                  * A desc buf might across two host physical pages that are
 822                  * not continuous. In such case (gpa_to_hpa returns 0), data
 823                  * will be copied even though zero copy is enabled.
 824                  */
 825                 if (unlikely(dev->dequeue_zero_copy && (hpa = gpa_to_hpa(dev,
 826                                         desc->addr + desc_offset, cpy_len)))) {
 827                         cur->data_len = cpy_len;
 828                         cur->data_off = 0;
 829                         cur->buf_addr = (void *)(uintptr_t)desc_addr;
 830                         cur->buf_physaddr = hpa;
 831
 832                         /*
 833                          * In zero copy mode, one mbuf can only reference data
 834                          * for one or partial of one desc buff.
 835                          */
 836                         mbuf_avail = cpy_len;
 837                 } else {
 838                         rte_memcpy(rte_pktmbuf_mtod_offset(cur, void *,
 839                                                            mbuf_offset),
 840                                 (void *)((uintptr_t)(desc_addr + desc_offset)),
 841                                 cpy_len);
 842                 }
 843
 844                 mbuf_avail  -= cpy_len;
 845                 mbuf_offset += cpy_len;
 846                 desc_avail  -= cpy_len;
 847                 desc_offset += cpy_len;
 848
 849                 /* This desc reaches to its end, get the next one */
 850                 if (desc_avail == 0) {
 851                         if ((desc->flags & VRING_DESC_F_NEXT) == 0)
 852                                 break;
 853
 854                         if (unlikely(desc->next >= max_desc ||
 855                                      ++nr_desc > max_desc))
 856                                 return -1;
 857                         desc = &descs[desc->next];
 858                         if (unlikely(desc->flags & VRING_DESC_F_INDIRECT))
 859                                 return -1;
 860
 861                         desc_addr = rte_vhost_gpa_to_vva(dev->mem, desc->addr);
 862                         if (unlikely(!desc_addr))
 863                                 return -1;
 864
 865                         rte_prefetch0((void *)(uintptr_t)desc_addr);
 866
 867                         desc_offset = 0;
 868                         desc_avail  = desc->len;
 869
 870                         PRINT_PACKET(dev, (uintptr_t)desc_addr, desc->len, 0);
 871                 }
 872
 873                 /*
 874                  * This mbuf reaches to its end, get a new one
 875                  * to hold more data.
 876                  */
 877                 if (mbuf_avail == 0) {
 878                         cur = rte_pktmbuf_alloc(mbuf_pool);
 879                         if (unlikely(cur == NULL)) {
 880                                 RTE_LOG(ERR, VHOST_DATA, "Failed to "
 881                                         "allocate memory for mbuf.\n");
 882                                 return -1;
 883                         }
 884                         if (unlikely(dev->dequeue_zero_copy))
 885                                 rte_mbuf_refcnt_update(cur, 1);
 886
 887                         prev->next = cur;
 888                         prev->data_len = mbuf_offset;
 889                         m->nb_segs += 1;
 890                         m->pkt_len += mbuf_offset;
 891                         prev = cur;
 892
 893                         mbuf_offset = 0;
 894                         mbuf_avail  = cur->buf_len - RTE_PKTMBUF_HEADROOM;
 895                 }
 896         }
 897
 898         prev->data_len = mbuf_offset;
 899         m->pkt_len    += mbuf_offset;
 900
 901         if (hdr)
 902                 vhost_dequeue_offload(hdr, m);
 903
 904         return 0;
 905 }
 906
 907 static __rte_always_inline void
 908 update_used_ring(struct virtio_net *dev, struct vhost_virtqueue *vq,
 909                  uint32_t used_idx, uint32_t desc_idx)
 910 {
 911         vq->used->ring[used_idx].id  = desc_idx;
 912         vq->used->ring[used_idx].len = 0;
 913         vhost_log_used_vring(dev, vq,
 914                         offsetof(struct vring_used, ring[used_idx]),
 915                         sizeof(vq->used->ring[used_idx]));
 916 }
 917
 918 static __rte_always_inline void
 919 update_used_idx(struct virtio_net *dev, struct vhost_virtqueue *vq,
 920                 uint32_t count)
 921 {
 922         if (unlikely(count == 0))
 923                 return;
 924
 925         rte_smp_wmb();
 926         rte_smp_rmb();
 927
 928         vq->used->idx += count;
 929         vhost_log_used_vring(dev, vq, offsetof(struct vring_used, idx),
 930                         sizeof(vq->used->idx));
 931
 932         /* Kick guest if required. */
 933         if (!(vq->avail->flags & VRING_AVAIL_F_NO_INTERRUPT)
 934                         && (vq->callfd >= 0))
 935                 eventfd_write(vq->callfd, (eventfd_t)1);
 936 }
 937
 938 static __rte_always_inline struct zcopy_mbuf *
 939 get_zmbuf(struct vhost_virtqueue *vq)
 940 {
 941         uint16_t i;
 942         uint16_t last;
 943         int tries = 0;
 944
 945         /* search [last_zmbuf_idx, zmbuf_size) */
 946         i = vq->last_zmbuf_idx;
 947         last = vq->zmbuf_size;
 948
 949 again:
 950         for (; i < last; i++) {
 951                 if (vq->zmbufs[i].in_use == 0) {
 952                         vq->last_zmbuf_idx = i + 1;
 953                         vq->zmbufs[i].in_use = 1;
 954                         return &vq->zmbufs[i];
 955                 }
 956         }
 957
 958         tries++;
 959         if (tries == 1) {
 960                 /* search [0, last_zmbuf_idx) */
 961                 i = 0;
 962                 last = vq->last_zmbuf_idx;
 963                 goto again;
 964         }
 965
 966         return NULL;
 967 }
 968
 969 static __rte_always_inline bool
 970 mbuf_is_consumed(struct rte_mbuf *m)
 971 {
 972         while (m) {
 973                 if (rte_mbuf_refcnt_read(m) > 1)
 974                         return false;
 975                 m = m->next;
 976         }
 977
 978         return true;
 979 }
 980
 981 uint16_t
 982 rte_vhost_dequeue_burst(int vid, uint16_t queue_id,
 983         struct rte_mempool *mbuf_pool, struct rte_mbuf **pkts, uint16_t count)
 984 {
 985         struct virtio_net *dev;
 986         struct rte_mbuf *rarp_mbuf = NULL;
 987         struct vhost_virtqueue *vq;
 988         uint32_t desc_indexes[MAX_PKT_BURST];
 989         uint32_t used_idx;
 990         uint32_t i = 0;
 991         uint16_t free_entries;
 992         uint16_t avail_idx;
 993
 994         dev = get_device(vid);
 995         if (!dev)
 996                 return 0;
 997
 998         if (unlikely(!is_valid_virt_queue_idx(queue_id, 1, dev->nr_vring))) {
 999                 RTE_LOG(ERR, VHOST_DATA, "(%d) %s: invalid virtqueue idx %d.\n",
1000                         dev->vid, __func__, queue_id);
1001                 return 0;
1002         }
1003
1004         vq = dev->virtqueue[queue_id];
1005         if (unlikely(vq->enabled == 0))
1006                 return 0;
1007
1008         if (unlikely(dev->dequeue_zero_copy)) {
1009                 struct zcopy_mbuf *zmbuf, *next;
1010                 int nr_updated = 0;
1011
1012                 for (zmbuf = TAILQ_FIRST(&vq->zmbuf_list);
1013                      zmbuf != NULL; zmbuf = next) {
1014                         next = TAILQ_NEXT(zmbuf, next);
1015
1016                         if (mbuf_is_consumed(zmbuf->mbuf)) {
1017                                 used_idx = vq->last_used_idx++ & (vq->size - 1);
1018                                 update_used_ring(dev, vq, used_idx,
1019                                                  zmbuf->desc_idx);
1020                                 nr_updated += 1;
1021
1022                                 TAILQ_REMOVE(&vq->zmbuf_list, zmbuf, next);
1023                                 rte_pktmbuf_free(zmbuf->mbuf);
1024                                 put_zmbuf(zmbuf);
1025                                 vq->nr_zmbuf -= 1;
1026                         }
1027                 }
1028
1029                 update_used_idx(dev, vq, nr_updated);
1030         }
1031
1032         /*
1033          * Construct a RARP broadcast packet, and inject it to the "pkts"
1034          * array, to looks like that guest actually send such packet.
1035          *
1036          * Check user_send_rarp() for more information.
1037          *
1038          * broadcast_rarp shares a cacheline in the virtio_net structure
1039          * with some fields that are accessed during enqueue and
1040          * rte_atomic16_cmpset() causes a write if using cmpxchg. This could
1041          * result in false sharing between enqueue and dequeue.
1042          *
1043          * Prevent unnecessary false sharing by reading broadcast_rarp first
1044          * and only performing cmpset if the read indicates it is likely to
1045          * be set.
1046          */
1047
1048         if (unlikely(rte_atomic16_read(&dev->broadcast_rarp) &&
1049                         rte_atomic16_cmpset((volatile uint16_t *)
1050                                 &dev->broadcast_rarp.cnt, 1, 0))) {
1051
1052                 rarp_mbuf = rte_pktmbuf_alloc(mbuf_pool);
1053                 if (rarp_mbuf == NULL) {
1054                         RTE_LOG(ERR, VHOST_DATA,
1055                                 "Failed to allocate memory for mbuf.\n");
1056                         return 0;
1057                 }
1058
1059                 if (make_rarp_packet(rarp_mbuf, &dev->mac)) {
1060                         rte_pktmbuf_free(rarp_mbuf);
1061                         rarp_mbuf = NULL;
1062                 } else {
1063                         count -= 1;
1064                 }
1065         }
1066
1067         free_entries = *((volatile uint16_t *)&vq->avail->idx) -
1068                         vq->last_avail_idx;
1069         if (free_entries == 0)
1070                 goto out;
1071
1072         LOG_DEBUG(VHOST_DATA, "(%d) %s\n", dev->vid, __func__);
1073
1074         /* Prefetch available and used ring */
1075         avail_idx = vq->last_avail_idx & (vq->size - 1);
1076         used_idx  = vq->last_used_idx  & (vq->size - 1);
1077         rte_prefetch0(&vq->avail->ring[avail_idx]);
1078         rte_prefetch0(&vq->used->ring[used_idx]);
1079
1080         count = RTE_MIN(count, MAX_PKT_BURST);
1081         count = RTE_MIN(count, free_entries);
1082         LOG_DEBUG(VHOST_DATA, "(%d) about to dequeue %u buffers\n",
1083                         dev->vid, count);
1084
1085         /* Retrieve all of the head indexes first to avoid caching issues. */
1086         for (i = 0; i < count; i++) {
1087                 avail_idx = (vq->last_avail_idx + i) & (vq->size - 1);
1088                 used_idx  = (vq->last_used_idx  + i) & (vq->size - 1);
1089                 desc_indexes[i] = vq->avail->ring[avail_idx];
1090
1091                 if (likely(dev->dequeue_zero_copy == 0))
1092                         update_used_ring(dev, vq, used_idx, desc_indexes[i]);
1093         }
1094
1095         /* Prefetch descriptor index. */
1096         rte_prefetch0(&vq->desc[desc_indexes[0]]);
1097         for (i = 0; i < count; i++) {
1098                 struct vring_desc *desc;
1099                 uint16_t sz, idx;
1100                 int err;
1101
1102                 if (likely(i + 1 < count))
1103                         rte_prefetch0(&vq->desc[desc_indexes[i + 1]]);
1104
1105                 if (vq->desc[desc_indexes[i]].flags & VRING_DESC_F_INDIRECT) {
1106                         desc = (struct vring_desc *)(uintptr_t)
1107                                 rte_vhost_gpa_to_vva(dev->mem,
1108                                         vq->desc[desc_indexes[i]].addr);
1109                         if (unlikely(!desc))
1110                                 break;
1111
1112                         rte_prefetch0(desc);
1113                         sz = vq->desc[desc_indexes[i]].len / sizeof(*desc);
1114                         idx = 0;
1115                 } else {
1116                         desc = vq->desc;
1117                         sz = vq->size;
1118                         idx = desc_indexes[i];
1119                 }
1120
1121                 pkts[i] = rte_pktmbuf_alloc(mbuf_pool);
1122                 if (unlikely(pkts[i] == NULL)) {
1123                         RTE_LOG(ERR, VHOST_DATA,
1124                                 "Failed to allocate memory for mbuf.\n");
1125                         break;
1126                 }
1127
1128                 err = copy_desc_to_mbuf(dev, desc, sz, pkts[i], idx, mbuf_pool);
1129                 if (unlikely(err)) {
1130                         rte_pktmbuf_free(pkts[i]);
1131                         break;
1132                 }
1133
1134                 if (unlikely(dev->dequeue_zero_copy)) {
1135                         struct zcopy_mbuf *zmbuf;
1136
1137                         zmbuf = get_zmbuf(vq);
1138                         if (!zmbuf) {
1139                                 rte_pktmbuf_free(pkts[i]);
1140                                 break;
1141                         }
1142                         zmbuf->mbuf = pkts[i];
1143                         zmbuf->desc_idx = desc_indexes[i];
1144
1145                         /*
1146                          * Pin lock the mbuf; we will check later to see
1147                          * whether the mbuf is freed (when we are the last
1148                          * user) or not. If that's the case, we then could
1149                          * update the used ring safely.
1150                          */
1151                         rte_mbuf_refcnt_update(pkts[i], 1);
1152
1153                         vq->nr_zmbuf += 1;
1154                         TAILQ_INSERT_TAIL(&vq->zmbuf_list, zmbuf, next);
1155                 }
1156         }
1157         vq->last_avail_idx += i;
1158
1159         if (likely(dev->dequeue_zero_copy == 0)) {
1160                 vq->last_used_idx += i;
1161                 update_used_idx(dev, vq, i);
1162         }
1163
1164 out:
1165         if (unlikely(rarp_mbuf != NULL)) {
1166                 /*
1167                  * Inject it to the head of "pkts" array, so that switch's mac
1168                  * learning table will get updated first.
1169                  */
1170                 memmove(&pkts[1], pkts, i * sizeof(struct rte_mbuf *));
1171                 pkts[0] = rarp_mbuf;
1172                 i += 1;
1173         }
1174
1175         return i;
1176 }