[dpdk-dev] [PATCH v4 2/2] vhost: Add vhost-user-blk example which support inflight

[JinYu <jin.yu@intel.com>]

A vhost-user-blk example that support inflight feature. It uses the
new APIs that introduced in the first patch, so It can show how there
APIs work to support inflight feature.

Signed-off-by: Jin Yu <jin.yu@intel.com>
---
V1 - add the case.
V2 - add the rte_vhost prefix.
V3 - add packed ring support
---
 examples/vhost_blk/Makefile           |   67 ++
 examples/vhost_blk/blk.c              |  122 +++
 examples/vhost_blk/blk_spec.h         |   95 +++
 examples/vhost_blk/meson.build        |   20 +
 examples/vhost_blk/vhost_blk.c        | 1054 +++++++++++++++++++++++++
 examples/vhost_blk/vhost_blk.h        |  114 +++
 examples/vhost_blk/vhost_blk_compat.c |  193 +++++
 7 files changed, 1665 insertions(+)
 create mode 100644 examples/vhost_blk/Makefile
 create mode 100644 examples/vhost_blk/blk.c
 create mode 100644 examples/vhost_blk/blk_spec.h
 create mode 100644 examples/vhost_blk/meson.build
 create mode 100644 examples/vhost_blk/vhost_blk.c
 create mode 100644 examples/vhost_blk/vhost_blk.h
 create mode 100644 examples/vhost_blk/vhost_blk_compat.c

diff --git a/examples/vhost_blk/Makefile b/examples/vhost_blk/Makefile
new file mode 100644
index 000000000..52e9befd8
--- /dev/null
+++ b/examples/vhost_blk/Makefile
@@ -0,0 +1,67 @@
+# SPDX-License-Identifier: BSD-3-Clause
+# Copyright(c) 2010-2017 Intel Corporation
+
+# binary name
+APP = vhost-blk
+
+# all source are stored in SRCS-y
+SRCS-y := blk.c vhost_blk.c vhost_blk_compat.c
+
+# Build using pkg-config variables if possible
+$(shell pkg-config --exists libdpdk)
+ifeq ($(.SHELLSTATUS),0)
+
+all: shared
+.PHONY: shared static
+shared: build/$(APP)-shared
+	ln -sf $(APP)-shared build/$(APP)
+static: build/$(APP)-static
+	ln -sf $(APP)-static build/$(APP)
+
+CFLAGS += -D_FILE_OFFSET_BITS=64
+LDFLAGS += -pthread
+
+PC_FILE := $(shell pkg-config --path libdpdk)
+CFLAGS += -O3 $(shell pkg-config --cflags libdpdk)
+LDFLAGS_SHARED = $(shell pkg-config --libs libdpdk)
+LDFLAGS_STATIC = -Wl,-Bstatic $(shell pkg-config --static --libs libdpdk)
+
+build/$(APP)-shared: $(SRCS-y) Makefile $(PC_FILE) | build
+	$(CC) $(CFLAGS) $(SRCS-y) -o $@ $(LDFLAGS) $(LDFLAGS_SHARED)
+
+build/$(APP)-static: $(SRCS-y) Makefile $(PC_FILE) | build
+	$(CC) $(CFLAGS) $(SRCS-y) -o $@ $(LDFLAGS) $(LDFLAGS_STATIC)
+
+build:
+	@mkdir -p $@
+
+.PHONY: clean
+clean:
+	rm -f build/$(APP) build/$(APP)-static build/$(APP)-shared
+	test -d build && rmdir -p build || true
+
+else # Build using legacy build system
+
+ifeq ($(RTE_SDK),)
+$(error "Please define RTE_SDK environment variable")
+endif
+
+# Default target, detect a build directory, by looking for a path with a .config
+RTE_TARGET ?= $(notdir $(abspath $(dir $(firstword $(wildcard $(RTE_SDK)/*/.config)))))
+
+include $(RTE_SDK)/mk/rte.vars.mk
+
+ifneq ($(CONFIG_RTE_EXEC_ENV_LINUX),y)
+$(info This application can only operate in a linux environment, \
+please change the definition of the RTE_TARGET environment variable)
+all:
+else
+
+CFLAGS += -D_FILE_OFFSET_BITS=64
+CFLAGS += -O2
+#CFLAGS += $(WERROR_FLAGS)
+
+include $(RTE_SDK)/mk/rte.extapp.mk
+
+endif
+endif
diff --git a/examples/vhost_blk/blk.c b/examples/vhost_blk/blk.c
new file mode 100644
index 000000000..3ecd0e206
--- /dev/null
+++ b/examples/vhost_blk/blk.c
@@ -0,0 +1,122 @@
+/* SPDX-License-Identifier: BSD-3-Clause
+ * Copyright(c) 2010-2019 Intel Corporation
+ */
+
+/**
+ * This work is largely based on the "vhost-user-blk" implementation by
+ * SPDK(https://github.com/spdk/spdk).
+ */
+
+#include <stdio.h>
+#include <stdint.h>
+#include <unistd.h>
+#include <assert.h>
+#include <ctype.h>
+#include <string.h>
+#include <stddef.h>
+
+#include <rte_atomic.h>
+#include <rte_cycles.h>
+#include <rte_log.h>
+#include <rte_malloc.h>
+#include <rte_byteorder.h>
+#include <rte_string_fns.h>
+
+#include "vhost_blk.h"
+#include "blk_spec.h"
+
+static void
+vhost_strcpy_pad(void *dst, const char *src, size_t size, int pad)
+{
+	size_t len;
+
+	len = strlen(src);
+	if (len < size) {
+		memcpy(dst, src, len);
+		memset((char *)dst + len, pad, size - len);
+	} else {
+		memcpy(dst, src, size);
+	}
+}
+
+static int
+vhost_bdev_blk_readwrite(struct vhost_block_dev *bdev,
+			  struct vhost_blk_task *task,
+			  uint64_t lba_512, __rte_unused uint32_t xfer_len)
+{
+	uint32_t i;
+	uint64_t offset;
+	uint32_t nbytes = 0;
+
+	offset = lba_512 * 512;
+
+	for (i = 0; i < task->iovs_cnt; i++) {
+		if (task->dxfer_dir == BLK_DIR_TO_DEV)
+			memcpy(bdev->data + offset, task->iovs[i].iov_base,
+			       task->iovs[i].iov_len);
+		else
+			memcpy(task->iovs[i].iov_base, bdev->data + offset,
+			       task->iovs[i].iov_len);
+		offset += task->iovs[i].iov_len;
+		nbytes += task->iovs[i].iov_len;
+	}
+
+	return nbytes;
+}
+
+int
+vhost_bdev_process_blk_commands(struct vhost_block_dev *bdev,
+				 struct vhost_blk_task *task)
+{
+	int used_len;
+
+	if (unlikely(task->data_len > (bdev->blockcnt * bdev->blocklen))) {
+		fprintf(stderr, "read or write beyond capacity\n");
+		return VIRTIO_BLK_S_UNSUPP;
+	}
+
+	switch (task->req->type) {
+	case VIRTIO_BLK_T_IN:
+		if (unlikely(task->data_len == 0 || (task->data_len & (512 - 1)) != 0)) {
+			fprintf(stderr,
+				"%s - passed IO buffer is not multiple of 512b"
+				"(req_idx = %"PRIu16").\n",
+				task->req->type ? "WRITE" : "READ", task->head_idx);
+			return VIRTIO_BLK_S_UNSUPP;
+		}
+
+		task->dxfer_dir = BLK_DIR_FROM_DEV;
+		vhost_bdev_blk_readwrite(bdev, task,
+					 task->req->sector, task->data_len);
+		break;
+	case VIRTIO_BLK_T_OUT:
+		if (unlikely(task->data_len == 0 || (task->data_len & (512 - 1)) != 0)) {
+			fprintf(stderr,
+				"%s - passed IO buffer is not multiple of 512b"
+				"(req_idx = %"PRIu16").\n",
+				task->req->type ? "WRITE" : "READ", task->head_idx);
+			return VIRTIO_BLK_S_UNSUPP;
+		}
+
+		if (task->readtype) {
+			fprintf(stderr, "type isn't right\n");
+			return VIRTIO_BLK_S_IOERR;
+		}
+		task->dxfer_dir = BLK_DIR_TO_DEV;
+		vhost_bdev_blk_readwrite(bdev, task,
+					 task->req->sector, task->data_len);
+		break;
+	case VIRTIO_BLK_T_GET_ID:
+		if (!task->iovs_cnt || task->data_len)
+			return VIRTIO_BLK_S_UNSUPP;
+		used_len = min(VIRTIO_BLK_ID_BYTES, task->data_len);
+		vhost_strcpy_pad(task->iovs[0].iov_base,
+				 bdev->product_name, used_len, ' ');
+		break;
+	default:
+		fprintf(stderr, "unsupported cmd\n");
+		return VIRTIO_BLK_S_UNSUPP;
+	}
+
+	return VIRTIO_BLK_S_OK;
+}
diff --git a/examples/vhost_blk/blk_spec.h b/examples/vhost_blk/blk_spec.h
new file mode 100644
index 000000000..5875e2f86
--- /dev/null
+++ b/examples/vhost_blk/blk_spec.h
@@ -0,0 +1,95 @@
+/* SPDX-License-Identifier: BSD-3-Clause
+ * Copyright(c) 2019 Intel Corporation
+ */
+
+#ifndef _BLK_SPEC_H
+#define _BLK_SPEC_H
+
+#include <stdint.h>
+
+#ifndef VHOST_USER_MEMORY_MAX_NREGIONS
+#define VHOST_USER_MEMORY_MAX_NREGIONS		8
+#endif
+
+#ifndef VHOST_USER_MAX_CONFIG_SIZE
+#define VHOST_USER_MAX_CONFIG_SIZE		256
+#endif
+
+#ifndef VHOST_USER_PROTOCOL_F_CONFIG
+#define VHOST_USER_PROTOCOL_F_CONFIG		9
+#endif
+
+#ifndef VHOST_USER_PROTOCOL_F_INFLIGHT_SHMFD
+#define VHOST_USER_PROTOCOL_F_INFLIGHT_SHMFD	12
+#endif
+
+#define VIRTIO_BLK_ID_BYTES	20	/* ID string length */
+
+#define VIRTIO_BLK_T_IN			0
+#define VIRTIO_BLK_T_OUT		1
+#define VIRTIO_BLK_T_FLUSH		4
+#define VIRTIO_BLK_T_GET_ID		8
+#define VIRTIO_BLK_T_DISCARD		11
+#define VIRTIO_BLK_T_WRITE_ZEROES	13
+
+#define VIRTIO_BLK_S_OK			0
+#define VIRTIO_BLK_S_IOERR		1
+#define VIRTIO_BLK_S_UNSUPP		2
+
+enum vhost_user_request {
+	VHOST_USER_NONE = 0,
+	VHOST_USER_GET_FEATURES = 1,
+	VHOST_USER_SET_FEATURES = 2,
+	VHOST_USER_SET_OWNER = 3,
+	VHOST_USER_RESET_OWNER = 4,
+	VHOST_USER_SET_MEM_TABLE = 5,
+	VHOST_USER_SET_LOG_BASE = 6,
+	VHOST_USER_SET_LOG_FD = 7,
+	VHOST_USER_SET_VRING_NUM = 8,
+	VHOST_USER_SET_VRING_ADDR = 9,
+	VHOST_USER_SET_VRING_BASE = 10,
+	VHOST_USER_GET_VRING_BASE = 11,
+	VHOST_USER_SET_VRING_KICK = 12,
+	VHOST_USER_SET_VRING_CALL = 13,
+	VHOST_USER_SET_VRING_ERR = 14,
+	VHOST_USER_GET_PROTOCOL_FEATURES = 15,
+	VHOST_USER_SET_PROTOCOL_FEATURES = 16,
+	VHOST_USER_GET_QUEUE_NUM = 17,
+	VHOST_USER_SET_VRING_ENABLE = 18,
+	VHOST_USER_MAX
+};
+
+/** Get/set config msg payload */
+struct vhost_user_config {
+	uint32_t offset;
+	uint32_t size;
+	uint32_t flags;
+	uint8_t region[VHOST_USER_MAX_CONFIG_SIZE];
+};
+
+/** Fixed-size vhost_memory struct */
+struct vhost_memory_padded {
+	uint32_t nregions;
+	uint32_t padding;
+	struct vhost_memory_region regions[VHOST_USER_MEMORY_MAX_NREGIONS];
+};
+
+struct vhost_user_msg {
+	enum vhost_user_request request;
+
+#define VHOST_USER_VERSION_MASK     0x3
+#define VHOST_USER_REPLY_MASK       (0x1 << 2)
+	uint32_t flags;
+	uint32_t size; /**< the following payload size */
+	union {
+#define VHOST_USER_VRING_IDX_MASK   0xff
+#define VHOST_USER_VRING_NOFD_MASK  (0x1 << 8)
+		uint64_t u64;
+		struct vhost_vring_state state;
+		struct vhost_vring_addr addr;
+		struct vhost_memory_padded memory;
+		struct vhost_user_config cfg;
+	} payload;
+} __attribute((packed));
+
+#endif
diff --git a/examples/vhost_blk/meson.build b/examples/vhost_blk/meson.build
new file mode 100644
index 000000000..028aa4f62
--- /dev/null
+++ b/examples/vhost_blk/meson.build
@@ -0,0 +1,20 @@
+# SPDX-License-Identifier: BSD-3-Clause
+# Copyright(c) 2017 Intel Corporation
+
+# meson file, for building this example as part of a main DPDK build.
+#
+# To build this example as a standalone application with an already-installed
+# DPDK instance, use 'make'
+
+if not is_linux
+	build = false
+endif
+
+if not cc.has_header('linux/virtio_blk.h')
+	build = false
+endif
+
+deps += 'vhost'
+sources = files(
+	'blk.c', 'vhost_blk.c', 'vhost_blk_compat.c'
+)
diff --git a/examples/vhost_blk/vhost_blk.c b/examples/vhost_blk/vhost_blk.c
new file mode 100644
index 000000000..a03b6036f
--- /dev/null
+++ b/examples/vhost_blk/vhost_blk.c
@@ -0,0 +1,1054 @@
+/* SPDX-License-Identifier: BSD-3-Clause
+ * Copyright(c) 2010-2017 Intel Corporation
+ */
+
+#include <stdint.h>
+#include <unistd.h>
+#include <stdbool.h>
+#include <signal.h>
+#include <assert.h>
+#include <semaphore.h>
+#include <linux/virtio_blk.h>
+#include <linux/virtio_ring.h>
+
+#include <rte_atomic.h>
+#include <rte_cycles.h>
+#include <rte_log.h>
+#include <rte_malloc.h>
+#include <rte_vhost.h>
+
+#include "vhost_blk.h"
+#include "blk_spec.h"
+
+#define VIRTQ_DESC_F_NEXT 1
+#define VIRTQ_DESC_F_AVAIL (1 << 7)
+#define VIRTQ_DESC_F_USED (1 << 15)
+
+#define VHOST_BLK_FEATURES ((1ULL << VIRTIO_F_RING_PACKED) | \
+			    (1ULL << VIRTIO_F_VERSION_1) |\
+			    (1ULL << VIRTIO_F_NOTIFY_ON_EMPTY) | \
+			    (1ULL << VHOST_USER_F_PROTOCOL_FEATURES))
+
+/* Path to folder where character device will be created. Can be set by user. */
+static char dev_pathname[PATH_MAX] = "";
+static sem_t exit_sem;
+
+struct vhost_blk_ctrlr *
+vhost_blk_ctrlr_find(const char *ctrlr_name)
+{
+	/* currently we only support 1 socket file fd */
+	return g_vhost_ctrlr;
+}
+
+static uint64_t gpa_to_vva(int vid, uint64_t gpa, uint64_t *len)
+{
+	char path[PATH_MAX];
+	struct vhost_blk_ctrlr *ctrlr;
+	int ret = 0;
+
+	ret = rte_vhost_get_ifname(vid, path, PATH_MAX);
+	if (ret) {
+		fprintf(stderr, "Cannot get socket name\n");
+		assert(ret != 0);
+	}
+
+	ctrlr = vhost_blk_ctrlr_find(path);
+	if (!ctrlr) {
+		fprintf(stderr, "Controller is not ready\n");
+		assert(ctrlr != NULL);
+	}
+
+	assert(ctrlr->mem != NULL);
+
+	return rte_vhost_va_from_guest_pa(ctrlr->mem, gpa, len);
+}
+
+static struct vring_packed_desc *
+descriptor_get_next_packed(struct rte_vhost_vring *vq,
+			     uint16_t *idx)
+{
+	if (vq->desc_packed[*idx & (vq->size - 1)].flags & VIRTQ_DESC_F_NEXT) {
+		*idx += 1;
+		return &vq->desc_packed[*idx & (vq->size - 1)];
+	}
+
+	return NULL;
+}
+
+static bool
+descriptor_has_next_packed(struct vring_packed_desc *cur_desc)
+{
+	return !!(cur_desc->flags & VRING_DESC_F_NEXT);
+}
+
+static bool
+descriptor_is_wr_packed(struct vring_packed_desc *cur_desc)
+{
+	return !!(cur_desc->flags & VRING_DESC_F_WRITE);
+}
+
+static struct inflight_desc_packed *
+inflight_desc_get_next(struct inflight_info_packed *inflight_packed,
+			       struct inflight_desc_packed *cur_desc)
+{
+	if (cur_desc->flags & VIRTQ_DESC_F_NEXT) {
+		return &inflight_packed->desc[cur_desc->next];
+	}
+
+	return NULL;
+}
+
+static bool
+inflight_desc_has_next(struct inflight_desc_packed *cur_desc)
+{
+	return !!(cur_desc->flags & VRING_DESC_F_NEXT);
+}
+
+static bool
+inflight_desc_is_wr(struct inflight_desc_packed *cur_desc)
+{
+	return !!(cur_desc->flags & VRING_DESC_F_WRITE);
+}
+
+static void
+inflight_process_payload_chain_packed(struct inflight_blk_task *task)
+{
+	void *data;
+	uint64_t chunck_len;
+
+	task->blk_task.iovs_cnt = 0;
+
+	do {
+		chunck_len = task->inflight_desc->len;
+		data = (void *)(uintptr_t)gpa_to_vva(task->blk_task.bdev->vid,
+						     task->inflight_desc->addr,
+						     &chunck_len);
+		if (!data || chunck_len != task->inflight_desc->len) {
+			fprintf(stderr, "failed to translate desc address.\n");
+			return;
+		}
+
+		task->blk_task.iovs[task->blk_task.iovs_cnt].iov_base = data;
+		task->blk_task.iovs[task->blk_task.iovs_cnt].iov_len =
+		task->inflight_desc->len;
+		task->blk_task.data_len += task->inflight_desc->len;
+		task->blk_task.iovs_cnt++;
+		task->inflight_desc = inflight_desc_get_next(task->inflight_packed,
+							     task->inflight_desc);
+	} while (inflight_desc_has_next(task->inflight_desc));
+
+	chunck_len = task->inflight_desc->len;
+	task->blk_task.status = (void *)(uintptr_t)gpa_to_vva(task->blk_task.bdev->vid,
+							      task->inflight_desc->addr,
+							      &chunck_len);
+	if (!task->blk_task.status || chunck_len != task->inflight_desc->len)
+		fprintf(stderr, "failed to translate desc address.\n");
+}
+
+static void
+inflight_submit_completion_packed(struct inflight_blk_task *task,
+					      uint32_t q_idx, uint16_t *used_id,
+					      bool *used_wrap_counter)
+{
+	struct vhost_blk_ctrlr *ctrlr;
+	struct rte_vhost_vring *vq;
+	struct vring_packed_desc *desc;
+	uint16_t flags;
+	uint16_t entry_num;
+	int ret;
+
+	ctrlr = vhost_blk_ctrlr_find(dev_pathname);
+	vq = task->blk_task.vq;
+
+	ret = rte_vhost_set_last_inflight_io_packed(ctrlr->bdev->vid, q_idx,
+						    task->blk_task.head_idx);
+	if (ret != 0)
+		fprintf(stderr, "fail to set last inflight io\n");
+
+	desc = &vq->desc_packed[*used_id];
+	desc->id = task->blk_task.buffer_id;
+	rte_compiler_barrier();
+	if (*used_wrap_counter) {
+		desc->flags = desc->flags | VIRTQ_DESC_F_AVAIL |
+			      VIRTQ_DESC_F_USED;
+	} else {
+		desc->flags = desc->flags & ~( VIRTQ_DESC_F_AVAIL |
+			      VIRTQ_DESC_F_USED);
+	}
+	rte_compiler_barrier();
+
+	*used_id += task->blk_task.iovs_cnt + 2;
+	if (*used_id > vq->size) {
+		*used_id &= vq->size - 1;
+		*used_wrap_counter = !(*used_wrap_counter);
+	}
+
+	ret = rte_vhost_clr_inflight_desc_packed(ctrlr->bdev->vid, q_idx,
+						 task->blk_task.head_idx);
+	if (ret != 0)
+		fprintf(stderr, "fail to clear inflight io\n");
+
+	/* Send an interrupt back to the guest VM so that it knows
+	 * a completion is ready to be processed.
+	 */
+	rte_vhost_vring_call(task->blk_task.bdev->vid, q_idx);
+}
+
+static void
+submit_completion_packed(struct vhost_blk_task *task, uint32_t q_idx,
+				  uint16_t *used_id, bool *used_wrap_counter)
+{
+	struct vhost_blk_ctrlr *ctrlr;
+	struct rte_vhost_vring *vq;
+	struct vring_packed_desc *desc;
+	uint16_t entry_num;
+	int ret;
+
+	ctrlr = vhost_blk_ctrlr_find(dev_pathname);
+	vq = task->vq;;
+
+	ret = rte_vhost_set_last_inflight_io_packed(ctrlr->bdev->vid, q_idx,
+						    task->inflight_idx);
+	if (ret != 0)
+		fprintf(stderr, "fail to set last inflight io\n");
+
+
+	desc = &vq->desc_packed[*used_id];
+	desc->id = task->buffer_id;
+	rte_compiler_barrier();
+	if (*used_wrap_counter) {
+		desc->flags = desc->flags | VIRTQ_DESC_F_AVAIL |
+			      VIRTQ_DESC_F_USED;
+	} else {
+		desc->flags = desc->flags & ~( VIRTQ_DESC_F_AVAIL |
+			      VIRTQ_DESC_F_USED);
+	}
+	rte_compiler_barrier();
+
+	*used_id += task->iovs_cnt + 2;
+	if (*used_id >= vq->size) {
+		*used_id &= vq->size - 1;
+		*used_wrap_counter = !(*used_wrap_counter);
+	}
+
+	ret = rte_vhost_clr_inflight_desc_packed(ctrlr->bdev->vid, q_idx,
+						 task->inflight_idx);
+	if (ret != 0)
+		fprintf(stderr, "fail to clear inflight io\n");
+
+	/* Send an interrupt back to the guest VM so that it knows
+	 * a completion is ready to be processed.
+	 */
+	rte_vhost_vring_call(task->bdev->vid, q_idx);
+}
+
+static void
+vhost_process_payload_chain_packed(struct vhost_blk_task *task, uint16_t *idx)
+{
+	void *data;
+	uint64_t chunck_len;
+
+	task->iovs_cnt = 0;
+
+	do {
+		chunck_len = task->desc_packed->len;
+		data = (void *)(uintptr_t)gpa_to_vva(task->bdev->vid,
+						     task->desc_packed->addr,
+							 &chunck_len);
+		if (!data || chunck_len != task->desc_packed->len) {
+			fprintf(stderr, "failed to translate desc address.\n");
+			return;
+		}
+
+		task->iovs[task->iovs_cnt].iov_base = data;
+		task->iovs[task->iovs_cnt].iov_len = task->desc_packed->len;
+		task->data_len += task->desc_packed->len;
+		task->iovs_cnt++;
+		task->desc_packed = descriptor_get_next_packed(task->vq, idx);
+	} while (descriptor_has_next_packed(task->desc_packed));
+
+	task->last_idx = *idx & (task->vq->size - 1);
+	chunck_len = task->desc_packed->len;
+	task->status = (void *)(uintptr_t)gpa_to_vva(task->bdev->vid,
+						   task->desc_packed->addr,
+						   &chunck_len);
+	if (!task->status || chunck_len != task->desc_packed->len)
+		fprintf(stderr, "failed to translate desc address.\n");
+}
+
+
+static int
+descriptor_is_available(struct rte_vhost_vring *vring, uint16_t idx,
+					bool avail_wrap_counter)
+{
+	uint16_t flags = vring->desc_packed[idx].flags;
+
+	return ((!!(flags & VIRTQ_DESC_F_AVAIL) == avail_wrap_counter) &&
+		(!!(flags & VIRTQ_DESC_F_USED) != avail_wrap_counter));
+}
+
+static int
+descriptor_is_used(struct rte_vhost_vring *vring, uint16_t idx,
+					bool used_wrap_counter)
+{
+	uint16_t flags = vring->desc_packed[idx].flags;
+
+	return ((!!(flags & VIRTQ_DESC_F_AVAIL) == used_wrap_counter) &&
+		(!!(flags & VIRTQ_DESC_F_USED) == used_wrap_counter));
+}
+
+static void
+process_requestq_packed(struct vhost_blk_ctrlr *ctrlr, uint32_t q_idx)
+{
+	bool avail_wrap_counter, used_wrap_counter;
+	uint16_t avail_idx, used_idx;
+	int ret;
+	uint64_t chunck_len;
+	struct vhost_blk_queue *blk_vq;
+	struct rte_vhost_vring *vq;
+	struct vhost_blk_task *task;
+
+	blk_vq = &ctrlr->bdev->queues[q_idx];
+	vq = &blk_vq->vq;
+
+	avail_idx = blk_vq->last_avail_idx;
+	avail_wrap_counter = blk_vq->avail_wrap_counter;
+	used_idx = blk_vq->last_used_idx;
+	used_wrap_counter = blk_vq->used_wrap_counter;
+
+	task = rte_zmalloc(NULL, sizeof(*task), 0);
+	assert(task != NULL);
+	task->vq = vq;
+	task->bdev = ctrlr->bdev;
+
+	while (descriptor_is_available(vq, avail_idx, avail_wrap_counter)) {
+		task->head_idx = avail_idx;
+		task->desc_packed = &task->vq->desc_packed[task->head_idx];
+		task->iovs_cnt = 0;
+		task->data_len = 0;
+		task->req = NULL;
+		task->status = NULL;
+
+		/* does not support indirect descriptors */
+		assert((task->desc_packed->flags & VRING_DESC_F_INDIRECT) == 0);
+
+		chunck_len = task->desc_packed->len;
+		task->req = (void *)(uintptr_t)gpa_to_vva(task->bdev->vid,
+							  task->desc_packed->addr,
+							  &chunck_len);
+		if (!task->req || chunck_len != task->desc_packed->len) {
+			fprintf(stderr, "failed to translate desc address.\n");
+			rte_free(task);
+			return;
+		}
+
+		task->desc_packed = descriptor_get_next_packed(task->vq, &avail_idx);
+		assert(task->desc_packed != NULL);
+		if (!descriptor_has_next_packed(task->desc_packed)) {
+			task->dxfer_dir = BLK_DIR_NONE;
+			task->last_idx = avail_idx & (vq->size - 1);
+			chunck_len = task->desc_packed->len;
+			task->status = (void *)(uintptr_t)
+					      gpa_to_vva(task->bdev->vid,
+							 task->desc_packed->addr,
+							 &chunck_len);
+			if (!task->status || chunck_len != task->desc_packed->len) {
+				fprintf(stderr, "failed to translate desc address.\n");
+				rte_free(task);
+				return;
+			}
+		} else {
+			task->readtype = descriptor_is_wr_packed(task->desc_packed);
+			vhost_process_payload_chain_packed(task, &avail_idx);
+		}
+		task->buffer_id = vq->desc_packed[task->last_idx].id;
+		rte_vhost_set_inflight_desc_packed(ctrlr->bdev->vid, q_idx, 
+						   task->head_idx,
+						   task->last_idx,
+						   &task->inflight_idx);
+
+		if (++avail_idx >= vq->size) {
+			avail_idx &= vq->size - 1;
+			avail_wrap_counter = !avail_wrap_counter;
+		}
+		blk_vq->last_avail_idx = avail_idx;
+		blk_vq->avail_wrap_counter = avail_wrap_counter;
+
+		ret = vhost_bdev_process_blk_commands(ctrlr->bdev, task);
+		if (ret) {
+			/* invalid response */
+			*task->status = VIRTIO_BLK_S_IOERR;
+		} else {
+			/* successfully */
+			*task->status = VIRTIO_BLK_S_OK;
+		}
+
+		submit_completion_packed(task, q_idx, &used_idx, &used_wrap_counter);
+		blk_vq->last_used_idx = used_idx;
+		blk_vq->used_wrap_counter = used_wrap_counter;
+	}
+
+	rte_free(task);
+}
+
+static void
+submit_inflight_vq_packed(struct vhost_blk_ctrlr *ctrlr, uint16_t q_idx)
+{
+	bool used_wrap_counter;
+	int i, ret;
+	uint16_t used_idx;
+	uint64_t chunck_len;
+	struct vhost_blk_queue *blk_vq;
+	struct rte_vhost_ring_inflight *inflight_vq;
+	struct rte_vhost_vring *vq;
+	struct inflight_blk_task *task;
+
+	blk_vq = &ctrlr->bdev->queues[q_idx];
+	inflight_vq = &blk_vq->inflight_vq;
+	used_idx = inflight_vq->inflight_packed->old_used_idx;
+	used_wrap_counter = inflight_vq->inflight_packed->old_used_wrap_counter;
+
+	task = rte_malloc(NULL, sizeof(*task), 0);
+	if (task) {
+		fprintf(stderr, "fail to allocate memory\n");
+		return;
+	}
+	task->blk_task.vq = vq;
+	task->blk_task.bdev = ctrlr->bdev;
+
+	for (i = 0; i < inflight_vq->resubmit_inflight->resubmit_num; i++) {
+		task->blk_task.head_idx =
+		inflight_vq->resubmit_inflight->resubmit_list[i].index;
+		task->inflight_desc =
+		&inflight_vq->inflight_packed->desc[task->blk_task.head_idx];
+		task->blk_task.iovs_cnt = 0;
+		task->blk_task.data_len = 0;
+		task->blk_task.req = NULL;
+		task->blk_task.status = NULL;
+
+		/* does not support indirect descriptors */
+		assert((task->inflight_desc->flags & VRING_DESC_F_INDIRECT) == 0);
+
+		chunck_len = task->inflight_desc->len;
+		task->blk_task.req = (void *)(uintptr_t)gpa_to_vva(task->blk_task.bdev->vid,
+								task->inflight_desc->addr,
+								&chunck_len);
+		if (!task->blk_task.req || chunck_len != task->inflight_desc->len) {
+			fprintf(stderr, "failed to translate desc address.\n");
+			rte_free(task);
+			return;
+		}
+
+		task->inflight_desc = inflight_desc_get_next(task->inflight_packed,
+							     task->inflight_desc);
+		if (!inflight_desc_has_next(task->inflight_desc)) {
+			task->blk_task.dxfer_dir = BLK_DIR_NONE;
+			chunck_len = task->inflight_desc->len;
+			task->blk_task.status = (void *)(uintptr_t)
+						gpa_to_vva(task->blk_task.bdev->vid,
+							   task->inflight_desc->addr,
+							   &chunck_len);
+			if (!task->blk_task.status ||
+			    chunck_len != task->inflight_desc->len) {
+				fprintf(stderr, "failed to translate desc address.\n");
+				rte_free(task);
+				return;
+			}
+		} else {
+			task->blk_task.readtype =
+			inflight_desc_is_wr(task->inflight_desc);
+			inflight_process_payload_chain_packed(task);
+		}
+
+		ret = vhost_bdev_process_blk_commands(ctrlr->bdev, &task->blk_task);
+		if (ret) {
+			/* invalid response */
+			*task->blk_task.status = VIRTIO_BLK_S_IOERR;
+		} else {
+			/* successfully */
+			*task->blk_task.status = VIRTIO_BLK_S_OK;
+		}
+
+		inflight_submit_completion_packed(task, q_idx, &used_idx, 
+		&used_wrap_counter);
+
+		blk_vq->last_used_idx = used_idx;
+		blk_vq->used_wrap_counter = used_wrap_counter;
+	}
+
+	rte_free(task);
+}
+
+static struct vring_desc *
+descriptor_get_next_split(struct vring_desc *vq_desc,
+				   struct vring_desc *cur_desc)
+{
+	return &vq_desc[cur_desc->next];
+}
+
+static bool
+descriptor_has_next_split(struct vring_desc *cur_desc)
+{
+	return !!(cur_desc->flags & VRING_DESC_F_NEXT);
+}
+
+static bool
+descriptor_is_wr_split(struct vring_desc *cur_desc)
+{
+	return !!(cur_desc->flags & VRING_DESC_F_WRITE);
+}
+
+static void
+vhost_process_payload_chain_split(struct vhost_blk_task *task)
+{
+	void *data;
+	uint64_t chunck_len;
+
+	task->iovs_cnt = 0;
+
+	do {
+		chunck_len = task->desc_split->len;
+		data = (void *)(uintptr_t)gpa_to_vva(task->bdev->vid,
+						     task->desc_split->addr,
+						     &chunck_len);
+		if (!data || chunck_len != task->desc_split->len) {
+			fprintf(stderr, "failed to translate desc address.\n");
+			return;
+		}
+
+		task->iovs[task->iovs_cnt].iov_base = data;
+		task->iovs[task->iovs_cnt].iov_len = task->desc_split->len;
+		task->data_len += task->desc_split->len;
+		task->iovs_cnt++;
+		task->desc_split =
+		descriptor_get_next_split(task->vq->desc, task->desc_split);
+	} while (descriptor_has_next_split(task->desc_split));
+
+	chunck_len = task->desc_split->len;
+	task->status = (void *)(uintptr_t)gpa_to_vva(task->bdev->vid,
+						     task->desc_split->addr,
+						     &chunck_len);
+	if (!task->status || chunck_len != task->desc_split->len)
+		fprintf(stderr, "failed to translate desc address.\n");
+}
+
+static void
+submit_completion_split(struct vhost_blk_task *task, uint32_t vid, uint32_t q_idx)
+{
+	struct rte_vhost_vring *vq;
+	struct vring_used *used;
+
+	vq = task->vq;
+	used = vq->used;
+
+	rte_vhost_set_last_inflight_io_split(vid, q_idx, task->req_idx);
+
+	/* Fill out the next entry in the "used" ring.  id = the
+	 * index of the descriptor that contained the blk request.
+	 * len = the total amount of data transferred for the blk
+	 * request. We must report the correct len, for variable
+	 * length blk CDBs, where we may return less data than
+	 * allocated by the guest VM.
+	 */
+	used->ring[used->idx & (vq->size - 1)].id = task->req_idx;
+	used->ring[used->idx & (vq->size - 1)].len = task->data_len;
+	rte_compiler_barrier();
+	used->idx++;
+	rte_compiler_barrier();
+
+	rte_vhost_clr_inflight_desc_split(vid, q_idx, used->idx, task->req_idx);
+
+	/* Send an interrupt back to the guest VM so that it knows
+	 * a completion is ready to be processed.
+	 */
+	rte_vhost_vring_call(task->bdev->vid, q_idx);
+}
+
+static void
+submit_inflight_vq_split(struct vhost_blk_ctrlr *ctrlr, uint32_t q_idx)
+{
+	struct vhost_blk_queue *blk_vq;
+	struct rte_vhost_ring_inflight *inflight_vq;
+	struct rte_vhost_resubmit_info *resubmit_inflight;
+	struct rte_vhost_resubmit_desc *resubmit_list;
+	struct vhost_blk_task *task;
+	int i, req_idx;
+	uint64_t chunck_len;
+	int ret;
+
+	blk_vq = &ctrlr->bdev->queues[q_idx];
+	inflight_vq = &blk_vq->inflight_vq;
+	resubmit_inflight = inflight_vq->resubmit_inflight;
+	resubmit_list = resubmit_inflight->resubmit_list;
+
+	task = rte_zmalloc(NULL, sizeof(*task), 0);
+	assert(task != NULL);
+
+	task->ctrlr = ctrlr;
+	task->bdev = ctrlr->bdev;
+	task->vq = &blk_vq->vq;
+
+	for (i = 0; i < resubmit_inflight->resubmit_num; i++) {
+		req_idx = resubmit_list[i].index;
+		task->req_idx = req_idx;
+		task->desc_split = &task->vq->desc[task->req_idx];
+		task->iovs_cnt = 0;
+		task->data_len = 0;
+		task->req = NULL;
+		task->desc_split = NULL;
+		task->status = NULL;
+
+		/* does not support indirect descriptors */
+		assert((task->desc_split->flags & VRING_DESC_F_INDIRECT) == 0);
+
+		chunck_len = task->desc_split->len;
+		task->req = (void *)(uintptr_t)gpa_to_vva(task->bdev->vid,
+							  task->desc_split->addr,
+							  &chunck_len);
+		if (!task->req || chunck_len != task->desc_split->len) {
+			fprintf(stderr, "failed to translate desc address.\n");
+			rte_free(task);
+			return;
+		}
+
+		task->desc_split = descriptor_get_next_split(task->vq->desc,
+							     task->desc_split);
+		if (!descriptor_has_next_split(task->desc_split)) {
+			task->dxfer_dir = BLK_DIR_NONE;
+			chunck_len = task->desc_split->len;
+			task->status = (void *)(uintptr_t)
+				       gpa_to_vva(task->bdev->vid,
+						  task->desc_split->addr,
+						  &chunck_len);
+			if (!task->status || chunck_len != task->desc_split->len) {
+				fprintf(stderr, "failed to translate desc address.\n");
+				rte_free(task);
+				return;
+			}
+		} else {
+			task->readtype = descriptor_is_wr_split(task->desc_split);
+			vhost_process_payload_chain_split(task);
+		}
+
+		ret = vhost_bdev_process_blk_commands(ctrlr->bdev, task);
+		if (ret) {
+			/* invalid response */
+			*task->status = VIRTIO_BLK_S_IOERR;
+		} else {
+			/* successfully */
+			*task->status = VIRTIO_BLK_S_OK;
+		}
+		submit_completion_split(task, ctrlr->bdev->vid, q_idx);
+	}
+
+	rte_free(task);
+}
+
+static void
+process_requestq_split(struct vhost_blk_ctrlr *ctrlr, uint32_t q_idx)
+{
+	int ret;
+	int req_idx;
+	uint16_t last_idx;
+	uint64_t chunck_len;
+	struct vhost_blk_queue *blk_vq;
+	struct rte_vhost_vring *vq;
+	struct vhost_blk_task *task;
+
+	blk_vq = &ctrlr->bdev->queues[q_idx];
+	vq = &blk_vq->vq;
+
+	task = rte_zmalloc(NULL, sizeof(*task), 0);
+	assert(task != NULL);
+	task->ctrlr = ctrlr;
+	task->bdev = ctrlr->bdev;
+	task->vq = vq;
+
+	while (vq->avail->idx != blk_vq->last_avail_idx) {
+		last_idx = blk_vq->last_avail_idx & (vq->size - 1);
+		req_idx = vq->avail->ring[last_idx];
+		task->req_idx = req_idx;
+		task->desc_split = &task->vq->desc[task->req_idx];
+		task->iovs_cnt = 0;
+		task->data_len = 0;
+		task->req = NULL;
+		task->status = NULL;
+
+		rte_vhost_set_inflight_desc_split(ctrlr->bdev->vid, q_idx, task->req_idx);
+
+		/* does not support indirect descriptors */
+		assert((task->desc_split->flags & VRING_DESC_F_INDIRECT) == 0);
+
+		chunck_len = task->desc_split->len;
+		task->req = (void *)(uintptr_t)gpa_to_vva(task->bdev->vid,
+							  task->desc_split->addr,
+							  &chunck_len);
+		if (!task->req || chunck_len != task->desc_split->len) {
+			fprintf(stderr, "failed to translate desc address.\n");
+			rte_free(task);
+			return;
+		}
+
+		task->desc_split = descriptor_get_next_split(task->vq->desc, task->desc_split);
+		if (!descriptor_has_next_split(task->desc_split)) {
+			task->dxfer_dir = BLK_DIR_NONE;
+			chunck_len = task->desc_split->len;
+			task->status = (void *)(uintptr_t)
+					      gpa_to_vva(task->bdev->vid,
+							 task->desc_split->addr,
+							 &chunck_len);
+			if (!task->status || chunck_len != task->desc_split->len) {
+				fprintf(stderr, "failed to translate desc address.\n");
+				rte_free(task);
+				return;
+			}
+		} else {
+			task->readtype = descriptor_is_wr_split(task->desc_split);
+			vhost_process_payload_chain_split(task);
+		}
+		blk_vq->last_avail_idx++;
+
+		ret = vhost_bdev_process_blk_commands(ctrlr->bdev, task);
+		if (ret) {
+			/* invalid response */
+			*task->status = VIRTIO_BLK_S_IOERR;
+		} else {
+			/* successfully */
+			*task->status = VIRTIO_BLK_S_OK;
+		}
+
+		submit_completion_split(task, ctrlr->bdev->vid, q_idx);
+	}
+
+	rte_free(task);
+}
+
+static void *
+ctrlr_worker(void *arg)
+{
+	struct vhost_blk_ctrlr *ctrlr = (struct vhost_blk_ctrlr *)arg;
+	struct vhost_blk_queue *blk_vq;
+	struct rte_vhost_ring_inflight *inflight_vq;
+	cpu_set_t cpuset;
+	pthread_t thread;
+	int i, ret;
+
+	fprintf(stdout, "Ctrlr Worker Thread start\n");
+
+	if (ctrlr == NULL || ctrlr->bdev == NULL) {
+		fprintf(stderr, "%s: Error, invalid argument passed to worker thread\n",
+				__func__);
+		exit(0);
+	}
+
+	thread = pthread_self();
+	CPU_ZERO(&cpuset);
+	CPU_SET(0, &cpuset);
+	pthread_setaffinity_np(thread, sizeof(cpu_set_t), &cpuset);
+
+	for (i = 0; i < NUM_OF_BLK_QUEUES; i++) {
+		blk_vq = &ctrlr->bdev->queues[i];
+		inflight_vq = &blk_vq->inflight_vq;
+		if (inflight_vq->resubmit_inflight != NULL &&
+		    inflight_vq->resubmit_inflight->resubmit_num != 0) {
+			if (ctrlr->packed)
+				submit_inflight_vq_packed(ctrlr, i);
+			else
+				submit_inflight_vq_split(ctrlr, i);
+		    }
+	}
+
+	while (!g_should_stop && ctrlr->bdev != NULL) {
+		for (i = 0; i < NUM_OF_BLK_QUEUES; i++) {
+			if (ctrlr->packed) 
+				process_requestq_packed(ctrlr, i);
+			else
+				process_requestq_split(ctrlr, i);
+		}
+	}
+
+	fprintf(stdout, "Ctrlr Worker Thread Exiting\n");
+	sem_post(&exit_sem);
+	return NULL;
+}
+
+static int
+new_device(int vid)
+{
+	char path[PATH_MAX];
+	struct vhost_blk_ctrlr *ctrlr;
+	struct vhost_blk_queue *blk_vq;
+	struct rte_vhost_vring *vq;
+	pthread_t tid;
+	int i, ret;
+	uint64_t features;
+
+	ctrlr = vhost_blk_ctrlr_find(path);
+	if (!ctrlr) {
+		fprintf(stderr, "Controller is not ready\n");
+		return -1;
+	}
+
+	if (ctrlr->started)
+		return 0;
+
+	ctrlr->bdev->vid = vid;
+	ctrlr->packed = rte_vhost_vq_is_packed(vid);
+
+	ret = rte_vhost_get_mem_table(vid, &ctrlr->mem);
+	if (ret)
+		fprintf(stderr, "Get Controller memory region failed\n");
+	assert(ctrlr->mem != NULL);
+
+	/* Disable Notifications and init last idx */
+	for (i = 0; i < NUM_OF_BLK_QUEUES; i++) {
+		rte_vhost_enable_guest_notification(vid, i, 0);
+
+		blk_vq = &ctrlr->bdev->queues[i];
+		vq = &blk_vq->vq;
+		ret = rte_vhost_get_vring_base(ctrlr->bdev->vid, i,
+					       &blk_vq->last_avail_idx,
+					       &blk_vq->last_used_idx);
+		assert(ret == 0);
+		if (ctrlr->packed) {
+			ret = rte_vhost_get_vring_base_counter(ctrlr->bdev->vid, i,
+							&blk_vq->avail_wrap_counter,
+							&blk_vq->used_wrap_counter);
+			assert(ret == 0);
+		}
+
+		ret = rte_vhost_get_vhost_vring(ctrlr->bdev->vid, i, vq);
+		assert(ret == 0);
+
+		ret = rte_vhost_get_vhost_ring_inflight(ctrlr->bdev->vid, i,
+							&blk_vq->inflight_vq);
+		assert(ret == 0);
+
+		if (ctrlr->packed) {
+			/* for the reconnection */
+			ret = rte_vhost_get_vring_base_from_inflight(ctrlr->bdev->vid, i,
+								&blk_vq->last_avail_idx,
+								&blk_vq->last_used_idx);
+			assert(ret == 0);
+			rte_vhost_get_vring_base_counter_from_inflight(ctrlr->bdev->vid, i,
+							&blk_vq->avail_wrap_counter,
+							&blk_vq->used_wrap_counter);
+			assert(ret == 0);
+		}
+	}
+
+	/* start polling vring */
+	g_should_stop = 0;
+	fprintf(stdout, "New Device %s, Device ID %d\n", path, vid);
+	if (pthread_create(&tid, NULL, &ctrlr_worker, ctrlr) < 0) {
+		fprintf(stderr, "Worker Thread Started Failed\n");
+		return -1;
+	}
+
+	/* device has been started */
+	ctrlr->started = 1;
+	pthread_detach(tid);
+	return 0;
+}
+
+static void
+destroy_device(int vid)
+{
+	char path[PATH_MAX];
+	struct vhost_blk_ctrlr *ctrlr;
+	struct vhost_blk_queue *blk_vq;
+	struct rte_vhost_vring *vq;
+	int i, ret;
+
+	ret = rte_vhost_get_ifname(vid, path, PATH_MAX);
+	if (ret) {
+		fprintf(stderr, "Destroy Ctrlr Failed\n");
+		return;
+	}
+	fprintf(stdout, "Destroy %s Device ID %d\n", path, vid);
+	ctrlr = vhost_blk_ctrlr_find(path);
+	if (!ctrlr) {
+		fprintf(stderr, "Destroy Ctrlr Failed\n");
+		return;
+	}
+
+	if (!ctrlr->started)
+		return;
+
+	g_should_stop = 1;
+
+	for (i = 0; i < NUM_OF_BLK_QUEUES; i++) {
+		blk_vq = &ctrlr->bdev->queues[i];
+		rte_vhost_set_vring_base(ctrlr->bdev->vid, i,
+					 blk_vq->last_avail_idx, blk_vq->last_used_idx);
+		if (ctrlr->packed) {
+			fprintf(stderr, "destroy counter avail is %d and used is %d\n",
+			blk_vq->avail_wrap_counter, blk_vq->used_wrap_counter);
+			rte_vhost_set_vring_base_counter(ctrlr->bdev->vid, i,
+							blk_vq->avail_wrap_counter,
+							blk_vq->used_wrap_counter);
+		}
+	}
+
+	free(ctrlr->mem);
+
+	ctrlr->started = 0;
+	sem_wait(&exit_sem);
+}
+
+static int
+new_connection(int vid)
+{
+	/* extend the proper features for block device */
+	vhost_session_install_rte_compat_hooks(vid);
+}
+
+struct vhost_device_ops vhost_blk_device_ops = {
+	.new_device =  new_device,
+	.destroy_device = destroy_device,
+	.new_connection = new_connection,
+};
+
+static struct vhost_block_dev *
+vhost_blk_bdev_construct(const char *bdev_name, const char *bdev_serial,
+			  uint32_t blk_size, uint64_t blk_cnt,
+			  bool wce_enable)
+{
+	struct vhost_block_dev *bdev;
+
+	bdev = rte_zmalloc(NULL, sizeof(*bdev), RTE_CACHE_LINE_SIZE);
+	if (!bdev)
+		return NULL;
+
+	strncpy(bdev->name, bdev_name, sizeof(bdev->name));
+	strncpy(bdev->product_name, bdev_serial, sizeof(bdev->product_name));
+	bdev->blocklen = blk_size;
+	bdev->blockcnt = blk_cnt;
+	bdev->write_cache = wce_enable;
+
+	fprintf(stdout, "blocklen=%d, blockcnt=%d\n", bdev->blocklen, bdev->blockcnt);
+
+	/* use memory as disk storage space */
+	bdev->data = rte_zmalloc(NULL, blk_cnt * blk_size, 0);
+	if (!bdev->data) {
+		fprintf(stderr, "no enough reseverd huge memory for disk\n");
+		free(bdev);
+		return NULL;
+	}
+
+	return bdev;
+}
+
+static struct vhost_blk_ctrlr *
+vhost_blk_ctrlr_construct(const char *ctrlr_name)
+{
+	int ret;
+	struct vhost_blk_ctrlr *ctrlr;
+	char *path;
+	char cwd[PATH_MAX];
+
+	/* always use current directory */
+	path = getcwd(cwd, PATH_MAX);
+	if (!path) {
+		fprintf(stderr, "Cannot get current working directory\n");
+		return NULL;
+	}
+	snprintf(dev_pathname, sizeof(dev_pathname), "%s/%s", path, ctrlr_name);
+
+	if (access(dev_pathname, F_OK) != -1) {
+		if (unlink(dev_pathname) != 0)
+			rte_exit(EXIT_FAILURE, "Cannot remove %s.\n",
+				 dev_pathname);
+	}
+
+	if (rte_vhost_driver_register(dev_pathname, 0) != 0) {
+		fprintf(stderr, "socket %s already exists\n", dev_pathname);
+		return NULL;
+	}
+
+	ret = rte_vhost_driver_set_features(dev_pathname, VHOST_BLK_FEATURES);
+	if (ret != 0) {
+		fprintf(stderr, "Set vhost driver features failed\n");
+		rte_vhost_driver_unregister(dev_pathname);
+		return NULL;
+	}
+
+	/* set proper features */
+	vhost_dev_install_rte_compat_hooks(dev_pathname);
+
+	ctrlr = rte_zmalloc(NULL, sizeof(*ctrlr), RTE_CACHE_LINE_SIZE);
+	if (!ctrlr) {
+		rte_vhost_driver_unregister(dev_pathname);
+		return NULL;
+	}
+
+	/* hardcoded block device information with 128MiB */
+	ctrlr->bdev = vhost_blk_bdev_construct("malloc0", "vhost_blk_malloc0",
+						4096, 32768, 0);
+	if (!ctrlr->bdev) {
+		rte_free(ctrlr);
+		rte_vhost_driver_unregister(dev_pathname);
+		return NULL;
+	}
+
+	rte_vhost_driver_callback_register(dev_pathname,
+					   &vhost_blk_device_ops);
+
+	return ctrlr;
+}
+
+static void
+signal_handler(__rte_unused int signum)
+{
+	struct vhost_blk_ctrlr *ctrlr;
+
+	if (access(dev_pathname, F_OK) == 0)
+		unlink(dev_pathname);
+
+	g_should_stop = 1;
+
+	ctrlr = vhost_blk_ctrlr_find(NULL);
+	if (ctrlr != NULL) {
+		fprintf(stderr, "never come in\n");
+		if (ctrlr->bdev != NULL) {
+			rte_free(ctrlr->bdev->data);
+			rte_free(ctrlr->bdev);
+		}
+		rte_free(ctrlr);
+	}
+
+	rte_vhost_driver_unregister(dev_pathname);
+	exit(0);
+}
+
+int main(int argc, char *argv[])
+{
+	int ret;
+
+	signal(SIGINT, signal_handler);
+
+	/* init EAL */
+	ret = rte_eal_init(argc, argv);
+	if (ret < 0)
+		rte_exit(EXIT_FAILURE, "Error with EAL initialization\n");
+
+	g_vhost_ctrlr = vhost_blk_ctrlr_construct("vhost.socket");
+	if (g_vhost_ctrlr == NULL) {
+		fprintf(stderr, "Construct vhost blk controller failed\n");
+		return 0;
+	}
+
+	if (sem_init(&exit_sem, 0, 0) < 0) {
+		fprintf(stderr, "Error init exit_sem\n");
+		return -1;
+	}
+
+	rte_vhost_driver_start(dev_pathname);
+
+	/* loop for exit the application */
+	while (1)
+		sleep(1);
+
+	return 0;
+}
+
diff --git a/examples/vhost_blk/vhost_blk.h b/examples/vhost_blk/vhost_blk.h
new file mode 100644
index 000000000..6f6d20398
--- /dev/null
+++ b/examples/vhost_blk/vhost_blk.h
@@ -0,0 +1,114 @@
+/* SPDX-License-Identifier: BSD-3-Clause
+ * Copyright(c) 2010-2017 Intel Corporation
+ */
+
+#ifndef _VHOST_BLK_H_
+#define _VHOST_BLK_H_
+
+#include <stdio.h>
+#include <sys/uio.h>
+#include <stdint.h>
+#include <linux/virtio_blk.h>
+#include <linux/virtio_ring.h>
+
+#include <rte_vhost.h>
+
+struct vhost_blk_queue {
+	struct rte_vhost_vring vq;
+	struct rte_vhost_ring_inflight inflight_vq;
+	uint16_t last_avail_idx;
+	uint16_t last_used_idx;
+	bool avail_wrap_counter;
+	bool used_wrap_counter;
+};
+
+#define NUM_OF_BLK_QUEUES 1
+
+#ifndef VIRTIO_F_RING_PACKED
+#define VIRTIO_F_RING_PACKED 34
+#endif
+
+#define min(a, b) (((a) < (b)) ? (a) : (b))
+
+struct vhost_block_dev {
+	/** ID for vhost library. */
+	int vid;
+	/** Queues for the block device */
+	struct vhost_blk_queue queues[NUM_OF_BLK_QUEUES];
+	/** Unique name for this block device. */
+	char name[64];
+
+	/** Unique product name for this kind of block device. */
+	char product_name[256];
+
+	/** Size in bytes of a logical block for the backend */
+	uint32_t blocklen;
+
+	/** Number of blocks */
+	uint64_t blockcnt;
+
+	/** write cache enabled, not used at the moment */
+	int write_cache;
+
+	/** use memory as disk storage space */
+	uint8_t *data;
+};
+
+struct vhost_blk_ctrlr {
+	uint8_t started;
+	uint8_t packed;
+	uint8_t need_restart;
+	/** Only support 1 LUN for the example */
+	struct vhost_block_dev *bdev;
+	/** VM memory region */
+	struct rte_vhost_memory *mem;
+} __rte_cache_aligned;
+
+#define VHOST_BLK_MAX_IOVS 128
+
+enum blk_data_dir {
+	BLK_DIR_NONE = 0,
+	BLK_DIR_TO_DEV = 1,
+	BLK_DIR_FROM_DEV = 2,
+};
+
+struct vhost_blk_task {
+	uint8_t readtype;
+	uint8_t req_idx;
+	uint16_t head_idx;
+	uint16_t last_idx;
+	uint16_t inflight_idx;
+	uint16_t buffer_id;
+	uint32_t dxfer_dir;
+	uint32_t data_len;
+	struct virtio_blk_outhdr *req;
+	volatile uint8_t *status;
+	struct iovec iovs[VHOST_BLK_MAX_IOVS];
+	uint32_t iovs_cnt;
+	struct vring_packed_desc *desc_packed;
+	struct vring_desc *desc_split;
+	struct rte_vhost_vring *vq;
+	struct vhost_block_dev *bdev;
+	struct vhost_blk_ctrlr *ctrlr;
+};
+
+struct inflight_blk_task {
+	struct vhost_blk_task blk_task;
+	struct inflight_desc_packed *inflight_desc;
+	struct inflight_info_packed *inflight_packed;
+};
+
+struct vhost_blk_ctrlr *g_vhost_ctrlr;
+struct vhost_device_ops vhost_blk_device_ops;
+int g_should_stop;
+
+int vhost_bdev_process_blk_commands(struct vhost_block_dev *bdev,
+				     struct vhost_blk_task *task);
+
+void vhost_session_install_rte_compat_hooks(uint32_t vid);
+
+void vhost_dev_install_rte_compat_hooks(const char *path);
+
+struct vhost_blk_ctrlr *vhost_blk_ctrlr_find(const char *ctrlr_name);
+
+#endif /* _VHOST_blk_H_ */
diff --git a/examples/vhost_blk/vhost_blk_compat.c b/examples/vhost_blk/vhost_blk_compat.c
new file mode 100644
index 000000000..405b091d7
--- /dev/null
+++ b/examples/vhost_blk/vhost_blk_compat.c
@@ -0,0 +1,193 @@
+/* SPDX-License-Identifier: BSD-3-Clause
+ * Copyright(c) 2010-2017 Intel Corporation
+ */
+
+#ifndef _VHOST_BLK_COMPAT_H_
+#define _VHOST_BLK_COMPAT_H_
+
+#include <sys/uio.h>
+#include <stdint.h>
+#include <linux/virtio_blk.h>
+#include <linux/virtio_ring.h>
+
+#include <rte_vhost.h>
+#include "vhost_blk.h"
+#include "blk_spec.h"
+
+#define VHOST_MAX_VQUEUES	256
+#define SPDK_VHOST_MAX_VQ_SIZE	1024
+
+#define VHOST_USER_GET_CONFIG 24
+#define VHOST_USER_SET_CONFIG 25
+
+static int
+vhost_blk_get_config(struct vhost_block_dev *bdev, uint8_t *config,
+			  uint32_t len)
+{
+	struct virtio_blk_config blkcfg;
+	uint32_t blk_size;
+	uint64_t blkcnt;
+
+	if (bdev == NULL) {
+		/* We can't just return -1 here as this GET_CONFIG message might
+		 * be caused by a QEMU VM reboot. Returning -1 will indicate an
+		 * error to QEMU, who might then decide to terminate itself.
+		 * We don't want that. A simple reboot shouldn't break the system.
+		 *
+		 * Presenting a block device with block size 0 and block count 0
+		 * doesn't cause any problems on QEMU side and the virtio-pci
+		 * device is even still available inside the VM, but there will
+		 * be no block device created for it - the kernel drivers will
+		 * silently reject it.
+		 */
+		blk_size = 0;
+		blkcnt = 0;
+	} else {
+		blk_size = bdev->blocklen;
+		blkcnt = bdev->blockcnt;
+	}
+
+	memset(&blkcfg, 0, sizeof(blkcfg));
+	blkcfg.blk_size = blk_size;
+	/* minimum I/O size in blocks */
+	blkcfg.min_io_size = 1;
+	/* expressed in 512 Bytes sectors */
+	blkcfg.capacity = (blkcnt * blk_size) / 512;
+	/* QEMU can overwrite this value when started */
+	blkcfg.num_queues = VHOST_MAX_VQUEUES;
+
+	fprintf(stdout, "block device:blk_size = %d, blkcnt = %d\n", blk_size, blkcnt);
+
+	memcpy(config, &blkcfg, min(len, sizeof(blkcfg)));
+
+	return 0;
+}
+
+static enum rte_vhost_msg_result
+extern_vhost_pre_msg_handler(int vid, void *_msg)
+{
+	char path[PATH_MAX];
+	struct vhost_blk_ctrlr *ctrlr;
+	struct vhost_user_msg *msg = _msg;
+	int ret;
+
+	ret = rte_vhost_get_ifname(vid, path, PATH_MAX);
+	if (ret) {
+		fprintf(stderr, "Cannot get socket name\n");
+		return -1;
+	}
+
+	ctrlr = vhost_blk_ctrlr_find(path);
+	if (!ctrlr) {
+		fprintf(stderr, "Controller is not ready\n");
+		return -1;
+	}
+
+	switch (msg->request) {
+	case VHOST_USER_GET_VRING_BASE:
+		if (!g_should_stop && ctrlr->started)
+			vhost_blk_device_ops.destroy_device(vid);
+		break;
+	case VHOST_USER_SET_VRING_BASE:
+	case VHOST_USER_SET_VRING_ADDR:
+	case VHOST_USER_SET_VRING_NUM:
+	case VHOST_USER_SET_VRING_KICK:
+		if (!g_should_stop && ctrlr->started)
+			vhost_blk_device_ops.destroy_device(vid);
+		break;
+	case VHOST_USER_SET_VRING_CALL:
+	case VHOST_USER_SET_MEM_TABLE:
+		if (!g_should_stop && ctrlr->started) {
+			vhost_blk_device_ops.destroy_device(vid);
+			ctrlr->need_restart = 1;
+		}
+		break;
+	case VHOST_USER_GET_CONFIG: {
+		int rc = 0;
+
+		rc = vhost_blk_get_config(ctrlr->bdev,
+					  msg->payload.cfg.region, msg->payload.cfg.size);
+		if (rc != 0)
+			msg->size = 0;
+
+		return RTE_VHOST_MSG_RESULT_REPLY;
+	}
+	case VHOST_USER_SET_CONFIG:
+	default:
+		break;
+	}
+
+	return RTE_VHOST_MSG_RESULT_NOT_HANDLED;
+}
+
+static enum rte_vhost_msg_result
+extern_vhost_post_msg_handler(int vid, void *_msg)
+{
+	char path[PATH_MAX];
+	struct vhost_blk_ctrlr *ctrlr;
+	struct vhost_user_msg *msg = _msg;
+	int ret;
+
+	ret = rte_vhost_get_ifname(vid, path, PATH_MAX);
+	if (ret) {
+		fprintf(stderr, "Cannot get socket name\n");
+		return -1;
+	}
+
+	ctrlr = vhost_blk_ctrlr_find(path);
+	if (!ctrlr) {
+		fprintf(stderr, "Controller is not ready\n");
+		return -1;
+	}
+
+	if (ctrlr->need_restart) {
+		vhost_blk_device_ops.new_device(vid);
+		ctrlr->need_restart = 0;
+	}
+
+	switch (msg->request) {
+	case VHOST_USER_SET_FEATURES:
+		break;
+	case VHOST_USER_SET_VRING_KICK:
+		/* vhost-user spec tells us to start polling a queue after receiving
+		 * its SET_VRING_KICK message. Let's do it!
+		 */
+		if (g_should_stop && !ctrlr->started)
+			vhost_blk_device_ops.new_device(vid);
+		break;
+	default:
+		break;
+	}
+
+	return RTE_VHOST_MSG_RESULT_NOT_HANDLED;
+}
+
+struct rte_vhost_user_extern_ops g_extern_vhost_ops = {
+	.pre_msg_handle = extern_vhost_pre_msg_handler,
+	.post_msg_handle = extern_vhost_post_msg_handler,
+};
+
+void
+vhost_session_install_rte_compat_hooks(uint32_t vid)
+{
+	int rc;
+
+	rc = rte_vhost_extern_callback_register(vid, &g_extern_vhost_ops, NULL);
+	if (rc != 0)
+		fprintf(stderr,
+			"rte_vhost_extern_callback_register() failed for vid = %d\n",
+			vid);
+}
+
+void
+vhost_dev_install_rte_compat_hooks(const char *path)
+{
+	uint64_t protocol_features = 0;
+
+	rte_vhost_driver_get_protocol_features(path, &protocol_features);
+	protocol_features |= (1ULL << VHOST_USER_PROTOCOL_F_CONFIG);
+	protocol_features |= (1ULL << VHOST_USER_PROTOCOL_F_INFLIGHT_SHMFD);
+	rte_vhost_driver_set_protocol_features(path, protocol_features);
+}
+
+#endif
-- 
2.17.2