path: root/drivers/infiniband/sw/siw/siw_qp_tx.c

// SPDX-License-Identifier: GPL-2.0 or BSD-3-Clause

/* Authors: Bernard Metzler <bmt@zurich.ibm.com> */
/* Copyright (c) 2008-2019, IBM Corporation */

#include <linux/errno.h>
#include <linux/types.h>
#include <linux/net.h>
#include <linux/scatterlist.h>
#include <linux/highmem.h>
#include <net/tcp.h>

#include <rdma/iw_cm.h>
#include <rdma/ib_verbs.h>
#include <rdma/ib_user_verbs.h>

#include "siw.h"
#include "siw_verbs.h"
#include "siw_mem.h"

#define MAX_HDR_INLINE					\
	(((uint32_t)(sizeof(struct siw_rreq_pkt) -	\
		     sizeof(struct iwarp_send))) & 0xF8)

static struct page *siw_get_pblpage(struct siw_mem *mem, u64 addr, int *idx)
{
	struct siw_pbl *pbl = mem->pbl;
	u64 offset = addr - mem->va;
	dma_addr_t paddr = siw_pbl_get_buffer(pbl, offset, NULL, idx);

	if (paddr)
		return ib_virt_dma_to_page(paddr);

	return NULL;
}

/*
 * Copy short payload at provided destination payload address
 */
static int siw_try_1seg(struct siw_iwarp_tx *c_tx, void *paddr)
{
	struct siw_wqe *wqe = &c_tx->wqe_active;
	struct siw_sge *sge = &wqe->sqe.sge[0];
	u32 bytes = sge->length;

	if (bytes > MAX_HDR_INLINE || wqe->sqe.num_sge != 1)
		return MAX_HDR_INLINE + 1;

	if (!bytes)
		return 0;

	if (tx_flags(wqe) & SIW_WQE_INLINE) {
		memcpy(paddr, &wqe->sqe.sge[1], bytes);
	} else {
		struct siw_mem *mem = wqe->mem[0];

		if (!mem->mem_obj) {
			/* Kernel client using kva */
			memcpy(paddr, ib_virt_dma_to_ptr(sge->laddr), bytes);
		} else if (c_tx->in_syscall) {
			if (copy_from_user(paddr, u64_to_user_ptr(sge->laddr),
					   bytes))
				return -EFAULT;
		} else {
			unsigned int off = sge->laddr & ~PAGE_MASK;
			struct page *p;
			char *buffer;
			int pbl_idx = 0;

			if (!mem->is_pbl)
				p = siw_get_upage(mem->umem, sge->laddr);
			else
				p = siw_get_pblpage(mem, sge->laddr, &pbl_idx);

			if (unlikely(!p))
				return -EFAULT;

			buffer = kmap_local_page(p);

			if (likely(PAGE_SIZE - off >= bytes)) {
				memcpy(paddr, buffer + off, bytes);
			} else {
				unsigned long part = bytes - (PAGE_SIZE - off);

				memcpy(paddr, buffer + off, part);
				kunmap_local(buffer);

				if (!mem->is_pbl)
					p = siw_get_upage(mem->umem,
							  sge->laddr + part);
				else
					p = siw_get_pblpage(mem,
							    sge->laddr + part,
							    &pbl_idx);
				if (unlikely(!p))
					return -EFAULT;

				buffer = kmap_local_page(p);
				memcpy(paddr + part, buffer, bytes - part);
			}
			kunmap_local(buffer);
		}
	}
	return (int)bytes;
}

#define PKT_FRAGMENTED 1
#define PKT_COMPLETE 0

/*
 * siw_qp_prepare_tx()
 *
 * Prepare tx state for sending out one fpdu. Builds complete pkt
 * if no user data or only immediate data are present.
 *
 * returns PKT_COMPLETE if complete pkt built, PKT_FRAGMENTED otherwise.
 */
static int siw_qp_prepare_tx(struct siw_iwarp_tx *c_tx)
{
	struct siw_wqe *wqe = &c_tx->wqe_active;
	char *crc = NULL;
	int data = 0;

	switch (tx_type(wqe)) {
	case SIW_OP_READ:
	case SIW_OP_READ_LOCAL_INV:
		memcpy(&c_tx->pkt.ctrl,
		       &iwarp_pktinfo[RDMAP_RDMA_READ_REQ].ctrl,
		       sizeof(struct iwarp_ctrl));

		c_tx->pkt.rreq.rsvd = 0;
		c_tx->pkt.rreq.ddp_qn = htonl(RDMAP_UNTAGGED_QN_RDMA_READ);
		c_tx->pkt.rreq.ddp_msn =
			htonl(++c_tx->ddp_msn[RDMAP_UNTAGGED_QN_RDMA_READ]);
		c_tx->pkt.rreq.ddp_mo = 0;
		c_tx->pkt.rreq.sink_stag = htonl(wqe->sqe.sge[0].lkey);
		c_tx->pkt.rreq.sink_to =
			cpu_to_be64(wqe->sqe.sge[0].laddr);
		c_tx->pkt.rreq.source_stag = htonl(wqe->sqe.rkey);
		c_tx->pkt.rreq.source_to = cpu_to_be64(wqe->sqe.raddr);
		c_tx->pkt.rreq.read_size = htonl(wqe->sqe.sge[0].length);

		c_tx->ctrl_len = sizeof(struct iwarp_rdma_rreq);
		crc = (char *)&c_tx->pkt.rreq_pkt.crc;
		break;

	case SIW_OP_SEND:
		if (tx_flags(wqe) & SIW_WQE_SOLICITED)
			memcpy(&c_tx->pkt.ctrl,
			       &iwarp_pktinfo[RDMAP_SEND_SE].ctrl,
			       sizeof(struct iwarp_ctrl));
		else
			memcpy(&c_tx->pkt.ctrl, &iwarp_pktinfo[RDMAP_SEND].ctrl,
			       sizeof(struct iwarp_ctrl));

		c_tx->pkt.send.ddp_qn = RDMAP_UNTAGGED_QN_SEND;
		c_tx->pkt.send.ddp_msn =
			htonl(++c_tx->ddp_msn[RDMAP_UNTAGGED_QN_SEND]);
		c_tx->pkt.send.ddp_mo = 0;

		c_tx->pkt.send_inv.inval_stag = 0;

		c_tx->ctrl_len = sizeof(struct iwarp_send);

		crc = (char *)&c_tx->pkt.send_pkt.crc;
		data = siw_try_1seg(c_tx, crc);
		break;

	case SIW_OP_SEND_REMOTE_INV:
		if (tx_flags(wqe) & SIW_WQE_SOLICITED)
			memcpy(&c_tx->pkt.ctrl,
			       &iwarp_pktinfo[RDMAP_SEND_SE_INVAL].ctrl,
			       sizeof(struct iwarp_ctrl));
		else
			memcpy(&c_tx->pkt.ctrl,
			       &iwarp_pktinfo[RDMAP_SEND_INVAL].ctrl,
			       sizeof(struct iwarp_ctrl));

		c_tx->pkt.send.ddp_qn = RDMAP_UNTAGGED_QN_SEND;
		c_tx->pkt.send.ddp_msn =
			htonl(++c_tx->ddp_msn[RDMAP_UNTAGGED_QN_SEND]);
		c_tx->pkt.send.ddp_mo = 0;

		c_tx->pkt.send_inv.inval_stag = cpu_to_be32(wqe->sqe.rkey);

		c_tx->ctrl_len = sizeof(struct iwarp_send_inv);

		crc = (char *)&c_tx->pkt.send_pkt.crc;
		data = siw_try_1seg(c_tx, crc);
		break;

	case SIW_OP_WRITE:
		memcpy(&c_tx->pkt.ctrl, &iwarp_pktinfo[RDMAP_RDMA_WRITE].ctrl,
		       sizeof(struct iwarp_ctrl));

		c_tx->pkt.rwrite.sink_stag = htonl(wqe->sqe.rkey);
		c_tx->pkt.rwrite.sink_to = cpu_to_be64(wqe->sqe.raddr);
		c_tx->ctrl_len = sizeof(struct iwarp_rdma_write);

		crc = (char *)&c_tx->pkt.write_pkt.crc;
		data = siw_try_1seg(c_tx, crc);
		break;

	case SIW_OP_READ_RESPONSE:
		memcpy(&c_tx->pkt.ctrl,
		       &iwarp_pktinfo[RDMAP_RDMA_READ_RESP].ctrl,
		       sizeof(struct iwarp_ctrl));

		/* NBO */
		c_tx->pkt.rresp.sink_stag = cpu_to_be32(wqe->sqe.rkey);
		c_tx->pkt.rresp.sink_to = cpu_to_be64(wqe->sqe.raddr);

		c_tx->ctrl_len = sizeof(struct iwarp_rdma_rresp);

		crc = (char *)&c_tx->pkt.write_pkt.crc;
		data = siw_try_1seg(c_tx, crc);
		break;

	default:
		siw_dbg_qp(tx_qp(c_tx), "stale wqe type %d\n", tx_type(wqe));
		return -EOPNOTSUPP;
	}
	if (unlikely(data < 0))
		return data;

	c_tx->ctrl_sent = 0;

	if (data <= MAX_HDR_INLINE) {
		if (data) {
			wqe->processed = data;

			c_tx->pkt.ctrl.mpa_len =
				htons(c_tx->ctrl_len + data - MPA_HDR_SIZE);

			/* Add pad, if needed */
			data += -(int)data & 0x3;
			/* advance CRC location after payload */
			crc += data;
			c_tx->ctrl_len += data;

			if (!(c_tx->pkt.ctrl.ddp_rdmap_ctrl & DDP_FLAG_TAGGED))
				c_tx->pkt.c_untagged.ddp_mo = 0;
			else
				c_tx->pkt.c_tagged.ddp_to =
					cpu_to_be64(wqe->sqe.raddr);
		}

		*(u32 *)crc = 0;
		/*
		 * Do complete CRC if enabled and short packet
		 */
		if (c_tx->mpa_crc_hd) {
			crypto_shash_init(c_tx->mpa_crc_hd);
			if (crypto_shash_update(c_tx->mpa_crc_hd,
						(u8 *)&c_tx->pkt,
						c_tx->ctrl_len))
				return -EINVAL;
			crypto_shash_final(c_tx->mpa_crc_hd, (u8 *)crc);
		}
		c_tx->ctrl_len += MPA_CRC_SIZE;

		return PKT_COMPLETE;
	}
	c_tx->ctrl_len += MPA_CRC_SIZE;
	c_tx->sge_idx = 0;
	c_tx->sge_off = 0;
	c_tx->pbl_idx = 0;

	/*
	 * Allow direct sending out of user buffer if WR is non signalled
	 * and payload is over threshold.
	 * Per RDMA verbs, the application should not change the send buffer
	 * until the work completed. In iWarp, work completion is only
	 * local delivery to TCP. TCP may reuse the buffer for
	 * retransmission. Changing unsent data also breaks the CRC,
	 * if applied.
	 */
	if (c_tx->zcopy_tx && wqe->bytes >= SENDPAGE_THRESH &&
	    !(tx_flags(wqe) & SIW_WQE_SIGNALLED))
		c_tx->use_sendpage = 1;
	else
		c_tx->use_sendpage = 0;

	return PKT_FRAGMENTED;
}

/*
 * Send out one complete control type FPDU, or header of FPDU carrying
 * data. Used for fixed sized packets like Read.Requests or zero length
 * SENDs, WRITEs, READ.Responses, or header only.
 */
static int siw_tx_ctrl(struct siw_iwarp_tx *c_tx, struct socket *s,
			      int flags)
{
	struct msghdr msg = { .msg_flags = flags };
	struct kvec iov = { .iov_base =
				    (char *)&c_tx->pkt.ctrl + c_tx->ctrl_sent,
			    .iov_len = c_tx->ctrl_len - c_tx->ctrl_sent };

	int rv = kernel_sendmsg(s, &msg, &iov, 1,
				c_tx->ctrl_len - c_tx->ctrl_sent);

	if (rv >= 0) {
		c_tx->ctrl_sent += rv;

		if (c_tx->ctrl_sent == c_tx->ctrl_len)
			rv = 0;
		else
			rv = -EAGAIN;
	}
	return rv;
}

/*
 * 0copy TCP transmit interface: Use MSG_SPLICE_PAGES.
 *
 * Using sendpage to push page by page appears to be less efficient
 * than using sendmsg, even if data are copied.
 *
 * A general performance limitation might be the extra four bytes
 * trailer checksum segment to be pushed after user data.
 */
static int siw_tcp_sendpages(struct socket *s, struct page **page, int offset,
			     size_t size)
{
	struct bio_vec bvec;
	struct msghdr msg = {
		.msg_flags = (MSG_MORE | MSG_DONTWAIT | MSG_SPLICE_PAGES),
	};
	struct sock *sk = s->sk;
	int i = 0, rv = 0, sent = 0;

	while (size) {
		size_t bytes = min_t(size_t, PAGE_SIZE - offset, size);

		if (size + offset <= PAGE_SIZE)
			msg.msg_flags &= ~MSG_MORE;

		tcp_rate_check_app_limited(sk);
		bvec_set_page(&bvec, page[i], bytes, offset);
		iov_iter_bvec(&msg.msg_iter, ITER_SOURCE, &bvec, 1, size);

try_page_again:
		lock_sock(sk);
		rv = tcp_sendmsg_locked(sk, &msg, size);
		release_sock(sk);

		if (rv > 0) {
			size -= rv;
			sent += rv;
			if (rv != bytes) {
				offset += rv;
				bytes -= rv;
				goto try_page_again;
			}
			offset = 0;
		} else {
			if (rv == -EAGAIN || rv == 0)
				break;
			return rv;
		}
		i++;
	}
	return sent;
}

/*
 * siw_0copy_tx()
 *
 * Pushes list of pages to TCP socket. If pages from multiple
 * SGE's, all referenced pages of each SGE are pushed in one
 * shot.
 */
static int siw_0copy_tx(struct socket *s, struct page **page,
			struct siw_sge *sge, unsigned int offset,
			unsigned int size)
{
	int i = 0, sent = 0, rv;
	int sge_bytes = min(sge->length - offset, size);

	offset = (sge->laddr + offset) & ~PAGE_MASK;

	while (sent != size) {
		rv = siw_tcp_sendpages(s, &page[i], offset, sge_bytes);
		if (rv >= 0) {
			sent += rv;
			if (size == sent || sge_bytes > rv)
				break;

			i += PAGE_ALIGN(sge_bytes + offset) >> PAGE_SHIFT;
			sge++;
			sge_bytes = min(sge->length, size - sent);
			offset = sge->laddr & ~PAGE_MASK;
		} else {
			sent = rv;
			break;
		}
	}
	return sent;
}

#define MAX_TRAILER (MPA_CRC_SIZE + 4)

static void siw_unmap_pages(struct kvec *iov, unsigned long kmap_mask, int len)
{
	int i;

	/*
	 * Work backwards through the array to honor the kmap_local_page()
	 * ordering requirements.
	 */
	for (i = (len-1); i >= 0; i--) {
		if (kmap_mask & BIT(i)) {
			unsigned long addr = (unsigned long)iov[i].iov_base;

			kunmap_local((void *)(addr & PAGE_MASK));
		}
	}
}

/*
 * siw_tx_hdt() tries to push a complete packet to TCP where all
 * packet fragments are referenced by the elements of one iovec.
 * For the data portion, each involved page must be referenced by
 * one extra element. All sge's data can be non-aligned to page
 * boundaries. Two more elements are referencing iWARP header
 * and trailer:
 * MAX_ARRAY = 64KB/PAGE_SIZE + 1 + (2 * (SIW_MAX_SGE - 1) + HDR + TRL
 */
#define MAX_ARRAY ((0xffff / PAGE_SIZE) + 1 + (2 * (SIW_MAX_SGE - 1) + 2))

/*
 * Write out iov referencing hdr, data and trailer of current FPDU.
 * Update transmit state dependent on write return status
 */
static int siw_tx_hdt(struct siw_iwarp_tx *c_tx, struct socket *s)
{
	struct siw_wqe *wqe = &c_tx->wqe_active;
	struct siw_sge *sge = &wqe->sqe.sge[c_tx->sge_idx];
	struct kvec iov[MAX_ARRAY];
	struct page *page_array[MAX_ARRAY];
	struct msghdr msg = { .msg_flags = MSG_DONTWAIT | MSG_EOR };

	int seg = 0, do_crc = c_tx->do_crc, is_kva = 0, rv;
	unsigned int data_len = c_tx->bytes_unsent, hdr_len = 0, trl_len = 0,
		     sge_off = c_tx->sge_off, sge_idx = c_tx->sge_idx,
		     pbl_idx = c_tx->pbl_idx;
	unsigned long kmap_mask = 0L;

	if (c_tx->state == SIW_SEND_HDR) {
		if (c_tx->use_sendpage) {
			rv = siw_tx_ctrl(c_tx, s, MSG_DONTWAIT | MSG_MORE);
			if (rv)
				goto done;

			c_tx->state = SIW_SEND_DATA;
		} else {
			iov[0].iov_base =
				(char *)&c_tx->pkt.ctrl + c_tx->ctrl_sent;
			iov[0].iov_len = hdr_len =
				c_tx->ctrl_len - c_tx->ctrl_sent;
			seg = 1;
		}
	}

	wqe->processed += data_len;

	while (data_len) { /* walk the list of SGE's */
		unsigned int sge_len = min(sge->length - sge_off, data_len);
		unsigned int fp_off = (sge->laddr + sge_off) & ~PAGE_MASK;
		struct siw_mem *mem;

		if (!(tx_flags(wqe) & SIW_WQE_INLINE)) {
			mem = wqe->mem[sge_idx];
			is_kva = mem->mem_obj == NULL ? 1 : 0;
		} else {
			is_kva = 1;
		}
		if (is_kva && !c_tx->use_sendpage) {
			/*
			 * tx from kernel virtual address: either inline data
			 * or memory region with assigned kernel buffer
			 */
			iov[seg].iov_base =
				ib_virt_dma_to_ptr(sge->laddr + sge_off);
			iov[seg].iov_len = sge_len;

			if (do_crc)
				crypto_shash_update(c_tx->mpa_crc_hd,
						    iov[seg].iov_base,
						    sge_len);
			sge_off += sge_len;
			data_len -= sge_len;
			seg++;
			goto sge_done;
		}

		while (sge_len) {
			size_t plen = min((int)PAGE_SIZE - fp_off, sge_len);
			void *kaddr;

			if (!is_kva) {
				struct page *p;

				if (mem->is_pbl)
					p = siw_get_pblpage(
						mem, sge->laddr + sge_off,
						&pbl_idx);
				else
					p = siw_get_upage(mem->umem,
							  sge->laddr + sge_off);
				if (unlikely(!p)) {
					siw_unmap_pages(iov, kmap_mask, seg);
					wqe->processed -= c_tx->bytes_unsent;
					rv = -EFAULT;
					goto done_crc;
				}
				page_array[seg] = p;

				if (!c_tx->use_sendpage) {
					void *kaddr = kmap_local_page(p);

					/* Remember for later kunmap() */
					kmap_mask |= BIT(seg);
					iov[seg].iov_base = kaddr + fp_off;
					iov[seg].iov_len = plen;

					if (do_crc)
						crypto_shash_update(
							c_tx->mpa_crc_hd,
							iov[seg].iov_base,
							plen);
				} else if (do_crc) {
					kaddr = kmap_local_page(p);
					crypto_shash_update(c_tx->mpa_crc_hd,
							    kaddr + fp_off,
							    plen);
					kunmap_local(kaddr);
				}
			} else {
				/*
				 * Cast to an uintptr_t to preserve all 64 bits
				 * in sge->laddr.
				 */
				u64 va = sge->laddr + sge_off;

				page_array[seg] = ib_virt_dma_to_page(va);
				if (do_crc)
					crypto_shash_update(
						c_tx->mpa_crc_hd,
						ib_virt_dma_to_ptr(va),
						plen);
			}

			sge_len -= plen;
			sge_off += plen;
			data_len -= plen;
			fp_off = 0;

			if (++seg >= (int)MAX_ARRAY) {
				siw_dbg_qp(tx_qp(c_tx), "to many fragments\n");
				siw_unmap_pages(iov, kmap_mask, seg-1);
				wqe->processed -= c_tx->bytes_unsent;
				rv = -EMSGSIZE;
				goto done_crc;
			}
		}
sge_done:
		/* Update SGE variables at end of SGE */
		if (sge_off == sge->length &&
		    (data_len != 0 || wqe->processed < wqe->bytes)) {
			sge_idx++;
			sge++;
			sge_off = 0;
		}
	}
	/* trailer */
	if (likely(c_tx->state != SIW_SEND_TRAILER)) {
		iov[seg].iov_base = &c_tx->trailer.pad[4 - c_tx->pad];
		iov[seg].iov_len = trl_len = MAX_TRAILER - (4 - c_tx->pad);
	} else {
		iov[seg].iov_base = &c_tx->trailer.pad[c_tx->ctrl_sent];
		iov[seg].iov_len = trl_len = MAX_TRAILER - c_tx->ctrl_sent;
	}

	if (c_tx->pad) {
		*(u32 *)c_tx->trailer.pad = 0;
		if (do_crc)
			crypto_shash_update(c_tx->mpa_crc_hd,
				(u8 *)&c_tx->trailer.crc - c_tx->pad,
				c_tx->pad);
	}
	if (!c_tx->mpa_crc_hd)
		c_tx->trailer.crc = 0;
	else if (do_crc)
		crypto_shash_final(c_tx->mpa_crc_hd, (u8 *)&c_tx->trailer.crc);

	data_len = c_tx->bytes_unsent;

	if (c_tx->use_sendpage) {
		rv = siw_0copy_tx(s, page_array, &wqe->sqe.sge[c_tx->sge_idx],
				  c_tx->sge_off, data_len);
		if (rv == data_len) {
			rv = kernel_sendmsg(s, &msg, &iov[seg], 1, trl_len);
			if (rv > 0)
				rv += data_len;
			else
				rv = data_len;
		}
	} else {
		rv = kernel_sendmsg(s, &msg, iov, seg + 1,
				    hdr_len + data_len + trl_len);
		siw_unmap_pages(iov, kmap_mask, seg);
	}
	if (rv < (int)hdr_len) {
		/* Not even complete hdr pushed or negative rv */
		wqe->processed -= data_len;
		if (rv >= 0) {
			c_tx->ctrl_sent += rv;
			rv = -EAGAIN;
		}
		goto done_crc;
	}
	rv -= hdr_len;

	if (rv >= (int)data_len) {
		/* all user data pushed to TCP or no data to push */
		if (data_len > 0 && wqe->processed < wqe->bytes) {
			/* Save the current state for next tx */
			c_tx->sge_idx = sge_idx;
			c_tx->sge_off = sge_off;
			c_tx->pbl_idx = pbl_idx;
		}
		rv -= data_len;

		if (rv == trl_len) /* all pushed */
			rv = 0;
		else {
			c_tx->state = SIW_SEND_TRAILER;
			c_tx->ctrl_len = MAX_TRAILER;
			c_tx->ctrl_sent = rv + 4 - c_tx->pad;
			c_tx->bytes_unsent = 0;
			rv = -EAGAIN;
		}

	} else if (data_len > 0) {
		/* Maybe some user data pushed to TCP */
		c_tx->state = SIW_SEND_DATA;
		wqe->processed -= data_len - rv;

		if (rv) {
			/*
			 * Some bytes out. Recompute tx state based
			 * on old state and bytes pushed
			 */
			unsigned int sge_unsent;

			c_tx->bytes_unsent -= rv;
			sge = &wqe->sqe.sge[c_tx->sge_idx];
			sge_unsent = sge->length - c_tx->sge_off;

			while (sge_unsent <= rv) {
				rv -= sge_unsent;
				c_tx->sge_idx++;
				c_tx->sge_off = 0;
				sge++;
				sge_unsent = sge->length;
			}
			c_tx->sge_off += rv;
		}
		rv = -EAGAIN;
	}
done_crc:
	c_tx->do_crc = 0;
done:
	return rv;
}

static void siw_update_tcpseg(struct siw_iwarp_tx *c_tx,
				     struct socket *s)
{
	struct tcp_sock *tp = tcp_sk(s->sk);

	if (tp->gso_segs) {
		if (c_tx->gso_seg_limit == 0)
			c_tx->tcp_seglen = tp->mss_cache * tp->gso_segs;
		else
			c_tx->tcp_seglen =
				tp->mss_cache *
				min_t(u16, c_tx->gso_seg_limit, tp->gso_segs);
	} else {
		c_tx->tcp_seglen = tp->mss_cache;
	}
	/* Loopback may give odd numbers */
	c_tx->tcp_seglen &= 0xfffffff8;
}

/*
 * siw_prepare_fpdu()
 *
 * Prepares transmit context to send out one FPDU if FPDU will contain
 * user data and user data are not immediate data.
 * Computes maximum FPDU length to fill up TCP MSS if possible.
 *
 * @qp:		QP from which to transmit
 * @wqe:	Current WQE causing transmission
 *
 * TODO: Take into account real available sendspace on socket
 *       to avoid header misalignment due to send pausing within
 *       fpdu transmission
 */
static void siw_prepare_fpdu(struct siw_qp *qp, struct siw_wqe *wqe)
{
	struct siw_iwarp_tx *c_tx = &qp->tx_ctx;
	int data_len;

	c_tx->ctrl_len =
		iwarp_pktinfo[__rdmap_get_opcode(&c_tx->pkt.ctrl)].hdr_len;
	c_tx->ctrl_sent = 0;

	/*
	 * Update target buffer offset if any
	 */
	if (!(c_tx->pkt.ctrl.ddp_rdmap_ctrl & DDP_FLAG_TAGGED))
		/* Untagged message */
		c_tx->pkt.c_untagged.ddp_mo = cpu_to_be32(wqe->processed);
	else /* Tagged message */
		c_tx->pkt.c_tagged.ddp_to =
			cpu_to_be64(wqe->sqe.raddr + wqe->processed);

	data_len = wqe->bytes - wqe->processed;
	if (data_len + c_tx->ctrl_len + MPA_CRC_SIZE > c_tx->tcp_seglen) {
		/* Trim DDP payload to fit into current TCP segment */
		data_len = c_tx->tcp_seglen - (c_tx->ctrl_len + MPA_CRC_SIZE);
		c_tx->pkt.ctrl.ddp_rdmap_ctrl &= ~DDP_FLAG_LAST;
		c_tx->pad = 0;
	} else {
		c_tx->pkt.ctrl.ddp_rdmap_ctrl |= DDP_FLAG_LAST;
		c_tx->pad = -data_len & 0x3;
	}
	c_tx->bytes_unsent = data_len;

	c_tx->pkt.ctrl.mpa_len =
		htons(c_tx->ctrl_len + data_len - MPA_HDR_SIZE);

	/*
	 * Init MPA CRC computation
	 */
	if (c_tx->mpa_crc_hd) {
		crypto_shash_init(c_tx->mpa_crc_hd);
		crypto_shash_update(c_tx->mpa_crc_hd, (u8 *)&c_tx->pkt,
				    c_tx->ctrl_len);
		c_tx->do_crc = 1;
	}
}

/*
 * siw_check_sgl_tx()
 *
 * Check permissions for a list of SGE's (SGL).
 * A successful check will have all memory referenced
 * for transmission resolved and assigned to the WQE.
 *
 * @pd:		Protection Domain SGL should belong to
 * @wqe:	WQE to be checked
 * @perms:	requested access permissions
 *
 */

static int siw_check_sgl_tx(struct ib_pd *pd, struct siw_wqe *wqe,
			    enum ib_access_flags perms)
{
	struct siw_sge *sge = &wqe->sqe.sge[0];
	int i, len, num_sge = wqe->sqe.num_sge;

	if (unlikely(num_sge > SIW_MAX_SGE))
		return -EINVAL;

	for (i = 0, len = 0; num_sge; num_sge--, i++, sge++) {
		/*
		 * rdma verbs: do not check stag for a zero length sge
		 */
		if (sge->length) {
			int rv = siw_check_sge(pd, sge, &wqe->mem[i], perms, 0,
					       sge->length);

			if (unlikely(rv != E_ACCESS_OK))
				return rv;
		}
		len += sge->length;
	}
	return len;
}

/*
 * siw_qp_sq_proc_tx()
 *
 * Process one WQE which needs transmission on the wire.
 */
static int siw_qp_sq_proc_tx(struct siw_qp *qp, struct siw_wqe *wqe)
{
	struct siw_iwarp_tx *c_tx = &qp->tx_ctx;
	struct socket *s = qp->attrs.sk;
	int rv = 0, burst_len = qp->tx_ctx.burst;
	enum rdmap_ecode ecode = RDMAP_ECODE_CATASTROPHIC_STREAM;

	if (unlikely(wqe->wr_status == SIW_WR_IDLE))
		return 0;

	if (!burst_len)
		burst_len = SQ_USER_MAXBURST;

	if (wqe->wr_status == SIW_WR_QUEUED) {
		if (!(wqe->sqe.flags & SIW_WQE_INLINE)) {
			if (tx_type(wqe) == SIW_OP_READ_RESPONSE)
				wqe->sqe.num_sge = 1;

			if (tx_type(wqe) != SIW_OP_READ &&
			    tx_type(wqe) != SIW_OP_READ_LOCAL_INV) {
				/*
				 * Reference memory to be tx'd w/o checking
				 * access for LOCAL_READ permission, since
				 * not defined in RDMA core.
				 */
				rv = siw_check_sgl_tx(qp->pd, wqe, 0);
				if (rv < 0) {
					if (tx_type(wqe) ==
					    SIW_OP_READ_RESPONSE)
						ecode = siw_rdmap_error(-rv);
					rv = -EINVAL;
					goto tx_error;
				}
				wqe->bytes = rv;
			} else {
				wqe->bytes = 0;
			}
		} else {
			wqe->bytes = wqe->sqe.sge[0].length;
			if (!rdma_is_kernel_res(&qp->base_qp.res)) {
				if (wqe->bytes > SIW_MAX_INLINE) {
					rv = -EINVAL;
					goto tx_error;
				}
				wqe->sqe.sge[0].laddr =
					(u64)(uintptr_t)&wqe->sqe.sge[1];
			}
		}
		wqe->wr_status = SIW_WR_INPROGRESS;
		wqe->processed = 0;

		siw_update_tcpseg(c_tx, s);

		rv = siw_qp_prepare_tx(c_tx);
		if (rv == PKT_FRAGMENTED) {
			c_tx->state = SIW_SEND_HDR;
			siw_prepare_fpdu(qp, wqe);
		} else if (rv == PKT_COMPLETE) {
			c_tx->state = SIW_SEND_SHORT_FPDU;
		} else {
			goto tx_error;
		}
	}

next_segment:
	siw_dbg_qp(qp, "wr type %d, state %d, data %u, sent %u, id %llx\n",
		   tx_type(wqe), wqe->wr_status, wqe->bytes, wqe->processed,
		   wqe->sqe.id);

	if (--burst_len == 0) {
		rv = -EINPROGRESS;
		goto tx_done;
	}
	if (c_tx->state == SIW_SEND_SHORT_FPDU) {
		enum siw_opcode tx_type = tx_type(wqe);
		unsigned int msg_flags;

		if (siw_sq_empty(qp) || !siw_tcp_nagle || burst_len == 1)
			/*
			 * End current TCP segment, if SQ runs empty,
			 * or siw_tcp_nagle is not set, or we bail out
			 * soon due to no burst credit left.
			 */
			msg_flags = MSG_DONTWAIT;
		else
			msg_flags = MSG_DONTWAIT | MSG_MORE;

		rv = siw_tx_ctrl(c_tx, s, msg_flags);

		if (!rv && tx_type != SIW_OP_READ &&
		    tx_type != SIW_OP_READ_LOCAL_INV)
			wqe->processed = wqe->bytes;

		goto tx_done;

	} else {
		rv = siw_tx_hdt(c_tx, s);
	}
	if (!rv) {
		/*
		 * One segment sent. Processing completed if last
		 * segment, Do next segment otherwise.
		 */
		if (unlikely(c_tx->tx_suspend)) {
			/*
			 * Verbs, 6.4.: Try stopping sending after a full
			 * DDP segment if the connection goes down
			 * (== peer halfclose)
			 */
			rv = -ECONNABORTED;
			goto tx_done;
		}
		if (c_tx->pkt.ctrl.ddp_rdmap_ctrl & DDP_FLAG_LAST) {
			siw_dbg_qp(qp, "WQE completed\n");
			goto tx_done;
		}
		c_tx->state = SIW_SEND_HDR;

		siw_update_tcpseg(c_tx, s);

		siw_prepare_fpdu(qp, wqe);
		goto next_segment;
	}
tx_done:
	qp->tx_ctx.burst = burst_len;
	return rv;

tx_error:
	if (ecode != RDMAP_ECODE_CATASTROPHIC_STREAM)
		siw_init_terminate(qp, TERM_ERROR_LAYER_RDMAP,
				   RDMAP_ETYPE_REMOTE_PROTECTION, ecode, 1);
	else
		siw_init_terminate(qp, TERM_ERROR_LAYER_RDMAP,
				   RDMAP_ETYPE_CATASTROPHIC,
				   RDMAP_ECODE_UNSPECIFIED, 1);
	return rv;
}

static int siw_fastreg_mr(struct ib_pd *pd, struct siw_sqe *sqe)
{
	struct ib_mr *base_mr = (struct ib_mr *)(uintptr_t)sqe->base_mr;
	struct siw_device *sdev = to_siw_dev(pd->device);
	struct siw_mem *mem;
	int rv = 0;

	siw_dbg_pd(pd, "STag 0x%08x\n", sqe->rkey);

	if (unlikely(!base_mr)) {
		pr_warn("siw: fastreg: STag 0x%08x unknown\n", sqe->rkey);
		return -EINVAL;
	}

	if (unlikely(base_mr->rkey >> 8 != sqe->rkey  >> 8)) {
		pr_warn("siw: fastreg: STag 0x%08x: bad MR\n", sqe->rkey);
		return -EINVAL;
	}

	mem = siw_mem_id2obj(sdev, sqe->rkey  >> 8);
	if (unlikely(!mem)) {
		pr_warn("siw: fastreg: STag 0x%08x unknown\n", sqe->rkey);
		return -EINVAL;
	}

	if (unlikely(mem->pd != pd)) {
		pr_warn("siw: fastreg: PD mismatch\n");
		rv = -EINVAL;
		goto out;
	}
	if (unlikely(mem->stag_valid)) {
		pr_warn("siw: fastreg: STag 0x%08x already valid\n", sqe->rkey);
		rv = -EINVAL;
		goto out;
	}
	/* Refresh STag since user may have changed key part */
	mem->stag = sqe->rkey;
	mem->perms = sqe->access;

	siw_dbg_mem(mem, "STag 0x%08x now valid\n", sqe->rkey);
	mem->va = base_mr->iova;
	mem->stag_valid = 1;
out:
	siw_mem_put(mem);
	return rv;
}

static int siw_qp_sq_proc_local(struct siw_qp *qp, struct siw_wqe *wqe)
{
	int rv;

	switch (tx_type(wqe)) {
	case SIW_OP_REG_MR:
		rv = siw_fastreg_mr(qp->pd, &wqe->sqe);
		break;

	case SIW_OP_INVAL_STAG:
		rv = siw_invalidate_stag(qp->pd, wqe->sqe.rkey);
		break;

	default:
		rv = -EINVAL;
	}
	return rv;
}

/*
 * siw_qp_sq_process()
 *
 * Core TX path routine for RDMAP/DDP/MPA using a TCP kernel socket.
 * Sends RDMAP payload for the current SQ WR @wqe of @qp in one or more
 * MPA FPDUs, each containing a DDP segment.
 *
 * SQ processing may occur in user context as a result of posting
 * new WQE's or from siw_sq_work_handler() context. Processing in
 * user context is limited to non-kernel verbs users.
 *
 * SQ processing may get paused anytime, possibly in the middle of a WR
 * or FPDU, if insufficient send space is available. SQ processing
 * gets resumed from siw_sq_work_handler(), if send space becomes
 * available again.
 *
 * Must be called with the QP state read-locked.
 *
 * Note:
 * An outbound RREQ can be satisfied by the corresponding RRESP
 * _before_ it gets assigned to the ORQ. This happens regularly
 * in RDMA READ via loopback case. Since both outbound RREQ and
 * inbound RRESP can be handled by the same CPU, locking the ORQ
 * is dead-lock prone and thus not an option. With that, the
 * RREQ gets assigned to the ORQ _before_ being sent - see
 * siw_activate_tx() - and pulled back in case of send failure.
 */
int siw_qp_sq_process(struct siw_qp *qp)
{
	struct siw_wqe *wqe = tx_wqe(qp);
	enum siw_opcode tx_type;
	unsigned long flags;
	int rv = 0;

	siw_dbg_qp(qp, "enter for type %d\n", tx_type(wqe));

next_wqe:
	/*
	 * Stop QP processing if SQ state changed
	 */
	if (unlikely(qp->tx_ctx.tx_suspend)) {
		siw_dbg_qp(qp, "tx suspended\n");
		goto done;
	}
	tx_type = tx_type(wqe);

	if (tx_type <= SIW_OP_READ_RESPONSE)
		rv = siw_qp_sq_proc_tx(qp, wqe);
	else
		rv = siw_qp_sq_proc_local(qp, wqe);

	if (!rv) {
		/*
		 * WQE processing done
		 */
		switch (tx_type) {
		case SIW_OP_SEND:
		case SIW_OP_SEND_REMOTE_INV:
		case SIW_OP_WRITE:
			siw_wqe_put_mem(wqe, tx_type);
			fallthrough;

		case SIW_OP_INVAL_STAG:
		case SIW_OP_REG_MR:
			if (tx_flags(wqe) & SIW_WQE_SIGNALLED)
				siw_sqe_complete(qp, &wqe->sqe, wqe->bytes,
						 SIW_WC_SUCCESS);
			break;

		case SIW_OP_READ:
		case SIW_OP_READ_LOCAL_INV:
			/*
			 * already enqueued to ORQ queue
			 */
			break;

		case SIW_OP_READ_RESPONSE:
			siw_wqe_put_mem(wqe, tx_type);
			break;

		default:
			WARN(1, "undefined WQE type %d\n", tx_type);
			rv = -EINVAL;
			goto done;
		}

		spin_lock_irqsave(&qp->sq_lock, flags);
		wqe->wr_status = SIW_WR_IDLE;
		rv = siw_activate_tx(qp);
		spin_unlock_irqrestore(&qp->sq_lock, flags);

		if (rv <= 0)
			goto done;

		goto next_wqe;

	} else if (rv == -EAGAIN) {
		siw_dbg_qp(qp, "sq paused: hd/tr %d of %d, data %d\n",
			   qp->tx_ctx.ctrl_sent, qp->tx_ctx.ctrl_len,
			   qp->tx_ctx.bytes_unsent);
		rv = 0;
		goto done;
	} else if (rv == -EINPROGRESS) {
		rv = siw_sq_start(qp);
		goto done;
	} else {
		/*
		 * WQE processing failed.
		 * Verbs 8.3.2:
		 * o It turns any WQE into a signalled WQE.
		 * o Local catastrophic error must be surfaced
		 * o QP must be moved into Terminate state: done by code
		 *   doing socket state change processing
		 *
		 * o TODO: Termination message must be sent.
		 * o TODO: Implement more precise work completion errors,
		 *         see enum ib_wc_status in ib_verbs.h
		 */
		siw_dbg_qp(qp, "wqe type %d processing failed: %d\n",
			   tx_type(wqe), rv);

		spin_lock_irqsave(&qp->sq_lock, flags);
		/*
		 * RREQ may have already been completed by inbound RRESP!
		 */
		if ((tx_type == SIW_OP_READ ||
		     tx_type == SIW_OP_READ_LOCAL_INV) && qp->attrs.orq_size) {
			/* Cleanup pending entry in ORQ */
			qp->orq_put--;
			qp->orq[qp->orq_put % qp->attrs.orq_size].flags = 0;
		}
		spin_unlock_irqrestore(&qp->sq_lock, flags);
		/*
		 * immediately suspends further TX processing
		 */
		if (!qp->tx_ctx.tx_suspend)
			siw_qp_cm_drop(qp, 0);

		switch (tx_type) {
		case SIW_OP_SEND:
		case SIW_OP_SEND_REMOTE_INV:
		case SIW_OP_SEND_WITH_IMM:
		case SIW_OP_WRITE:
		case SIW_OP_READ:
		case SIW_OP_READ_LOCAL_INV:
			siw_wqe_put_mem(wqe, tx_type);
			fallthrough;

		case SIW_OP_INVAL_STAG:
		case SIW_OP_REG_MR:
			siw_sqe_complete(qp, &wqe->sqe, wqe->bytes,
					 SIW_WC_LOC_QP_OP_ERR);

			siw_qp_event(qp, IB_EVENT_QP_FATAL);

			break;

		case SIW_OP_READ_RESPONSE:
			siw_dbg_qp(qp, "proc. read.response failed: %d\n", rv);

			siw_qp_event(qp, IB_EVENT_QP_REQ_ERR);

			siw_wqe_put_mem(wqe, SIW_OP_READ_RESPONSE);

			break;

		default:
			WARN(1, "undefined WQE type %d\n", tx_type);
			rv = -EINVAL;
		}
		wqe->wr_status = SIW_WR_IDLE;
	}
done:
	return rv;
}

static void siw_sq_resume(struct siw_qp *qp)
{
	if (down_read_trylock(&qp->state_lock)) {
		if (likely(qp->attrs.state == SIW_QP_STATE_RTS &&
			   !qp->tx_ctx.tx_suspend)) {
			int rv = siw_qp_sq_process(qp);

			up_read(&qp->state_lock);

			if (unlikely(rv < 0)) {
				siw_dbg_qp(qp, "SQ task failed: err %d\n", rv);

				if (!qp->tx_ctx.tx_suspend)
					siw_qp_cm_drop(qp, 0);
			}
		} else {
			up_read(&qp->state_lock);
		}
	} else {
		siw_dbg_qp(qp, "Resume SQ while QP locked\n");
	}
	siw_qp_put(qp);
}

struct tx_task_t {
	struct llist_head active;
	wait_queue_head_t waiting;
};

static DEFINE_PER_CPU(struct tx_task_t, siw_tx_task_g);

int siw_create_tx_threads(void)
{
	int cpu, assigned = 0;

	for_each_online_cpu(cpu) {
		struct tx_task_t *tx_task;

		/* Skip HT cores */
		if (cpu % cpumask_weight(topology_sibling_cpumask(cpu)))
			continue;

		tx_task = &per_cpu(siw_tx_task_g, cpu);
		init_llist_head(&tx_task->active);
		init_waitqueue_head(&tx_task->waiting);

		siw_tx_thread[cpu] =
			kthread_run_on_cpu(siw_run_sq,
					   (unsigned long *)(long)cpu,
					   cpu, "siw_tx/%u");
		if (IS_ERR(siw_tx_thread[cpu])) {
			siw_tx_thread[cpu] = NULL;
			continue;
		}
		assigned++;
	}
	return assigned;
}

void siw_stop_tx_threads(void)
{
	int cpu;

	for_each_possible_cpu(cpu) {
		if (siw_tx_thread[cpu]) {
			kthread_stop(siw_tx_thread[cpu]);
			wake_up(&per_cpu(siw_tx_task_g, cpu).waiting);
			siw_tx_thread[cpu] = NULL;
		}
	}
}

int siw_run_sq(void *data)
{
	const int nr_cpu = (unsigned int)(long)data;
	struct llist_node *active;
	struct siw_qp *qp;
	struct tx_task_t *tx_task = &per_cpu(siw_tx_task_g, nr_cpu);

	while (1) {
		struct llist_node *fifo_list = NULL;

		wait_event_interruptible(tx_task->waiting,
					 !llist_empty(&tx_task->active) ||
						 kthread_should_stop());

		if (kthread_should_stop())
			break;

		active = llist_del_all(&tx_task->active);
		/*
		 * llist_del_all returns a list with newest entry first.
		 * Re-order list for fairness among QP's.
		 */
		fifo_list = llist_reverse_order(active);
		while (fifo_list) {
			qp = container_of(fifo_list, struct siw_qp, tx_list);
			fifo_list = llist_next(fifo_list);
			qp->tx_list.next = NULL;

			siw_sq_resume(qp);
		}
	}
	active = llist_del_all(&tx_task->active);
	if (active) {
		llist_for_each_entry(qp, active, tx_list) {
			qp->tx_list.next = NULL;
			siw_sq_resume(qp);
		}
	}
	return 0;
}

int siw_sq_start(struct siw_qp *qp)
{
	if (tx_wqe(qp)->wr_status == SIW_WR_IDLE)
		return 0;

	if (unlikely(!cpu_online(qp->tx_cpu))) {
		siw_put_tx_cpu(qp->tx_cpu);
		qp->tx_cpu = siw_get_tx_cpu(qp->sdev);
		if (qp->tx_cpu < 0) {
			pr_warn("siw: no tx cpu available\n");

			return -EIO;
		}
	}
	siw_qp_get(qp);

	llist_add(&qp->tx_list, &per_cpu(siw_tx_task_g, qp->tx_cpu).active);

	wake_up(&per_cpu(siw_tx_task_g, qp->tx_cpu).waiting);

	return 0;
}