lib/vhost/vhost.c

/*-
 *   BSD LICENSE
 *
 *   Copyright(c) 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 "spdk/stdinc.h"

#include "spdk/env.h"
#include "spdk/likely.h"
#include "spdk/string.h"
#include "spdk/util.h"
#include "spdk/memory.h"
#include "spdk/barrier.h"
#include "spdk/vhost.h"
#include "vhost_internal.h"

static struct spdk_cpuset g_vhost_core_mask;

/* Path to folder where character device will be created. Can be set by user. */
static char dev_dirname[PATH_MAX] = "";

/* Thread performing all vhost management operations */
static struct spdk_thread *g_vhost_init_thread;

static spdk_vhost_fini_cb g_fini_cpl_cb;

/**
 * DPDK calls our callbacks synchronously but the work those callbacks
 * perform needs to be async. Luckily, all DPDK callbacks are called on
 * a DPDK-internal pthread, so we'll just wait on a semaphore in there.
 */
static sem_t g_dpdk_sem;

/** Return code for the current DPDK callback */
static int g_dpdk_response;

struct vhost_session_fn_ctx {
	/** Device pointer obtained before enqueuing the event */
	struct spdk_vhost_dev *vdev;

	/** ID of the session to send event to. */
	uint32_t vsession_id;

	/** User provided function to be executed on session's thread. */
	spdk_vhost_session_fn cb_fn;

	/**
	 * User provided function to be called on the init thread
	 * after iterating through all sessions.
	 */
	spdk_vhost_dev_fn cpl_fn;

	/** Custom user context */
	void *user_ctx;
};

static TAILQ_HEAD(, spdk_vhost_dev) g_vhost_devices = TAILQ_HEAD_INITIALIZER(
			g_vhost_devices);
static pthread_mutex_t g_vhost_mutex = PTHREAD_MUTEX_INITIALIZER;

void *vhost_gpa_to_vva(struct spdk_vhost_session *vsession, uint64_t addr, uint64_t len)
{
	void *vva;
	uint64_t newlen;

	newlen = len;
	vva = (void *)rte_vhost_va_from_guest_pa(vsession->mem, addr, &newlen);
	if (newlen != len) {
		return NULL;
	}

	return vva;

}

static void
vhost_log_req_desc(struct spdk_vhost_session *vsession, struct spdk_vhost_virtqueue *virtqueue,
		   uint16_t req_id)
{
	struct vring_desc *desc, *desc_table;
	uint32_t desc_table_size;
	int rc;

	if (spdk_likely(!vhost_dev_has_feature(vsession, VHOST_F_LOG_ALL))) {
		return;
	}

	rc = vhost_vq_get_desc(vsession, virtqueue, req_id, &desc, &desc_table, &desc_table_size);
	if (spdk_unlikely(rc != 0)) {
		SPDK_ERRLOG("Can't log used ring descriptors!\n");
		return;
	}

	do {
		if (vhost_vring_desc_is_wr(desc)) {
			/* To be honest, only pages realy touched should be logged, but
			 * doing so would require tracking those changes in each backed.
			 * Also backend most likely will touch all/most of those pages so
			 * for lets assume we touched all pages passed to as writeable buffers. */
			rte_vhost_log_write(vsession->vid, desc->addr, desc->len);
		}
		vhost_vring_desc_get_next(&desc, desc_table, desc_table_size);
	} while (desc);
}

static void
vhost_log_used_vring_elem(struct spdk_vhost_session *vsession,
			  struct spdk_vhost_virtqueue *virtqueue,
			  uint16_t idx)
{
	uint64_t offset, len;

	if (spdk_likely(!vhost_dev_has_feature(vsession, VHOST_F_LOG_ALL))) {
		return;
	}

	if (spdk_unlikely(virtqueue->packed.packed_ring)) {
		offset = idx * sizeof(struct vring_packed_desc);
		len = sizeof(struct vring_packed_desc);
	} else {
		offset = offsetof(struct vring_used, ring[idx]);
		len = sizeof(virtqueue->vring.used->ring[idx]);
	}

	rte_vhost_log_used_vring(vsession->vid, virtqueue->vring_idx, offset, len);
}

static void
vhost_log_used_vring_idx(struct spdk_vhost_session *vsession,
			 struct spdk_vhost_virtqueue *virtqueue)
{
	uint64_t offset, len;
	uint16_t vq_idx;

	if (spdk_likely(!vhost_dev_has_feature(vsession, VHOST_F_LOG_ALL))) {
		return;
	}

	offset = offsetof(struct vring_used, idx);
	len = sizeof(virtqueue->vring.used->idx);
	vq_idx = virtqueue - vsession->virtqueue;

	rte_vhost_log_used_vring(vsession->vid, vq_idx, offset, len);
}

/*
 * Get available requests from avail ring.
 */
uint16_t
vhost_vq_avail_ring_get(struct spdk_vhost_virtqueue *virtqueue, uint16_t *reqs,
			uint16_t reqs_len)
{
	struct rte_vhost_vring *vring = &virtqueue->vring;
	struct vring_avail *avail = vring->avail;
	uint16_t size_mask = vring->size - 1;
	uint16_t last_idx = virtqueue->last_avail_idx, avail_idx = avail->idx;
	uint16_t count, i;

	spdk_smp_rmb();

	count = avail_idx - last_idx;
	if (spdk_likely(count == 0)) {
		return 0;
	}

	if (spdk_unlikely(count > vring->size)) {
		/* TODO: the queue is unrecoverably broken and should be marked so.
		 * For now we will fail silently and report there are no new avail entries.
		 */
		return 0;
	}

	count = spdk_min(count, reqs_len);
	virtqueue->last_avail_idx += count;
	for (i = 0; i < count; i++) {
		reqs[i] = vring->avail->ring[(last_idx + i) & size_mask];
	}

	SPDK_DEBUGLOG(vhost_ring,
		      "AVAIL: last_idx=%"PRIu16" avail_idx=%"PRIu16" count=%"PRIu16"\n",
		      last_idx, avail_idx, count);

	return count;
}

static bool
vhost_vring_desc_is_indirect(struct vring_desc *cur_desc)
{
	return !!(cur_desc->flags & VRING_DESC_F_INDIRECT);
}

static bool
vhost_vring_packed_desc_is_indirect(struct vring_packed_desc *cur_desc)
{
	return (cur_desc->flags & VRING_DESC_F_INDIRECT) != 0;
}

int
vhost_vq_get_desc(struct spdk_vhost_session *vsession, struct spdk_vhost_virtqueue *virtqueue,
		  uint16_t req_idx, struct vring_desc **desc, struct vring_desc **desc_table,
		  uint32_t *desc_table_size)
{
	if (spdk_unlikely(req_idx >= virtqueue->vring.size)) {
		return -1;
	}

	*desc = &virtqueue->vring.desc[req_idx];

	if (vhost_vring_desc_is_indirect(*desc)) {
		*desc_table_size = (*desc)->len / sizeof(**desc);
		*desc_table = vhost_gpa_to_vva(vsession, (*desc)->addr,
					       sizeof(**desc) * *desc_table_size);
		*desc = *desc_table;
		if (*desc == NULL) {
			return -1;
		}

		return 0;
	}

	*desc_table = virtqueue->vring.desc;
	*desc_table_size = virtqueue->vring.size;

	return 0;
}

int
vhost_vq_get_desc_packed(struct spdk_vhost_session *vsession,
			 struct spdk_vhost_virtqueue *virtqueue,
			 uint16_t req_idx, struct vring_packed_desc **desc,
			 struct vring_packed_desc **desc_table, uint32_t *desc_table_size)
{
	*desc =  &virtqueue->vring.desc_packed[req_idx];

	/* In packed ring when the desc is non-indirect we get next desc
	 * by judging (desc->flag & VRING_DESC_F_NEXT) != 0. When the desc
	 * is indirect we get next desc by idx and desc_table_size. It's
	 * different from split ring.
	 */
	if (vhost_vring_packed_desc_is_indirect(*desc)) {
		*desc_table_size = (*desc)->len / sizeof(struct vring_packed_desc);
		*desc_table = vhost_gpa_to_vva(vsession, (*desc)->addr,
					       (*desc)->len);
		*desc = *desc_table;
		if (spdk_unlikely(*desc == NULL)) {
			return -1;
		}
	} else {
		*desc_table = NULL;
		*desc_table_size  = 0;
	}

	return 0;
}

int
vhost_vq_used_signal(struct spdk_vhost_session *vsession,
		     struct spdk_vhost_virtqueue *virtqueue)
{
	if (virtqueue->used_req_cnt == 0) {
		return 0;
	}

	virtqueue->req_cnt += virtqueue->used_req_cnt;
	virtqueue->used_req_cnt = 0;

	SPDK_DEBUGLOG(vhost_ring,
		      "Queue %td - USED RING: sending IRQ: last used %"PRIu16"\n",
		      virtqueue - vsession->virtqueue, virtqueue->last_used_idx);

	if (rte_vhost_vring_call(vsession->vid, virtqueue->vring_idx) == 0) {
		/* interrupt signalled */
		return 1;
	} else {
		/* interrupt not signalled */
		return 0;
	}
}


static void
check_session_io_stats(struct spdk_vhost_session *vsession, uint64_t now)
{
	struct spdk_vhost_virtqueue *virtqueue;
	uint32_t irq_delay_base = vsession->coalescing_delay_time_base;
	uint32_t io_threshold = vsession->coalescing_io_rate_threshold;
	int32_t irq_delay;
	uint32_t req_cnt;
	uint16_t q_idx;

	if (now < vsession->next_stats_check_time) {
		return;
	}

	vsession->next_stats_check_time = now + vsession->stats_check_interval;
	for (q_idx = 0; q_idx < vsession->max_queues; q_idx++) {
		virtqueue = &vsession->virtqueue[q_idx];

		req_cnt = virtqueue->req_cnt + virtqueue->used_req_cnt;
		if (req_cnt <= io_threshold) {
			continue;
		}

		irq_delay = (irq_delay_base * (req_cnt - io_threshold)) / io_threshold;
		virtqueue->irq_delay_time = (uint32_t) spdk_max(0, irq_delay);

		virtqueue->req_cnt = 0;
		virtqueue->next_event_time = now;
	}
}

static inline bool
vhost_vq_event_is_suppressed(struct spdk_vhost_virtqueue *vq)
{
	if (spdk_unlikely(vq->packed.packed_ring)) {
		if (vq->vring.driver_event->flags & VRING_PACKED_EVENT_FLAG_DISABLE) {
			return true;
		}
	} else {
		if (vq->vring.avail->flags & VRING_AVAIL_F_NO_INTERRUPT) {
			return true;
		}
	}

	return false;
}

void
vhost_session_used_signal(struct spdk_vhost_session *vsession)
{
	struct spdk_vhost_virtqueue *virtqueue;
	uint64_t now;
	uint16_t q_idx;

	if (vsession->coalescing_delay_time_base == 0) {
		for (q_idx = 0; q_idx < vsession->max_queues; q_idx++) {
			virtqueue = &vsession->virtqueue[q_idx];

			if (virtqueue->vring.desc == NULL) {
				continue;
			}

			if (vhost_vq_event_is_suppressed(virtqueue)) {
				continue;
			}

			vhost_vq_used_signal(vsession, virtqueue);
		}
	} else {
		now = spdk_get_ticks();
		check_session_io_stats(vsession, now);

		for (q_idx = 0; q_idx < vsession->max_queues; q_idx++) {
			virtqueue = &vsession->virtqueue[q_idx];

			/* No need for event right now */
			if (now < virtqueue->next_event_time) {
				continue;
			}

			if (vhost_vq_event_is_suppressed(virtqueue)) {
				continue;
			}

			if (!vhost_vq_used_signal(vsession, virtqueue)) {
				continue;
			}

			/* Syscall is quite long so update time */
			now = spdk_get_ticks();
			virtqueue->next_event_time = now + virtqueue->irq_delay_time;
		}
	}
}

static int
vhost_session_set_coalescing(struct spdk_vhost_dev *vdev,
			     struct spdk_vhost_session *vsession, void *ctx)
{
	vsession->coalescing_delay_time_base =
		vdev->coalescing_delay_us * spdk_get_ticks_hz() / 1000000ULL;
	vsession->coalescing_io_rate_threshold =
		vdev->coalescing_iops_threshold * SPDK_VHOST_STATS_CHECK_INTERVAL_MS / 1000U;
	return 0;
}

static int
vhost_dev_set_coalescing(struct spdk_vhost_dev *vdev, uint32_t delay_base_us,
			 uint32_t iops_threshold)
{
	uint64_t delay_time_base = delay_base_us * spdk_get_ticks_hz() / 1000000ULL;
	uint32_t io_rate = iops_threshold * SPDK_VHOST_STATS_CHECK_INTERVAL_MS / 1000U;

	if (delay_time_base >= UINT32_MAX) {
		SPDK_ERRLOG("Delay time of %"PRIu32" is to big\n", delay_base_us);
		return -EINVAL;
	} else if (io_rate == 0) {
		SPDK_ERRLOG("IOPS rate of %"PRIu32" is too low. Min is %u\n", io_rate,
			    1000U / SPDK_VHOST_STATS_CHECK_INTERVAL_MS);
		return -EINVAL;
	}

	vdev->coalescing_delay_us = delay_base_us;
	vdev->coalescing_iops_threshold = iops_threshold;
	return 0;
}

int
spdk_vhost_set_coalescing(struct spdk_vhost_dev *vdev, uint32_t delay_base_us,
			  uint32_t iops_threshold)
{
	int rc;

	rc = vhost_dev_set_coalescing(vdev, delay_base_us, iops_threshold);
	if (rc != 0) {
		return rc;
	}

	vhost_dev_foreach_session(vdev, vhost_session_set_coalescing, NULL, NULL);
	return 0;
}

void
spdk_vhost_get_coalescing(struct spdk_vhost_dev *vdev, uint32_t *delay_base_us,
			  uint32_t *iops_threshold)
{
	if (delay_base_us) {
		*delay_base_us = vdev->coalescing_delay_us;
	}

	if (iops_threshold) {
		*iops_threshold = vdev->coalescing_iops_threshold;
	}
}

/*
 * Enqueue id and len to used ring.
 */
void
vhost_vq_used_ring_enqueue(struct spdk_vhost_session *vsession,
			   struct spdk_vhost_virtqueue *virtqueue,
			   uint16_t id, uint32_t len)
{
	struct rte_vhost_vring *vring = &virtqueue->vring;
	struct vring_used *used = vring->used;
	uint16_t last_idx = virtqueue->last_used_idx & (vring->size - 1);
	uint16_t vq_idx = virtqueue->vring_idx;

	SPDK_DEBUGLOG(vhost_ring,
		      "Queue %td - USED RING: last_idx=%"PRIu16" req id=%"PRIu16" len=%"PRIu32"\n",
		      virtqueue - vsession->virtqueue, virtqueue->last_used_idx, id, len);

	vhost_log_req_desc(vsession, virtqueue, id);

	virtqueue->last_used_idx++;
	used->ring[last_idx].id = id;
	used->ring[last_idx].len = len;

	/* Ensure the used ring is updated before we log it or increment used->idx. */
	spdk_smp_wmb();

	rte_vhost_set_last_inflight_io_split(vsession->vid, vq_idx, id);

	vhost_log_used_vring_elem(vsession, virtqueue, last_idx);
	* (volatile uint16_t *) &used->idx = virtqueue->last_used_idx;
	vhost_log_used_vring_idx(vsession, virtqueue);

	rte_vhost_clr_inflight_desc_split(vsession->vid, vq_idx, virtqueue->last_used_idx, id);

	virtqueue->used_req_cnt++;
}

void
vhost_vq_packed_ring_enqueue(struct spdk_vhost_session *vsession,
			     struct spdk_vhost_virtqueue *virtqueue,
			     uint16_t num_descs, uint16_t buffer_id,
			     uint32_t length)
{
	struct vring_packed_desc *desc = &virtqueue->vring.desc_packed[virtqueue->last_used_idx];
	bool used, avail;

	SPDK_DEBUGLOG(vhost_ring,
		      "Queue %td - RING: buffer_id=%"PRIu16"\n",
		      virtqueue - vsession->virtqueue, buffer_id);

	/* When the descriptor is used, two flags in descriptor
	 * avail flag and used flag are set to equal
	 * and used flag value == used_wrap_counter.
	 */
	used = !!(desc->flags & VRING_DESC_F_USED);
	avail = !!(desc->flags & VRING_DESC_F_AVAIL);
	if (spdk_unlikely(used == virtqueue->packed.used_phase && used == avail)) {
		SPDK_ERRLOG("descriptor has been used before\n");
		return;
	}

	/* In used desc addr is unused and len specifies the buffer length
	 * that has been written to by the device.
	 */
	desc->addr = 0;
	desc->len = length;

	/* This bit specifies whether any data has been written by the device */
	if (length != 0) {
		desc->flags |= VRING_DESC_F_WRITE;
	}

	/* Buffer ID is included in the last descriptor in the list.
	 * The driver needs to keep track of the size of the list corresponding
	 * to each buffer ID.
	 */
	desc->id = buffer_id;

	/* A device MUST NOT make the descriptor used before buffer_id is
	 * written to the descriptor.
	 */
	spdk_smp_wmb();
	/* To mark a desc as used, the device sets the F_USED bit in flags to match
	 * the internal Device ring wrap counter. It also sets the F_AVAIL bit to
	 * match the same value.
	 */
	if (virtqueue->packed.used_phase) {
		desc->flags |= VRING_DESC_F_AVAIL_USED;
	} else {
		desc->flags &= ~VRING_DESC_F_AVAIL_USED;
	}

	vhost_log_used_vring_elem(vsession, virtqueue, virtqueue->last_used_idx);
	virtqueue->last_used_idx += num_descs;
	if (virtqueue->last_used_idx >= virtqueue->vring.size) {
		virtqueue->last_used_idx -= virtqueue->vring.size;
		virtqueue->packed.used_phase = !virtqueue->packed.used_phase;
	}

	virtqueue->used_req_cnt++;
}

bool
vhost_vq_packed_ring_is_avail(struct spdk_vhost_virtqueue *virtqueue)
{
	uint16_t flags = virtqueue->vring.desc_packed[virtqueue->last_avail_idx].flags;

	/* To mark a desc as available, the driver sets the F_AVAIL bit in flags
	 * to match the internal avail wrap counter. It also sets the F_USED bit to
	 * match the inverse value but it's not mandatory.
	 */
	return (!!(flags & VRING_DESC_F_AVAIL) == virtqueue->packed.avail_phase);
}

bool
vhost_vring_packed_desc_is_wr(struct vring_packed_desc *cur_desc)
{
	return (cur_desc->flags & VRING_DESC_F_WRITE) != 0;
}

int
vhost_vring_packed_desc_get_next(struct vring_packed_desc **desc, uint16_t *req_idx,
				 struct spdk_vhost_virtqueue *vq,
				 struct vring_packed_desc *desc_table,
				 uint32_t desc_table_size)
{
	if (desc_table != NULL) {
		/* When the desc_table isn't NULL means it's indirect and we get the next
		 * desc by req_idx and desc_table_size. The return value is NULL means
		 * we reach the last desc of this request.
		 */
		(*req_idx)++;
		if (*req_idx < desc_table_size) {
			*desc = &desc_table[*req_idx];
		} else {
			*desc = NULL;
		}
	} else {
		/* When the desc_table is NULL means it's non-indirect and we get the next
		 * desc by req_idx and F_NEXT in flags. The return value is NULL means
		 * we reach the last desc of this request. When return new desc
		 * we update the req_idx too.
		 */
		if (((*desc)->flags & VRING_DESC_F_NEXT) == 0) {
			*desc = NULL;
			return 0;
		}

		*req_idx = (*req_idx + 1) % vq->vring.size;
		*desc = &vq->vring.desc_packed[*req_idx];
	}

	return 0;
}

static int
vhost_vring_desc_payload_to_iov(struct spdk_vhost_session *vsession, struct iovec *iov,
				uint16_t *iov_index, uintptr_t payload, uint64_t remaining)
{
	uintptr_t vva;
	uint64_t len;

	do {
		if (*iov_index >= SPDK_VHOST_IOVS_MAX) {
			SPDK_ERRLOG("SPDK_VHOST_IOVS_MAX(%d) reached\n", SPDK_VHOST_IOVS_MAX);
			return -1;
		}
		len = remaining;
		vva = (uintptr_t)rte_vhost_va_from_guest_pa(vsession->mem, payload, &len);
		if (vva == 0 || len == 0) {
			SPDK_ERRLOG("gpa_to_vva(%p) == NULL\n", (void *)payload);
			return -1;
		}
		iov[*iov_index].iov_base = (void *)vva;
		iov[*iov_index].iov_len = len;
		remaining -= len;
		payload += len;
		(*iov_index)++;
	} while (remaining);

	return 0;
}

int
vhost_vring_packed_desc_to_iov(struct spdk_vhost_session *vsession, struct iovec *iov,
			       uint16_t *iov_index, const struct vring_packed_desc *desc)
{
	return vhost_vring_desc_payload_to_iov(vsession, iov, iov_index,
					       desc->addr, desc->len);
}

/* 1, Traverse the desc chain to get the buffer_id and return buffer_id as task_idx.
 * 2, Update the vq->last_avail_idx to point next available desc chain.
 * 3, Update the avail_wrap_counter if last_avail_idx overturn.
 */
uint16_t
vhost_vring_packed_desc_get_buffer_id(struct spdk_vhost_virtqueue *vq, uint16_t req_idx,
				      uint16_t *num_descs)
{
	struct vring_packed_desc *desc;
	uint16_t desc_head = req_idx;

	*num_descs = 1;

	desc =  &vq->vring.desc_packed[req_idx];
	if (!vhost_vring_packed_desc_is_indirect(desc)) {
		while ((desc->flags & VRING_DESC_F_NEXT) != 0) {
			req_idx = (req_idx + 1) % vq->vring.size;
			desc = &vq->vring.desc_packed[req_idx];
			(*num_descs)++;
		}
	}

	/* Queue Size doesn't have to be a power of 2
	 * Device maintains last_avail_idx so we can make sure
	 * the value is valid(0 ~ vring.size - 1)
	 */
	vq->last_avail_idx = (req_idx + 1) % vq->vring.size;
	if (vq->last_avail_idx < desc_head) {
		vq->packed.avail_phase = !vq->packed.avail_phase;
	}

	return desc->id;
}

int
vhost_vring_desc_get_next(struct vring_desc **desc,
			  struct vring_desc *desc_table, uint32_t desc_table_size)
{
	struct vring_desc *old_desc = *desc;
	uint16_t next_idx;

	if ((old_desc->flags & VRING_DESC_F_NEXT) == 0) {
		*desc = NULL;
		return 0;
	}

	next_idx = old_desc->next;
	if (spdk_unlikely(next_idx >= desc_table_size)) {
		*desc = NULL;
		return -1;
	}

	*desc = &desc_table[next_idx];
	return 0;
}

int
vhost_vring_desc_to_iov(struct spdk_vhost_session *vsession, struct iovec *iov,
			uint16_t *iov_index, const struct vring_desc *desc)
{
	return vhost_vring_desc_payload_to_iov(vsession, iov, iov_index,
					       desc->addr, desc->len);
}

static struct spdk_vhost_session *
vhost_session_find_by_id(struct spdk_vhost_dev *vdev, unsigned id)
{
	struct spdk_vhost_session *vsession;

	TAILQ_FOREACH(vsession, &vdev->vsessions, tailq) {
		if (vsession->id == id) {
			return vsession;
		}
	}

	return NULL;
}

struct spdk_vhost_session *
vhost_session_find_by_vid(int vid)
{
	struct spdk_vhost_dev *vdev;
	struct spdk_vhost_session *vsession;

	TAILQ_FOREACH(vdev, &g_vhost_devices, tailq) {
		TAILQ_FOREACH(vsession, &vdev->vsessions, tailq) {
			if (vsession->vid == vid) {
				return vsession;
			}
		}
	}

	return NULL;
}

struct spdk_vhost_dev *
spdk_vhost_dev_next(struct spdk_vhost_dev *vdev)
{
	if (vdev == NULL) {
		return TAILQ_FIRST(&g_vhost_devices);
	}

	return TAILQ_NEXT(vdev, tailq);
}

struct spdk_vhost_dev *
spdk_vhost_dev_find(const char *ctrlr_name)
{
	struct spdk_vhost_dev *vdev;
	size_t dev_dirname_len = strlen(dev_dirname);

	if (strncmp(ctrlr_name, dev_dirname, dev_dirname_len) == 0) {
		ctrlr_name += dev_dirname_len;
	}

	TAILQ_FOREACH(vdev, &g_vhost_devices, tailq) {
		if (strcmp(vdev->name, ctrlr_name) == 0) {
			return vdev;
		}
	}

	return NULL;
}

static int
vhost_parse_core_mask(const char *mask, struct spdk_cpuset *cpumask)
{
	int rc;

	if (cpumask == NULL) {
		return -1;
	}

	if (mask == NULL) {
		spdk_cpuset_copy(cpumask, &g_vhost_core_mask);
		return 0;
	}

	rc = spdk_cpuset_parse(cpumask, mask);
	if (rc < 0) {
		SPDK_ERRLOG("invalid cpumask %s\n", mask);
		return -1;
	}

	spdk_cpuset_and(cpumask, &g_vhost_core_mask);

	if (spdk_cpuset_count(cpumask) == 0) {
		SPDK_ERRLOG("no cpu is selected among core mask(=%s)\n",
			    spdk_cpuset_fmt(&g_vhost_core_mask));
		return -1;
	}

	return 0;
}

static void
vhost_setup_core_mask(void *ctx)
{
	struct spdk_thread *thread = spdk_get_thread();
	spdk_cpuset_or(&g_vhost_core_mask, spdk_thread_get_cpumask(thread));
}

static void
vhost_setup_core_mask_done(void *ctx)
{
	spdk_vhost_init_cb init_cb = ctx;

	if (spdk_cpuset_count(&g_vhost_core_mask) == 0) {
		init_cb(-ECHILD);
		return;
	}

	init_cb(0);
}

static void
vhost_dev_thread_exit(void *arg1)
{
	spdk_thread_exit(spdk_get_thread());
}

int
vhost_dev_register(struct spdk_vhost_dev *vdev, const char *name, const char *mask_str,
		   const struct spdk_vhost_dev_backend *backend)
{
	char path[PATH_MAX];
	struct spdk_cpuset cpumask = {};
	int rc;

	assert(vdev);
	if (name == NULL) {
		SPDK_ERRLOG("Can't register controller with no name\n");
		return -EINVAL;
	}

	if (vhost_parse_core_mask(mask_str, &cpumask) != 0) {
		SPDK_ERRLOG("cpumask %s is invalid (core mask is 0x%s)\n",
			    mask_str, spdk_cpuset_fmt(&g_vhost_core_mask));
		return -EINVAL;
	}

	if (spdk_vhost_dev_find(name)) {
		SPDK_ERRLOG("vhost controller %s already exists.\n", name);
		return -EEXIST;
	}

	if (snprintf(path, sizeof(path), "%s%s", dev_dirname, name) >= (int)sizeof(path)) {
		SPDK_ERRLOG("Resulting socket path for controller %s is too long: %s%s\n", name, dev_dirname,
			    name);
		return -EINVAL;
	}

	vdev->name = strdup(name);
	vdev->path = strdup(path);
	if (vdev->name == NULL || vdev->path == NULL) {
		rc = -EIO;
		goto out;
	}

	vdev->thread = spdk_thread_create(vdev->name, &cpumask);
	if (vdev->thread == NULL) {
		SPDK_ERRLOG("Failed to create thread for vhost controller %s.\n", name);
		rc = -EIO;
		goto out;
	}

	vdev->registered = true;
	vdev->backend = backend;
	TAILQ_INIT(&vdev->vsessions);

	vhost_dev_set_coalescing(vdev, SPDK_VHOST_COALESCING_DELAY_BASE_US,
				 SPDK_VHOST_VQ_IOPS_COALESCING_THRESHOLD);

	if (vhost_register_unix_socket(path, name, vdev->virtio_features, vdev->disabled_features,
				       vdev->protocol_features)) {
		spdk_thread_send_msg(vdev->thread, vhost_dev_thread_exit, NULL);
		rc = -EIO;
		goto out;
	}

	TAILQ_INSERT_TAIL(&g_vhost_devices, vdev, tailq);

	SPDK_INFOLOG(vhost, "Controller %s: new controller added\n", vdev->name);
	return 0;

out:
	free(vdev->name);
	free(vdev->path);
	return rc;
}

int
vhost_dev_unregister(struct spdk_vhost_dev *vdev)
{
	if (!TAILQ_EMPTY(&vdev->vsessions)) {
		SPDK_ERRLOG("Controller %s has still valid connection.\n", vdev->name);
		return -EBUSY;
	}

	if (vdev->registered && vhost_driver_unregister(vdev->path) != 0) {
		SPDK_ERRLOG("Could not unregister controller %s with vhost library\n"
			    "Check if domain socket %s still exists\n",
			    vdev->name, vdev->path);
		return -EIO;
	}

	SPDK_INFOLOG(vhost, "Controller %s: removed\n", vdev->name);

	spdk_thread_send_msg(vdev->thread, vhost_dev_thread_exit, NULL);

	free(vdev->name);
	free(vdev->path);
	TAILQ_REMOVE(&g_vhost_devices, vdev, tailq);
	return 0;
}

const char *
spdk_vhost_dev_get_name(struct spdk_vhost_dev *vdev)
{
	assert(vdev != NULL);
	return vdev->name;
}

const struct spdk_cpuset *
spdk_vhost_dev_get_cpumask(struct spdk_vhost_dev *vdev)
{
	assert(vdev != NULL);
	return spdk_thread_get_cpumask(vdev->thread);
}

static void
wait_for_semaphore(int timeout_sec, const char *errmsg)
{
	struct timespec timeout;
	int rc;

	clock_gettime(CLOCK_REALTIME, &timeout);
	timeout.tv_sec += timeout_sec;
	rc = sem_timedwait(&g_dpdk_sem, &timeout);
	if (rc != 0) {
		SPDK_ERRLOG("Timeout waiting for event: %s.\n", errmsg);
		sem_wait(&g_dpdk_sem);
	}
}

static void
vhost_session_cb_done(int rc)
{
	g_dpdk_response = rc;
	sem_post(&g_dpdk_sem);
}

void
vhost_session_start_done(struct spdk_vhost_session *vsession, int response)
{
	if (response == 0) {
		vsession->started = true;

		assert(vsession->vdev->active_session_num < UINT32_MAX);
		vsession->vdev->active_session_num++;
	}

	vhost_session_cb_done(response);
}

void
vhost_session_stop_done(struct spdk_vhost_session *vsession, int response)
{
	if (response == 0) {
		vsession->started = false;

		assert(vsession->vdev->active_session_num > 0);
		vsession->vdev->active_session_num--;
	}

	vhost_session_cb_done(response);
}

static void
vhost_event_cb(void *arg1)
{
	struct vhost_session_fn_ctx *ctx = arg1;
	struct spdk_vhost_session *vsession;

	if (pthread_mutex_trylock(&g_vhost_mutex) != 0) {
		spdk_thread_send_msg(spdk_get_thread(), vhost_event_cb, arg1);
		return;
	}

	vsession = vhost_session_find_by_id(ctx->vdev, ctx->vsession_id);
	ctx->cb_fn(ctx->vdev, vsession, NULL);
	pthread_mutex_unlock(&g_vhost_mutex);
}

int
vhost_session_send_event(struct spdk_vhost_session *vsession,
			 spdk_vhost_session_fn cb_fn, unsigned timeout_sec,
			 const char *errmsg)
{
	struct vhost_session_fn_ctx ev_ctx = {0};
	struct spdk_vhost_dev *vdev = vsession->vdev;

	ev_ctx.vdev = vdev;
	ev_ctx.vsession_id = vsession->id;
	ev_ctx.cb_fn = cb_fn;

	spdk_thread_send_msg(vdev->thread, vhost_event_cb, &ev_ctx);

	pthread_mutex_unlock(&g_vhost_mutex);
	wait_for_semaphore(timeout_sec, errmsg);
	pthread_mutex_lock(&g_vhost_mutex);

	return g_dpdk_response;
}

static void
foreach_session_finish_cb(void *arg1)
{
	struct vhost_session_fn_ctx *ev_ctx = arg1;
	struct spdk_vhost_dev *vdev = ev_ctx->vdev;

	if (pthread_mutex_trylock(&g_vhost_mutex) != 0) {
		spdk_thread_send_msg(spdk_get_thread(),
				     foreach_session_finish_cb, arg1);
		return;
	}

	assert(vdev->pending_async_op_num > 0);
	vdev->pending_async_op_num--;
	if (ev_ctx->cpl_fn != NULL) {
		ev_ctx->cpl_fn(vdev, ev_ctx->user_ctx);
	}

	pthread_mutex_unlock(&g_vhost_mutex);
	free(ev_ctx);
}

static void
foreach_session(void *arg1)
{
	struct vhost_session_fn_ctx *ev_ctx = arg1;
	struct spdk_vhost_session *vsession;
	struct spdk_vhost_dev *vdev = ev_ctx->vdev;
	int rc;

	if (pthread_mutex_trylock(&g_vhost_mutex) != 0) {
		spdk_thread_send_msg(spdk_get_thread(), foreach_session, arg1);
		return;
	}

	TAILQ_FOREACH(vsession, &vdev->vsessions, tailq) {
		if (vsession->initialized) {
			rc = ev_ctx->cb_fn(vdev, vsession, ev_ctx->user_ctx);
			if (rc < 0) {
				goto out;
			}
		}
	}

out:
	pthread_mutex_unlock(&g_vhost_mutex);

	spdk_thread_send_msg(g_vhost_init_thread, foreach_session_finish_cb, arg1);
}

void
vhost_dev_foreach_session(struct spdk_vhost_dev *vdev,
			  spdk_vhost_session_fn fn,
			  spdk_vhost_dev_fn cpl_fn,
			  void *arg)
{
	struct vhost_session_fn_ctx *ev_ctx;

	ev_ctx = calloc(1, sizeof(*ev_ctx));
	if (ev_ctx == NULL) {
		SPDK_ERRLOG("Failed to alloc vhost event.\n");
		assert(false);
		return;
	}

	ev_ctx->vdev = vdev;
	ev_ctx->cb_fn = fn;
	ev_ctx->cpl_fn = cpl_fn;
	ev_ctx->user_ctx = arg;

	assert(vdev->pending_async_op_num < UINT32_MAX);
	vdev->pending_async_op_num++;

	spdk_thread_send_msg(vdev->thread, foreach_session, ev_ctx);
}

static int
_stop_session(struct spdk_vhost_session *vsession)
{
	struct spdk_vhost_dev *vdev = vsession->vdev;
	struct spdk_vhost_virtqueue *q;
	int rc;
	uint16_t i;

	rc = vdev->backend->stop_session(vsession);
	if (rc != 0) {
		SPDK_ERRLOG("Couldn't stop device with vid %d.\n", vsession->vid);
		pthread_mutex_unlock(&g_vhost_mutex);
		return rc;
	}

	for (i = 0; i < vsession->max_queues; i++) {
		q = &vsession->virtqueue[i];

		/* vring.desc and vring.desc_packed are in a union struct
		 * so q->vring.desc can replace q->vring.desc_packed.
		 */
		if (q->vring.desc == NULL) {
			continue;
		}

		/* Packed virtqueues support up to 2^15 entries each
		 * so left one bit can be used as wrap counter.
		 */
		if (q->packed.packed_ring) {
			q->last_avail_idx = q->last_avail_idx |
					    ((uint16_t)q->packed.avail_phase << 15);
			q->last_used_idx = q->last_used_idx |
					   ((uint16_t)q->packed.used_phase << 15);
		}

		rte_vhost_set_vring_base(vsession->vid, i, q->last_avail_idx, q->last_used_idx);
	}

	vhost_session_mem_unregister(vsession->mem);
	free(vsession->mem);

	return 0;
}

int
vhost_stop_device_cb(int vid)
{
	struct spdk_vhost_session *vsession;
	int rc;

	pthread_mutex_lock(&g_vhost_mutex);
	vsession = vhost_session_find_by_vid(vid);
	if (vsession == NULL) {
		SPDK_ERRLOG("Couldn't find session with vid %d.\n", vid);
		pthread_mutex_unlock(&g_vhost_mutex);
		return -EINVAL;
	}

	if (!vsession->started) {
		/* already stopped, nothing to do */
		pthread_mutex_unlock(&g_vhost_mutex);
		return -EALREADY;
	}

	rc = _stop_session(vsession);
	pthread_mutex_unlock(&g_vhost_mutex);

	return rc;
}

int
vhost_start_device_cb(int vid)
{
	struct spdk_vhost_dev *vdev;
	struct spdk_vhost_session *vsession;
	int rc = -1;
	uint16_t i;
	bool packed_ring;

	pthread_mutex_lock(&g_vhost_mutex);

	vsession = vhost_session_find_by_vid(vid);
	if (vsession == NULL) {
		SPDK_ERRLOG("Couldn't find session with vid %d.\n", vid);
		goto out;
	}

	vdev = vsession->vdev;
	if (vsession->started) {
		/* already started, nothing to do */
		rc = 0;
		goto out;
	}

	if (vhost_get_negotiated_features(vid, &vsession->negotiated_features) != 0) {
		SPDK_ERRLOG("vhost device %d: Failed to get negotiated driver features\n", vid);
		goto out;
	}

	packed_ring = ((vsession->negotiated_features & (1ULL << VIRTIO_F_RING_PACKED)) != 0);

	vsession->max_queues = 0;
	memset(vsession->virtqueue, 0, sizeof(vsession->virtqueue));
	for (i = 0; i < SPDK_VHOST_MAX_VQUEUES; i++) {
		struct spdk_vhost_virtqueue *q = &vsession->virtqueue[i];

		q->vring_idx = -1;
		if (rte_vhost_get_vhost_vring(vid, i, &q->vring)) {
			continue;
		}
		q->vring_idx = i;
		rte_vhost_get_vhost_ring_inflight(vid, i, &q->vring_inflight);

		/* vring.desc and vring.desc_packed are in a union struct
		 * so q->vring.desc can replace q->vring.desc_packed.
		 */
		if (q->vring.desc == NULL || q->vring.size == 0) {
			continue;
		}

		if (rte_vhost_get_vring_base(vsession->vid, i, &q->last_avail_idx, &q->last_used_idx)) {
			q->vring.desc = NULL;
			continue;
		}

		if (packed_ring) {
			/* Packed virtqueues support up to 2^15 entries each
			 * so left one bit can be used as wrap counter.
			 */
			q->packed.avail_phase = q->last_avail_idx >> 15;
			q->last_avail_idx = q->last_avail_idx & 0x7FFF;
			q->packed.used_phase = q->last_used_idx >> 15;
			q->last_used_idx = q->last_used_idx & 0x7FFF;

			/* Disable I/O submission notifications, we'll be polling. */
			q->vring.device_event->flags = VRING_PACKED_EVENT_FLAG_DISABLE;
		} else {
			/* Disable I/O submission notifications, we'll be polling. */
			q->vring.used->flags = VRING_USED_F_NO_NOTIFY;
		}

		q->packed.packed_ring = packed_ring;
		vsession->max_queues = i + 1;
	}

	if (vhost_get_mem_table(vid, &vsession->mem) != 0) {
		SPDK_ERRLOG("vhost device %d: Failed to get guest memory table\n", vid);
		goto out;
	}

	/*
	 * Not sure right now but this look like some kind of QEMU bug and guest IO
	 * might be frozed without kicking all queues after live-migration. This look like
	 * the previous vhost instance failed to effectively deliver all interrupts before
	 * the GET_VRING_BASE message. This shouldn't harm guest since spurious interrupts
	 * should be ignored by guest virtio driver.
	 *
	 * Tested on QEMU 2.10.91 and 2.11.50.
	 */
	for (i = 0; i < vsession->max_queues; i++) {
		struct spdk_vhost_virtqueue *q = &vsession->virtqueue[i];

		/* vring.desc and vring.desc_packed are in a union struct
		 * so q->vring.desc can replace q->vring.desc_packed.
		 */
		if (q->vring.desc != NULL && q->vring.size > 0) {
			rte_vhost_vring_call(vsession->vid, q->vring_idx);
		}
	}

	vhost_session_set_coalescing(vdev, vsession, NULL);
	vhost_session_mem_register(vsession->mem);
	vsession->initialized = true;
	rc = vdev->backend->start_session(vsession);
	if (rc != 0) {
		vhost_session_mem_unregister(vsession->mem);
		free(vsession->mem);
		goto out;
	}

out:
	pthread_mutex_unlock(&g_vhost_mutex);
	return rc;
}

int
spdk_vhost_set_socket_path(const char *basename)
{
	int ret;

	if (basename && strlen(basename) > 0) {
		ret = snprintf(dev_dirname, sizeof(dev_dirname) - 2, "%s", basename);
		if (ret <= 0) {
			return -EINVAL;
		}
		if ((size_t)ret >= sizeof(dev_dirname) - 2) {
			SPDK_ERRLOG("Char dev dir path length %d is too long\n", ret);
			return -EINVAL;
		}

		if (dev_dirname[ret - 1] != '/') {
			dev_dirname[ret] = '/';
			dev_dirname[ret + 1]  = '\0';
		}
	}

	return 0;
}

void
vhost_dump_info_json(struct spdk_vhost_dev *vdev, struct spdk_json_write_ctx *w)
{
	assert(vdev->backend->dump_info_json != NULL);
	vdev->backend->dump_info_json(vdev, w);
}

int
spdk_vhost_dev_remove(struct spdk_vhost_dev *vdev)
{
	if (vdev->pending_async_op_num) {
		return -EBUSY;
	}

	return vdev->backend->remove_device(vdev);
}

int
vhost_new_connection_cb(int vid, const char *ifname)
{
	struct spdk_vhost_dev *vdev;
	struct spdk_vhost_session *vsession;

	pthread_mutex_lock(&g_vhost_mutex);

	vdev = spdk_vhost_dev_find(ifname);
	if (vdev == NULL) {
		SPDK_ERRLOG("Couldn't find device with vid %d to create connection for.\n", vid);
		pthread_mutex_unlock(&g_vhost_mutex);
		return -1;
	}

	/* We expect sessions inside vdev->vsessions to be sorted in ascending
	 * order in regard of vsession->id. For now we always set id = vsessions_cnt++
	 * and append each session to the very end of the vsessions list.
	 * This is required for spdk_vhost_dev_foreach_session() to work.
	 */
	if (vdev->vsessions_num == UINT_MAX) {
		assert(false);
		return -EINVAL;
	}

	if (posix_memalign((void **)&vsession, SPDK_CACHE_LINE_SIZE, sizeof(*vsession) +
			   vdev->backend->session_ctx_size)) {
		SPDK_ERRLOG("vsession alloc failed\n");
		pthread_mutex_unlock(&g_vhost_mutex);
		return -1;
	}
	memset(vsession, 0, sizeof(*vsession) + vdev->backend->session_ctx_size);

	vsession->vdev = vdev;
	vsession->vid = vid;
	vsession->id = vdev->vsessions_num++;
	vsession->name = spdk_sprintf_alloc("%ss%u", vdev->name, vsession->vid);
	if (vsession->name == NULL) {
		SPDK_ERRLOG("vsession alloc failed\n");
		pthread_mutex_unlock(&g_vhost_mutex);
		free(vsession);
		return -1;
	}
	vsession->started = false;
	vsession->initialized = false;
	vsession->next_stats_check_time = 0;
	vsession->stats_check_interval = SPDK_VHOST_STATS_CHECK_INTERVAL_MS *
					 spdk_get_ticks_hz() / 1000UL;
	TAILQ_INSERT_TAIL(&vdev->vsessions, vsession, tailq);

	vhost_session_install_rte_compat_hooks(vsession);
	pthread_mutex_unlock(&g_vhost_mutex);
	return 0;
}

int
vhost_destroy_connection_cb(int vid)
{
	struct spdk_vhost_session *vsession;
	int rc = 0;

	pthread_mutex_lock(&g_vhost_mutex);
	vsession = vhost_session_find_by_vid(vid);
	if (vsession == NULL) {
		SPDK_ERRLOG("Couldn't find session with vid %d.\n", vid);
		pthread_mutex_unlock(&g_vhost_mutex);
		return -EINVAL;
	}

	if (vsession->started) {
		rc = _stop_session(vsession);
	}

	TAILQ_REMOVE(&vsession->vdev->vsessions, vsession, tailq);
	free(vsession->name);
	free(vsession);
	pthread_mutex_unlock(&g_vhost_mutex);

	return rc;
}

void
spdk_vhost_lock(void)
{
	pthread_mutex_lock(&g_vhost_mutex);
}

int
spdk_vhost_trylock(void)
{
	return -pthread_mutex_trylock(&g_vhost_mutex);
}

void
spdk_vhost_unlock(void)
{
	pthread_mutex_unlock(&g_vhost_mutex);
}

void
spdk_vhost_init(spdk_vhost_init_cb init_cb)
{
	size_t len;
	int ret;

	g_vhost_init_thread = spdk_get_thread();
	assert(g_vhost_init_thread != NULL);

	if (dev_dirname[0] == '\0') {
		if (getcwd(dev_dirname, sizeof(dev_dirname) - 1) == NULL) {
			SPDK_ERRLOG("getcwd failed (%d): %s\n", errno, spdk_strerror(errno));
			ret = -1;
			goto out;
		}

		len = strlen(dev_dirname);
		if (dev_dirname[len - 1] != '/') {
			dev_dirname[len] = '/';
			dev_dirname[len + 1] = '\0';
		}
	}

	ret = sem_init(&g_dpdk_sem, 0, 0);
	if (ret != 0) {
		SPDK_ERRLOG("Failed to initialize semaphore for rte_vhost pthread.\n");
		ret = -1;
		goto out;
	}

	spdk_cpuset_zero(&g_vhost_core_mask);

	/* iterate threads instead of using SPDK_ENV_FOREACH_CORE to ensure that threads are really
	 * created.
	 */
	spdk_for_each_thread(vhost_setup_core_mask, init_cb, vhost_setup_core_mask_done);
	return;
out:
	init_cb(ret);
}

static void
vhost_fini(void *arg1)
{
	struct spdk_vhost_dev *vdev, *tmp;

	spdk_vhost_lock();
	vdev = spdk_vhost_dev_next(NULL);
	while (vdev != NULL) {
		tmp = spdk_vhost_dev_next(vdev);
		spdk_vhost_dev_remove(vdev);
		/* don't care if it fails, there's nothing we can do for now */
		vdev = tmp;
	}
	spdk_vhost_unlock();

	spdk_cpuset_zero(&g_vhost_core_mask);

	/* All devices are removed now. */
	sem_destroy(&g_dpdk_sem);

	g_fini_cpl_cb();
}

static void *
session_shutdown(void *arg)
{
	struct spdk_vhost_dev *vdev = NULL;

	TAILQ_FOREACH(vdev, &g_vhost_devices, tailq) {
		vhost_driver_unregister(vdev->path);
		vdev->registered = false;
	}

	SPDK_INFOLOG(vhost, "Exiting\n");
	spdk_thread_send_msg(g_vhost_init_thread, vhost_fini, NULL);
	return NULL;
}

void
spdk_vhost_fini(spdk_vhost_fini_cb fini_cb)
{
	pthread_t tid;
	int rc;

	assert(spdk_get_thread() == g_vhost_init_thread);
	g_fini_cpl_cb = fini_cb;

	/* rte_vhost API for removing sockets is not asynchronous. Since it may call SPDK
	 * ops for stopping a device or removing a connection, we need to call it from
	 * a separate thread to avoid deadlock.
	 */
	rc = pthread_create(&tid, NULL, &session_shutdown, NULL);
	if (rc < 0) {
		SPDK_ERRLOG("Failed to start session shutdown thread (%d): %s\n", rc, spdk_strerror(rc));
		abort();
	}
	pthread_detach(tid);
}

void
spdk_vhost_config_json(struct spdk_json_write_ctx *w)
{
	struct spdk_vhost_dev *vdev;
	uint32_t delay_base_us;
	uint32_t iops_threshold;

	spdk_json_write_array_begin(w);

	spdk_vhost_lock();
	vdev = spdk_vhost_dev_next(NULL);
	while (vdev != NULL) {
		vdev->backend->write_config_json(vdev, w);

		spdk_vhost_get_coalescing(vdev, &delay_base_us, &iops_threshold);
		if (delay_base_us) {
			spdk_json_write_object_begin(w);
			spdk_json_write_named_string(w, "method", "vhost_controller_set_coalescing");

			spdk_json_write_named_object_begin(w, "params");
			spdk_json_write_named_string(w, "ctrlr", vdev->name);
			spdk_json_write_named_uint32(w, "delay_base_us", delay_base_us);
			spdk_json_write_named_uint32(w, "iops_threshold", iops_threshold);
			spdk_json_write_object_end(w);

			spdk_json_write_object_end(w);
		}
		vdev = spdk_vhost_dev_next(vdev);
	}
	spdk_vhost_unlock();

	spdk_json_write_array_end(w);
}

SPDK_LOG_REGISTER_COMPONENT(vhost)
SPDK_LOG_REGISTER_COMPONENT(vhost_ring)