vhost: convert vhost device driver to a plugin

convert vhost device driver to a plugin as described in
https://jira.fd.io/browse/VPP-2065

Type: improvement

Signed-off-by: Steven Luong <sluong@cisco.com>
Change-Id: Ibfe2f351bcaed36a04b136d082ae414145dd37b5

1 files changed, 1145 insertions, 0 deletions

diff --git a/src/plugins/vhost/vhost_user_output.c b/src/plugins/vhost/vhost_user_output.c
new file mode 100644
index 00000000000..9b52fc6265c
--- /dev/null
+++ b/src/plugins/vhost/vhost_user_output.c
@@ -0,0 +1,1145 @@
+/*
+ *------------------------------------------------------------------
+ * 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 <stddef.h>
+#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/ethernet/ethernet.h>
+#include <vnet/devices/devices.h>
+#include <vnet/feature/feature.h>
+#include <vnet/ip/ip_psh_cksum.h>
+
+#include <vhost/vhost_user.h>
+#include <vhost/vhost_user_inline.h>
+
+#include <vnet/gso/hdr_offset_parser.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. We subtract 200 because our default buffer size is
+ * 2048 and the default desc len is likely 1536. While it takes less than 40
+ * vlib buffers for the jumbo frame, it may take twice as much descriptors
+ * for the same jumbo frame. Use 200 for the extra head room.
+ */
+#define VHOST_USER_TX_COPY_THRESHOLD (VHOST_USER_COPY_ARRAY_N - 200)
+
+extern 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;
+  vhost_user_intf_t *vui = pool_elt_at_index (vum->vhost_user_interfaces,
+					      hi->dev_instance);
+
+  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;
+
+  vu_log_debug (vui, "renumbered vhost-user interface dev_instance %d to %d",
+		hi->dev_instance, new_dev_instance);
+
+  return 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];
+  vnet_virtio_vring_desc_t *hdr_desc = 0;
+  u32 hint = 0;
+
+  clib_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 & VRING_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 & VRING_DESC_F_NEXT)
+    {
+      t->virtio_ring_flags |= 1 << VIRTIO_TRACE_F_SIMPLE_CHAINED;
+    }
+  if (!(rxvq->desc[desc_current].flags & VRING_DESC_F_NEXT) &&
+      !(rxvq->desc[desc_current].flags & VRING_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_load ((void *) cpy[2].src);
+	  clib_prefetch_load ((void *) cpy[3].src);
+
+	  clib_memcpy_fast (dst0, (void *) cpy[0].src, cpy[0].len);
+	  clib_memcpy_fast (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_fast (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_always_inline void
+vhost_user_handle_tx_offload (vhost_user_intf_t *vui, vlib_buffer_t *b,
+			      vnet_virtio_net_hdr_t *hdr)
+{
+  generic_header_offset_t gho = { 0 };
+  int is_ip4 = b->flags & VNET_BUFFER_F_IS_IP4;
+  int is_ip6 = b->flags & VNET_BUFFER_F_IS_IP6;
+  vnet_buffer_oflags_t oflags = vnet_buffer (b)->oflags;
+  u16 psh_cksum = 0;
+  ip4_header_t *ip4 = 0;
+  ip6_header_t *ip6 = 0;
+
+  ASSERT (!(is_ip4 && is_ip6));
+  vnet_generic_header_offset_parser (b, &gho, 1 /* l2 */ , is_ip4, is_ip6);
+  if (oflags & VNET_BUFFER_OFFLOAD_F_IP_CKSUM)
+    {
+      ip4 =
+	(ip4_header_t *) (vlib_buffer_get_current (b) + gho.l3_hdr_offset);
+      ip4->checksum = ip4_header_checksum (ip4);
+      psh_cksum = ip4_pseudo_header_cksum (ip4);
+    }
+  else
+    {
+      ip6 = (ip6_header_t *) (vlib_buffer_get_current (b) + gho.l3_hdr_offset);
+      psh_cksum = ip6_pseudo_header_cksum (ip6);
+    }
+
+  /* checksum offload */
+  if (oflags & VNET_BUFFER_OFFLOAD_F_UDP_CKSUM)
+    {
+      udp_header_t *udp =
+	(udp_header_t *) (vlib_buffer_get_current (b) + gho.l4_hdr_offset);
+      udp->checksum = psh_cksum;
+      hdr->flags = VIRTIO_NET_HDR_F_NEEDS_CSUM;
+      hdr->csum_start = gho.l4_hdr_offset;
+      hdr->csum_offset = offsetof (udp_header_t, checksum);
+    }
+  else if (oflags & VNET_BUFFER_OFFLOAD_F_TCP_CKSUM)
+    {
+      tcp_header_t *tcp =
+	(tcp_header_t *) (vlib_buffer_get_current (b) + gho.l4_hdr_offset);
+      tcp->checksum = psh_cksum;
+      hdr->flags = VIRTIO_NET_HDR_F_NEEDS_CSUM;
+      hdr->csum_start = gho.l4_hdr_offset;
+      hdr->csum_offset = offsetof (tcp_header_t, checksum);
+    }
+
+  /* GSO offload */
+  if (b->flags & VNET_BUFFER_F_GSO)
+    {
+      if (oflags & VNET_BUFFER_OFFLOAD_F_TCP_CKSUM)
+	{
+	  if (is_ip4 &&
+	      (vui->features & VIRTIO_FEATURE (VIRTIO_NET_F_GUEST_TSO4)))
+	    {
+	      hdr->gso_size = vnet_buffer2 (b)->gso_size;
+	      hdr->gso_type = VIRTIO_NET_HDR_GSO_TCPV4;
+	    }
+	  else if (is_ip6 &&
+		   (vui->features & VIRTIO_FEATURE (VIRTIO_NET_F_GUEST_TSO6)))
+	    {
+	      hdr->gso_size = vnet_buffer2 (b)->gso_size;
+	      hdr->gso_type = VIRTIO_NET_HDR_GSO_TCPV6;
+	    }
+	}
+      else if ((vui->features & VIRTIO_FEATURE (VIRTIO_NET_F_GUEST_UFO)) &&
+	       (oflags & VNET_BUFFER_OFFLOAD_F_UDP_CKSUM))
+	{
+	  hdr->gso_size = vnet_buffer2 (b)->gso_size;
+	  hdr->gso_type = VIRTIO_NET_HDR_GSO_UDP;
+	}
+    }
+}
+
+static_always_inline void
+vhost_user_mark_desc_available (vlib_main_t * vm, vhost_user_intf_t * vui,
+				vhost_user_vring_t * rxvq,
+				u16 * n_descs_processed, u8 chained,
+				vlib_frame_t * frame, u32 n_left)
+{
+  u16 desc_idx, flags;
+  vnet_virtio_vring_packed_desc_t *desc_table = rxvq->packed_desc;
+  u16 last_used_idx = rxvq->last_used_idx;
+
+  if (PREDICT_FALSE (*n_descs_processed == 0))
+    return;
+
+  if (rxvq->used_wrap_counter)
+    flags = desc_table[last_used_idx & rxvq->qsz_mask].flags |
+      (VRING_DESC_F_AVAIL | VRING_DESC_F_USED);
+  else
+    flags = desc_table[last_used_idx & rxvq->qsz_mask].flags &
+      ~(VRING_DESC_F_AVAIL | VRING_DESC_F_USED);
+
+  vhost_user_advance_last_used_idx (rxvq);
+
+  for (desc_idx = 1; desc_idx < *n_descs_processed; desc_idx++)
+    {
+      if (rxvq->used_wrap_counter)
+	desc_table[rxvq->last_used_idx & rxvq->qsz_mask].flags |=
+	  (VRING_DESC_F_AVAIL | VRING_DESC_F_USED);
+      else
+	desc_table[rxvq->last_used_idx & rxvq->qsz_mask].flags &=
+	  ~(VRING_DESC_F_AVAIL | VRING_DESC_F_USED);
+      vhost_user_advance_last_used_idx (rxvq);
+    }
+
+  desc_table[last_used_idx & rxvq->qsz_mask].flags = flags;
+
+  *n_descs_processed = 0;
+
+  if (chained)
+    {
+      vnet_virtio_vring_packed_desc_t *desc_table = rxvq->packed_desc;
+
+      while (desc_table[rxvq->last_used_idx & rxvq->qsz_mask].flags &
+	     VRING_DESC_F_NEXT)
+	vhost_user_advance_last_used_idx (rxvq);
+
+      /* Advance past the current chained table entries */
+      vhost_user_advance_last_used_idx (rxvq);
+    }
+
+  /* interrupt (call) handling */
+  if ((rxvq->callfd_idx != ~0) &&
+      (rxvq->avail_event->flags != VRING_EVENT_F_DISABLE))
+    {
+      vhost_user_main_t *vum = &vhost_user_main;
+
+      rxvq->n_since_last_int += frame->n_vectors - n_left;
+      if (rxvq->n_since_last_int > vum->coalesce_frames)
+	vhost_user_send_call (vm, vui, rxvq);
+    }
+}
+
+static_always_inline void
+vhost_user_tx_trace_packed (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 = last_avail_idx & rxvq->qsz_mask;
+  vnet_virtio_vring_packed_desc_t *hdr_desc = 0;
+  u32 hint = 0;
+
+  clib_memset (t, 0, sizeof (*t));
+  t->device_index = vui - vum->vhost_user_interfaces;
+  t->qid = qid;
+
+  hdr_desc = &rxvq->packed_desc[desc_current];
+  if (rxvq->packed_desc[desc_current].flags & VRING_DESC_F_INDIRECT)
+    {
+      t->virtio_ring_flags |= 1 << VIRTIO_TRACE_F_INDIRECT;
+      /* Header is the first here */
+      hdr_desc = map_guest_mem (vui, rxvq->packed_desc[desc_current].addr,
+				&hint);
+    }
+  if (rxvq->packed_desc[desc_current].flags & VRING_DESC_F_NEXT)
+    {
+      t->virtio_ring_flags |= 1 << VIRTIO_TRACE_F_SIMPLE_CHAINED;
+    }
+  if (!(rxvq->packed_desc[desc_current].flags & VRING_DESC_F_NEXT) &&
+      !(rxvq->packed_desc[desc_current].flags & VRING_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 uword
+vhost_user_device_class_packed (vlib_main_t *vm, vlib_node_runtime_t *node,
+				vlib_frame_t *frame, vhost_user_intf_t *vui,
+				vhost_user_vring_t *rxvq)
+{
+  u32 *buffers = vlib_frame_vector_args (frame);
+  u32 n_left = frame->n_vectors;
+  vhost_user_main_t *vum = &vhost_user_main;
+  u32 qid = rxvq->qid;
+  u8 error;
+  u32 thread_index = vm->thread_index;
+  vhost_cpu_t *cpu = &vum->cpus[thread_index];
+  u32 map_hint = 0;
+  u8 retry = 8;
+  u16 copy_len;
+  u16 tx_headers_len;
+  vnet_virtio_vring_packed_desc_t *desc_table;
+  u32 or_flags;
+  u16 desc_head, desc_index, desc_len;
+  u16 n_descs_processed;
+  u8 indirect, chained;
+
+retry:
+  error = VHOST_USER_TX_FUNC_ERROR_NONE;
+  tx_headers_len = 0;
+  copy_len = 0;
+  n_descs_processed = 0;
+
+  while (n_left > 0)
+    {
+      vlib_buffer_t *b0, *current_b0;
+      uword buffer_map_addr;
+      u32 buffer_len;
+      u16 bytes_left;
+      u32 total_desc_len = 0;
+      u16 n_entries = 0;
+
+      indirect = 0;
+      chained = 0;
+      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))
+	{
+	  cpu->current_trace = vlib_add_trace (vm, node, b0,
+					       sizeof (*cpu->current_trace));
+	  vhost_user_tx_trace_packed (cpu->current_trace, vui, qid / 2, b0,
+				      rxvq);
+	}
+
+      desc_table = rxvq->packed_desc;
+      desc_head = desc_index = rxvq->last_avail_idx & rxvq->qsz_mask;
+      if (PREDICT_FALSE (!vhost_user_packed_desc_available (rxvq, desc_head)))
+	{
+	  error = VHOST_USER_TX_FUNC_ERROR_PKT_DROP_NOBUF;
+	  goto done;
+	}
+      /*
+       * Go deeper in case of indirect descriptor.
+       * To test it, turn off mrg_rxbuf.
+       */
+      if (desc_table[desc_head].flags & VRING_DESC_F_INDIRECT)
+	{
+	  indirect = 1;
+	  if (PREDICT_FALSE (desc_table[desc_head].len <
+			     sizeof (vnet_virtio_vring_packed_desc_t)))
+	    {
+	      error = VHOST_USER_TX_FUNC_ERROR_INDIRECT_OVERFLOW;
+	      goto done;
+	    }
+	  n_entries = desc_table[desc_head].len >> 4;
+	  desc_table = map_guest_mem (vui, desc_table[desc_index].addr,
+				      &map_hint);
+	  if (PREDICT_FALSE (desc_table == 0))
+	    {
+	      error = VHOST_USER_TX_FUNC_ERROR_MMAP_FAIL;
+	      goto done;
+	    }
+	  desc_index = 0;
+	}
+      else if (rxvq->packed_desc[desc_head].flags & VRING_DESC_F_NEXT)
+	chained = 1;
+
+      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 */
+      vnet_virtio_net_hdr_mrg_rxbuf_t *hdr = &cpu->tx_headers[tx_headers_len];
+      tx_headers_len++;
+      hdr->hdr.flags = 0;
+      hdr->hdr.gso_type = VIRTIO_NET_HDR_GSO_NONE;
+      hdr->num_buffers = 1;
+
+      or_flags = (b0->flags & VNET_BUFFER_F_OFFLOAD);
+
+      /* Guest supports csum offload and buffer requires checksum offload? */
+      if (or_flags &&
+	  (vui->features & VIRTIO_FEATURE (VIRTIO_NET_F_GUEST_CSUM)))
+	vhost_user_handle_tx_offload (vui, b0, &hdr->hdr);
+
+      /* Prepare a copy order executed later for the header */
+      ASSERT (copy_len < VHOST_USER_COPY_ARRAY_N);
+      vhost_copy_t *cpy = &cpu->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 (chained)
+		{
+		  /*
+		   * Next one is chained
+		   * Test it with both indirect and mrg_rxbuf off
+		   */
+		  if (PREDICT_FALSE (!(desc_table[desc_index].flags &
+				       VRING_DESC_F_NEXT)))
+		    {
+		      /*
+		       * Last descriptor in chain.
+		       * Dequeue queued descriptors for this packet
+		       */
+		      vhost_user_dequeue_chained_descs (rxvq,
+							&n_descs_processed);
+		      error = VHOST_USER_TX_FUNC_ERROR_PKT_DROP_NOBUF;
+		      goto done;
+		    }
+		  vhost_user_advance_last_avail_idx (rxvq);
+		  desc_index = rxvq->last_avail_idx & rxvq->qsz_mask;
+		  n_descs_processed++;
+		  buffer_map_addr = desc_table[desc_index].addr;
+		  buffer_len = desc_table[desc_index].len;
+		  total_desc_len += desc_len;
+		  desc_len = 0;
+		}
+	      else if (indirect)
+		{
+		  /*
+		   * Indirect table
+		   * Test it with mrg_rxnuf off
+		   */
+		  if (PREDICT_TRUE (n_entries > 0))
+		    n_entries--;
+		  else
+		    {
+		      /* Dequeue queued descriptors for this packet */
+		      vhost_user_dequeue_chained_descs (rxvq,
+							&n_descs_processed);
+		      error = VHOST_USER_TX_FUNC_ERROR_INDIRECT_OVERFLOW;
+		      goto done;
+		    }
+		  total_desc_len += desc_len;
+		  desc_index = (desc_index + 1) & rxvq->qsz_mask;
+		  buffer_map_addr = desc_table[desc_index].addr;
+		  buffer_len = desc_table[desc_index].len;
+		  desc_len = 0;
+		}
+	      else if (vui->virtio_net_hdr_sz == 12)
+		{
+		  /*
+		   * MRG is available
+		   * This is the default setting for the guest VM
+		   */
+		  vnet_virtio_net_hdr_mrg_rxbuf_t *hdr =
+		    &cpu->tx_headers[tx_headers_len - 1];
+
+		  desc_table[desc_index].len = desc_len;
+		  vhost_user_advance_last_avail_idx (rxvq);
+		  desc_head = desc_index =
+		    rxvq->last_avail_idx & rxvq->qsz_mask;
+		  hdr->num_buffers++;
+		  n_descs_processed++;
+		  desc_len = 0;
+
+		  if (PREDICT_FALSE (!vhost_user_packed_desc_available
+				     (rxvq, desc_index)))
+		    {
+		      /* Dequeue queued descriptors for this packet */
+		      vhost_user_dequeue_descs (rxvq, hdr,
+						&n_descs_processed);
+		      error = VHOST_USER_TX_FUNC_ERROR_PKT_DROP_NOBUF;
+		      goto done;
+		    }
+
+		  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;
+		}
+	    }
+
+	  ASSERT (copy_len < VHOST_USER_COPY_ARRAY_N);
+	  vhost_copy_t *cpy = &cpu->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_load (&rxvq->packed_desc);
+
+	  /* 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 */
+      total_desc_len += desc_len;
+      rxvq->packed_desc[desc_head].len = total_desc_len;
+
+      vhost_user_advance_last_avail_table_idx (vui, rxvq, chained);
+      n_descs_processed++;
+
+      if (PREDICT_FALSE (b0->flags & VLIB_BUFFER_IS_TRACED))
+	cpu->current_trace->hdr = cpu->tx_headers[tx_headers_len - 1];
+
+      n_left--;
+
+      /*
+       * Do the copy periodically to prevent
+       * cpu->copy array overflow and corrupt memory
+       */
+      if (PREDICT_FALSE (copy_len >= VHOST_USER_TX_COPY_THRESHOLD) || chained)
+	{
+	  if (PREDICT_FALSE (vhost_user_tx_copy (vui, cpu->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 */
+	  vhost_user_mark_desc_available (vm, vui, rxvq, &n_descs_processed,
+					  chained, frame, n_left);
+	}
+
+      buffers++;
+    }
+
+done:
+  if (PREDICT_TRUE (copy_len))
+    {
+      if (PREDICT_FALSE (vhost_user_tx_copy (vui, cpu->copy, copy_len,
+					     &map_hint)))
+	vlib_error_count (vm, node->node_index,
+			  VHOST_USER_TX_FUNC_ERROR_MMAP_FAIL, 1);
+
+      vhost_user_mark_desc_available (vm, vui, rxvq, &n_descs_processed,
+				      chained, frame, n_left);
+    }
+
+  /*
+   * 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;
+    }
+
+  clib_spinlock_unlock (&rxvq->vring_lock);
+
+  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_vector_args (frame), frame->n_vectors);
+  return frame->n_vectors;
+}
+
+VNET_DEVICE_CLASS_TX_FN (vhost_user_device_class) (vlib_main_t * vm,
+						   vlib_node_runtime_t *
+						   node, vlib_frame_t * frame)
+{
+  u32 *buffers = vlib_frame_vector_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;
+  vhost_user_vring_t *rxvq;
+  u8 error;
+  u32 thread_index = vm->thread_index;
+  vhost_cpu_t *cpu = &vum->cpus[thread_index];
+  u32 map_hint = 0;
+  u8 retry = 8;
+  u16 copy_len;
+  u16 tx_headers_len;
+  u32 or_flags;
+  vnet_hw_if_tx_frame_t *tf = vlib_frame_scalar_args (frame);
+
+  if (PREDICT_FALSE (!vui->admin_up))
+    {
+      error = VHOST_USER_TX_FUNC_ERROR_DOWN;
+      goto done3;
+    }
+
+  if (PREDICT_FALSE (!vui->is_ready))
+    {
+      error = VHOST_USER_TX_FUNC_ERROR_NOT_READY;
+      goto done3;
+    }
+
+  qid = VHOST_VRING_IDX_RX (tf->queue_id);
+  rxvq = &vui->vrings[qid];
+  ASSERT (tf->queue_id == rxvq->qid);
+
+  if (PREDICT_FALSE (rxvq->avail == 0))
+    {
+      error = VHOST_USER_TX_FUNC_ERROR_MMAP_FAIL;
+      goto done3;
+    }
+  if (tf->shared_queue)
+    clib_spinlock_lock (&rxvq->vring_lock);
+
+  if (vhost_user_is_packed_ring_supported (vui))
+    return (vhost_user_device_class_packed (vm, node, frame, vui, rxvq));
+
+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;
+      vnet_virtio_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))
+	{
+	  cpu->current_trace = vlib_add_trace (vm, node, b0,
+					       sizeof (*cpu->current_trace));
+	  vhost_user_tx_trace (cpu->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 & VRING_DESC_F_INDIRECT))
+	{
+	  if (PREDICT_FALSE (rxvq->desc[desc_head].len <
+			     sizeof (vnet_virtio_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
+	vnet_virtio_net_hdr_mrg_rxbuf_t *hdr =
+	  &cpu->tx_headers[tx_headers_len];
+	tx_headers_len++;
+	hdr->hdr.flags = 0;
+	hdr->hdr.gso_type = VIRTIO_NET_HDR_GSO_NONE;
+	hdr->num_buffers = 1;	//This is local, no need to check
+
+	or_flags = (b0->flags & VNET_BUFFER_F_OFFLOAD);
+
+	/* Guest supports csum offload and buffer requires checksum offload? */
+	if (or_flags
+	    && (vui->features & VIRTIO_FEATURE (VIRTIO_NET_F_GUEST_CSUM)))
+	  vhost_user_handle_tx_offload (vui, b0, &hdr->hdr);
+
+	// Prepare a copy order executed later for the header
+	ASSERT (copy_len < VHOST_USER_COPY_ARRAY_N);
+	vhost_copy_t *cpy = &cpu->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 & VRING_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
+		{
+		  vnet_virtio_net_hdr_mrg_rxbuf_t *hdr =
+		    &cpu->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 & VRING_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 (vnet_virtio_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;
+		}
+	    }
+
+	  {
+	    ASSERT (copy_len < VHOST_USER_COPY_ARRAY_N);
+	    vhost_copy_t *cpy = &cpu->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_load (&rxvq->desc);
+	  }
+
+	  // 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))
+	{
+	  cpu->current_trace->hdr = cpu->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
+       * cpu->copy array overflow and corrupt memory
+       */
+      if (PREDICT_FALSE (copy_len >= VHOST_USER_TX_COPY_THRESHOLD))
+	{
+	  if (PREDICT_FALSE (vhost_user_tx_copy (vui, cpu->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, cpu->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 likelihood 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, vui, rxvq);
+    }
+
+  clib_spinlock_unlock (&rxvq->vring_lock);
+
+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_vector_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_if_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)];
+  vhost_cpu_t *cpu;
+
+  if (mode == txvq->mode)
+    return 0;
+
+  if ((mode != VNET_HW_IF_RX_MODE_POLLING) &&
+      (mode != VNET_HW_IF_RX_MODE_ADAPTIVE) &&
+      (mode != VNET_HW_IF_RX_MODE_INTERRUPT))
+    {
+      vu_log_err (vui, "unhandled mode %d changed for if %d queue %d", mode,
+		  hw_if_index, qid);
+      return clib_error_return (0, "unsupported");
+    }
+
+  if (txvq->thread_index == ~0)
+    return clib_error_return (0, "Queue initialization is not finished yet");
+
+  cpu = vec_elt_at_index (vum->cpus, txvq->thread_index);
+  if ((mode == VNET_HW_IF_RX_MODE_INTERRUPT) ||
+      (mode == VNET_HW_IF_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_IF_RX_MODE_POLLING)
+	{
+	  ASSERT (cpu->polling_q_count != 0);
+	  if (cpu->polling_q_count)
+	    cpu->polling_q_count--;
+	  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_IF_RX_MODE_POLLING)
+    {
+      if (((txvq->mode == VNET_HW_IF_RX_MODE_INTERRUPT) ||
+	   (txvq->mode == VNET_HW_IF_RX_MODE_ADAPTIVE)) && vum->ifq_count)
+	{
+	  cpu->polling_q_count++;
+	  vum->ifq_count--;
+	  // Stop the timer if there is no more interrupt interface/queue
+	  if (vum->ifq_count == 0)
+	    vlib_process_signal_event (vm,
+				       vhost_user_send_interrupt_node.index,
+				       VHOST_USER_EVENT_STOP_TIMER, 0);
+	}
+    }
+
+  txvq->mode = mode;
+  vhost_user_set_operation_mode (vui, txvq);
+
+  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);
+  u8 link_old, link_new;
+
+  link_old = vui_is_link_up (vui);
+
+  vui->admin_up = (flags & VNET_SW_INTERFACE_FLAG_ADMIN_UP) != 0;
+
+  link_new = vui_is_link_up (vui);
+
+  if (link_old != link_new)
+    vnet_hw_interface_set_flags (vnm, vui->hw_if_index, link_new ?
+				 VNET_HW_INTERFACE_FLAG_LINK_UP : 0);
+
+  return /* no error */ 0;
+}
+
+/* *INDENT-OFF* */
+VNET_DEVICE_CLASS (vhost_user_device_class) = {
+  .name = "vhost-user",
+  .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,
+};
+
+/* *INDENT-ON* */
+
+/*
+ * fd.io coding-style-patch-verification: ON
+ *
+ * Local Variables:
+ * eval: (c-set-style "gnu")
+ * End:
+ */