vhost: Add multi-versioning support

It also refactors the vhost code which was in one big file vhost-user.c.
Receive side code is in vhost_user_input.c and
Transmit side code is in vhost_user_output.c

Change-Id: I1b539b5008685889723e228265786a2a3e9f3a78
Signed-off-by: Mohsin Kazmi <sykazmi@cisco.com>

1 files changed, 678 insertions, 0 deletions

diff --git a/src/vnet/devices/virtio/vhost_user_input.c b/src/vnet/devices/virtio/vhost_user_input.c
new file mode 100644
index 00000000000..3db44731b5e
--- /dev/null
+++ b/src/vnet/devices/virtio/vhost_user_input.c
@@ -0,0 +1,678 @@
+/*
+ *------------------------------------------------------------------
+ * vhost-user-input
+ *
+ * Copyright (c) 2014-2018 Cisco and/or its affiliates.
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at:
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *------------------------------------------------------------------
+ */
+
+#include <fcntl.h>		/* for open */
+#include <sys/ioctl.h>
+#include <sys/socket.h>
+#include <sys/un.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <sys/uio.h>		/* for iovec */
+#include <netinet/in.h>
+#include <sys/vfs.h>
+
+#include <linux/if_arp.h>
+#include <linux/if_tun.h>
+
+#include <vlib/vlib.h>
+#include <vlib/unix/unix.h>
+
+#include <vnet/ip/ip.h>
+
+#include <vnet/ethernet/ethernet.h>
+#include <vnet/devices/devices.h>
+#include <vnet/feature/feature.h>
+
+#include <vnet/devices/virtio/vhost_user.h>
+#include <vnet/devices/virtio/vhost_user_inline.h>
+
+/*
+ * When an RX queue is down but active, received packets
+ * must be discarded. This value controls up to how many
+ * packets will be discarded during each round.
+ */
+#define VHOST_USER_DOWN_DISCARD_COUNT 256
+
+/*
+ * When the number of available buffers gets under this threshold,
+ * RX node will start discarding packets.
+ */
+#define VHOST_USER_RX_BUFFER_STARVATION 32
+
+/*
+ * On the receive side, the host should free descriptors as soon
+ * as possible in order to avoid TX drop in the VM.
+ * This value controls the number of copy operations that are stacked
+ * before copy is done for all and descriptors are given back to
+ * the guest.
+ * The value 64 was obtained by testing (48 and 128 were not as good).
+ */
+#define VHOST_USER_RX_COPY_THRESHOLD 64
+
+vlib_node_registration_t vhost_user_input_node;
+
+#define foreach_vhost_user_input_func_error      \
+  _(NO_ERROR, "no error")  \
+  _(NO_BUFFER, "no available buffer")  \
+  _(MMAP_FAIL, "mmap failure")  \
+  _(INDIRECT_OVERFLOW, "indirect descriptor overflows table")  \
+  _(UNDERSIZED_FRAME, "undersized ethernet frame received (< 14 bytes)") \
+  _(FULL_RX_QUEUE, "full rx queue (possible driver tx drop)")
+
+typedef enum
+{
+#define _(f,s) VHOST_USER_INPUT_FUNC_ERROR_##f,
+  foreach_vhost_user_input_func_error
+#undef _
+    VHOST_USER_INPUT_FUNC_N_ERROR,
+} vhost_user_input_func_error_t;
+
+static __clib_unused char *vhost_user_input_func_error_strings[] = {
+#define _(n,s) s,
+  foreach_vhost_user_input_func_error
+#undef _
+};
+
+static_always_inline void
+vhost_user_rx_trace (vhost_trace_t * t,
+		     vhost_user_intf_t * vui, u16 qid,
+		     vlib_buffer_t * b, vhost_user_vring_t * txvq)
+{
+  vhost_user_main_t *vum = &vhost_user_main;
+  u32 last_avail_idx = txvq->last_avail_idx;
+  u32 desc_current = txvq->avail->ring[last_avail_idx & txvq->qsz_mask];
+  vring_desc_t *hdr_desc = 0;
+  virtio_net_hdr_mrg_rxbuf_t *hdr;
+  u32 hint = 0;
+
+  memset (t, 0, sizeof (*t));
+  t->device_index = vui - vum->vhost_user_interfaces;
+  t->qid = qid;
+
+  hdr_desc = &txvq->desc[desc_current];
+  if (txvq->desc[desc_current].flags & VIRTQ_DESC_F_INDIRECT)
+    {
+      t->virtio_ring_flags |= 1 << VIRTIO_TRACE_F_INDIRECT;
+      /* Header is the first here */
+      hdr_desc = map_guest_mem (vui, txvq->desc[desc_current].addr, &hint);
+    }
+  if (txvq->desc[desc_current].flags & VIRTQ_DESC_F_NEXT)
+    {
+      t->virtio_ring_flags |= 1 << VIRTIO_TRACE_F_SIMPLE_CHAINED;
+    }
+  if (!(txvq->desc[desc_current].flags & VIRTQ_DESC_F_NEXT) &&
+      !(txvq->desc[desc_current].flags & VIRTQ_DESC_F_INDIRECT))
+    {
+      t->virtio_ring_flags |= 1 << VIRTIO_TRACE_F_SINGLE_DESC;
+    }
+
+  t->first_desc_len = hdr_desc ? hdr_desc->len : 0;
+
+  if (!hdr_desc || !(hdr = map_guest_mem (vui, hdr_desc->addr, &hint)))
+    {
+      t->virtio_ring_flags |= 1 << VIRTIO_TRACE_F_MAP_ERROR;
+    }
+  else
+    {
+      u32 len = vui->virtio_net_hdr_sz;
+      memcpy (&t->hdr, hdr, len > hdr_desc->len ? hdr_desc->len : len);
+    }
+}
+
+static_always_inline u32
+vhost_user_input_copy (vhost_user_intf_t * vui, vhost_copy_t * cpy,
+		       u16 copy_len, u32 * map_hint)
+{
+  void *src0, *src1, *src2, *src3;
+  if (PREDICT_TRUE (copy_len >= 4))
+    {
+      if (PREDICT_FALSE (!(src2 = map_guest_mem (vui, cpy[0].src, map_hint))))
+	return 1;
+      if (PREDICT_FALSE (!(src3 = map_guest_mem (vui, cpy[1].src, map_hint))))
+	return 1;
+
+      while (PREDICT_TRUE (copy_len >= 4))
+	{
+	  src0 = src2;
+	  src1 = src3;
+
+	  if (PREDICT_FALSE
+	      (!(src2 = map_guest_mem (vui, cpy[2].src, map_hint))))
+	    return 1;
+	  if (PREDICT_FALSE
+	      (!(src3 = map_guest_mem (vui, cpy[3].src, map_hint))))
+	    return 1;
+
+	  CLIB_PREFETCH (src2, 64, LOAD);
+	  CLIB_PREFETCH (src3, 64, LOAD);
+
+	  clib_memcpy ((void *) cpy[0].dst, src0, cpy[0].len);
+	  clib_memcpy ((void *) cpy[1].dst, src1, cpy[1].len);
+	  copy_len -= 2;
+	  cpy += 2;
+	}
+    }
+  while (copy_len)
+    {
+      if (PREDICT_FALSE (!(src0 = map_guest_mem (vui, cpy->src, map_hint))))
+	return 1;
+      clib_memcpy ((void *) cpy->dst, src0, cpy->len);
+      copy_len -= 1;
+      cpy += 1;
+    }
+  return 0;
+}
+
+/**
+ * Try to discard packets from the tx ring (VPP RX path).
+ * Returns the number of discarded packets.
+ */
+static_always_inline u32
+vhost_user_rx_discard_packet (vlib_main_t * vm,
+			      vhost_user_intf_t * vui,
+			      vhost_user_vring_t * txvq, u32 discard_max)
+{
+  /*
+   * On the RX side, each packet corresponds to one descriptor
+   * (it is the same whether it is a shallow descriptor, chained, or indirect).
+   * Therefore, discarding a packet is like discarding a descriptor.
+   */
+  u32 discarded_packets = 0;
+  u32 avail_idx = txvq->avail->idx;
+  while (discarded_packets != discard_max)
+    {
+      if (avail_idx == txvq->last_avail_idx)
+	goto out;
+
+      u16 desc_chain_head =
+	txvq->avail->ring[txvq->last_avail_idx & txvq->qsz_mask];
+      txvq->last_avail_idx++;
+      txvq->used->ring[txvq->last_used_idx & txvq->qsz_mask].id =
+	desc_chain_head;
+      txvq->used->ring[txvq->last_used_idx & txvq->qsz_mask].len = 0;
+      vhost_user_log_dirty_ring (vui, txvq,
+				 ring[txvq->last_used_idx & txvq->qsz_mask]);
+      txvq->last_used_idx++;
+      discarded_packets++;
+    }
+
+out:
+  CLIB_MEMORY_BARRIER ();
+  txvq->used->idx = txvq->last_used_idx;
+  vhost_user_log_dirty_ring (vui, txvq, idx);
+  return discarded_packets;
+}
+
+/*
+ * In case of overflow, we need to rewind the array of allocated buffers.
+ */
+static __clib_unused void
+vhost_user_input_rewind_buffers (vlib_main_t * vm,
+				 vhost_cpu_t * cpu, vlib_buffer_t * b_head)
+{
+  u32 bi_current = cpu->rx_buffers[cpu->rx_buffers_len];
+  vlib_buffer_t *b_current = vlib_get_buffer (vm, bi_current);
+  b_current->current_length = 0;
+  b_current->flags = 0;
+  while (b_current != b_head)
+    {
+      cpu->rx_buffers_len++;
+      bi_current = cpu->rx_buffers[cpu->rx_buffers_len];
+      b_current = vlib_get_buffer (vm, bi_current);
+      b_current->current_length = 0;
+      b_current->flags = 0;
+    }
+  cpu->rx_buffers_len++;
+}
+
+static __clib_unused u32
+vhost_user_if_input (vlib_main_t * vm,
+		     vhost_user_main_t * vum,
+		     vhost_user_intf_t * vui,
+		     u16 qid, vlib_node_runtime_t * node,
+		     vnet_hw_interface_rx_mode mode)
+{
+  vhost_user_vring_t *txvq = &vui->vrings[VHOST_VRING_IDX_TX (qid)];
+  u16 n_rx_packets = 0;
+  u32 n_rx_bytes = 0;
+  u16 n_left;
+  u32 n_left_to_next, *to_next;
+  u32 next_index = VNET_DEVICE_INPUT_NEXT_ETHERNET_INPUT;
+  u32 n_trace = vlib_get_trace_count (vm, node);
+  u32 map_hint = 0;
+  u16 thread_index = vlib_get_thread_index ();
+  u16 copy_len = 0;
+
+  {
+    /* do we have pending interrupts ? */
+    vhost_user_vring_t *rxvq = &vui->vrings[VHOST_VRING_IDX_RX (qid)];
+    f64 now = vlib_time_now (vm);
+
+    if ((txvq->n_since_last_int) && (txvq->int_deadline < now))
+      vhost_user_send_call (vm, txvq);
+
+    if ((rxvq->n_since_last_int) && (rxvq->int_deadline < now))
+      vhost_user_send_call (vm, rxvq);
+  }
+
+  /*
+   * For adaptive mode, it is optimized to reduce interrupts.
+   * If the scheduler switches the input node to polling due
+   * to burst of traffic, we tell the driver no interrupt.
+   * When the traffic subsides, the scheduler switches the node back to
+   * interrupt mode. We must tell the driver we want interrupt.
+   */
+  if (PREDICT_FALSE (mode == VNET_HW_INTERFACE_RX_MODE_ADAPTIVE))
+    {
+      if ((node->flags &
+	   VLIB_NODE_FLAG_SWITCH_FROM_POLLING_TO_INTERRUPT_MODE) ||
+	  !(node->flags &
+	    VLIB_NODE_FLAG_SWITCH_FROM_INTERRUPT_TO_POLLING_MODE))
+	/* Tell driver we want notification */
+	txvq->used->flags = 0;
+      else
+	/* Tell driver we don't want notification */
+	txvq->used->flags = VRING_USED_F_NO_NOTIFY;
+    }
+
+  if (PREDICT_FALSE (txvq->avail->flags & 0xFFFE))
+    return 0;
+
+  n_left = (u16) (txvq->avail->idx - txvq->last_avail_idx);
+
+  /* nothing to do */
+  if (PREDICT_FALSE (n_left == 0))
+    return 0;
+
+  if (PREDICT_FALSE (!vui->admin_up || !(txvq->enabled)))
+    {
+      /*
+       * Discard input packet if interface is admin down or vring is not
+       * enabled.
+       * "For example, for a networking device, in the disabled state
+       * client must not supply any new RX packets, but must process
+       * and discard any TX packets."
+       */
+      vhost_user_rx_discard_packet (vm, vui, txvq,
+				    VHOST_USER_DOWN_DISCARD_COUNT);
+      return 0;
+    }
+
+  if (PREDICT_FALSE (n_left == (txvq->qsz_mask + 1)))
+    {
+      /*
+       * Informational error logging when VPP is not
+       * receiving packets fast enough.
+       */
+      vlib_error_count (vm, node->node_index,
+			VHOST_USER_INPUT_FUNC_ERROR_FULL_RX_QUEUE, 1);
+    }
+
+  if (n_left > VLIB_FRAME_SIZE)
+    n_left = VLIB_FRAME_SIZE;
+
+  /*
+   * For small packets (<2kB), we will not need more than one vlib buffer
+   * per packet. In case packets are bigger, we will just yeld at some point
+   * in the loop and come back later. This is not an issue as for big packet,
+   * processing cost really comes from the memory copy.
+   * The assumption is that big packets will fit in 40 buffers.
+   */
+  if (PREDICT_FALSE (vum->cpus[thread_index].rx_buffers_len < n_left + 1 ||
+		     vum->cpus[thread_index].rx_buffers_len < 40))
+    {
+      u32 curr_len = vum->cpus[thread_index].rx_buffers_len;
+      vum->cpus[thread_index].rx_buffers_len +=
+	vlib_buffer_alloc_from_free_list (vm,
+					  vum->cpus[thread_index].rx_buffers +
+					  curr_len,
+					  VHOST_USER_RX_BUFFERS_N - curr_len,
+					  VLIB_BUFFER_DEFAULT_FREE_LIST_INDEX);
+
+      if (PREDICT_FALSE
+	  (vum->cpus[thread_index].rx_buffers_len <
+	   VHOST_USER_RX_BUFFER_STARVATION))
+	{
+	  /* In case of buffer starvation, discard some packets from the queue
+	   * and log the event.
+	   * We keep doing best effort for the remaining packets. */
+	  u32 flush = (n_left + 1 > vum->cpus[thread_index].rx_buffers_len) ?
+	    n_left + 1 - vum->cpus[thread_index].rx_buffers_len : 1;
+	  flush = vhost_user_rx_discard_packet (vm, vui, txvq, flush);
+
+	  n_left -= flush;
+	  vlib_increment_simple_counter (vnet_main.
+					 interface_main.sw_if_counters +
+					 VNET_INTERFACE_COUNTER_DROP,
+					 vlib_get_thread_index (),
+					 vui->sw_if_index, flush);
+
+	  vlib_error_count (vm, vhost_user_input_node.index,
+			    VHOST_USER_INPUT_FUNC_ERROR_NO_BUFFER, flush);
+	}
+    }
+
+  while (n_left > 0)
+    {
+      vlib_get_next_frame (vm, node, next_index, to_next, n_left_to_next);
+
+      while (n_left > 0 && n_left_to_next > 0)
+	{
+	  vlib_buffer_t *b_head, *b_current;
+	  u32 bi_current;
+	  u16 desc_current;
+	  u32 desc_data_offset;
+	  vring_desc_t *desc_table = txvq->desc;
+
+	  if (PREDICT_FALSE (vum->cpus[thread_index].rx_buffers_len <= 1))
+	    {
+	      /* Not enough rx_buffers
+	       * Note: We yeld on 1 so we don't need to do an additional
+	       * check for the next buffer prefetch.
+	       */
+	      n_left = 0;
+	      break;
+	    }
+
+	  desc_current =
+	    txvq->avail->ring[txvq->last_avail_idx & txvq->qsz_mask];
+	  vum->cpus[thread_index].rx_buffers_len--;
+	  bi_current = (vum->cpus[thread_index].rx_buffers)
+	    [vum->cpus[thread_index].rx_buffers_len];
+	  b_head = b_current = vlib_get_buffer (vm, bi_current);
+	  to_next[0] = bi_current;	//We do that now so we can forget about bi_current
+	  to_next++;
+	  n_left_to_next--;
+
+	  vlib_prefetch_buffer_with_index (vm,
+					   (vum->
+					    cpus[thread_index].rx_buffers)
+					   [vum->cpus[thread_index].
+					    rx_buffers_len - 1], LOAD);
+
+	  /* Just preset the used descriptor id and length for later */
+	  txvq->used->ring[txvq->last_used_idx & txvq->qsz_mask].id =
+	    desc_current;
+	  txvq->used->ring[txvq->last_used_idx & txvq->qsz_mask].len = 0;
+	  vhost_user_log_dirty_ring (vui, txvq,
+				     ring[txvq->last_used_idx &
+					  txvq->qsz_mask]);
+
+	  /* The buffer should already be initialized */
+	  b_head->total_length_not_including_first_buffer = 0;
+	  b_head->flags |= VLIB_BUFFER_TOTAL_LENGTH_VALID;
+
+	  if (PREDICT_FALSE (n_trace))
+	    {
+	      //TODO: next_index is not exactly known at that point
+	      vlib_trace_buffer (vm, node, next_index, b_head,
+				 /* follow_chain */ 0);
+	      vhost_trace_t *t0 =
+		vlib_add_trace (vm, node, b_head, sizeof (t0[0]));
+	      vhost_user_rx_trace (t0, vui, qid, b_head, txvq);
+	      n_trace--;
+	      vlib_set_trace_count (vm, node, n_trace);
+	    }
+
+	  /* This depends on the setup but is very consistent
+	   * So I think the CPU branch predictor will make a pretty good job
+	   * at optimizing the decision. */
+	  if (txvq->desc[desc_current].flags & VIRTQ_DESC_F_INDIRECT)
+	    {
+	      desc_table = map_guest_mem (vui, txvq->desc[desc_current].addr,
+					  &map_hint);
+	      desc_current = 0;
+	      if (PREDICT_FALSE (desc_table == 0))
+		{
+		  vlib_error_count (vm, node->node_index,
+				    VHOST_USER_INPUT_FUNC_ERROR_MMAP_FAIL, 1);
+		  goto out;
+		}
+	    }
+
+	  if (PREDICT_TRUE (vui->is_any_layout) ||
+	      (!(desc_table[desc_current].flags & VIRTQ_DESC_F_NEXT)))
+	    {
+	      /* ANYLAYOUT or single buffer */
+	      desc_data_offset = vui->virtio_net_hdr_sz;
+	    }
+	  else
+	    {
+	      /* CSR case without ANYLAYOUT, skip 1st buffer */
+	      desc_data_offset = desc_table[desc_current].len;
+	    }
+
+	  while (1)
+	    {
+	      /* Get more input if necessary. Or end of packet. */
+	      if (desc_data_offset == desc_table[desc_current].len)
+		{
+		  if (PREDICT_FALSE (desc_table[desc_current].flags &
+				     VIRTQ_DESC_F_NEXT))
+		    {
+		      desc_current = desc_table[desc_current].next;
+		      desc_data_offset = 0;
+		    }
+		  else
+		    {
+		      goto out;
+		    }
+		}
+
+	      /* Get more output if necessary. Or end of packet. */
+	      if (PREDICT_FALSE
+		  (b_current->current_length == VLIB_BUFFER_DATA_SIZE))
+		{
+		  if (PREDICT_FALSE
+		      (vum->cpus[thread_index].rx_buffers_len == 0))
+		    {
+		      /* Cancel speculation */
+		      to_next--;
+		      n_left_to_next++;
+
+		      /*
+		       * Checking if there are some left buffers.
+		       * If not, just rewind the used buffers and stop.
+		       * Note: Scheduled copies are not cancelled. This is
+		       * not an issue as they would still be valid. Useless,
+		       * but valid.
+		       */
+		      vhost_user_input_rewind_buffers (vm,
+						       &vum->cpus
+						       [thread_index],
+						       b_head);
+		      n_left = 0;
+		      goto stop;
+		    }
+
+		  /* Get next output */
+		  vum->cpus[thread_index].rx_buffers_len--;
+		  u32 bi_next =
+		    (vum->cpus[thread_index].rx_buffers)[vum->cpus
+							 [thread_index].rx_buffers_len];
+		  b_current->next_buffer = bi_next;
+		  b_current->flags |= VLIB_BUFFER_NEXT_PRESENT;
+		  bi_current = bi_next;
+		  b_current = vlib_get_buffer (vm, bi_current);
+		}
+
+	      /* Prepare a copy order executed later for the data */
+	      vhost_copy_t *cpy = &vum->cpus[thread_index].copy[copy_len];
+	      copy_len++;
+	      u32 desc_data_l =
+		desc_table[desc_current].len - desc_data_offset;
+	      cpy->len = VLIB_BUFFER_DATA_SIZE - b_current->current_length;
+	      cpy->len = (cpy->len > desc_data_l) ? desc_data_l : cpy->len;
+	      cpy->dst = (uword) (vlib_buffer_get_current (b_current) +
+				  b_current->current_length);
+	      cpy->src = desc_table[desc_current].addr + desc_data_offset;
+
+	      desc_data_offset += cpy->len;
+
+	      b_current->current_length += cpy->len;
+	      b_head->total_length_not_including_first_buffer += cpy->len;
+	    }
+
+	out:
+	  CLIB_PREFETCH (&n_left, sizeof (n_left), LOAD);
+
+	  n_rx_bytes += b_head->total_length_not_including_first_buffer;
+	  n_rx_packets++;
+
+	  b_head->total_length_not_including_first_buffer -=
+	    b_head->current_length;
+
+	  /* consume the descriptor and return it as used */
+	  txvq->last_avail_idx++;
+	  txvq->last_used_idx++;
+
+	  VLIB_BUFFER_TRACE_TRAJECTORY_INIT (b_head);
+
+	  vnet_buffer (b_head)->sw_if_index[VLIB_RX] = vui->sw_if_index;
+	  vnet_buffer (b_head)->sw_if_index[VLIB_TX] = (u32) ~ 0;
+	  b_head->error = 0;
+
+	  {
+	    u32 next0 = VNET_DEVICE_INPUT_NEXT_ETHERNET_INPUT;
+
+	    /* redirect if feature path enabled */
+	    vnet_feature_start_device_input_x1 (vui->sw_if_index, &next0,
+						b_head);
+
+	    u32 bi = to_next[-1];	//Cannot use to_next[-1] in the macro
+	    vlib_validate_buffer_enqueue_x1 (vm, node, next_index,
+					     to_next, n_left_to_next,
+					     bi, next0);
+	  }
+
+	  n_left--;
+
+	  /*
+	   * Although separating memory copies from virtio ring parsing
+	   * is beneficial, we can offer to perform the copies from time
+	   * to time in order to free some space in the ring.
+	   */
+	  if (PREDICT_FALSE (copy_len >= VHOST_USER_RX_COPY_THRESHOLD))
+	    {
+	      if (PREDICT_FALSE
+		  (vhost_user_input_copy (vui, vum->cpus[thread_index].copy,
+					  copy_len, &map_hint)))
+		{
+		  vlib_error_count (vm, node->node_index,
+				    VHOST_USER_INPUT_FUNC_ERROR_MMAP_FAIL, 1);
+		}
+	      copy_len = 0;
+
+	      /* give buffers back to driver */
+	      CLIB_MEMORY_BARRIER ();
+	      txvq->used->idx = txvq->last_used_idx;
+	      vhost_user_log_dirty_ring (vui, txvq, idx);
+	    }
+	}
+    stop:
+      vlib_put_next_frame (vm, node, next_index, n_left_to_next);
+    }
+
+  /* Do the memory copies */
+  if (PREDICT_FALSE
+      (vhost_user_input_copy (vui, vum->cpus[thread_index].copy,
+			      copy_len, &map_hint)))
+    {
+      vlib_error_count (vm, node->node_index,
+			VHOST_USER_INPUT_FUNC_ERROR_MMAP_FAIL, 1);
+    }
+
+  /* give buffers back to driver */
+  CLIB_MEMORY_BARRIER ();
+  txvq->used->idx = txvq->last_used_idx;
+  vhost_user_log_dirty_ring (vui, txvq, idx);
+
+  /* interrupt (call) handling */
+  if ((txvq->callfd_idx != ~0) &&
+      !(txvq->avail->flags & VRING_AVAIL_F_NO_INTERRUPT))
+    {
+      txvq->n_since_last_int += n_rx_packets;
+
+      if (txvq->n_since_last_int > vum->coalesce_frames)
+	vhost_user_send_call (vm, txvq);
+    }
+
+  /* increase rx counters */
+  vlib_increment_combined_counter
+    (vnet_main.interface_main.combined_sw_if_counters
+     + VNET_INTERFACE_COUNTER_RX,
+     vlib_get_thread_index (), vui->sw_if_index, n_rx_packets, n_rx_bytes);
+
+  vnet_device_increment_rx_packets (thread_index, n_rx_packets);
+
+  return n_rx_packets;
+}
+
+VLIB_NODE_FN (vhost_user_input_node) (vlib_main_t * vm,
+				      vlib_node_runtime_t * node,
+				      vlib_frame_t * frame)
+{
+  vhost_user_main_t *vum = &vhost_user_main;
+  uword n_rx_packets = 0;
+  vhost_user_intf_t *vui;
+  vnet_device_input_runtime_t *rt =
+    (vnet_device_input_runtime_t *) node->runtime_data;
+  vnet_device_and_queue_t *dq;
+
+  vec_foreach (dq, rt->devices_and_queues)
+  {
+    if (clib_smp_swap (&dq->interrupt_pending, 0) ||
+	(node->state == VLIB_NODE_STATE_POLLING))
+      {
+	vui =
+	  pool_elt_at_index (vum->vhost_user_interfaces, dq->dev_instance);
+	n_rx_packets = vhost_user_if_input (vm, vum, vui, dq->queue_id, node,
+					    dq->mode);
+      }
+  }
+
+  return n_rx_packets;
+}
+
+#ifndef CLIB_MARCH_VARIANT
+/* *INDENT-OFF* */
+VLIB_REGISTER_NODE (vhost_user_input_node) = {
+  .type = VLIB_NODE_TYPE_INPUT,
+  .name = "vhost-user-input",
+  .sibling_of = "device-input",
+
+  /* Will be enabled if/when hardware is detected. */
+  .state = VLIB_NODE_STATE_DISABLED,
+
+  .format_buffer = format_ethernet_header_with_length,
+  .format_trace = format_vhost_trace,
+
+  .n_errors = VHOST_USER_INPUT_FUNC_N_ERROR,
+  .error_strings = vhost_user_input_func_error_strings,
+};
+/* *INDENT-ON* */
+#endif
+
+/*
+ * fd.io coding-style-patch-verification: ON
+ *
+ * Local Variables:
+ * eval: (c-set-style "gnu")
+ * End:
+ */