misc: mic: COSM SCIF server

The COSM driver communicates with the MIC cards over SCIF. A SCIF
"server" listens for incoming connections from "client" MIC cards as
they boot. After the connection is accepted a separate work item is
scheduled for each MIC card. This work item normally stays blocked in
scif_poll but wakes up to process messages from the card.

The SCIF connection between the host and card COSM components is used
to (a) send the command to shut down the card (b) receive shutdown
status back from the card upon completion of shutdown (c) receive
periodic heartbeat messages to detect card crashes (d) send host time
to the card to enable the card to sync its time to the host.
Reviewed-by: Nikhil Rao <nikhil.rao@intel.com>
Reviewed-by: Sudeep Dutt <sudeep.dutt@intel.com>
Signed-off-by: Ashutosh Dixit <ashutosh.dixit@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/misc/mic/cosm/cosm_scif_server.c

+/*
+ * Intel MIC Platform Software Stack (MPSS)
+ *
+ * Copyright(c) 2015 Intel Corporation.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License, version 2, as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * General Public License for more details.
+ *
+ * The full GNU General Public License is included in this distribution in
+ * the file called "COPYING".
+ *
+ * Intel MIC Coprocessor State Management (COSM) Driver
+ *
+ */
+#include <linux/kthread.h>
+#include "cosm_main.h"
+
+/*
+ * The COSM driver uses SCIF to communicate between the management node and the
+ * MIC cards. SCIF is used to (a) Send a shutdown command to the card (b)
+ * receive a shutdown status back from the card upon completion of shutdown and
+ * (c) receive periodic heartbeat messages from the card used to deduce if the
+ * card has crashed.
+ *
+ * A COSM server consisting of a SCIF listening endpoint waits for incoming
+ * connections from the card. Upon acceptance of the connection, a separate
+ * work-item is scheduled to handle SCIF message processing for that card. The
+ * life-time of this work-item is therefore the time from which the connection
+ * from a card is accepted to the time at which the connection is closed. A new
+ * work-item starts each time the card boots and is alive till the card (a)
+ * shuts down (b) is reset (c) crashes (d) cosm_client driver on the card is
+ * unloaded.
+ *
+ * From the point of view of COSM interactions with SCIF during card
+ * shutdown, reset and crash are as follows:
+ *
+ * Card shutdown
+ * -------------
+ * 1. COSM client on the card invokes orderly_poweroff() in response to SHUTDOWN
+ *    message from the host.
+ * 2. Card driver shutdown callback invokes scif_unregister_device(..) resulting
+ *    in scif_remove(..) getting called on the card
+ * 3. scif_remove -> scif_stop -> scif_handle_remove_node ->
+ *    scif_peer_unregister_device -> device_unregister for the host peer device
+ * 4. During device_unregister remove(..) method of cosm_client is invoked which
+ *    closes the COSM SCIF endpoint on the card. This results in a SCIF_DISCNCT
+ *    message being sent to host SCIF. SCIF_DISCNCT message processing on the
+ *    host SCIF sets the host COSM SCIF endpoint state to DISCONNECTED and wakes
+ *    up the host COSM thread blocked in scif_poll(..) resulting in
+ *    scif_poll(..)  returning POLLHUP.
+ * 5. On the card, scif_peer_release_dev is next called which results in an
+ *    SCIF_EXIT message being sent to the host and after receiving the
+ *    SCIF_EXIT_ACK from the host the peer device teardown on the card is
+ *    complete.
+ * 6. As part of the SCIF_EXIT message processing on the host, host sends a
+ *    SCIF_REMOVE_NODE to itself corresponding to the card being removed. This
+ *    starts a similar SCIF peer device teardown sequence on the host
+ *    corresponding to the card being shut down.
+ *
+ * Card reset
+ * ----------
+ * The case of interest here is when the card has not been previously shut down
+ * since most of the steps below are skipped in that case:
+
+ * 1. cosm_stop(..) invokes hw_ops->stop(..) method of the base PCIe driver
+ *    which unregisters the SCIF HW device resulting in scif_remove(..) being
+ *    called on the host.
+ * 2. scif_remove(..) calls scif_disconnect_node(..) which results in a
+ *    SCIF_EXIT message being sent to the card.
+ * 3. The card executes scif_stop() as part of SCIF_EXIT message
+ *    processing. This results in the COSM endpoint on the card being closed and
+ *    the SCIF host peer device on the card getting unregistered similar to
+ *    steps 3, 4 and 5 for the card shutdown case above. scif_poll(..) on the
+ *    host returns POLLHUP as a result.
+ * 4. On the host, card peer device unregister and SCIF HW remove(..) also
+ *    subsequently complete.
+ *
+ * Card crash
+ * ----------
+ * If a reset is issued after the card has crashed, there is no SCIF_DISCNT
+ * message from the card which would result in scif_poll(..) returning
+ * POLLHUP. In this case when the host SCIF driver sends a SCIF_REMOVE_NODE
+ * message to itself resulting in the card SCIF peer device being unregistered,
+ * this results in a scif_peer_release_dev -> scif_cleanup_scifdev->
+ * scif_invalidate_ep call sequence which sets the endpoint state to
+ * DISCONNECTED and results in scif_poll(..) returning POLLHUP.
+ */
+
+#define COSM_SCIF_BACKLOG 16
+#define COSM_HEARTBEAT_CHECK_DELTA_SEC 10
+#define COSM_HEARTBEAT_TIMEOUT_SEC \
+		(COSM_HEARTBEAT_SEND_SEC + COSM_HEARTBEAT_CHECK_DELTA_SEC)
+#define COSM_HEARTBEAT_TIMEOUT_MSEC (COSM_HEARTBEAT_TIMEOUT_SEC * MSEC_PER_SEC)
+
+static struct task_struct *server_thread;
+static scif_epd_t listen_epd;
+
+/* Publish MIC card's shutdown status to user space MIC daemon */
+static void cosm_update_mic_status(struct cosm_device *cdev)
+{
+	if (cdev->shutdown_status_int != MIC_NOP) {
+		cosm_set_shutdown_status(cdev, cdev->shutdown_status_int);
+		cdev->shutdown_status_int = MIC_NOP;
+	}
+}
+
+/* Store MIC card's shutdown status internally when it is received */
+static void cosm_shutdown_status_int(struct cosm_device *cdev,
+				     enum mic_status shutdown_status)
+{
+	switch (shutdown_status) {
+	case MIC_HALTED:
+	case MIC_POWER_OFF:
+	case MIC_RESTART:
+	case MIC_CRASHED:
+		break;
+	default:
+		dev_err(&cdev->dev, "%s %d Unexpected shutdown_status %d\n",
+			__func__, __LINE__, shutdown_status);
+		return;
+	};
+	cdev->shutdown_status_int = shutdown_status;
+	cdev->heartbeat_watchdog_enable = false;
+
+	if (cdev->state != MIC_SHUTTING_DOWN)
+		cosm_set_state(cdev, MIC_SHUTTING_DOWN);
+}
+
+/* Non-blocking recv. Read and process all available messages */
+static void cosm_scif_recv(struct cosm_device *cdev)
+{
+	struct cosm_msg msg;
+	int rc;
+
+	while (1) {
+		rc = scif_recv(cdev->epd, &msg, sizeof(msg), 0);
+		if (!rc) {
+			break;
+		} else if (rc < 0) {
+			dev_dbg(&cdev->dev, "%s: %d rc %d\n",
+				__func__, __LINE__, rc);
+			break;
+		}
+		dev_dbg(&cdev->dev, "%s: %d rc %d id 0x%llx\n",
+			__func__, __LINE__, rc, msg.id);
+
+		switch (msg.id) {
+		case COSM_MSG_SHUTDOWN_STATUS:
+			cosm_shutdown_status_int(cdev, msg.shutdown_status);
+			break;
+		case COSM_MSG_HEARTBEAT:
+			/* Nothing to do, heartbeat only unblocks scif_poll */
+			break;
+		default:
+			dev_err(&cdev->dev, "%s: %d unknown msg.id %lld\n",
+				__func__, __LINE__, msg.id);
+			break;
+		}
+	}
+}
+
+/* Publish crashed status for this MIC card */
+static void cosm_set_crashed(struct cosm_device *cdev)
+{
+	dev_err(&cdev->dev, "node alive timeout\n");
+	cosm_shutdown_status_int(cdev, MIC_CRASHED);
+	cosm_update_mic_status(cdev);
+}
+
+/* Send host time to the MIC card to sync system time between host and MIC */
+static void cosm_send_time(struct cosm_device *cdev)
+{
+	struct cosm_msg msg = { .id = COSM_MSG_SYNC_TIME };
+	int rc;
+
+	getnstimeofday64(&msg.timespec);
+	rc = scif_send(cdev->epd, &msg, sizeof(msg), SCIF_SEND_BLOCK);
+	if (rc < 0)
+		dev_err(&cdev->dev, "%s %d scif_send failed rc %d\n",
+			__func__, __LINE__, rc);
+}
+
+/*
+ * Close this cosm_device's endpoint after its peer endpoint on the card has
+ * been closed. In all cases except MIC card crash POLLHUP on the host is
+ * triggered by the client's endpoint being closed.
+ */
+static void cosm_scif_close(struct cosm_device *cdev)
+{
+	/*
+	 * Because SHUTDOWN_STATUS message is sent by the MIC cards in the
+	 * reboot notifier when shutdown is still not complete, we notify mpssd
+	 * to reset the card when SCIF endpoint is closed.
+	 */
+	cosm_update_mic_status(cdev);
+	scif_close(cdev->epd);
+	cdev->epd = NULL;
+	dev_dbg(&cdev->dev, "%s %d\n", __func__, __LINE__);
+}
+
+/*
+ * Set card state to ONLINE when a new SCIF connection from a MIC card is
+ * received. Normally the state is BOOTING when the connection comes in, but can
+ * be ONLINE if cosm_client driver on the card was unloaded and then reloaded.
+ */
+static int cosm_set_online(struct cosm_device *cdev)
+{
+	int rc = 0;
+
+	if (MIC_BOOTING == cdev->state || MIC_ONLINE == cdev->state) {
+		cdev->heartbeat_watchdog_enable = cdev->sysfs_heartbeat_enable;
+		cdev->epd = cdev->newepd;
+		if (cdev->state == MIC_BOOTING)
+			cosm_set_state(cdev, MIC_ONLINE);
+		cosm_send_time(cdev);
+		dev_dbg(&cdev->dev, "%s %d\n", __func__, __LINE__);
+	} else {
+		dev_warn(&cdev->dev, "%s %d not going online in state: %s\n",
+			 __func__, __LINE__, cosm_state_string[cdev->state]);
+		rc = -EINVAL;
+	}
+	/* Drop reference acquired by bus_find_device in the server thread */
+	put_device(&cdev->dev);
+	return rc;
+}
+
+/*
+ * Work function for handling work for a SCIF connection from a particular MIC
+ * card. It first sets the card state to ONLINE and then calls scif_poll to
+ * block on activity such as incoming messages on the SCIF endpoint. When the
+ * endpoint is closed, the work function exits, completing its life cycle, from
+ * MIC card boot to card shutdown/reset/crash.
+ */
+void cosm_scif_work(struct work_struct *work)
+{
+	struct cosm_device *cdev = container_of(work, struct cosm_device,
+						scif_work);
+	struct scif_pollepd pollepd;
+	int rc;
+
+	mutex_lock(&cdev->cosm_mutex);
+	if (cosm_set_online(cdev))
+		goto exit;
+
+	while (1) {
+		pollepd.epd = cdev->epd;
+		pollepd.events = POLLIN;
+
+		/* Drop the mutex before blocking in scif_poll(..) */
+		mutex_unlock(&cdev->cosm_mutex);
+		/* poll(..) with timeout on our endpoint */
+		rc = scif_poll(&pollepd, 1, COSM_HEARTBEAT_TIMEOUT_MSEC);
+		mutex_lock(&cdev->cosm_mutex);
+		if (rc < 0) {
+			dev_err(&cdev->dev, "%s %d scif_poll rc %d\n",
+				__func__, __LINE__, rc);
+			continue;
+		}
+
+		/* There is a message from the card */
+		if (pollepd.revents & POLLIN)
+			cosm_scif_recv(cdev);
+
+		/* The peer endpoint is closed or this endpoint disconnected */
+		if (pollepd.revents & POLLHUP) {
+			cosm_scif_close(cdev);
+			break;
+		}
+
+		/* Did we timeout from poll? */
+		if (!rc && cdev->heartbeat_watchdog_enable)
+			cosm_set_crashed(cdev);
+	}
+exit:
+	dev_dbg(&cdev->dev, "%s %d exiting\n", __func__, __LINE__);
+	mutex_unlock(&cdev->cosm_mutex);
+}
+
+/*
+ * COSM SCIF server thread function. Accepts incoming SCIF connections from MIC
+ * cards, finds the correct cosm_device to associate that connection with and
+ * schedules individual work items for each MIC card.
+ */
+static int cosm_scif_server(void *unused)
+{
+	struct cosm_device *cdev;
+	scif_epd_t newepd;
+	struct scif_port_id port_id;
+	int rc;
+
+	allow_signal(SIGKILL);
+
+	while (!kthread_should_stop()) {
+		rc = scif_accept(listen_epd, &port_id, &newepd,
+				 SCIF_ACCEPT_SYNC);
+		if (rc < 0) {
+			if (-ERESTARTSYS != rc)
+				pr_err("%s %d rc %d\n", __func__, __LINE__, rc);
+			continue;
+		}
+
+		/*
+		 * Associate the incoming connection with a particular
+		 * cosm_device, COSM device ID == SCIF node ID - 1
+		 */
+		cdev = cosm_find_cdev_by_id(port_id.node - 1);
+		if (!cdev)
+			continue;
+		cdev->newepd = newepd;
+		schedule_work(&cdev->scif_work);
+	}
+
+	pr_debug("%s %d Server thread stopped\n", __func__, __LINE__);
+	return 0;
+}
+
+static int cosm_scif_listen(void)
+{
+	int rc;
+
+	listen_epd = scif_open();
+	if (!listen_epd) {
+		pr_err("%s %d scif_open failed\n", __func__, __LINE__);
+		return -ENOMEM;
+	}
+
+	rc = scif_bind(listen_epd, SCIF_COSM_LISTEN_PORT);
+	if (rc < 0) {
+		pr_err("%s %d scif_bind failed rc %d\n",
+		       __func__, __LINE__, rc);
+		goto err;
+	}
+
+	rc = scif_listen(listen_epd, COSM_SCIF_BACKLOG);
+	if (rc < 0) {
+		pr_err("%s %d scif_listen rc %d\n", __func__, __LINE__, rc);
+		goto err;
+	}
+	pr_debug("%s %d listen_epd set up\n", __func__, __LINE__);
+	return 0;
+err:
+	scif_close(listen_epd);
+	listen_epd = NULL;
+	return rc;
+}
+
+static void cosm_scif_listen_exit(void)
+{
+	pr_debug("%s %d closing listen_epd\n", __func__, __LINE__);
+	if (listen_epd) {
+		scif_close(listen_epd);
+		listen_epd = NULL;
+	}
+}
+
+/*
+ * Create a listening SCIF endpoint and a server kthread which accepts incoming
+ * SCIF connections from MIC cards
+ */
+int cosm_scif_init(void)
+{
+	int rc = cosm_scif_listen();
+
+	if (rc) {
+		pr_err("%s %d cosm_scif_listen rc %d\n",
+		       __func__, __LINE__, rc);
+		goto err;
+	}
+
+	server_thread = kthread_run(cosm_scif_server, NULL, "cosm_server");
+	if (IS_ERR(server_thread)) {
+		rc = PTR_ERR(server_thread);
+		pr_err("%s %d kthread_run rc %d\n", __func__, __LINE__, rc);
+		goto listen_exit;
+	}
+	return 0;
+listen_exit:
+	cosm_scif_listen_exit();
+err:
+	return rc;
+}
+
+/* Stop the running server thread and close the listening SCIF endpoint */
+void cosm_scif_exit(void)
+{
+	int rc;
+
+	if (!IS_ERR_OR_NULL(server_thread)) {
+		rc = send_sig(SIGKILL, server_thread, 0);
+		if (rc) {
+			pr_err("%s %d send_sig rc %d\n",
+			       __func__, __LINE__, rc);
+			return;
+		}
+		kthread_stop(server_thread);
+	}
+
+	cosm_scif_listen_exit();
+}