misc: mic: SCIF connections APIs i.e. accept and connect

SCIF connection APIs which establish a SCIF connection between
a pair of SCIF endpoints. A SCIF connection consists of a
dedicated queue-pair between the endpoints. Client messages are
sent over the queue-pair whereas the signaling associated with the
message is multiplexed over the node queue-pair. Similarly other
control messages such as exposing registered memory are also sent
over the node queue-pair. The SCIF endpoints must be in connected
state to exchange messages, register memory, map remote memory and
trigger DMA transfers. SCIF connections can be set up
asynchronously or synchronously.

Thanks to Johnnie S Peters for authoring parts of this patch during
early bring up of the SCIF driver.

Reviewed-by: Ashutosh Dixit <ashutosh.dixit@intel.com>
Signed-off-by: Sudeep Dutt <sudeep.dutt@intel.com>
Signed-off-by: Nikhil Rao <nikhil.rao@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 457 insertions, 0 deletions

diff --git a/drivers/misc/mic/scif/scif_api.c b/drivers/misc/mic/scif/scif_api.c
index cbdc27b3b187..da64cee91908 100644
--- a/drivers/misc/mic/scif/scif_api.c
+++ b/drivers/misc/mic/scif/scif_api.c
@@ -415,3 +415,460 @@ int scif_listen(scif_epd_t epd, int backlog)
 	return 0;
 }
 EXPORT_SYMBOL_GPL(scif_listen);
+
+/*
+ ************************************************************************
+ * SCIF connection flow:
+ *
+ * 1) A SCIF listening endpoint can call scif_accept(..) to wait for SCIF
+ *	connections via a SCIF_CNCT_REQ message
+ * 2) A SCIF endpoint can initiate a SCIF connection by calling
+ *	scif_connect(..) which calls scif_setup_qp_connect(..) which
+ *	allocates the local qp for the endpoint ring buffer and then sends
+ *	a SCIF_CNCT_REQ to the remote node and waits for a SCIF_CNCT_GNT or
+ *	a SCIF_CNCT_REJ message
+ * 3) The peer node handles a SCIF_CNCT_REQ via scif_cnctreq_resp(..) which
+ *	wakes up any threads blocked in step 1 or sends a SCIF_CNCT_REJ
+ *	message otherwise
+ * 4) A thread blocked waiting for incoming connections allocates its local
+ *	endpoint QP and ring buffer following which it sends a SCIF_CNCT_GNT
+ *	and waits for a SCIF_CNCT_GNT(N)ACK. If the allocation fails then
+ *	the node sends a SCIF_CNCT_REJ message
+ * 5) Upon receipt of a SCIF_CNCT_GNT or a SCIF_CNCT_REJ message the
+ *	connecting endpoint is woken up as part of handling
+ *	scif_cnctgnt_resp(..) following which it maps the remote endpoints'
+ *	QP, updates its outbound QP and sends a SCIF_CNCT_GNTACK message on
+ *	success or a SCIF_CNCT_GNTNACK message on failure and completes
+ *	the scif_connect(..) API
+ * 6) Upon receipt of a SCIF_CNCT_GNT(N)ACK the accepting endpoint blocked
+ *	in step 4 is woken up and completes the scif_accept(..) API
+ * 7) The SCIF connection is now established between the two SCIF endpoints.
+ */
+static int scif_conn_func(struct scif_endpt *ep)
+{
+	int err = 0;
+	struct scifmsg msg;
+	struct device *spdev;
+
+	/* Initiate the first part of the endpoint QP setup */
+	err = scif_setup_qp_connect(ep->qp_info.qp, &ep->qp_info.qp_offset,
+				    SCIF_ENDPT_QP_SIZE, ep->remote_dev);
+	if (err) {
+		dev_err(&ep->remote_dev->sdev->dev,
+			"%s err %d qp_offset 0x%llx\n",
+			__func__, err, ep->qp_info.qp_offset);
+		ep->state = SCIFEP_BOUND;
+		goto connect_error_simple;
+	}
+
+	spdev = scif_get_peer_dev(ep->remote_dev);
+	if (IS_ERR(spdev)) {
+		err = PTR_ERR(spdev);
+		goto cleanup_qp;
+	}
+	/* Format connect message and send it */
+	msg.src = ep->port;
+	msg.dst = ep->conn_port;
+	msg.uop = SCIF_CNCT_REQ;
+	msg.payload[0] = (u64)ep;
+	msg.payload[1] = ep->qp_info.qp_offset;
+	err = _scif_nodeqp_send(ep->remote_dev, &msg);
+	if (err)
+		goto connect_error_dec;
+	scif_put_peer_dev(spdev);
+	/*
+	 * Wait for the remote node to respond with SCIF_CNCT_GNT or
+	 * SCIF_CNCT_REJ message.
+	 */
+	err = wait_event_timeout(ep->conwq, ep->state != SCIFEP_CONNECTING,
+				 SCIF_NODE_ALIVE_TIMEOUT);
+	if (!err) {
+		dev_err(&ep->remote_dev->sdev->dev,
+			"%s %d timeout\n", __func__, __LINE__);
+		ep->state = SCIFEP_BOUND;
+	}
+	spdev = scif_get_peer_dev(ep->remote_dev);
+	if (IS_ERR(spdev)) {
+		err = PTR_ERR(spdev);
+		goto cleanup_qp;
+	}
+	if (ep->state == SCIFEP_MAPPING) {
+		err = scif_setup_qp_connect_response(ep->remote_dev,
+						     ep->qp_info.qp,
+						     ep->qp_info.gnt_pld);
+		/*
+		 * If the resource to map the queue are not available then
+		 * we need to tell the other side to terminate the accept
+		 */
+		if (err) {
+			dev_err(&ep->remote_dev->sdev->dev,
+				"%s %d err %d\n", __func__, __LINE__, err);
+			msg.uop = SCIF_CNCT_GNTNACK;
+			msg.payload[0] = ep->remote_ep;
+			_scif_nodeqp_send(ep->remote_dev, &msg);
+			ep->state = SCIFEP_BOUND;
+			goto connect_error_dec;
+		}
+
+		msg.uop = SCIF_CNCT_GNTACK;
+		msg.payload[0] = ep->remote_ep;
+		err = _scif_nodeqp_send(ep->remote_dev, &msg);
+		if (err) {
+			ep->state = SCIFEP_BOUND;
+			goto connect_error_dec;
+		}
+		ep->state = SCIFEP_CONNECTED;
+		mutex_lock(&scif_info.connlock);
+		list_add_tail(&ep->list, &scif_info.connected);
+		mutex_unlock(&scif_info.connlock);
+		dev_dbg(&ep->remote_dev->sdev->dev,
+			"SCIFAPI connect: ep %p connected\n", ep);
+	} else if (ep->state == SCIFEP_BOUND) {
+		dev_dbg(&ep->remote_dev->sdev->dev,
+			"SCIFAPI connect: ep %p connection refused\n", ep);
+		err = -ECONNREFUSED;
+		goto connect_error_dec;
+	}
+	scif_put_peer_dev(spdev);
+	return err;
+connect_error_dec:
+	scif_put_peer_dev(spdev);
+cleanup_qp:
+	scif_cleanup_ep_qp(ep);
+connect_error_simple:
+	return err;
+}
+
+/*
+ * scif_conn_handler:
+ *
+ * Workqueue handler for servicing non-blocking SCIF connect
+ *
+ */
+void scif_conn_handler(struct work_struct *work)
+{
+	struct scif_endpt *ep;
+
+	do {
+		ep = NULL;
+		spin_lock(&scif_info.nb_connect_lock);
+		if (!list_empty(&scif_info.nb_connect_list)) {
+			ep = list_first_entry(&scif_info.nb_connect_list,
+					      struct scif_endpt, conn_list);
+			list_del(&ep->conn_list);
+		}
+		spin_unlock(&scif_info.nb_connect_lock);
+		if (ep)
+			ep->conn_err = scif_conn_func(ep);
+	} while (ep);
+}
+
+int __scif_connect(scif_epd_t epd, struct scif_port_id *dst, bool non_block)
+{
+	struct scif_endpt *ep = (struct scif_endpt *)epd;
+	int err = 0;
+	struct scif_dev *remote_dev;
+	struct device *spdev;
+
+	dev_dbg(scif_info.mdev.this_device, "SCIFAPI connect: ep %p %s\n", ep,
+		scif_ep_states[ep->state]);
+
+	if (!scif_dev || dst->node > scif_info.maxid)
+		return -ENODEV;
+
+	might_sleep();
+
+	remote_dev = &scif_dev[dst->node];
+	spdev = scif_get_peer_dev(remote_dev);
+	if (IS_ERR(spdev)) {
+		err = PTR_ERR(spdev);
+		return err;
+	}
+
+	spin_lock(&ep->lock);
+	switch (ep->state) {
+	case SCIFEP_ZOMBIE:
+	case SCIFEP_CLOSING:
+		err = -EINVAL;
+		break;
+	case SCIFEP_DISCONNECTED:
+		if (ep->conn_async_state == ASYNC_CONN_INPROGRESS)
+			ep->conn_async_state = ASYNC_CONN_FLUSH_WORK;
+		else
+			err = -EINVAL;
+		break;
+	case SCIFEP_LISTENING:
+	case SCIFEP_CLLISTEN:
+		err = -EOPNOTSUPP;
+		break;
+	case SCIFEP_CONNECTING:
+	case SCIFEP_MAPPING:
+		if (ep->conn_async_state == ASYNC_CONN_INPROGRESS)
+			err = -EINPROGRESS;
+		else
+			err = -EISCONN;
+		break;
+	case SCIFEP_CONNECTED:
+		if (ep->conn_async_state == ASYNC_CONN_INPROGRESS)
+			ep->conn_async_state = ASYNC_CONN_FLUSH_WORK;
+		else
+			err = -EISCONN;
+		break;
+	case SCIFEP_UNBOUND:
+		ep->port.port = scif_get_new_port();
+		if (!ep->port.port) {
+			err = -ENOSPC;
+		} else {
+			ep->port.node = scif_info.nodeid;
+			ep->conn_async_state = ASYNC_CONN_IDLE;
+		}
+		/* Fall through */
+	case SCIFEP_BOUND:
+		/*
+		 * If a non-blocking connect has been already initiated
+		 * (conn_async_state is either ASYNC_CONN_INPROGRESS or
+		 * ASYNC_CONN_FLUSH_WORK), the end point could end up in
+		 * SCIF_BOUND due an error in the connection process
+		 * (e.g., connection refused) If conn_async_state is
+		 * ASYNC_CONN_INPROGRESS - transition to ASYNC_CONN_FLUSH_WORK
+		 * so that the error status can be collected. If the state is
+		 * already ASYNC_CONN_FLUSH_WORK - then set the error to
+		 * EINPROGRESS since some other thread is waiting to collect
+		 * error status.
+		 */
+		if (ep->conn_async_state == ASYNC_CONN_INPROGRESS) {
+			ep->conn_async_state = ASYNC_CONN_FLUSH_WORK;
+		} else if (ep->conn_async_state == ASYNC_CONN_FLUSH_WORK) {
+			err = -EINPROGRESS;
+		} else {
+			ep->conn_port = *dst;
+			init_waitqueue_head(&ep->sendwq);
+			init_waitqueue_head(&ep->recvwq);
+			init_waitqueue_head(&ep->conwq);
+			ep->conn_async_state = 0;
+
+			if (unlikely(non_block))
+				ep->conn_async_state = ASYNC_CONN_INPROGRESS;
+		}
+		break;
+	}
+
+	if (err || ep->conn_async_state == ASYNC_CONN_FLUSH_WORK)
+			goto connect_simple_unlock1;
+
+	ep->state = SCIFEP_CONNECTING;
+	ep->remote_dev = &scif_dev[dst->node];
+	ep->qp_info.qp->magic = SCIFEP_MAGIC;
+	if (ep->conn_async_state == ASYNC_CONN_INPROGRESS) {
+		spin_lock(&scif_info.nb_connect_lock);
+		list_add_tail(&ep->conn_list, &scif_info.nb_connect_list);
+		spin_unlock(&scif_info.nb_connect_lock);
+		err = -EINPROGRESS;
+		schedule_work(&scif_info.conn_work);
+	}
+connect_simple_unlock1:
+	spin_unlock(&ep->lock);
+	scif_put_peer_dev(spdev);
+	if (err) {
+		return err;
+	} else if (ep->conn_async_state == ASYNC_CONN_FLUSH_WORK) {
+		flush_work(&scif_info.conn_work);
+		err = ep->conn_err;
+		spin_lock(&ep->lock);
+		ep->conn_async_state = ASYNC_CONN_IDLE;
+		spin_unlock(&ep->lock);
+	} else {
+		err = scif_conn_func(ep);
+	}
+	return err;
+}
+
+int scif_connect(scif_epd_t epd, struct scif_port_id *dst)
+{
+	return __scif_connect(epd, dst, false);
+}
+EXPORT_SYMBOL_GPL(scif_connect);
+
+/**
+ * scif_accept() - Accept a connection request from the remote node
+ *
+ * The function accepts a connection request from the remote node.  Successful
+ * complete is indicate by a new end point being created and passed back
+ * to the caller for future reference.
+ *
+ * Upon successful complete a zero will be returned and the peer information
+ * will be filled in.
+ *
+ * If the end point is not in the listening state -EINVAL will be returned.
+ *
+ * If during the connection sequence resource allocation fails the -ENOMEM
+ * will be returned.
+ *
+ * If the function is called with the ASYNC flag set and no connection requests
+ * are pending it will return -EAGAIN.
+ *
+ * If the remote side is not sending any connection requests the caller may
+ * terminate this function with a signal.  If so a -EINTR will be returned.
+ */
+int scif_accept(scif_epd_t epd, struct scif_port_id *peer,
+		scif_epd_t *newepd, int flags)
+{
+	struct scif_endpt *lep = (struct scif_endpt *)epd;
+	struct scif_endpt *cep;
+	struct scif_conreq *conreq;
+	struct scifmsg msg;
+	int err;
+	struct device *spdev;
+
+	dev_dbg(scif_info.mdev.this_device,
+		"SCIFAPI accept: ep %p %s\n", lep, scif_ep_states[lep->state]);
+
+	if (flags & ~SCIF_ACCEPT_SYNC)
+		return -EINVAL;
+
+	if (!peer || !newepd)
+		return -EINVAL;
+
+	might_sleep();
+	spin_lock(&lep->lock);
+	if (lep->state != SCIFEP_LISTENING) {
+		spin_unlock(&lep->lock);
+		return -EINVAL;
+	}
+
+	if (!lep->conreqcnt && !(flags & SCIF_ACCEPT_SYNC)) {
+		/* No connection request present and we do not want to wait */
+		spin_unlock(&lep->lock);
+		return -EAGAIN;
+	}
+
+	lep->files = current->files;
+retry_connection:
+	spin_unlock(&lep->lock);
+	/* Wait for the remote node to send us a SCIF_CNCT_REQ */
+	err = wait_event_interruptible(lep->conwq,
+				       (lep->conreqcnt ||
+				       (lep->state != SCIFEP_LISTENING)));
+	if (err)
+		return err;
+
+	if (lep->state != SCIFEP_LISTENING)
+		return -EINTR;
+
+	spin_lock(&lep->lock);
+
+	if (!lep->conreqcnt)
+		goto retry_connection;
+
+	/* Get the first connect request off the list */
+	conreq = list_first_entry(&lep->conlist, struct scif_conreq, list);
+	list_del(&conreq->list);
+	lep->conreqcnt--;
+	spin_unlock(&lep->lock);
+
+	/* Fill in the peer information */
+	peer->node = conreq->msg.src.node;
+	peer->port = conreq->msg.src.port;
+
+	cep = kzalloc(sizeof(*cep), GFP_KERNEL);
+	if (!cep) {
+		err = -ENOMEM;
+		goto scif_accept_error_epalloc;
+	}
+	spin_lock_init(&cep->lock);
+	mutex_init(&cep->sendlock);
+	mutex_init(&cep->recvlock);
+	cep->state = SCIFEP_CONNECTING;
+	cep->remote_dev = &scif_dev[peer->node];
+	cep->remote_ep = conreq->msg.payload[0];
+
+	cep->qp_info.qp = kzalloc(sizeof(*cep->qp_info.qp), GFP_KERNEL);
+	if (!cep->qp_info.qp) {
+		err = -ENOMEM;
+		goto scif_accept_error_qpalloc;
+	}
+
+	cep->qp_info.qp->magic = SCIFEP_MAGIC;
+	spdev = scif_get_peer_dev(cep->remote_dev);
+	if (IS_ERR(spdev)) {
+		err = PTR_ERR(spdev);
+		goto scif_accept_error_map;
+	}
+	err = scif_setup_qp_accept(cep->qp_info.qp, &cep->qp_info.qp_offset,
+				   conreq->msg.payload[1], SCIF_ENDPT_QP_SIZE,
+				   cep->remote_dev);
+	if (err) {
+		dev_dbg(&cep->remote_dev->sdev->dev,
+			"SCIFAPI accept: ep %p new %p scif_setup_qp_accept %d qp_offset 0x%llx\n",
+			lep, cep, err, cep->qp_info.qp_offset);
+		scif_put_peer_dev(spdev);
+		goto scif_accept_error_map;
+	}
+
+	cep->port.node = lep->port.node;
+	cep->port.port = lep->port.port;
+	cep->peer.node = peer->node;
+	cep->peer.port = peer->port;
+	init_waitqueue_head(&cep->sendwq);
+	init_waitqueue_head(&cep->recvwq);
+	init_waitqueue_head(&cep->conwq);
+
+	msg.uop = SCIF_CNCT_GNT;
+	msg.src = cep->port;
+	msg.payload[0] = cep->remote_ep;
+	msg.payload[1] = cep->qp_info.qp_offset;
+	msg.payload[2] = (u64)cep;
+
+	err = _scif_nodeqp_send(cep->remote_dev, &msg);
+	scif_put_peer_dev(spdev);
+	if (err)
+		goto scif_accept_error_map;
+retry:
+	/* Wait for the remote node to respond with SCIF_CNCT_GNT(N)ACK */
+	err = wait_event_timeout(cep->conwq, cep->state != SCIFEP_CONNECTING,
+				 SCIF_NODE_ACCEPT_TIMEOUT);
+	if (!err && scifdev_alive(cep))
+		goto retry;
+	err = !err ? -ENODEV : 0;
+	if (err)
+		goto scif_accept_error_map;
+	kfree(conreq);
+
+	spin_lock(&cep->lock);
+
+	if (cep->state == SCIFEP_CLOSING) {
+		/*
+		 * Remote failed to allocate resources and NAKed the grant.
+		 * There is at this point nothing referencing the new end point.
+		 */
+		spin_unlock(&cep->lock);
+		scif_teardown_ep(cep);
+		kfree(cep);
+
+		/* If call with sync flag then go back and wait. */
+		if (flags & SCIF_ACCEPT_SYNC) {
+			spin_lock(&lep->lock);
+			goto retry_connection;
+		}
+		return -EAGAIN;
+	}
+
+	scif_get_port(cep->port.port);
+	*newepd = (scif_epd_t)cep;
+	spin_unlock(&cep->lock);
+	return 0;
+scif_accept_error_map:
+	scif_teardown_ep(cep);
+scif_accept_error_qpalloc:
+	kfree(cep);
+scif_accept_error_epalloc:
+	msg.uop = SCIF_CNCT_REJ;
+	msg.dst.node = conreq->msg.src.node;
+	msg.dst.port = conreq->msg.src.port;
+	msg.payload[0] = conreq->msg.payload[0];
+	msg.payload[1] = conreq->msg.payload[1];
+	scif_nodeqp_send(&scif_dev[conreq->msg.src.node], &msg);
+	kfree(conreq);
+	return err;
+}
+EXPORT_SYMBOL_GPL(scif_accept);