Imported Upstream version 16.04

Change-Id: I77eadcd8538a9122e4773cbe55b24033dc451757
Signed-off-by: C.J. Collier <cjcollier@linuxfoundation.org>

7 files changed, 3290 insertions, 0 deletions

diff --git a/examples/vhost_xen/Makefile b/examples/vhost_xen/Makefile
new file mode 100644
index 00000000..47e14898
--- /dev/null
+++ b/examples/vhost_xen/Makefile
@@ -0,0 +1,52 @@
+#   BSD LICENSE
+#
+#   Copyright(c) 2010-2014 Intel Corporation. All rights reserved.
+#   All rights reserved.
+#
+#   Redistribution and use in source and binary forms, with or without
+#   modification, are permitted provided that the following conditions
+#   are met:
+#
+#     * Redistributions of source code must retain the above copyright
+#       notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above copyright
+#       notice, this list of conditions and the following disclaimer in
+#       the documentation and/or other materials provided with the
+#       distribution.
+#     * Neither the name of Intel Corporation nor the names of its
+#       contributors may be used to endorse or promote products derived
+#       from this software without specific prior written permission.
+#
+#   THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+#   "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+#   LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+#   A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+#   OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+#   SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+#   LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+#   DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+#   THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+#   (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+#   OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+ifeq ($(RTE_SDK),)
+$(error "Please define RTE_SDK environment variable")
+endif
+
+# Default target, can be overriden by command line or environment
+RTE_TARGET ?= x86_64-native-linuxapp-gcc
+
+include $(RTE_SDK)/mk/rte.vars.mk
+
+# binary name
+APP = vhost-switch
+
+# all source are stored in SRCS-y
+SRCS-y := main.c vhost_monitor.c xenstore_parse.c
+
+CFLAGS += -O2 -I/usr/local/include -D_FILE_OFFSET_BITS=64 -Wno-unused-parameter
+CFLAGS += $(WERROR_FLAGS)
+CFLAGS += -D_GNU_SOURCE
+LDFLAGS += -lxenstore
+
+include $(RTE_SDK)/mk/rte.extapp.mk
diff --git a/examples/vhost_xen/main.c b/examples/vhost_xen/main.c
new file mode 100644
index 00000000..d83138d6
--- /dev/null
+++ b/examples/vhost_xen/main.c
@@ -0,0 +1,1530 @@
+/*-
+ *   BSD LICENSE
+ *
+ *   Copyright(c) 2010-2015 Intel Corporation. All rights reserved.
+ *   All rights reserved.
+ *
+ *   Redistribution and use in source and binary forms, with or without
+ *   modification, are permitted provided that the following conditions
+ *   are met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ *       notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above copyright
+ *       notice, this list of conditions and the following disclaimer in
+ *       the documentation and/or other materials provided with the
+ *       distribution.
+ *     * Neither the name of Intel Corporation nor the names of its
+ *       contributors may be used to endorse or promote products derived
+ *       from this software without specific prior written permission.
+ *
+ *   THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ *   "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ *   LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ *   A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ *   OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ *   SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ *   LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ *   DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ *   THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ *   (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ *   OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <arpa/inet.h>
+#include <getopt.h>
+#include <linux/if_ether.h>
+#include <linux/if_vlan.h>
+#include <linux/virtio_net.h>
+#include <linux/virtio_ring.h>
+#include <signal.h>
+#include <stdint.h>
+#include <sys/eventfd.h>
+#include <sys/param.h>
+#include <unistd.h>
+
+#include <rte_atomic.h>
+#include <rte_cycles.h>
+#include <rte_ethdev.h>
+#include <rte_log.h>
+#include <rte_string_fns.h>
+
+#include "main.h"
+#include "virtio-net.h"
+#include "xen_vhost.h"
+
+#define MAX_QUEUES 128
+
+/* the maximum number of external ports supported */
+#define MAX_SUP_PORTS 1
+
+/*
+ * Calculate the number of buffers needed per port
+ */
+#define NUM_MBUFS_PER_PORT ((MAX_QUEUES*RTE_TEST_RX_DESC_DEFAULT) +		\
+							(num_switching_cores*MAX_PKT_BURST) +  			\
+							(num_switching_cores*RTE_TEST_TX_DESC_DEFAULT) +\
+							(num_switching_cores*MBUF_CACHE_SIZE))
+
+#define MBUF_CACHE_SIZE 64
+
+/*
+ * RX and TX Prefetch, Host, and Write-back threshold values should be
+ * carefully set for optimal performance. Consult the network
+ * controller's datasheet and supporting DPDK documentation for guidance
+ * on how these parameters should be set.
+ */
+#define RX_PTHRESH 8 /* Default values of RX prefetch threshold reg. */
+#define RX_HTHRESH 8 /* Default values of RX host threshold reg. */
+#define RX_WTHRESH 4 /* Default values of RX write-back threshold reg. */
+
+/*
+ * These default values are optimized for use with the Intel(R) 82599 10 GbE
+ * Controller and the DPDK ixgbe PMD. Consider using other values for other
+ * network controllers and/or network drivers.
+ */
+#define TX_PTHRESH 36 /* Default values of TX prefetch threshold reg. */
+#define TX_HTHRESH 0  /* Default values of TX host threshold reg. */
+#define TX_WTHRESH 0  /* Default values of TX write-back threshold reg. */
+
+#define MAX_PKT_BURST 32		/* Max burst size for RX/TX */
+#define MAX_MRG_PKT_BURST 16	/* Max burst for merge buffers. Set to 1 due to performance issue. */
+#define BURST_TX_DRAIN_US 100	/* TX drain every ~100us */
+
+/* State of virtio device. */
+#define DEVICE_NOT_READY     0
+#define DEVICE_READY         1
+#define DEVICE_SAFE_REMOVE   2
+
+/* Config_core_flag status definitions. */
+#define REQUEST_DEV_REMOVAL 1
+#define ACK_DEV_REMOVAL 0
+
+/* Configurable number of RX/TX ring descriptors */
+#define RTE_TEST_RX_DESC_DEFAULT 128
+#define RTE_TEST_TX_DESC_DEFAULT 512
+
+#define INVALID_PORT_ID 0xFF
+
+/* Max number of devices. Limited by vmdq. */
+#define MAX_DEVICES 64
+
+/* Size of buffers used for snprintfs. */
+#define MAX_PRINT_BUFF 6072
+
+
+/* Maximum long option length for option parsing. */
+#define MAX_LONG_OPT_SZ 64
+
+/* Used to compare MAC addresses. */
+#define MAC_ADDR_CMP 0xFFFFFFFFFFFF
+
+/* mask of enabled ports */
+static uint32_t enabled_port_mask = 0;
+
+/*Number of switching cores enabled*/
+static uint32_t num_switching_cores = 0;
+
+/* number of devices/queues to support*/
+static uint32_t num_queues = 0;
+uint32_t num_devices = 0;
+
+/* Enable VM2VM communications. If this is disabled then the MAC address compare is skipped. */
+static uint32_t enable_vm2vm = 1;
+/* Enable stats. */
+static uint32_t enable_stats = 0;
+
+/* empty vmdq configuration structure. Filled in programatically */
+static const struct rte_eth_conf vmdq_conf_default = {
+	.rxmode = {
+		.mq_mode        = ETH_MQ_RX_VMDQ_ONLY,
+		.split_hdr_size = 0,
+		.header_split   = 0, /**< Header Split disabled */
+		.hw_ip_checksum = 0, /**< IP checksum offload disabled */
+		.hw_vlan_filter = 0, /**< VLAN filtering disabled */
+		/*
+		 * It is necessary for 1G NIC such as I350,
+		 * this fixes bug of ipv4 forwarding in guest can't
+		 * forward pakets from one virtio dev to another virtio dev.
+		 */
+		.hw_vlan_strip  = 1, /**< VLAN strip enabled. */
+		.jumbo_frame    = 0, /**< Jumbo Frame Support disabled */
+		.hw_strip_crc   = 0, /**< CRC stripped by hardware */
+	},
+
+	.txmode = {
+		.mq_mode = ETH_MQ_TX_NONE,
+	},
+	.rx_adv_conf = {
+		/*
+		 * should be overridden separately in code with
+		 * appropriate values
+		 */
+		.vmdq_rx_conf = {
+			.nb_queue_pools = ETH_8_POOLS,
+			.enable_default_pool = 0,
+			.default_pool = 0,
+			.nb_pool_maps = 0,
+			.pool_map = {{0, 0},},
+		},
+	},
+};
+
+static unsigned lcore_ids[RTE_MAX_LCORE];
+static uint8_t ports[RTE_MAX_ETHPORTS];
+static unsigned num_ports = 0; /**< The number of ports specified in command line */
+
+const uint16_t vlan_tags[] = {
+	1000, 1001, 1002, 1003, 1004, 1005, 1006, 1007,
+	1008, 1009, 1010, 1011,	1012, 1013, 1014, 1015,
+	1016, 1017, 1018, 1019, 1020, 1021, 1022, 1023,
+	1024, 1025, 1026, 1027, 1028, 1029, 1030, 1031,
+	1032, 1033, 1034, 1035, 1036, 1037, 1038, 1039,
+	1040, 1041, 1042, 1043, 1044, 1045, 1046, 1047,
+	1048, 1049, 1050, 1051, 1052, 1053, 1054, 1055,
+	1056, 1057, 1058, 1059, 1060, 1061, 1062, 1063,
+};
+
+/* ethernet addresses of ports */
+static struct ether_addr vmdq_ports_eth_addr[RTE_MAX_ETHPORTS];
+
+/* heads for the main used and free linked lists for the data path. */
+static struct virtio_net_data_ll *ll_root_used = NULL;
+static struct virtio_net_data_ll *ll_root_free = NULL;
+
+/* Array of data core structures containing information on individual core linked lists. */
+static struct lcore_info lcore_info[RTE_MAX_LCORE];
+
+/* Used for queueing bursts of TX packets. */
+struct mbuf_table {
+	unsigned len;
+	unsigned txq_id;
+	struct rte_mbuf *m_table[MAX_PKT_BURST];
+};
+
+/* TX queue for each data core. */
+struct mbuf_table lcore_tx_queue[RTE_MAX_LCORE];
+
+/* Vlan header struct used to insert vlan tags on TX. */
+struct vlan_ethhdr {
+	unsigned char   h_dest[ETH_ALEN];
+	unsigned char   h_source[ETH_ALEN];
+	__be16          h_vlan_proto;
+	__be16          h_vlan_TCI;
+	__be16          h_vlan_encapsulated_proto;
+};
+
+/* Header lengths. */
+#define VLAN_HLEN       4
+#define VLAN_ETH_HLEN   18
+
+/* Per-device statistics struct */
+struct device_statistics {
+	uint64_t tx_total;
+	rte_atomic64_t rx_total;
+	uint64_t tx;
+	rte_atomic64_t rx;
+} __rte_cache_aligned;
+struct device_statistics dev_statistics[MAX_DEVICES];
+
+/*
+ * Builds up the correct configuration for VMDQ VLAN pool map
+ * according to the pool & queue limits.
+ */
+static inline int
+get_eth_conf(struct rte_eth_conf *eth_conf, uint32_t num_devices)
+{
+	struct rte_eth_vmdq_rx_conf conf;
+	unsigned i;
+
+	memset(&conf, 0, sizeof(conf));
+	conf.nb_queue_pools = (enum rte_eth_nb_pools)num_devices;
+	conf.nb_pool_maps = num_devices;
+
+	for (i = 0; i < conf.nb_pool_maps; i++) {
+		conf.pool_map[i].vlan_id = vlan_tags[ i ];
+		conf.pool_map[i].pools = (1UL << i);
+	}
+
+	(void)(rte_memcpy(eth_conf, &vmdq_conf_default, sizeof(*eth_conf)));
+	(void)(rte_memcpy(&eth_conf->rx_adv_conf.vmdq_rx_conf, &conf,
+		   sizeof(eth_conf->rx_adv_conf.vmdq_rx_conf)));
+	return 0;
+}
+
+/*
+ * Validate the device number according to the max pool number gotten form dev_info
+ * If the device number is invalid, give the error message and return -1.
+ * Each device must have its own pool.
+ */
+static inline int
+validate_num_devices(uint32_t max_nb_devices)
+{
+	if (num_devices > max_nb_devices) {
+		RTE_LOG(ERR, VHOST_PORT, "invalid number of devices\n");
+		return -1;
+	}
+	return 0;
+}
+
+/*
+ * Initialises a given port using global settings and with the rx buffers
+ * coming from the mbuf_pool passed as parameter
+ */
+static inline int
+port_init(uint8_t port, struct rte_mempool *mbuf_pool)
+{
+	struct rte_eth_dev_info dev_info;
+	struct rte_eth_rxconf *rxconf;
+	struct rte_eth_conf port_conf;
+	uint16_t rx_rings, tx_rings = (uint16_t)rte_lcore_count();
+	const uint16_t rx_ring_size = RTE_TEST_RX_DESC_DEFAULT, tx_ring_size = RTE_TEST_TX_DESC_DEFAULT;
+	int retval;
+	uint16_t q;
+
+	/* The max pool number from dev_info will be used to validate the pool number specified in cmd line */
+	rte_eth_dev_info_get (port, &dev_info);
+
+	/*configure the number of supported virtio devices based on VMDQ limits */
+	num_devices = dev_info.max_vmdq_pools;
+	num_queues = dev_info.max_rx_queues;
+
+	retval = validate_num_devices(MAX_DEVICES);
+	if (retval < 0)
+		return retval;
+
+	/* Get port configuration. */
+	retval = get_eth_conf(&port_conf, num_devices);
+	if (retval < 0)
+		return retval;
+
+	if (port >= rte_eth_dev_count()) return -1;
+
+	rx_rings = (uint16_t)num_queues,
+	/* Configure ethernet device. */
+	retval = rte_eth_dev_configure(port, rx_rings, tx_rings, &port_conf);
+	if (retval != 0)
+		return retval;
+
+	rte_eth_dev_info_get(port, &dev_info);
+	rxconf = &dev_info.default_rxconf;
+	rxconf->rx_drop_en = 1;
+	/* Setup the queues. */
+	for (q = 0; q < rx_rings; q ++) {
+		retval = rte_eth_rx_queue_setup(port, q, rx_ring_size,
+						rte_eth_dev_socket_id(port), rxconf,
+						mbuf_pool);
+		if (retval < 0)
+			return retval;
+	}
+	for (q = 0; q < tx_rings; q ++) {
+		retval = rte_eth_tx_queue_setup(port, q, tx_ring_size,
+						rte_eth_dev_socket_id(port),
+						NULL);
+		if (retval < 0)
+			return retval;
+	}
+
+	/* Start the device. */
+	retval  = rte_eth_dev_start(port);
+	if (retval < 0)
+		return retval;
+
+	rte_eth_macaddr_get(port, &vmdq_ports_eth_addr[port]);
+	RTE_LOG(INFO, VHOST_PORT, "Max virtio devices supported: %u\n", num_devices);
+	RTE_LOG(INFO, VHOST_PORT, "Port %u MAC: %02"PRIx8" %02"PRIx8" %02"PRIx8
+			" %02"PRIx8" %02"PRIx8" %02"PRIx8"\n",
+			(unsigned)port,
+			vmdq_ports_eth_addr[port].addr_bytes[0],
+			vmdq_ports_eth_addr[port].addr_bytes[1],
+			vmdq_ports_eth_addr[port].addr_bytes[2],
+			vmdq_ports_eth_addr[port].addr_bytes[3],
+			vmdq_ports_eth_addr[port].addr_bytes[4],
+			vmdq_ports_eth_addr[port].addr_bytes[5]);
+
+	return 0;
+}
+
+/*
+ * Parse the portmask provided at run time.
+ */
+static int
+parse_portmask(const char *portmask)
+{
+	char *end = NULL;
+	unsigned long pm;
+
+	errno = 0;
+
+	/* parse hexadecimal string */
+	pm = strtoul(portmask, &end, 16);
+	if ((portmask[0] == '\0') || (end == NULL) || (*end != '\0') || (errno != 0))
+		return -1;
+
+	if (pm == 0)
+		return -1;
+
+	return pm;
+
+}
+
+/*
+ * Parse num options at run time.
+ */
+static int
+parse_num_opt(const char *q_arg, uint32_t max_valid_value)
+{
+	char *end = NULL;
+	unsigned long num;
+
+	errno = 0;
+
+	/* parse unsigned int string */
+	num = strtoul(q_arg, &end, 10);
+	if ((q_arg[0] == '\0') || (end == NULL) || (*end != '\0') || (errno != 0))
+		return -1;
+
+	if (num > max_valid_value)
+		return -1;
+
+	return num;
+
+}
+
+/*
+ * Display usage
+ */
+static void
+us_vhost_usage(const char *prgname)
+{
+	RTE_LOG(INFO, VHOST_CONFIG, "%s [EAL options] -- -p PORTMASK --vm2vm [0|1] --stats [0-N] --nb-devices ND\n"
+	"		-p PORTMASK: Set mask for ports to be used by application\n"
+	"		--vm2vm [0|1]: disable/enable(default) vm2vm comms\n"
+	"		--stats [0-N]: 0: Disable stats, N: Time in seconds to print stats\n",
+	       prgname);
+}
+
+/*
+ * Parse the arguments given in the command line of the application.
+ */
+static int
+us_vhost_parse_args(int argc, char **argv)
+{
+	int opt, ret;
+	int option_index;
+	unsigned i;
+	const char *prgname = argv[0];
+	static struct option long_option[] = {
+		{"vm2vm", required_argument, NULL, 0},
+		{"stats", required_argument, NULL, 0},
+		{NULL, 0, 0, 0}
+	};
+
+	/* Parse command line */
+	while ((opt = getopt_long(argc, argv, "p:",long_option, &option_index)) != EOF) {
+		switch (opt) {
+		/* Portmask */
+		case 'p':
+			enabled_port_mask = parse_portmask(optarg);
+			if (enabled_port_mask == 0) {
+				RTE_LOG(INFO, VHOST_CONFIG, "Invalid portmask\n");
+				us_vhost_usage(prgname);
+				return -1;
+			}
+			break;
+
+		case 0:
+			/* Enable/disable vm2vm comms. */
+			if (!strncmp(long_option[option_index].name, "vm2vm", MAX_LONG_OPT_SZ)) {
+				ret = parse_num_opt(optarg, 1);
+				if (ret == -1) {
+					RTE_LOG(INFO, VHOST_CONFIG, "Invalid argument for vm2vm [0|1]\n");
+					us_vhost_usage(prgname);
+					return -1;
+				} else {
+					enable_vm2vm = ret;
+				}
+			}
+
+			/* Enable/disable stats. */
+			if (!strncmp(long_option[option_index].name, "stats", MAX_LONG_OPT_SZ)) {
+				ret = parse_num_opt(optarg, INT32_MAX);
+				if (ret == -1) {
+					RTE_LOG(INFO, VHOST_CONFIG, "Invalid argument for stats [0..N]\n");
+					us_vhost_usage(prgname);
+					return -1;
+				} else {
+					enable_stats = ret;
+				}
+			}
+			break;
+
+			/* Invalid option - print options. */
+		default:
+			us_vhost_usage(prgname);
+			return -1;
+		}
+	}
+
+	for (i = 0; i < RTE_MAX_ETHPORTS; i++) {
+		if (enabled_port_mask & (1 << i))
+			ports[num_ports++] = (uint8_t)i;
+	}
+
+	if ((num_ports ==  0) || (num_ports > MAX_SUP_PORTS)) {
+		RTE_LOG(INFO, VHOST_PORT, "Current enabled port number is %u,"
+			"but only %u port can be enabled\n",num_ports, MAX_SUP_PORTS);
+		return -1;
+	}
+
+	return 0;
+}
+
+/*
+ * Update the global var NUM_PORTS and array PORTS according to system ports number
+ * and return valid ports number
+ */
+static unsigned check_ports_num(unsigned nb_ports)
+{
+	unsigned valid_num_ports = num_ports;
+	unsigned portid;
+
+	if (num_ports > nb_ports) {
+		RTE_LOG(INFO, VHOST_PORT, "\nSpecified port number(%u) exceeds total system port number(%u)\n",
+			num_ports, nb_ports);
+		num_ports = nb_ports;
+	}
+
+	for (portid = 0; portid < num_ports; portid ++) {
+		if (ports[portid] >= nb_ports) {
+			RTE_LOG(INFO, VHOST_PORT, "\nSpecified port ID(%u) exceeds max system port ID(%u)\n",
+				ports[portid], (nb_ports - 1));
+			ports[portid] = INVALID_PORT_ID;
+			valid_num_ports--;
+		}
+	}
+	return valid_num_ports;
+}
+
+/*
+ * Macro to print out packet contents. Wrapped in debug define so that the
+ * data path is not effected when debug is disabled.
+ */
+#ifdef DEBUG
+#define PRINT_PACKET(device, addr, size, header) do {																\
+	char *pkt_addr = (char*)(addr);																					\
+	unsigned int index;																								\
+	char packet[MAX_PRINT_BUFF];																					\
+																													\
+	if ((header))																									\
+		snprintf(packet, MAX_PRINT_BUFF, "(%"PRIu64") Header size %d: ", (device->device_fh), (size));				\
+	else																											\
+		snprintf(packet, MAX_PRINT_BUFF, "(%"PRIu64") Packet size %d: ", (device->device_fh), (size));				\
+	for (index = 0; index < (size); index++) {																		\
+		snprintf(packet + strnlen(packet, MAX_PRINT_BUFF), MAX_PRINT_BUFF - strnlen(packet, MAX_PRINT_BUFF),	\
+			"%02hhx ", pkt_addr[index]);																			\
+	}																												\
+	snprintf(packet + strnlen(packet, MAX_PRINT_BUFF), MAX_PRINT_BUFF - strnlen(packet, MAX_PRINT_BUFF), "\n");	\
+																													\
+	LOG_DEBUG(VHOST_DATA, "%s", packet);																					\
+} while(0)
+#else
+#define PRINT_PACKET(device, addr, size, header) do{} while(0)
+#endif
+
+/*
+ * Function to convert guest physical addresses to vhost virtual addresses. This
+ * is used to convert virtio buffer addresses.
+ */
+static inline uint64_t __attribute__((always_inline))
+gpa_to_vva(struct virtio_net *dev, uint64_t guest_pa)
+{
+	struct virtio_memory_regions *region;
+	uint32_t regionidx;
+	uint64_t vhost_va = 0;
+
+	for (regionidx = 0; regionidx < dev->mem->nregions; regionidx++) {
+		region = &dev->mem->regions[regionidx];
+		if ((guest_pa >= region->guest_phys_address) &&
+			(guest_pa <= region->guest_phys_address_end)) {
+			vhost_va = region->address_offset + guest_pa;
+			break;
+		}
+	}
+	LOG_DEBUG(VHOST_DATA, "(%"PRIu64") GPA %p| VVA %p\n",
+		dev->device_fh, (void*)(uintptr_t)guest_pa, (void*)(uintptr_t)vhost_va);
+
+	return vhost_va;
+}
+
+/*
+ * This function adds buffers to the virtio devices RX virtqueue. Buffers can
+ * be received from the physical port or from another virtio device. A packet
+ * count is returned to indicate the number of packets that were succesfully
+ * added to the RX queue.
+ */
+static inline uint32_t __attribute__((always_inline))
+virtio_dev_rx(struct virtio_net *dev, struct rte_mbuf **pkts, uint32_t count)
+{
+	struct vhost_virtqueue *vq;
+	struct vring_desc *desc;
+	struct rte_mbuf *buff;
+	/* The virtio_hdr is initialised to 0. */
+	struct virtio_net_hdr_mrg_rxbuf virtio_hdr = {{0,0,0,0,0,0},0};
+	uint64_t buff_addr = 0;
+	uint64_t buff_hdr_addr = 0;
+	uint32_t head[MAX_PKT_BURST], packet_len = 0;
+	uint32_t head_idx, packet_success = 0;
+	uint16_t avail_idx, res_cur_idx;
+	uint16_t res_base_idx, res_end_idx;
+	uint16_t free_entries;
+	uint8_t success = 0;
+	void *userdata;
+
+	LOG_DEBUG(VHOST_DATA, "(%"PRIu64") virtio_dev_rx()\n", dev->device_fh);
+	vq = dev->virtqueue_rx;
+	count = (count > MAX_PKT_BURST) ? MAX_PKT_BURST : count;
+	/* As many data cores may want access to available buffers, they need to be reserved. */
+	do {
+
+		res_base_idx = vq->last_used_idx_res;
+
+		avail_idx = *((volatile uint16_t *)&vq->avail->idx);
+
+		free_entries = (avail_idx - res_base_idx);
+
+		/*check that we have enough buffers*/
+		if (unlikely(count > free_entries))
+			count = free_entries;
+
+		if (count == 0)
+			return 0;
+
+		res_end_idx = res_base_idx + count;
+		/* vq->last_used_idx_res is atomically updated. */
+		success = rte_atomic16_cmpset(&vq->last_used_idx_res, res_base_idx,
+									res_end_idx);
+	} while (unlikely(success == 0));
+	res_cur_idx = res_base_idx;
+	LOG_DEBUG(VHOST_DATA, "(%"PRIu64") Current Index %d| End Index %d\n", dev->device_fh, res_cur_idx, res_end_idx);
+
+	/* Prefetch available ring to retrieve indexes. */
+	rte_prefetch0(&vq->avail->ring[res_cur_idx & (vq->size - 1)]);
+
+	/* Retrieve all of the head indexes first to avoid caching issues. */
+	for (head_idx = 0; head_idx < count; head_idx++)
+		head[head_idx] = vq->avail->ring[(res_cur_idx + head_idx) & (vq->size - 1)];
+
+	/*Prefetch descriptor index. */
+	rte_prefetch0(&vq->desc[head[packet_success]]);
+
+	while (res_cur_idx != res_end_idx) {
+		/* Get descriptor from available ring */
+		desc = &vq->desc[head[packet_success]];
+		/* Prefetch descriptor address. */
+		rte_prefetch0(desc);
+
+		buff = pkts[packet_success];
+
+		/* Convert from gpa to vva (guest physical addr -> vhost virtual addr) */
+		buff_addr = gpa_to_vva(dev, desc->addr);
+		/* Prefetch buffer address. */
+		rte_prefetch0((void*)(uintptr_t)buff_addr);
+
+		{
+			/* Copy virtio_hdr to packet and increment buffer address */
+			buff_hdr_addr = buff_addr;
+			packet_len = rte_pktmbuf_data_len(buff) + vq->vhost_hlen;
+
+			/*
+			 * If the descriptors are chained the header and data are placed in
+			 * separate buffers.
+			 */
+			if (desc->flags & VRING_DESC_F_NEXT) {
+				desc->len = vq->vhost_hlen;
+				desc = &vq->desc[desc->next];
+				/* Buffer address translation. */
+				buff_addr = gpa_to_vva(dev, desc->addr);
+				desc->len = rte_pktmbuf_data_len(buff);
+			} else {
+				buff_addr += vq->vhost_hlen;
+				desc->len = packet_len;
+			}
+		}
+
+		/* Update used ring with desc information */
+		vq->used->ring[res_cur_idx & (vq->size - 1)].id = head[packet_success];
+		vq->used->ring[res_cur_idx & (vq->size - 1)].len = packet_len;
+
+		/* Copy mbuf data to buffer */
+		userdata = rte_pktmbuf_mtod(buff, void *);
+		rte_memcpy((void *)(uintptr_t)buff_addr, userdata, rte_pktmbuf_data_len(buff));
+
+		res_cur_idx++;
+		packet_success++;
+
+		/* mergeable is disabled then a header is required per buffer. */
+		rte_memcpy((void *)(uintptr_t)buff_hdr_addr, (const void *)&virtio_hdr, vq->vhost_hlen);
+		if (res_cur_idx < res_end_idx) {
+			/* Prefetch descriptor index. */
+			rte_prefetch0(&vq->desc[head[packet_success]]);
+		}
+	}
+
+	rte_compiler_barrier();
+
+	/* Wait until it's our turn to add our buffer to the used ring. */
+	while (unlikely(vq->last_used_idx != res_base_idx))
+		rte_pause();
+
+	*(volatile uint16_t *)&vq->used->idx += count;
+
+	vq->last_used_idx = res_end_idx;
+
+	return count;
+}
+
+/*
+ * Compares a packet destination MAC address to a device MAC address.
+ */
+static inline int __attribute__((always_inline))
+ether_addr_cmp(struct ether_addr *ea, struct ether_addr *eb)
+{
+	return ((*(uint64_t *)ea ^ *(uint64_t *)eb) & MAC_ADDR_CMP) == 0;
+}
+
+/*
+ * This function registers mac along with a
+ * vlan tag to a VMDQ.
+ */
+static int
+link_vmdq(struct virtio_net *dev)
+{
+	int ret;
+	struct virtio_net_data_ll *dev_ll;
+
+	dev_ll = ll_root_used;
+
+	while (dev_ll != NULL) {
+		if ((dev != dev_ll->dev) && ether_addr_cmp(&dev->mac_address, &dev_ll->dev->mac_address)) {
+			RTE_LOG(INFO, VHOST_DATA, "(%"PRIu64") WARNING: This device is using an existing MAC address and has not been registered.\n", dev->device_fh);
+			return -1;
+		}
+		dev_ll = dev_ll->next;
+	}
+
+	/* vlan_tag currently uses the device_id. */
+	dev->vlan_tag = vlan_tags[dev->device_fh];
+	dev->vmdq_rx_q = dev->device_fh * (num_queues/num_devices);
+
+	/* Print out VMDQ registration info. */
+	RTE_LOG(INFO, VHOST_DATA, "(%"PRIu64") MAC_ADDRESS %02x:%02x:%02x:%02x:%02x:%02x and VLAN_TAG %d registered\n",
+		dev->device_fh,
+		dev->mac_address.addr_bytes[0], dev->mac_address.addr_bytes[1],
+		dev->mac_address.addr_bytes[2], dev->mac_address.addr_bytes[3],
+		dev->mac_address.addr_bytes[4], dev->mac_address.addr_bytes[5],
+		dev->vlan_tag);
+
+	/* Register the MAC address. */
+	ret = rte_eth_dev_mac_addr_add(ports[0], &dev->mac_address, (uint32_t)dev->device_fh);
+	if (ret) {
+		RTE_LOG(ERR, VHOST_DATA, "(%"PRIu64") Failed to add device MAC address to VMDQ\n",
+										dev->device_fh);
+		return -1;
+	}
+
+	/* Enable stripping of the vlan tag as we handle routing. */
+	rte_eth_dev_set_vlan_strip_on_queue(ports[0], dev->vmdq_rx_q, 1);
+
+	rte_compiler_barrier();
+	/* Set device as ready for RX. */
+	dev->ready = DEVICE_READY;
+
+	return 0;
+}
+
+/*
+ * Removes MAC address and vlan tag from VMDQ. Ensures that nothing is adding buffers to the RX
+ * queue before disabling RX on the device.
+ */
+static inline void
+unlink_vmdq(struct virtio_net *dev)
+{
+	unsigned i = 0;
+	unsigned rx_count;
+	struct rte_mbuf *pkts_burst[MAX_PKT_BURST];
+
+	if (dev->ready == DEVICE_READY) {
+		/*clear MAC and VLAN settings*/
+		rte_eth_dev_mac_addr_remove(ports[0], &dev->mac_address);
+		for (i = 0; i < 6; i++)
+			dev->mac_address.addr_bytes[i] = 0;
+
+		dev->vlan_tag = 0;
+
+		/*Clear out the receive buffers*/
+		rx_count = rte_eth_rx_burst(ports[0],
+					(uint16_t)dev->vmdq_rx_q, pkts_burst, MAX_PKT_BURST);
+
+		while (rx_count) {
+			for (i = 0; i < rx_count; i++)
+				rte_pktmbuf_free(pkts_burst[i]);
+
+			rx_count = rte_eth_rx_burst(ports[0],
+					(uint16_t)dev->vmdq_rx_q, pkts_burst, MAX_PKT_BURST);
+		}
+
+		dev->ready = DEVICE_NOT_READY;
+	}
+}
+
+/*
+ * Check if the packet destination MAC address is for a local device. If so then put
+ * the packet on that devices RX queue. If not then return.
+ */
+static inline unsigned __attribute__((always_inline))
+virtio_tx_local(struct virtio_net *dev, struct rte_mbuf *m)
+{
+	struct virtio_net_data_ll *dev_ll;
+	struct ether_hdr *pkt_hdr;
+	uint64_t ret = 0;
+
+	pkt_hdr = rte_pktmbuf_mtod(m, struct ether_hdr *);
+
+	/*get the used devices list*/
+	dev_ll = ll_root_used;
+
+	while (dev_ll != NULL) {
+		if (likely(dev_ll->dev->ready == DEVICE_READY) && ether_addr_cmp(&(pkt_hdr->d_addr),
+				          &dev_ll->dev->mac_address)) {
+
+			/* Drop the packet if the TX packet is destined for the TX device. */
+			if (dev_ll->dev->device_fh == dev->device_fh) {
+				LOG_DEBUG(VHOST_DATA, "(%"PRIu64") TX: Source and destination MAC addresses are the same. Dropping packet.\n",
+							dev_ll->dev->device_fh);
+				return 0;
+			}
+
+
+			LOG_DEBUG(VHOST_DATA, "(%"PRIu64") TX: MAC address is local\n", dev_ll->dev->device_fh);
+
+			if (dev_ll->dev->remove) {
+				/*drop the packet if the device is marked for removal*/
+				LOG_DEBUG(VHOST_DATA, "(%"PRIu64") Device is marked for removal\n", dev_ll->dev->device_fh);
+			} else {
+				/*send the packet to the local virtio device*/
+				ret = virtio_dev_rx(dev_ll->dev, &m, 1);
+				if (enable_stats) {
+					rte_atomic64_add(&dev_statistics[dev_ll->dev->device_fh].rx_total, 1);
+					rte_atomic64_add(&dev_statistics[dev_ll->dev->device_fh].rx, ret);
+					dev_statistics[dev->device_fh].tx_total++;
+					dev_statistics[dev->device_fh].tx += ret;
+				}
+			}
+
+			return 0;
+		}
+		dev_ll = dev_ll->next;
+	}
+
+	return -1;
+}
+
+/*
+ * This function routes the TX packet to the correct interface. This may be a local device
+ * or the physical port.
+ */
+static inline void __attribute__((always_inline))
+virtio_tx_route(struct virtio_net* dev, struct rte_mbuf *m, struct rte_mempool *mbuf_pool, uint16_t vlan_tag)
+{
+	struct mbuf_table *tx_q;
+	struct vlan_ethhdr *vlan_hdr;
+	struct rte_mbuf **m_table;
+	struct rte_mbuf *mbuf;
+	unsigned len, ret;
+	const uint16_t lcore_id = rte_lcore_id();
+
+	/*check if destination is local VM*/
+	if (enable_vm2vm && (virtio_tx_local(dev, m) == 0)) {
+		return;
+	}
+
+	LOG_DEBUG(VHOST_DATA, "(%"PRIu64") TX: MAC address is external\n", dev->device_fh);
+
+	/*Add packet to the port tx queue*/
+	tx_q = &lcore_tx_queue[lcore_id];
+	len = tx_q->len;
+
+	/* Allocate an mbuf and populate the structure. */
+	mbuf = rte_pktmbuf_alloc(mbuf_pool);
+	if(!mbuf)
+		return;
+
+	mbuf->data_len = m->data_len + VLAN_HLEN;
+	mbuf->pkt_len = mbuf->data_len;
+
+	/* Copy ethernet header to mbuf. */
+	rte_memcpy(rte_pktmbuf_mtod(mbuf, void*),
+			rte_pktmbuf_mtod(m, const void*), ETH_HLEN);
+
+
+	/* Setup vlan header. Bytes need to be re-ordered for network with htons()*/
+	vlan_hdr = rte_pktmbuf_mtod(mbuf, struct vlan_ethhdr *);
+	vlan_hdr->h_vlan_encapsulated_proto = vlan_hdr->h_vlan_proto;
+	vlan_hdr->h_vlan_proto = htons(ETH_P_8021Q);
+	vlan_hdr->h_vlan_TCI = htons(vlan_tag);
+
+	/* Copy the remaining packet contents to the mbuf. */
+	rte_memcpy(rte_pktmbuf_mtod_offset(mbuf, void *, VLAN_ETH_HLEN),
+		rte_pktmbuf_mtod_offset(m, const void *, ETH_HLEN),
+		(m->data_len - ETH_HLEN));
+	tx_q->m_table[len] = mbuf;
+	len++;
+	if (enable_stats) {
+		dev_statistics[dev->device_fh].tx_total++;
+		dev_statistics[dev->device_fh].tx++;
+	}
+
+	if (unlikely(len == MAX_PKT_BURST)) {
+		m_table = (struct rte_mbuf **)tx_q->m_table;
+		ret = rte_eth_tx_burst(ports[0], (uint16_t)tx_q->txq_id, m_table, (uint16_t) len);
+		/* Free any buffers not handled by TX and update the port stats. */
+		if (unlikely(ret < len)) {
+			do {
+				rte_pktmbuf_free(m_table[ret]);
+			} while (++ret < len);
+		}
+
+		len = 0;
+	}
+
+	tx_q->len = len;
+	return;
+}
+
+static inline void __attribute__((always_inline))
+virtio_dev_tx(struct virtio_net* dev, struct rte_mempool *mbuf_pool)
+{
+	struct rte_mbuf m;
+	struct vhost_virtqueue *vq;
+	struct vring_desc *desc;
+	uint64_t buff_addr = 0;
+	uint32_t head[MAX_PKT_BURST];
+	uint32_t used_idx;
+	uint32_t i;
+	uint16_t free_entries, packet_success = 0;
+	uint16_t avail_idx;
+
+	vq = dev->virtqueue_tx;
+	avail_idx = *((volatile uint16_t *)&vq->avail->idx);
+
+	/* If there are no available buffers then return. */
+	if (vq->last_used_idx == avail_idx)
+		return;
+
+	LOG_DEBUG(VHOST_DATA, "(%"PRIu64") virtio_dev_tx()\n", dev->device_fh);
+
+	/* Prefetch available ring to retrieve head indexes. */
+	rte_prefetch0(&vq->avail->ring[vq->last_used_idx & (vq->size - 1)]);
+
+	/*get the number of free entries in the ring*/
+	free_entries = avail_idx - vq->last_used_idx;
+	free_entries = unlikely(free_entries < MAX_PKT_BURST) ? free_entries : MAX_PKT_BURST;
+
+	LOG_DEBUG(VHOST_DATA, "(%"PRIu64") Buffers available %d\n", dev->device_fh, free_entries);
+	/* Retrieve all of the head indexes first to avoid caching issues. */
+	for (i = 0; i < free_entries; i++)
+		head[i] = vq->avail->ring[(vq->last_used_idx + i) & (vq->size - 1)];
+
+	/* Prefetch descriptor index. */
+	rte_prefetch0(&vq->desc[head[packet_success]]);
+
+	while (packet_success < free_entries) {
+		desc = &vq->desc[head[packet_success]];
+		/* Prefetch descriptor address. */
+		rte_prefetch0(desc);
+
+		if (packet_success < (free_entries - 1)) {
+			/* Prefetch descriptor index. */
+			rte_prefetch0(&vq->desc[head[packet_success+1]]);
+		}
+
+		/* Update used index buffer information. */
+		used_idx = vq->last_used_idx & (vq->size - 1);
+		vq->used->ring[used_idx].id = head[packet_success];
+		vq->used->ring[used_idx].len = 0;
+
+		/* Discard first buffer as it is the virtio header */
+		desc = &vq->desc[desc->next];
+
+		/* Buffer address translation. */
+		buff_addr = gpa_to_vva(dev, desc->addr);
+		/* Prefetch buffer address. */
+		rte_prefetch0((void*)(uintptr_t)buff_addr);
+
+		/* Setup dummy mbuf. This is copied to a real mbuf if transmitted out the physical port. */
+		m.data_len = desc->len;
+		m.data_off = 0;
+		m.nb_segs = 1;
+
+		virtio_tx_route(dev, &m, mbuf_pool, 0);
+
+		vq->last_used_idx++;
+		packet_success++;
+	}
+
+	rte_compiler_barrier();
+	vq->used->idx += packet_success;
+	/* Kick guest if required. */
+}
+
+/*
+ * This function is called by each data core. It handles all RX/TX registered with the
+ * core. For TX the specific lcore linked list is used. For RX, MAC addresses are compared
+ * with all devices in the main linked list.
+ */
+static int
+switch_worker(__attribute__((unused)) void *arg)
+{
+	struct rte_mempool *mbuf_pool = arg;
+	struct virtio_net *dev = NULL;
+	struct rte_mbuf *pkts_burst[MAX_PKT_BURST];
+	struct virtio_net_data_ll *dev_ll;
+	struct mbuf_table *tx_q;
+	volatile struct lcore_ll_info *lcore_ll;
+	const uint64_t drain_tsc = (rte_get_tsc_hz() + US_PER_S - 1) / US_PER_S * BURST_TX_DRAIN_US;
+	uint64_t prev_tsc, diff_tsc, cur_tsc, ret_count = 0;
+	unsigned ret, i;
+	const uint16_t lcore_id = rte_lcore_id();
+	const uint16_t num_cores = (uint16_t)rte_lcore_count();
+	uint16_t rx_count = 0;
+
+	RTE_LOG(INFO, VHOST_DATA, "Procesing on Core %u started \n", lcore_id);
+	lcore_ll = lcore_info[lcore_id].lcore_ll;
+	prev_tsc = 0;
+
+	tx_q = &lcore_tx_queue[lcore_id];
+	for (i = 0; i < num_cores; i ++) {
+		if (lcore_ids[i] == lcore_id) {
+			tx_q->txq_id = i;
+			break;
+		}
+	}
+
+	while(1) {
+		cur_tsc = rte_rdtsc();
+		/*
+		 * TX burst queue drain
+		 */
+		diff_tsc = cur_tsc - prev_tsc;
+		if (unlikely(diff_tsc > drain_tsc)) {
+
+			if (tx_q->len) {
+				LOG_DEBUG(VHOST_DATA, "TX queue drained after timeout with burst size %u \n", tx_q->len);
+
+				/*Tx any packets in the queue*/
+				ret = rte_eth_tx_burst(ports[0], (uint16_t)tx_q->txq_id,
+									   (struct rte_mbuf **)tx_q->m_table,
+									   (uint16_t)tx_q->len);
+				if (unlikely(ret < tx_q->len)) {
+					do {
+						rte_pktmbuf_free(tx_q->m_table[ret]);
+					} while (++ret < tx_q->len);
+				}
+
+				tx_q->len = 0;
+			}
+
+			prev_tsc = cur_tsc;
+
+		}
+
+		/*
+		 * Inform the configuration core that we have exited the linked list and that no devices are
+		 * in use if requested.
+		 */
+		if (lcore_ll->dev_removal_flag == REQUEST_DEV_REMOVAL)
+			lcore_ll->dev_removal_flag = ACK_DEV_REMOVAL;
+
+		/*
+		 * Process devices
+	 	 */
+		dev_ll = lcore_ll->ll_root_used;
+
+		while (dev_ll != NULL) {
+			/*get virtio device ID*/
+			dev = dev_ll->dev;
+
+			if (unlikely(dev->remove)) {
+				dev_ll = dev_ll->next;
+				unlink_vmdq(dev);
+				dev->ready = DEVICE_SAFE_REMOVE;
+				continue;
+			}
+			if (likely(dev->ready == DEVICE_READY)) {
+				/*Handle guest RX*/
+				rx_count = rte_eth_rx_burst(ports[0],
+					(uint16_t)dev->vmdq_rx_q, pkts_burst, MAX_PKT_BURST);
+
+				if (rx_count) {
+					ret_count = virtio_dev_rx(dev, pkts_burst, rx_count);
+					if (enable_stats) {
+						rte_atomic64_add(&dev_statistics[dev_ll->dev->device_fh].rx_total, rx_count);
+						rte_atomic64_add(&dev_statistics[dev_ll->dev->device_fh].rx, ret_count);
+					}
+					while (likely(rx_count)) {
+						rx_count--;
+						rte_pktmbuf_free_seg(pkts_burst[rx_count]);
+					}
+
+				}
+			}
+
+			if (likely(!dev->remove))
+				/*Handle guest TX*/
+				virtio_dev_tx(dev, mbuf_pool);
+
+			/*move to the next device in the list*/
+			dev_ll = dev_ll->next;
+		}
+	}
+
+	return 0;
+}
+
+/*
+ * Add an entry to a used linked list. A free entry must first be found in the free linked list
+ * using get_data_ll_free_entry();
+ */
+static void
+add_data_ll_entry(struct virtio_net_data_ll **ll_root_addr, struct virtio_net_data_ll *ll_dev)
+{
+	struct virtio_net_data_ll *ll = *ll_root_addr;
+
+	/* Set next as NULL and use a compiler barrier to avoid reordering. */
+	ll_dev->next = NULL;
+	rte_compiler_barrier();
+
+	/* If ll == NULL then this is the first device. */
+	if (ll) {
+		/* Increment to the tail of the linked list. */
+		while ((ll->next != NULL) )
+			ll = ll->next;
+
+		ll->next = ll_dev;
+	} else {
+		*ll_root_addr = ll_dev;
+	}
+}
+
+/*
+ * Remove an entry from a used linked list. The entry must then be added to the free linked list
+ * using put_data_ll_free_entry().
+ */
+static void
+rm_data_ll_entry(struct virtio_net_data_ll **ll_root_addr, struct virtio_net_data_ll *ll_dev, struct virtio_net_data_ll *ll_dev_last)
+{
+	struct virtio_net_data_ll *ll = *ll_root_addr;
+
+	if (ll_dev == ll)
+		*ll_root_addr = ll_dev->next;
+	else
+		ll_dev_last->next = ll_dev->next;
+}
+
+/*
+ * Find and return an entry from the free linked list.
+ */
+static struct virtio_net_data_ll *
+get_data_ll_free_entry(struct virtio_net_data_ll **ll_root_addr)
+{
+	struct virtio_net_data_ll *ll_free = *ll_root_addr;
+	struct virtio_net_data_ll *ll_dev;
+
+	if (ll_free == NULL)
+		return NULL;
+
+	ll_dev = ll_free;
+	*ll_root_addr = ll_free->next;
+
+	return ll_dev;
+}
+
+/*
+ * Place an entry back on to the free linked list.
+ */
+static void
+put_data_ll_free_entry(struct virtio_net_data_ll **ll_root_addr, struct virtio_net_data_ll *ll_dev)
+{
+	struct virtio_net_data_ll *ll_free = *ll_root_addr;
+
+	ll_dev->next = ll_free;
+	*ll_root_addr = ll_dev;
+}
+
+/*
+ * Creates a linked list of a given size.
+ */
+static struct virtio_net_data_ll *
+alloc_data_ll(uint32_t size)
+{
+	struct virtio_net_data_ll *ll_new;
+	uint32_t i;
+
+	/* Malloc and then chain the linked list. */
+	ll_new = malloc(size * sizeof(struct virtio_net_data_ll));
+	if (ll_new == NULL) {
+		RTE_LOG(ERR, VHOST_CONFIG, "Failed to allocate memory for ll_new.\n");
+		return NULL;
+	}
+
+	for (i = 0; i < size - 1; i++) {
+		ll_new[i].dev = NULL;
+		ll_new[i].next = &ll_new[i+1];
+	}
+	ll_new[i].next = NULL;
+
+	return ll_new;
+}
+
+/*
+ * Create the main linked list along with each individual cores linked list. A used and a free list
+ * are created to manage entries.
+ */
+static int
+init_data_ll (void)
+{
+	int lcore;
+
+	RTE_LCORE_FOREACH_SLAVE(lcore) {
+		lcore_info[lcore].lcore_ll = malloc(sizeof(struct lcore_ll_info));
+		if (lcore_info[lcore].lcore_ll == NULL) {
+			RTE_LOG(ERR, VHOST_CONFIG, "Failed to allocate memory for lcore_ll.\n");
+			return -1;
+		}
+
+		lcore_info[lcore].lcore_ll->device_num = 0;
+		lcore_info[lcore].lcore_ll->dev_removal_flag = ACK_DEV_REMOVAL;
+		lcore_info[lcore].lcore_ll->ll_root_used = NULL;
+		if (num_devices % num_switching_cores)
+			lcore_info[lcore].lcore_ll->ll_root_free = alloc_data_ll((num_devices / num_switching_cores) + 1);
+		else
+			lcore_info[lcore].lcore_ll->ll_root_free = alloc_data_ll(num_devices / num_switching_cores);
+	}
+
+	/* Allocate devices up to a maximum of MAX_DEVICES. */
+	ll_root_free = alloc_data_ll(MIN((num_devices), MAX_DEVICES));
+
+	return 0;
+}
+/*
+ * Remove a device from the specific data core linked list and from the main linked list. The
+ * rx/tx thread must be set the flag to indicate that it is safe to remove the device.
+ * used.
+ */
+static void
+destroy_device (volatile struct virtio_net *dev)
+{
+	struct virtio_net_data_ll *ll_lcore_dev_cur;
+	struct virtio_net_data_ll *ll_main_dev_cur;
+	struct virtio_net_data_ll *ll_lcore_dev_last = NULL;
+	struct virtio_net_data_ll *ll_main_dev_last = NULL;
+	int lcore;
+
+	dev->flags &= ~VIRTIO_DEV_RUNNING;
+
+	/*set the remove flag. */
+	dev->remove = 1;
+
+	while(dev->ready != DEVICE_SAFE_REMOVE) {
+		rte_pause();
+	}
+
+	/* Search for entry to be removed from lcore ll */
+	ll_lcore_dev_cur = lcore_info[dev->coreid].lcore_ll->ll_root_used;
+	while (ll_lcore_dev_cur != NULL) {
+		if (ll_lcore_dev_cur->dev == dev) {
+			break;
+		} else {
+			ll_lcore_dev_last = ll_lcore_dev_cur;
+			ll_lcore_dev_cur = ll_lcore_dev_cur->next;
+		}
+	}
+
+	/* Search for entry to be removed from main ll */
+	ll_main_dev_cur = ll_root_used;
+	ll_main_dev_last = NULL;
+	while (ll_main_dev_cur != NULL) {
+		if (ll_main_dev_cur->dev == dev) {
+			break;
+		} else {
+			ll_main_dev_last = ll_main_dev_cur;
+			ll_main_dev_cur = ll_main_dev_cur->next;
+		}
+	}
+
+	if (ll_lcore_dev_cur == NULL || ll_main_dev_cur == NULL) {
+		RTE_LOG(ERR, XENHOST, "%s: could find device in per_cpu list or main_list\n", __func__);
+		return;
+	}
+
+	/* Remove entries from the lcore and main ll. */
+	rm_data_ll_entry(&lcore_info[ll_lcore_dev_cur->dev->coreid].lcore_ll->ll_root_used, ll_lcore_dev_cur, ll_lcore_dev_last);
+	rm_data_ll_entry(&ll_root_used, ll_main_dev_cur, ll_main_dev_last);
+
+	/* Set the dev_removal_flag on each lcore. */
+	RTE_LCORE_FOREACH_SLAVE(lcore) {
+		lcore_info[lcore].lcore_ll->dev_removal_flag = REQUEST_DEV_REMOVAL;
+	}
+
+	/*
+	 * Once each core has set the dev_removal_flag to ACK_DEV_REMOVAL we can be sure that
+	 * they can no longer access the device removed from the linked lists and that the devices
+	 * are no longer in use.
+	 */
+	RTE_LCORE_FOREACH_SLAVE(lcore) {
+		while (lcore_info[lcore].lcore_ll->dev_removal_flag != ACK_DEV_REMOVAL) {
+			rte_pause();
+		}
+	}
+
+	/* Add the entries back to the lcore and main free ll.*/
+	put_data_ll_free_entry(&lcore_info[ll_lcore_dev_cur->dev->coreid].lcore_ll->ll_root_free, ll_lcore_dev_cur);
+	put_data_ll_free_entry(&ll_root_free, ll_main_dev_cur);
+
+	/* Decrement number of device on the lcore. */
+	lcore_info[ll_lcore_dev_cur->dev->coreid].lcore_ll->device_num--;
+
+	RTE_LOG(INFO, VHOST_DATA, "  #####(%"PRIu64") Device has been removed from data core\n", dev->device_fh);
+}
+
+/*
+ * A new device is added to a data core. First the device is added to the main linked list
+ * and the allocated to a specific data core.
+ */
+static int
+new_device (struct virtio_net *dev)
+{
+	struct virtio_net_data_ll *ll_dev;
+	int lcore, core_add = 0;
+	uint32_t device_num_min = num_devices;
+
+	/* Add device to main ll */
+	ll_dev = get_data_ll_free_entry(&ll_root_free);
+	if (ll_dev == NULL) {
+		RTE_LOG(INFO, VHOST_DATA, "(%"PRIu64") No free entry found in linked list. Device limit "
+			"of %d devices per core has been reached\n",
+			dev->device_fh, num_devices);
+		return -1;
+	}
+	ll_dev->dev = dev;
+	add_data_ll_entry(&ll_root_used, ll_dev);
+
+	/*reset ready flag*/
+	dev->ready = DEVICE_NOT_READY;
+	dev->remove = 0;
+
+	/* Find a suitable lcore to add the device. */
+	RTE_LCORE_FOREACH_SLAVE(lcore) {
+		if (lcore_info[lcore].lcore_ll->device_num < device_num_min) {
+			device_num_min = lcore_info[lcore].lcore_ll->device_num;
+			core_add = lcore;
+		}
+	}
+	/* Add device to lcore ll */
+	ll_dev->dev->coreid = core_add;
+	ll_dev = get_data_ll_free_entry(&lcore_info[ll_dev->dev->coreid].lcore_ll->ll_root_free);
+	if (ll_dev == NULL) {
+		RTE_LOG(INFO, VHOST_DATA, "(%"PRIu64") Failed to add device to data core\n", dev->device_fh);
+		destroy_device(dev);
+		return -1;
+	}
+	ll_dev->dev = dev;
+	add_data_ll_entry(&lcore_info[ll_dev->dev->coreid].lcore_ll->ll_root_used, ll_dev);
+
+	/* Initialize device stats */
+	memset(&dev_statistics[dev->device_fh], 0, sizeof(struct device_statistics));
+
+	lcore_info[ll_dev->dev->coreid].lcore_ll->device_num++;
+	dev->flags |= VIRTIO_DEV_RUNNING;
+
+	RTE_LOG(INFO, VHOST_DATA, "(%"PRIu64") Device has been added to data core %d\n", dev->device_fh, dev->coreid);
+
+	link_vmdq(dev);
+
+	return 0;
+}
+
+/*
+ * These callback allow devices to be added to the data core when configuration
+ * has been fully complete.
+ */
+static const struct virtio_net_device_ops virtio_net_device_ops =
+{
+	.new_device =  new_device,
+	.destroy_device = destroy_device,
+};
+
+/*
+ * This is a thread will wake up after a period to print stats if the user has
+ * enabled them.
+ */
+static void
+print_stats(void)
+{
+	struct virtio_net_data_ll *dev_ll;
+	uint64_t tx_dropped, rx_dropped;
+	uint64_t tx, tx_total, rx, rx_total;
+	uint32_t device_fh;
+	const char clr[] = { 27, '[', '2', 'J', '\0' };
+	const char top_left[] = { 27, '[', '1', ';', '1', 'H','\0' };
+
+	while(1) {
+		sleep(enable_stats);
+
+		/* Clear screen and move to top left */
+		printf("%s%s", clr, top_left);
+
+		printf("\nDevice statistics ====================================");
+
+		dev_ll = ll_root_used;
+		while (dev_ll != NULL) {
+			device_fh = (uint32_t)dev_ll->dev->device_fh;
+			tx_total = dev_statistics[device_fh].tx_total;
+			tx = dev_statistics[device_fh].tx;
+			tx_dropped = tx_total - tx;
+			rx_total = rte_atomic64_read(&dev_statistics[device_fh].rx_total);
+			rx = rte_atomic64_read(&dev_statistics[device_fh].rx);
+			rx_dropped = rx_total - rx;
+
+			printf("\nStatistics for device %"PRIu32" ------------------------------"
+					"\nTX total: 		%"PRIu64""
+					"\nTX dropped: 		%"PRIu64""
+					"\nTX successful: 		%"PRIu64""
+					"\nRX total: 		%"PRIu64""
+					"\nRX dropped: 		%"PRIu64""
+					"\nRX successful: 		%"PRIu64"",
+					device_fh,
+					tx_total,
+					tx_dropped,
+					tx,
+					rx_total,
+					rx_dropped,
+					rx);
+
+			dev_ll = dev_ll->next;
+		}
+		printf("\n======================================================\n");
+	}
+}
+
+
+int init_virtio_net(struct virtio_net_device_ops const * const ops);
+
+/*
+ * Main function, does initialisation and calls the per-lcore functions. The CUSE
+ * device is also registered here to handle the IOCTLs.
+ */
+int
+main(int argc, char *argv[])
+{
+	struct rte_mempool *mbuf_pool;
+	unsigned lcore_id, core_id = 0;
+	unsigned nb_ports, valid_num_ports;
+	int ret;
+	uint8_t portid;
+	static pthread_t tid;
+	char thread_name[RTE_MAX_THREAD_NAME_LEN];
+
+	/* init EAL */
+	ret = rte_eal_init(argc, argv);
+	if (ret < 0)
+		rte_exit(EXIT_FAILURE, "Error with EAL initialization\n");
+	argc -= ret;
+	argv += ret;
+
+	/* parse app arguments */
+	ret = us_vhost_parse_args(argc, argv);
+	if (ret < 0)
+		rte_exit(EXIT_FAILURE, "Invalid argument\n");
+
+	for (lcore_id = 0; lcore_id < RTE_MAX_LCORE; lcore_id ++)
+		if (rte_lcore_is_enabled(lcore_id))
+			lcore_ids[core_id ++] = lcore_id;
+
+	if (rte_lcore_count() > RTE_MAX_LCORE)
+		rte_exit(EXIT_FAILURE,"Not enough cores\n");
+
+	/*set the number of swithcing cores available*/
+	num_switching_cores = rte_lcore_count()-1;
+
+	/* Get the number of physical ports. */
+	nb_ports = rte_eth_dev_count();
+	if (nb_ports > RTE_MAX_ETHPORTS)
+		nb_ports = RTE_MAX_ETHPORTS;
+
+	/*
+	 * Update the global var NUM_PORTS and global array PORTS
+	 * and get value of var VALID_NUM_PORTS according to system ports number
+	 */
+	valid_num_ports = check_ports_num(nb_ports);
+
+	if ((valid_num_ports ==  0) || (valid_num_ports > MAX_SUP_PORTS)) {
+		RTE_LOG(INFO, VHOST_PORT, "Current enabled port number is %u,"
+			"but only %u port can be enabled\n",num_ports, MAX_SUP_PORTS);
+		return -1;
+	}
+
+	/* Create the mbuf pool. */
+	mbuf_pool = rte_pktmbuf_pool_create("MBUF_POOL",
+		NUM_MBUFS_PER_PORT * valid_num_ports, MBUF_CACHE_SIZE, 0,
+		RTE_MBUF_DEFAULT_BUF_SIZE, rte_socket_id());
+	if (mbuf_pool == NULL)
+		rte_exit(EXIT_FAILURE, "Cannot create mbuf pool\n");
+
+	/* Set log level. */
+	rte_set_log_level(LOG_LEVEL);
+
+	/* initialize all ports */
+	for (portid = 0; portid < nb_ports; portid++) {
+		/* skip ports that are not enabled */
+		if ((enabled_port_mask & (1 << portid)) == 0) {
+			RTE_LOG(INFO, VHOST_PORT, "Skipping disabled port %d\n", portid);
+			continue;
+		}
+		if (port_init(portid, mbuf_pool) != 0)
+			rte_exit(EXIT_FAILURE, "Cannot initialize network ports\n");
+	}
+
+	/* Initialise all linked lists. */
+	if (init_data_ll() == -1)
+		rte_exit(EXIT_FAILURE, "Failed to initialize linked list\n");
+
+	/* Initialize device stats */
+	memset(&dev_statistics, 0, sizeof(dev_statistics));
+
+	/* Enable stats if the user option is set. */
+	if (enable_stats) {
+		ret = pthread_create(&tid, NULL, (void *)print_stats, NULL);
+		if (ret != 0)
+			rte_exit(EXIT_FAILURE,
+				"Cannot create print-stats thread\n");
+
+		/* Set thread_name for aid in debugging. */
+		snprintf(thread_name, RTE_MAX_THREAD_NAME_LEN, "print-xen-stats");
+		ret = rte_thread_setname(tid, thread_name);
+		if (ret != 0)
+			RTE_LOG(ERR, VHOST_CONFIG,
+				"Cannot set print-stats name\n");
+	}
+
+	/* Launch all data cores. */
+	RTE_LCORE_FOREACH_SLAVE(lcore_id) {
+		rte_eal_remote_launch(switch_worker, mbuf_pool, lcore_id);
+	}
+
+	init_virtio_xen(&virtio_net_device_ops);
+
+	virtio_monitor_loop();
+	return 0;
+}
diff --git a/examples/vhost_xen/main.h b/examples/vhost_xen/main.h
new file mode 100644
index 00000000..481572e6
--- /dev/null
+++ b/examples/vhost_xen/main.h
@@ -0,0 +1,77 @@
+/*-
+ *   BSD LICENSE
+ *
+ *   Copyright(c) 2010-2014 Intel Corporation. All rights reserved.
+ *   All rights reserved.
+ *
+ *   Redistribution and use in source and binary forms, with or without
+ *   modification, are permitted provided that the following conditions
+ *   are met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ *       notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above copyright
+ *       notice, this list of conditions and the following disclaimer in
+ *       the documentation and/or other materials provided with the
+ *       distribution.
+ *     * Neither the name of Intel Corporation nor the names of its
+ *       contributors may be used to endorse or promote products derived
+ *       from this software without specific prior written permission.
+ *
+ *   THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ *   "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ *   LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ *   A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ *   OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ *   SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ *   LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ *   DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ *   THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ *   (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ *   OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef _MAIN_H_
+#define _MAIN_H_
+
+//#define DEBUG
+
+#ifdef DEBUG
+#define LOG_LEVEL RTE_LOG_DEBUG
+#define LOG_DEBUG(log_type, fmt, args...) \
+	RTE_LOG(DEBUG, log_type, fmt, ##args)
+#else
+#define LOG_LEVEL RTE_LOG_INFO
+#define LOG_DEBUG(log_type, fmt, args...) do{} while(0)
+#endif
+
+/* Macros for printing using RTE_LOG */
+#define RTE_LOGTYPE_VHOST_CONFIG RTE_LOGTYPE_USER1
+#define RTE_LOGTYPE_VHOST_DATA   RTE_LOGTYPE_USER2
+#define RTE_LOGTYPE_VHOST_PORT   RTE_LOGTYPE_USER3
+
+/*
+ * Device linked list structure for data path.
+ */
+struct virtio_net_data_ll
+{
+	struct virtio_net          *dev;   /* Pointer to device created by configuration core. */
+	struct virtio_net_data_ll  *next;  /* Pointer to next device in linked list. */
+};
+
+/*
+ * Structure containing data core specific information.
+ */
+struct lcore_ll_info
+{
+	struct virtio_net_data_ll    *ll_root_free; 	/* Pointer to head in free linked list. */
+	struct virtio_net_data_ll    *ll_root_used;	    /* Pointer to head of used linked list. */
+	uint32_t                      device_num;       /* Number of devices on lcore. */
+	volatile  uint8_t             dev_removal_flag; /* Flag to synchronize device removal. */
+};
+
+struct lcore_info
+{
+	struct lcore_ll_info	*lcore_ll;	/* Pointer to data core specific lcore_ll_info struct */
+};
+#endif /* _MAIN_H_ */
diff --git a/examples/vhost_xen/vhost_monitor.c b/examples/vhost_xen/vhost_monitor.c
new file mode 100644
index 00000000..fb9606bf
--- /dev/null
+++ b/examples/vhost_xen/vhost_monitor.c
@@ -0,0 +1,595 @@
+/*-
+ *   BSD LICENSE
+ *
+ *   Copyright(c) 2010-2014 Intel Corporation. All rights reserved.
+ *   All rights reserved.
+ *
+ *   Redistribution and use in source and binary forms, with or without
+ *   modification, are permitted provided that the following conditions
+ *   are met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ *       notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above copyright
+ *       notice, this list of conditions and the following disclaimer in
+ *       the documentation and/or other materials provided with the
+ *       distribution.
+ *     * Neither the name of Intel Corporation nor the names of its
+ *       contributors may be used to endorse or promote products derived
+ *       from this software without specific prior written permission.
+ *
+ *   THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ *   "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ *   LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ *   A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ *   OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ *   SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ *   LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ *   DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ *   THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ *   (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ *   OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <stdlib.h>
+#include <stdio.h>
+#include <dirent.h>
+#include <unistd.h>
+#include <sys/eventfd.h>
+#include <sys/ioctl.h>
+#include <sys/mman.h>
+#include <xen/xen-compat.h>
+#if __XEN_LATEST_INTERFACE_VERSION__ < 0x00040200
+#include <xs.h>
+#else
+#include <xenstore.h>
+#endif
+#include <linux/virtio_ring.h>
+#include <linux/virtio_pci.h>
+#include <linux/virtio_net.h>
+
+#include <rte_ethdev.h>
+#include <rte_log.h>
+#include <rte_malloc.h>
+#include <rte_string_fns.h>
+
+#include "virtio-net.h"
+#include "xen_vhost.h"
+
+struct virtio_watch {
+	struct xs_handle *xs;
+	int watch_fd;
+};
+
+
+/* device ops to add/remove device to/from data core. */
+static struct virtio_net_device_ops const *notify_ops;
+
+/* root address of the linked list in the configuration core. */
+static struct virtio_net_config_ll *ll_root = NULL;
+
+/* root address of VM. */
+static struct xen_guestlist guest_root;
+
+static struct virtio_watch watch;
+
+static void
+vq_vring_init(struct vhost_virtqueue *vq, unsigned int num, uint8_t *p,
+	unsigned long align)
+{
+	vq->size = num;
+	vq->desc = (struct vring_desc *) p;
+	vq->avail = (struct vring_avail *) (p +
+		num * sizeof(struct vring_desc));
+	vq->used = (void *)
+		RTE_ALIGN_CEIL( (uintptr_t)(&vq->avail->ring[num]), align);
+
+}
+
+static int
+init_watch(void)
+{
+	struct xs_handle *xs;
+	int ret;
+	int fd;
+
+	/* get a connection to the daemon */
+	xs = xs_daemon_open();
+	if (xs == NULL) {
+		RTE_LOG(ERR, XENHOST, "xs_daemon_open failed\n");
+		return -1;
+	}
+
+	ret = xs_watch(xs, "/local/domain", "mytoken");
+	if (ret == 0) {
+		RTE_LOG(ERR, XENHOST, "%s: xs_watch failed\n", __func__);
+		xs_daemon_close(xs);
+		return -1;
+	}
+
+	/* We are notified of read availability on the watch via the file descriptor. */
+	fd = xs_fileno(xs);
+	watch.xs = xs;
+	watch.watch_fd = fd;
+
+	TAILQ_INIT(&guest_root);
+	return 0;
+}
+
+static struct xen_guest *
+get_xen_guest(int dom_id)
+{
+	struct xen_guest *guest = NULL;
+
+	TAILQ_FOREACH(guest, &guest_root, next) {
+		if(guest->dom_id == dom_id)
+			return guest;
+	}
+
+	return NULL;
+}
+
+
+static struct xen_guest *
+add_xen_guest(int32_t dom_id)
+{
+	struct xen_guest *guest = NULL;
+
+	if ((guest = get_xen_guest(dom_id)) != NULL)
+		return guest;
+
+	guest = calloc(1, sizeof(struct xen_guest));
+	if (guest) {
+		RTE_LOG(ERR, XENHOST, "  %s: return newly created guest with %d rings\n", __func__, guest->vring_num);
+		TAILQ_INSERT_TAIL(&guest_root, guest, next);
+		guest->dom_id = dom_id;
+	}
+
+	return guest;
+}
+
+static void
+cleanup_device(struct virtio_net_config_ll *ll_dev)
+{
+	if (ll_dev == NULL)
+		return;
+	if (ll_dev->dev.virtqueue_rx) {
+		rte_free(ll_dev->dev.virtqueue_rx);
+		ll_dev->dev.virtqueue_rx = NULL;
+	}
+	if (ll_dev->dev.virtqueue_tx) {
+		rte_free(ll_dev->dev.virtqueue_tx);
+		ll_dev->dev.virtqueue_tx = NULL;
+	}
+	free(ll_dev);
+}
+
+/*
+ * Add entry containing a device to the device configuration linked list.
+ */
+static void
+add_config_ll_entry(struct virtio_net_config_ll *new_ll_dev)
+{
+	struct virtio_net_config_ll *ll_dev = ll_root;
+
+	/* If ll_dev == NULL then this is the first device so go to else */
+	if (ll_dev) {
+		/* If the 1st device_id != 0 then we insert our device here. */
+		if (ll_dev->dev.device_fh != 0)	{
+			new_ll_dev->dev.device_fh = 0;
+			new_ll_dev->next = ll_dev;
+			ll_root = new_ll_dev;
+		} else {
+			/* increment through the ll until we find un unused device_id,
+			 * insert the device at that entry
+			 */
+			while ((ll_dev->next != NULL) && (ll_dev->dev.device_fh == (ll_dev->next->dev.device_fh - 1)))
+				ll_dev = ll_dev->next;
+
+			new_ll_dev->dev.device_fh = ll_dev->dev.device_fh + 1;
+			new_ll_dev->next = ll_dev->next;
+			ll_dev->next = new_ll_dev;
+		}
+	} else {
+		ll_root = new_ll_dev;
+		ll_root->dev.device_fh = 0;
+	}
+}
+
+
+/*
+ * Remove an entry from the device configuration linked list.
+ */
+static struct virtio_net_config_ll *
+rm_config_ll_entry(struct virtio_net_config_ll *ll_dev, struct virtio_net_config_ll *ll_dev_last)
+{
+	/* First remove the device and then clean it up. */
+	if (ll_dev == ll_root) {
+		ll_root = ll_dev->next;
+		cleanup_device(ll_dev);
+		return ll_root;
+	} else {
+		ll_dev_last->next = ll_dev->next;
+		cleanup_device(ll_dev);
+		return ll_dev_last->next;
+	}
+}
+
+/*
+ * Retrieves an entry from the devices configuration linked list.
+ */
+static struct virtio_net_config_ll *
+get_config_ll_entry(unsigned int virtio_idx, unsigned int dom_id)
+{
+	struct virtio_net_config_ll *ll_dev = ll_root;
+
+	/* Loop through linked list until the dom_id is found. */
+	while (ll_dev != NULL) {
+		if (ll_dev->dev.dom_id == dom_id && ll_dev->dev.virtio_idx == virtio_idx)
+			return ll_dev;
+		ll_dev = ll_dev->next;
+	}
+
+	return NULL;
+}
+
+/*
+ * Initialise all variables in device structure.
+ */
+static void
+init_dev(struct virtio_net *dev)
+{
+	RTE_SET_USED(dev);
+}
+
+
+static struct
+virtio_net_config_ll *new_device(unsigned int virtio_idx, struct xen_guest *guest)
+{
+	struct virtio_net_config_ll *new_ll_dev;
+	struct vhost_virtqueue *virtqueue_rx, *virtqueue_tx;
+	size_t size, vq_ring_size, vq_size = VQ_DESC_NUM;
+	void *vq_ring_virt_mem;
+	uint64_t gpa;
+	uint32_t i;
+
+	/* Setup device and virtqueues. */
+	new_ll_dev   = calloc(1, sizeof(struct virtio_net_config_ll));
+	virtqueue_rx = rte_zmalloc(NULL, sizeof(struct vhost_virtqueue), RTE_CACHE_LINE_SIZE);
+	virtqueue_tx = rte_zmalloc(NULL, sizeof(struct vhost_virtqueue), RTE_CACHE_LINE_SIZE);
+	if (new_ll_dev == NULL || virtqueue_rx == NULL || virtqueue_tx == NULL)
+		goto err;
+
+	new_ll_dev->dev.virtqueue_rx = virtqueue_rx;
+	new_ll_dev->dev.virtqueue_tx = virtqueue_tx;
+	new_ll_dev->dev.dom_id       = guest->dom_id;
+	new_ll_dev->dev.virtio_idx   = virtio_idx;
+	/* Initialise device and virtqueues. */
+	init_dev(&new_ll_dev->dev);
+
+	size = vring_size(vq_size, VIRTIO_PCI_VRING_ALIGN);
+	vq_ring_size = RTE_ALIGN_CEIL(size, VIRTIO_PCI_VRING_ALIGN);
+	(void)vq_ring_size;
+
+	vq_ring_virt_mem = guest->vring[virtio_idx].rxvring_addr;
+	vq_vring_init(virtqueue_rx, vq_size, vq_ring_virt_mem, VIRTIO_PCI_VRING_ALIGN);
+	virtqueue_rx->size = vq_size;
+	virtqueue_rx->vhost_hlen = sizeof(struct virtio_net_hdr);
+
+	vq_ring_virt_mem = guest->vring[virtio_idx].txvring_addr;
+	vq_vring_init(virtqueue_tx, vq_size, vq_ring_virt_mem, VIRTIO_PCI_VRING_ALIGN);
+	virtqueue_tx->size = vq_size;
+	memcpy(&new_ll_dev->dev.mac_address, &guest->vring[virtio_idx].addr, sizeof(struct ether_addr));
+
+	/* virtio_memory has to be one per domid */
+	new_ll_dev->dev.mem = malloc(sizeof(struct virtio_memory) + sizeof(struct virtio_memory_regions) * MAX_XENVIRT_MEMPOOL);
+	new_ll_dev->dev.mem->nregions = guest->pool_num;
+	for (i = 0; i < guest->pool_num; i++) {
+		gpa = new_ll_dev->dev.mem->regions[i].guest_phys_address =
+				(uint64_t)((uintptr_t)guest->mempool[i].gva);
+		new_ll_dev->dev.mem->regions[i].guest_phys_address_end =
+				gpa + guest->mempool[i].mempfn_num * getpagesize();
+		new_ll_dev->dev.mem->regions[i].address_offset =
+				(uint64_t)((uintptr_t)guest->mempool[i].hva -
+					(uintptr_t)gpa);
+	}
+
+	new_ll_dev->next = NULL;
+
+	/* Add entry to device configuration linked list. */
+	add_config_ll_entry(new_ll_dev);
+	return new_ll_dev;
+err:
+	free(new_ll_dev);
+	rte_free(virtqueue_rx);
+	rte_free(virtqueue_tx);
+
+	return NULL;
+}
+
+static void
+destroy_guest(struct xen_guest *guest)
+{
+	uint32_t i;
+
+	for (i = 0; i < guest->vring_num; i++)
+		cleanup_vring(&guest->vring[i]);
+	/* clean mempool */
+	for (i = 0; i < guest->pool_num; i++)
+		cleanup_mempool(&guest->mempool[i]);
+	free(guest);
+
+	return;
+}
+
+/*
+ * This function will cleanup the device and remove it from device configuration linked list.
+ */
+static void
+destroy_device(unsigned int virtio_idx, unsigned int dom_id)
+{
+	struct virtio_net_config_ll *ll_dev_cur_ctx, *ll_dev_last = NULL;
+	struct virtio_net_config_ll *ll_dev_cur = ll_root;
+
+	/* clean virtio device */
+	struct xen_guest *guest = NULL;
+	guest = get_xen_guest(dom_id);
+	if (guest == NULL)
+		return;
+
+	/* Find the linked list entry for the device to be removed. */
+	ll_dev_cur_ctx = get_config_ll_entry(virtio_idx, dom_id);
+	while (ll_dev_cur != NULL) {
+		/* If the device is found or a device that doesn't exist is found then it is removed. */
+		if  (ll_dev_cur == ll_dev_cur_ctx) {
+			if ((ll_dev_cur->dev.flags & VIRTIO_DEV_RUNNING))
+				notify_ops->destroy_device(&(ll_dev_cur->dev));
+			ll_dev_cur = rm_config_ll_entry(ll_dev_cur, ll_dev_last);
+		} else {
+			ll_dev_last = ll_dev_cur;
+			ll_dev_cur = ll_dev_cur->next;
+		}
+	}
+	RTE_LOG(INFO, XENHOST, "  %s guest:%p vring:%p rxvring:%p txvring:%p flag:%p\n",
+		__func__, guest, &guest->vring[virtio_idx], guest->vring[virtio_idx].rxvring_addr, guest->vring[virtio_idx].txvring_addr, guest->vring[virtio_idx].flag);
+	cleanup_vring(&guest->vring[virtio_idx]);
+	guest->vring[virtio_idx].removed = 1;
+	guest->vring_num -= 1;
+}
+
+
+
+
+static void
+watch_unmap_event(void)
+{
+	int i;
+	struct xen_guest *guest  = NULL;
+	bool remove_request;
+
+	TAILQ_FOREACH(guest, &guest_root, next) {
+		for (i = 0; i < MAX_VIRTIO; i++) {
+			if (guest->vring[i].dom_id && guest->vring[i].removed == 0 && *guest->vring[i].flag == 0) {
+				RTE_LOG(INFO, XENHOST, "\n\n");
+				RTE_LOG(INFO, XENHOST, "  #####%s:  (%d, %d) to be removed\n",
+					__func__,
+					guest->vring[i].dom_id,
+					i);
+				destroy_device(i, guest->dom_id);
+				RTE_LOG(INFO, XENHOST, "  %s: DOM %u, vring num: %d\n",
+					__func__,
+					guest->dom_id,
+					guest->vring_num);
+			}
+		}
+	}
+
+_find_next_remove:
+	guest = NULL;
+	remove_request = false;
+	TAILQ_FOREACH(guest, &guest_root, next) {
+		if (guest->vring_num == 0) {
+			remove_request = true;
+			break;
+		}
+	}
+	if (remove_request == true) {
+		TAILQ_REMOVE(&guest_root, guest, next);
+		RTE_LOG(INFO, XENHOST, "  #####%s: destroy guest (%d)\n", __func__, guest->dom_id);
+		destroy_guest(guest);
+		goto _find_next_remove;
+	}
+	return;
+}
+
+/*
+ * OK, if the guest starts first, it is ok.
+ * if host starts first, it is ok.
+ * if guest starts, and has run for sometime, and host stops and restarts,
+ * then last_used_idx  0? how to solve this. */
+
+static void virtio_init(void)
+{
+	uint32_t len, e_num;
+	uint32_t i,j;
+	char **dom;
+	char *status;
+	int dom_id;
+	char path[PATH_MAX];
+	char node[PATH_MAX];
+	xs_transaction_t th;
+	struct xen_guest *guest;
+	struct virtio_net_config_ll *net_config;
+	char *end;
+	int val;
+
+	/* init env for watch the node */
+	if (init_watch() < 0)
+		return;
+
+	dom = xs_directory(watch.xs, XBT_NULL, "/local/domain", &e_num);
+
+	for (i = 0; i < e_num; i++) {
+		errno = 0;
+		dom_id = strtol(dom[i], &end, 0);
+		if (errno != 0 || end == NULL || dom_id == 0)
+			continue;
+
+		for (j = 0; j < RTE_MAX_ETHPORTS; j++) {
+			snprintf(node, PATH_MAX, "%s%d", VIRTIO_START, j);
+			snprintf(path, PATH_MAX, XEN_VM_NODE_FMT,
+					dom_id, node);
+
+			th = xs_transaction_start(watch.xs);
+			status = xs_read(watch.xs, th, path, &len);
+			xs_transaction_end(watch.xs, th, false);
+
+			if (status == NULL)
+				break;
+
+			/* if there's any valid virtio device */
+			errno = 0;
+			val = strtol(status, &end, 0);
+			if (errno != 0 || end == NULL || dom_id == 0)
+				val = 0;
+			if (val == 1) {
+				guest = add_xen_guest(dom_id);
+				if (guest == NULL)
+					continue;
+				RTE_LOG(INFO, XENHOST, "  there's a new virtio existed, new a virtio device\n\n");
+
+				RTE_LOG(INFO, XENHOST, "  parse_vringnode dom_id %d virtioidx %d\n",dom_id,j);
+				if (parse_vringnode(guest, j)) {
+					RTE_LOG(ERR, XENHOST, "  there is invalid information in xenstore\n");
+					TAILQ_REMOVE(&guest_root, guest, next);
+					destroy_guest(guest);
+
+					continue;
+				}
+
+				/*if pool_num > 0, then mempool has already been parsed*/
+				if (guest->pool_num == 0 && parse_mempoolnode(guest)) {
+					RTE_LOG(ERR, XENHOST, "  there is error information in xenstore\n");
+					TAILQ_REMOVE(&guest_root, guest, next);
+					destroy_guest(guest);
+					continue;
+				}
+
+				net_config = new_device(j, guest);
+				/* every thing is ready now, added into data core */
+				notify_ops->new_device(&net_config->dev);
+			}
+		}
+	}
+
+	free(dom);
+	return;
+}
+
+void
+virtio_monitor_loop(void)
+{
+	char **vec;
+	xs_transaction_t th;
+	char *buf;
+	unsigned int len;
+	unsigned int dom_id;
+	uint32_t virtio_idx;
+	struct xen_guest *guest;
+	struct virtio_net_config_ll *net_config;
+	enum fieldnames {
+		FLD_NULL = 0,
+		FLD_LOCAL,
+		FLD_DOMAIN,
+		FLD_ID,
+		FLD_CONTROL,
+		FLD_DPDK,
+		FLD_NODE,
+		_NUM_FLD
+	};
+	char *str_fld[_NUM_FLD];
+	char *str;
+	char *end;
+
+	virtio_init();
+	while (1) {
+		watch_unmap_event();
+
+		usleep(50);
+		vec = xs_check_watch(watch.xs);
+
+		if (vec == NULL)
+			continue;
+
+		th = xs_transaction_start(watch.xs);
+
+		buf = xs_read(watch.xs, th, vec[XS_WATCH_PATH],&len);
+		xs_transaction_end(watch.xs, th, false);
+
+		if (buf) {
+			/* theres' some node for vhost existed */
+			if (rte_strsplit(vec[XS_WATCH_PATH], strnlen(vec[XS_WATCH_PATH], PATH_MAX),
+						str_fld, _NUM_FLD, '/') == _NUM_FLD) {
+				if (strstr(str_fld[FLD_NODE], VIRTIO_START)) {
+					errno = 0;
+					str = str_fld[FLD_ID];
+					dom_id = strtoul(str, &end, 0);
+					if (errno != 0 || end == NULL || end == str ) {
+						RTE_LOG(INFO, XENHOST, "invalid domain id\n");
+						continue;
+					}
+
+					errno = 0;
+					str = str_fld[FLD_NODE] + sizeof(VIRTIO_START) - 1;
+					virtio_idx = strtoul(str, &end, 0);
+					if (errno != 0 || end == NULL || end == str
+							|| virtio_idx > MAX_VIRTIO) {
+						RTE_LOG(INFO, XENHOST, "invalid virtio idx\n");
+						continue;
+					}
+					RTE_LOG(INFO, XENHOST, "  #####virtio dev (%d, %d) is started\n", dom_id, virtio_idx);
+
+					guest = add_xen_guest(dom_id);
+					if (guest == NULL)
+						continue;
+					guest->dom_id = dom_id;
+					if (parse_vringnode(guest, virtio_idx)) {
+						RTE_LOG(ERR, XENHOST, "  there is invalid information in xenstore\n");
+						/*guest newly created? guest existed ?*/
+						TAILQ_REMOVE(&guest_root, guest, next);
+						destroy_guest(guest);
+						continue;
+					}
+					/*if pool_num > 0, then mempool has already been parsed*/
+					if (guest->pool_num == 0 && parse_mempoolnode(guest)) {
+						RTE_LOG(ERR, XENHOST, "  there is error information in xenstore\n");
+						TAILQ_REMOVE(&guest_root, guest, next);
+						destroy_guest(guest);
+						continue;
+					}
+
+
+					net_config = new_device(virtio_idx, guest);
+					RTE_LOG(INFO, XENHOST, "  Add to dataplane core\n");
+					notify_ops->new_device(&net_config->dev);
+
+				}
+			}
+		}
+
+		free(vec);
+	}
+	return;
+}
+
+/*
+ * Register ops so that we can add/remove device to data core.
+ */
+int
+init_virtio_xen(struct virtio_net_device_ops const *const ops)
+{
+	notify_ops = ops;
+	if (xenhost_init())
+		return -1;
+	return 0;
+}
diff --git a/examples/vhost_xen/virtio-net.h b/examples/vhost_xen/virtio-net.h
new file mode 100644
index 00000000..ab697260
--- /dev/null
+++ b/examples/vhost_xen/virtio-net.h
@@ -0,0 +1,113 @@
+/*-
+ *   BSD LICENSE
+ *
+ *   Copyright(c) 2010-2014 Intel Corporation. All rights reserved.
+ *   All rights reserved.
+ *
+ *   Redistribution and use in source and binary forms, with or without
+ *   modification, are permitted provided that the following conditions
+ *   are met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ *       notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above copyright
+ *       notice, this list of conditions and the following disclaimer in
+ *       the documentation and/or other materials provided with the
+ *       distribution.
+ *     * Neither the name of Intel Corporation nor the names of its
+ *       contributors may be used to endorse or promote products derived
+ *       from this software without specific prior written permission.
+ *
+ *   THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ *   "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ *   LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ *   A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ *   OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ *   SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ *   LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ *   DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ *   THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ *   (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ *   OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef _VIRTIO_NET_H_
+#define _VIRTIO_NET_H_
+
+#include <stdint.h>
+
+#define VQ_DESC_NUM 256
+/* Used to indicate that the device is running on a data core */
+#define VIRTIO_DEV_RUNNING 1
+
+/*
+ * Structure contains variables relevant to TX/RX virtqueues.
+ */
+struct vhost_virtqueue
+{
+	struct vring_desc  *desc;             /* Virtqueue descriptor ring. */
+	struct vring_avail *avail;            /* Virtqueue available ring. */
+	struct vring_used  *used;             /* Virtqueue used ring. */
+	uint32_t           size;              /* Size of descriptor ring. */
+	uint32_t           vhost_hlen;        /* Vhost header length (varies depending on RX merge buffers. */
+	volatile uint16_t  last_used_idx;     /* Last index used on the available ring */
+	volatile uint16_t  last_used_idx_res; /* Used for multiple devices reserving buffers. */
+} __rte_cache_aligned;
+
+/*
+ * Device structure contains all configuration information relating to the device.
+ */
+struct virtio_net
+{
+	struct vhost_virtqueue	*virtqueue_tx;	/* Contains all TX virtqueue information. */
+	struct vhost_virtqueue	*virtqueue_rx;	/* Contains all RX virtqueue information. */
+	struct virtio_memory    *mem;           /* QEMU memory and memory region information. */
+	struct ether_addr       mac_address;    /* Device MAC address (Obtained on first TX packet). */
+	uint32_t                flags;          /* Device flags. Only used to check if device is running on data core. */
+	uint32_t                vlan_tag;       /* Vlan tag for device. Currently set to device_id (0-63). */
+	uint32_t                vmdq_rx_q;
+	uint64_t                device_fh;      /* device identifier. */
+	uint16_t                coreid;
+	volatile uint8_t        ready;          /* A device is set as ready if the MAC address has been set. */
+	volatile uint8_t        remove;         /* Device is marked for removal from the data core. */
+	uint32_t                virtio_idx;     /* Index of virtio device */
+	uint32_t                dom_id;         /* Domain id of xen guest */
+} ___rte_cache_aligned;
+
+/*
+ * Device linked list structure for configuration.
+ */
+struct virtio_net_config_ll
+{
+	struct virtio_net		dev;	/* Virtio device. */
+	struct virtio_net_config_ll	*next; /* Next entry on linked list. */
+};
+
+/*
+ * Information relating to memory regions including offsets to addresses in QEMUs memory file.
+ */
+struct virtio_memory_regions {
+	uint64_t	guest_phys_address;     /* Base guest physical address of region. */
+	uint64_t	guest_phys_address_end;	/* End guest physical address of region. */
+	uint64_t	memory_size;		/* Size of region. */
+	uint64_t	userspace_address;      /* Base userspace address of region. */
+	uint64_t	address_offset;         /* Offset of region for address translation. */
+};
+
+/*
+ * Memory structure includes region and mapping information.
+ */
+struct virtio_memory {
+	uint32_t			nregions;	/* Number of memory regions. */
+	struct virtio_memory_regions 	regions[0];	/* Memory region information. */
+};
+
+/*
+ * Device operations to add/remove device.
+ */
+struct virtio_net_device_ops {
+	int (* new_device)(struct virtio_net *);	/* Add device. */
+	void (* destroy_device)	(volatile struct virtio_net *);	/* Remove device. */
+};
+
+#endif
diff --git a/examples/vhost_xen/xen_vhost.h b/examples/vhost_xen/xen_vhost.h
new file mode 100644
index 00000000..2fc304c7
--- /dev/null
+++ b/examples/vhost_xen/xen_vhost.h
@@ -0,0 +1,148 @@
+/*-
+ *   BSD LICENSE
+ *
+ *   Copyright(c) 2010-2014 Intel Corporation. All rights reserved.
+ *   All rights reserved.
+ *
+ *   Redistribution and use in source and binary forms, with or without
+ *   modification, are permitted provided that the following conditions
+ *   are met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ *       notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above copyright
+ *       notice, this list of conditions and the following disclaimer in
+ *       the documentation and/or other materials provided with the
+ *       distribution.
+ *     * Neither the name of Intel Corporation nor the names of its
+ *       contributors may be used to endorse or promote products derived
+ *       from this software without specific prior written permission.
+ *
+ *   THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ *   "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ *   LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ *   A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ *   OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ *   SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ *   LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ *   DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ *   THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ *   (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ *   OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef _XEN_VHOST_H_
+#define _XEN_VHOST_H_
+
+#include <stdint.h>
+
+#include <rte_ether.h>
+
+#include "virtio-net.h"
+
+#define RTE_LOGTYPE_XENHOST RTE_LOGTYPE_USER1
+
+#define XEN_VM_ROOTNODE_FMT  "/local/domain/%d/control/dpdk"
+#define XEN_VM_NODE_FMT      "/local/domain/%d/control/dpdk/%s"
+#define XEN_MEMPOOL_SUFFIX   "mempool_gref"
+#define XEN_RXVRING_SUFFIX   "rx_vring_gref"
+#define XEN_TXVRING_SUFFIX   "tx_vring_gref"
+#define XEN_GVA_SUFFIX       "mempool_va"
+#define XEN_VRINGFLAG_SUFFIX "vring_flag"
+#define XEN_ADDR_SUFFIX      "ether_addr"
+#define VIRTIO_START         "event_type_start_"
+
+#define XEN_GREF_SPLITTOKEN  ','
+
+#define MAX_XENVIRT_MEMPOOL 16
+#define MAX_VIRTIO  32
+#define MAX_GREF_PER_NODE 64  /* 128 MB memory */
+
+#define PAGE_SIZE   4096
+#define PAGE_PFNNUM (PAGE_SIZE / sizeof(uint32_t))
+
+#define XEN_GNTDEV_FNAME "/dev/xen/gntdev"
+
+/* xen grant reference info in one grant node */
+struct xen_gnt {
+	uint32_t gref;	/* grant reference for this node */
+	union {
+		int gref;		/* grant reference */
+		uint32_t pfn_num;	/* guest pfn number of grant reference */
+	} gref_pfn[PAGE_PFNNUM];
+}__attribute__((__packed__));
+
+
+/* structure for mempool or vring node list */
+struct xen_gntnode {
+	uint32_t gnt_num;           /* grant reference number */
+	struct xen_gnt *gnt_info;   /* grant reference info */
+};
+
+
+struct xen_vring {
+	uint32_t dom_id;
+	uint32_t virtio_idx;    /* index of virtio device */
+	void *rxvring_addr;     /* mapped virtual address of rxvring */
+	void *txvring_addr;     /* mapped virtual address of txvring */
+	uint32_t rxpfn_num;     /* number of gpfn for rxvring */
+	uint32_t txpfn_num;	/* number of gpfn for txvring */
+	uint32_t *rxpfn_tbl;    /* array of rxvring gpfn */
+	uint32_t *txpfn_tbl;	/* array of txvring gpfn */
+	uint64_t *rx_pindex;    /* index used to release rx grefs */
+	uint64_t *tx_pindex;    /* index used to release tx grefs */
+	uint64_t  flag_index;
+	uint8_t  *flag; 	/* cleared to zero on guest unmap */
+	struct ether_addr addr; /* ethernet address of virtio device */
+	uint8_t   removed;
+
+};
+
+struct xen_mempool {
+	uint32_t dom_id;      /* guest domain id */
+	uint32_t pool_idx;    /* index of memory pool */
+	void *gva;            /* guest virtual address of mbuf pool */
+	void *hva;            /* host virtual address of mbuf pool */
+	uint32_t mempfn_num;  /* number of gpfn for mbuf pool */
+	uint32_t *mempfn_tbl; /* array of mbuf pool gpfn */
+	uint64_t *pindex;     /* index used to release grefs */
+};
+
+struct xen_guest {
+	TAILQ_ENTRY(xen_guest) next;
+	int32_t dom_id;       /* guest domain id */
+	uint32_t pool_num;    /* number of mbuf pool of the guest */
+	uint32_t vring_num;   /* number of virtio ports of the guest */
+	/* array contain the guest mbuf pool info */
+	struct xen_mempool mempool[MAX_XENVIRT_MEMPOOL];
+	/* array contain the guest rx/tx vring info */
+	struct xen_vring vring[MAX_VIRTIO];
+};
+
+TAILQ_HEAD(xen_guestlist, xen_guest);
+
+int
+parse_mempoolnode(struct xen_guest *guest);
+
+int
+xenhost_init(void);
+
+int
+parse_vringnode(struct xen_guest *guest, uint32_t virtio_idx);
+
+int
+parse_mempoolnode(struct xen_guest *guest);
+
+void
+cleanup_mempool(struct xen_mempool *mempool);
+
+void
+cleanup_vring(struct xen_vring *vring);
+
+void
+virtio_monitor_loop(void);
+
+int
+init_virtio_xen(struct virtio_net_device_ops const * const);
+
+#endif
diff --git a/examples/vhost_xen/xenstore_parse.c b/examples/vhost_xen/xenstore_parse.c
new file mode 100644
index 00000000..26d24320
--- /dev/null
+++ b/examples/vhost_xen/xenstore_parse.c
@@ -0,0 +1,775 @@
+/*-
+ *   BSD LICENSE
+ *
+ *   Copyright(c) 2010-2014 Intel Corporation. All rights reserved.
+ *   All rights reserved.
+ *
+ *   Redistribution and use in source and binary forms, with or without
+ *   modification, are permitted provided that the following conditions
+ *   are met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ *       notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above copyright
+ *       notice, this list of conditions and the following disclaimer in
+ *       the documentation and/or other materials provided with the
+ *       distribution.
+ *     * Neither the name of Intel Corporation nor the names of its
+ *       contributors may be used to endorse or promote products derived
+ *       from this software without specific prior written permission.
+ *
+ *   THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ *   "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ *   LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ *   A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ *   OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ *   SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ *   LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ *   DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ *   THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ *   (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ *   OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <stdint.h>
+#include <unistd.h>
+#include <inttypes.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <sys/ioctl.h>
+#include <sys/mman.h>
+#include <xen/sys/gntalloc.h>
+#include <xen/sys/gntdev.h>
+#include <xen/xen-compat.h>
+#if __XEN_LATEST_INTERFACE_VERSION__ < 0x00040200
+#include <xs.h>
+#else
+#include <xenstore.h>
+#endif
+
+#include <rte_common.h>
+#include <rte_memory.h>
+#include <rte_eal.h>
+#include <rte_malloc.h>
+#include <rte_string_fns.h>
+#include <rte_log.h>
+#include <rte_debug.h>
+
+#include "xen_vhost.h"
+
+/* xenstore handle */
+static struct xs_handle *xs = NULL;
+
+/* gntdev file descriptor to map grant pages */
+static int d_fd = -1;
+
+/*
+ *  The grant node format in xenstore for vring/mpool is like:
+ *  idx#_rx_vring_gref = "gref1#, gref2#, gref3#"
+ *  idx#_mempool_gref  = "gref1#, gref2#, gref3#"
+ *  each gref# is the grant reference for a shared page.
+ *  In each shared page, we store the grant_node_item items.
+ */
+struct grant_node_item {
+	uint32_t gref;
+	uint32_t pfn;
+} __attribute__((packed));
+
+int cmdline_parse_etheraddr(void *tk, const char *srcbuf,
+	void *res, unsigned ressize);
+
+/* Map grant ref refid at addr_ori*/
+static void *
+xen_grant_mmap(void *addr_ori, int domid, int refid, uint64_t *pindex)
+{
+	struct ioctl_gntdev_map_grant_ref arg;
+	void *addr = NULL;
+	int pg_sz = getpagesize();
+
+	arg.count = 1;
+	arg.refs[0].domid = domid;
+	arg.refs[0].ref = refid;
+
+	int rv = ioctl(d_fd, IOCTL_GNTDEV_MAP_GRANT_REF, &arg);
+	if (rv) {
+		RTE_LOG(ERR, XENHOST, "  %s: (%d,%d) %s (ioctl failed)\n", __func__,
+				domid, refid, strerror(errno));
+		return NULL;
+	}
+
+	if (addr_ori == NULL)
+		addr = mmap(addr_ori, pg_sz, PROT_READ|PROT_WRITE, MAP_SHARED,
+				d_fd, arg.index);
+	else
+		addr = mmap(addr_ori, pg_sz, PROT_READ|PROT_WRITE, MAP_SHARED | MAP_FIXED,
+				d_fd, arg.index);
+
+	if (addr == MAP_FAILED) {
+		RTE_LOG(ERR, XENHOST, "  %s: (%d, %d) %s (map failed)\n", __func__,
+				domid, refid, strerror(errno));
+		return NULL;
+	}
+
+	if (pindex)
+		*pindex = arg.index;
+
+	return addr;
+}
+
+/* Unmap one grant ref, and munmap must be called before this */
+static int
+xen_unmap_grant_ref(uint64_t index)
+{
+	struct ioctl_gntdev_unmap_grant_ref arg;
+	int rv;
+
+	arg.count = 1;
+	arg.index = index;
+	rv = ioctl(d_fd, IOCTL_GNTDEV_UNMAP_GRANT_REF, &arg);
+	if (rv) {
+		RTE_LOG(ERR, XENHOST, "  %s: index 0x%" PRIx64 "unmap failed\n", __func__, index);
+		return -1;
+	}
+	return 0;
+}
+
+/*
+ * Reserve a virtual address space.
+ * On success, returns the pointer. On failure, returns NULL.
+ */
+static void *
+get_xen_virtual(size_t size, size_t page_sz)
+{
+	void *addr;
+	uintptr_t aligned_addr;
+
+	addr = mmap(NULL, size + page_sz, PROT_READ, MAP_SHARED | MAP_ANONYMOUS, -1, 0);
+	if (addr == MAP_FAILED) {
+		RTE_LOG(ERR, XENHOST, "failed get a virtual area\n");
+		return NULL;
+	}
+
+	aligned_addr = RTE_ALIGN_CEIL((uintptr_t)addr, page_sz);
+	munmap(addr, aligned_addr - (uintptr_t)addr);
+	munmap((void *)(aligned_addr + size), page_sz + (uintptr_t)addr - aligned_addr);
+	addr = (void *)(aligned_addr);
+
+	return addr;
+}
+
+static void
+free_xen_virtual(void *addr, size_t size, size_t page_sz __rte_unused)
+{
+	if (addr)
+		munmap(addr, size);
+}
+
+/*
+ * Returns val str in xenstore.
+ * @param path
+ *  Full path string for key
+ * @return
+ *  Pointer to Val str, NULL on failure
+ */
+static char *
+xen_read_node(char *path, uint32_t *len)
+{
+	char *buf;
+
+	buf = xs_read(xs, XBT_NULL, path, len);
+	return buf;
+}
+
+static int
+cal_pagenum(struct xen_gnt *gnt)
+{
+	unsigned int i;
+	/*
+	 * the items in the page are in the format of
+	 * gref#,pfn#,...,gref#,pfn#
+	 * FIXME, 0 is reserved by system, use it as terminator.
+	 */
+	for (i = 0; i < (PAGE_PFNNUM) / 2; i++) {
+		if (gnt->gref_pfn[i * 2].gref <= 0)
+			break;
+	}
+
+	return i;
+}
+
+/* Frees memory allocated to a grant node */
+static void
+xen_free_gntnode(struct xen_gntnode *gntnode)
+{
+	if (gntnode == NULL)
+		return;
+	free(gntnode->gnt_info);
+	free(gntnode);
+}
+
+/*
+ * Parse a grant node.
+ * @param domid
+ *  Guest domain id.
+ * @param path
+ *  Full path string for a grant node, like for the following (key, val) pair
+ *  idx#_mempool_gref = "gref#, gref#, gref#"
+ *  path = 'local/domain/domid/control/dpdk/idx#_mempool_gref'
+ *  gref# is a shared page contain packed (gref,pfn) entries
+ * @return
+ *  Returns the pointer to xen_gntnode
+ */
+static struct xen_gntnode *
+parse_gntnode(int dom_id, char *path)
+{
+	char **gref_list = NULL;
+	uint32_t i, len, gref_num;
+	void *addr = NULL;
+	char *buf = NULL;
+	struct xen_gntnode *gntnode = NULL;
+	struct xen_gnt *gnt = NULL;
+	int pg_sz = getpagesize();
+	char *end;
+	uint64_t index;
+
+	if ((buf = xen_read_node(path, &len)) == NULL)
+		goto err;
+
+	gref_list = malloc(MAX_GREF_PER_NODE * sizeof(char *));
+	if (gref_list == NULL)
+		goto err;
+
+	gref_num = rte_strsplit(buf, len, gref_list, MAX_GREF_PER_NODE,
+			XEN_GREF_SPLITTOKEN);
+	if (gref_num == 0) {
+		RTE_LOG(ERR, XENHOST, "  %s: invalid grant node format\n", __func__);
+		goto err;
+	}
+
+	gntnode = calloc(1, sizeof(struct xen_gntnode));
+	gnt = calloc(gref_num, sizeof(struct xen_gnt));
+	if (gnt == NULL || gntnode == NULL)
+		goto err;
+
+	for (i = 0; i < gref_num; i++) {
+		errno = 0;
+		gnt[i].gref = strtol(gref_list[i], &end, 0);
+		if (errno != 0 || end == NULL || end == gref_list[i] ||
+			(*end != '\0' &&  *end != XEN_GREF_SPLITTOKEN)) {
+			RTE_LOG(ERR, XENHOST, "  %s: parse grant node item failed\n", __func__);
+			goto err;
+		}
+		addr = xen_grant_mmap(NULL, dom_id, gnt[i].gref, &index);
+		if (addr == NULL) {
+			RTE_LOG(ERR, XENHOST, "  %s: map gref %u failed\n", __func__, gnt[i].gref);
+			goto err;
+		}
+		RTE_LOG(INFO, XENHOST, "      %s: map gref %u to %p\n", __func__, gnt[i].gref, addr);
+		memcpy(gnt[i].gref_pfn, addr, pg_sz);
+		if (munmap(addr, pg_sz)) {
+			RTE_LOG(INFO, XENHOST, "  %s: unmap gref %u failed\n", __func__, gnt[i].gref);
+			goto err;
+		}
+		if (xen_unmap_grant_ref(index)) {
+			RTE_LOG(INFO, XENHOST, "  %s: release gref %u failed\n", __func__, gnt[i].gref);
+			goto err;
+		}
+
+	}
+
+	gntnode->gnt_num  = gref_num;
+	gntnode->gnt_info = gnt;
+
+	free(buf);
+	free(gref_list);
+	return gntnode;
+
+err:
+	free(gnt);
+	free(gntnode);
+	free(gref_list);
+	free(buf);
+	return NULL;
+}
+
+/*
+ * This function maps grant node of vring or mbuf pool to a continous virtual address space,
+ * and returns mapped address, pfn array, index array
+ * @param gntnode
+ *  Pointer to grant node
+ * @param domid
+ *  Guest domain id
+ * @param ppfn
+ *  Pointer to pfn array, caller should free this array
+ * @param pgs
+ *  Pointer to number of pages
+ * @param ppindex
+ *  Pointer to index array, used to release grefs when to free this node
+ * @return
+ *  Pointer to mapped virtual address, NULL on failure
+ */
+static void *
+map_gntnode(struct xen_gntnode *gntnode, int domid, uint32_t **ppfn, uint32_t *pgs, uint64_t **ppindex)
+{
+	struct xen_gnt *gnt;
+	uint32_t i, j;
+	size_t total_pages = 0;
+	void *addr;
+	uint32_t *pfn;
+	uint64_t *pindex;
+	uint32_t pfn_num = 0;
+	int pg_sz;
+
+	if (gntnode == NULL)
+		return NULL;
+
+	pg_sz = getpagesize();
+	for (i = 0; i < gntnode->gnt_num; i++) {
+		gnt = gntnode->gnt_info + i;
+		total_pages += cal_pagenum(gnt);
+	}
+	if ((addr = get_xen_virtual(total_pages * pg_sz, pg_sz)) == NULL) {
+		RTE_LOG(ERR, XENHOST, "  %s: failed get_xen_virtual\n", __func__);
+		return NULL;
+	}
+	pfn = calloc(total_pages, (size_t)sizeof(uint32_t));
+	pindex = calloc(total_pages, (size_t)sizeof(uint64_t));
+	if (pfn == NULL || pindex == NULL) {
+		free_xen_virtual(addr, total_pages * pg_sz, pg_sz);
+		free(pfn);
+		free(pindex);
+		return NULL;
+	}
+
+	RTE_LOG(INFO, XENHOST, "    %s: total pages:%zu, map to [%p, %p]\n", __func__, total_pages, addr, RTE_PTR_ADD(addr, total_pages * pg_sz - 1));
+	for (i = 0; i < gntnode->gnt_num; i++) {
+		gnt = gntnode->gnt_info + i;
+		for (j = 0; j < (PAGE_PFNNUM) / 2; j++) {
+			if ((gnt->gref_pfn[j * 2].gref) <= 0)
+				goto _end;
+			/*alternative: batch map, or through libxc*/
+			if (xen_grant_mmap(RTE_PTR_ADD(addr, pfn_num * pg_sz),
+					domid,
+					gnt->gref_pfn[j * 2].gref,
+					&pindex[pfn_num]) == NULL) {
+				goto mmap_failed;
+			}
+			pfn[pfn_num] = gnt->gref_pfn[j * 2 + 1].pfn_num;
+			pfn_num++;
+		}
+	}
+
+mmap_failed:
+	if (pfn_num)
+		munmap(addr, pfn_num * pg_sz);
+	for (i = 0; i < pfn_num; i++) {
+		xen_unmap_grant_ref(pindex[i]);
+	}
+	free(pindex);
+	free(pfn);
+	return NULL;
+
+_end:
+	if (ppindex)
+		*ppindex = pindex;
+	else
+		free(pindex);
+	if (ppfn)
+		*ppfn = pfn;
+	else
+		free(pfn);
+	if (pgs)
+		*pgs = total_pages;
+
+	return addr;
+}
+
+static int
+parse_mpool_va(struct xen_mempool *mempool)
+{
+	char path[PATH_MAX] = {0};
+	char *buf;
+	uint32_t len;
+	char *end;
+	int ret = -1;
+
+	errno = 0;
+	snprintf(path, sizeof(path),
+		XEN_VM_ROOTNODE_FMT"/%d_"XEN_GVA_SUFFIX,
+		mempool->dom_id, mempool->pool_idx);
+
+	if((buf = xen_read_node(path, &len)) == NULL)
+		goto out;
+	mempool->gva = (void *)strtoul(buf, &end, 16);
+	if (errno != 0 || end == NULL || end == buf || *end != '\0') {
+		mempool->gva = NULL;
+		goto out;
+	}
+	ret = 0;
+out:
+	free(buf);
+	return ret;
+}
+
+/*
+ * map mbuf pool
+ */
+static int
+map_mempoolnode(struct xen_gntnode *gntnode,
+			struct xen_mempool *mempool)
+{
+	if (gntnode == NULL || mempool == NULL)
+		return -1;
+
+	mempool->hva =
+		map_gntnode(gntnode, mempool->dom_id, &mempool->mempfn_tbl, &mempool->mempfn_num, &mempool->pindex);
+
+	RTE_LOG(INFO, XENHOST, "  %s: map mempool at %p\n", __func__, (void *)mempool->hva);
+	if (mempool->hva)
+		return 0;
+	else {
+		return -1;
+	}
+}
+
+void
+cleanup_mempool(struct xen_mempool *mempool)
+{
+	int pg_sz = getpagesize();
+	uint32_t i;
+
+	if (mempool->hva)
+		munmap(mempool->hva, mempool->mempfn_num * pg_sz);
+	mempool->hva = NULL;
+
+	if (mempool->pindex) {
+		RTE_LOG(INFO, XENHOST, "  %s: unmap dom %02u mempool%02u %u grefs\n",
+			__func__,
+			mempool->dom_id,
+			mempool->pool_idx,
+			mempool->mempfn_num);
+		for (i = 0; i < mempool->mempfn_num; i ++) {
+			xen_unmap_grant_ref(mempool->pindex[i]);
+		}
+	}
+	mempool->pindex = NULL;
+
+	free(mempool->mempfn_tbl);
+	mempool->mempfn_tbl = NULL;
+}
+
+/*
+ * process mempool node idx#_mempool_gref, idx = 0, 1, 2...
+ * untill we encounter a node that doesn't exist.
+ */
+int
+parse_mempoolnode(struct xen_guest *guest)
+{
+	uint32_t i, len;
+	char path[PATH_MAX] = {0};
+	struct xen_gntnode *gntnode = NULL;
+	struct xen_mempool *mempool = NULL;
+	char *buf;
+
+	bzero(&guest->mempool, MAX_XENVIRT_MEMPOOL * sizeof(guest->mempool[0]));
+	guest->pool_num = 0;
+
+	while (1) {
+		/* check if null terminated */
+		snprintf(path, sizeof(path),
+			XEN_VM_ROOTNODE_FMT"/%d_"XEN_MEMPOOL_SUFFIX,
+			guest->dom_id,
+			guest->pool_num);
+
+		if ((buf = xen_read_node(path, &len)) != NULL) {
+			/* this node exists */
+			free(buf);
+		} else {
+			if (guest->pool_num == 0) {
+				RTE_LOG(ERR, PMD, "no mempool found\n");
+				return -1;
+			}
+			break;
+		}
+
+		mempool = &guest->mempool[guest->pool_num];
+		mempool->dom_id = guest->dom_id;
+		mempool->pool_idx = guest->pool_num;
+
+		RTE_LOG(INFO, XENHOST, "  %s: mempool %u parse gntnode %s\n", __func__, guest->pool_num, path);
+		gntnode = parse_gntnode(guest->dom_id, path);
+		if (gntnode == NULL)
+			goto err;
+
+		if (parse_mpool_va(mempool))
+			goto err;
+
+		RTE_LOG(INFO, XENHOST, "  %s: mempool %u map gntnode %s\n", __func__, guest->pool_num, path);
+		if (map_mempoolnode(gntnode, mempool))
+			goto err;
+
+		xen_free_gntnode(gntnode);
+		guest->pool_num++;
+	}
+
+	return 0;
+err:
+	if (gntnode)
+		xen_free_gntnode(gntnode);
+	for (i = 0; i <  MAX_XENVIRT_MEMPOOL ; i++) {
+		cleanup_mempool(&guest->mempool[i]);
+	}
+	/* reinitialise mempool */
+	bzero(&guest->mempool, MAX_XENVIRT_MEMPOOL * sizeof(guest->mempool[0]));
+	return -1;
+}
+
+static int
+xen_map_vringflag(struct xen_vring *vring)
+{
+	char path[PATH_MAX] = {0};
+	char *buf;
+	uint32_t len,gref;
+	int pg_sz = getpagesize();
+	char *end;
+
+	snprintf(path, sizeof(path),
+		XEN_VM_ROOTNODE_FMT"/%d_"XEN_VRINGFLAG_SUFFIX,
+		vring->dom_id, vring->virtio_idx);
+
+	if((buf = xen_read_node(path, &len)) == NULL)
+		goto err;
+
+	errno = 0;
+	gref = strtol(buf, &end, 0);
+	if (errno != 0 || end == NULL || end == buf) {
+		goto err;
+	}
+	vring->flag = xen_grant_mmap(0, vring->dom_id, gref, &vring->flag_index);
+	if (vring->flag == NULL || *vring->flag == 0)
+		goto err;
+
+	free(buf);
+	return 0;
+err:
+	free(buf);
+	if (vring->flag) {
+		munmap(vring->flag, pg_sz);
+		vring->flag = NULL;
+		xen_unmap_grant_ref(vring->flag_index);
+	}
+	return -1;
+}
+
+
+static int
+xen_map_rxvringnode(struct xen_gntnode *gntnode,
+				struct xen_vring *vring)
+{
+	vring->rxvring_addr =
+		map_gntnode(gntnode, vring->dom_id, &vring->rxpfn_tbl, &vring->rxpfn_num, &vring->rx_pindex);
+	RTE_LOG(INFO, XENHOST, "  %s: map rx vring at %p\n", __func__, (void *)vring->rxvring_addr);
+	if (vring->rxvring_addr)
+		return 0;
+	else
+		return -1;
+}
+
+static int
+xen_map_txvringnode(struct xen_gntnode *gntnode,
+				struct xen_vring *vring)
+{
+	vring->txvring_addr =
+		map_gntnode(gntnode, vring->dom_id, &vring->txpfn_tbl, &vring->txpfn_num, &vring->tx_pindex);
+	RTE_LOG(INFO, XENHOST, "  %s: map tx vring at %p\n", __func__, (void *)vring->txvring_addr);
+	if (vring->txvring_addr)
+		return 0;
+	else
+		return -1;
+}
+
+void
+cleanup_vring(struct xen_vring *vring)
+{
+	int pg_sz = getpagesize();
+	uint32_t i;
+
+	RTE_LOG(INFO, XENHOST, "  %s: cleanup dom %u vring %u\n", __func__, vring->dom_id, vring->virtio_idx);
+	if (vring->rxvring_addr) {
+		munmap(vring->rxvring_addr, vring->rxpfn_num * pg_sz);
+		RTE_LOG(INFO, XENHOST, "  %s: unmap rx vring [%p, %p]\n",
+			__func__,
+			vring->rxvring_addr,
+			RTE_PTR_ADD(vring->rxvring_addr,
+			vring->rxpfn_num * pg_sz - 1));
+	}
+	vring->rxvring_addr = NULL;
+
+
+	if (vring->rx_pindex) {
+		RTE_LOG(INFO, XENHOST, "  %s: unmap rx vring %u grefs\n", __func__, vring->rxpfn_num);
+		for (i = 0; i < vring->rxpfn_num; i++) {
+			xen_unmap_grant_ref(vring->rx_pindex[i]);
+		}
+	}
+	vring->rx_pindex = NULL;
+
+	free(vring->rxpfn_tbl);
+	vring->rxpfn_tbl = NULL;
+
+	if (vring->txvring_addr) {
+		munmap(vring->txvring_addr, vring->txpfn_num * pg_sz);
+		RTE_LOG(INFO, XENHOST, "  %s: unmap tx vring [%p, %p]\n",
+			__func__,
+			vring->txvring_addr,
+			RTE_PTR_ADD(vring->txvring_addr,
+			vring->txpfn_num * pg_sz - 1));
+	}
+	vring->txvring_addr = NULL;
+
+	if (vring->tx_pindex) {
+		RTE_LOG(INFO, XENHOST, "  %s: unmap tx vring %u grefs\n", __func__, vring->txpfn_num);
+		for (i = 0; i < vring->txpfn_num; i++) {
+			xen_unmap_grant_ref(vring->tx_pindex[i]);
+		}
+	}
+	vring->tx_pindex = NULL;
+
+	free(vring->txpfn_tbl);
+	vring->txpfn_tbl = NULL;
+
+	if (vring->flag) {
+		if (!munmap((void *)vring->flag, pg_sz))
+			RTE_LOG(INFO, XENHOST, "  %s: unmap flag page at %p\n", __func__, vring->flag);
+		if (!xen_unmap_grant_ref(vring->flag_index))
+			RTE_LOG(INFO, XENHOST, "  %s: release flag ref index 0x%" PRIx64 "\n", __func__, vring->flag_index);
+	}
+	vring->flag = NULL;
+	return;
+}
+
+
+
+static int
+xen_parse_etheraddr(struct xen_vring *vring)
+{
+	char path[PATH_MAX] = {0};
+	char *buf;
+	uint32_t len;
+	int ret = -1;
+
+	snprintf(path, sizeof(path),
+		XEN_VM_ROOTNODE_FMT"/%d_"XEN_ADDR_SUFFIX,
+		vring->dom_id, vring->virtio_idx);
+
+	if ((buf = xen_read_node(path, &len)) == NULL)
+		goto out;
+
+	if (cmdline_parse_etheraddr(NULL, buf, &vring->addr,
+			sizeof(vring->addr)) < 0)
+		goto out;
+	ret = 0;
+out:
+	free(buf);
+	return ret;
+}
+
+
+int
+parse_vringnode(struct xen_guest *guest, uint32_t virtio_idx)
+{
+	char path[PATH_MAX] = {0};
+	struct xen_gntnode *rx_gntnode = NULL;
+	struct xen_gntnode *tx_gntnode = NULL;
+	struct xen_vring *vring = NULL;
+
+	/*check if null terminated */
+	snprintf(path, sizeof(path),
+		XEN_VM_ROOTNODE_FMT"/%d_"XEN_RXVRING_SUFFIX,
+		guest->dom_id,
+		virtio_idx);
+
+	RTE_LOG(INFO, XENHOST, "  %s: virtio %u parse rx gntnode %s\n", __func__, virtio_idx, path);
+	rx_gntnode = parse_gntnode(guest->dom_id, path);
+	if (rx_gntnode == NULL)
+		goto err;
+
+	/*check if null terminated */
+	snprintf(path, sizeof(path),
+		XEN_VM_ROOTNODE_FMT"/%d_"XEN_TXVRING_SUFFIX,
+		guest->dom_id,
+		virtio_idx);
+
+	RTE_LOG(INFO, XENHOST, "  %s: virtio %u parse tx gntnode %s\n", __func__, virtio_idx, path);
+	tx_gntnode = parse_gntnode(guest->dom_id, path);
+	if (tx_gntnode == NULL)
+		goto err;
+
+	vring = &guest->vring[virtio_idx];
+	bzero(vring, sizeof(*vring));
+	vring->dom_id = guest->dom_id;
+	vring->virtio_idx = virtio_idx;
+
+	if (xen_parse_etheraddr(vring) != 0)
+		goto err;
+
+	RTE_LOG(INFO, XENHOST, "  %s: virtio %u map rx gntnode %s\n", __func__, virtio_idx, path);
+	if (xen_map_rxvringnode(rx_gntnode, vring) != 0)
+		goto err;
+
+	RTE_LOG(INFO, XENHOST, "  %s: virtio %u map tx gntnode %s\n", __func__, virtio_idx, path);
+	if (xen_map_txvringnode(tx_gntnode, vring) != 0)
+		goto err;
+
+	if (xen_map_vringflag(vring) != 0)
+		goto err;
+
+	guest->vring_num++;
+
+	xen_free_gntnode(rx_gntnode);
+	xen_free_gntnode(tx_gntnode);
+
+	return 0;
+
+err:
+	if (rx_gntnode)
+		xen_free_gntnode(rx_gntnode);
+	if (tx_gntnode)
+		xen_free_gntnode(tx_gntnode);
+	if (vring) {
+		cleanup_vring(vring);
+		bzero(vring, sizeof(*vring));
+	}
+	return -1;
+}
+
+/*
+ * Open xen grant dev driver
+ * @return
+ *  0 on success, -1 on failure.
+ */
+static int
+xen_grant_init(void)
+{
+	d_fd = open(XEN_GNTDEV_FNAME, O_RDWR);
+
+	return d_fd == -1? (-1): (0);
+}
+
+/*
+ * Initialise xenstore handle and open grant dev driver.
+ * @return
+ *  0 on success, -1 on failure.
+ */
+int
+xenhost_init(void)
+{
+	xs = xs_daemon_open();
+	if (xs == NULL) {
+		rte_panic("failed initialize xen daemon handler");
+		return -1;
+	}
+	if (xen_grant_init())
+		return -1;
+	return 0;
+}