drivers/net/xen-netback/rx.c

   1 /*
   2  * Copyright (c) 2016 Citrix Systems Inc.
   3  * Copyright (c) 2002-2005, K A Fraser
   4  *
   5  * This program is free software; you can redistribute it and/or
   6  * modify it under the terms of the GNU General Public License version 2
   7  * as published by the Free Software Foundation; or, when distributed
   8  * separately from the Linux kernel or incorporated into other
   9  * software packages, subject to the following license:
  10  *
  11  * Permission is hereby granted, free of charge, to any person obtaining a copy
  12  * of this source file (the "Software"), to deal in the Software without
  13  * restriction, including without limitation the rights to use, copy, modify,
  14  * merge, publish, distribute, sublicense, and/or sell copies of the Software,
  15  * and to permit persons to whom the Software is furnished to do so, subject to
  16  * the following conditions:
  17  *
  18  * The above copyright notice and this permission notice shall be included in
  19  * all copies or substantial portions of the Software.
  20  *
  21  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  22  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  23  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  24  * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  25  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
  26  * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
  27  * IN THE SOFTWARE.
  28  */
  29 #include "common.h"
  30
  31 #include <linux/kthread.h>
  32
  33 #include <xen/xen.h>
  34 #include <xen/events.h>
  35
  36 /*
  37  * Update the needed ring page slots for the first SKB queued.
  38  * Note that any call sequence outside the RX thread calling this function
  39  * needs to wake up the RX thread via a call of xenvif_kick_thread()
  40  * afterwards in order to avoid a race with putting the thread to sleep.
  41  */
  42 static void xenvif_update_needed_slots(struct xenvif_queue *queue,
  43                                        const struct sk_buff *skb)
  44 {
  45         unsigned int needed = 0;
  46
  47         if (skb) {
  48                 needed = DIV_ROUND_UP(skb->len, XEN_PAGE_SIZE);
  49                 if (skb_is_gso(skb))
  50                         needed++;
  51                 if (skb->sw_hash)
  52                         needed++;
  53         }
  54
  55         WRITE_ONCE(queue->rx_slots_needed, needed);
  56 }
  57
  58 static bool xenvif_rx_ring_slots_available(struct xenvif_queue *queue)
  59 {
  60         RING_IDX prod, cons;
  61         unsigned int needed;
  62
  63         needed = READ_ONCE(queue->rx_slots_needed);
  64         if (!needed)
  65                 return false;
  66
  67         do {
  68                 prod = queue->rx.sring->req_prod;
  69                 cons = queue->rx.req_cons;
  70
  71                 if (prod - cons >= needed)
  72                         return true;
  73
  74                 queue->rx.sring->req_event = prod + 1;
  75
  76                 /* Make sure event is visible before we check prod
  77                  * again.
  78                  */
  79                 mb();
  80         } while (queue->rx.sring->req_prod != prod);
  81
  82         return false;
  83 }
  84
  85 bool xenvif_rx_queue_tail(struct xenvif_queue *queue, struct sk_buff *skb)
  86 {
  87         unsigned long flags;
  88         bool ret = true;
  89
  90         spin_lock_irqsave(&queue->rx_queue.lock, flags);
  91
  92         if (queue->rx_queue_len >= queue->rx_queue_max) {
  93                 struct net_device *dev = queue->vif->dev;
  94
  95                 netif_tx_stop_queue(netdev_get_tx_queue(dev, queue->id));
  96                 ret = false;
  97         } else {
  98                 if (skb_queue_empty(&queue->rx_queue))
  99                         xenvif_update_needed_slots(queue, skb);
 100
 101                 __skb_queue_tail(&queue->rx_queue, skb);
 102
 103                 queue->rx_queue_len += skb->len;
 104         }
 105
 106         spin_unlock_irqrestore(&queue->rx_queue.lock, flags);
 107
 108         return ret;
 109 }
 110
 111 static struct sk_buff *xenvif_rx_dequeue(struct xenvif_queue *queue)
 112 {
 113         struct sk_buff *skb;
 114
 115         spin_lock_irq(&queue->rx_queue.lock);
 116
 117         skb = __skb_dequeue(&queue->rx_queue);
 118         if (skb) {
 119                 xenvif_update_needed_slots(queue, skb_peek(&queue->rx_queue));
 120
 121                 queue->rx_queue_len -= skb->len;
 122                 if (queue->rx_queue_len < queue->rx_queue_max) {
 123                         struct netdev_queue *txq;
 124
 125                         txq = netdev_get_tx_queue(queue->vif->dev, queue->id);
 126                         netif_tx_wake_queue(txq);
 127                 }
 128         }
 129
 130         spin_unlock_irq(&queue->rx_queue.lock);
 131
 132         return skb;
 133 }
 134
 135 static void xenvif_rx_queue_purge(struct xenvif_queue *queue)
 136 {
 137         struct sk_buff *skb;
 138
 139         while ((skb = xenvif_rx_dequeue(queue)) != NULL)
 140                 kfree_skb(skb);
 141 }
 142
 143 static void xenvif_rx_queue_drop_expired(struct xenvif_queue *queue)
 144 {
 145         struct sk_buff *skb;
 146
 147         for (;;) {
 148                 skb = skb_peek(&queue->rx_queue);
 149                 if (!skb)
 150                         break;
 151                 if (time_before(jiffies, XENVIF_RX_CB(skb)->expires))
 152                         break;
 153                 xenvif_rx_dequeue(queue);
 154                 kfree_skb(skb);
 155                 queue->vif->dev->stats.rx_dropped++;
 156         }
 157 }
 158
 159 static void xenvif_rx_copy_flush(struct xenvif_queue *queue)
 160 {
 161         unsigned int i;
 162         int notify;
 163
 164         gnttab_batch_copy(queue->rx_copy.op, queue->rx_copy.num);
 165
 166         for (i = 0; i < queue->rx_copy.num; i++) {
 167                 struct gnttab_copy *op;
 168
 169                 op = &queue->rx_copy.op[i];
 170
 171                 /* If the copy failed, overwrite the status field in
 172                  * the corresponding response.
 173                  */
 174                 if (unlikely(op->status != GNTST_okay)) {
 175                         struct xen_netif_rx_response *rsp;
 176
 177                         rsp = RING_GET_RESPONSE(&queue->rx,
 178                                                 queue->rx_copy.idx[i]);
 179                         rsp->status = op->status;
 180                 }
 181         }
 182
 183         queue->rx_copy.num = 0;
 184
 185         /* Push responses for all completed packets. */
 186         RING_PUSH_RESPONSES_AND_CHECK_NOTIFY(&queue->rx, notify);
 187         if (notify)
 188                 notify_remote_via_irq(queue->rx_irq);
 189
 190         __skb_queue_purge(queue->rx_copy.completed);
 191 }
 192
 193 static void xenvif_rx_copy_add(struct xenvif_queue *queue,
 194                                struct xen_netif_rx_request *req,
 195                                unsigned int offset, void *data, size_t len)
 196 {
 197         struct gnttab_copy *op;
 198         struct page *page;
 199         struct xen_page_foreign *foreign;
 200
 201         if (queue->rx_copy.num == COPY_BATCH_SIZE)
 202                 xenvif_rx_copy_flush(queue);
 203
 204         op = &queue->rx_copy.op[queue->rx_copy.num];
 205
 206         page = virt_to_page(data);
 207
 208         op->flags = GNTCOPY_dest_gref;
 209
 210         foreign = xen_page_foreign(page);
 211         if (foreign) {
 212                 op->source.domid = foreign->domid;
 213                 op->source.u.ref = foreign->gref;
 214                 op->flags |= GNTCOPY_source_gref;
 215         } else {
 216                 op->source.u.gmfn = virt_to_gfn(data);
 217                 op->source.domid  = DOMID_SELF;
 218         }
 219
 220         op->source.offset = xen_offset_in_page(data);
 221         op->dest.u.ref    = req->gref;
 222         op->dest.domid    = queue->vif->domid;
 223         op->dest.offset   = offset;
 224         op->len           = len;
 225
 226         queue->rx_copy.idx[queue->rx_copy.num] = queue->rx.req_cons;
 227         queue->rx_copy.num++;
 228 }
 229
 230 static unsigned int xenvif_gso_type(struct sk_buff *skb)
 231 {
 232         if (skb_is_gso(skb)) {
 233                 if (skb_shinfo(skb)->gso_type & SKB_GSO_TCPV4)
 234                         return XEN_NETIF_GSO_TYPE_TCPV4;
 235                 else
 236                         return XEN_NETIF_GSO_TYPE_TCPV6;
 237         }
 238         return XEN_NETIF_GSO_TYPE_NONE;
 239 }
 240
 241 struct xenvif_pkt_state {
 242         struct sk_buff *skb;
 243         size_t remaining_len;
 244         struct sk_buff *frag_iter;
 245         int frag; /* frag == -1 => frag_iter->head */
 246         unsigned int frag_offset;
 247         struct xen_netif_extra_info extras[XEN_NETIF_EXTRA_TYPE_MAX - 1];
 248         unsigned int extra_count;
 249         unsigned int slot;
 250 };
 251
 252 static void xenvif_rx_next_skb(struct xenvif_queue *queue,
 253                                struct xenvif_pkt_state *pkt)
 254 {
 255         struct sk_buff *skb;
 256         unsigned int gso_type;
 257
 258         skb = xenvif_rx_dequeue(queue);
 259
 260         queue->stats.tx_bytes += skb->len;
 261         queue->stats.tx_packets++;
 262
 263         /* Reset packet state. */
 264         memset(pkt, 0, sizeof(struct xenvif_pkt_state));
 265
 266         pkt->skb = skb;
 267         pkt->frag_iter = skb;
 268         pkt->remaining_len = skb->len;
 269         pkt->frag = -1;
 270
 271         gso_type = xenvif_gso_type(skb);
 272         if ((1 << gso_type) & queue->vif->gso_mask) {
 273                 struct xen_netif_extra_info *extra;
 274
 275                 extra = &pkt->extras[XEN_NETIF_EXTRA_TYPE_GSO - 1];
 276
 277                 extra->u.gso.type = gso_type;
 278                 extra->u.gso.size = skb_shinfo(skb)->gso_size;
 279                 extra->u.gso.pad = 0;
 280                 extra->u.gso.features = 0;
 281                 extra->type = XEN_NETIF_EXTRA_TYPE_GSO;
 282                 extra->flags = 0;
 283
 284                 pkt->extra_count++;
 285         }
 286
 287         if (queue->vif->xdp_headroom) {
 288                 struct xen_netif_extra_info *extra;
 289
 290                 extra = &pkt->extras[XEN_NETIF_EXTRA_TYPE_XDP - 1];
 291
 292                 memset(extra, 0, sizeof(struct xen_netif_extra_info));
 293                 extra->u.xdp.headroom = queue->vif->xdp_headroom;
 294                 extra->type = XEN_NETIF_EXTRA_TYPE_XDP;
 295                 extra->flags = 0;
 296
 297                 pkt->extra_count++;
 298         }
 299
 300         if (skb->sw_hash) {
 301                 struct xen_netif_extra_info *extra;
 302
 303                 extra = &pkt->extras[XEN_NETIF_EXTRA_TYPE_HASH - 1];
 304
 305                 extra->u.hash.algorithm =
 306                         XEN_NETIF_CTRL_HASH_ALGORITHM_TOEPLITZ;
 307
 308                 if (skb->l4_hash)
 309                         extra->u.hash.type =
 310                                 skb->protocol == htons(ETH_P_IP) ?
 311                                 _XEN_NETIF_CTRL_HASH_TYPE_IPV4_TCP :
 312                                 _XEN_NETIF_CTRL_HASH_TYPE_IPV6_TCP;
 313                 else
 314                         extra->u.hash.type =
 315                                 skb->protocol == htons(ETH_P_IP) ?
 316                                 _XEN_NETIF_CTRL_HASH_TYPE_IPV4 :
 317                                 _XEN_NETIF_CTRL_HASH_TYPE_IPV6;
 318
 319                 *(uint32_t *)extra->u.hash.value = skb_get_hash_raw(skb);
 320
 321                 extra->type = XEN_NETIF_EXTRA_TYPE_HASH;
 322                 extra->flags = 0;
 323
 324                 pkt->extra_count++;
 325         }
 326 }
 327
 328 static void xenvif_rx_complete(struct xenvif_queue *queue,
 329                                struct xenvif_pkt_state *pkt)
 330 {
 331         /* All responses are ready to be pushed. */
 332         queue->rx.rsp_prod_pvt = queue->rx.req_cons;
 333
 334         __skb_queue_tail(queue->rx_copy.completed, pkt->skb);
 335 }
 336
 337 static void xenvif_rx_next_frag(struct xenvif_pkt_state *pkt)
 338 {
 339         struct sk_buff *frag_iter = pkt->frag_iter;
 340         unsigned int nr_frags = skb_shinfo(frag_iter)->nr_frags;
 341
 342         pkt->frag++;
 343         pkt->frag_offset = 0;
 344
 345         if (pkt->frag >= nr_frags) {
 346                 if (frag_iter == pkt->skb)
 347                         pkt->frag_iter = skb_shinfo(frag_iter)->frag_list;
 348                 else
 349                         pkt->frag_iter = frag_iter->next;
 350
 351                 pkt->frag = -1;
 352         }
 353 }
 354
 355 static void xenvif_rx_next_chunk(struct xenvif_queue *queue,
 356                                  struct xenvif_pkt_state *pkt,
 357                                  unsigned int offset, void **data,
 358                                  size_t *len)
 359 {
 360         struct sk_buff *frag_iter = pkt->frag_iter;
 361         void *frag_data;
 362         size_t frag_len, chunk_len;
 363
 364         BUG_ON(!frag_iter);
 365
 366         if (pkt->frag == -1) {
 367                 frag_data = frag_iter->data;
 368                 frag_len = skb_headlen(frag_iter);
 369         } else {
 370                 skb_frag_t *frag = &skb_shinfo(frag_iter)->frags[pkt->frag];
 371
 372                 frag_data = skb_frag_address(frag);
 373                 frag_len = skb_frag_size(frag);
 374         }
 375
 376         frag_data += pkt->frag_offset;
 377         frag_len -= pkt->frag_offset;
 378
 379         chunk_len = min_t(size_t, frag_len, XEN_PAGE_SIZE - offset);
 380         chunk_len = min_t(size_t, chunk_len, XEN_PAGE_SIZE -
 381                                              xen_offset_in_page(frag_data));
 382
 383         pkt->frag_offset += chunk_len;
 384
 385         /* Advance to next frag? */
 386         if (frag_len == chunk_len)
 387                 xenvif_rx_next_frag(pkt);
 388
 389         *data = frag_data;
 390         *len = chunk_len;
 391 }
 392
 393 static void xenvif_rx_data_slot(struct xenvif_queue *queue,
 394                                 struct xenvif_pkt_state *pkt,
 395                                 struct xen_netif_rx_request *req,
 396                                 struct xen_netif_rx_response *rsp)
 397 {
 398         unsigned int offset = queue->vif->xdp_headroom;
 399         unsigned int flags;
 400
 401         do {
 402                 size_t len;
 403                 void *data;
 404
 405                 xenvif_rx_next_chunk(queue, pkt, offset, &data, &len);
 406                 xenvif_rx_copy_add(queue, req, offset, data, len);
 407
 408                 offset += len;
 409                 pkt->remaining_len -= len;
 410
 411         } while (offset < XEN_PAGE_SIZE && pkt->remaining_len > 0);
 412
 413         if (pkt->remaining_len > 0)
 414                 flags = XEN_NETRXF_more_data;
 415         else
 416                 flags = 0;
 417
 418         if (pkt->slot == 0) {
 419                 struct sk_buff *skb = pkt->skb;
 420
 421                 if (skb->ip_summed == CHECKSUM_PARTIAL)
 422                         flags |= XEN_NETRXF_csum_blank |
 423                                  XEN_NETRXF_data_validated;
 424                 else if (skb->ip_summed == CHECKSUM_UNNECESSARY)
 425                         flags |= XEN_NETRXF_data_validated;
 426
 427                 if (pkt->extra_count != 0)
 428                         flags |= XEN_NETRXF_extra_info;
 429         }
 430
 431         rsp->offset = 0;
 432         rsp->flags = flags;
 433         rsp->id = req->id;
 434         rsp->status = (s16)offset;
 435 }
 436
 437 static void xenvif_rx_extra_slot(struct xenvif_queue *queue,
 438                                  struct xenvif_pkt_state *pkt,
 439                                  struct xen_netif_rx_request *req,
 440                                  struct xen_netif_rx_response *rsp)
 441 {
 442         struct xen_netif_extra_info *extra = (void *)rsp;
 443         unsigned int i;
 444
 445         pkt->extra_count--;
 446
 447         for (i = 0; i < ARRAY_SIZE(pkt->extras); i++) {
 448                 if (pkt->extras[i].type) {
 449                         *extra = pkt->extras[i];
 450
 451                         if (pkt->extra_count != 0)
 452                                 extra->flags |= XEN_NETIF_EXTRA_FLAG_MORE;
 453
 454                         pkt->extras[i].type = 0;
 455                         return;
 456                 }
 457         }
 458         BUG();
 459 }
 460
 461 static void xenvif_rx_skb(struct xenvif_queue *queue)
 462 {
 463         struct xenvif_pkt_state pkt;
 464
 465         xenvif_rx_next_skb(queue, &pkt);
 466
 467         queue->last_rx_time = jiffies;
 468
 469         do {
 470                 struct xen_netif_rx_request *req;
 471                 struct xen_netif_rx_response *rsp;
 472
 473                 req = RING_GET_REQUEST(&queue->rx, queue->rx.req_cons);
 474                 rsp = RING_GET_RESPONSE(&queue->rx, queue->rx.req_cons);
 475
 476                 /* Extras must go after the first data slot */
 477                 if (pkt.slot != 0 && pkt.extra_count != 0)
 478                         xenvif_rx_extra_slot(queue, &pkt, req, rsp);
 479                 else
 480                         xenvif_rx_data_slot(queue, &pkt, req, rsp);
 481
 482                 queue->rx.req_cons++;
 483                 pkt.slot++;
 484         } while (pkt.remaining_len > 0 || pkt.extra_count != 0);
 485
 486         xenvif_rx_complete(queue, &pkt);
 487 }
 488
 489 #define RX_BATCH_SIZE 64
 490
 491 static void xenvif_rx_action(struct xenvif_queue *queue)
 492 {
 493         struct sk_buff_head completed_skbs;
 494         unsigned int work_done = 0;
 495
 496         __skb_queue_head_init(&completed_skbs);
 497         queue->rx_copy.completed = &completed_skbs;
 498
 499         while (xenvif_rx_ring_slots_available(queue) &&
 500                !skb_queue_empty(&queue->rx_queue) &&
 501                work_done < RX_BATCH_SIZE) {
 502                 xenvif_rx_skb(queue);
 503                 work_done++;
 504         }
 505
 506         /* Flush any pending copies and complete all skbs. */
 507         xenvif_rx_copy_flush(queue);
 508 }
 509
 510 static RING_IDX xenvif_rx_queue_slots(const struct xenvif_queue *queue)
 511 {
 512         RING_IDX prod, cons;
 513
 514         prod = queue->rx.sring->req_prod;
 515         cons = queue->rx.req_cons;
 516
 517         return prod - cons;
 518 }
 519
 520 static bool xenvif_rx_queue_stalled(const struct xenvif_queue *queue)
 521 {
 522         unsigned int needed = READ_ONCE(queue->rx_slots_needed);
 523
 524         return !queue->stalled &&
 525                 xenvif_rx_queue_slots(queue) < needed &&
 526                 time_after(jiffies,
 527                            queue->last_rx_time + queue->vif->stall_timeout);
 528 }
 529
 530 static bool xenvif_rx_queue_ready(struct xenvif_queue *queue)
 531 {
 532         unsigned int needed = READ_ONCE(queue->rx_slots_needed);
 533
 534         return queue->stalled && xenvif_rx_queue_slots(queue) >= needed;
 535 }
 536
 537 bool xenvif_have_rx_work(struct xenvif_queue *queue, bool test_kthread)
 538 {
 539         return xenvif_rx_ring_slots_available(queue) ||
 540                 (queue->vif->stall_timeout &&
 541                  (xenvif_rx_queue_stalled(queue) ||
 542                   xenvif_rx_queue_ready(queue))) ||
 543                 (test_kthread && kthread_should_stop()) ||
 544                 queue->vif->disabled;
 545 }
 546
 547 static long xenvif_rx_queue_timeout(struct xenvif_queue *queue)
 548 {
 549         struct sk_buff *skb;
 550         long timeout;
 551
 552         skb = skb_peek(&queue->rx_queue);
 553         if (!skb)
 554                 return MAX_SCHEDULE_TIMEOUT;
 555
 556         timeout = XENVIF_RX_CB(skb)->expires - jiffies;
 557         return timeout < 0 ? 0 : timeout;
 558 }
 559
 560 /* Wait until the guest Rx thread has work.
 561  *
 562  * The timeout needs to be adjusted based on the current head of the
 563  * queue (and not just the head at the beginning).  In particular, if
 564  * the queue is initially empty an infinite timeout is used and this
 565  * needs to be reduced when a skb is queued.
 566  *
 567  * This cannot be done with wait_event_timeout() because it only
 568  * calculates the timeout once.
 569  */
 570 static void xenvif_wait_for_rx_work(struct xenvif_queue *queue)
 571 {
 572         DEFINE_WAIT(wait);
 573
 574         if (xenvif_have_rx_work(queue, true))
 575                 return;
 576
 577         for (;;) {
 578                 long ret;
 579
 580                 prepare_to_wait(&queue->wq, &wait, TASK_INTERRUPTIBLE);
 581                 if (xenvif_have_rx_work(queue, true))
 582                         break;
 583                 if (atomic_fetch_andnot(NETBK_RX_EOI | NETBK_COMMON_EOI,
 584                                         &queue->eoi_pending) &
 585                     (NETBK_RX_EOI | NETBK_COMMON_EOI))
 586                         xen_irq_lateeoi(queue->rx_irq, 0);
 587
 588                 ret = schedule_timeout(xenvif_rx_queue_timeout(queue));
 589                 if (!ret)
 590                         break;
 591         }
 592         finish_wait(&queue->wq, &wait);
 593 }
 594
 595 static void xenvif_queue_carrier_off(struct xenvif_queue *queue)
 596 {
 597         struct xenvif *vif = queue->vif;
 598
 599         queue->stalled = true;
 600
 601         /* At least one queue has stalled? Disable the carrier. */
 602         spin_lock(&vif->lock);
 603         if (vif->stalled_queues++ == 0) {
 604                 netdev_info(vif->dev, "Guest Rx stalled");
 605                 netif_carrier_off(vif->dev);
 606         }
 607         spin_unlock(&vif->lock);
 608 }
 609
 610 static void xenvif_queue_carrier_on(struct xenvif_queue *queue)
 611 {
 612         struct xenvif *vif = queue->vif;
 613
 614         queue->last_rx_time = jiffies; /* Reset Rx stall detection. */
 615         queue->stalled = false;
 616
 617         /* All queues are ready? Enable the carrier. */
 618         spin_lock(&vif->lock);
 619         if (--vif->stalled_queues == 0) {
 620                 netdev_info(vif->dev, "Guest Rx ready");
 621                 netif_carrier_on(vif->dev);
 622         }
 623         spin_unlock(&vif->lock);
 624 }
 625
 626 int xenvif_kthread_guest_rx(void *data)
 627 {
 628         struct xenvif_queue *queue = data;
 629         struct xenvif *vif = queue->vif;
 630
 631         if (!vif->stall_timeout)
 632                 xenvif_queue_carrier_on(queue);
 633
 634         for (;;) {
 635                 xenvif_wait_for_rx_work(queue);
 636
 637                 if (kthread_should_stop())
 638                         break;
 639
 640                 /* This frontend is found to be rogue, disable it in
 641                  * kthread context. Currently this is only set when
 642                  * netback finds out frontend sends malformed packet,
 643                  * but we cannot disable the interface in softirq
 644                  * context so we defer it here, if this thread is
 645                  * associated with queue 0.
 646                  */
 647                 if (unlikely(vif->disabled && queue->id == 0)) {
 648                         xenvif_carrier_off(vif);
 649                         break;
 650                 }
 651
 652                 if (!skb_queue_empty(&queue->rx_queue))
 653                         xenvif_rx_action(queue);
 654
 655                 /* If the guest hasn't provided any Rx slots for a
 656                  * while it's probably not responsive, drop the
 657                  * carrier so packets are dropped earlier.
 658                  */
 659                 if (vif->stall_timeout) {
 660                         if (xenvif_rx_queue_stalled(queue))
 661                                 xenvif_queue_carrier_off(queue);
 662                         else if (xenvif_rx_queue_ready(queue))
 663                                 xenvif_queue_carrier_on(queue);
 664                 }
 665
 666                 /* Queued packets may have foreign pages from other
 667                  * domains.  These cannot be queued indefinitely as
 668                  * this would starve guests of grant refs and transmit
 669                  * slots.
 670                  */
 671                 xenvif_rx_queue_drop_expired(queue);
 672
 673                 cond_resched();
 674         }
 675
 676         /* Bin any remaining skbs */
 677         xenvif_rx_queue_purge(queue);
 678
 679         return 0;
 680 }