[vmw_vmci 05/11] Apply VMCI event code

[Andrew Stiegmann (stieg)]

Code that manages event handlers and handles callbacks when
specific events fire.

Signed-off-by: Andrew Stiegmann (stieg) <astiegmann@xxxxxxxxxx>
---
 drivers/misc/vmw_vmci/vmci_event.c |  451 ++++++++++++++++++++++++++++++++++++
 drivers/misc/vmw_vmci/vmci_event.h |   29 +++
 2 files changed, 480 insertions(+), 0 deletions(-)
 create mode 100644 drivers/misc/vmw_vmci/vmci_event.c
 create mode 100644 drivers/misc/vmw_vmci/vmci_event.h

diff --git a/drivers/misc/vmw_vmci/vmci_event.c b/drivers/misc/vmw_vmci/vmci_event.c
new file mode 100644
index 0000000..bc4e976
--- /dev/null
+++ b/drivers/misc/vmw_vmci/vmci_event.c
@@ -0,0 +1,451 @@
+/*
+ * VMware VMCI Driver
+ *
+ * Copyright (C) 2012 VMware, Inc. All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the
+ * Free Software Foundation version 2 and no later version.
+ *
+ * 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.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin St, Fifth Floor, Boston, MA  02110-1301 USA
+ */
+
+#include <linux/module.h>
+#include <linux/list.h>
+#include <linux/sched.h>
+#include <linux/vmw_vmci_api.h>
+#include <linux/vmw_vmci_defs.h>
+
+#include "vmci_event.h"
+#include "vmci_driver.h"
+
+#define EVENT_MAGIC 0xEABE0000
+#define VMCI_EVENT_MAX_ATTEMPTS 10
+
+struct vmci_subscription {
+	uint32_t id;
+	int refCount;
+	bool runDelayed;
+	wait_queue_head_t destroyEvent;
+	uint32_t event;
+	VMCI_EventCB callback;
+	void *callbackData;
+	struct list_head subscriberListItem;
+};
+
+static struct list_head subscriberArray[VMCI_EVENT_MAX];
+static spinlock_t subscriberLock;
+
+struct delayed_event_info {
+	struct vmci_subscription *sub;
+	uint8_t eventPayload[sizeof(struct vmci_event_data_max)];
+};
+
+struct event_ref {
+	struct vmci_subscription *sub;
+	struct list_head listItem;
+};
+
+int __init vmci_event_init(void)
+{
+	int i;
+
+	for (i = 0; i < VMCI_EVENT_MAX; i++)
+		INIT_LIST_HEAD(&subscriberArray[i]);
+
+	spin_lock_init(&subscriberLock);
+	return VMCI_SUCCESS;
+}
+
+void vmci_event_exit(void)
+{
+	int e;
+
+	/* We free all memory at exit. */
+	for (e = 0; e < VMCI_EVENT_MAX; e++) {
+		struct vmci_subscription *cur, *p2;
+		list_for_each_entry_safe(cur, p2, &subscriberArray[e],
+					 subscriberListItem) {
+
+			/*
+			 * We should never get here because all events
+			 * should have been unregistered before we try
+			 * to unload the driver module.  Also, delayed
+			 * callbacks could still be firing so this
+			 * cleanup would not be safe.  Still it is
+			 * better to free the memory than not ... so
+			 * we leave this code in just in case....
+			 */
+			pr_warn("Unexpected free events occuring.");
+			kfree(cur);
+		}
+	}
+
+}
+
+/*
+ * Gets a reference to the given VMCISubscription.
+ */
+static void event_get(struct vmci_subscription *entry)
+{
+	ASSERT(entry);
+
+	entry->refCount++;
+}
+
+/*
+ * Releases the given VMCISubscription.
+ * Fires the destroy event if the reference count has gone to zero.
+ */
+static void event_release(struct vmci_subscription *entry)
+{
+	ASSERT(entry);
+	ASSERT(entry->refCount > 0);
+
+	entry->refCount--;
+	if (entry->refCount == 0)
+		wake_up(&entry->destroyEvent);
+}
+
+/*
+ * Callback to release the event entry reference. It is called by the
+ * VMCI_WaitOnEvent function before it blocks.
+ */
+static int event_release_cb(void *clientData)
+{
+	struct vmci_subscription *sub = (struct vmci_subscription *)clientData;
+
+	ASSERT(sub);
+
+	spin_lock_bh(&subscriberLock);
+	event_release(sub);
+	spin_unlock_bh(&subscriberLock);
+
+	return 0;
+}
+
+/*
+ * Find entry. Assumes lock is held.
+ * Increments the VMCISubscription refcount if an entry is found.
+ */
+static struct vmci_subscription *event_find(uint32_t subID)
+{
+	int e;
+
+	for (e = 0; e < VMCI_EVENT_MAX; e++) {
+		struct vmci_subscription *cur;
+		list_for_each_entry(cur, &subscriberArray[e],
+				    subscriberListItem) {
+			if (cur->id == subID) {
+				event_get(cur);
+				return cur;
+			}
+		}
+	}
+	return NULL;
+}
+
+/*
+ * Calls the specified callback in a delayed context.
+ */
+static void event_delayed_dispatch_cb(void *data)
+{
+	struct delayed_event_info *eventInfo;
+	struct vmci_subscription *sub;
+	struct vmci_event_data *ed;
+
+	eventInfo = data;
+
+	ASSERT(eventInfo);
+	ASSERT(eventInfo->sub);
+
+	sub = eventInfo->sub;
+	ed = (struct vmci_event_data *)eventInfo->eventPayload;
+
+	sub->callback(sub->id, ed, sub->callbackData);
+
+	spin_lock_bh(&subscriberLock);
+	event_release(sub);
+	spin_unlock_bh(&subscriberLock);
+
+	kfree(eventInfo);
+}
+
+/*
+ * Actually delivers the events to the subscribers.
+ * The callback function for each subscriber is invoked.
+ */
+static int event_deliver(struct vmci_event_msg *eventMsg)
+{
+	int err = VMCI_SUCCESS;
+	struct vmci_subscription *cur;
+	struct list_head noDelayList;
+	struct vmci_event_data *ed;
+	struct event_ref *eventRef, *p2;
+
+	ASSERT(eventMsg);
+
+	INIT_LIST_HEAD(&noDelayList);
+
+	spin_lock_bh(&subscriberLock);
+	list_for_each_entry(cur, &subscriberArray[eventMsg->eventData.event],
+			    subscriberListItem) {
+		ASSERT(cur && cur->event == eventMsg->eventData.event);
+
+		if (cur->runDelayed) {
+			struct delayed_event_info *eventInfo;
+			eventInfo = kzalloc(sizeof *eventInfo, GFP_ATOMIC);
+			if (!eventInfo) {
+				err = VMCI_ERROR_NO_MEM;
+				goto out;
+			}
+
+			event_get(cur);
+			memcpy(eventInfo->eventPayload,
+			       VMCI_DG_PAYLOAD(eventMsg),
+			       (size_t) eventMsg->hdr.payloadSize);
+			eventInfo->sub = cur;
+			err = vmci_drv_schedule_delayed_work(
+				event_delayed_dispatch_cb,
+				eventInfo);
+			if (err != VMCI_SUCCESS) {
+				event_release(cur);
+				kfree(eventInfo);
+				goto out;
+			}
+
+		} else {
+			/*
+			 * To avoid possible lock rank voilation when holding
+			 * subscriberLock, we construct a local list of
+			 * subscribers and release subscriberLock before
+			 * invokes the callbacks. This is similar to delayed
+			 * callbacks, but callbacks is invoked right away here.
+			 */
+			eventRef = kzalloc(sizeof *eventRef, GFP_ATOMIC);
+			if (!eventRef) {
+				err = VMCI_ERROR_NO_MEM;
+				goto out;
+			}
+
+			event_get(cur);
+			eventRef->sub = cur;
+			INIT_LIST_HEAD(&eventRef->listItem);
+			list_add(&eventRef->listItem, &noDelayList);
+		}
+	}
+
+out:
+	spin_unlock_bh(&subscriberLock);
+
+	list_for_each_entry_safe(eventRef, p2, &noDelayList, listItem) {
+		uint8_t eventPayload[sizeof(struct vmci_event_data_max)]
+			= { 0 };
+
+		/*
+		 * We set event data before each callback to ensure
+		 * isolation.
+		 */
+		memcpy(eventPayload, VMCI_DG_PAYLOAD(eventMsg),
+		       (size_t) eventMsg->hdr.payloadSize);
+		ed = (struct vmci_event_data *)eventPayload;
+		cur = eventRef->sub;
+		cur->callback(cur->id, ed, cur->callbackData);
+
+		spin_lock_bh(&subscriberLock);
+		event_release(cur);
+		spin_unlock_bh(&subscriberLock);
+		kfree(eventRef);
+	}
+
+	return err;
+}
+
+/*
+ * Dispatcher for the VMCI_EVENT_RECEIVE datagrams. Calls all
+ * subscribers for given event.
+ */
+int vmci_event_dispatch(struct vmci_dg *msg)
+{
+	struct vmci_event_msg *eventMsg = (struct vmci_event_msg *)msg;
+
+	ASSERT(msg &&
+	       msg->src.context == VMCI_HYPERVISOR_CONTEXT_ID &&
+	       msg->dst.resource == VMCI_EVENT_HANDLER);
+
+	if (msg->payloadSize < sizeof(uint32_t) ||
+	    msg->payloadSize > sizeof(struct vmci_event_data_max))
+		return VMCI_ERROR_INVALID_ARGS;
+
+	if (!VMCI_EVENT_VALID(eventMsg->eventData.event))
+		return VMCI_ERROR_EVENT_UNKNOWN;
+
+	event_deliver(eventMsg);
+	return VMCI_SUCCESS;
+}
+
+/*
+ * Initialize and add subscription to subscriber list.
+ */
+static int event_register_subscription(struct vmci_subscription *sub,
+				       uint32_t event,
+				       uint32_t flags,
+				       VMCI_EventCB callback,
+				       void *callbackData)
+{
+	static uint32_t subscriptionID;
+	uint32_t attempts = 0;
+	int result;
+	bool success;
+
+	ASSERT(sub);
+
+	if (!VMCI_EVENT_VALID(event) || callback == NULL) {
+		pr_devel("Failed to subscribe to event (type=%d) " \
+			 "(callback=%p) (data=%p).", event,
+			 callback, callbackData);
+		return VMCI_ERROR_INVALID_ARGS;
+	}
+
+	sub->runDelayed = !!(flags & VMCI_FLAG_EVENT_DELAYED_CB);
+	sub->refCount = 1;
+	sub->event = event;
+	sub->callback = callback;
+	sub->callbackData = callbackData;
+	INIT_LIST_HEAD(&sub->subscriberListItem);
+
+	spin_lock_bh(&subscriberLock);
+
+	/* Creation of a new event is always allowed. */
+	for (success = false, attempts = 0;
+	     success == false && attempts < VMCI_EVENT_MAX_ATTEMPTS;
+	     attempts++) {
+		struct vmci_subscription *existingSub = NULL;
+
+		/*
+		 * We try to get an id a couple of time before
+		 * claiming we are out of resources.
+		 */
+		sub->id = ++subscriptionID;
+
+		/* Test for duplicate id. */
+		existingSub = event_find(sub->id);
+		if (existingSub == NULL)
+			success = true;
+		else
+			event_release(existingSub);
+	}
+
+	if (success) {
+		init_waitqueue_head(&sub->destroyEvent);
+		list_add(&sub->subscriberListItem, &subscriberArray[event]);
+		result = VMCI_SUCCESS;
+	} else {
+		result = VMCI_ERROR_NO_RESOURCES;
+	}
+
+	spin_unlock_bh(&subscriberLock);
+	return result;
+}
+
+/*
+ * Remove subscription from subscriber list.
+ */
+static struct vmci_subscription *event_unregister_subscription(uint32_t subID)
+{
+	struct vmci_subscription *s;
+
+	spin_lock_bh(&subscriberLock);
+	s = event_find(subID);
+	if (s != NULL) {
+		event_release(s);
+		list_del(&s->subscriberListItem);
+	}
+	spin_unlock_bh(&subscriberLock);
+
+	if (s != NULL)
+		vmci_drv_wait_on_event_intr(&s->destroyEvent,
+					    event_release_cb, s);
+
+	return s;
+}
+
+/**
+ * VMCIEvent_Subscribe() - Subscribe to a given event.
+ * @event:	The event to subscribe to.
+ * @flags:	Event flags.  VMCI_FLAG_EVENT_*
+ * @callback:	The callback to invoke upon the event.
+ * @callbackData:	Data to pass to the callback.
+ * @subscriptionID:	ID used to track subscription.  Used with
+ *		VMCIEvent_Unsubscribe()
+ *
+ * Subscribes to the provided event.  The callback specified can be fired
+ * in different contexts depending on what flag is specified while
+ * registering. If flags contains VMCI_FLAG_EVENT_NONE then the
+ * callback is fired with the subscriber lock held (and BH context
+ * on the guest). If flags contain VMCI_FLAG_EVENT_DELAYED_CB then
+ * the callback is fired with no locks held in thread context.
+ * This is useful because other VMCIEvent functions can be called,
+ * but it also increases the chances that an event will be dropped.
+ */
+int VMCIEvent_Subscribe(uint32_t event,
+			uint32_t flags,
+			VMCI_EventCB callback,
+			void *callbackData,
+			uint32_t *subscriptionID)
+{
+	int retval;
+	struct vmci_subscription *s = NULL;
+
+	if (subscriptionID == NULL) {
+		pr_devel("Invalid subscription (NULL).");
+		return VMCI_ERROR_INVALID_ARGS;
+	}
+
+	s = kmalloc(sizeof *s, GFP_KERNEL);
+	if (s == NULL)
+		return VMCI_ERROR_NO_MEM;
+
+	retval = event_register_subscription(s, event, flags,
+					     callback, callbackData);
+	if (retval < VMCI_SUCCESS) {
+		kfree(s);
+		return retval;
+	}
+
+	*subscriptionID = s->id;
+	return retval;
+}
+EXPORT_SYMBOL(VMCIEvent_Subscribe);
+
+/**
+ * VMCIEvent_Unsubscribe() - Unsubscribe to an event.
+ * @subID:	A subscription ID ad provided by VMCIEvent_Subscribe()
+ *
+ * Unsubscribe to given event. Removes it from list and frees it.
+ * Will return callbackData if requested by caller.
+ */
+int VMCIEvent_Unsubscribe(uint32_t subID)
+{
+	struct vmci_subscription *s;
+
+	/*
+	 * Return subscription. At this point we know noone else is accessing
+	 * the subscription so we can free it.
+	 */
+	s = event_unregister_subscription(subID);
+	if (s == NULL)
+		return VMCI_ERROR_NOT_FOUND;
+
+	kfree(s);
+
+	return VMCI_SUCCESS;
+}
+EXPORT_SYMBOL(VMCIEvent_Unsubscribe);
diff --git a/drivers/misc/vmw_vmci/vmci_event.h b/drivers/misc/vmw_vmci/vmci_event.h
new file mode 100644
index 0000000..83574c6
--- /dev/null
+++ b/drivers/misc/vmw_vmci/vmci_event.h
@@ -0,0 +1,29 @@
+/*
+ * VMware VMCI Driver
+ *
+ * Copyright (C) 2012 VMware, Inc. All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the
+ * Free Software Foundation version 2 and no later version.
+ *
+ * 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.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin St, Fifth Floor, Boston, MA  02110-1301 USA
+ */
+
+#ifndef __VMCI_EVENT_H__
+#define __VMCI_EVENT_H__
+
+#include <linux/vmw_vmci_api.h>
+
+int vmci_event_init(void);
+void vmci_event_exit(void);
+int vmci_event_dispatch(struct vmci_dg *msg);
+
+#endif /*__VMCI_EVENT_H__ */
-- 
1.7.0.4

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