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>

6 files changed, 1667 insertions, 1534 deletions

diff --git a/src/vnet/devices/virtio/vhost-user.c b/src/vnet/devices/virtio/vhost_user.c
index f6406d469b2..a8a7ae89065 100644
--- a/src/vnet/devices/virtio/vhost-user.c
+++ b/src/vnet/devices/virtio/vhost_user.c
@@ -2,7 +2,7 @@
  *------------------------------------------------------------------
  * vhost.c - vhost-user
  *
- * Copyright (c) 2014 Cisco and/or its affiliates.
+ * 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:
@@ -39,7 +39,8 @@
 #include <vnet/devices/devices.h>
 #include <vnet/feature/feature.h>
 
-#include <vnet/devices/virtio/vhost-user.h>
+#include <vnet/devices/virtio/vhost_user.h>
+#include <vnet/devices/virtio/vhost_user_inline.h>
 
 /**
  * @file
@@ -49,122 +50,10 @@
  */
 
 
-#define VHOST_DEBUG_VQ 0
-
-#define DBG_SOCK(args...)			\
-  {						\
-    vhost_user_main_t *_vum = &vhost_user_main; \
-    if (_vum->debug)				\
-      clib_warning(args);			\
-  };
-
-#if VHOST_DEBUG_VQ == 1
-#define DBG_VQ(args...) clib_warning(args);
-#else
-#define DBG_VQ(args...)
-#endif
-
-/*
- * 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
-/*
- * On the transmit side, we keep processing the buffers from vlib in the while
- * loop and prepare the copy order to be executed later. However, the static
- * array which we keep the copy order is limited to VHOST_USER_COPY_ARRAY_N
- * entries. In order to not corrupt memory, we have to do the copy when the
- * static array reaches the copy threshold. We subtract 40 in case the code
- * goes into the inner loop for a maximum of 64k frames which may require
- * more array entries.
- */
-#define VHOST_USER_TX_COPY_THRESHOLD (VHOST_USER_COPY_ARRAY_N - 40)
-
-#define UNIX_GET_FD(unixfd_idx) ({ \
-    typeof(unixfd_idx) __unixfd_idx = (unixfd_idx); \
-    (__unixfd_idx != ~0) ? \
-	pool_elt_at_index (file_main.file_pool, \
-			   __unixfd_idx)->file_descriptor : -1; })
-
-#define foreach_virtio_trace_flags \
-  _ (SIMPLE_CHAINED, 0, "Simple descriptor chaining") \
-  _ (SINGLE_DESC,  1, "Single descriptor packet") \
-  _ (INDIRECT, 2, "Indirect descriptor") \
-  _ (MAP_ERROR, 4, "Memory mapping error")
-
-typedef enum
-{
-#define _(n,i,s) VIRTIO_TRACE_F_##n,
-  foreach_virtio_trace_flags
-#undef _
-} virtio_trace_flag_t;
-
-vlib_node_registration_t vhost_user_input_node;
-
-#define foreach_vhost_user_tx_func_error      \
-  _(NONE, "no error")  \
-  _(NOT_READY, "vhost vring not ready")  \
-  _(DOWN, "vhost interface is down")  \
-  _(PKT_DROP_NOBUF, "tx packet drops (no available descriptors)")  \
-  _(PKT_DROP_NOMRG, "tx packet drops (cannot merge descriptors)")  \
-  _(MMAP_FAIL, "mmap failure") \
-  _(INDIRECT_OVERFLOW, "indirect descriptor table overflow")
-
-typedef enum
-{
-#define _(f,s) VHOST_USER_TX_FUNC_ERROR_##f,
-  foreach_vhost_user_tx_func_error
-#undef _
-    VHOST_USER_TX_FUNC_N_ERROR,
-} vhost_user_tx_func_error_t;
-
-static char *vhost_user_tx_func_error_strings[] = {
-#define _(n,s) s,
-  foreach_vhost_user_tx_func_error
-#undef _
-};
-
-#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 char *vhost_user_input_func_error_strings[] = {
-#define _(n,s) s,
-  foreach_vhost_user_input_func_error
-#undef _
-};
+vlib_node_registration_t vhost_user_send_interrupt_node;
 
 /* *INDENT-OFF* */
-static vhost_user_main_t vhost_user_main = {
+vhost_user_main_t vhost_user_main = {
   .mtu_bytes = 1518,
 };
 
@@ -173,195 +62,6 @@ VNET_HW_INTERFACE_CLASS (vhost_interface_class, static) = {
 };
 /* *INDENT-ON* */
 
-static u8 *
-format_vhost_user_interface_name (u8 * s, va_list * args)
-{
-  u32 i = va_arg (*args, u32);
-  u32 show_dev_instance = ~0;
-  vhost_user_main_t *vum = &vhost_user_main;
-
-  if (i < vec_len (vum->show_dev_instance_by_real_dev_instance))
-    show_dev_instance = vum->show_dev_instance_by_real_dev_instance[i];
-
-  if (show_dev_instance != ~0)
-    i = show_dev_instance;
-
-  s = format (s, "VirtualEthernet0/0/%d", i);
-  return s;
-}
-
-static int
-vhost_user_name_renumber (vnet_hw_interface_t * hi, u32 new_dev_instance)
-{
-  // FIXME: check if the new dev instance is already used
-  vhost_user_main_t *vum = &vhost_user_main;
-  vec_validate_init_empty (vum->show_dev_instance_by_real_dev_instance,
-			   hi->dev_instance, ~0);
-
-  vum->show_dev_instance_by_real_dev_instance[hi->dev_instance] =
-    new_dev_instance;
-
-  DBG_SOCK ("renumbered vhost-user interface dev_instance %d to %d",
-	    hi->dev_instance, new_dev_instance);
-
-  return 0;
-}
-
-static_always_inline void *
-map_guest_mem (vhost_user_intf_t * vui, uword addr, u32 * hint)
-{
-  int i = *hint;
-  if (PREDICT_TRUE ((vui->regions[i].guest_phys_addr <= addr) &&
-		    ((vui->regions[i].guest_phys_addr +
-		      vui->regions[i].memory_size) > addr)))
-    {
-      return (void *) (vui->region_mmap_addr[i] + addr -
-		       vui->regions[i].guest_phys_addr);
-    }
-#if __SSE4_2__
-  __m128i rl, rh, al, ah, r;
-  al = _mm_set1_epi64x (addr + 1);
-  ah = _mm_set1_epi64x (addr);
-
-  rl = _mm_loadu_si128 ((__m128i *) & vui->region_guest_addr_lo[0]);
-  rl = _mm_cmpgt_epi64 (al, rl);
-  rh = _mm_loadu_si128 ((__m128i *) & vui->region_guest_addr_hi[0]);
-  rh = _mm_cmpgt_epi64 (rh, ah);
-  r = _mm_and_si128 (rl, rh);
-
-  rl = _mm_loadu_si128 ((__m128i *) & vui->region_guest_addr_lo[2]);
-  rl = _mm_cmpgt_epi64 (al, rl);
-  rh = _mm_loadu_si128 ((__m128i *) & vui->region_guest_addr_hi[2]);
-  rh = _mm_cmpgt_epi64 (rh, ah);
-  r = _mm_blend_epi16 (r, _mm_and_si128 (rl, rh), 0x22);
-
-  rl = _mm_loadu_si128 ((__m128i *) & vui->region_guest_addr_lo[4]);
-  rl = _mm_cmpgt_epi64 (al, rl);
-  rh = _mm_loadu_si128 ((__m128i *) & vui->region_guest_addr_hi[4]);
-  rh = _mm_cmpgt_epi64 (rh, ah);
-  r = _mm_blend_epi16 (r, _mm_and_si128 (rl, rh), 0x44);
-
-  rl = _mm_loadu_si128 ((__m128i *) & vui->region_guest_addr_lo[6]);
-  rl = _mm_cmpgt_epi64 (al, rl);
-  rh = _mm_loadu_si128 ((__m128i *) & vui->region_guest_addr_hi[6]);
-  rh = _mm_cmpgt_epi64 (rh, ah);
-  r = _mm_blend_epi16 (r, _mm_and_si128 (rl, rh), 0x88);
-
-  r = _mm_shuffle_epi8 (r, _mm_set_epi64x (0, 0x0e060c040a020800));
-  i = count_trailing_zeros (_mm_movemask_epi8 (r) |
-			    (1 << VHOST_MEMORY_MAX_NREGIONS));
-
-  if (i < vui->nregions)
-    {
-      *hint = i;
-      return (void *) (vui->region_mmap_addr[i] + addr -
-		       vui->regions[i].guest_phys_addr);
-    }
-#elif __aarch64__ && __ARM_NEON
-  uint64x2_t al, ah, rl, rh, r;
-  uint32_t u32 = 0;
-
-  al = vdupq_n_u64 (addr + 1);
-  ah = vdupq_n_u64 (addr);
-
-  /*First Iteration */
-  rl = vld1q_u64 (&vui->region_guest_addr_lo[0]);
-  rl = vcgtq_u64 (al, rl);
-  rh = vld1q_u64 (&vui->region_guest_addr_hi[0]);
-  rh = vcgtq_u64 (rh, ah);
-  r = vandq_u64 (rl, rh);
-  u32 |= (vgetq_lane_u8 (vreinterpretq_u8_u64 (r), 0) & 0x1);
-  u32 |= ((vgetq_lane_u8 (vreinterpretq_u8_u64 (r), 8) & 0x1) << 1);
-
-  if (u32)
-    {
-      i = count_trailing_zeros (u32);
-      goto vhost_map_guest_mem_done;
-    }
-
-  /*Second Iteration */
-  rl = vld1q_u64 (&vui->region_guest_addr_lo[2]);
-  rl = vcgtq_u64 (al, rl);
-  rh = vld1q_u64 (&vui->region_guest_addr_hi[2]);
-  rh = vcgtq_u64 (rh, ah);
-  r = vandq_u64 (rl, rh);
-  u32 |= ((vgetq_lane_u8 (vreinterpretq_u8_u64 (r), 0) & 0x1) << 2);
-  u32 |= ((vgetq_lane_u8 (vreinterpretq_u8_u64 (r), 8) & 0x1) << 3);
-
-  if (u32)
-    {
-      i = count_trailing_zeros (u32);
-      goto vhost_map_guest_mem_done;
-    }
-
-  /*Third Iteration */
-  rl = vld1q_u64 (&vui->region_guest_addr_lo[4]);
-  rl = vcgtq_u64 (al, rl);
-  rh = vld1q_u64 (&vui->region_guest_addr_hi[4]);
-  rh = vcgtq_u64 (rh, ah);
-  r = vandq_u64 (rl, rh);
-  u32 |= ((vgetq_lane_u8 (vreinterpretq_u8_u64 (r), 0) & 0x1) << 4);
-  u32 |= ((vgetq_lane_u8 (vreinterpretq_u8_u64 (r), 8) & 0x1) << 5);
-
-  if (u32)
-    {
-      i = count_trailing_zeros (u32);
-      goto vhost_map_guest_mem_done;
-    }
-
-  /*Fourth Iteration */
-  rl = vld1q_u64 (&vui->region_guest_addr_lo[6]);
-  rl = vcgtq_u64 (al, rl);
-  rh = vld1q_u64 (&vui->region_guest_addr_hi[6]);
-  rh = vcgtq_u64 (rh, ah);
-  r = vandq_u64 (rl, rh);
-  u32 |= ((vgetq_lane_u8 (vreinterpretq_u8_u64 (r), 0) & 0x1) << 6);
-  u32 |= ((vgetq_lane_u8 (vreinterpretq_u8_u64 (r), 8) & 0x1) << 7);
-
-  i = count_trailing_zeros (u32 | (1 << VHOST_MEMORY_MAX_NREGIONS));
-
-vhost_map_guest_mem_done:
-  if (i < vui->nregions)
-    {
-      *hint = i;
-      return (void *) (vui->region_mmap_addr[i] + addr -
-		       vui->regions[i].guest_phys_addr);
-    }
-#else
-  for (i = 0; i < vui->nregions; i++)
-    {
-      if ((vui->regions[i].guest_phys_addr <= addr) &&
-	  ((vui->regions[i].guest_phys_addr + vui->regions[i].memory_size) >
-	   addr))
-	{
-	  *hint = i;
-	  return (void *) (vui->region_mmap_addr[i] + addr -
-			   vui->regions[i].guest_phys_addr);
-	}
-    }
-#endif
-  DBG_VQ ("failed to map guest mem addr %llx", addr);
-  *hint = 0;
-  return 0;
-}
-
-static inline void *
-map_user_mem (vhost_user_intf_t * vui, uword addr)
-{
-  int i;
-  for (i = 0; i < vui->nregions; i++)
-    {
-      if ((vui->regions[i].userspace_addr <= addr) &&
-	  ((vui->regions[i].userspace_addr + vui->regions[i].memory_size) >
-	   addr))
-	{
-	  return (void *) (vui->region_mmap_addr[i] + addr -
-			   vui->regions[i].userspace_addr);
-	}
-    }
-  return 0;
-}
-
 static long
 get_huge_page_size (int fd)
 {
@@ -510,7 +210,7 @@ vhost_user_rx_thread_placement ()
 }
 
 /** @brief Returns whether at least one TX and one RX vring are enabled */
-int
+static_always_inline int
 vhost_user_intf_ready (vhost_user_intf_t * vui)
 {
   int i, found[2] = { };	//RX + TX
@@ -592,36 +292,7 @@ vhost_user_kickfd_read_ready (clib_file_t * uf)
   return 0;
 }
 
-/**
- * @brief Try once to lock the vring
- * @return 0 on success, non-zero on failure.
- */
-static inline int
-vhost_user_vring_try_lock (vhost_user_intf_t * vui, u32 qid)
-{
-  return __sync_lock_test_and_set (vui->vring_locks[qid], 1);
-}
-
-/**
- * @brief Spin until the vring is successfully locked
- */
-static inline void
-vhost_user_vring_lock (vhost_user_intf_t * vui, u32 qid)
-{
-  while (vhost_user_vring_try_lock (vui, qid))
-    ;
-}
-
-/**
- * @brief Unlock the vring lock
- */
-static inline void
-vhost_user_vring_unlock (vhost_user_intf_t * vui, u32 qid)
-{
-  *vui->vring_locks[qid] = 0;
-}
-
-static inline void
+static_always_inline void
 vhost_user_vring_init (vhost_user_intf_t * vui, u32 qid)
 {
   vhost_user_vring_t *vring = &vui->vrings[qid];
@@ -643,7 +314,7 @@ vhost_user_vring_init (vhost_user_intf_t * vui, u32 qid)
     vring->enabled = 1;
 }
 
-static inline void
+static_always_inline void
 vhost_user_vring_close (vhost_user_intf_t * vui, u32 qid)
 {
   vhost_user_vring_t *vring = &vui->vrings[qid];
@@ -669,7 +340,7 @@ vhost_user_vring_close (vhost_user_intf_t * vui, u32 qid)
   vhost_user_vring_init (vui, qid);
 }
 
-static inline void
+static_always_inline void
 vhost_user_if_disconnect (vhost_user_intf_t * vui)
 {
   vnet_main_t *vnm = vnet_get_main ();
@@ -692,47 +363,6 @@ vhost_user_if_disconnect (vhost_user_intf_t * vui)
   DBG_SOCK ("interface ifindex %d disconnected", vui->sw_if_index);
 }
 
-#define VHOST_LOG_PAGE 0x1000
-static_always_inline void
-vhost_user_log_dirty_pages_2 (vhost_user_intf_t * vui,
-			      u64 addr, u64 len, u8 is_host_address)
-{
-  if (PREDICT_TRUE (vui->log_base_addr == 0
-		    || !(vui->features & (1 << FEAT_VHOST_F_LOG_ALL))))
-    {
-      return;
-    }
-  if (is_host_address)
-    {
-      addr = pointer_to_uword (map_user_mem (vui, (uword) addr));
-    }
-  if (PREDICT_FALSE ((addr + len - 1) / VHOST_LOG_PAGE / 8 >= vui->log_size))
-    {
-      DBG_SOCK ("vhost_user_log_dirty_pages(): out of range\n");
-      return;
-    }
-
-  CLIB_MEMORY_BARRIER ();
-  u64 page = addr / VHOST_LOG_PAGE;
-  while (page * VHOST_LOG_PAGE < addr + len)
-    {
-      ((u8 *) vui->log_base_addr)[page / 8] |= 1 << page % 8;
-      page++;
-    }
-}
-
-static_always_inline void
-vhost_user_log_dirty_pages (vhost_user_intf_t * vui, u64 addr, u64 len)
-{
-  vhost_user_log_dirty_pages_2 (vui, addr, len, 0);
-}
-
-#define vhost_user_log_dirty_ring(vui, vq, member) \
-  if (PREDICT_FALSE(vq->log_used)) { \
-    vhost_user_log_dirty_pages(vui, vq->log_guest_addr + STRUCT_OFFSET_OF(vring_used_t, member), \
-                             sizeof(vq->used->member)); \
-  }
-
 static clib_error_t *
 vhost_user_socket_read (clib_file_t * uf)
 {
@@ -1333,1056 +963,6 @@ vhost_user_init (vlib_main_t * vm)
 
 VLIB_INIT_FUNCTION (vhost_user_init);
 
-static u8 *
-format_vhost_trace (u8 * s, va_list * va)
-{
-  CLIB_UNUSED (vlib_main_t * vm) = va_arg (*va, vlib_main_t *);
-  CLIB_UNUSED (vlib_node_t * node) = va_arg (*va, vlib_node_t *);
-  CLIB_UNUSED (vnet_main_t * vnm) = vnet_get_main ();
-  vhost_user_main_t *vum = &vhost_user_main;
-  vhost_trace_t *t = va_arg (*va, vhost_trace_t *);
-  vhost_user_intf_t *vui = pool_elt_at_index (vum->vhost_user_interfaces,
-					      t->device_index);
-
-  vnet_sw_interface_t *sw = vnet_get_sw_interface (vnm, vui->sw_if_index);
-
-  u32 indent = format_get_indent (s);
-
-  s = format (s, "%U %U queue %d\n", format_white_space, indent,
-	      format_vnet_sw_interface_name, vnm, sw, t->qid);
-
-  s = format (s, "%U virtio flags:\n", format_white_space, indent);
-#define _(n,i,st) \
-	  if (t->virtio_ring_flags & (1 << VIRTIO_TRACE_F_##n)) \
-	    s = format (s, "%U  %s %s\n", format_white_space, indent, #n, st);
-  foreach_virtio_trace_flags
-#undef _
-    s = format (s, "%U virtio_net_hdr first_desc_len %u\n",
-		format_white_space, indent, t->first_desc_len);
-
-  s = format (s, "%U   flags 0x%02x gso_type %u\n",
-	      format_white_space, indent,
-	      t->hdr.hdr.flags, t->hdr.hdr.gso_type);
-
-  if (vui->virtio_net_hdr_sz == 12)
-    s = format (s, "%U   num_buff %u",
-		format_white_space, indent, t->hdr.num_buffers);
-
-  return s;
-}
-
-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 inline void
-vhost_user_send_call (vlib_main_t * vm, vhost_user_vring_t * vq)
-{
-  vhost_user_main_t *vum = &vhost_user_main;
-  u64 x = 1;
-  int fd = UNIX_GET_FD (vq->callfd_idx);
-  int rv;
-
-  rv = write (fd, &x, sizeof (x));
-  if (rv <= 0)
-    {
-      clib_unix_warning
-	("Error: Could not write to unix socket for callfd %d", fd);
-      return;
-    }
-
-  vq->n_since_last_int = 0;
-  vq->int_deadline = vlib_time_now (vm) + vum->coalesce_time;
-}
-
-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.
- */
-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 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 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;
-}
-
-static uword
-vhost_user_input (vlib_main_t * vm,
-		  vlib_node_runtime_t * node, vlib_frame_t * f)
-{
-  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;
-}
-
-/* *INDENT-OFF* */
-VLIB_REGISTER_NODE (vhost_user_input_node) = {
-  .function = vhost_user_input,
-  .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,
-};
-
-VLIB_NODE_FUNCTION_MULTIARCH (vhost_user_input_node, vhost_user_input)
-/* *INDENT-ON* */
-
-
-void
-vhost_user_tx_trace (vhost_trace_t * t,
-		     vhost_user_intf_t * vui, u16 qid,
-		     vlib_buffer_t * b, vhost_user_vring_t * rxvq)
-{
-  vhost_user_main_t *vum = &vhost_user_main;
-  u32 last_avail_idx = rxvq->last_avail_idx;
-  u32 desc_current = rxvq->avail->ring[last_avail_idx & rxvq->qsz_mask];
-  vring_desc_t *hdr_desc = 0;
-  u32 hint = 0;
-
-  memset (t, 0, sizeof (*t));
-  t->device_index = vui - vum->vhost_user_interfaces;
-  t->qid = qid;
-
-  hdr_desc = &rxvq->desc[desc_current];
-  if (rxvq->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, rxvq->desc[desc_current].addr, &hint);
-    }
-  if (rxvq->desc[desc_current].flags & VIRTQ_DESC_F_NEXT)
-    {
-      t->virtio_ring_flags |= 1 << VIRTIO_TRACE_F_SIMPLE_CHAINED;
-    }
-  if (!(rxvq->desc[desc_current].flags & VIRTQ_DESC_F_NEXT) &&
-      !(rxvq->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;
-}
-
-static_always_inline u32
-vhost_user_tx_copy (vhost_user_intf_t * vui, vhost_copy_t * cpy,
-		    u16 copy_len, u32 * map_hint)
-{
-  void *dst0, *dst1, *dst2, *dst3;
-  if (PREDICT_TRUE (copy_len >= 4))
-    {
-      if (PREDICT_FALSE (!(dst2 = map_guest_mem (vui, cpy[0].dst, map_hint))))
-	return 1;
-      if (PREDICT_FALSE (!(dst3 = map_guest_mem (vui, cpy[1].dst, map_hint))))
-	return 1;
-      while (PREDICT_TRUE (copy_len >= 4))
-	{
-	  dst0 = dst2;
-	  dst1 = dst3;
-
-	  if (PREDICT_FALSE
-	      (!(dst2 = map_guest_mem (vui, cpy[2].dst, map_hint))))
-	    return 1;
-	  if (PREDICT_FALSE
-	      (!(dst3 = map_guest_mem (vui, cpy[3].dst, map_hint))))
-	    return 1;
-
-	  CLIB_PREFETCH ((void *) cpy[2].src, 64, LOAD);
-	  CLIB_PREFETCH ((void *) cpy[3].src, 64, LOAD);
-
-	  clib_memcpy (dst0, (void *) cpy[0].src, cpy[0].len);
-	  clib_memcpy (dst1, (void *) cpy[1].src, cpy[1].len);
-
-	  vhost_user_log_dirty_pages_2 (vui, cpy[0].dst, cpy[0].len, 1);
-	  vhost_user_log_dirty_pages_2 (vui, cpy[1].dst, cpy[1].len, 1);
-	  copy_len -= 2;
-	  cpy += 2;
-	}
-    }
-  while (copy_len)
-    {
-      if (PREDICT_FALSE (!(dst0 = map_guest_mem (vui, cpy->dst, map_hint))))
-	return 1;
-      clib_memcpy (dst0, (void *) cpy->src, cpy->len);
-      vhost_user_log_dirty_pages_2 (vui, cpy->dst, cpy->len, 1);
-      copy_len -= 1;
-      cpy += 1;
-    }
-  return 0;
-}
-
-
-static uword
-vhost_user_tx (vlib_main_t * vm,
-	       vlib_node_runtime_t * node, vlib_frame_t * frame)
-{
-  u32 *buffers = vlib_frame_args (frame);
-  u32 n_left = frame->n_vectors;
-  vhost_user_main_t *vum = &vhost_user_main;
-  vnet_interface_output_runtime_t *rd = (void *) node->runtime_data;
-  vhost_user_intf_t *vui =
-    pool_elt_at_index (vum->vhost_user_interfaces, rd->dev_instance);
-  u32 qid = ~0;
-  vhost_user_vring_t *rxvq;
-  u8 error;
-  u32 thread_index = vlib_get_thread_index ();
-  u32 map_hint = 0;
-  u8 retry = 8;
-  u16 copy_len;
-  u16 tx_headers_len;
-
-  if (PREDICT_FALSE (!vui->admin_up))
-    {
-      error = VHOST_USER_TX_FUNC_ERROR_DOWN;
-      goto done3;
-    }
-
-  if (PREDICT_FALSE (!vui->is_up))
-    {
-      error = VHOST_USER_TX_FUNC_ERROR_NOT_READY;
-      goto done3;
-    }
-
-  qid =
-    VHOST_VRING_IDX_RX (*vec_elt_at_index
-			(vui->per_cpu_tx_qid, thread_index));
-  rxvq = &vui->vrings[qid];
-  if (PREDICT_FALSE (vui->use_tx_spinlock))
-    vhost_user_vring_lock (vui, qid);
-
-retry:
-  error = VHOST_USER_TX_FUNC_ERROR_NONE;
-  tx_headers_len = 0;
-  copy_len = 0;
-  while (n_left > 0)
-    {
-      vlib_buffer_t *b0, *current_b0;
-      u16 desc_head, desc_index, desc_len;
-      vring_desc_t *desc_table;
-      uword buffer_map_addr;
-      u32 buffer_len;
-      u16 bytes_left;
-
-      if (PREDICT_TRUE (n_left > 1))
-	vlib_prefetch_buffer_with_index (vm, buffers[1], LOAD);
-
-      b0 = vlib_get_buffer (vm, buffers[0]);
-
-      if (PREDICT_FALSE (b0->flags & VLIB_BUFFER_IS_TRACED))
-	{
-	  vum->cpus[thread_index].current_trace =
-	    vlib_add_trace (vm, node, b0,
-			    sizeof (*vum->cpus[thread_index].current_trace));
-	  vhost_user_tx_trace (vum->cpus[thread_index].current_trace,
-			       vui, qid / 2, b0, rxvq);
-	}
-
-      if (PREDICT_FALSE (rxvq->last_avail_idx == rxvq->avail->idx))
-	{
-	  error = VHOST_USER_TX_FUNC_ERROR_PKT_DROP_NOBUF;
-	  goto done;
-	}
-
-      desc_table = rxvq->desc;
-      desc_head = desc_index =
-	rxvq->avail->ring[rxvq->last_avail_idx & rxvq->qsz_mask];
-
-      /* Go deeper in case of indirect descriptor
-       * I don't know of any driver providing indirect for RX. */
-      if (PREDICT_FALSE (rxvq->desc[desc_head].flags & VIRTQ_DESC_F_INDIRECT))
-	{
-	  if (PREDICT_FALSE
-	      (rxvq->desc[desc_head].len < sizeof (vring_desc_t)))
-	    {
-	      error = VHOST_USER_TX_FUNC_ERROR_INDIRECT_OVERFLOW;
-	      goto done;
-	    }
-	  if (PREDICT_FALSE
-	      (!(desc_table =
-		 map_guest_mem (vui, rxvq->desc[desc_index].addr,
-				&map_hint))))
-	    {
-	      error = VHOST_USER_TX_FUNC_ERROR_MMAP_FAIL;
-	      goto done;
-	    }
-	  desc_index = 0;
-	}
-
-      desc_len = vui->virtio_net_hdr_sz;
-      buffer_map_addr = desc_table[desc_index].addr;
-      buffer_len = desc_table[desc_index].len;
-
-      {
-	// Get a header from the header array
-	virtio_net_hdr_mrg_rxbuf_t *hdr =
-	  &vum->cpus[thread_index].tx_headers[tx_headers_len];
-	tx_headers_len++;
-	hdr->hdr.flags = 0;
-	hdr->hdr.gso_type = 0;
-	hdr->num_buffers = 1;	//This is local, no need to check
-
-	// Prepare a copy order executed later for the header
-	vhost_copy_t *cpy = &vum->cpus[thread_index].copy[copy_len];
-	copy_len++;
-	cpy->len = vui->virtio_net_hdr_sz;
-	cpy->dst = buffer_map_addr;
-	cpy->src = (uword) hdr;
-      }
-
-      buffer_map_addr += vui->virtio_net_hdr_sz;
-      buffer_len -= vui->virtio_net_hdr_sz;
-      bytes_left = b0->current_length;
-      current_b0 = b0;
-      while (1)
-	{
-	  if (buffer_len == 0)
-	    {			//Get new output
-	      if (desc_table[desc_index].flags & VIRTQ_DESC_F_NEXT)
-		{
-		  //Next one is chained
-		  desc_index = desc_table[desc_index].next;
-		  buffer_map_addr = desc_table[desc_index].addr;
-		  buffer_len = desc_table[desc_index].len;
-		}
-	      else if (vui->virtio_net_hdr_sz == 12)	//MRG is available
-		{
-		  virtio_net_hdr_mrg_rxbuf_t *hdr =
-		    &vum->cpus[thread_index].tx_headers[tx_headers_len - 1];
-
-		  //Move from available to used buffer
-		  rxvq->used->ring[rxvq->last_used_idx & rxvq->qsz_mask].id =
-		    desc_head;
-		  rxvq->used->ring[rxvq->last_used_idx & rxvq->qsz_mask].len =
-		    desc_len;
-		  vhost_user_log_dirty_ring (vui, rxvq,
-					     ring[rxvq->last_used_idx &
-						  rxvq->qsz_mask]);
-
-		  rxvq->last_avail_idx++;
-		  rxvq->last_used_idx++;
-		  hdr->num_buffers++;
-		  desc_len = 0;
-
-		  if (PREDICT_FALSE
-		      (rxvq->last_avail_idx == rxvq->avail->idx))
-		    {
-		      //Dequeue queued descriptors for this packet
-		      rxvq->last_used_idx -= hdr->num_buffers - 1;
-		      rxvq->last_avail_idx -= hdr->num_buffers - 1;
-		      error = VHOST_USER_TX_FUNC_ERROR_PKT_DROP_NOBUF;
-		      goto done;
-		    }
-
-		  desc_table = rxvq->desc;
-		  desc_head = desc_index =
-		    rxvq->avail->ring[rxvq->last_avail_idx & rxvq->qsz_mask];
-		  if (PREDICT_FALSE
-		      (rxvq->desc[desc_head].flags & VIRTQ_DESC_F_INDIRECT))
-		    {
-		      //It is seriously unlikely that a driver will put indirect descriptor
-		      //after non-indirect descriptor.
-		      if (PREDICT_FALSE
-			  (rxvq->desc[desc_head].len < sizeof (vring_desc_t)))
-			{
-			  error = VHOST_USER_TX_FUNC_ERROR_INDIRECT_OVERFLOW;
-			  goto done;
-			}
-		      if (PREDICT_FALSE
-			  (!(desc_table =
-			     map_guest_mem (vui,
-					    rxvq->desc[desc_index].addr,
-					    &map_hint))))
-			{
-			  error = VHOST_USER_TX_FUNC_ERROR_MMAP_FAIL;
-			  goto done;
-			}
-		      desc_index = 0;
-		    }
-		  buffer_map_addr = desc_table[desc_index].addr;
-		  buffer_len = desc_table[desc_index].len;
-		}
-	      else
-		{
-		  error = VHOST_USER_TX_FUNC_ERROR_PKT_DROP_NOMRG;
-		  goto done;
-		}
-	    }
-
-	  {
-	    vhost_copy_t *cpy = &vum->cpus[thread_index].copy[copy_len];
-	    copy_len++;
-	    cpy->len = bytes_left;
-	    cpy->len = (cpy->len > buffer_len) ? buffer_len : cpy->len;
-	    cpy->dst = buffer_map_addr;
-	    cpy->src = (uword) vlib_buffer_get_current (current_b0) +
-	      current_b0->current_length - bytes_left;
-
-	    bytes_left -= cpy->len;
-	    buffer_len -= cpy->len;
-	    buffer_map_addr += cpy->len;
-	    desc_len += cpy->len;
-
-	    CLIB_PREFETCH (&rxvq->desc, CLIB_CACHE_LINE_BYTES, LOAD);
-	  }
-
-	  // Check if vlib buffer has more data. If not, get more or break.
-	  if (PREDICT_TRUE (!bytes_left))
-	    {
-	      if (PREDICT_FALSE
-		  (current_b0->flags & VLIB_BUFFER_NEXT_PRESENT))
-		{
-		  current_b0 = vlib_get_buffer (vm, current_b0->next_buffer);
-		  bytes_left = current_b0->current_length;
-		}
-	      else
-		{
-		  //End of packet
-		  break;
-		}
-	    }
-	}
-
-      //Move from available to used ring
-      rxvq->used->ring[rxvq->last_used_idx & rxvq->qsz_mask].id = desc_head;
-      rxvq->used->ring[rxvq->last_used_idx & rxvq->qsz_mask].len = desc_len;
-      vhost_user_log_dirty_ring (vui, rxvq,
-				 ring[rxvq->last_used_idx & rxvq->qsz_mask]);
-      rxvq->last_avail_idx++;
-      rxvq->last_used_idx++;
-
-      if (PREDICT_FALSE (b0->flags & VLIB_BUFFER_IS_TRACED))
-	{
-	  vum->cpus[thread_index].current_trace->hdr =
-	    vum->cpus[thread_index].tx_headers[tx_headers_len - 1];
-	}
-
-      n_left--;			//At the end for error counting when 'goto done' is invoked
-
-      /*
-       * Do the copy periodically to prevent
-       * vum->cpus[thread_index].copy array overflow and corrupt memory
-       */
-      if (PREDICT_FALSE (copy_len >= VHOST_USER_TX_COPY_THRESHOLD))
-	{
-	  if (PREDICT_FALSE
-	      (vhost_user_tx_copy (vui, vum->cpus[thread_index].copy,
-				   copy_len, &map_hint)))
-	    {
-	      vlib_error_count (vm, node->node_index,
-				VHOST_USER_TX_FUNC_ERROR_MMAP_FAIL, 1);
-	    }
-	  copy_len = 0;
-
-	  /* give buffers back to driver */
-	  CLIB_MEMORY_BARRIER ();
-	  rxvq->used->idx = rxvq->last_used_idx;
-	  vhost_user_log_dirty_ring (vui, rxvq, idx);
-	}
-      buffers++;
-    }
-
-done:
-  //Do the memory copies
-  if (PREDICT_FALSE
-      (vhost_user_tx_copy (vui, vum->cpus[thread_index].copy,
-			   copy_len, &map_hint)))
-    {
-      vlib_error_count (vm, node->node_index,
-			VHOST_USER_TX_FUNC_ERROR_MMAP_FAIL, 1);
-    }
-
-  CLIB_MEMORY_BARRIER ();
-  rxvq->used->idx = rxvq->last_used_idx;
-  vhost_user_log_dirty_ring (vui, rxvq, idx);
-
-  /*
-   * When n_left is set, error is always set to something too.
-   * In case error is due to lack of remaining buffers, we go back up and
-   * retry.
-   * The idea is that it is better to waste some time on packets
-   * that have been processed already than dropping them and get
-   * more fresh packets with a good likelyhood that they will be dropped too.
-   * This technique also gives more time to VM driver to pick-up packets.
-   * In case the traffic flows from physical to virtual interfaces, this
-   * technique will end-up leveraging the physical NIC buffer in order to
-   * absorb the VM's CPU jitter.
-   */
-  if (n_left && (error == VHOST_USER_TX_FUNC_ERROR_PKT_DROP_NOBUF) && retry)
-    {
-      retry--;
-      goto retry;
-    }
-
-  /* interrupt (call) handling */
-  if ((rxvq->callfd_idx != ~0) &&
-      !(rxvq->avail->flags & VRING_AVAIL_F_NO_INTERRUPT))
-    {
-      rxvq->n_since_last_int += frame->n_vectors - n_left;
-
-      if (rxvq->n_since_last_int > vum->coalesce_frames)
-	vhost_user_send_call (vm, rxvq);
-    }
-
-  vhost_user_vring_unlock (vui, qid);
-
-done3:
-  if (PREDICT_FALSE (n_left && error != VHOST_USER_TX_FUNC_ERROR_NONE))
-    {
-      vlib_error_count (vm, node->node_index, error, n_left);
-      vlib_increment_simple_counter
-	(vnet_main.interface_main.sw_if_counters
-	 + VNET_INTERFACE_COUNTER_DROP,
-	 thread_index, vui->sw_if_index, n_left);
-    }
-
-  vlib_buffer_free (vm, vlib_frame_args (frame), frame->n_vectors);
-  return frame->n_vectors;
-}
-
 static uword
 vhost_user_send_interrupt_process (vlib_main_t * vm,
 				   vlib_node_runtime_t * rt, vlib_frame_t * f)
@@ -2473,110 +1053,13 @@ vhost_user_send_interrupt_process (vlib_main_t * vm,
 }
 
 /* *INDENT-OFF* */
-VLIB_REGISTER_NODE (vhost_user_send_interrupt_node,static) = {
+VLIB_REGISTER_NODE (vhost_user_send_interrupt_node) = {
     .function = vhost_user_send_interrupt_process,
     .type = VLIB_NODE_TYPE_PROCESS,
     .name = "vhost-user-send-interrupt-process",
 };
 /* *INDENT-ON* */
 
-static clib_error_t *
-vhost_user_interface_rx_mode_change (vnet_main_t * vnm, u32 hw_if_index,
-				     u32 qid, vnet_hw_interface_rx_mode mode)
-{
-  vlib_main_t *vm = vnm->vlib_main;
-  vnet_hw_interface_t *hif = vnet_get_hw_interface (vnm, hw_if_index);
-  vhost_user_main_t *vum = &vhost_user_main;
-  vhost_user_intf_t *vui =
-    pool_elt_at_index (vum->vhost_user_interfaces, hif->dev_instance);
-  vhost_user_vring_t *txvq = &vui->vrings[VHOST_VRING_IDX_TX (qid)];
-
-  if ((mode == VNET_HW_INTERFACE_RX_MODE_INTERRUPT) ||
-      (mode == VNET_HW_INTERFACE_RX_MODE_ADAPTIVE))
-    {
-      if (txvq->kickfd_idx == ~0)
-	{
-	  // We cannot support interrupt mode if the driver opts out
-	  return clib_error_return (0, "Driver does not support interrupt");
-	}
-      if (txvq->mode == VNET_HW_INTERFACE_RX_MODE_POLLING)
-	{
-	  vum->ifq_count++;
-	  // Start the timer if this is the first encounter on interrupt
-	  // interface/queue
-	  if ((vum->ifq_count == 1) &&
-	      (vum->coalesce_time > 0.0) && (vum->coalesce_frames > 0))
-	    vlib_process_signal_event (vm,
-				       vhost_user_send_interrupt_node.index,
-				       VHOST_USER_EVENT_START_TIMER, 0);
-	}
-    }
-  else if (mode == VNET_HW_INTERFACE_RX_MODE_POLLING)
-    {
-      if (((txvq->mode == VNET_HW_INTERFACE_RX_MODE_INTERRUPT) ||
-	   (txvq->mode == VNET_HW_INTERFACE_RX_MODE_ADAPTIVE)) &&
-	  vum->ifq_count)
-	{
-	  vum->ifq_count--;
-	  // Stop the timer if there is no more interrupt interface/queue
-	  if ((vum->ifq_count == 0) &&
-	      (vum->coalesce_time > 0.0) && (vum->coalesce_frames > 0))
-	    vlib_process_signal_event (vm,
-				       vhost_user_send_interrupt_node.index,
-				       VHOST_USER_EVENT_STOP_TIMER, 0);
-	}
-    }
-
-  txvq->mode = mode;
-  if (mode == VNET_HW_INTERFACE_RX_MODE_POLLING)
-    txvq->used->flags = VRING_USED_F_NO_NOTIFY;
-  else if ((mode == VNET_HW_INTERFACE_RX_MODE_ADAPTIVE) ||
-	   (mode == VNET_HW_INTERFACE_RX_MODE_INTERRUPT))
-    txvq->used->flags = 0;
-  else
-    {
-      clib_warning ("BUG: unhandled mode %d changed for if %d queue %d", mode,
-		    hw_if_index, qid);
-      return clib_error_return (0, "unsupported");
-    }
-
-  return 0;
-}
-
-static clib_error_t *
-vhost_user_interface_admin_up_down (vnet_main_t * vnm, u32 hw_if_index,
-				    u32 flags)
-{
-  vnet_hw_interface_t *hif = vnet_get_hw_interface (vnm, hw_if_index);
-  vhost_user_main_t *vum = &vhost_user_main;
-  vhost_user_intf_t *vui =
-    pool_elt_at_index (vum->vhost_user_interfaces, hif->dev_instance);
-  u32 hw_flags = 0;
-  vui->admin_up = (flags & VNET_SW_INTERFACE_FLAG_ADMIN_UP) != 0;
-  hw_flags = vui->admin_up ? VNET_HW_INTERFACE_FLAG_LINK_UP : 0;
-
-  vnet_hw_interface_set_flags (vnm, vui->hw_if_index, hw_flags);
-
-  return /* no error */ 0;
-}
-
-/* *INDENT-OFF* */
-VNET_DEVICE_CLASS (vhost_user_dev_class,static) = {
-  .name = "vhost-user",
-  .tx_function = vhost_user_tx,
-  .tx_function_n_errors = VHOST_USER_TX_FUNC_N_ERROR,
-  .tx_function_error_strings = vhost_user_tx_func_error_strings,
-  .format_device_name = format_vhost_user_interface_name,
-  .name_renumber = vhost_user_name_renumber,
-  .admin_up_down_function = vhost_user_interface_admin_up_down,
-  .rx_mode_change_function = vhost_user_interface_rx_mode_change,
-  .format_tx_trace = format_vhost_trace,
-};
-
-VLIB_DEVICE_TX_FUNCTION_MULTIARCH (vhost_user_dev_class,
-				   vhost_user_tx)
-/* *INDENT-ON* */
-
 static uword
 vhost_user_process (vlib_main_t * vm,
 		    vlib_node_runtime_t * rt, vlib_frame_t * f)
@@ -2727,7 +1210,7 @@ vhost_user_delete_if (vnet_main_t * vnm, vlib_main_t * vm, u32 sw_if_index)
   u16 *queue;
 
   if (!(hwif = vnet_get_sup_hw_interface (vnm, sw_if_index)) ||
-      hwif->dev_class_index != vhost_user_dev_class.index)
+      hwif->dev_class_index != vhost_user_device_class.index)
     return VNET_API_ERROR_INVALID_SW_IF_INDEX;
 
   DBG_SOCK ("Deleting vhost-user interface %s (instance %d)",
@@ -2859,7 +1342,7 @@ vhost_user_create_ethernet (vnet_main_t * vnm, vlib_main_t * vm,
 
   error = ethernet_register_interface
     (vnm,
-     vhost_user_dev_class.index,
+     vhost_user_device_class.index,
      vui - vum->vhost_user_interfaces /* device instance */ ,
      hwaddr /* ethernet address */ ,
      &vui->hw_if_index, 0 /* flag change */ );
@@ -3007,7 +1490,7 @@ vhost_user_modify_if (vnet_main_t * vnm, vlib_main_t * vm,
   uword *if_index;
 
   if (!(hwif = vnet_get_sup_hw_interface (vnm, sw_if_index)) ||
-      hwif->dev_class_index != vhost_user_dev_class.index)
+      hwif->dev_class_index != vhost_user_device_class.index)
     return VNET_API_ERROR_INVALID_SW_IF_INDEX;
 
   if (sock_filename == NULL || !(strlen (sock_filename) > 0))
@@ -3132,7 +1615,7 @@ vhost_user_delete_command_fn (vlib_main_t * vm,
 	  vnet_hw_interface_t *hwif =
 	    vnet_get_sup_hw_interface (vnm, sw_if_index);
 	  if (hwif == NULL ||
-	      vhost_user_dev_class.index != hwif->dev_class_index)
+	      vhost_user_device_class.index != hwif->dev_class_index)
 	    {
 	      error = clib_error_return (0, "Not a vhost interface");
 	      goto done;
@@ -3251,7 +1734,7 @@ show_vhost_user_command_fn (vlib_main_t * vm,
 	  (input, "%U", unformat_vnet_hw_interface, vnm, &hw_if_index))
 	{
 	  hi = vnet_get_hw_interface (vnm, hw_if_index);
-	  if (vhost_user_dev_class.index != hi->dev_class_index)
+	  if (vhost_user_device_class.index != hi->dev_class_index)
 	    {
 	      error = clib_error_return (0, "unknown input `%U'",
 					 format_unformat_error, input);
@@ -3732,6 +2215,7 @@ vhost_user_config (vlib_main_t * vm, unformat_input_t * input)
   return 0;
 }
 
+
 /* vhost-user { ... } configuration. */
 VLIB_CONFIG_FUNCTION (vhost_user_config, "vhost-user");
 
diff --git a/src/vnet/devices/virtio/vhost-user.h b/src/vnet/devices/virtio/vhost_user.h
index 105b92b72ef..ff0669598c9 100644
--- a/src/vnet/devices/virtio/vhost-user.h
+++ b/src/vnet/devices/virtio/vhost_user.h
@@ -45,6 +45,40 @@
 #define VRING_USED_F_NO_NOTIFY  1
 #define VRING_AVAIL_F_NO_INTERRUPT 1
 
+#define DBG_SOCK(args...)                       \
+  {                                             \
+    vhost_user_main_t *_vum = &vhost_user_main; \
+    if (_vum->debug)                            \
+      clib_warning(args);                       \
+  };
+
+#define VHOST_DEBUG_VQ 0
+
+#if VHOST_DEBUG_VQ == 1
+#define DBG_VQ(args...) clib_warning(args);
+#else
+#define DBG_VQ(args...)
+#endif
+
+#define UNIX_GET_FD(unixfd_idx) ({ \
+    typeof(unixfd_idx) __unixfd_idx = (unixfd_idx); \
+    (__unixfd_idx != ~0) ? \
+        pool_elt_at_index (file_main.file_pool, \
+                           __unixfd_idx)->file_descriptor : -1; })
+
+#define foreach_virtio_trace_flags \
+  _ (SIMPLE_CHAINED, 0, "Simple descriptor chaining") \
+  _ (SINGLE_DESC,  1, "Single descriptor packet") \
+  _ (INDIRECT, 2, "Indirect descriptor") \
+  _ (MAP_ERROR, 4, "Memory mapping error")
+
+typedef enum
+{
+#define _(n,i,s) VIRTIO_TRACE_F_##n,
+  foreach_virtio_trace_flags
+#undef _
+} virtio_trace_flag_t;
+
 #define foreach_virtio_net_feature      \
  _ (VIRTIO_NET_F_MRG_RXBUF, 15)         \
  _ (VIRTIO_NET_F_CTRL_VQ, 17)           \
@@ -56,7 +90,6 @@
  _ (VHOST_USER_F_PROTOCOL_FEATURES, 30) \
  _ (VIRTIO_F_VERSION_1, 32)
 
-
 typedef enum
 {
 #define _(f,n) FEAT_##f = (n),
@@ -331,6 +364,11 @@ typedef struct
 int vhost_user_dump_ifs (vnet_main_t * vnm, vlib_main_t * vm,
 			 vhost_user_intf_details_t ** out_vuids);
 
+extern vlib_node_registration_t vhost_user_send_interrupt_node;
+extern vnet_device_class_t vhost_user_device_class;
+extern vlib_node_registration_t vhost_user_input_node;
+extern vhost_user_main_t vhost_user_main;
+
 #endif
 
 /*
diff --git a/src/vnet/devices/virtio/vhost_user_api.c b/src/vnet/devices/virtio/vhost_user_api.c
index 442d9146945..59dba252f22 100644
--- a/src/vnet/devices/virtio/vhost_user_api.c
+++ b/src/vnet/devices/virtio/vhost_user_api.c
@@ -22,7 +22,7 @@
 
 #include <vnet/interface.h>
 #include <vnet/api_errno.h>
-#include <vnet/devices/virtio/vhost-user.h>
+#include <vnet/devices/virtio/vhost_user.h>
 
 #include <vnet/vnet_msg_enum.h>
 
diff --git a/src/vnet/devices/virtio/vhost_user_inline.h b/src/vnet/devices/virtio/vhost_user_inline.h
new file mode 100644
index 00000000000..9f6135165ae
--- /dev/null
+++ b/src/vnet/devices/virtio/vhost_user_inline.h
@@ -0,0 +1,262 @@
+/*
+ * Copyright (c) 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.
+ */
+#ifndef __VIRTIO_VHOST_USER_INLINE_H__
+#define __VIRTIO_VHOST_USER_INLINE_H__
+/* vhost-user inline functions */
+
+static_always_inline void *
+map_guest_mem (vhost_user_intf_t * vui, uword addr, u32 * hint)
+{
+  int i = *hint;
+  if (PREDICT_TRUE ((vui->regions[i].guest_phys_addr <= addr) &&
+		    ((vui->regions[i].guest_phys_addr +
+		      vui->regions[i].memory_size) > addr)))
+    {
+      return (void *) (vui->region_mmap_addr[i] + addr -
+		       vui->regions[i].guest_phys_addr);
+    }
+#if __SSE4_2__
+  __m128i rl, rh, al, ah, r;
+  al = _mm_set1_epi64x (addr + 1);
+  ah = _mm_set1_epi64x (addr);
+
+  rl = _mm_loadu_si128 ((__m128i *) & vui->region_guest_addr_lo[0]);
+  rl = _mm_cmpgt_epi64 (al, rl);
+  rh = _mm_loadu_si128 ((__m128i *) & vui->region_guest_addr_hi[0]);
+  rh = _mm_cmpgt_epi64 (rh, ah);
+  r = _mm_and_si128 (rl, rh);
+
+  rl = _mm_loadu_si128 ((__m128i *) & vui->region_guest_addr_lo[2]);
+  rl = _mm_cmpgt_epi64 (al, rl);
+  rh = _mm_loadu_si128 ((__m128i *) & vui->region_guest_addr_hi[2]);
+  rh = _mm_cmpgt_epi64 (rh, ah);
+  r = _mm_blend_epi16 (r, _mm_and_si128 (rl, rh), 0x22);
+
+  rl = _mm_loadu_si128 ((__m128i *) & vui->region_guest_addr_lo[4]);
+  rl = _mm_cmpgt_epi64 (al, rl);
+  rh = _mm_loadu_si128 ((__m128i *) & vui->region_guest_addr_hi[4]);
+  rh = _mm_cmpgt_epi64 (rh, ah);
+  r = _mm_blend_epi16 (r, _mm_and_si128 (rl, rh), 0x44);
+
+  rl = _mm_loadu_si128 ((__m128i *) & vui->region_guest_addr_lo[6]);
+  rl = _mm_cmpgt_epi64 (al, rl);
+  rh = _mm_loadu_si128 ((__m128i *) & vui->region_guest_addr_hi[6]);
+  rh = _mm_cmpgt_epi64 (rh, ah);
+  r = _mm_blend_epi16 (r, _mm_and_si128 (rl, rh), 0x88);
+
+  r = _mm_shuffle_epi8 (r, _mm_set_epi64x (0, 0x0e060c040a020800));
+  i = count_trailing_zeros (_mm_movemask_epi8 (r) |
+			    (1 << VHOST_MEMORY_MAX_NREGIONS));
+
+  if (i < vui->nregions)
+    {
+      *hint = i;
+      return (void *) (vui->region_mmap_addr[i] + addr -
+		       vui->regions[i].guest_phys_addr);
+    }
+#elif __aarch64__ && __ARM_NEON
+  uint64x2_t al, ah, rl, rh, r;
+  uint32_t u32 = 0;
+
+  al = vdupq_n_u64 (addr + 1);
+  ah = vdupq_n_u64 (addr);
+
+  /*First Iteration */
+  rl = vld1q_u64 (&vui->region_guest_addr_lo[0]);
+  rl = vcgtq_u64 (al, rl);
+  rh = vld1q_u64 (&vui->region_guest_addr_hi[0]);
+  rh = vcgtq_u64 (rh, ah);
+  r = vandq_u64 (rl, rh);
+  u32 |= (vgetq_lane_u8 (vreinterpretq_u8_u64 (r), 0) & 0x1);
+  u32 |= ((vgetq_lane_u8 (vreinterpretq_u8_u64 (r), 8) & 0x1) << 1);
+
+  if (u32)
+    {
+      i = count_trailing_zeros (u32);
+      goto vhost_map_guest_mem_done;
+    }
+
+  /*Second Iteration */
+  rl = vld1q_u64 (&vui->region_guest_addr_lo[2]);
+  rl = vcgtq_u64 (al, rl);
+  rh = vld1q_u64 (&vui->region_guest_addr_hi[2]);
+  rh = vcgtq_u64 (rh, ah);
+  r = vandq_u64 (rl, rh);
+  u32 |= ((vgetq_lane_u8 (vreinterpretq_u8_u64 (r), 0) & 0x1) << 2);
+  u32 |= ((vgetq_lane_u8 (vreinterpretq_u8_u64 (r), 8) & 0x1) << 3);
+
+  if (u32)
+    {
+      i = count_trailing_zeros (u32);
+      goto vhost_map_guest_mem_done;
+    }
+
+  /*Third Iteration */
+  rl = vld1q_u64 (&vui->region_guest_addr_lo[4]);
+  rl = vcgtq_u64 (al, rl);
+  rh = vld1q_u64 (&vui->region_guest_addr_hi[4]);
+  rh = vcgtq_u64 (rh, ah);
+  r = vandq_u64 (rl, rh);
+  u32 |= ((vgetq_lane_u8 (vreinterpretq_u8_u64 (r), 0) & 0x1) << 6);
+  u32 |= ((vgetq_lane_u8 (vreinterpretq_u8_u64 (r), 8) & 0x1) << 7);
+
+  i = count_trailing_zeros (u32 | (1 << VHOST_MEMORY_MAX_NREGIONS));
+
+vhost_map_guest_mem_done:
+  if (i < vui->nregions)
+    {
+      *hint = i;
+      return (void *) (vui->region_mmap_addr[i] + addr -
+		       vui->regions[i].guest_phys_addr);
+    }
+#else
+  for (i = 0; i < vui->nregions; i++)
+    {
+      if ((vui->regions[i].guest_phys_addr <= addr) &&
+	  ((vui->regions[i].guest_phys_addr + vui->regions[i].memory_size) >
+	   addr))
+	{
+	  *hint = i;
+	  return (void *) (vui->region_mmap_addr[i] + addr -
+			   vui->regions[i].guest_phys_addr);
+	}
+    }
+#endif
+  DBG_VQ ("failed to map guest mem addr %llx", addr);
+  *hint = 0;
+  return 0;
+}
+
+static_always_inline void *
+map_user_mem (vhost_user_intf_t * vui, uword addr)
+{
+  int i;
+  for (i = 0; i < vui->nregions; i++)
+    {
+      if ((vui->regions[i].userspace_addr <= addr) &&
+	  ((vui->regions[i].userspace_addr + vui->regions[i].memory_size) >
+	   addr))
+	{
+	  return (void *) (vui->region_mmap_addr[i] + addr -
+			   vui->regions[i].userspace_addr);
+	}
+    }
+  return 0;
+}
+
+#define VHOST_LOG_PAGE 0x1000
+
+static_always_inline void
+vhost_user_log_dirty_pages_2 (vhost_user_intf_t * vui,
+			      u64 addr, u64 len, u8 is_host_address)
+{
+  if (PREDICT_TRUE (vui->log_base_addr == 0
+		    || !(vui->features & (1 << FEAT_VHOST_F_LOG_ALL))))
+    {
+      return;
+    }
+  if (is_host_address)
+    {
+      addr = pointer_to_uword (map_user_mem (vui, (uword) addr));
+    }
+  if (PREDICT_FALSE ((addr + len - 1) / VHOST_LOG_PAGE / 8 >= vui->log_size))
+    {
+      DBG_SOCK ("vhost_user_log_dirty_pages(): out of range\n");
+      return;
+    }
+
+  CLIB_MEMORY_BARRIER ();
+  u64 page = addr / VHOST_LOG_PAGE;
+  while (page * VHOST_LOG_PAGE < addr + len)
+    {
+      ((u8 *) vui->log_base_addr)[page / 8] |= 1 << page % 8;
+      page++;
+    }
+}
+
+
+#define vhost_user_log_dirty_ring(vui, vq, member) \
+  if (PREDICT_FALSE(vq->log_used)) { \
+    vhost_user_log_dirty_pages_2(vui, vq->log_guest_addr + STRUCT_OFFSET_OF(vring_used_t, member), \
+                             sizeof(vq->used->member), 0); \
+  }
+
+static_always_inline u8 *
+format_vhost_trace (u8 * s, va_list * va)
+{
+  CLIB_UNUSED (vlib_main_t * vm) = va_arg (*va, vlib_main_t *);
+  CLIB_UNUSED (vlib_node_t * node) = va_arg (*va, vlib_node_t *);
+  CLIB_UNUSED (vnet_main_t * vnm) = vnet_get_main ();
+  vhost_user_main_t *vum = &vhost_user_main;
+  vhost_trace_t *t = va_arg (*va, vhost_trace_t *);
+  vhost_user_intf_t *vui = pool_elt_at_index (vum->vhost_user_interfaces,
+					      t->device_index);
+
+  vnet_sw_interface_t *sw = vnet_get_sw_interface (vnm, vui->sw_if_index);
+
+  u32 indent = format_get_indent (s);
+
+  s = format (s, "%U %U queue %d\n", format_white_space, indent,
+	      format_vnet_sw_interface_name, vnm, sw, t->qid);
+
+  s = format (s, "%U virtio flags:\n", format_white_space, indent);
+#define _(n,i,st) \
+          if (t->virtio_ring_flags & (1 << VIRTIO_TRACE_F_##n)) \
+            s = format (s, "%U  %s %s\n", format_white_space, indent, #n, st);
+  foreach_virtio_trace_flags
+#undef _
+    s = format (s, "%U virtio_net_hdr first_desc_len %u\n",
+		format_white_space, indent, t->first_desc_len);
+
+  s = format (s, "%U   flags 0x%02x gso_type %u\n",
+	      format_white_space, indent,
+	      t->hdr.hdr.flags, t->hdr.hdr.gso_type);
+
+  if (vui->virtio_net_hdr_sz == 12)
+    s = format (s, "%U   num_buff %u",
+		format_white_space, indent, t->hdr.num_buffers);
+
+  return s;
+}
+
+static_always_inline void
+vhost_user_send_call (vlib_main_t * vm, vhost_user_vring_t * vq)
+{
+  vhost_user_main_t *vum = &vhost_user_main;
+  u64 x = 1;
+  int fd = UNIX_GET_FD (vq->callfd_idx);
+  int rv;
+
+  rv = write (fd, &x, sizeof (x));
+  if (rv <= 0)
+    {
+      clib_unix_warning
+	("Error: Could not write to unix socket for callfd %d", fd);
+      return;
+    }
+
+  vq->n_since_last_int = 0;
+  vq->int_deadline = vlib_time_now (vm) + vum->coalesce_time;
+}
+
+#endif
+
+/*
+ * fd.io coding-style-patch-verification: ON
+ *
+ * Local Variables:
+ * eval: (c-set-style "gnu")
+ * End:
+ */
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:
+ */
diff --git a/src/vnet/devices/virtio/vhost_user_output.c b/src/vnet/devices/virtio/vhost_user_output.c
new file mode 100644
index 00000000000..f400f18307a
--- /dev/null
+++ b/src/vnet/devices/virtio/vhost_user_output.c
@@ -0,0 +1,671 @@
+/*
+ *------------------------------------------------------------------
+ * vhost-user-output
+ *
+ * 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>
+
+/*
+ * On the transmit side, we keep processing the buffers from vlib in the while
+ * loop and prepare the copy order to be executed later. However, the static
+ * array which we keep the copy order is limited to VHOST_USER_COPY_ARRAY_N
+ * entries. In order to not corrupt memory, we have to do the copy when the
+ * static array reaches the copy threshold. We subtract 40 in case the code
+ * goes into the inner loop for a maximum of 64k frames which may require
+ * more array entries.
+ */
+#define VHOST_USER_TX_COPY_THRESHOLD (VHOST_USER_COPY_ARRAY_N - 40)
+
+vnet_device_class_t vhost_user_device_class;
+
+#define foreach_vhost_user_tx_func_error      \
+  _(NONE, "no error")  \
+  _(NOT_READY, "vhost vring not ready")  \
+  _(DOWN, "vhost interface is down")  \
+  _(PKT_DROP_NOBUF, "tx packet drops (no available descriptors)")  \
+  _(PKT_DROP_NOMRG, "tx packet drops (cannot merge descriptors)")  \
+  _(MMAP_FAIL, "mmap failure") \
+  _(INDIRECT_OVERFLOW, "indirect descriptor table overflow")
+
+typedef enum
+{
+#define _(f,s) VHOST_USER_TX_FUNC_ERROR_##f,
+  foreach_vhost_user_tx_func_error
+#undef _
+    VHOST_USER_TX_FUNC_N_ERROR,
+} vhost_user_tx_func_error_t;
+
+static __clib_unused char *vhost_user_tx_func_error_strings[] = {
+#define _(n,s) s,
+  foreach_vhost_user_tx_func_error
+#undef _
+};
+
+static __clib_unused u8 *
+format_vhost_user_interface_name (u8 * s, va_list * args)
+{
+  u32 i = va_arg (*args, u32);
+  u32 show_dev_instance = ~0;
+  vhost_user_main_t *vum = &vhost_user_main;
+
+  if (i < vec_len (vum->show_dev_instance_by_real_dev_instance))
+    show_dev_instance = vum->show_dev_instance_by_real_dev_instance[i];
+
+  if (show_dev_instance != ~0)
+    i = show_dev_instance;
+
+  s = format (s, "VirtualEthernet0/0/%d", i);
+  return s;
+}
+
+static __clib_unused int
+vhost_user_name_renumber (vnet_hw_interface_t * hi, u32 new_dev_instance)
+{
+  // FIXME: check if the new dev instance is already used
+  vhost_user_main_t *vum = &vhost_user_main;
+  vec_validate_init_empty (vum->show_dev_instance_by_real_dev_instance,
+			   hi->dev_instance, ~0);
+
+  vum->show_dev_instance_by_real_dev_instance[hi->dev_instance] =
+    new_dev_instance;
+
+  DBG_SOCK ("renumbered vhost-user interface dev_instance %d to %d",
+	    hi->dev_instance, new_dev_instance);
+
+  return 0;
+}
+
+/**
+ * @brief Try once to lock the vring
+ * @return 0 on success, non-zero on failure.
+ */
+static_always_inline int
+vhost_user_vring_try_lock (vhost_user_intf_t * vui, u32 qid)
+{
+  return __sync_lock_test_and_set (vui->vring_locks[qid], 1);
+}
+
+/**
+ * @brief Spin until the vring is successfully locked
+ */
+static_always_inline void
+vhost_user_vring_lock (vhost_user_intf_t * vui, u32 qid)
+{
+  while (vhost_user_vring_try_lock (vui, qid))
+    ;
+}
+
+/**
+ * @brief Unlock the vring lock
+ */
+static_always_inline void
+vhost_user_vring_unlock (vhost_user_intf_t * vui, u32 qid)
+{
+  *vui->vring_locks[qid] = 0;
+}
+
+static_always_inline void
+vhost_user_tx_trace (vhost_trace_t * t,
+		     vhost_user_intf_t * vui, u16 qid,
+		     vlib_buffer_t * b, vhost_user_vring_t * rxvq)
+{
+  vhost_user_main_t *vum = &vhost_user_main;
+  u32 last_avail_idx = rxvq->last_avail_idx;
+  u32 desc_current = rxvq->avail->ring[last_avail_idx & rxvq->qsz_mask];
+  vring_desc_t *hdr_desc = 0;
+  u32 hint = 0;
+
+  memset (t, 0, sizeof (*t));
+  t->device_index = vui - vum->vhost_user_interfaces;
+  t->qid = qid;
+
+  hdr_desc = &rxvq->desc[desc_current];
+  if (rxvq->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, rxvq->desc[desc_current].addr, &hint);
+    }
+  if (rxvq->desc[desc_current].flags & VIRTQ_DESC_F_NEXT)
+    {
+      t->virtio_ring_flags |= 1 << VIRTIO_TRACE_F_SIMPLE_CHAINED;
+    }
+  if (!(rxvq->desc[desc_current].flags & VIRTQ_DESC_F_NEXT) &&
+      !(rxvq->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;
+}
+
+static_always_inline u32
+vhost_user_tx_copy (vhost_user_intf_t * vui, vhost_copy_t * cpy,
+		    u16 copy_len, u32 * map_hint)
+{
+  void *dst0, *dst1, *dst2, *dst3;
+  if (PREDICT_TRUE (copy_len >= 4))
+    {
+      if (PREDICT_FALSE (!(dst2 = map_guest_mem (vui, cpy[0].dst, map_hint))))
+	return 1;
+      if (PREDICT_FALSE (!(dst3 = map_guest_mem (vui, cpy[1].dst, map_hint))))
+	return 1;
+      while (PREDICT_TRUE (copy_len >= 4))
+	{
+	  dst0 = dst2;
+	  dst1 = dst3;
+
+	  if (PREDICT_FALSE
+	      (!(dst2 = map_guest_mem (vui, cpy[2].dst, map_hint))))
+	    return 1;
+	  if (PREDICT_FALSE
+	      (!(dst3 = map_guest_mem (vui, cpy[3].dst, map_hint))))
+	    return 1;
+
+	  CLIB_PREFETCH ((void *) cpy[2].src, 64, LOAD);
+	  CLIB_PREFETCH ((void *) cpy[3].src, 64, LOAD);
+
+	  clib_memcpy (dst0, (void *) cpy[0].src, cpy[0].len);
+	  clib_memcpy (dst1, (void *) cpy[1].src, cpy[1].len);
+
+	  vhost_user_log_dirty_pages_2 (vui, cpy[0].dst, cpy[0].len, 1);
+	  vhost_user_log_dirty_pages_2 (vui, cpy[1].dst, cpy[1].len, 1);
+	  copy_len -= 2;
+	  cpy += 2;
+	}
+    }
+  while (copy_len)
+    {
+      if (PREDICT_FALSE (!(dst0 = map_guest_mem (vui, cpy->dst, map_hint))))
+	return 1;
+      clib_memcpy (dst0, (void *) cpy->src, cpy->len);
+      vhost_user_log_dirty_pages_2 (vui, cpy->dst, cpy->len, 1);
+      copy_len -= 1;
+      cpy += 1;
+    }
+  return 0;
+}
+
+
+uword
+CLIB_MULTIARCH_FN (vhost_user_tx) (vlib_main_t * vm,
+				   vlib_node_runtime_t * node,
+				   vlib_frame_t * frame)
+{
+  u32 *buffers = vlib_frame_args (frame);
+  u32 n_left = frame->n_vectors;
+  vhost_user_main_t *vum = &vhost_user_main;
+  vnet_interface_output_runtime_t *rd = (void *) node->runtime_data;
+  vhost_user_intf_t *vui =
+    pool_elt_at_index (vum->vhost_user_interfaces, rd->dev_instance);
+  u32 qid = ~0;
+  vhost_user_vring_t *rxvq;
+  u8 error;
+  u32 thread_index = vlib_get_thread_index ();
+  u32 map_hint = 0;
+  u8 retry = 8;
+  u16 copy_len;
+  u16 tx_headers_len;
+
+  if (PREDICT_FALSE (!vui->admin_up))
+    {
+      error = VHOST_USER_TX_FUNC_ERROR_DOWN;
+      goto done3;
+    }
+
+  if (PREDICT_FALSE (!vui->is_up))
+    {
+      error = VHOST_USER_TX_FUNC_ERROR_NOT_READY;
+      goto done3;
+    }
+
+  qid =
+    VHOST_VRING_IDX_RX (*vec_elt_at_index
+			(vui->per_cpu_tx_qid, thread_index));
+  rxvq = &vui->vrings[qid];
+  if (PREDICT_FALSE (vui->use_tx_spinlock))
+    vhost_user_vring_lock (vui, qid);
+
+retry:
+  error = VHOST_USER_TX_FUNC_ERROR_NONE;
+  tx_headers_len = 0;
+  copy_len = 0;
+  while (n_left > 0)
+    {
+      vlib_buffer_t *b0, *current_b0;
+      u16 desc_head, desc_index, desc_len;
+      vring_desc_t *desc_table;
+      uword buffer_map_addr;
+      u32 buffer_len;
+      u16 bytes_left;
+
+      if (PREDICT_TRUE (n_left > 1))
+	vlib_prefetch_buffer_with_index (vm, buffers[1], LOAD);
+
+      b0 = vlib_get_buffer (vm, buffers[0]);
+
+      if (PREDICT_FALSE (b0->flags & VLIB_BUFFER_IS_TRACED))
+	{
+	  vum->cpus[thread_index].current_trace =
+	    vlib_add_trace (vm, node, b0,
+			    sizeof (*vum->cpus[thread_index].current_trace));
+	  vhost_user_tx_trace (vum->cpus[thread_index].current_trace,
+			       vui, qid / 2, b0, rxvq);
+	}
+
+      if (PREDICT_FALSE (rxvq->last_avail_idx == rxvq->avail->idx))
+	{
+	  error = VHOST_USER_TX_FUNC_ERROR_PKT_DROP_NOBUF;
+	  goto done;
+	}
+
+      desc_table = rxvq->desc;
+      desc_head = desc_index =
+	rxvq->avail->ring[rxvq->last_avail_idx & rxvq->qsz_mask];
+
+      /* Go deeper in case of indirect descriptor
+       * I don't know of any driver providing indirect for RX. */
+      if (PREDICT_FALSE (rxvq->desc[desc_head].flags & VIRTQ_DESC_F_INDIRECT))
+	{
+	  if (PREDICT_FALSE
+	      (rxvq->desc[desc_head].len < sizeof (vring_desc_t)))
+	    {
+	      error = VHOST_USER_TX_FUNC_ERROR_INDIRECT_OVERFLOW;
+	      goto done;
+	    }
+	  if (PREDICT_FALSE
+	      (!(desc_table =
+		 map_guest_mem (vui, rxvq->desc[desc_index].addr,
+				&map_hint))))
+	    {
+	      error = VHOST_USER_TX_FUNC_ERROR_MMAP_FAIL;
+	      goto done;
+	    }
+	  desc_index = 0;
+	}
+
+      desc_len = vui->virtio_net_hdr_sz;
+      buffer_map_addr = desc_table[desc_index].addr;
+      buffer_len = desc_table[desc_index].len;
+
+      {
+	// Get a header from the header array
+	virtio_net_hdr_mrg_rxbuf_t *hdr =
+	  &vum->cpus[thread_index].tx_headers[tx_headers_len];
+	tx_headers_len++;
+	hdr->hdr.flags = 0;
+	hdr->hdr.gso_type = 0;
+	hdr->num_buffers = 1;	//This is local, no need to check
+
+	// Prepare a copy order executed later for the header
+	vhost_copy_t *cpy = &vum->cpus[thread_index].copy[copy_len];
+	copy_len++;
+	cpy->len = vui->virtio_net_hdr_sz;
+	cpy->dst = buffer_map_addr;
+	cpy->src = (uword) hdr;
+      }
+
+      buffer_map_addr += vui->virtio_net_hdr_sz;
+      buffer_len -= vui->virtio_net_hdr_sz;
+      bytes_left = b0->current_length;
+      current_b0 = b0;
+      while (1)
+	{
+	  if (buffer_len == 0)
+	    {			//Get new output
+	      if (desc_table[desc_index].flags & VIRTQ_DESC_F_NEXT)
+		{
+		  //Next one is chained
+		  desc_index = desc_table[desc_index].next;
+		  buffer_map_addr = desc_table[desc_index].addr;
+		  buffer_len = desc_table[desc_index].len;
+		}
+	      else if (vui->virtio_net_hdr_sz == 12)	//MRG is available
+		{
+		  virtio_net_hdr_mrg_rxbuf_t *hdr =
+		    &vum->cpus[thread_index].tx_headers[tx_headers_len - 1];
+
+		  //Move from available to used buffer
+		  rxvq->used->ring[rxvq->last_used_idx & rxvq->qsz_mask].id =
+		    desc_head;
+		  rxvq->used->ring[rxvq->last_used_idx & rxvq->qsz_mask].len =
+		    desc_len;
+		  vhost_user_log_dirty_ring (vui, rxvq,
+					     ring[rxvq->last_used_idx &
+						  rxvq->qsz_mask]);
+
+		  rxvq->last_avail_idx++;
+		  rxvq->last_used_idx++;
+		  hdr->num_buffers++;
+		  desc_len = 0;
+
+		  if (PREDICT_FALSE
+		      (rxvq->last_avail_idx == rxvq->avail->idx))
+		    {
+		      //Dequeue queued descriptors for this packet
+		      rxvq->last_used_idx -= hdr->num_buffers - 1;
+		      rxvq->last_avail_idx -= hdr->num_buffers - 1;
+		      error = VHOST_USER_TX_FUNC_ERROR_PKT_DROP_NOBUF;
+		      goto done;
+		    }
+
+		  desc_table = rxvq->desc;
+		  desc_head = desc_index =
+		    rxvq->avail->ring[rxvq->last_avail_idx & rxvq->qsz_mask];
+		  if (PREDICT_FALSE
+		      (rxvq->desc[desc_head].flags & VIRTQ_DESC_F_INDIRECT))
+		    {
+		      //It is seriously unlikely that a driver will put indirect descriptor
+		      //after non-indirect descriptor.
+		      if (PREDICT_FALSE
+			  (rxvq->desc[desc_head].len < sizeof (vring_desc_t)))
+			{
+			  error = VHOST_USER_TX_FUNC_ERROR_INDIRECT_OVERFLOW;
+			  goto done;
+			}
+		      if (PREDICT_FALSE
+			  (!(desc_table =
+			     map_guest_mem (vui,
+					    rxvq->desc[desc_index].addr,
+					    &map_hint))))
+			{
+			  error = VHOST_USER_TX_FUNC_ERROR_MMAP_FAIL;
+			  goto done;
+			}
+		      desc_index = 0;
+		    }
+		  buffer_map_addr = desc_table[desc_index].addr;
+		  buffer_len = desc_table[desc_index].len;
+		}
+	      else
+		{
+		  error = VHOST_USER_TX_FUNC_ERROR_PKT_DROP_NOMRG;
+		  goto done;
+		}
+	    }
+
+	  {
+	    vhost_copy_t *cpy = &vum->cpus[thread_index].copy[copy_len];
+	    copy_len++;
+	    cpy->len = bytes_left;
+	    cpy->len = (cpy->len > buffer_len) ? buffer_len : cpy->len;
+	    cpy->dst = buffer_map_addr;
+	    cpy->src = (uword) vlib_buffer_get_current (current_b0) +
+	      current_b0->current_length - bytes_left;
+
+	    bytes_left -= cpy->len;
+	    buffer_len -= cpy->len;
+	    buffer_map_addr += cpy->len;
+	    desc_len += cpy->len;
+
+	    CLIB_PREFETCH (&rxvq->desc, CLIB_CACHE_LINE_BYTES, LOAD);
+	  }
+
+	  // Check if vlib buffer has more data. If not, get more or break.
+	  if (PREDICT_TRUE (!bytes_left))
+	    {
+	      if (PREDICT_FALSE
+		  (current_b0->flags & VLIB_BUFFER_NEXT_PRESENT))
+		{
+		  current_b0 = vlib_get_buffer (vm, current_b0->next_buffer);
+		  bytes_left = current_b0->current_length;
+		}
+	      else
+		{
+		  //End of packet
+		  break;
+		}
+	    }
+	}
+
+      //Move from available to used ring
+      rxvq->used->ring[rxvq->last_used_idx & rxvq->qsz_mask].id = desc_head;
+      rxvq->used->ring[rxvq->last_used_idx & rxvq->qsz_mask].len = desc_len;
+      vhost_user_log_dirty_ring (vui, rxvq,
+				 ring[rxvq->last_used_idx & rxvq->qsz_mask]);
+      rxvq->last_avail_idx++;
+      rxvq->last_used_idx++;
+
+      if (PREDICT_FALSE (b0->flags & VLIB_BUFFER_IS_TRACED))
+	{
+	  vum->cpus[thread_index].current_trace->hdr =
+	    vum->cpus[thread_index].tx_headers[tx_headers_len - 1];
+	}
+
+      n_left--;			//At the end for error counting when 'goto done' is invoked
+
+      /*
+       * Do the copy periodically to prevent
+       * vum->cpus[thread_index].copy array overflow and corrupt memory
+       */
+      if (PREDICT_FALSE (copy_len >= VHOST_USER_TX_COPY_THRESHOLD))
+	{
+	  if (PREDICT_FALSE
+	      (vhost_user_tx_copy (vui, vum->cpus[thread_index].copy,
+				   copy_len, &map_hint)))
+	    {
+	      vlib_error_count (vm, node->node_index,
+				VHOST_USER_TX_FUNC_ERROR_MMAP_FAIL, 1);
+	    }
+	  copy_len = 0;
+
+	  /* give buffers back to driver */
+	  CLIB_MEMORY_BARRIER ();
+	  rxvq->used->idx = rxvq->last_used_idx;
+	  vhost_user_log_dirty_ring (vui, rxvq, idx);
+	}
+      buffers++;
+    }
+
+done:
+  //Do the memory copies
+  if (PREDICT_FALSE
+      (vhost_user_tx_copy (vui, vum->cpus[thread_index].copy,
+			   copy_len, &map_hint)))
+    {
+      vlib_error_count (vm, node->node_index,
+			VHOST_USER_TX_FUNC_ERROR_MMAP_FAIL, 1);
+    }
+
+  CLIB_MEMORY_BARRIER ();
+  rxvq->used->idx = rxvq->last_used_idx;
+  vhost_user_log_dirty_ring (vui, rxvq, idx);
+
+  /*
+   * When n_left is set, error is always set to something too.
+   * In case error is due to lack of remaining buffers, we go back up and
+   * retry.
+   * The idea is that it is better to waste some time on packets
+   * that have been processed already than dropping them and get
+   * more fresh packets with a good likelyhood that they will be dropped too.
+   * This technique also gives more time to VM driver to pick-up packets.
+   * In case the traffic flows from physical to virtual interfaces, this
+   * technique will end-up leveraging the physical NIC buffer in order to
+   * absorb the VM's CPU jitter.
+   */
+  if (n_left && (error == VHOST_USER_TX_FUNC_ERROR_PKT_DROP_NOBUF) && retry)
+    {
+      retry--;
+      goto retry;
+    }
+
+  /* interrupt (call) handling */
+  if ((rxvq->callfd_idx != ~0) &&
+      !(rxvq->avail->flags & VRING_AVAIL_F_NO_INTERRUPT))
+    {
+      rxvq->n_since_last_int += frame->n_vectors - n_left;
+
+      if (rxvq->n_since_last_int > vum->coalesce_frames)
+	vhost_user_send_call (vm, rxvq);
+    }
+
+  vhost_user_vring_unlock (vui, qid);
+
+done3:
+  if (PREDICT_FALSE (n_left && error != VHOST_USER_TX_FUNC_ERROR_NONE))
+    {
+      vlib_error_count (vm, node->node_index, error, n_left);
+      vlib_increment_simple_counter
+	(vnet_main.interface_main.sw_if_counters
+	 + VNET_INTERFACE_COUNTER_DROP,
+	 thread_index, vui->sw_if_index, n_left);
+    }
+
+  vlib_buffer_free (vm, vlib_frame_args (frame), frame->n_vectors);
+  return frame->n_vectors;
+}
+
+static __clib_unused clib_error_t *
+vhost_user_interface_rx_mode_change (vnet_main_t * vnm, u32 hw_if_index,
+				     u32 qid, vnet_hw_interface_rx_mode mode)
+{
+  vlib_main_t *vm = vnm->vlib_main;
+  vnet_hw_interface_t *hif = vnet_get_hw_interface (vnm, hw_if_index);
+  vhost_user_main_t *vum = &vhost_user_main;
+  vhost_user_intf_t *vui =
+    pool_elt_at_index (vum->vhost_user_interfaces, hif->dev_instance);
+  vhost_user_vring_t *txvq = &vui->vrings[VHOST_VRING_IDX_TX (qid)];
+
+  if ((mode == VNET_HW_INTERFACE_RX_MODE_INTERRUPT) ||
+      (mode == VNET_HW_INTERFACE_RX_MODE_ADAPTIVE))
+    {
+      if (txvq->kickfd_idx == ~0)
+	{
+	  // We cannot support interrupt mode if the driver opts out
+	  return clib_error_return (0, "Driver does not support interrupt");
+	}
+      if (txvq->mode == VNET_HW_INTERFACE_RX_MODE_POLLING)
+	{
+	  vum->ifq_count++;
+	  // Start the timer if this is the first encounter on interrupt
+	  // interface/queue
+	  if ((vum->ifq_count == 1) &&
+	      (vum->coalesce_time > 0.0) && (vum->coalesce_frames > 0))
+	    vlib_process_signal_event (vm,
+				       vhost_user_send_interrupt_node.index,
+				       VHOST_USER_EVENT_START_TIMER, 0);
+	}
+    }
+  else if (mode == VNET_HW_INTERFACE_RX_MODE_POLLING)
+    {
+      if (((txvq->mode == VNET_HW_INTERFACE_RX_MODE_INTERRUPT) ||
+	   (txvq->mode == VNET_HW_INTERFACE_RX_MODE_ADAPTIVE)) &&
+	  vum->ifq_count)
+	{
+	  vum->ifq_count--;
+	  // Stop the timer if there is no more interrupt interface/queue
+	  if ((vum->ifq_count == 0) &&
+	      (vum->coalesce_time > 0.0) && (vum->coalesce_frames > 0))
+	    vlib_process_signal_event (vm,
+				       vhost_user_send_interrupt_node.index,
+				       VHOST_USER_EVENT_STOP_TIMER, 0);
+	}
+    }
+
+  txvq->mode = mode;
+  if (mode == VNET_HW_INTERFACE_RX_MODE_POLLING)
+    txvq->used->flags = VRING_USED_F_NO_NOTIFY;
+  else if ((mode == VNET_HW_INTERFACE_RX_MODE_ADAPTIVE) ||
+	   (mode == VNET_HW_INTERFACE_RX_MODE_INTERRUPT))
+    txvq->used->flags = 0;
+  else
+    {
+      clib_warning ("BUG: unhandled mode %d changed for if %d queue %d", mode,
+		    hw_if_index, qid);
+      return clib_error_return (0, "unsupported");
+    }
+
+  return 0;
+}
+
+static __clib_unused clib_error_t *
+vhost_user_interface_admin_up_down (vnet_main_t * vnm, u32 hw_if_index,
+				    u32 flags)
+{
+  vnet_hw_interface_t *hif = vnet_get_hw_interface (vnm, hw_if_index);
+  vhost_user_main_t *vum = &vhost_user_main;
+  vhost_user_intf_t *vui =
+    pool_elt_at_index (vum->vhost_user_interfaces, hif->dev_instance);
+  u32 hw_flags = 0;
+  vui->admin_up = (flags & VNET_SW_INTERFACE_FLAG_ADMIN_UP) != 0;
+  hw_flags = vui->admin_up ? VNET_HW_INTERFACE_FLAG_LINK_UP : 0;
+
+  vnet_hw_interface_set_flags (vnm, vui->hw_if_index, hw_flags);
+
+  return /* no error */ 0;
+}
+
+#ifndef CLIB_MARCH_VARIANT
+/* *INDENT-OFF* */
+VNET_DEVICE_CLASS (vhost_user_device_class) = {
+  .name = "vhost-user",
+  .tx_function = vhost_user_tx,
+  .tx_function_n_errors = VHOST_USER_TX_FUNC_N_ERROR,
+  .tx_function_error_strings = vhost_user_tx_func_error_strings,
+  .format_device_name = format_vhost_user_interface_name,
+  .name_renumber = vhost_user_name_renumber,
+  .admin_up_down_function = vhost_user_interface_admin_up_down,
+  .rx_mode_change_function = vhost_user_interface_rx_mode_change,
+  .format_tx_trace = format_vhost_trace,
+};
+
+#if __x86_64__
+vlib_node_function_t __clib_weak vhost_user_tx_avx512;
+vlib_node_function_t __clib_weak vhost_user_tx_avx2;
+static void __clib_constructor
+vhost_user_tx_multiarch_select (void)
+{
+  if (vhost_user_tx_avx512 && clib_cpu_supports_avx512f ())
+    vhost_user_device_class.tx_function = vhost_user_tx_avx512;
+  else if (vhost_user_tx_avx2 && clib_cpu_supports_avx2 ())
+    vhost_user_device_class.tx_function = vhost_user_tx_avx2;
+}
+#endif
+#endif
+
+/* *INDENT-ON* */
+
+/*
+ * fd.io coding-style-patch-verification: ON
+ *
+ * Local Variables:
+ * eval: (c-set-style "gnu")
+ * End:
+ */