smc_llc.c

// SPDX-License-Identifier: GPL-2.0
/*
 *  Shared Memory Communications over RDMA (SMC-R) and RoCE
 *
 *  Link Layer Control (LLC)
 *
 *  Copyright IBM Corp. 2016
 *
 *  Author(s):  Klaus Wacker <Klaus.Wacker@de.ibm.com>
 *              Ursula Braun <ubraun@linux.vnet.ibm.com>
 */

#include <net/tcp.h>
#include <rdma/ib_verbs.h>

#include "smc.h"
#include "smc_core.h"
#include "smc_clc.h"
#include "smc_llc.h"
#include "smc_pnet.h"

#define SMC_LLC_DATA_LEN		40

struct smc_llc_hdr {
	struct smc_wr_rx_hdr common;
	u8 length;	/* 44 */
#if defined(__BIG_ENDIAN_BITFIELD)
	u8 reserved:4,
	   add_link_rej_rsn:4;
#elif defined(__LITTLE_ENDIAN_BITFIELD)
	u8 add_link_rej_rsn:4,
	   reserved:4;
#endif
	u8 flags;
};

#define SMC_LLC_FLAG_NO_RMBE_EYEC	0x03

struct smc_llc_msg_confirm_link {	/* type 0x01 */
	struct smc_llc_hdr hd;
	u8 sender_mac[ETH_ALEN];
	u8 sender_gid[SMC_GID_SIZE];
	u8 sender_qp_num[3];
	u8 link_num;
	u8 link_uid[SMC_LGR_ID_SIZE];
	u8 max_links;
	u8 reserved[9];
};

#define SMC_LLC_FLAG_ADD_LNK_REJ	0x40
#define SMC_LLC_REJ_RSN_NO_ALT_PATH	1

#define SMC_LLC_ADD_LNK_MAX_LINKS	2

struct smc_llc_msg_add_link {		/* type 0x02 */
	struct smc_llc_hdr hd;
	u8 sender_mac[ETH_ALEN];
	u8 reserved2[2];
	u8 sender_gid[SMC_GID_SIZE];
	u8 sender_qp_num[3];
	u8 link_num;
#if defined(__BIG_ENDIAN_BITFIELD)
	u8 reserved3 : 4,
	   qp_mtu   : 4;
#elif defined(__LITTLE_ENDIAN_BITFIELD)
	u8 qp_mtu   : 4,
	   reserved3 : 4;
#endif
	u8 initial_psn[3];
	u8 reserved[8];
};

struct smc_llc_msg_add_link_cont_rt {
	__be32 rmb_key;
	__be32 rmb_key_new;
	__be64 rmb_vaddr_new;
};

#define SMC_LLC_RKEYS_PER_CONT_MSG	2

struct smc_llc_msg_add_link_cont {	/* type 0x03 */
	struct smc_llc_hdr hd;
	u8 link_num;
	u8 num_rkeys;
	u8 reserved2[2];
	struct smc_llc_msg_add_link_cont_rt rt[SMC_LLC_RKEYS_PER_CONT_MSG];
	u8 reserved[4];
} __packed;			/* format defined in RFC7609 */

#define SMC_LLC_FLAG_DEL_LINK_ALL	0x40
#define SMC_LLC_FLAG_DEL_LINK_ORDERLY	0x20

struct smc_llc_msg_del_link {		/* type 0x04 */
	struct smc_llc_hdr hd;
	u8 link_num;
	__be32 reason;
	u8 reserved[35];
} __packed;			/* format defined in RFC7609 */

struct smc_llc_msg_test_link {		/* type 0x07 */
	struct smc_llc_hdr hd;
	u8 user_data[16];
	u8 reserved[24];
};

struct smc_rmb_rtoken {
	union {
		u8 num_rkeys;	/* first rtoken byte of CONFIRM LINK msg */
				/* is actually the num of rtokens, first */
				/* rtoken is always for the current link */
		u8 link_id;	/* link id of the rtoken */
	};
	__be32 rmb_key;
	__be64 rmb_vaddr;
} __packed;			/* format defined in RFC7609 */

#define SMC_LLC_RKEYS_PER_MSG	3

struct smc_llc_msg_confirm_rkey {	/* type 0x06 */
	struct smc_llc_hdr hd;
	struct smc_rmb_rtoken rtoken[SMC_LLC_RKEYS_PER_MSG];
	u8 reserved;
};

#define SMC_LLC_DEL_RKEY_MAX	8
#define SMC_LLC_FLAG_RKEY_RETRY	0x10
#define SMC_LLC_FLAG_RKEY_NEG	0x20

struct smc_llc_msg_delete_rkey {	/* type 0x09 */
	struct smc_llc_hdr hd;
	u8 num_rkeys;
	u8 err_mask;
	u8 reserved[2];
	__be32 rkey[8];
	u8 reserved2[4];
};

union smc_llc_msg {
	struct smc_llc_msg_confirm_link confirm_link;
	struct smc_llc_msg_add_link add_link;
	struct smc_llc_msg_add_link_cont add_link_cont;
	struct smc_llc_msg_del_link delete_link;

	struct smc_llc_msg_confirm_rkey confirm_rkey;
	struct smc_llc_msg_delete_rkey delete_rkey;

	struct smc_llc_msg_test_link test_link;
	struct {
		struct smc_llc_hdr hdr;
		u8 data[SMC_LLC_DATA_LEN];
	} raw;
};

#define SMC_LLC_FLAG_RESP		0x80

struct smc_llc_qentry {
	struct list_head list;
	struct smc_link *link;
	union smc_llc_msg msg;
};

struct smc_llc_qentry *smc_llc_flow_qentry_clr(struct smc_llc_flow *flow)
{
	struct smc_llc_qentry *qentry = flow->qentry;

	flow->qentry = NULL;
	return qentry;
}

void smc_llc_flow_qentry_del(struct smc_llc_flow *flow)
{
	struct smc_llc_qentry *qentry;

	if (flow->qentry) {
		qentry = flow->qentry;
		flow->qentry = NULL;
		kfree(qentry);
	}
}

static inline void smc_llc_flow_qentry_set(struct smc_llc_flow *flow,
					   struct smc_llc_qentry *qentry)
{
	flow->qentry = qentry;
}

/* try to start a new llc flow, initiated by an incoming llc msg */
static bool smc_llc_flow_start(struct smc_llc_flow *flow,
			       struct smc_llc_qentry *qentry)
{
	struct smc_link_group *lgr = qentry->link->lgr;

	spin_lock_bh(&lgr->llc_flow_lock);
	if (flow->type) {
		/* a flow is already active */
		if ((qentry->msg.raw.hdr.common.type == SMC_LLC_ADD_LINK ||
		     qentry->msg.raw.hdr.common.type == SMC_LLC_DELETE_LINK) &&
		    !lgr->delayed_event) {
			lgr->delayed_event = qentry;
		} else {
			/* forget this llc request */
			kfree(qentry);
		}
		spin_unlock_bh(&lgr->llc_flow_lock);
		return false;
	}
	switch (qentry->msg.raw.hdr.common.type) {
	case SMC_LLC_ADD_LINK:
		flow->type = SMC_LLC_FLOW_ADD_LINK;
		break;
	case SMC_LLC_DELETE_LINK:
		flow->type = SMC_LLC_FLOW_DEL_LINK;
		break;
	case SMC_LLC_CONFIRM_RKEY:
	case SMC_LLC_DELETE_RKEY:
		flow->type = SMC_LLC_FLOW_RKEY;
		break;
	default:
		flow->type = SMC_LLC_FLOW_NONE;
	}
	if (qentry == lgr->delayed_event)
		lgr->delayed_event = NULL;
	spin_unlock_bh(&lgr->llc_flow_lock);
	smc_llc_flow_qentry_set(flow, qentry);
	return true;
}

/* start a new local llc flow, wait till current flow finished */
int smc_llc_flow_initiate(struct smc_link_group *lgr,
			  enum smc_llc_flowtype type)
{
	enum smc_llc_flowtype allowed_remote = SMC_LLC_FLOW_NONE;
	int rc;

	/* all flows except confirm_rkey and delete_rkey are exclusive,
	 * confirm/delete rkey flows can run concurrently (local and remote)
	 */
	if (type == SMC_LLC_FLOW_RKEY)
		allowed_remote = SMC_LLC_FLOW_RKEY;
again:
	if (list_empty(&lgr->list))
		return -ENODEV;
	spin_lock_bh(&lgr->llc_flow_lock);
	if (lgr->llc_flow_lcl.type == SMC_LLC_FLOW_NONE &&
	    (lgr->llc_flow_rmt.type == SMC_LLC_FLOW_NONE ||
	     lgr->llc_flow_rmt.type == allowed_remote)) {
		lgr->llc_flow_lcl.type = type;
		spin_unlock_bh(&lgr->llc_flow_lock);
		return 0;
	}
	spin_unlock_bh(&lgr->llc_flow_lock);
	rc = wait_event_interruptible_timeout(lgr->llc_waiter,
			(lgr->llc_flow_lcl.type == SMC_LLC_FLOW_NONE &&
			 (lgr->llc_flow_rmt.type == SMC_LLC_FLOW_NONE ||
			  lgr->llc_flow_rmt.type == allowed_remote)),
			SMC_LLC_WAIT_TIME);
	if (!rc)
		return -ETIMEDOUT;
	goto again;
}

/* finish the current llc flow */
void smc_llc_flow_stop(struct smc_link_group *lgr, struct smc_llc_flow *flow)
{
	spin_lock_bh(&lgr->llc_flow_lock);
	memset(flow, 0, sizeof(*flow));
	flow->type = SMC_LLC_FLOW_NONE;
	spin_unlock_bh(&lgr->llc_flow_lock);
	if (!list_empty(&lgr->list) && lgr->delayed_event &&
	    flow == &lgr->llc_flow_lcl)
		schedule_work(&lgr->llc_event_work);
	else
		wake_up_interruptible(&lgr->llc_waiter);
}

/* lnk is optional and used for early wakeup when link goes down, useful in
 * cases where we wait for a response on the link after we sent a request
 */
struct smc_llc_qentry *smc_llc_wait(struct smc_link_group *lgr,
				    struct smc_link *lnk,
				    int time_out, u8 exp_msg)
{
	struct smc_llc_flow *flow = &lgr->llc_flow_lcl;

	wait_event_interruptible_timeout(lgr->llc_waiter,
					 (flow->qentry ||
					  (lnk && !smc_link_usable(lnk)) ||
					  list_empty(&lgr->list)),
					 time_out);
	if (!flow->qentry ||
	    (lnk && !smc_link_usable(lnk)) || list_empty(&lgr->list)) {
		smc_llc_flow_qentry_del(flow);
		goto out;
	}
	if (exp_msg && flow->qentry->msg.raw.hdr.common.type != exp_msg) {
		if (exp_msg == SMC_LLC_ADD_LINK &&
		    flow->qentry->msg.raw.hdr.common.type ==
		    SMC_LLC_DELETE_LINK) {
			/* flow_start will delay the unexpected msg */
			smc_llc_flow_start(&lgr->llc_flow_lcl,
					   smc_llc_flow_qentry_clr(flow));
			return NULL;
		}
		smc_llc_flow_qentry_del(flow);
	}
out:
	return flow->qentry;
}

/********************************** send *************************************/

struct smc_llc_tx_pend {
};

/* handler for send/transmission completion of an LLC msg */
static void smc_llc_tx_handler(struct smc_wr_tx_pend_priv *pend,
			       struct smc_link *link,
			       enum ib_wc_status wc_status)
{
	/* future work: handle wc_status error for recovery and failover */
}

/**
 * smc_llc_add_pending_send() - add LLC control message to pending WQE transmits
 * @link: Pointer to SMC link used for sending LLC control message.
 * @wr_buf: Out variable returning pointer to work request payload buffer.
 * @pend: Out variable returning pointer to private pending WR tracking.
 *	  It's the context the transmit complete handler will get.
 *
 * Reserves and pre-fills an entry for a pending work request send/tx.
 * Used by mid-level smc_llc_send_msg() to prepare for later actual send/tx.
 * Can sleep due to smc_get_ctrl_buf (if not in softirq context).
 *
 * Return: 0 on success, otherwise an error value.
 */
static int smc_llc_add_pending_send(struct smc_link *link,
				    struct smc_wr_buf **wr_buf,
				    struct smc_wr_tx_pend_priv **pend)
{
	int rc;

	rc = smc_wr_tx_get_free_slot(link, smc_llc_tx_handler, wr_buf, NULL,
				     pend);
	if (rc < 0)
		return rc;
	BUILD_BUG_ON_MSG(
		sizeof(union smc_llc_msg) > SMC_WR_BUF_SIZE,
		"must increase SMC_WR_BUF_SIZE to at least sizeof(struct smc_llc_msg)");
	BUILD_BUG_ON_MSG(
		sizeof(union smc_llc_msg) != SMC_WR_TX_SIZE,
		"must adapt SMC_WR_TX_SIZE to sizeof(struct smc_llc_msg); if not all smc_wr upper layer protocols use the same message size any more, must start to set link->wr_tx_sges[i].length on each individual smc_wr_tx_send()");
	BUILD_BUG_ON_MSG(
		sizeof(struct smc_llc_tx_pend) > SMC_WR_TX_PEND_PRIV_SIZE,
		"must increase SMC_WR_TX_PEND_PRIV_SIZE to at least sizeof(struct smc_llc_tx_pend)");
	return 0;
}

/* high-level API to send LLC confirm link */
int smc_llc_send_confirm_link(struct smc_link *link,
			      enum smc_llc_reqresp reqresp)
{
	struct smc_link_group *lgr = smc_get_lgr(link);
	struct smc_llc_msg_confirm_link *confllc;
	struct smc_wr_tx_pend_priv *pend;
	struct smc_wr_buf *wr_buf;
	int rc;

	rc = smc_llc_add_pending_send(link, &wr_buf, &pend);
	if (rc)
		return rc;
	confllc = (struct smc_llc_msg_confirm_link *)wr_buf;
	memset(confllc, 0, sizeof(*confllc));
	confllc->hd.common.type = SMC_LLC_CONFIRM_LINK;
	confllc->hd.length = sizeof(struct smc_llc_msg_confirm_link);
	confllc->hd.flags |= SMC_LLC_FLAG_NO_RMBE_EYEC;
	if (reqresp == SMC_LLC_RESP)
		confllc->hd.flags |= SMC_LLC_FLAG_RESP;
	memcpy(confllc->sender_mac, link->smcibdev->mac[link->ibport - 1],
	       ETH_ALEN);
	memcpy(confllc->sender_gid, link->gid, SMC_GID_SIZE);
	hton24(confllc->sender_qp_num, link->roce_qp->qp_num);
	confllc->link_num = link->link_id;
	memcpy(confllc->link_uid, lgr->id, SMC_LGR_ID_SIZE);
	confllc->max_links = SMC_LLC_ADD_LNK_MAX_LINKS;
	/* send llc message */
	rc = smc_wr_tx_send(link, pend);
	return rc;
}

/* send LLC confirm rkey request */
static int smc_llc_send_confirm_rkey(struct smc_link *send_link,
				     struct smc_buf_desc *rmb_desc)
{
	struct smc_llc_msg_confirm_rkey *rkeyllc;
	struct smc_wr_tx_pend_priv *pend;
	struct smc_wr_buf *wr_buf;
	struct smc_link *link;
	int i, rc, rtok_ix;

	rc = smc_llc_add_pending_send(send_link, &wr_buf, &pend);
	if (rc)
		return rc;
	rkeyllc = (struct smc_llc_msg_confirm_rkey *)wr_buf;
	memset(rkeyllc, 0, sizeof(*rkeyllc));
	rkeyllc->hd.common.type = SMC_LLC_CONFIRM_RKEY;
	rkeyllc->hd.length = sizeof(struct smc_llc_msg_confirm_rkey);

	rtok_ix = 1;
	for (i = 0; i < SMC_LINKS_PER_LGR_MAX; i++) {
		link = &send_link->lgr->lnk[i];
		if (link->state == SMC_LNK_ACTIVE && link != send_link) {
			rkeyllc->rtoken[rtok_ix].link_id = link->link_id;
			rkeyllc->rtoken[rtok_ix].rmb_key =
				htonl(rmb_desc->mr_rx[link->link_idx]->rkey);
			rkeyllc->rtoken[rtok_ix].rmb_vaddr = cpu_to_be64(
				(u64)sg_dma_address(
					rmb_desc->sgt[link->link_idx].sgl));
			rtok_ix++;
		}
	}
	/* rkey of send_link is in rtoken[0] */
	rkeyllc->rtoken[0].num_rkeys = rtok_ix - 1;
	rkeyllc->rtoken[0].rmb_key =
		htonl(rmb_desc->mr_rx[send_link->link_idx]->rkey);
	rkeyllc->rtoken[0].rmb_vaddr = cpu_to_be64(
		(u64)sg_dma_address(rmb_desc->sgt[send_link->link_idx].sgl));
	/* send llc message */
	rc = smc_wr_tx_send(send_link, pend);
	return rc;
}

/* send LLC delete rkey request */
static int smc_llc_send_delete_rkey(struct smc_link *link,
				    struct smc_buf_desc *rmb_desc)
{
	struct smc_llc_msg_delete_rkey *rkeyllc;
	struct smc_wr_tx_pend_priv *pend;
	struct smc_wr_buf *wr_buf;
	int rc;

	rc = smc_llc_add_pending_send(link, &wr_buf, &pend);
	if (rc)
		return rc;
	rkeyllc = (struct smc_llc_msg_delete_rkey *)wr_buf;
	memset(rkeyllc, 0, sizeof(*rkeyllc));
	rkeyllc->hd.common.type = SMC_LLC_DELETE_RKEY;
	rkeyllc->hd.length = sizeof(struct smc_llc_msg_delete_rkey);
	rkeyllc->num_rkeys = 1;
	rkeyllc->rkey[0] = htonl(rmb_desc->mr_rx[link->link_idx]->rkey);
	/* send llc message */
	rc = smc_wr_tx_send(link, pend);
	return rc;
}

/* send ADD LINK request or response */
int smc_llc_send_add_link(struct smc_link *link, u8 mac[], u8 gid[],
			  struct smc_link *link_new,
			  enum smc_llc_reqresp reqresp)
{
	struct smc_llc_msg_add_link *addllc;
	struct smc_wr_tx_pend_priv *pend;
	struct smc_wr_buf *wr_buf;
	int rc;

	rc = smc_llc_add_pending_send(link, &wr_buf, &pend);
	if (rc)
		return rc;
	addllc = (struct smc_llc_msg_add_link *)wr_buf;

	memset(addllc, 0, sizeof(*addllc));
	addllc->hd.common.type = SMC_LLC_ADD_LINK;
	addllc->hd.length = sizeof(struct smc_llc_msg_add_link);
	if (reqresp == SMC_LLC_RESP)
		addllc->hd.flags |= SMC_LLC_FLAG_RESP;
	memcpy(addllc->sender_mac, mac, ETH_ALEN);
	memcpy(addllc->sender_gid, gid, SMC_GID_SIZE);
	if (link_new) {
		addllc->link_num = link_new->link_id;
		hton24(addllc->sender_qp_num, link_new->roce_qp->qp_num);
		hton24(addllc->initial_psn, link_new->psn_initial);
		if (reqresp == SMC_LLC_REQ)
			addllc->qp_mtu = link_new->path_mtu;
		else
			addllc->qp_mtu = min(link_new->path_mtu,
					     link_new->peer_mtu);
	}
	/* send llc message */
	rc = smc_wr_tx_send(link, pend);
	return rc;
}

/* send DELETE LINK request or response */
int smc_llc_send_delete_link(struct smc_link *link, u8 link_del_id,
			     enum smc_llc_reqresp reqresp, bool orderly,
			     u32 reason)
{
	struct smc_llc_msg_del_link *delllc;
	struct smc_wr_tx_pend_priv *pend;
	struct smc_wr_buf *wr_buf;
	int rc;

	rc = smc_llc_add_pending_send(link, &wr_buf, &pend);
	if (rc)
		return rc;
	delllc = (struct smc_llc_msg_del_link *)wr_buf;

	memset(delllc, 0, sizeof(*delllc));
	delllc->hd.common.type = SMC_LLC_DELETE_LINK;
	delllc->hd.length = sizeof(struct smc_llc_msg_del_link);
	if (reqresp == SMC_LLC_RESP)
		delllc->hd.flags |= SMC_LLC_FLAG_RESP;
	if (orderly)
		delllc->hd.flags |= SMC_LLC_FLAG_DEL_LINK_ORDERLY;
	if (link_del_id)
		delllc->link_num = link_del_id;
	else
		delllc->hd.flags |= SMC_LLC_FLAG_DEL_LINK_ALL;
	delllc->reason = htonl(reason);
	/* send llc message */
	rc = smc_wr_tx_send(link, pend);
	return rc;
}

/* send LLC test link request */
static int smc_llc_send_test_link(struct smc_link *link, u8 user_data[16])
{
	struct smc_llc_msg_test_link *testllc;
	struct smc_wr_tx_pend_priv *pend;
	struct smc_wr_buf *wr_buf;
	int rc;

	rc = smc_llc_add_pending_send(link, &wr_buf, &pend);
	if (rc)
		return rc;
	testllc = (struct smc_llc_msg_test_link *)wr_buf;
	memset(testllc, 0, sizeof(*testllc));
	testllc->hd.common.type = SMC_LLC_TEST_LINK;
	testllc->hd.length = sizeof(struct smc_llc_msg_test_link);
	memcpy(testllc->user_data, user_data, sizeof(testllc->user_data));
	/* send llc message */
	rc = smc_wr_tx_send(link, pend);
	return rc;
}

/* schedule an llc send on link, may wait for buffers */
static int smc_llc_send_message(struct smc_link *link, void *llcbuf)
{
	struct smc_wr_tx_pend_priv *pend;
	struct smc_wr_buf *wr_buf;
	int rc;

	if (!smc_link_usable(link))
		return -ENOLINK;
	rc = smc_llc_add_pending_send(link, &wr_buf, &pend);
	if (rc)
		return rc;
	memcpy(wr_buf, llcbuf, sizeof(union smc_llc_msg));
	return smc_wr_tx_send(link, pend);
}

/********************************* receive ***********************************/

static int smc_llc_alloc_alt_link(struct smc_link_group *lgr,
				  enum smc_lgr_type lgr_new_t)
{
	int i;

	if (lgr->type == SMC_LGR_SYMMETRIC ||
	    (lgr->type != SMC_LGR_SINGLE &&
	     (lgr_new_t == SMC_LGR_ASYMMETRIC_LOCAL ||
	      lgr_new_t == SMC_LGR_ASYMMETRIC_PEER)))
		return -EMLINK;

	if (lgr_new_t == SMC_LGR_ASYMMETRIC_LOCAL ||
	    lgr_new_t == SMC_LGR_ASYMMETRIC_PEER) {
		for (i = SMC_LINKS_PER_LGR_MAX - 1; i >= 0; i--)
			if (lgr->lnk[i].state == SMC_LNK_UNUSED)
				return i;
	} else {
		for (i = 0; i < SMC_LINKS_PER_LGR_MAX; i++)
			if (lgr->lnk[i].state == SMC_LNK_UNUSED)
				return i;
	}
	return -EMLINK;
}

/* return first buffer from any of the next buf lists */
static struct smc_buf_desc *_smc_llc_get_next_rmb(struct smc_link_group *lgr,
						  int *buf_lst)
{
	struct smc_buf_desc *buf_pos;

	while (*buf_lst < SMC_RMBE_SIZES) {
		buf_pos = list_first_entry_or_null(&lgr->rmbs[*buf_lst],
						   struct smc_buf_desc, list);
		if (buf_pos)
			return buf_pos;
		(*buf_lst)++;
	}
	return NULL;
}

/* return next rmb from buffer lists */
static struct smc_buf_desc *smc_llc_get_next_rmb(struct smc_link_group *lgr,
						 int *buf_lst,
						 struct smc_buf_desc *buf_pos)
{
	struct smc_buf_desc *buf_next;

	if (!buf_pos || list_is_last(&buf_pos->list, &lgr->rmbs[*buf_lst])) {
		(*buf_lst)++;
		return _smc_llc_get_next_rmb(lgr, buf_lst);
	}
	buf_next = list_next_entry(buf_pos, list);
	return buf_next;
}

static struct smc_buf_desc *smc_llc_get_first_rmb(struct smc_link_group *lgr,
						  int *buf_lst)
{
	*buf_lst = 0;
	return smc_llc_get_next_rmb(lgr, buf_lst, NULL);
}

/* send one add_link_continue msg */
static int smc_llc_add_link_cont(struct smc_link *link,
				 struct smc_link *link_new, u8 *num_rkeys_todo,
				 int *buf_lst, struct smc_buf_desc **buf_pos)
{
	struct smc_llc_msg_add_link_cont *addc_llc;
	struct smc_link_group *lgr = link->lgr;
	int prim_lnk_idx, lnk_idx, i, rc;
	struct smc_wr_tx_pend_priv *pend;
	struct smc_wr_buf *wr_buf;
	struct smc_buf_desc *rmb;
	u8 n;

	rc = smc_llc_add_pending_send(link, &wr_buf, &pend);
	if (rc)
		return rc;
	addc_llc = (struct smc_llc_msg_add_link_cont *)wr_buf;
	memset(addc_llc, 0, sizeof(*addc_llc));

	prim_lnk_idx = link->link_idx;
	lnk_idx = link_new->link_idx;
	addc_llc->link_num = link_new->link_id;
	addc_llc->num_rkeys = *num_rkeys_todo;
	n = *num_rkeys_todo;
	for (i = 0; i < min_t(u8, n, SMC_LLC_RKEYS_PER_CONT_MSG); i++) {
		if (!*buf_pos) {
			addc_llc->num_rkeys = addc_llc->num_rkeys -
					      *num_rkeys_todo;
			*num_rkeys_todo = 0;
			break;
		}
		rmb = *buf_pos;

		addc_llc->rt[i].rmb_key = htonl(rmb->mr_rx[prim_lnk_idx]->rkey);
		addc_llc->rt[i].rmb_key_new = htonl(rmb->mr_rx[lnk_idx]->rkey);
		addc_llc->rt[i].rmb_vaddr_new =
			cpu_to_be64((u64)sg_dma_address(rmb->sgt[lnk_idx].sgl));

		(*num_rkeys_todo)--;
		*buf_pos = smc_llc_get_next_rmb(lgr, buf_lst, *buf_pos);
		while (*buf_pos && !(*buf_pos)->used)
			*buf_pos = smc_llc_get_next_rmb(lgr, buf_lst, *buf_pos);
	}
	addc_llc->hd.common.type = SMC_LLC_ADD_LINK_CONT;
	addc_llc->hd.length = sizeof(struct smc_llc_msg_add_link_cont);
	if (lgr->role == SMC_CLNT)
		addc_llc->hd.flags |= SMC_LLC_FLAG_RESP;
	return smc_wr_tx_send(link, pend);
}

static int smc_llc_cli_rkey_exchange(struct smc_link *link,
				     struct smc_link *link_new)
{
	struct smc_llc_msg_add_link_cont *addc_llc;
	struct smc_link_group *lgr = link->lgr;
	u8 max, num_rkeys_send, num_rkeys_recv;
	struct smc_llc_qentry *qentry;
	struct smc_buf_desc *buf_pos;
	int buf_lst;
	int rc = 0;
	int i;

	mutex_lock(&lgr->rmbs_lock);
	num_rkeys_send = lgr->conns_num;
	buf_pos = smc_llc_get_first_rmb(lgr, &buf_lst);
	do {
		qentry = smc_llc_wait(lgr, NULL, SMC_LLC_WAIT_TIME,
				      SMC_LLC_ADD_LINK_CONT);
		if (!qentry) {
			rc = -ETIMEDOUT;
			break;
		}
		addc_llc = &qentry->msg.add_link_cont;
		num_rkeys_recv = addc_llc->num_rkeys;
		max = min_t(u8, num_rkeys_recv, SMC_LLC_RKEYS_PER_CONT_MSG);
		for (i = 0; i < max; i++) {
			smc_rtoken_set(lgr, link->link_idx, link_new->link_idx,
				       addc_llc->rt[i].rmb_key,
				       addc_llc->rt[i].rmb_vaddr_new,
				       addc_llc->rt[i].rmb_key_new);
			num_rkeys_recv--;
		}
		smc_llc_flow_qentry_del(&lgr->llc_flow_lcl);
		rc = smc_llc_add_link_cont(link, link_new, &num_rkeys_send,
					   &buf_lst, &buf_pos);
		if (rc)
			break;
	} while (num_rkeys_send || num_rkeys_recv);

	mutex_unlock(&lgr->rmbs_lock);
	return rc;
}

/* prepare and send an add link reject response */
static int smc_llc_cli_add_link_reject(struct smc_llc_qentry *qentry)
{
	qentry->msg.raw.hdr.flags |= SMC_LLC_FLAG_RESP;
	qentry->msg.raw.hdr.flags |= SMC_LLC_FLAG_ADD_LNK_REJ;
	qentry->msg.raw.hdr.add_link_rej_rsn = SMC_LLC_REJ_RSN_NO_ALT_PATH;
	return smc_llc_send_message(qentry->link, &qentry->msg);
}

static int smc_llc_cli_conf_link(struct smc_link *link,
				 struct smc_init_info *ini,
				 struct smc_link *link_new,
				 enum smc_lgr_type lgr_new_t)
{
	struct smc_link_group *lgr = link->lgr;
	struct smc_llc_msg_del_link *del_llc;
	struct smc_llc_qentry *qentry = NULL;
	int rc = 0;

	/* receive CONFIRM LINK request over RoCE fabric */
	qentry = smc_llc_wait(lgr, NULL, SMC_LLC_WAIT_FIRST_TIME, 0);
	if (!qentry) {
		rc = smc_llc_send_delete_link(link, link_new->link_id,
					      SMC_LLC_REQ, false,
					      SMC_LLC_DEL_LOST_PATH);
		return -ENOLINK;
	}
	if (qentry->msg.raw.hdr.common.type != SMC_LLC_CONFIRM_LINK) {
		/* received DELETE_LINK instead */
		del_llc = &qentry->msg.delete_link;
		qentry->msg.raw.hdr.flags |= SMC_LLC_FLAG_RESP;
		smc_llc_send_message(link, &qentry->msg);
		smc_llc_flow_qentry_del(&lgr->llc_flow_lcl);
		return -ENOLINK;
	}
	smc_llc_flow_qentry_del(&lgr->llc_flow_lcl);

	rc = smc_ib_modify_qp_rts(link_new);
	if (rc) {
		smc_llc_send_delete_link(link, link_new->link_id, SMC_LLC_REQ,
					 false, SMC_LLC_DEL_LOST_PATH);
		return -ENOLINK;
	}
	smc_wr_remember_qp_attr(link_new);

	rc = smcr_buf_reg_lgr(link_new);
	if (rc) {
		smc_llc_send_delete_link(link, link_new->link_id, SMC_LLC_REQ,
					 false, SMC_LLC_DEL_LOST_PATH);
		return -ENOLINK;
	}

	/* send CONFIRM LINK response over RoCE fabric */
	rc = smc_llc_send_confirm_link(link_new, SMC_LLC_RESP);
	if (rc) {
		smc_llc_send_delete_link(link, link_new->link_id, SMC_LLC_REQ,
					 false, SMC_LLC_DEL_LOST_PATH);
		return -ENOLINK;
	}
	smc_llc_link_active(link_new);
	lgr->type = lgr_new_t;
	return 0;
}

static void smc_llc_save_add_link_info(struct smc_link *link,
				       struct smc_llc_msg_add_link *add_llc)
{
	link->peer_qpn = ntoh24(add_llc->sender_qp_num);
	memcpy(link->peer_gid, add_llc->sender_gid, SMC_GID_SIZE);
	memcpy(link->peer_mac, add_llc->sender_mac, ETH_ALEN);
	link->peer_psn = ntoh24(add_llc->initial_psn);
	link->peer_mtu = add_llc->qp_mtu;
}

/* as an SMC client, process an add link request */
int smc_llc_cli_add_link(struct smc_link *link, struct smc_llc_qentry *qentry)
{
	struct smc_llc_msg_add_link *llc = &qentry->msg.add_link;
	enum smc_lgr_type lgr_new_t = SMC_LGR_SYMMETRIC;
	struct smc_link_group *lgr = smc_get_lgr(link);
	struct smc_link *lnk_new = NULL;
	struct smc_init_info ini;
	int lnk_idx, rc = 0;

	ini.vlan_id = lgr->vlan_id;
	smc_pnet_find_alt_roce(lgr, &ini, link->smcibdev);
	if (!memcmp(llc->sender_gid, link->peer_gid, SMC_GID_SIZE) &&
	    !memcmp(llc->sender_mac, link->peer_mac, ETH_ALEN)) {
		if (!ini.ib_dev)
			goto out_reject;
		lgr_new_t = SMC_LGR_ASYMMETRIC_PEER;
	}
	if (!ini.ib_dev) {
		lgr_new_t = SMC_LGR_ASYMMETRIC_LOCAL;
		ini.ib_dev = link->smcibdev;
		ini.ib_port = link->ibport;
	}
	lnk_idx = smc_llc_alloc_alt_link(lgr, lgr_new_t);
	if (lnk_idx < 0)
		goto out_reject;
	lnk_new = &lgr->lnk[lnk_idx];
	rc = smcr_link_init(lgr, lnk_new, lnk_idx, &ini);
	if (rc)
		goto out_reject;
	smc_llc_save_add_link_info(lnk_new, llc);
	lnk_new->link_id = llc->link_num;

	rc = smc_ib_ready_link(lnk_new);
	if (rc)
		goto out_clear_lnk;

	rc = smcr_buf_map_lgr(lnk_new);
	if (rc)
		goto out_clear_lnk;

	rc = smc_llc_send_add_link(link,
				   lnk_new->smcibdev->mac[ini.ib_port - 1],
				   lnk_new->gid, lnk_new, SMC_LLC_RESP);
	if (rc)
		goto out_clear_lnk;
	rc = smc_llc_cli_rkey_exchange(link, lnk_new);
	if (rc) {
		rc = 0;
		goto out_clear_lnk;
	}
	rc = smc_llc_cli_conf_link(link, &ini, lnk_new, lgr_new_t);
	if (!rc)
		goto out;
out_clear_lnk:
	smcr_link_clear(lnk_new);
out_reject:
	smc_llc_cli_add_link_reject(qentry);
out:
	kfree(qentry);
	return rc;
}

static void smc_llc_process_cli_add_link(struct smc_link_group *lgr)
{
	struct smc_llc_qentry *qentry;

	qentry = smc_llc_flow_qentry_clr(&lgr->llc_flow_lcl);

	mutex_lock(&lgr->llc_conf_mutex);
	smc_llc_cli_add_link(qentry->link, qentry);
	mutex_unlock(&lgr->llc_conf_mutex);
}

static int smc_llc_active_link_count(struct smc_link_group *lgr)
{
	int i, link_count = 0;

	for (i = 0; i < SMC_LINKS_PER_LGR_MAX; i++) {
		if (!smc_link_usable(&lgr->lnk[i]))
			continue;
		link_count++;
	}
	return link_count;
}

/* find the asymmetric link when 3 links are established  */
static struct smc_link *smc_llc_find_asym_link(struct smc_link_group *lgr)
{
	int asym_idx = -ENOENT;
	int i, j, k;
	bool found;

	/* determine asymmetric link */
	found = false;
	for (i = 0; i < SMC_LINKS_PER_LGR_MAX; i++) {
		for (j = i + 1; j < SMC_LINKS_PER_LGR_MAX; j++) {
			if (!smc_link_usable(&lgr->lnk[i]) ||
			    !smc_link_usable(&lgr->lnk[j]))
				continue;
			if (!memcmp(lgr->lnk[i].gid, lgr->lnk[j].gid,
				    SMC_GID_SIZE)) {
				found = true;	/* asym_lnk is i or j */
				break;
			}
		}
		if (found)
			break;
	}
	if (!found)
		goto out; /* no asymmetric link */
	for (k = 0; k < SMC_LINKS_PER_LGR_MAX; k++) {
		if (!smc_link_usable(&lgr->lnk[k]))
			continue;
		if (k != i &&
		    !memcmp(lgr->lnk[i].peer_gid, lgr->lnk[k].peer_gid,
			    SMC_GID_SIZE)) {
			asym_idx = i;
			break;
		}
		if (k != j &&
		    !memcmp(lgr->lnk[j].peer_gid, lgr->lnk[k].peer_gid,
			    SMC_GID_SIZE)) {
			asym_idx = j;
			break;
		}
	}
out:
	return (asym_idx < 0) ? NULL : &lgr->lnk[asym_idx];
}

static void smc_llc_delete_asym_link(struct smc_link_group *lgr)
{
	struct smc_link *lnk_new = NULL, *lnk_asym;
	struct smc_llc_qentry *qentry;
	int rc;

	lnk_asym = smc_llc_find_asym_link(lgr);
	if (!lnk_asym)
		return; /* no asymmetric link */
	if (!smc_link_downing(&lnk_asym->state))
		return;
	/* tbd: lnk_new = smc_switch_conns(lgr, lnk_asym, false); */
	smc_wr_tx_wait_no_pending_sends(lnk_asym);
	if (!lnk_new)
		goto out_free;
	/* change flow type from ADD_LINK into DEL_LINK */
	lgr->llc_flow_lcl.type = SMC_LLC_FLOW_DEL_LINK;
	rc = smc_llc_send_delete_link(lnk_new, lnk_asym->link_id, SMC_LLC_REQ,
				      true, SMC_LLC_DEL_NO_ASYM_NEEDED);
	if (rc) {
		smcr_link_down_cond(lnk_new);
		goto out_free;
	}
	qentry = smc_llc_wait(lgr, lnk_new, SMC_LLC_WAIT_TIME,
			      SMC_LLC_DELETE_LINK);
	if (!qentry) {
		smcr_link_down_cond(lnk_new);
		goto out_free;
	}
	smc_llc_flow_qentry_del(&lgr->llc_flow_lcl);
out_free:
	smcr_link_clear(lnk_asym);
}

static int smc_llc_srv_rkey_exchange(struct smc_link *link,
				     struct smc_link *link_new)
{
	struct smc_llc_msg_add_link_cont *addc_llc;
	struct smc_link_group *lgr = link->lgr;
	u8 max, num_rkeys_send, num_rkeys_recv;
	struct smc_llc_qentry *qentry = NULL;
	struct smc_buf_desc *buf_pos;
	int buf_lst;
	int rc = 0;
	int i;

	mutex_lock(&lgr->rmbs_lock);
	num_rkeys_send = lgr->conns_num;
	buf_pos = smc_llc_get_first_rmb(lgr, &buf_lst);
	do {
		smc_llc_add_link_cont(link, link_new, &num_rkeys_send,
				      &buf_lst, &buf_pos);
		qentry = smc_llc_wait(lgr, link, SMC_LLC_WAIT_TIME,
				      SMC_LLC_ADD_LINK_CONT);
		if (!qentry) {
			rc = -ETIMEDOUT;
			goto out;
		}
		addc_llc = &qentry->msg.add_link_cont;
		num_rkeys_recv = addc_llc->num_rkeys;
		max = min_t(u8, num_rkeys_recv, SMC_LLC_RKEYS_PER_CONT_MSG);
		for (i = 0; i < max; i++) {
			smc_rtoken_set(lgr, link->link_idx, link_new->link_idx,
				       addc_llc->rt[i].rmb_key,
				       addc_llc->rt[i].rmb_vaddr_new,
				       addc_llc->rt[i].rmb_key_new);
			num_rkeys_recv--;
		}
		smc_llc_flow_qentry_del(&lgr->llc_flow_lcl);
	} while (num_rkeys_send || num_rkeys_recv);
out:
	mutex_unlock(&lgr->rmbs_lock);
	return rc;
}

static int smc_llc_srv_conf_link(struct smc_link *link,
				 struct smc_link *link_new,
				 enum smc_lgr_type lgr_new_t)