path: root/drivers/net/mlx4/mlx4_rxq.c

/*-
 *   BSD LICENSE
 *
 *   Copyright 2017 6WIND S.A.
 *   Copyright 2017 Mellanox
 *
 *   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 6WIND S.A. 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.
 */

/**
 * @file
 * Rx queues configuration for mlx4 driver.
 */

#include <assert.h>
#include <errno.h>
#include <stddef.h>
#include <stdint.h>
#include <string.h>

/* Verbs headers do not support -pedantic. */
#ifdef PEDANTIC
#pragma GCC diagnostic ignored "-Wpedantic"
#endif
#include <infiniband/mlx4dv.h>
#include <infiniband/verbs.h>
#ifdef PEDANTIC
#pragma GCC diagnostic error "-Wpedantic"
#endif

#include <rte_byteorder.h>
#include <rte_common.h>
#include <rte_errno.h>
#include <rte_ethdev.h>
#include <rte_flow.h>
#include <rte_malloc.h>
#include <rte_mbuf.h>
#include <rte_mempool.h>

#include "mlx4.h"
#include "mlx4_flow.h"
#include "mlx4_rxtx.h"
#include "mlx4_utils.h"

/**
 * Historical RSS hash key.
 *
 * This used to be the default for mlx4 in Linux before v3.19 switched to
 * generating random hash keys through netdev_rss_key_fill().
 *
 * It is used in this PMD for consistency with past DPDK releases but can
 * now be overridden through user configuration.
 *
 * Note: this is not const to work around API quirks.
 */
uint8_t
mlx4_rss_hash_key_default[MLX4_RSS_HASH_KEY_SIZE] = {
	0x2c, 0xc6, 0x81, 0xd1,
	0x5b, 0xdb, 0xf4, 0xf7,
	0xfc, 0xa2, 0x83, 0x19,
	0xdb, 0x1a, 0x3e, 0x94,
	0x6b, 0x9e, 0x38, 0xd9,
	0x2c, 0x9c, 0x03, 0xd1,
	0xad, 0x99, 0x44, 0xa7,
	0xd9, 0x56, 0x3d, 0x59,
	0x06, 0x3c, 0x25, 0xf3,
	0xfc, 0x1f, 0xdc, 0x2a,
};

/**
 * Obtain a RSS context with specified properties.
 *
 * Used when creating a flow rule targeting one or several Rx queues.
 *
 * If a matching RSS context already exists, it is returned with its
 * reference count incremented.
 *
 * @param priv
 *   Pointer to private structure.
 * @param fields
 *   Fields for RSS processing (Verbs format).
 * @param[in] key
 *   Hash key to use (whose size is exactly MLX4_RSS_HASH_KEY_SIZE).
 * @param queues
 *   Number of target queues.
 * @param[in] queue_id
 *   Target queues.
 *
 * @return
 *   Pointer to RSS context on success, NULL otherwise and rte_errno is set.
 */
struct mlx4_rss *
mlx4_rss_get(struct priv *priv, uint64_t fields,
	     uint8_t key[MLX4_RSS_HASH_KEY_SIZE],
	     uint16_t queues, const uint16_t queue_id[])
{
	struct mlx4_rss *rss;
	size_t queue_id_size = sizeof(queue_id[0]) * queues;

	LIST_FOREACH(rss, &priv->rss, next)
		if (fields == rss->fields &&
		    queues == rss->queues &&
		    !memcmp(key, rss->key, MLX4_RSS_HASH_KEY_SIZE) &&
		    !memcmp(queue_id, rss->queue_id, queue_id_size)) {
			++rss->refcnt;
			return rss;
		}
	rss = rte_malloc(__func__, offsetof(struct mlx4_rss, queue_id) +
			 queue_id_size, 0);
	if (!rss)
		goto error;
	*rss = (struct mlx4_rss){
		.priv = priv,
		.refcnt = 1,
		.usecnt = 0,
		.qp = NULL,
		.ind = NULL,
		.fields = fields,
		.queues = queues,
	};
	memcpy(rss->key, key, MLX4_RSS_HASH_KEY_SIZE);
	memcpy(rss->queue_id, queue_id, queue_id_size);
	LIST_INSERT_HEAD(&priv->rss, rss, next);
	return rss;
error:
	rte_errno = ENOMEM;
	return NULL;
}

/**
 * Release a RSS context instance.
 *
 * Used when destroying a flow rule targeting one or several Rx queues.
 *
 * This function decrements the reference count of the context and destroys
 * it after reaching 0. The context must have no users at this point; all
 * prior calls to mlx4_rss_attach() must have been followed by matching
 * calls to mlx4_rss_detach().
 *
 * @param rss
 *   RSS context to release.
 */
void
mlx4_rss_put(struct mlx4_rss *rss)
{
	assert(rss->refcnt);
	if (--rss->refcnt)
		return;
	assert(!rss->usecnt);
	assert(!rss->qp);
	assert(!rss->ind);
	LIST_REMOVE(rss, next);
	rte_free(rss);
}

/**
 * Attach a user to a RSS context instance.
 *
 * Used when the RSS QP and indirection table objects must be instantiated,
 * that is, when a flow rule must be enabled.
 *
 * This function increments the usage count of the context.
 *
 * @param rss
 *   RSS context to attach to.
 *
 * @return
 *   0 on success, a negative errno value otherwise and rte_errno is set.
 */
int
mlx4_rss_attach(struct mlx4_rss *rss)
{
	assert(rss->refcnt);
	if (rss->usecnt++) {
		assert(rss->qp);
		assert(rss->ind);
		return 0;
	}

	struct ibv_wq *ind_tbl[rss->queues];
	struct priv *priv = rss->priv;
	const char *msg;
	unsigned int i = 0;
	int ret;

	if (!rte_is_power_of_2(RTE_DIM(ind_tbl))) {
		ret = EINVAL;
		msg = "number of RSS queues must be a power of two";
		goto error;
	}
	for (i = 0; i != RTE_DIM(ind_tbl); ++i) {
		uint16_t id = rss->queue_id[i];
		struct rxq *rxq = NULL;

		if (id < priv->dev->data->nb_rx_queues)
			rxq = priv->dev->data->rx_queues[id];
		if (!rxq) {
			ret = EINVAL;
			msg = "RSS target queue is not configured";
			goto error;
		}
		ret = mlx4_rxq_attach(rxq);
		if (ret) {
			ret = -ret;
			msg = "unable to attach RSS target queue";
			goto error;
		}
		ind_tbl[i] = rxq->wq;
	}
	rss->ind = ibv_create_rwq_ind_table
		(priv->ctx,
		 &(struct ibv_rwq_ind_table_init_attr){
			.log_ind_tbl_size = rte_log2_u32(RTE_DIM(ind_tbl)),
			.ind_tbl = ind_tbl,
			.comp_mask = 0,
		 });
	if (!rss->ind) {
		ret = errno ? errno : EINVAL;
		msg = "RSS indirection table creation failure";
		goto error;
	}
	rss->qp = ibv_create_qp_ex
		(priv->ctx,
		 &(struct ibv_qp_init_attr_ex){
			.comp_mask = (IBV_QP_INIT_ATTR_PD |
				      IBV_QP_INIT_ATTR_RX_HASH |
				      IBV_QP_INIT_ATTR_IND_TABLE),
			.qp_type = IBV_QPT_RAW_PACKET,
			.pd = priv->pd,
			.rwq_ind_tbl = rss->ind,
			.rx_hash_conf = {
				.rx_hash_function = IBV_RX_HASH_FUNC_TOEPLITZ,
				.rx_hash_key_len = MLX4_RSS_HASH_KEY_SIZE,
				.rx_hash_key = rss->key,
				.rx_hash_fields_mask = rss->fields,
			},
		 });
	if (!rss->qp) {
		ret = errno ? errno : EINVAL;
		msg = "RSS hash QP creation failure";
		goto error;
	}
	ret = ibv_modify_qp
		(rss->qp,
		 &(struct ibv_qp_attr){
			.qp_state = IBV_QPS_INIT,
			.port_num = priv->port,
		 },
		 IBV_QP_STATE | IBV_QP_PORT);
	if (ret) {
		msg = "failed to switch RSS hash QP to INIT state";
		goto error;
	}
	ret = ibv_modify_qp
		(rss->qp,
		 &(struct ibv_qp_attr){
			.qp_state = IBV_QPS_RTR,
		 },
		 IBV_QP_STATE);
	if (ret) {
		msg = "failed to switch RSS hash QP to RTR state";
		goto error;
	}
	return 0;
error:
	if (rss->qp) {
		claim_zero(ibv_destroy_qp(rss->qp));
		rss->qp = NULL;
	}
	if (rss->ind) {
		claim_zero(ibv_destroy_rwq_ind_table(rss->ind));
		rss->ind = NULL;
	}
	while (i--)
		mlx4_rxq_detach(priv->dev->data->rx_queues[rss->queue_id[i]]);
	ERROR("mlx4: %s", msg);
	--rss->usecnt;
	rte_errno = ret;
	return -ret;
}

/**
 * Detach a user from a RSS context instance.
 *
 * Used when disabling (not destroying) a flow rule.
 *
 * This function decrements the usage count of the context and destroys
 * usage resources after reaching 0.
 *
 * @param rss
 *   RSS context to detach from.
 */
void
mlx4_rss_detach(struct mlx4_rss *rss)
{
	struct priv *priv = rss->priv;
	unsigned int i;

	assert(rss->refcnt);
	assert(rss->qp);
	assert(rss->ind);
	if (--rss->usecnt)
		return;
	claim_zero(ibv_destroy_qp(rss->qp));
	rss->qp = NULL;
	claim_zero(ibv_destroy_rwq_ind_table(rss->ind));
	rss->ind = NULL;
	for (i = 0; i != rss->queues; ++i)
		mlx4_rxq_detach(priv->dev->data->rx_queues[rss->queue_id[i]]);
}

/**
 * Initialize common RSS context resources.
 *
 * Because ConnectX-3 hardware limitations require a fixed order in the
 * indirection table, WQs must be allocated sequentially to be part of a
 * common RSS context.
 *
 * Since a newly created WQ cannot be moved to a different context, this
 * function allocates them all at once, one for each configured Rx queue,
 * as well as all related resources (CQs and mbufs).
 *
 * This must therefore be done before creating any Rx flow rules relying on
 * indirection tables.
 *
 * @param priv
 *   Pointer to private structure.
 *
 * @return
 *   0 on success, a negative errno value otherwise and rte_errno is set.
 */
int
mlx4_rss_init(struct priv *priv)
{
	struct rte_eth_dev *dev = priv->dev;
	uint8_t log2_range = rte_log2_u32(dev->data->nb_rx_queues);
	uint32_t wq_num_prev = 0;
	const char *msg;
	unsigned int i;
	int ret;

	/* Prepare range for RSS contexts before creating the first WQ. */
	ret = mlx4dv_set_context_attr(priv->ctx,
				      MLX4DV_SET_CTX_ATTR_LOG_WQS_RANGE_SZ,
				      &log2_range);
	if (ret) {
		ERROR("cannot set up range size for RSS context to %u"
		      " (for %u Rx queues), error: %s",
		      1 << log2_range, dev->data->nb_rx_queues, strerror(ret));
		rte_errno = ret;
		return -ret;
	}
	for (i = 0; i != priv->dev->data->nb_rx_queues; ++i) {
		struct rxq *rxq = priv->dev->data->rx_queues[i];
		struct ibv_cq *cq;
		struct ibv_wq *wq;
		uint32_t wq_num;

		/* Attach the configured Rx queues. */
		if (rxq) {
			assert(!rxq->usecnt);
			ret = mlx4_rxq_attach(rxq);
			if (!ret) {
				wq_num = rxq->wq->wq_num;
				goto wq_num_check;
			}
			ret = -ret;
			msg = "unable to create Rx queue resources";
			goto error;
		}
		/*
		 * WQs are temporarily allocated for unconfigured Rx queues
		 * to maintain proper index alignment in indirection table
		 * by skipping unused WQ numbers.
		 *
		 * The reason this works at all even though these WQs are
		 * immediately destroyed is that WQNs are allocated
		 * sequentially and are guaranteed to never be reused in the
		 * same context by the underlying implementation.
		 */
		cq = ibv_create_cq(priv->ctx, 1, NULL, NULL, 0);
		if (!cq) {
			ret = ENOMEM;
			msg = "placeholder CQ creation failure";
			goto error;
		}
		wq = ibv_create_wq
			(priv->ctx,
			 &(struct ibv_wq_init_attr){
				.wq_type = IBV_WQT_RQ,
				.max_wr = 1,
				.max_sge = 1,
				.pd = priv->pd,
				.cq = cq,
			 });
		if (wq) {
			wq_num = wq->wq_num;
			claim_zero(ibv_destroy_wq(wq));
		} else {
			wq_num = 0; /* Shut up GCC 4.8 warnings. */
		}
		claim_zero(ibv_destroy_cq(cq));
		if (!wq) {
			ret = ENOMEM;
			msg = "placeholder WQ creation failure";
			goto error;
		}
wq_num_check:
		/*
		 * While guaranteed by the implementation, make sure WQ
		 * numbers are really sequential (as the saying goes,
		 * trust, but verify).
		 */
		if (i && wq_num - wq_num_prev != 1) {
			if (rxq)
				mlx4_rxq_detach(rxq);
			ret = ERANGE;
			msg = "WQ numbers are not sequential";
			goto error;
		}
		wq_num_prev = wq_num;
	}
	return 0;
error:
	ERROR("cannot initialize common RSS resources (queue %u): %s: %s",
	      i, msg, strerror(ret));
	while (i--) {
		struct rxq *rxq = priv->dev->data->rx_queues[i];

		if (rxq)
			mlx4_rxq_detach(rxq);
	}
	rte_errno = ret;
	return -ret;
}

/**
 * Release common RSS context resources.
 *
 * As the reverse of mlx4_rss_init(), this must be done after removing all
 * flow rules relying on indirection tables.
 *
 * @param priv
 *   Pointer to private structure.
 */
void
mlx4_rss_deinit(struct priv *priv)
{
	unsigned int i;

	for (i = 0; i != priv->dev->data->nb_rx_queues; ++i) {
		struct rxq *rxq = priv->dev->data->rx_queues[i];

		if (rxq) {
			assert(rxq->usecnt == 1);
			mlx4_rxq_detach(rxq);
		}
	}
}

/**
 * Attach a user to a Rx queue.
 *
 * Used when the resources of an Rx queue must be instantiated for it to
 * become in a usable state.
 *
 * This function increments the usage count of the Rx queue.
 *
 * @param rxq
 *   Pointer to Rx queue structure.
 *
 * @return
 *   0 on success, negative errno value otherwise and rte_errno is set.
 */
int
mlx4_rxq_attach(struct rxq *rxq)
{
	if (rxq->usecnt++) {
		assert(rxq->cq);
		assert(rxq->wq);
		assert(rxq->wqes);
		assert(rxq->rq_db);
		return 0;
	}

	struct priv *priv = rxq->priv;
	const uint32_t elts_n = 1 << rxq->elts_n;
	const uint32_t sges_n = 1 << rxq->sges_n;
	struct rte_mbuf *(*elts)[elts_n] = rxq->elts;
	struct mlx4dv_obj mlxdv;
	struct mlx4dv_rwq dv_rwq;
	struct mlx4dv_cq dv_cq = { .comp_mask = MLX4DV_CQ_MASK_UAR, };
	const char *msg;
	struct ibv_cq *cq = NULL;
	struct ibv_wq *wq = NULL;
	volatile struct mlx4_wqe_data_seg (*wqes)[];
	unsigned int i;
	int ret;

	assert(rte_is_power_of_2(elts_n));
	cq = ibv_create_cq(priv->ctx, elts_n / sges_n, NULL, rxq->channel, 0);
	if (!cq) {
		ret = ENOMEM;
		msg = "CQ creation failure";
		goto error;
	}
	wq = ibv_create_wq
		(priv->ctx,
		 &(struct ibv_wq_init_attr){
			.wq_type = IBV_WQT_RQ,
			.max_wr = elts_n / sges_n,
			.max_sge = sges_n,
			.pd = priv->pd,
			.cq = cq,
		 });
	if (!wq) {
		ret = errno ? errno : EINVAL;
		msg = "WQ creation failure";
		goto error;
	}
	ret = ibv_modify_wq
		(wq,
		 &(struct ibv_wq_attr){
			.attr_mask = IBV_WQ_ATTR_STATE,
			.wq_state = IBV_WQS_RDY,
		 });
	if (ret) {
		msg = "WQ state change to IBV_WQS_RDY failed";
		goto error;
	}
	/* Retrieve device queue information. */
	mlxdv.cq.in = cq;
	mlxdv.cq.out = &dv_cq;
	mlxdv.rwq.in = wq;
	mlxdv.rwq.out = &dv_rwq;
	ret = mlx4dv_init_obj(&mlxdv, MLX4DV_OBJ_RWQ | MLX4DV_OBJ_CQ);
	if (ret) {
		msg = "failed to obtain device information from WQ/CQ objects";
		goto error;
	}
	wqes = (volatile struct mlx4_wqe_data_seg (*)[])
		((uintptr_t)dv_rwq.buf.buf + dv_rwq.rq.offset);
	for (i = 0; i != RTE_DIM(*elts); ++i) {
		volatile struct mlx4_wqe_data_seg *scat = &(*wqes)[i];
		struct rte_mbuf *buf = rte_pktmbuf_alloc(rxq->mp);

		if (buf == NULL) {
			while (i--) {
				rte_pktmbuf_free_seg((*elts)[i]);
				(*elts)[i] = NULL;
			}
			ret = ENOMEM;
			msg = "cannot allocate mbuf";
			goto error;
		}
		/* Headroom is reserved by rte_pktmbuf_alloc(). */
		assert(buf->data_off == RTE_PKTMBUF_HEADROOM);
		/* Buffer is supposed to be empty. */
		assert(rte_pktmbuf_data_len(buf) == 0);
		assert(rte_pktmbuf_pkt_len(buf) == 0);
		/* Only the first segment keeps headroom. */
		if (i % sges_n)
			buf->data_off = 0;
		buf->port = rxq->port_id;
		buf->data_len = rte_pktmbuf_tailroom(buf);
		buf->pkt_len = rte_pktmbuf_tailroom(buf);
		buf->nb_segs = 1;
		*scat = (struct mlx4_wqe_data_seg){
			.addr = rte_cpu_to_be_64(rte_pktmbuf_mtod(buf,
								  uintptr_t)),
			.byte_count = rte_cpu_to_be_32(buf->data_len),
			.lkey = rte_cpu_to_be_32(rxq->mr->lkey),
		};
		(*elts)[i] = buf;
	}
	DEBUG("%p: allocated and configured %u segments (max %u packets)",
	      (void *)rxq, elts_n, elts_n / sges_n);
	rxq->cq = cq;
	rxq->wq = wq;
	rxq->wqes = wqes;
	rxq->rq_db = dv_rwq.rdb;
	rxq->mcq.buf = dv_cq.buf.buf;
	rxq->mcq.cqe_cnt = dv_cq.cqe_cnt;
	rxq->mcq.set_ci_db = dv_cq.set_ci_db;
	rxq->mcq.cqe_64 = (dv_cq.cqe_size & 64) ? 1 : 0;
	rxq->mcq.arm_db = dv_cq.arm_db;
	rxq->mcq.arm_sn = dv_cq.arm_sn;
	rxq->mcq.cqn = dv_cq.cqn;
	rxq->mcq.cq_uar = dv_cq.cq_uar;
	rxq->mcq.cq_db_reg = (uint8_t *)dv_cq.cq_uar + MLX4_CQ_DOORBELL;
	/* Update doorbell counter. */
	rxq->rq_ci = elts_n / sges_n;
	rte_wmb();
	*rxq->rq_db = rte_cpu_to_be_32(rxq->rq_ci);
	return 0;
error:
	if (wq)
		claim_zero(ibv_destroy_wq(wq));
	if (cq)
		claim_zero(ibv_destroy_cq(cq));
	rte_errno = ret;
	ERROR("error while attaching Rx queue %p: %s: %s",
	      (void *)rxq, msg, strerror(ret));
	return -ret;
}

/**
 * Detach a user from a Rx queue.
 *
 * This function decrements the usage count of the Rx queue and destroys
 * usage resources after reaching 0.
 *
 * @param rxq
 *   Pointer to Rx queue structure.
 */
void
mlx4_rxq_detach(struct rxq *rxq)
{
	unsigned int i;
	struct rte_mbuf *(*elts)[1 << rxq->elts_n] = rxq->elts;

	if (--rxq->usecnt)
		return;
	rxq->rq_ci = 0;
	memset(&rxq->mcq, 0, sizeof(rxq->mcq));
	rxq->rq_db = NULL;
	rxq->wqes = NULL;
	claim_zero(ibv_destroy_wq(rxq->wq));
	rxq->wq = NULL;
	claim_zero(ibv_destroy_cq(rxq->cq));
	rxq->cq = NULL;
	DEBUG("%p: freeing Rx queue elements", (void *)rxq);
	for (i = 0; (i != RTE_DIM(*elts)); ++i) {
		if (!(*elts)[i])
			continue;
		rte_pktmbuf_free_seg((*elts)[i]);
		(*elts)[i] = NULL;
	}
}

/**
 * DPDK callback to configure a Rx queue.
 *
 * @param dev
 *   Pointer to Ethernet device structure.
 * @param idx
 *   Rx queue index.
 * @param desc
 *   Number of descriptors to configure in queue.
 * @param socket
 *   NUMA socket on which memory must be allocated.
 * @param[in] conf
 *   Thresholds parameters.
 * @param mp
 *   Memory pool for buffer allocations.
 *
 * @return
 *   0 on success, negative errno value otherwise and rte_errno is set.
 */
int
mlx4_rx_queue_setup(struct rte_eth_dev *dev, uint16_t idx, uint16_t desc,
		    unsigned int socket, const struct rte_eth_rxconf *conf,
		    struct rte_mempool *mp)
{
	struct priv *priv = dev->data->dev_private;
	uint32_t mb_len = rte_pktmbuf_data_room_size(mp);
	struct rte_mbuf *(*elts)[rte_align32pow2(desc)];
	struct rxq *rxq;
	struct mlx4_malloc_vec vec[] = {
		{
			.align = RTE_CACHE_LINE_SIZE,
			.size = sizeof(*rxq),
			.addr = (void **)&rxq,
		},
		{
			.align = RTE_CACHE_LINE_SIZE,
			.size = sizeof(*elts),
			.addr = (void **)&elts,
		},
	};
	int ret;

	(void)conf; /* Thresholds configuration (ignored). */
	DEBUG("%p: configuring queue %u for %u descriptors",
	      (void *)dev, idx, desc);
	if (idx >= dev->data->nb_rx_queues) {
		rte_errno = EOVERFLOW;
		ERROR("%p: queue index out of range (%u >= %u)",
		      (void *)dev, idx, dev->data->nb_rx_queues);
		return -rte_errno;
	}
	rxq = dev->data->rx_queues[idx];
	if (rxq) {
		rte_errno = EEXIST;
		ERROR("%p: Rx queue %u already configured, release it first",
		      (void *)dev, idx);
		return -rte_errno;
	}
	if (!desc) {
		rte_errno = EINVAL;
		ERROR("%p: invalid number of Rx descriptors", (void *)dev);
		return -rte_errno;
	}
	if (desc != RTE_DIM(*elts)) {
		desc = RTE_DIM(*elts);
		WARN("%p: increased number of descriptors in Rx queue %u"
		     " to the next power of two (%u)",
		     (void *)dev, idx, desc);
	}
	/* Allocate and initialize Rx queue. */
	mlx4_zmallocv_socket("RXQ", vec, RTE_DIM(vec), socket);
	if (!rxq) {
		ERROR("%p: unable to allocate queue index %u",
		      (void *)dev, idx);
		return -rte_errno;
	}
	*rxq = (struct rxq){
		.priv = priv,
		.mp = mp,
		.port_id = dev->data->port_id,
		.sges_n = 0,
		.elts_n = rte_log2_u32(desc),
		.elts = elts,
		/* Toggle Rx checksum offload if hardware supports it. */
		.csum = (priv->hw_csum &&
			 dev->data->dev_conf.rxmode.hw_ip_checksum),
		.csum_l2tun = (priv->hw_csum_l2tun &&
			       dev->data->dev_conf.rxmode.hw_ip_checksum),
		.l2tun_offload = priv->hw_csum_l2tun,
		.stats = {
			.idx = idx,
		},
		.socket = socket,
	};
	/* Enable scattered packets support for this queue if necessary. */
	assert(mb_len >= RTE_PKTMBUF_HEADROOM);
	if (dev->data->dev_conf.rxmode.max_rx_pkt_len <=
	    (mb_len - RTE_PKTMBUF_HEADROOM)) {
		;
	} else if (dev->data->dev_conf.rxmode.enable_scatter) {
		uint32_t size =
			RTE_PKTMBUF_HEADROOM +
			dev->data->dev_conf.rxmode.max_rx_pkt_len;
		uint32_t sges_n;

		/*
		 * Determine the number of SGEs needed for a full packet
		 * and round it to the next power of two.
		 */
		sges_n = rte_log2_u32((size / mb_len) + !!(size % mb_len));
		rxq->sges_n = sges_n;
		/* Make sure sges_n did not overflow. */
		size = mb_len * (1 << rxq->sges_n);
		size -= RTE_PKTMBUF_HEADROOM;
		if (size < dev->data->dev_conf.rxmode.max_rx_pkt_len) {
			rte_errno = EOVERFLOW;
			ERROR("%p: too many SGEs (%u) needed to handle"
			      " requested maximum packet size %u",
			      (void *)dev,
			      1 << sges_n,
			      dev->data->dev_conf.rxmode.max_rx_pkt_len);
			goto error;
		}
	} else {
		WARN("%p: the requested maximum Rx packet size (%u) is"
		     " larger than a single mbuf (%u) and scattered"
		     " mode has not been requested",
		     (void *)dev,
		     dev->data->dev_conf.rxmode.max_rx_pkt_len,
		     mb_len - RTE_PKTMBUF_HEADROOM);
	}
	DEBUG("%p: maximum number of segments per packet: %u",
	      (void *)dev, 1 << rxq->sges_n);
	if (desc % (1 << rxq->sges_n)) {
		rte_errno = EINVAL;
		ERROR("%p: number of Rx queue descriptors (%u) is not a"
		      " multiple of maximum segments per packet (%u)",
		      (void *)dev,
		      desc,
		      1 << rxq->sges_n);
		goto error;
	}
	/* Use the entire Rx mempool as the memory region. */
	rxq->mr = mlx4_mr_get(priv, mp);
	if (!rxq->mr) {
		ERROR("%p: MR creation failure: %s",
		      (void *)dev, strerror(rte_errno));
		goto error;
	}
	if (dev->data->dev_conf.intr_conf.rxq) {
		rxq->channel = ibv_create_comp_channel(priv->ctx);
		if (rxq->channel == NULL) {
			rte_errno = ENOMEM;
			ERROR("%p: Rx interrupt completion channel creation"
			      " failure: %s",
			      (void *)dev, strerror(rte_errno));
			goto error;
		}
		if (mlx4_fd_set_non_blocking(rxq->channel->fd) < 0) {
			ERROR("%p: unable to make Rx interrupt completion"
			      " channel non-blocking: %s",
			      (void *)dev, strerror(rte_errno));
			goto error;
		}
	}
	DEBUG("%p: adding Rx queue %p to list", (void *)dev, (void *)rxq);
	dev->data->rx_queues[idx] = rxq;
	return 0;
error:
	dev->data->rx_queues[idx] = NULL;
	ret = rte_errno;
	mlx4_rx_queue_release(rxq);
	rte_errno = ret;
	assert(rte_errno > 0);
	return -rte_errno;
}

/**
 * DPDK callback to release a Rx queue.
 *
 * @param dpdk_rxq
 *   Generic Rx queue pointer.
 */
void
mlx4_rx_queue_release(void *dpdk_rxq)
{
	struct rxq *rxq = (struct rxq *)dpdk_rxq;
	struct priv *priv;
	unsigned int i;

	if (rxq == NULL)
		return;
	priv = rxq->priv;
	for (i = 0; i != priv->dev->data->nb_rx_queues; ++i)
		if (priv->dev->data->rx_queues[i] == rxq) {
			DEBUG("%p: removing Rx queue %p from list",
			      (void *)priv->dev, (void *)rxq);
			priv->dev->data->rx_queues[i] = NULL;
			break;
		}
	assert(!rxq->cq);
	assert(!rxq->wq);
	assert(!rxq->wqes);
	assert(!rxq->rq_db);
	if (rxq->channel)
		claim_zero(ibv_destroy_comp_channel(rxq->channel));
	if (rxq->mr)
		mlx4_mr_put(rxq->mr);
	rte_free(rxq);
}