drivers/misc/vmw_vmci/vmci_datagram.c - kernel/bruno - Git at Google

 /*
  * 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.
  */

 #include <linux/vmw_vmci_defs.h>
 #include <linux/vmw_vmci_api.h>
 #include <linux/module.h>
 #include <linux/sched.h>
 #include <linux/slab.h>
 #include <linux/bug.h>

 #include "vmci_datagram.h"
 #include "vmci_resource.h"
 #include "vmci_context.h"
 #include "vmci_driver.h"
 #include "vmci_event.h"
 #include "vmci_route.h"

 /*
  * struct datagram_entry describes the datagram entity. It is used for datagram
  * entities created only on the host.
  */
 struct datagram_entry {
 	struct vmci_resource resource;
 	u32 flags;
 	bool run_delayed;
 	vmci_datagram_recv_cb recv_cb;
 	void *client_data;
 	u32 priv_flags;
 };

 struct delayed_datagram_info {
 	struct datagram_entry *entry;
 	struct work_struct work;
 	bool in_dg_host_queue;
 	/* msg and msg_payload must be together. */
 	struct vmci_datagram msg;
 	u8 msg_payload[];
 };

 /* Number of in-flight host->host datagrams */
 static atomic_t delayed_dg_host_queue_size = ATOMIC_INIT(0);

 /*
  * Create a datagram entry given a handle pointer.
  */
 static int dg_create_handle(u32 resource_id,
 			    u32 flags,
 			    u32 priv_flags,
 			    vmci_datagram_recv_cb recv_cb,
 			    void *client_data, struct vmci_handle *out_handle)
 {
 	int result;
 	u32 context_id;
 	struct vmci_handle handle;
 	struct datagram_entry *entry;

 	if ((flags & VMCI_FLAG_WELLKNOWN_DG_HND) != 0)
 		return VMCI_ERROR_INVALID_ARGS;

 	if ((flags & VMCI_FLAG_ANYCID_DG_HND) != 0) {
 		context_id = VMCI_INVALID_ID;
 	} else {
 		context_id = vmci_get_context_id();
 		if (context_id == VMCI_INVALID_ID)
 			return VMCI_ERROR_NO_RESOURCES;
 	}

 	handle = vmci_make_handle(context_id, resource_id);

 	entry = kmalloc(sizeof(*entry), GFP_KERNEL);
 	if (!entry) {
 		pr_warn("Failed allocating memory for datagram entry\n");
 		return VMCI_ERROR_NO_MEM;
 	}

 	entry->run_delayed = (flags & VMCI_FLAG_DG_DELAYED_CB) ? true : false;
 	entry->flags = flags;
 	entry->recv_cb = recv_cb;
 	entry->client_data = client_data;
 	entry->priv_flags = priv_flags;

 	/* Make datagram resource live. */
 	result = vmci_resource_add(&entry->resource,
 				   VMCI_RESOURCE_TYPE_DATAGRAM,
 				   handle);
 	if (result != VMCI_SUCCESS) {
 		pr_warn("Failed to add new resource (handle=0x%x:0x%x), error: %d\n",
 			handle.context, handle.resource, result);
 		kfree(entry);
 		return result;
 	}

 	*out_handle = vmci_resource_handle(&entry->resource);
 	return VMCI_SUCCESS;
 }

 /*
  * Internal utility function with the same purpose as
  * vmci_datagram_get_priv_flags that also takes a context_id.
  */
 static int vmci_datagram_get_priv_flags(u32 context_id,
 					struct vmci_handle handle,
 					u32 *priv_flags)
 {
 	if (context_id == VMCI_INVALID_ID)
 		return VMCI_ERROR_INVALID_ARGS;

 	if (context_id == VMCI_HOST_CONTEXT_ID) {
 		struct datagram_entry *src_entry;
 		struct vmci_resource *resource;

 		resource = vmci_resource_by_handle(handle,
 						   VMCI_RESOURCE_TYPE_DATAGRAM);
 		if (!resource)
 			return VMCI_ERROR_INVALID_ARGS;

 		src_entry = container_of(resource, struct datagram_entry,
 					 resource);
 		*priv_flags = src_entry->priv_flags;
 		vmci_resource_put(resource);
 	} else if (context_id == VMCI_HYPERVISOR_CONTEXT_ID)
 		*priv_flags = VMCI_MAX_PRIVILEGE_FLAGS;
 	else
 		*priv_flags = vmci_context_get_priv_flags(context_id);

 	return VMCI_SUCCESS;
 }

 /*
  * Calls the specified callback in a delayed context.
  */
 static void dg_delayed_dispatch(struct work_struct *work)
 {
 	struct delayed_datagram_info *dg_info =
 			container_of(work, struct delayed_datagram_info, work);

 	dg_info->entry->recv_cb(dg_info->entry->client_data, &dg_info->msg);

 	vmci_resource_put(&dg_info->entry->resource);

 	if (dg_info->in_dg_host_queue)
 		atomic_dec(&delayed_dg_host_queue_size);

 	kfree(dg_info);
 }

 /*
  * Dispatch datagram as a host, to the host, or other vm context. This
  * function cannot dispatch to hypervisor context handlers. This should
  * have been handled before we get here by vmci_datagram_dispatch.
  * Returns number of bytes sent on success, error code otherwise.
  */
 static int dg_dispatch_as_host(u32 context_id, struct vmci_datagram *dg)
 {
 	int retval;
 	size_t dg_size;
 	u32 src_priv_flags;

 	dg_size = VMCI_DG_SIZE(dg);

 	/* Host cannot send to the hypervisor. */
 	if (dg->dst.context == VMCI_HYPERVISOR_CONTEXT_ID)
 		return VMCI_ERROR_DST_UNREACHABLE;

 	/* Check that source handle matches sending context. */
 	if (dg->src.context != context_id) {
 		pr_devel("Sender context (ID=0x%x) is not owner of src datagram entry (handle=0x%x:0x%x)\n",
 			 context_id, dg->src.context, dg->src.resource);
 		return VMCI_ERROR_NO_ACCESS;
 	}

 	/* Get hold of privileges of sending endpoint. */
 	retval = vmci_datagram_get_priv_flags(context_id, dg->src,
 					      &src_priv_flags);
 	if (retval != VMCI_SUCCESS) {
 		pr_warn("Couldn't get privileges (handle=0x%x:0x%x)\n",
 			dg->src.context, dg->src.resource);
 		return retval;
 	}

 	/* Determine if we should route to host or guest destination. */
 	if (dg->dst.context == VMCI_HOST_CONTEXT_ID) {
 		/* Route to host datagram entry. */
 		struct datagram_entry *dst_entry;
 		struct vmci_resource *resource;

 		if (dg->src.context == VMCI_HYPERVISOR_CONTEXT_ID &&
 		    dg->dst.resource == VMCI_EVENT_HANDLER) {
 			return vmci_event_dispatch(dg);
 		}

 		resource = vmci_resource_by_handle(dg->dst,
 						   VMCI_RESOURCE_TYPE_DATAGRAM);
 		if (!resource) {
 			pr_devel("Sending to invalid destination (handle=0x%x:0x%x)\n",
 				 dg->dst.context, dg->dst.resource);
 			return VMCI_ERROR_INVALID_RESOURCE;
 		}
 		dst_entry = container_of(resource, struct datagram_entry,
 					 resource);
 		if (vmci_deny_interaction(src_priv_flags,
 					  dst_entry->priv_flags)) {
 			vmci_resource_put(resource);
 			return VMCI_ERROR_NO_ACCESS;
 		}

 		/*
 		 * If a VMCI datagram destined for the host is also sent by the
 		 * host, we always run it delayed. This ensures that no locks
 		 * are held when the datagram callback runs.
 		 */
 		if (dst_entry->run_delayed ||
 		    dg->src.context == VMCI_HOST_CONTEXT_ID) {
 			struct delayed_datagram_info *dg_info;

 			if (atomic_add_return(1, &delayed_dg_host_queue_size)
 			    == VMCI_MAX_DELAYED_DG_HOST_QUEUE_SIZE) {
 				atomic_dec(&delayed_dg_host_queue_size);
 				vmci_resource_put(resource);
 				return VMCI_ERROR_NO_MEM;
 			}

 			dg_info = kmalloc(sizeof(*dg_info) +
 				    (size_t) dg->payload_size, GFP_ATOMIC);
 			if (!dg_info) {
 				atomic_dec(&delayed_dg_host_queue_size);
 				vmci_resource_put(resource);
 				return VMCI_ERROR_NO_MEM;
 			}

 			dg_info->in_dg_host_queue = true;
 			dg_info->entry = dst_entry;
 			memcpy(&dg_info->msg, dg, dg_size);

 			INIT_WORK(&dg_info->work, dg_delayed_dispatch);
 			schedule_work(&dg_info->work);
 			retval = VMCI_SUCCESS;

 		} else {
 			retval = dst_entry->recv_cb(dst_entry->client_data, dg);
 			vmci_resource_put(resource);
 			if (retval < VMCI_SUCCESS)
 				return retval;
 		}
 	} else {
 		/* Route to destination VM context. */
 		struct vmci_datagram *new_dg;

 		if (context_id != dg->dst.context) {
 			if (vmci_deny_interaction(src_priv_flags,
 						  vmci_context_get_priv_flags
 						  (dg->dst.context))) {
 				return VMCI_ERROR_NO_ACCESS;
 			} else if (VMCI_CONTEXT_IS_VM(context_id)) {
 				/*
 				 * If the sending context is a VM, it
 				 * cannot reach another VM.
 				 */

 				pr_devel("Datagram communication between VMs not supported (src=0x%x, dst=0x%x)\n",
 					 context_id, dg->dst.context);
 				return VMCI_ERROR_DST_UNREACHABLE;
 			}
 		}

 		/* We make a copy to enqueue. */
 		new_dg = kmemdup(dg, dg_size, GFP_KERNEL);
 		if (new_dg == NULL)
 			return VMCI_ERROR_NO_MEM;

 		retval = vmci_ctx_enqueue_datagram(dg->dst.context, new_dg);
 		if (retval < VMCI_SUCCESS) {
 			kfree(new_dg);
 			return retval;
 		}
 	}

 	/*
 	 * We currently truncate the size to signed 32 bits. This doesn't
 	 * matter for this handler as it only support 4Kb messages.
 	 */
 	return (int)dg_size;
 }

 /*
  * Dispatch datagram as a guest, down through the VMX and potentially to
  * the host.
  * Returns number of bytes sent on success, error code otherwise.
  */
 static int dg_dispatch_as_guest(struct vmci_datagram *dg)
 {
 	int retval;
 	struct vmci_resource *resource;

 	resource = vmci_resource_by_handle(dg->src,
 					   VMCI_RESOURCE_TYPE_DATAGRAM);
 	if (!resource)
 		return VMCI_ERROR_NO_HANDLE;

 	retval = vmci_send_datagram(dg);
 	vmci_resource_put(resource);
 	return retval;
 }

 /*
  * Dispatch datagram.  This will determine the routing for the datagram
  * and dispatch it accordingly.
  * Returns number of bytes sent on success, error code otherwise.
  */
 int vmci_datagram_dispatch(u32 context_id,
 			   struct vmci_datagram *dg, bool from_guest)
 {
 	int retval;
 	enum vmci_route route;

 	BUILD_BUG_ON(sizeof(struct vmci_datagram) != 24);

 	if (dg->payload_size > VMCI_MAX_DG_SIZE ||
 	    VMCI_DG_SIZE(dg) > VMCI_MAX_DG_SIZE) {
 		pr_devel("Payload (size=%llu bytes) too big to send\n",
 			 (unsigned long long)dg->payload_size);
 		return VMCI_ERROR_INVALID_ARGS;
 	}

 	retval = vmci_route(&dg->src, &dg->dst, from_guest, &route);
 	if (retval < VMCI_SUCCESS) {
 		pr_devel("Failed to route datagram (src=0x%x, dst=0x%x, err=%d)\n",
 			 dg->src.context, dg->dst.context, retval);
 		return retval;
 	}

 	if (VMCI_ROUTE_AS_HOST == route) {
 		if (VMCI_INVALID_ID == context_id)
 			context_id = VMCI_HOST_CONTEXT_ID;
 		return dg_dispatch_as_host(context_id, dg);
 	}

 	if (VMCI_ROUTE_AS_GUEST == route)
 		return dg_dispatch_as_guest(dg);

 	pr_warn("Unknown route (%d) for datagram\n", route);
 	return VMCI_ERROR_DST_UNREACHABLE;
 }

 /*
  * Invoke the handler for the given datagram.  This is intended to be
  * called only when acting as a guest and receiving a datagram from the
  * virtual device.
  */
 int vmci_datagram_invoke_guest_handler(struct vmci_datagram *dg)
 {
 	struct vmci_resource *resource;
 	struct datagram_entry *dst_entry;

 	resource = vmci_resource_by_handle(dg->dst,
 					   VMCI_RESOURCE_TYPE_DATAGRAM);
 	if (!resource) {
 		pr_devel("destination (handle=0x%x:0x%x) doesn't exist\n",
 			 dg->dst.context, dg->dst.resource);
 		return VMCI_ERROR_NO_HANDLE;
 	}

 	dst_entry = container_of(resource, struct datagram_entry, resource);
 	if (dst_entry->run_delayed) {
 		struct delayed_datagram_info *dg_info;

 		dg_info = kmalloc(sizeof(*dg_info) + (size_t)dg->payload_size,
 				  GFP_ATOMIC);
 		if (!dg_info) {
 			vmci_resource_put(resource);
 			return VMCI_ERROR_NO_MEM;
 		}

 		dg_info->in_dg_host_queue = false;
 		dg_info->entry = dst_entry;
 		memcpy(&dg_info->msg, dg, VMCI_DG_SIZE(dg));

 		INIT_WORK(&dg_info->work, dg_delayed_dispatch);
 		schedule_work(&dg_info->work);
 	} else {
 		dst_entry->recv_cb(dst_entry->client_data, dg);
 		vmci_resource_put(resource);
 	}

 	return VMCI_SUCCESS;
 }

 /*
  * vmci_datagram_create_handle_priv() - Create host context datagram endpoint
  * @resource_id:        The resource ID.
  * @flags:      Datagram Flags.
  * @priv_flags: Privilege Flags.
  * @recv_cb:    Callback when receiving datagrams.
  * @client_data:        Pointer for a datagram_entry struct
  * @out_handle: vmci_handle that is populated as a result of this function.
  *
  * Creates a host context datagram endpoint and returns a handle to it.
  */
 int vmci_datagram_create_handle_priv(u32 resource_id,
 				     u32 flags,
 				     u32 priv_flags,
 				     vmci_datagram_recv_cb recv_cb,
 				     void *client_data,
 				     struct vmci_handle *out_handle)
 {
 	if (out_handle == NULL)
 		return VMCI_ERROR_INVALID_ARGS;

 	if (recv_cb == NULL) {
 		pr_devel("Client callback needed when creating datagram\n");
 		return VMCI_ERROR_INVALID_ARGS;
 	}

 	if (priv_flags & ~VMCI_PRIVILEGE_ALL_FLAGS)
 		return VMCI_ERROR_INVALID_ARGS;

 	return dg_create_handle(resource_id, flags, priv_flags, recv_cb,
 				client_data, out_handle);
 }
 EXPORT_SYMBOL_GPL(vmci_datagram_create_handle_priv);

 /*
  * vmci_datagram_create_handle() - Create host context datagram endpoint
  * @resource_id:        Resource ID.
  * @flags:      Datagram Flags.
  * @recv_cb:    Callback when receiving datagrams.
  * @client_ata: Pointer for a datagram_entry struct
  * @out_handle: vmci_handle that is populated as a result of this function.
  *
  * Creates a host context datagram endpoint and returns a handle to
  * it.  Same as vmci_datagram_create_handle_priv without the priviledge
  * flags argument.
  */
 int vmci_datagram_create_handle(u32 resource_id,
 				u32 flags,
 				vmci_datagram_recv_cb recv_cb,
 				void *client_data,
 				struct vmci_handle *out_handle)
 {
 	return vmci_datagram_create_handle_priv(
 		resource_id, flags,
 		VMCI_DEFAULT_PROC_PRIVILEGE_FLAGS,
 		recv_cb, client_data,
 		out_handle);
 }
 EXPORT_SYMBOL_GPL(vmci_datagram_create_handle);

 /*
  * vmci_datagram_destroy_handle() - Destroys datagram handle
  * @handle:     vmci_handle to be destroyed and reaped.
  *
  * Use this function to destroy any datagram handles created by
  * vmci_datagram_create_handle{,Priv} functions.
  */
 int vmci_datagram_destroy_handle(struct vmci_handle handle)
 {
 	struct datagram_entry *entry;
 	struct vmci_resource *resource;

 	resource = vmci_resource_by_handle(handle, VMCI_RESOURCE_TYPE_DATAGRAM);
 	if (!resource) {
 		pr_devel("Failed to destroy datagram (handle=0x%x:0x%x)\n",
 			 handle.context, handle.resource);
 		return VMCI_ERROR_NOT_FOUND;
 	}

 	entry = container_of(resource, struct datagram_entry, resource);

 	vmci_resource_put(&entry->resource);
 	vmci_resource_remove(&entry->resource);
 	kfree(entry);

 	return VMCI_SUCCESS;
 }
 EXPORT_SYMBOL_GPL(vmci_datagram_destroy_handle);

 /*
  * vmci_datagram_send() - Send a datagram
  * @msg:        The datagram to send.
  *
  * Sends the provided datagram on its merry way.
  */
 int vmci_datagram_send(struct vmci_datagram *msg)
 {
 	if (msg == NULL)
 		return VMCI_ERROR_INVALID_ARGS;

 	return vmci_datagram_dispatch(VMCI_INVALID_ID, msg, false);
 }
 EXPORT_SYMBOL_GPL(vmci_datagram_send);
	/*
	* 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.
	*/

	#include <linux/vmw_vmci_defs.h>
	#include <linux/vmw_vmci_api.h>
	#include <linux/module.h>
	#include <linux/sched.h>
	#include <linux/slab.h>
	#include <linux/bug.h>

	#include "vmci_datagram.h"
	#include "vmci_resource.h"
	#include "vmci_context.h"
	#include "vmci_driver.h"
	#include "vmci_event.h"
	#include "vmci_route.h"

	/*
	* struct datagram_entry describes the datagram entity. It is used for datagram
	* entities created only on the host.
	*/
	struct datagram_entry {
	struct vmci_resource resource;
	u32 flags;
	bool run_delayed;
	vmci_datagram_recv_cb recv_cb;
	void *client_data;
	u32 priv_flags;
	};

	struct delayed_datagram_info {
	struct datagram_entry *entry;
	struct work_struct work;
	bool in_dg_host_queue;
	/* msg and msg_payload must be together. */
	struct vmci_datagram msg;
	u8 msg_payload[];
	};

	/* Number of in-flight host->host datagrams */
	static atomic_t delayed_dg_host_queue_size = ATOMIC_INIT(0);

	/*
	* Create a datagram entry given a handle pointer.
	*/
	static int dg_create_handle(u32 resource_id,
	u32 flags,
	u32 priv_flags,
	vmci_datagram_recv_cb recv_cb,
	void client_data, struct vmci_handle out_handle)
	{
	int result;
	u32 context_id;
	struct vmci_handle handle;
	struct datagram_entry *entry;

	if ((flags & VMCI_FLAG_WELLKNOWN_DG_HND) != 0)
	return VMCI_ERROR_INVALID_ARGS;

	if ((flags & VMCI_FLAG_ANYCID_DG_HND) != 0) {
	context_id = VMCI_INVALID_ID;
	} else {
	context_id = vmci_get_context_id();
	if (context_id == VMCI_INVALID_ID)
	return VMCI_ERROR_NO_RESOURCES;
	}

	handle = vmci_make_handle(context_id, resource_id);

	entry = kmalloc(sizeof(*entry), GFP_KERNEL);
	if (!entry) {
	pr_warn("Failed allocating memory for datagram entry\n");
	return VMCI_ERROR_NO_MEM;
	}

	entry->run_delayed = (flags & VMCI_FLAG_DG_DELAYED_CB) ? true : false;
	entry->flags = flags;
	entry->recv_cb = recv_cb;
	entry->client_data = client_data;
	entry->priv_flags = priv_flags;

	/* Make datagram resource live. */
	result = vmci_resource_add(&entry->resource,
	VMCI_RESOURCE_TYPE_DATAGRAM,
	handle);
	if (result != VMCI_SUCCESS) {
	pr_warn("Failed to add new resource (handle=0x%x:0x%x), error: %d\n",
	handle.context, handle.resource, result);
	kfree(entry);
	return result;
	}

	*out_handle = vmci_resource_handle(&entry->resource);
	return VMCI_SUCCESS;
	}

	/*
	* Internal utility function with the same purpose as
	* vmci_datagram_get_priv_flags that also takes a context_id.
	*/
	static int vmci_datagram_get_priv_flags(u32 context_id,
	struct vmci_handle handle,
	u32 *priv_flags)
	{
	if (context_id == VMCI_INVALID_ID)
	return VMCI_ERROR_INVALID_ARGS;

	if (context_id == VMCI_HOST_CONTEXT_ID) {
	struct datagram_entry *src_entry;
	struct vmci_resource *resource;

	resource = vmci_resource_by_handle(handle,
	VMCI_RESOURCE_TYPE_DATAGRAM);
	if (!resource)
	return VMCI_ERROR_INVALID_ARGS;

	src_entry = container_of(resource, struct datagram_entry,
	resource);
	*priv_flags = src_entry->priv_flags;
	vmci_resource_put(resource);
	} else if (context_id == VMCI_HYPERVISOR_CONTEXT_ID)
	*priv_flags = VMCI_MAX_PRIVILEGE_FLAGS;
	else
	*priv_flags = vmci_context_get_priv_flags(context_id);

	return VMCI_SUCCESS;
	}

	/*
	* Calls the specified callback in a delayed context.
	*/
	static void dg_delayed_dispatch(struct work_struct *work)
	{
	struct delayed_datagram_info *dg_info =
	container_of(work, struct delayed_datagram_info, work);

	dg_info->entry->recv_cb(dg_info->entry->client_data, &dg_info->msg);

	vmci_resource_put(&dg_info->entry->resource);

	if (dg_info->in_dg_host_queue)
	atomic_dec(&delayed_dg_host_queue_size);

	kfree(dg_info);
	}

	/*
	* Dispatch datagram as a host, to the host, or other vm context. This
	* function cannot dispatch to hypervisor context handlers. This should
	* have been handled before we get here by vmci_datagram_dispatch.
	* Returns number of bytes sent on success, error code otherwise.
	*/
	static int dg_dispatch_as_host(u32 context_id, struct vmci_datagram *dg)
	{
	int retval;
	size_t dg_size;
	u32 src_priv_flags;

	dg_size = VMCI_DG_SIZE(dg);

	/* Host cannot send to the hypervisor. */
	if (dg->dst.context == VMCI_HYPERVISOR_CONTEXT_ID)
	return VMCI_ERROR_DST_UNREACHABLE;

	/* Check that source handle matches sending context. */
	if (dg->src.context != context_id) {
	pr_devel("Sender context (ID=0x%x) is not owner of src datagram entry (handle=0x%x:0x%x)\n",
	context_id, dg->src.context, dg->src.resource);
	return VMCI_ERROR_NO_ACCESS;
	}

	/* Get hold of privileges of sending endpoint. */
	retval = vmci_datagram_get_priv_flags(context_id, dg->src,
	&src_priv_flags);
	if (retval != VMCI_SUCCESS) {
	pr_warn("Couldn't get privileges (handle=0x%x:0x%x)\n",
	dg->src.context, dg->src.resource);
	return retval;
	}

	/* Determine if we should route to host or guest destination. */
	if (dg->dst.context == VMCI_HOST_CONTEXT_ID) {
	/* Route to host datagram entry. */
	struct datagram_entry *dst_entry;
	struct vmci_resource *resource;

	if (dg->src.context == VMCI_HYPERVISOR_CONTEXT_ID &&
	dg->dst.resource == VMCI_EVENT_HANDLER) {
	return vmci_event_dispatch(dg);
	}

	resource = vmci_resource_by_handle(dg->dst,
	VMCI_RESOURCE_TYPE_DATAGRAM);
	if (!resource) {
	pr_devel("Sending to invalid destination (handle=0x%x:0x%x)\n",
	dg->dst.context, dg->dst.resource);
	return VMCI_ERROR_INVALID_RESOURCE;
	}
	dst_entry = container_of(resource, struct datagram_entry,
	resource);
	if (vmci_deny_interaction(src_priv_flags,
	dst_entry->priv_flags)) {
	vmci_resource_put(resource);
	return VMCI_ERROR_NO_ACCESS;
	}

	/*
	* If a VMCI datagram destined for the host is also sent by the
	* host, we always run it delayed. This ensures that no locks
	* are held when the datagram callback runs.
	*/
	if (dst_entry->run_delayed \|\|
	dg->src.context == VMCI_HOST_CONTEXT_ID) {
	struct delayed_datagram_info *dg_info;

	if (atomic_add_return(1, &delayed_dg_host_queue_size)
	== VMCI_MAX_DELAYED_DG_HOST_QUEUE_SIZE) {
	atomic_dec(&delayed_dg_host_queue_size);
	vmci_resource_put(resource);
	return VMCI_ERROR_NO_MEM;
	}

	dg_info = kmalloc(sizeof(*dg_info) +
	(size_t) dg->payload_size, GFP_ATOMIC);
	if (!dg_info) {
	atomic_dec(&delayed_dg_host_queue_size);
	vmci_resource_put(resource);
	return VMCI_ERROR_NO_MEM;
	}

	dg_info->in_dg_host_queue = true;
	dg_info->entry = dst_entry;
	memcpy(&dg_info->msg, dg, dg_size);

	INIT_WORK(&dg_info->work, dg_delayed_dispatch);
	schedule_work(&dg_info->work);
	retval = VMCI_SUCCESS;

	} else {
	retval = dst_entry->recv_cb(dst_entry->client_data, dg);
	vmci_resource_put(resource);
	if (retval < VMCI_SUCCESS)
	return retval;
	}
	} else {
	/* Route to destination VM context. */
	struct vmci_datagram *new_dg;

	if (context_id != dg->dst.context) {
	if (vmci_deny_interaction(src_priv_flags,
	vmci_context_get_priv_flags
	(dg->dst.context))) {
	return VMCI_ERROR_NO_ACCESS;
	} else if (VMCI_CONTEXT_IS_VM(context_id)) {
	/*
	* If the sending context is a VM, it
	* cannot reach another VM.
	*/

	pr_devel("Datagram communication between VMs not supported (src=0x%x, dst=0x%x)\n",
	context_id, dg->dst.context);
	return VMCI_ERROR_DST_UNREACHABLE;
	}
	}

	/* We make a copy to enqueue. */
	new_dg = kmemdup(dg, dg_size, GFP_KERNEL);
	if (new_dg == NULL)
	return VMCI_ERROR_NO_MEM;

	retval = vmci_ctx_enqueue_datagram(dg->dst.context, new_dg);
	if (retval < VMCI_SUCCESS) {
	kfree(new_dg);
	return retval;
	}
	}

	/*
	* We currently truncate the size to signed 32 bits. This doesn't
	* matter for this handler as it only support 4Kb messages.
	*/
	return (int)dg_size;
	}

	/*
	* Dispatch datagram as a guest, down through the VMX and potentially to
	* the host.
	* Returns number of bytes sent on success, error code otherwise.
	*/
	static int dg_dispatch_as_guest(struct vmci_datagram *dg)
	{
	int retval;
	struct vmci_resource *resource;

	resource = vmci_resource_by_handle(dg->src,
	VMCI_RESOURCE_TYPE_DATAGRAM);
	if (!resource)
	return VMCI_ERROR_NO_HANDLE;

	retval = vmci_send_datagram(dg);
	vmci_resource_put(resource);
	return retval;
	}

	/*
	* Dispatch datagram. This will determine the routing for the datagram
	* and dispatch it accordingly.
	* Returns number of bytes sent on success, error code otherwise.
	*/
	int vmci_datagram_dispatch(u32 context_id,
	struct vmci_datagram *dg, bool from_guest)
	{
	int retval;
	enum vmci_route route;

	BUILD_BUG_ON(sizeof(struct vmci_datagram) != 24);

	if (dg->payload_size > VMCI_MAX_DG_SIZE \|\|
	VMCI_DG_SIZE(dg) > VMCI_MAX_DG_SIZE) {
	pr_devel("Payload (size=%llu bytes) too big to send\n",
	(unsigned long long)dg->payload_size);
	return VMCI_ERROR_INVALID_ARGS;
	}

	retval = vmci_route(&dg->src, &dg->dst, from_guest, &route);
	if (retval < VMCI_SUCCESS) {
	pr_devel("Failed to route datagram (src=0x%x, dst=0x%x, err=%d)\n",
	dg->src.context, dg->dst.context, retval);
	return retval;
	}

	if (VMCI_ROUTE_AS_HOST == route) {
	if (VMCI_INVALID_ID == context_id)
	context_id = VMCI_HOST_CONTEXT_ID;
	return dg_dispatch_as_host(context_id, dg);
	}

	if (VMCI_ROUTE_AS_GUEST == route)
	return dg_dispatch_as_guest(dg);

	pr_warn("Unknown route (%d) for datagram\n", route);
	return VMCI_ERROR_DST_UNREACHABLE;
	}

	/*
	* Invoke the handler for the given datagram. This is intended to be
	* called only when acting as a guest and receiving a datagram from the
	* virtual device.
	*/
	int vmci_datagram_invoke_guest_handler(struct vmci_datagram *dg)
	{
	struct vmci_resource *resource;
	struct datagram_entry *dst_entry;

	resource = vmci_resource_by_handle(dg->dst,
	VMCI_RESOURCE_TYPE_DATAGRAM);
	if (!resource) {
	pr_devel("destination (handle=0x%x:0x%x) doesn't exist\n",
	dg->dst.context, dg->dst.resource);
	return VMCI_ERROR_NO_HANDLE;
	}

	dst_entry = container_of(resource, struct datagram_entry, resource);
	if (dst_entry->run_delayed) {
	struct delayed_datagram_info *dg_info;

	dg_info = kmalloc(sizeof(*dg_info) + (size_t)dg->payload_size,
	GFP_ATOMIC);
	if (!dg_info) {
	vmci_resource_put(resource);
	return VMCI_ERROR_NO_MEM;
	}

	dg_info->in_dg_host_queue = false;
	dg_info->entry = dst_entry;
	memcpy(&dg_info->msg, dg, VMCI_DG_SIZE(dg));

	INIT_WORK(&dg_info->work, dg_delayed_dispatch);
	schedule_work(&dg_info->work);
	} else {
	dst_entry->recv_cb(dst_entry->client_data, dg);
	vmci_resource_put(resource);
	}

	return VMCI_SUCCESS;
	}

	/*
	* vmci_datagram_create_handle_priv() - Create host context datagram endpoint
	* @resource_id: The resource ID.
	* @flags: Datagram Flags.
	* @priv_flags: Privilege Flags.
	* @recv_cb: Callback when receiving datagrams.
	* @client_data: Pointer for a datagram_entry struct
	* @out_handle: vmci_handle that is populated as a result of this function.
	*
	* Creates a host context datagram endpoint and returns a handle to it.
	*/
	int vmci_datagram_create_handle_priv(u32 resource_id,
	u32 flags,
	u32 priv_flags,
	vmci_datagram_recv_cb recv_cb,
	void *client_data,
	struct vmci_handle *out_handle)
	{
	if (out_handle == NULL)
	return VMCI_ERROR_INVALID_ARGS;

	if (recv_cb == NULL) {
	pr_devel("Client callback needed when creating datagram\n");
	return VMCI_ERROR_INVALID_ARGS;
	}

	if (priv_flags & ~VMCI_PRIVILEGE_ALL_FLAGS)
	return VMCI_ERROR_INVALID_ARGS;

	return dg_create_handle(resource_id, flags, priv_flags, recv_cb,
	client_data, out_handle);
	}
	EXPORT_SYMBOL_GPL(vmci_datagram_create_handle_priv);

	/*
	* vmci_datagram_create_handle() - Create host context datagram endpoint
	* @resource_id: Resource ID.
	* @flags: Datagram Flags.
	* @recv_cb: Callback when receiving datagrams.
	* @client_ata: Pointer for a datagram_entry struct
	* @out_handle: vmci_handle that is populated as a result of this function.
	*
	* Creates a host context datagram endpoint and returns a handle to
	* it. Same as vmci_datagram_create_handle_priv without the priviledge
	* flags argument.
	*/
	int vmci_datagram_create_handle(u32 resource_id,
	u32 flags,
	vmci_datagram_recv_cb recv_cb,
	void *client_data,
	struct vmci_handle *out_handle)
	{
	return vmci_datagram_create_handle_priv(
	resource_id, flags,
	VMCI_DEFAULT_PROC_PRIVILEGE_FLAGS,
	recv_cb, client_data,
	out_handle);
	}
	EXPORT_SYMBOL_GPL(vmci_datagram_create_handle);

	/*
	* vmci_datagram_destroy_handle() - Destroys datagram handle
	* @handle: vmci_handle to be destroyed and reaped.
	*
	* Use this function to destroy any datagram handles created by
	* vmci_datagram_create_handle{,Priv} functions.
	*/
	int vmci_datagram_destroy_handle(struct vmci_handle handle)
	{
	struct datagram_entry *entry;
	struct vmci_resource *resource;

	resource = vmci_resource_by_handle(handle, VMCI_RESOURCE_TYPE_DATAGRAM);
	if (!resource) {
	pr_devel("Failed to destroy datagram (handle=0x%x:0x%x)\n",
	handle.context, handle.resource);
	return VMCI_ERROR_NOT_FOUND;
	}

	entry = container_of(resource, struct datagram_entry, resource);

	vmci_resource_put(&entry->resource);
	vmci_resource_remove(&entry->resource);
	kfree(entry);

	return VMCI_SUCCESS;
	}
	EXPORT_SYMBOL_GPL(vmci_datagram_destroy_handle);

	/*
	* vmci_datagram_send() - Send a datagram
	* @msg: The datagram to send.
	*
	* Sends the provided datagram on its merry way.
	*/
	int vmci_datagram_send(struct vmci_datagram *msg)
	{
	if (msg == NULL)
	return VMCI_ERROR_INVALID_ARGS;

	return vmci_datagram_dispatch(VMCI_INVALID_ID, msg, false);
	}
	EXPORT_SYMBOL_GPL(vmci_datagram_send);