VMCI: queue pairs implementation.

VMCI queue pairs allow for bi-directional ordered communication between host and guests.

Signed-off-by: George Zhang <georgezhang@vmware.com>
Acked-by: Andy king <acking@vmware.com>
Acked-by: Dmitry Torokhov <dtor@vmware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

2 files changed, 3611 insertions, 0 deletions

diff --git a/drivers/misc/vmw_vmci/vmci_queue_pair.c b/drivers/misc/vmw_vmci/vmci_queue_pair.c
new file mode 100644
index 0000000..1123111b
--- /dev/null
+++ b/drivers/misc/vmw_vmci/vmci_queue_pair.c
@@ -0,0 +1,3420 @@
+/*
+ * 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/device-mapper.h>
+#include <linux/vmw_vmci_defs.h>
+#include <linux/vmw_vmci_api.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/socket.h>
+#include <linux/wait.h>
+
+#include "vmci_handle_array.h"
+#include "vmci_queue_pair.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"
+
+/*
+ * In the following, we will distinguish between two kinds of VMX processes -
+ * the ones with versions lower than VMCI_VERSION_NOVMVM that use specialized
+ * VMCI page files in the VMX and supporting VM to VM communication and the
+ * newer ones that use the guest memory directly. We will in the following
+ * refer to the older VMX versions as old-style VMX'en, and the newer ones as
+ * new-style VMX'en.
+ *
+ * The state transition datagram is as follows (the VMCIQPB_ prefix has been
+ * removed for readability) - see below for more details on the transtions:
+ *
+ *            --------------  NEW  -------------
+ *            |                                |
+ *           \_/                              \_/
+ *     CREATED_NO_MEM <-----------------> CREATED_MEM
+ *            |    |                           |
+ *            |    o-----------------------o   |
+ *            |                            |   |
+ *           \_/                          \_/ \_/
+ *     ATTACHED_NO_MEM <----------------> ATTACHED_MEM
+ *            |                            |   |
+ *            |     o----------------------o   |
+ *            |     |                          |
+ *           \_/   \_/                        \_/
+ *     SHUTDOWN_NO_MEM <----------------> SHUTDOWN_MEM
+ *            |                                |
+ *            |                                |
+ *            -------------> gone <-------------
+ *
+ * In more detail. When a VMCI queue pair is first created, it will be in the
+ * VMCIQPB_NEW state. It will then move into one of the following states:
+ *
+ * - VMCIQPB_CREATED_NO_MEM: this state indicates that either:
+ *
+ *     - the created was performed by a host endpoint, in which case there is
+ *       no backing memory yet.
+ *
+ *     - the create was initiated by an old-style VMX, that uses
+ *       vmci_qp_broker_set_page_store to specify the UVAs of the queue pair at
+ *       a later point in time. This state can be distinguished from the one
+ *       above by the context ID of the creator. A host side is not allowed to
+ *       attach until the page store has been set.
+ *
+ * - VMCIQPB_CREATED_MEM: this state is the result when the queue pair
+ *     is created by a VMX using the queue pair device backend that
+ *     sets the UVAs of the queue pair immediately and stores the
+ *     information for later attachers. At this point, it is ready for
+ *     the host side to attach to it.
+ *
+ * Once the queue pair is in one of the created states (with the exception of
+ * the case mentioned for older VMX'en above), it is possible to attach to the
+ * queue pair. Again we have two new states possible:
+ *
+ * - VMCIQPB_ATTACHED_MEM: this state can be reached through the following
+ *   paths:
+ *
+ *     - from VMCIQPB_CREATED_NO_MEM when a new-style VMX allocates a queue
+ *       pair, and attaches to a queue pair previously created by the host side.
+ *
+ *     - from VMCIQPB_CREATED_MEM when the host side attaches to a queue pair
+ *       already created by a guest.
+ *
+ *     - from VMCIQPB_ATTACHED_NO_MEM, when an old-style VMX calls
+ *       vmci_qp_broker_set_page_store (see below).
+ *
+ * - VMCIQPB_ATTACHED_NO_MEM: If the queue pair already was in the
+ *     VMCIQPB_CREATED_NO_MEM due to a host side create, an old-style VMX will
+ *     bring the queue pair into this state. Once vmci_qp_broker_set_page_store
+ *     is called to register the user memory, the VMCIQPB_ATTACH_MEM state
+ *     will be entered.
+ *
+ * From the attached queue pair, the queue pair can enter the shutdown states
+ * when either side of the queue pair detaches. If the guest side detaches
+ * first, the queue pair will enter the VMCIQPB_SHUTDOWN_NO_MEM state, where
+ * the content of the queue pair will no longer be available. If the host
+ * side detaches first, the queue pair will either enter the
+ * VMCIQPB_SHUTDOWN_MEM, if the guest memory is currently mapped, or
+ * VMCIQPB_SHUTDOWN_NO_MEM, if the guest memory is not mapped
+ * (e.g., the host detaches while a guest is stunned).
+ *
+ * New-style VMX'en will also unmap guest memory, if the guest is
+ * quiesced, e.g., during a snapshot operation. In that case, the guest
+ * memory will no longer be available, and the queue pair will transition from
+ * *_MEM state to a *_NO_MEM state. The VMX may later map the memory once more,
+ * in which case the queue pair will transition from the *_NO_MEM state at that
+ * point back to the *_MEM state. Note that the *_NO_MEM state may have changed,
+ * since the peer may have either attached or detached in the meantime. The
+ * values are laid out such that ++ on a state will move from a *_NO_MEM to a
+ * *_MEM state, and vice versa.
+ */
+
+/*
+ * VMCIMemcpy{To,From}QueueFunc() prototypes.  Functions of these
+ * types are passed around to enqueue and dequeue routines.  Note that
+ * often the functions passed are simply wrappers around memcpy
+ * itself.
+ *
+ * Note: In order for the memcpy typedefs to be compatible with the VMKernel,
+ * there's an unused last parameter for the hosted side.  In
+ * ESX, that parameter holds a buffer type.
+ */
+typedef int vmci_memcpy_to_queue_func(struct vmci_queue *queue,
+				      u64 queue_offset, const void *src,
+				      size_t src_offset, size_t size);
+typedef int vmci_memcpy_from_queue_func(void *dest, size_t dest_offset,
+					const struct vmci_queue *queue,
+					u64 queue_offset, size_t size);
+
+/* The Kernel specific component of the struct vmci_queue structure. */
+struct vmci_queue_kern_if {
+	struct page **page;
+	struct page **header_page;
+	void *va;
+	struct mutex __mutex;	/* Protects the queue. */
+	struct mutex *mutex;	/* Shared by producer and consumer queues. */
+	bool host;
+	size_t num_pages;
+	bool mapped;
+};
+
+/*
+ * This structure is opaque to the clients.
+ */
+struct vmci_qp {
+	struct vmci_handle handle;
+	struct vmci_queue *produce_q;
+	struct vmci_queue *consume_q;
+	u64 produce_q_size;
+	u64 consume_q_size;
+	u32 peer;
+	u32 flags;
+	u32 priv_flags;
+	bool guest_endpoint;
+	unsigned int blocked;
+	unsigned int generation;
+	wait_queue_head_t event;
+};
+
+enum qp_broker_state {
+	VMCIQPB_NEW,
+	VMCIQPB_CREATED_NO_MEM,
+	VMCIQPB_CREATED_MEM,
+	VMCIQPB_ATTACHED_NO_MEM,
+	VMCIQPB_ATTACHED_MEM,
+	VMCIQPB_SHUTDOWN_NO_MEM,
+	VMCIQPB_SHUTDOWN_MEM,
+	VMCIQPB_GONE
+};
+
+#define QPBROKERSTATE_HAS_MEM(_qpb) (_qpb->state == VMCIQPB_CREATED_MEM || \
+				     _qpb->state == VMCIQPB_ATTACHED_MEM || \
+				     _qpb->state == VMCIQPB_SHUTDOWN_MEM)
+
+/*
+ * In the queue pair broker, we always use the guest point of view for
+ * the produce and consume queue values and references, e.g., the
+ * produce queue size stored is the guests produce queue size. The
+ * host endpoint will need to swap these around. The only exception is
+ * the local queue pairs on the host, in which case the host endpoint
+ * that creates the queue pair will have the right orientation, and
+ * the attaching host endpoint will need to swap.
+ */
+struct qp_entry {
+	struct list_head list_item;
+	struct vmci_handle handle;
+	u32 peer;
+	u32 flags;
+	u64 produce_size;
+	u64 consume_size;
+	u32 ref_count;
+};
+
+struct qp_broker_entry {
+	struct vmci_resource resource;
+	struct qp_entry qp;
+	u32 create_id;
+	u32 attach_id;
+	enum qp_broker_state state;
+	bool require_trusted_attach;
+	bool created_by_trusted;
+	bool vmci_page_files;	/* Created by VMX using VMCI page files */
+	struct vmci_queue *produce_q;
+	struct vmci_queue *consume_q;
+	struct vmci_queue_header saved_produce_q;
+	struct vmci_queue_header saved_consume_q;
+	vmci_event_release_cb wakeup_cb;
+	void *client_data;
+	void *local_mem;	/* Kernel memory for local queue pair */
+};
+
+struct qp_guest_endpoint {
+	struct vmci_resource resource;
+	struct qp_entry qp;
+	u64 num_ppns;
+	void *produce_q;
+	void *consume_q;
+	struct PPNSet ppn_set;
+};
+
+struct qp_list {
+	struct list_head head;
+	struct mutex mutex;	/* Protect queue list. */
+};
+
+static struct qp_list qp_broker_list = {
+	.head = LIST_HEAD_INIT(qp_broker_list.head),
+	.mutex = __MUTEX_INITIALIZER(qp_broker_list.mutex),
+};
+
+static struct qp_list qp_guest_endpoints = {
+	.head = LIST_HEAD_INIT(qp_guest_endpoints.head),
+	.mutex = __MUTEX_INITIALIZER(qp_guest_endpoints.mutex),
+};
+
+#define INVALID_VMCI_GUEST_MEM_ID  0
+#define QPE_NUM_PAGES(_QPE) ((u32)					 \
+			     (dm_div_up(_QPE.produce_size, PAGE_SIZE) +	 \
+			      dm_div_up(_QPE.consume_size, PAGE_SIZE) + 2))
+
+
+/*
+ * Frees kernel VA space for a given queue and its queue header, and
+ * frees physical data pages.
+ */
+static void qp_free_queue(void *q, u64 size)
+{
+	struct vmci_queue *queue = q;
+
+	if (queue) {
+		u64 i = dm_div_up(size, PAGE_SIZE);
+
+		if (queue->kernel_if->mapped) {
+			vunmap(queue->kernel_if->va);
+			queue->kernel_if->va = NULL;
+		}
+
+		while (i)
+			__free_page(queue->kernel_if->page[--i]);
+
+		vfree(queue->q_header);
+	}
+}
+
+/*
+ * Allocates kernel VA space of specified size, plus space for the
+ * queue structure/kernel interface and the queue header.  Allocates
+ * physical pages for the queue data pages.
+ *
+ * PAGE m:      struct vmci_queue_header (struct vmci_queue->q_header)
+ * PAGE m+1:    struct vmci_queue
+ * PAGE m+1+q:  struct vmci_queue_kern_if (struct vmci_queue->kernel_if)
+ * PAGE n-size: Data pages (struct vmci_queue->kernel_if->page[])
+ */
+static void *qp_alloc_queue(u64 size, u32 flags)
+{
+	u64 i;
+	struct vmci_queue *queue;
+	struct vmci_queue_header *q_header;
+	const u64 num_data_pages = dm_div_up(size, PAGE_SIZE);
+	const uint queue_size =
+	    PAGE_SIZE +
+	    sizeof(*queue) + sizeof(*(queue->kernel_if)) +
+	    num_data_pages * sizeof(*(queue->kernel_if->page));
+
+	q_header = vmalloc(queue_size);
+	if (!q_header)
+		return NULL;
+
+	queue = (void *)q_header + PAGE_SIZE;
+	queue->q_header = q_header;
+	queue->saved_header = NULL;
+	queue->kernel_if = (struct vmci_queue_kern_if *)(queue + 1);
+	queue->kernel_if->header_page = NULL;	/* Unused in guest. */
+	queue->kernel_if->page = (struct page **)(queue->kernel_if + 1);
+	queue->kernel_if->host = false;
+	queue->kernel_if->va = NULL;
+	queue->kernel_if->mapped = false;
+
+	for (i = 0; i < num_data_pages; i++) {
+		queue->kernel_if->page[i] = alloc_pages(GFP_KERNEL, 0);
+		if (!queue->kernel_if->page[i])
+			goto fail;
+	}
+
+	if (vmci_qp_pinned(flags)) {
+		queue->kernel_if->va =
+		    vmap(queue->kernel_if->page, num_data_pages, VM_MAP,
+			 PAGE_KERNEL);
+		if (!queue->kernel_if->va)
+			goto fail;
+
+		queue->kernel_if->mapped = true;
+	}
+
+	return (void *)queue;
+
+ fail:
+	qp_free_queue(queue, i * PAGE_SIZE);
+	return NULL;
+}
+
+/*
+ * Copies from a given buffer or iovector to a VMCI Queue.  Uses
+ * kmap()/kunmap() to dynamically map/unmap required portions of the queue
+ * by traversing the offset -> page translation structure for the queue.
+ * Assumes that offset + size does not wrap around in the queue.
+ */
+static int __qp_memcpy_to_queue(struct vmci_queue *queue,
+				u64 queue_offset,
+				const void *src,
+				size_t size,
+				bool is_iovec)
+{
+	struct vmci_queue_kern_if *kernel_if = queue->kernel_if;
+	size_t bytes_copied = 0;
+
+	while (bytes_copied < size) {
+		u64 page_index = (queue_offset + bytes_copied) / PAGE_SIZE;
+		size_t page_offset =
+		    (queue_offset + bytes_copied) & (PAGE_SIZE - 1);
+		void *va;
+		size_t to_copy;
+
+		if (!kernel_if->mapped)
+			va = kmap(kernel_if->page[page_index]);
+		else
+			va = (void *)((u8 *)kernel_if->va +
+				      (page_index * PAGE_SIZE));
+
+		if (size - bytes_copied > PAGE_SIZE - page_offset)
+			/* Enough payload to fill up from this page. */
+			to_copy = PAGE_SIZE - page_offset;
+		else
+			to_copy = size - bytes_copied;
+
+		if (is_iovec) {
+			struct iovec *iov = (struct iovec *)src;
+			int err;
+
+			/* The iovec will track bytes_copied internally. */
+			err = memcpy_fromiovec((u8 *)va + page_offset,
+					       iov, to_copy);
+			if (err != 0) {
+				kunmap(kernel_if->page[page_index]);
+				return VMCI_ERROR_INVALID_ARGS;
+			}
+		} else {
+			memcpy((u8 *)va + page_offset,
+			       (u8 *)src + bytes_copied, to_copy);
+		}
+
+		bytes_copied += to_copy;
+		if (!kernel_if->mapped)
+			kunmap(kernel_if->page[page_index]);
+	}
+
+	return VMCI_SUCCESS;
+}
+
+/*
+ * Copies to a given buffer or iovector from a VMCI Queue.  Uses
+ * kmap()/kunmap() to dynamically map/unmap required portions of the queue
+ * by traversing the offset -> page translation structure for the queue.
+ * Assumes that offset + size does not wrap around in the queue.
+ */
+static int __qp_memcpy_from_queue(void *dest,
+				  const struct vmci_queue *queue,
+				  u64 queue_offset,
+				  size_t size,
+				  bool is_iovec)
+{
+	struct vmci_queue_kern_if *kernel_if = queue->kernel_if;
+	size_t bytes_copied = 0;
+
+	while (bytes_copied < size) {
+		u64 page_index = (queue_offset + bytes_copied) / PAGE_SIZE;
+		size_t page_offset =
+		    (queue_offset + bytes_copied) & (PAGE_SIZE - 1);
+		void *va;
+		size_t to_copy;
+
+		if (!kernel_if->mapped)
+			va = kmap(kernel_if->page[page_index]);
+		else
+			va = (void *)((u8 *)kernel_if->va +
+				      (page_index * PAGE_SIZE));
+
+		if (size - bytes_copied > PAGE_SIZE - page_offset)
+			/* Enough payload to fill up this page. */
+			to_copy = PAGE_SIZE - page_offset;
+		else
+			to_copy = size - bytes_copied;
+
+		if (is_iovec) {
+			struct iovec *iov = (struct iovec *)dest;
+			int err;
+
+			/* The iovec will track bytes_copied internally. */
+			err = memcpy_toiovec(iov, (u8 *)va + page_offset,
+					     to_copy);
+			if (err != 0) {
+				kunmap(kernel_if->page[page_index]);
+				return VMCI_ERROR_INVALID_ARGS;
+			}
+		} else {
+			memcpy((u8 *)dest + bytes_copied,
+			       (u8 *)va + page_offset, to_copy);
+		}
+
+		bytes_copied += to_copy;
+		if (!kernel_if->mapped)
+			kunmap(kernel_if->page[page_index]);
+	}
+
+	return VMCI_SUCCESS;
+}
+
+/*
+ * Allocates two list of PPNs --- one for the pages in the produce queue,
+ * and the other for the pages in the consume queue. Intializes the list
+ * of PPNs with the page frame numbers of the KVA for the two queues (and
+ * the queue headers).
+ */
+static int qp_alloc_ppn_set(void *prod_q,
+			    u64 num_produce_pages,
+			    void *cons_q,
+			    u64 num_consume_pages, struct PPNSet *ppn_set)
+{
+	u32 *produce_ppns;
+	u32 *consume_ppns;
+	struct vmci_queue *produce_q = prod_q;
+	struct vmci_queue *consume_q = cons_q;
+	u64 i;
+
+	if (!produce_q || !num_produce_pages || !consume_q ||
+	    !num_consume_pages || !ppn_set)
+		return VMCI_ERROR_INVALID_ARGS;
+
+	if (ppn_set->initialized)
+		return VMCI_ERROR_ALREADY_EXISTS;
+
+	produce_ppns =
+	    kmalloc(num_produce_pages * sizeof(*produce_ppns), GFP_KERNEL);
+	if (!produce_ppns)
+		return VMCI_ERROR_NO_MEM;
+
+	consume_ppns =
+	    kmalloc(num_consume_pages * sizeof(*consume_ppns), GFP_KERNEL);
+	if (!consume_ppns) {
+		kfree(produce_ppns);
+		return VMCI_ERROR_NO_MEM;
+	}
+
+	produce_ppns[0] = page_to_pfn(vmalloc_to_page(produce_q->q_header));
+	for (i = 1; i < num_produce_pages; i++) {
+		unsigned long pfn;
+
+		produce_ppns[i] =
+		    page_to_pfn(produce_q->kernel_if->page[i - 1]);
+		pfn = produce_ppns[i];
+
+		/* Fail allocation if PFN isn't supported by hypervisor. */
+		if (sizeof(pfn) > sizeof(*produce_ppns)
+		    && pfn != produce_ppns[i])
+			goto ppn_error;
+	}
+
+	consume_ppns[0] = page_to_pfn(vmalloc_to_page(consume_q->q_header));
+	for (i = 1; i < num_consume_pages; i++) {
+		unsigned long pfn;
+
+		consume_ppns[i] =
+		    page_to_pfn(consume_q->kernel_if->page[i - 1]);
+		pfn = consume_ppns[i];
+
+		/* Fail allocation if PFN isn't supported by hypervisor. */
+		if (sizeof(pfn) > sizeof(*consume_ppns)
+		    && pfn != consume_ppns[i])
+			goto ppn_error;
+	}
+
+	ppn_set->num_produce_pages = num_produce_pages;
+	ppn_set->num_consume_pages = num_consume_pages;
+	ppn_set->produce_ppns = produce_ppns;
+	ppn_set->consume_ppns = consume_ppns;
+	ppn_set->initialized = true;
+	return VMCI_SUCCESS;
+
+ ppn_error:
+	kfree(produce_ppns);
+	kfree(consume_ppns);
+	return VMCI_ERROR_INVALID_ARGS;
+}
+
+/*
+ * Frees the two list of PPNs for a queue pair.
+ */
+static void qp_free_ppn_set(struct PPNSet *ppn_set)
+{
+	if (ppn_set->initialized) {
+		/* Do not call these functions on NULL inputs. */
+		kfree(ppn_set->produce_ppns);
+		kfree(ppn_set->consume_ppns);
+	}
+	memset(ppn_set, 0, sizeof(*ppn_set));
+}
+
+/*
+ * Populates the list of PPNs in the hypercall structure with the PPNS
+ * of the produce queue and the consume queue.
+ */
+static int qp_populate_ppn_set(u8 *call_buf, const struct PPNSet *ppn_set)
+{
+	memcpy(call_buf, ppn_set->produce_ppns,
+	       ppn_set->num_produce_pages * sizeof(*ppn_set->produce_ppns));
+	memcpy(call_buf +
+	       ppn_set->num_produce_pages * sizeof(*ppn_set->produce_ppns),
+	       ppn_set->consume_ppns,
+	       ppn_set->num_consume_pages * sizeof(*ppn_set->consume_ppns));
+
+	return VMCI_SUCCESS;
+}
+
+static int qp_memcpy_to_queue(struct vmci_queue *queue,
+			      u64 queue_offset,
+			      const void *src, size_t src_offset, size_t size)
+{
+	return __qp_memcpy_to_queue(queue, queue_offset,
+				    (u8 *)src + src_offset, size, false);
+}
+
+static int qp_memcpy_from_queue(void *dest,
+				size_t dest_offset,
+				const struct vmci_queue *queue,
+				u64 queue_offset, size_t size)
+{
+	return __qp_memcpy_from_queue((u8 *)dest + dest_offset,
+				      queue, queue_offset, size, false);
+}
+
+/*
+ * Copies from a given iovec from a VMCI Queue.
+ */
+static int qp_memcpy_to_queue_iov(struct vmci_queue *queue,
+				  u64 queue_offset,
+				  const void *src,
+				  size_t src_offset, size_t size)
+{
+
+	/*
+	 * We ignore src_offset because src is really a struct iovec * and will
+	 * maintain offset internally.
+	 */
+	return __qp_memcpy_to_queue(queue, queue_offset, src, size, true);
+}
+
+/*
+ * Copies to a given iovec from a VMCI Queue.
+ */
+static int qp_memcpy_from_queue_iov(void *dest,
+				    size_t dest_offset,
+				    const struct vmci_queue *queue,
+				    u64 queue_offset, size_t size)
+{
+	/*
+	 * We ignore dest_offset because dest is really a struct iovec * and
+	 * will maintain offset internally.
+	 */
+	return __qp_memcpy_from_queue(dest, queue, queue_offset, size, true);
+}
+
+/*
+ * Allocates kernel VA space of specified size plus space for the queue
+ * and kernel interface.  This is different from the guest queue allocator,
+ * because we do not allocate our own queue header/data pages here but
+ * share those of the guest.
+ */
+static struct vmci_queue *qp_host_alloc_queue(u64 size)
+{
+	struct vmci_queue *queue;
+	const size_t num_pages = dm_div_up(size, PAGE_SIZE) + 1;
+	const size_t queue_size = sizeof(*queue) + sizeof(*(queue->kernel_if));
+	const size_t queue_page_size =
+	    num_pages * sizeof(*queue->kernel_if->page);
+
+	queue = kzalloc(queue_size + queue_page_size, GFP_KERNEL);
+	if (queue) {
+		queue->q_header = NULL;
+		queue->saved_header = NULL;
+		queue->kernel_if =
+		    (struct vmci_queue_kern_if *)((u8 *)queue +
+						  sizeof(*queue));
+		queue->kernel_if->host = true;
+		queue->kernel_if->mutex = NULL;
+		queue->kernel_if->num_pages = num_pages;
+		queue->kernel_if->header_page =
+		    (struct page **)((u8 *)queue + queue_size);
+		queue->kernel_if->page = &queue->kernel_if->header_page[1];
+		queue->kernel_if->va = NULL;
+		queue->kernel_if->mapped = false;
+	}
+
+	return queue;
+}
+
+/*
+ * Frees kernel memory for a given queue (header plus translation
+ * structure).
+ */
+static void qp_host_free_queue(struct vmci_queue *queue, u64 queue_size)
+{
+	kfree(queue);
+}
+
+/*
+ * Initialize the mutex for the pair of queues.  This mutex is used to
+ * protect the q_header and the buffer from changing out from under any
+ * users of either queue.  Of course, it's only any good if the mutexes
+ * are actually acquired.  Queue structure must lie on non-paged memory
+ * or we cannot guarantee access to the mutex.
+ */
+static void qp_init_queue_mutex(struct vmci_queue *produce_q,
+				struct vmci_queue *consume_q)
+{
+	/*
+	 * Only the host queue has shared state - the guest queues do not
+	 * need to synchronize access using a queue mutex.
+	 */
+
+	if (produce_q->kernel_if->host) {
+		produce_q->kernel_if->mutex = &produce_q->kernel_if->__mutex;
+		consume_q->kernel_if->mutex = &produce_q->kernel_if->__mutex;
+		mutex_init(produce_q->kernel_if->mutex);
+	}
+}
+
+/*
+ * Cleans up the mutex for the pair of queues.
+ */
+static void qp_cleanup_queue_mutex(struct vmci_queue *produce_q,
+				   struct vmci_queue *consume_q)
+{
+	if (produce_q->kernel_if->host) {
+		produce_q->kernel_if->mutex = NULL;
+		consume_q->kernel_if->mutex = NULL;
+	}
+}
+
+/*
+ * Acquire the mutex for the queue.  Note that the produce_q and
+ * the consume_q share a mutex.  So, only one of the two need to
+ * be passed in to this routine.  Either will work just fine.
+ */
+static void qp_acquire_queue_mutex(struct vmci_queue *queue)
+{
+	if (queue->kernel_if->host)
+		mutex_lock(queue->kernel_if->mutex);
+}
+
+/*
+ * Release the mutex for the queue.  Note that the produce_q and
+ * the consume_q share a mutex.  So, only one of the two need to
+ * be passed in to this routine.  Either will work just fine.
+ */
+static void qp_release_queue_mutex(struct vmci_queue *queue)
+{
+	if (queue->kernel_if->host)
+		mutex_unlock(queue->kernel_if->mutex);
+}
+
+/*
+ * Helper function to release pages in the PageStoreAttachInfo
+ * previously obtained using get_user_pages.
+ */
+static void qp_release_pages(struct page **pages,
+			     u64 num_pages, bool dirty)
+{
+	int i;
+
+	for (i = 0; i < num_pages; i++) {
+		if (dirty)
+			set_page_dirty(pages[i]);
+
+		page_cache_release(pages[i]);
+		pages[i] = NULL;
+	}
+}
+
+/*
+ * Lock the user pages referenced by the {produce,consume}Buffer
+ * struct into memory and populate the {produce,consume}Pages
+ * arrays in the attach structure with them.
+ */
+static int qp_host_get_user_memory(u64 produce_uva,
+				   u64 consume_uva,
+				   struct vmci_queue *produce_q,
+				   struct vmci_queue *consume_q)
+{
+	int retval;
+	int err = VMCI_SUCCESS;
+
+	down_write(&current->mm->mmap_sem);
+	retval = get_user_pages(current,
+				current->mm,
+				(uintptr_t) produce_uva,
+				produce_q->kernel_if->num_pages,
+				1, 0, produce_q->kernel_if->header_page, NULL);
+	if (retval < produce_q->kernel_if->num_pages) {
+		pr_warn("get_user_pages(produce) failed (retval=%d)", retval);
+		qp_release_pages(produce_q->kernel_if->header_page, retval,
+				 false);
+		err = VMCI_ERROR_NO_MEM;
+		goto out;
+	}
+
+	retval = get_user_pages(current,
+				current->mm,
+				(uintptr_t) consume_uva,
+				consume_q->kernel_if->num_pages,
+				1, 0, consume_q->kernel_if->header_page, NULL);
+	if (retval < consume_q->kernel_if->num_pages) {
+		pr_warn("get_user_pages(consume) failed (retval=%d)", retval);
+		qp_release_pages(consume_q->kernel_if->header_page, retval,
+				 false);
+		qp_release_pages(produce_q->kernel_if->header_page,
+				 produce_q->kernel_if->num_pages, false);
+		err = VMCI_ERROR_NO_MEM;
+	}
+
+ out:
+	up_write(&current->mm->mmap_sem);
+
+	return err;
+}
+
+/*
+ * Registers the specification of the user pages used for backing a queue
+ * pair. Enough information to map in pages is stored in the OS specific
+ * part of the struct vmci_queue structure.
+ */
+static int qp_host_register_user_memory(struct vmci_qp_page_store *page_store,
+					struct vmci_queue *produce_q,
+					struct vmci_queue *consume_q)
+{
+	u64 produce_uva;
+	u64 consume_uva;
+
+	/*
+	 * The new style and the old style mapping only differs in
+	 * that we either get a single or two UVAs, so we split the
+	 * single UVA range at the appropriate spot.
+	 */
+	produce_uva = page_store->pages;
+	consume_uva = page_store->pages +
+	    produce_q->kernel_if->num_pages * PAGE_SIZE;
+	return qp_host_get_user_memory(produce_uva, consume_uva, produce_q,
+				       consume_q);
+}
+
+/*
+ * Releases and removes the references to user pages stored in the attach
+ * struct.  Pages are released from the page cache and may become
+ * swappable again.
+ */
+static void qp_host_unregister_user_memory(struct vmci_queue *produce_q,
+					   struct vmci_queue *consume_q)
+{
+	qp_release_pages(produce_q->kernel_if->header_page,
+			 produce_q->kernel_if->num_pages, true);
+	memset(produce_q->kernel_if->header_page, 0,
+	       sizeof(*produce_q->kernel_if->header_page) *
+	       produce_q->kernel_if->num_pages);
+	qp_release_pages(consume_q->kernel_if->header_page,
+			 consume_q->kernel_if->num_pages, true);
+	memset(consume_q->kernel_if->header_page, 0,
+	       sizeof(*consume_q->kernel_if->header_page) *
+	       consume_q->kernel_if->num_pages);
+}
+
+/*
+ * Once qp_host_register_user_memory has been performed on a
+ * queue, the queue pair headers can be mapped into the
+ * kernel. Once mapped, they must be unmapped with
+ * qp_host_unmap_queues prior to calling
+ * qp_host_unregister_user_memory.
+ * Pages are pinned.
+ */
+static int qp_host_map_queues(struct vmci_queue *produce_q,
+			      struct vmci_queue *consume_q)
+{
+	int result;
+
+	if (!produce_q->q_header || !consume_q->q_header) {
+		struct page *headers[2];
+
+		if (produce_q->q_header != consume_q->q_header)
+			return VMCI_ERROR_QUEUEPAIR_MISMATCH;
+
+		if (produce_q->kernel_if->header_page == NULL ||
+		    *produce_q->kernel_if->header_page == NULL)
+			return VMCI_ERROR_UNAVAILABLE;
+
+		headers[0] = *produce_q->kernel_if->header_page;
+		headers[1] = *consume_q->kernel_if->header_page;
+
+		produce_q->q_header = vmap(headers, 2, VM_MAP, PAGE_KERNEL);
+		if (produce_q->q_header != NULL) {
+			consume_q->q_header =
+			    (struct vmci_queue_header *)((u8 *)
+							 produce_q->q_header +
+							 PAGE_SIZE);
+			result = VMCI_SUCCESS;
+		} else {
+			pr_warn("vmap failed\n");
+			result = VMCI_ERROR_NO_MEM;
+		}
+	} else {
+		result = VMCI_SUCCESS;
+	}
+
+	return result;
+}
+
+/*
+ * Unmaps previously mapped queue pair headers from the kernel.
+ * Pages are unpinned.
+ */
+static int qp_host_unmap_queues(u32 gid,
+				struct vmci_queue *produce_q,
+				struct vmci_queue *consume_q)
+{
+	if (produce_q->q_header) {
+		if (produce_q->q_header < consume_q->q_header)
+			vunmap(produce_q->q_header);
+		else
+			vunmap(consume_q->q_header);
+
+		produce_q->q_header = NULL;
+		consume_q->q_header = NULL;
+	}
+
+	return VMCI_SUCCESS;
+}
+
+/*
+ * Finds the entry in the list corresponding to a given handle. Assumes
+ * that the list is locked.
+ */
+static struct qp_entry *qp_list_find(struct qp_list *qp_list,
+				     struct vmci_handle handle)
+{
+	struct qp_entry *entry;
+
+	if (vmci_handle_is_invalid(handle))
+		return NULL;
+
+	list_for_each_entry(entry, &qp_list->head, list_item) {
+		if (vmci_handle_is_equal(entry->handle, handle))
+			return entry;
+	}
+
+	return NULL;
+}
+
+/*
+ * Finds the entry in the list corresponding to a given handle.
+ */
+static struct qp_guest_endpoint *
+qp_guest_handle_to_entry(struct vmci_handle handle)
+{
+	struct qp_guest_endpoint *entry;
+	struct qp_entry *qp = qp_list_find(&qp_guest_endpoints, handle);
+
+	entry = qp ? container_of(
+		qp, struct qp_guest_endpoint, qp) : NULL;
+	return entry;
+}
+
+/*
+ * Finds the entry in the list corresponding to a given handle.
+ */
+static struct qp_broker_entry *
+qp_broker_handle_to_entry(struct vmci_handle handle)
+{
+	struct qp_broker_entry *entry;
+	struct qp_entry *qp = qp_list_find(&qp_broker_list, handle);
+
+	entry = qp ? container_of(
+		qp, struct qp_broker_entry, qp) : NULL;
+	return entry;
+}
+
+/*
+ * Dispatches a queue pair event message directly into the local event
+ * queue.
+ */
+static int qp_notify_peer_local(bool attach, struct vmci_handle handle)
+{
+	u32 context_id = vmci_get_context_id();
+	struct vmci_event_qp ev;
+
+	ev.msg.hdr.dst = vmci_make_handle(context_id, VMCI_EVENT_HANDLER);
+	ev.msg.hdr.src = vmci_make_handle(VMCI_HYPERVISOR_CONTEXT_ID,
+					  VMCI_CONTEXT_RESOURCE_ID);
+	ev.msg.hdr.payload_size = sizeof(ev) - sizeof(ev.msg.hdr);
+	ev.msg.event_data.event =
+	    attach ? VMCI_EVENT_QP_PEER_ATTACH : VMCI_EVENT_QP_PEER_DETACH;
+	ev.payload.peer_id = context_id;
+	ev.payload.handle = handle;
+
+	return vmci_event_dispatch(&ev.msg.hdr);
+}
+
+/*
+ * Allocates and initializes a qp_guest_endpoint structure.
+ * Allocates a queue_pair rid (and handle) iff the given entry has
+ * an invalid handle.  0 through VMCI_RESERVED_RESOURCE_ID_MAX
+ * are reserved handles.  Assumes that the QP list mutex is held
+ * by the caller.
+ */
+static struct qp_guest_endpoint *
+qp_guest_endpoint_create(struct vmci_handle handle,
+			 u32 peer,
+			 u32 flags,
+			 u64 produce_size,
+			 u64 consume_size,
+			 void *produce_q,
+			 void *consume_q)
+{
+	int result;
+	struct qp_guest_endpoint *entry;
+	/* One page each for the queue headers. */
+	const u64 num_ppns = dm_div_up(produce_size, PAGE_SIZE) +
+	    dm_div_up(consume_size, PAGE_SIZE) + 2;
+
+	if (vmci_handle_is_invalid(handle)) {
+		u32 context_id = vmci_get_context_id();
+
+		handle = vmci_make_handle(context_id, VMCI_INVALID_ID);
+	}
+
+	entry = kzalloc(sizeof(*entry), GFP_KERNEL);
+	if (entry) {
+		entry->qp.peer = peer;
+		entry->qp.flags = flags;
+		entry->qp.produce_size = produce_size;
+		entry->qp.consume_size = consume_size;
+		entry->qp.ref_count = 0;
+		entry->num_ppns = num_ppns;
+		entry->produce_q = produce_q;
+		entry->consume_q = consume_q;
+		INIT_LIST_HEAD(&entry->qp.list_item);
+
+		/* Add resource obj */
+		result = vmci_resource_add(&entry->resource,
+					   VMCI_RESOURCE_TYPE_QPAIR_GUEST,
+					   handle);
+		entry->qp.handle = vmci_resource_handle(&entry->resource);
+		if ((result != VMCI_SUCCESS) ||
+		    qp_list_find(&qp_guest_endpoints, entry->qp.handle)) {
+			pr_warn("Failed to add new resource (handle=0x%x:0x%x), error: %d",
+				handle.context, handle.resource, result);
+			kfree(entry);
+			entry = NULL;
+		}
+	}
+	return entry;
+}
+
+/*
+ * Frees a qp_guest_endpoint structure.
+ */
+static void qp_guest_endpoint_destroy(struct qp_guest_endpoint *entry)
+{
+	qp_free_ppn_set(&entry->ppn_set);
+	qp_cleanup_queue_mutex(entry->produce_q, entry->consume_q);
+	qp_free_queue(entry->produce_q, entry->qp.produce_size);
+	qp_free_queue(entry->consume_q, entry->qp.consume_size);
+	/* Unlink from resource hash table and free callback */
+	vmci_resource_remove(&entry->resource);
+
+	kfree(entry);
+}
+
+/*
+ * Helper to make a queue_pairAlloc hypercall when the driver is
+ * supporting a guest device.
+ */
+static int qp_alloc_hypercall(const struct qp_guest_endpoint *entry)
+{
+	struct vmci_qp_alloc_msg *alloc_msg;
+	size_t msg_size;
+	int result;
+
+	if (!entry || entry->num_ppns <= 2)
+		return VMCI_ERROR_INVALID_ARGS;
+
+	msg_size = sizeof(*alloc_msg) +
+	    (size_t) entry->num_ppns * sizeof(u32);
+	alloc_msg = kmalloc(msg_size, GFP_KERNEL);
+	if (!alloc_msg)
+		return VMCI_ERROR_NO_MEM;
+
+	alloc_msg->hdr.dst = vmci_make_handle(VMCI_HYPERVISOR_CONTEXT_ID,
+					      VMCI_QUEUEPAIR_ALLOC);
+	alloc_msg->hdr.src = VMCI_ANON_SRC_HANDLE;
+	alloc_msg->hdr.payload_size = msg_size - VMCI_DG_HEADERSIZE;
+	alloc_msg->handle = entry->qp.handle;
+	alloc_msg->peer = entry->qp.peer;
+	alloc_msg->flags = entry->qp.flags;
+	alloc_msg->produce_size = entry->qp.produce_size;
+	alloc_msg->consume_size = entry->qp.consume_size;
+	alloc_msg->num_ppns = entry->num_ppns;
+
+	result = qp_populate_ppn_set((u8 *)alloc_msg + sizeof(*alloc_msg),
+				     &entry->ppn_set);
+	if (result == VMCI_SUCCESS)
+		result = vmci_send_datagram(&alloc_msg->hdr);
+
+	kfree(alloc_msg);
+
+	return result;
+}
+
+/*
+ * Helper to make a queue_pairDetach hypercall when the driver is
+ * supporting a guest device.
+ */
+static int qp_detatch_hypercall(struct vmci_handle handle)
+{
+	struct vmci_qp_detach_msg detach_msg;
+
+	detach_msg.hdr.dst = vmci_make_handle(VMCI_HYPERVISOR_CONTEXT_ID,
+					      VMCI_QUEUEPAIR_DETACH);
+	detach_msg.hdr.src = VMCI_ANON_SRC_HANDLE;
+	detach_msg.hdr.payload_size = sizeof(handle);
+	detach_msg.handle = handle;
+
+	return vmci_send_datagram(&detach_msg.hdr);
+}
+
+/*
+ * Adds the given entry to the list. Assumes that the list is locked.
+ */
+static void qp_list_add_entry(struct qp_list *qp_list, struct qp_entry *entry)
+{
+	if (entry)
+		list_add(&entry->list_item, &qp_list->head);
+}
+
+/*
+ * Removes the given entry from the list. Assumes that the list is locked.
+ */
+static void qp_list_remove_entry(struct qp_list *qp_list,
+				 struct qp_entry *entry)
+{
+	if (entry)
+		list_del(&entry->list_item);
+}
+
+/*
+ * Helper for VMCI queue_pair detach interface. Frees the physical
+ * pages for the queue pair.
+ */
+static int qp_detatch_guest_work(struct vmci_handle handle)
+{
+	int result;
+	struct qp_guest_endpoint *entry;
+	u32 ref_count = ~0;	/* To avoid compiler warning below */
+
+	mutex_lock(&qp_guest_endpoints.mutex);
+
+	entry = qp_guest_handle_to_entry(handle);
+	if (!entry) {
+		mutex_unlock(&qp_guest_endpoints.mutex);
+		return VMCI_ERROR_NOT_FOUND;
+	}
+
+	if (entry->qp.flags & VMCI_QPFLAG_LOCAL) {
+		result = VMCI_SUCCESS;
+
+		if (entry->qp.ref_count > 1) {
+			result = qp_notify_peer_local(false, handle);
+			/*
+			 * We can fail to notify a local queuepair
+			 * because we can't allocate.  We still want
+			 * to release the entry if that happens, so
+			 * don't bail out yet.
+			 */
+		}
+	} else {
+		result = qp_detatch_hypercall(handle);
+		if (result < VMCI_SUCCESS) {
+			/*
+			 * We failed to notify a non-local queuepair.
+			 * That other queuepair might still be
+			 * accessing the shared memory, so don't
+			 * release the entry yet.  It will get cleaned
+			 * up by VMCIqueue_pair_Exit() if necessary
+			 * (assuming we are going away, otherwise why
+			 * did this fail?).
+			 */
+
+			mutex_unlock(&qp_guest_endpoints.mutex);
+			return result;
+		}
+	}
+
+	/*
+	 * If we get here then we either failed to notify a local queuepair, or
+	 * we succeeded in all cases.  Release the entry if required.
+	 */
+
+	entry->qp.ref_count--;
+	if (entry->qp.ref_count == 0)
+		qp_list_remove_entry(&qp_guest_endpoints, &entry->qp);
+
+	/* If we didn't remove the entry, this could change once we unlock. */
+	if (entry)
+		ref_count = entry->qp.ref_count;
+
+	mutex_unlock(&qp_guest_endpoints.mutex);
+
+	if (ref_count == 0)
+		qp_guest_endpoint_destroy(entry);
+
+	return result;
+}
+
+/*
+ * This functions handles the actual allocation of a VMCI queue
+ * pair guest endpoint. Allocates physical pages for the queue
+ * pair. It makes OS dependent calls through generic wrappers.
+ */
+static int qp_alloc_guest_work(struct vmci_handle *handle,
+			       struct vmci_queue **produce_q,
+			       u64 produce_size,
+			       struct vmci_queue **consume_q,
+			       u64 consume_size,
+			       u32 peer,
+			       u32 flags,
+			       u32 priv_flags)
+{
+	const u64 num_produce_pages =
+	    dm_div_up(produce_size, PAGE_SIZE) + 1;
+	const u64 num_consume_pages =
+	    dm_div_up(consume_size, PAGE_SIZE) + 1;
+	void *my_produce_q = NULL;
+	void *my_consume_q = NULL;
+	int result;
+	struct qp_guest_endpoint *queue_pair_entry = NULL;
+
+	if (priv_flags != VMCI_NO_PRIVILEGE_FLAGS)
+		return VMCI_ERROR_NO_ACCESS;
+
+	mutex_lock(&qp_guest_endpoints.mutex);
+
+	queue_pair_entry = qp_guest_handle_to_entry(*handle);
+	if (queue_pair_entry) {
+		if (queue_pair_entry->qp.flags & VMCI_QPFLAG_LOCAL) {
+			/* Local attach case. */
+			if (queue_pair_entry->qp.ref_count > 1) {
+				pr_devel("Error attempting to attach more than once\n");
+				result = VMCI_ERROR_UNAVAILABLE;
+				goto error_keep_entry;
+			}
+
+			if (queue_pair_entry->qp.produce_size != consume_size ||
+			    queue_pair_entry->qp.consume_size !=
+			    produce_size ||
+			    queue_pair_entry->qp.flags !=
+			    (flags & ~VMCI_QPFLAG_ATTACH_ONLY)) {
+				pr_devel("Error mismatched queue pair in local attach\n");
+				result = VMCI_ERROR_QUEUEPAIR_MISMATCH;
+				goto error_keep_entry;
+			}
+
+			/*
+			 * Do a local attach.  We swap the consume and
+			 * produce queues for the attacher and deliver
+			 * an attach event.
+			 */
+			result = qp_notify_peer_local(true, *handle);
+			if (result < VMCI_SUCCESS)
+				goto error_keep_entry;
+
+			my_produce_q = queue_pair_entry->consume_q;
+			my_consume_q = queue_pair_entry->produce_q;
+			goto out;
+		}
+
+		result = VMCI_ERROR_ALREADY_EXISTS;
+		goto error_keep_entry;
+	}
+
+	my_produce_q = qp_alloc_queue(produce_size, flags);
+	if (!my_produce_q) {
+		pr_warn("Error allocating pages for produce queue\n");
+		result = VMCI_ERROR_NO_MEM;
+		goto error;
+	}
+
+	my_consume_q = qp_alloc_queue(consume_size, flags);
+	if (!my_consume_q) {
+		pr_warn("Error allocating pages for consume queue\n");
+		result = VMCI_ERROR_NO_MEM;
+		goto error;
+	}
+
+	queue_pair_entry = qp_guest_endpoint_create(*handle, peer, flags,
+						    produce_size, consume_size,
+						    my_produce_q, my_consume_q);
+	if (!queue_pair_entry) {
+		pr_warn("Error allocating memory in %s\n", __func__);
+		result = VMCI_ERROR_NO_MEM;
+		goto error;
+	}
+
+	result = qp_alloc_ppn_set(my_produce_q, num_produce_pages, my_consume_q,
+				  num_consume_pages,
+				  &queue_pair_entry->ppn_set);
+	if (result < VMCI_SUCCESS) {
+		pr_warn("qp_alloc_ppn_set failed\n");
+		goto error;
+	}
+
+	/*
+	 * It's only necessary to notify the host if this queue pair will be
+	 * attached to from another context.
+	 */
+	if (queue_pair_entry->qp.flags & VMCI_QPFLAG_LOCAL) {
+		/* Local create case. */
+		u32 context_id = vmci_get_context_id();
+
+		/*
+		 * Enforce similar checks on local queue pairs as we
+		 * do for regular ones.  The handle's context must
+		 * match the creator or attacher context id (here they
+		 * are both the current context id) and the
+		 * attach-only flag cannot exist during create.  We
+		 * also ensure specified peer is this context or an
+		 * invalid one.
+		 */
+		if (queue_pair_entry->qp.handle.context != context_id ||
+		    (queue_pair_entry->qp.peer != VMCI_INVALID_ID &&
+		     queue_pair_entry->qp.peer != context_id)) {
+			result = VMCI_ERROR_NO_ACCESS;
+			goto error;
+		}
+
+		if (queue_pair_entry->qp.flags & VMCI_QPFLAG_ATTACH_ONLY) {
+			result = VMCI_ERROR_NOT_FOUND;
+			goto error;
+		}
+	} else {
+		result = qp_alloc_hypercall(queue_pair_entry);
+		if (result < VMCI_SUCCESS) {
+			pr_warn("qp_alloc_hypercall result = %d\n", result);
+			goto error;
+		}
+	}
+
+	qp_init_queue_mutex((struct vmci_queue *)my_produce_q,
+			    (struct vmci_queue *)my_consume_q);
+
+	qp_list_add_entry(&qp_guest_endpoints, &queue_pair_entry->qp);
+
+ out:
+	queue_pair_entry->qp.ref_count++;
+	*handle = queue_pair_entry->qp.handle;
+	*produce_q = (struct vmci_queue *)my_produce_q;
+	*consume_q = (struct vmci_queue *)my_consume_q;
+
+	/*
+	 * We should initialize the queue pair header pages on a local
+	 * queue pair create.  For non-local queue pairs, the
+	 * hypervisor initializes the header pages in the create step.
+	 */
+	if ((queue_pair_entry->qp.flags & VMCI_QPFLAG_LOCAL) &&
+	    queue_pair_entry->qp.ref_count == 1) {
+		vmci_q_header_init((*produce_q)->q_header, *handle);
+		vmci_q_header_init((*consume_q)->q_header, *handle);
+	}
+
+	mutex_unlock(&qp_guest_endpoints.mutex);
+
+	return VMCI_SUCCESS;
+
+ error:
+	mutex_unlock(&qp_guest_endpoints.mutex);
+	if (queue_pair_entry) {
+		/* The queues will be freed inside the destroy routine. */
+		qp_guest_endpoint_destroy(queue_pair_entry);
+	} else {
+		qp_free_queue(my_produce_q, produce_size);
+		qp_free_queue(my_consume_q, consume_size);
+	}
+	return result;
+
+ error_keep_entry:
+	/* This path should only be used when an existing entry was found. */
+	mutex_unlock(&qp_guest_endpoints.mutex);
+	return result;
+}
+
+/*
+ * The first endpoint issuing a queue pair allocation will create the state
+ * of the queue pair in the queue pair broker.
+ *
+ * If the creator is a guest, it will associate a VMX virtual address range
+ * with the queue pair as specified by the page_store. For compatibility with
+ * older VMX'en, that would use a separate step to set the VMX virtual
+ * address range, the virtual address range can be registered later using
+ * vmci_qp_broker_set_page_store. In that case, a page_store of NULL should be
+ * used.
+ *
+ * If the creator is the host, a page_store of NULL should be used as well,
+ * since the host is not able to supply a page store for the queue pair.
+ *
+ * For older VMX and host callers, the queue pair will be created in the
+ * VMCIQPB_CREATED_NO_MEM state, and for current VMX callers, it will be
+ * created in VMCOQPB_CREATED_MEM state.
+ */
+static int qp_broker_create(struct vmci_handle handle,
+			    u32 peer,
+			    u32 flags,
+			    u32 priv_flags,
+			    u64 produce_size,
+			    u64 consume_size,
+			    struct vmci_qp_page_store *page_store,
+			    struct vmci_ctx *context,
+			    vmci_event_release_cb wakeup_cb,
+			    void *client_data, struct qp_broker_entry **ent)
+{
+	struct qp_broker_entry *entry = NULL;
+	const u32 context_id = vmci_ctx_get_id(context);
+	bool is_local = flags & VMCI_QPFLAG_LOCAL;
+	int result;
+	u64 guest_produce_size;
+	u64 guest_consume_size;
+
+	/* Do not create if the caller asked not to. */
+	if (flags & VMCI_QPFLAG_ATTACH_ONLY)
+		return VMCI_ERROR_NOT_FOUND;
+
+	/*
+	 * Creator's context ID should match handle's context ID or the creator
+	 * must allow the context in handle's context ID as the "peer".
+	 */
+	if (handle.context != context_id && handle.context != peer)
+		return VMCI_ERROR_NO_ACCESS;
+
+	if (VMCI_CONTEXT_IS_VM(context_id) && VMCI_CONTEXT_IS_VM(peer))
+		return VMCI_ERROR_DST_UNREACHABLE;
+
+	/*
+	 * Creator's context ID for local queue pairs should match the
+	 * peer, if a peer is specified.
+	 */
+	if (is_local && peer != VMCI_INVALID_ID && context_id != peer)
+		return VMCI_ERROR_NO_ACCESS;
+
+	entry = kzalloc(sizeof(*entry), GFP_ATOMIC);
+	if (!entry)
+		return VMCI_ERROR_NO_MEM;
+
+	if (vmci_ctx_get_id(context) == VMCI_HOST_CONTEXT_ID && !is_local) {
+		/*
+		 * The queue pair broker entry stores values from the guest
+		 * point of view, so a creating host side endpoint should swap
+		 * produce and consume values -- unless it is a local queue
+		 * pair, in which case no swapping is necessary, since the local
+		 * attacher will swap queues.
+		 */
+
+		guest_produce_size = consume_size;
+		guest_consume_size = produce_size;
+	} else {
+		guest_produce_size = produce_size;
+		guest_consume_size = consume_size;
+	}
+
+	entry->qp.handle = handle;
+	entry->qp.peer = peer;
+	entry->qp.flags = flags;
+	entry->qp.produce_size = guest_produce_size;
+	entry->qp.consume_size = guest_consume_size;
+	entry->qp.ref_count = 1;
+	entry->create_id = context_id;
+	entry->attach_id = VMCI_INVALID_ID;
+	entry->state = VMCIQPB_NEW;
+	entry->require_trusted_attach =
+	    !!(context->priv_flags & VMCI_PRIVILEGE_FLAG_RESTRICTED);
+	entry->created_by_trusted =
+	    !!(priv_flags & VMCI_PRIVILEGE_FLAG_TRUSTED);
+	entry->vmci_page_files = false;
+	entry->wakeup_cb = wakeup_cb;
+	entry->client_data = client_data;
+	entry->produce_q = qp_host_alloc_queue(guest_produce_size);
+	if (entry->produce_q == NULL) {
+		result = VMCI_ERROR_NO_MEM;
+		goto error;
+	}
+	entry->consume_q = qp_host_alloc_queue(guest_consume_size);
+	if (entry->consume_q == NULL) {
+		result = VMCI_ERROR_NO_MEM;
+		goto error;
+	}
+
+	qp_init_queue_mutex(entry->produce_q, entry->consume_q);
+
+	INIT_LIST_HEAD(&entry->qp.list_item);
+
+	if (is_local) {
+		u8 *tmp;
+
+		entry->local_mem = kcalloc(QPE_NUM_PAGES(entry->qp),
+					   PAGE_SIZE, GFP_KERNEL);
+		if (entry->local_mem == NULL) {
+			result = VMCI_ERROR_NO_MEM;
+			goto error;
+		}
+		entry->state = VMCIQPB_CREATED_MEM;
+		entry->produce_q->q_header = entry->local_mem;
+		tmp = (u8 *)entry->local_mem + PAGE_SIZE *
+		    (dm_div_up(entry->qp.produce_size, PAGE_SIZE) + 1);
+		entry->consume_q->q_header = (struct vmci_queue_header *)tmp;
+	} else if (page_store) {
+		/*
+		 * The VMX already initialized the queue pair headers, so no
+		 * need for the kernel side to do that.
+		 */
+		result = qp_host_register_user_memory(page_store,
+						      entry->produce_q,
+						      entry->consume_q);
+		if (result < VMCI_SUCCESS)
+			goto error;
+
+		entry->state = VMCIQPB_CREATED_MEM;
+	} else {
+		/*
+		 * A create without a page_store may be either a host
+		 * side create (in which case we are waiting for the
+		 * guest side to supply the memory) or an old style
+		 * queue pair create (in which case we will expect a
+		 * set page store call as the next step).
+		 */
+		entry->state = VMCIQPB_CREATED_NO_MEM;
+	}
+
+	qp_list_add_entry(&qp_broker_list, &entry->qp);
+	if (ent != NULL)
+		*ent = entry;
+
+	/* Add to resource obj */
+	result = vmci_resource_add(&entry->resource,
+				   VMCI_RESOURCE_TYPE_QPAIR_HOST,
+				   handle);
+	if (result != VMCI_SUCCESS) {
+		pr_warn("Failed to add new resource (handle=0x%x:0x%x), error: %d",
+			handle.context, handle.resource, result);
+		goto error;
+	}
+
+	entry->qp.handle = vmci_resource_handle(&entry->resource);
+	if (is_local) {
+		vmci_q_header_init(entry->produce_q->q_header,
+				   entry->qp.handle);
+		vmci_q_header_init(entry->consume_q->q_header,
+				   entry->qp.handle);
+	}
+
+	vmci_ctx_qp_create(context, entry->qp.handle);
+
+	return VMCI_SUCCESS;
+
+ error:
+	if (entry != NULL) {
+		qp_host_free_queue(entry->produce_q, guest_produce_size);
+		qp_host_free_queue(entry->consume_q, guest_consume_size);
+		kfree(entry);
+	}
+
+	return result;
+}
+
+/*
+ * Enqueues an event datagram to notify the peer VM attached to
+ * the given queue pair handle about attach/detach event by the
+ * given VM.  Returns Payload size of datagram enqueued on
+ * success, error code otherwise.
+ */
+static int qp_notify_peer(bool attach,
+			  struct vmci_handle handle,
+			  u32 my_id,
+			  u32 peer_id)
+{
+	int rv;
+	struct vmci_event_qp ev;
+
+	if (vmci_handle_is_invalid(handle) || my_id == VMCI_INVALID_ID ||
+	    peer_id == VMCI_INVALID_ID)
+		return VMCI_ERROR_INVALID_ARGS;
+
+	/*
+	 * In vmci_ctx_enqueue_datagram() we enforce the upper limit on
+	 * number of pending events from the hypervisor to a given VM
+	 * otherwise a rogue VM could do an arbitrary number of attach
+	 * and detach operations causing memory pressure in the host
+	 * kernel.
+	 */
+
+	ev.msg.hdr.dst = vmci_make_handle(peer_id, VMCI_EVENT_HANDLER);
+	ev.msg.hdr.src = vmci_make_handle(VMCI_HYPERVISOR_CONTEXT_ID,
+					  VMCI_CONTEXT_RESOURCE_ID);
+	ev.msg.hdr.payload_size = sizeof(ev) - sizeof(ev.msg.hdr);
+	ev.msg.event_data.event = attach ?
+	    VMCI_EVENT_QP_PEER_ATTACH : VMCI_EVENT_QP_PEER_DETACH;
+	ev.payload.handle = handle;
+	ev.payload.peer_id = my_id;
+
+	rv = vmci_datagram_dispatch(VMCI_HYPERVISOR_CONTEXT_ID,
+				    &ev.msg.hdr, false);
+	if (rv < VMCI_SUCCESS)
+		pr_warn("Failed to enqueue queue_pair %s event datagram for context (ID=0x%x)\n",
+			attach ? "ATTACH" : "DETACH", peer_id);
+
+	return rv;
+}
+
+/*
+ * The second endpoint issuing a queue pair allocation will attach to
+ * the queue pair registered with the queue pair broker.
+ *
+ * If the attacher is a guest, it will associate a VMX virtual address
+ * range with the queue pair as specified by the page_store. At this
+ * point, the already attach host endpoint may start using the queue
+ * pair, and an attach event is sent to it. For compatibility with
+ * older VMX'en, that used a separate step to set the VMX virtual
+ * address range, the virtual address range can be registered later
+ * using vmci_qp_broker_set_page_store. In that case, a page_store of
+ * NULL should be used, and the attach event will be generated once
+ * the actual page store has been set.
+ *
+ * If the attacher is the host, a page_store of NULL should be used as
+ * well, since the page store information is already set by the guest.
+ *
+ * For new VMX and host callers, the queue pair will be moved to the
+ * VMCIQPB_ATTACHED_MEM state, and for older VMX callers, it will be
+ * moved to the VMCOQPB_ATTACHED_NO_MEM state.
+ */
+static int qp_broker_attach(struct qp_broker_entry *entry,
+			    u32 peer,
+			    u32 flags,
+			    u32 priv_flags,
+			    u64 produce_size,
+			    u64 consume_size,
+			    struct vmci_qp_page_store *page_store,
+			    struct vmci_ctx *context,
+			    vmci_event_release_cb wakeup_cb,
+			    void *client_data,
+			    struct qp_broker_entry **ent)
+{
+	const u32 context_id = vmci_ctx_get_id(context);
+	bool is_local = flags & VMCI_QPFLAG_LOCAL;
+	int result;
+
+	if (entry->state != VMCIQPB_CREATED_NO_MEM &&
+	    entry->state != VMCIQPB_CREATED_MEM)
+		return VMCI_ERROR_UNAVAILABLE;
+
+	if (is_local) {
+		if (!(entry->qp.flags & VMCI_QPFLAG_LOCAL) ||
+		    context_id != entry->create_id) {
+			return VMCI_ERROR_INVALID_ARGS;
+		}
+	} else if (context_id == entry->create_id ||
+		   context_id == entry->attach_id) {
+		return VMCI_ERROR_ALREADY_EXISTS;
+	}
+
+	if (VMCI_CONTEXT_IS_VM(context_id) &&
+	    VMCI_CONTEXT_IS_VM(entry->create_id))
+		return VMCI_ERROR_DST_UNREACHABLE;
+
+	/*
+	 * If we are attaching from a restricted context then the queuepair
+	 * must have been created by a trusted endpoint.
+	 */
+	if ((context->priv_flags & VMCI_PRIVILEGE_FLAG_RESTRICTED) &&
+	    !entry->created_by_trusted)
+		return VMCI_ERROR_NO_ACCESS;
+
+	/*
+	 * If we are attaching to a queuepair that was created by a restricted
+	 * context then we must be trusted.
+	 */
+	if (entry->require_trusted_attach &&
+	    (!(priv_flags & VMCI_PRIVILEGE_FLAG_TRUSTED)))
+		return VMCI_ERROR_NO_ACCESS;
+
+	/*
+	 * If the creator specifies VMCI_INVALID_ID in "peer" field, access
+	 * control check is not performed.
+	 */
+	if (entry->qp.peer != VMCI_INVALID_ID && entry->qp.peer != context_id)
+		return VMCI_ERROR_NO_ACCESS;
+
+	if (entry->create_id == VMCI_HOST_CONTEXT_ID) {
+		/*
+		 * Do not attach if the caller doesn't support Host Queue Pairs
+		 * and a host created this queue pair.
+		 */
+
+		if (!vmci_ctx_supports_host_qp(context))
+			return VMCI_ERROR_INVALID_RESOURCE;
+
+	} else if (context_id == VMCI_HOST_CONTEXT_ID) {
+		struct vmci_ctx *create_context;
+		bool supports_host_qp;
+
+		/*
+		 * Do not attach a host to a user created queue pair if that
+		 * user doesn't support host queue pair end points.
+		 */
+
+		create_context = vmci_ctx_get(entry->create_id);
+		supports_host_qp = vmci_ctx_supports_host_qp(create_context);
+		vmci_ctx_put(create_context);
+
+		if (!supports_host_qp)
+			return VMCI_ERROR_INVALID_RESOURCE;
+	}
+
+	if ((entry->qp.flags & ~VMCI_QP_ASYMM) != (flags & ~VMCI_QP_ASYMM_PEER))
+		return VMCI_ERROR_QUEUEPAIR_MISMATCH;
+
+	if (context_id != VMCI_HOST_CONTEXT_ID) {
+		/*
+		 * The queue pair broker entry stores values from the guest
+		 * point of view, so an attaching guest should match the values
+		 * stored in the entry.
+		 */
+
+		if (entry->qp.produce_size != produce_size ||
+		    entry->qp.consume_size != consume_size) {
+			return VMCI_ERROR_QUEUEPAIR_MISMATCH;
+		}
+	} else if (entry->qp.produce_size != consume_size ||
+		   entry->qp.consume_size != produce_size) {
+		return VMCI_ERROR_QUEUEPAIR_MISMATCH;
+	}
+
+	if (context_id != VMCI_HOST_CONTEXT_ID) {
+		/*
+		 * If a guest attached to a queue pair, it will supply
+		 * the backing memory.  If this is a pre NOVMVM vmx,
+		 * the backing memory will be supplied by calling
+		 * vmci_qp_broker_set_page_store() following the
+		 * return of the vmci_qp_broker_alloc() call. If it is
+		 * a vmx of version NOVMVM or later, the page store
+		 * must be supplied as part of the
+		 * vmci_qp_broker_alloc call.  Under all circumstances
+		 * must the initially created queue pair not have any
+		 * memory associated with it already.
+		 */
+
+		if (entry->state != VMCIQPB_CREATED_NO_MEM)
+			return VMCI_ERROR_INVALID_ARGS;
+
+		if (page_store != NULL) {
+			/*
+			 * Patch up host state to point to guest
+			 * supplied memory. The VMX already
+			 * initialized the queue pair headers, so no
+			 * need for the kernel side to do that.
+			 */
+
+			result = qp_host_register_user_memory(page_store,
+							      entry->produce_q,
+							      entry->consume_q);
+			if (result < VMCI_SUCCESS)
+				return result;
+
+			/*
+			 * Preemptively load in the headers if non-blocking to
+			 * prevent blocking later.
+			 */
+			if (entry->qp.flags & VMCI_QPFLAG_NONBLOCK) {
+				result = qp_host_map_queues(entry->produce_q,
+							    entry->consume_q);
+				if (result < VMCI_SUCCESS) {
+					qp_host_unregister_user_memory(
+						entry->produce_q,
+						entry->consume_q);
+					return result;
+				}
+			}
+
+			entry->state = VMCIQPB_ATTACHED_MEM;
+		} else {
+			entry->state = VMCIQPB_ATTACHED_NO_MEM;
+		}
+	} else if (entry->state == VMCIQPB_CREATED_NO_MEM) {
+		/*
+		 * The host side is attempting to attach to a queue
+		 * pair that doesn't have any memory associated with
+		 * it. This must be a pre NOVMVM vmx that hasn't set
+		 * the page store information yet, or a quiesced VM.
+		 */
+
+		return VMCI_ERROR_UNAVAILABLE;
+	} else {
+		/*
+		 * For non-blocking queue pairs, we cannot rely on
+		 * enqueue/dequeue to map in the pages on the
+		 * host-side, since it may block, so we make an
+		 * attempt here.
+		 */
+
+		if (flags & VMCI_QPFLAG_NONBLOCK) {
+			result =
+			    qp_host_map_queues(entry->produce_q,
+					       entry->consume_q);
+			if (result < VMCI_SUCCESS)
+				return result;
+
+			entry->qp.flags |= flags &
+			    (VMCI_QPFLAG_NONBLOCK | VMCI_QPFLAG_PINNED);
+		}
+
+		/* The host side has successfully attached to a queue pair. */
+		entry->state = VMCIQPB_ATTACHED_MEM;
+	}
+
+	if (entry->state == VMCIQPB_ATTACHED_MEM) {
+		result =
+		    qp_notify_peer(true, entry->qp.handle, context_id,
+				   entry->create_id);
+		if (result < VMCI_SUCCESS)
+			pr_warn("Failed to notify peer (ID=0x%x) of attach to queue pair (handle=0x%x:0x%x)\n",
+				entry->create_id, entry->qp.handle.context,
+				entry->qp.handle.resource);
+	}
+
+	entry->attach_id = context_id;
+	entry->qp.ref_count++;
+	if (wakeup_cb) {
+		entry->wakeup_cb = wakeup_cb;
+		entry->client_data = client_data;
+	}
+
+	/*
+	 * When attaching to local queue pairs, the context already has
+	 * an entry tracking the queue pair, so don't add another one.
+	 */
+	if (!is_local)
+		vmci_ctx_qp_create(context, entry->qp.handle);
+
+	if (ent != NULL)
+		*ent = entry;
+
+	return VMCI_SUCCESS;
+}
+
+/*
+ * queue_pair_Alloc for use when setting up queue pair endpoints
+ * on the host.
+ */
+static int qp_broker_alloc(struct vmci_handle handle,
+			   u32 peer,
+			   u32 flags,
+			   u32 priv_flags,
+			   u64 produce_size,
+			   u64 consume_size,
+			   struct vmci_qp_page_store *page_store,
+			   struct vmci_ctx *context,
+			   vmci_event_release_cb wakeup_cb,
+			   void *client_data,
+			   struct qp_broker_entry **ent,
+			   bool *swap)
+{
+	const u32 context_id = vmci_ctx_get_id(context);
+	bool create;
+	struct qp_broker_entry *entry = NULL;
+	bool is_local = flags & VMCI_QPFLAG_LOCAL;
+	int result;
+
+	if (vmci_handle_is_invalid(handle) ||
+	    (flags & ~VMCI_QP_ALL_FLAGS) || is_local ||
+	    !(produce_size || consume_size) ||
+	    !context || context_id == VMCI_INVALID_ID ||
+	    handle.context == VMCI_INVALID_ID) {
+		return VMCI_ERROR_INVALID_ARGS;
+	}
+
+	if (page_store && !VMCI_QP_PAGESTORE_IS_WELLFORMED(page_store))
+		return VMCI_ERROR_INVALID_ARGS;
+
+	/*
+	 * In the initial argument check, we ensure that non-vmkernel hosts
+	 * are not allowed to create local queue pairs.
+	 */
+
+	mutex_lock(&qp_broker_list.mutex);
+
+	if (!is_local && vmci_ctx_qp_exists(context, handle)) {
+		pr_devel("Context (ID=0x%x) already attached to queue pair (handle=0x%x:0x%x)\n",
+			 context_id, handle.context, handle.resource);
+		mutex_unlock(&qp_broker_list.mutex);
+		return VMCI_ERROR_ALREADY_EXISTS;
+	}
+
+	if (handle.resource != VMCI_INVALID_ID)
+		entry = qp_broker_handle_to_entry(handle);
+
+	if (!entry) {
+		create = true;
+		result =
+		    qp_broker_create(handle, peer, flags, priv_flags,
+				     produce_size, consume_size, page_store,
+				     context, wakeup_cb, client_data, ent);
+	} else {
+		create = false;
+		result =
+		    qp_broker_attach(entry, peer, flags, priv_flags,
+				     produce_size, consume_size, page_store,
+				     context, wakeup_cb, client_data, ent);
+	}
+
+	mutex_unlock(&qp_broker_list.mutex);
+
+	if (swap)
+		*swap = (context_id == VMCI_HOST_CONTEXT_ID) &&
+		    !(create && is_local);
+
+	return result;
+}
+
+/*
+ * This function implements the kernel API for allocating a queue
+ * pair.
+ */
+static int qp_alloc_host_work(struct vmci_handle *handle,
+			      struct vmci_queue **produce_q,
+			      u64 produce_size,
+			      struct vmci_queue **consume_q,
+			      u64 consume_size,
+			      u32 peer,
+			      u32 flags,
+			      u32 priv_flags,
+			      vmci_event_release_cb wakeup_cb,
+			      void *client_data)
+{
+	struct vmci_handle new_handle;
+	struct vmci_ctx *context;
+	struct qp_broker_entry *entry;
+	int result;
+	bool swap;
+
+	if (vmci_handle_is_invalid(*handle)) {
+		new_handle = vmci_make_handle(
+			VMCI_HOST_CONTEXT_ID, VMCI_INVALID_ID);
+	} else
+		new_handle = *handle;
+
+	context = vmci_ctx_get(VMCI_HOST_CONTEXT_ID);
+	entry = NULL;
+	result =
+	    qp_broker_alloc(new_handle, peer, flags, priv_flags,
+			    produce_size, consume_size, NULL, context,
+			    wakeup_cb, client_data, &entry, &swap);
+	if (result == VMCI_SUCCESS) {
+		if (swap) {
+			/*
+			 * If this is a local queue pair, the attacher
+			 * will swap around produce and consume
+			 * queues.
+			 */
+
+			*produce_q = entry->consume_q;
+			*consume_q = entry->produce_q;
+		} else {
+			*produce_q = entry->produce_q;
+			*consume_q = entry->consume_q;
+		}
+
+		*handle = vmci_resource_handle(&entry->resource);
+	} else {
+		*handle = VMCI_INVALID_HANDLE;
+		pr_devel("queue pair broker failed to alloc (result=%d)\n",
+			 result);
+	}
+	vmci_ctx_put(context);
+	return result;
+}
+
+/*
+ * Allocates a VMCI queue_pair. Only checks validity of input
+ * arguments. The real work is done in the host or guest
+ * specific function.
+ */
+int vmci_qp_alloc(struct vmci_handle *handle,
+		  struct vmci_queue **produce_q,
+		  u64 produce_size,
+		  struct vmci_queue **consume_q,
+		  u64 consume_size,
+		  u32 peer,
+		  u32 flags,
+		  u32 priv_flags,
+		  bool guest_endpoint,
+		  vmci_event_release_cb wakeup_cb,
+		  void *client_data)
+{
+	if (!handle || !produce_q || !consume_q ||
+	    (!produce_size && !consume_size) || (flags & ~VMCI_QP_ALL_FLAGS))
+		return VMCI_ERROR_INVALID_ARGS;
+
+	if (guest_endpoint) {
+		return qp_alloc_guest_work(handle, produce_q,
+					   produce_size, consume_q,
+					   consume_size, peer,
+					   flags, priv_flags);
+	} else {
+		return qp_alloc_host_work(handle, produce_q,
+					  produce_size, consume_q,
+					  consume_size, peer, flags,
+					  priv_flags, wakeup_cb, client_data);
+	}
+}
+
+/*
+ * This function implements the host kernel API for detaching from
+ * a queue pair.
+ */
+static int qp_detatch_host_work(struct vmci_handle handle)
+{
+	int result;
+	struct vmci_ctx *context;
+
+	context = vmci_ctx_get(VMCI_HOST_CONTEXT_ID);
+
+	result = vmci_qp_broker_detach(handle, context);
+
+	vmci_ctx_put(context);
+	return result;
+}
+
+/*
+ * Detaches from a VMCI queue_pair. Only checks validity of input argument.
+ * Real work is done in the host or guest specific function.
+ */
+static int qp_detatch(struct vmci_handle handle, bool guest_endpoint)
+{
+	if (vmci_handle_is_invalid(handle))
+		return VMCI_ERROR_INVALID_ARGS;
+
+	if (guest_endpoint)
+		return qp_detatch_guest_work(handle);
+	else
+		return qp_detatch_host_work(handle);
+}
+
+/*
+ * Returns the entry from the head of the list. Assumes that the list is
+ * locked.
+ */
+static struct qp_entry *qp_list_get_head(struct qp_list *qp_list)
+{
+	if (!list_empty(&qp_list->head)) {
+		struct qp_entry *entry =
+		    list_first_entry(&qp_list->head, struct qp_entry,
+				     list_item);
+		return entry;
+	}
+
+	return NULL;
+}
+
+void vmci_qp_broker_exit(void)
+{
+	struct qp_entry *entry;
+	struct qp_broker_entry *be;
+
+	mutex_lock(&qp_broker_list.mutex);
+
+	while ((entry = qp_list_get_head(&qp_broker_list))) {
+		be = (struct qp_broker_entry *)entry;
+
+		qp_list_remove_entry(&qp_broker_list, entry);
+		kfree(be);
+	}
+
+	mutex_unlock(&qp_broker_list.mutex);
+}
+
+/*
+ * Requests that a queue pair be allocated with the VMCI queue
+ * pair broker. Allocates a queue pair entry if one does not
+ * exist. Attaches to one if it exists, and retrieves the page
+ * files backing that queue_pair.  Assumes that the queue pair
+ * broker lock is held.
+ */
+int vmci_qp_broker_alloc(struct vmci_handle handle,
+			 u32 peer,
+			 u32 flags,
+			 u32 priv_flags,
+			 u64 produce_size,
+			 u64 consume_size,
+			 struct vmci_qp_page_store *page_store,
+			 struct vmci_ctx *context)
+{
+	return qp_broker_alloc(handle, peer, flags, priv_flags,
+			       produce_size, consume_size,
+			       page_store, context, NULL, NULL, NULL, NULL);
+}
+
+/*
+ * VMX'en with versions lower than VMCI_VERSION_NOVMVM use a separate
+ * step to add the UVAs of the VMX mapping of the queue pair. This function
+ * provides backwards compatibility with such VMX'en, and takes care of
+ * registering the page store for a queue pair previously allocated by the
+ * VMX during create or attach. This function will move the queue pair state
+ * to either from VMCIQBP_CREATED_NO_MEM to VMCIQBP_CREATED_MEM or
+ * VMCIQBP_ATTACHED_NO_MEM to VMCIQBP_ATTACHED_MEM. If moving to the
+ * attached state with memory, the queue pair is ready to be used by the
+ * host peer, and an attached event will be generated.
+ *
+ * Assumes that the queue pair broker lock is held.
+ *
+ * This function is only used by the hosted platform, since there is no
+ * issue with backwards compatibility for vmkernel.
+ */
+int vmci_qp_broker_set_page_store(struct vmci_handle handle,
+				  u64 produce_uva,
+				  u64 consume_uva,
+				  struct vmci_ctx *context)
+{
+	struct qp_broker_entry *entry;
+	int result;
+	const u32 context_id = vmci_ctx_get_id(context);
+
+	if (vmci_handle_is_invalid(handle) || !context ||
+	    context_id == VMCI_INVALID_ID)
+		return VMCI_ERROR_INVALID_ARGS;
+
+	/*
+	 * We only support guest to host queue pairs, so the VMX must
+	 * supply UVAs for the mapped page files.
+	 */
+
+	if (produce_uva == 0 || consume_uva == 0)
+		return VMCI_ERROR_INVALID_ARGS;
+
+	mutex_lock(&qp_broker_list.mutex);
+
+	if (!vmci_ctx_qp_exists(context, handle)) {
+		pr_warn("Context (ID=0x%x) not attached to queue pair (handle=0x%x:0x%x)\n",
+			context_id, handle.context, handle.resource);
+		result = VMCI_ERROR_NOT_FOUND;
+		goto out;
+	}
+
+	entry = qp_broker_handle_to_entry(handle);
+	if (!entry) {
+		result = VMCI_ERROR_NOT_FOUND;
+		goto out;
+	}
+
+	/*
+	 * If I'm the owner then I can set the page store.
+	 *
+	 * Or, if a host created the queue_pair and I'm the attached peer
+	 * then I can set the page store.
+	 */
+	if (entry->create_id != context_id &&
+	    (entry->create_id != VMCI_HOST_CONTEXT_ID ||
+	     entry->attach_id != context_id)) {
+		result = VMCI_ERROR_QUEUEPAIR_NOTOWNER;
+		goto out;
+	}
+
+	if (entry->state != VMCIQPB_CREATED_NO_MEM &&
+	    entry->state != VMCIQPB_ATTACHED_NO_MEM) {
+		result = VMCI_ERROR_UNAVAILABLE;
+		goto out;
+	}
+
+	result = qp_host_get_user_memory(produce_uva, consume_uva,
+					 entry->produce_q, entry->consume_q);
+	if (result < VMCI_SUCCESS)
+		goto out;
+
+	result = qp_host_map_queues(entry->produce_q, entry->consume_q);
+	if (result < VMCI_SUCCESS) {
+		qp_host_unregister_user_memory(entry->produce_q,
+					       entry->consume_q);
+		goto out;
+	}
+
+	if (entry->state == VMCIQPB_CREATED_NO_MEM)
+		entry->state = VMCIQPB_CREATED_MEM;
+	else
+		entry->state = VMCIQPB_ATTACHED_MEM;
+
+	entry->vmci_page_files = true;
+
+	if (entry->state == VMCIQPB_ATTACHED_MEM) {
+		result =
+		    qp_notify_peer(true, handle, context_id, entry->create_id);
+		if (result < VMCI_SUCCESS) {
+			pr_warn("Failed to notify peer (ID=0x%x) of attach to queue pair (handle=0x%x:0x%x)\n",
+				entry->create_id, entry->qp.handle.context,
+				entry->qp.handle.resource);
+		}
+	}
+
+	result = VMCI_SUCCESS;
+ out:
+	mutex_unlock(&qp_broker_list.mutex);
+	return result;
+}
+
+/*
+ * Resets saved queue headers for the given QP broker
+ * entry. Should be used when guest memory becomes available
+ * again, or the guest detaches.
+ */
+static void qp_reset_saved_headers(struct qp_broker_entry *entry)
+{
+	entry->produce_q->saved_header = NULL;
+	entry->consume_q->saved_header = NULL;
+}
+
+/*
+ * The main entry point for detaching from a queue pair registered with the
+ * queue pair broker. If more than one endpoint is attached to the queue
+ * pair, the first endpoint will mainly decrement a reference count and
+ * generate a notification to its peer. The last endpoint will clean up
+ * the queue pair state registered with the broker.
+ *
+ * When a guest endpoint detaches, it will unmap and unregister the guest
+ * memory backing the queue pair. If the host is still attached, it will
+ * no longer be able to access the queue pair content.
+ *
+ * If the queue pair is already in a state where there is no memory
+ * registered for the queue pair (any *_NO_MEM state), it will transition to
+ * the VMCIQPB_SHUTDOWN_NO_MEM state. This will also happen, if a guest
+ * endpoint is the first of two endpoints to detach. If the host endpoint is
+ * the first out of two to detach, the queue pair will move to the
+ * VMCIQPB_SHUTDOWN_MEM state.
+ */
+int vmci_qp_broker_detach(struct vmci_handle handle, struct vmci_ctx *context)
+{
+	struct qp_broker_entry *entry;
+	const u32 context_id = vmci_ctx_get_id(context);
+	u32 peer_id;
+	bool is_local = false;
+	int result;
+
+	if (vmci_handle_is_invalid(handle) || !context ||
+	    context_id == VMCI_INVALID_ID) {
+		return VMCI_ERROR_INVALID_ARGS;
+	}
+
+	mutex_lock(&qp_broker_list.mutex);
+
+	if (!vmci_ctx_qp_exists(context, handle)) {
+		pr_devel("Context (ID=0x%x) not attached to queue pair (handle=0x%x:0x%x)\n",
+			 context_id, handle.context, handle.resource);
+		result = VMCI_ERROR_NOT_FOUND;
+		goto out;
+	}
+
+	entry = qp_broker_handle_to_entry(handle);
+	if (!entry) {
+		pr_devel("Context (ID=0x%x) reports being attached to queue pair(handle=0x%x:0x%x) that isn't present in broker\n",
+			 context_id, handle.context, handle.resource);
+		result = VMCI_ERROR_NOT_FOUND;
+		goto out;
+	}
+
+	if (context_id != entry->create_id && context_id != entry->attach_id) {
+		result = VMCI_ERROR_QUEUEPAIR_NOTATTACHED;
+		goto out;
+	}
+
+	if (context_id == entry->create_id) {
+		peer_id = entry->attach_id;
+		entry->create_id = VMCI_INVALID_ID;
+	} else {
+		peer_id = entry->create_id;
+		entry->attach_id = VMCI_INVALID_ID;
+	}
+	entry->qp.ref_count--;
+
+	is_local = entry->qp.flags & VMCI_QPFLAG_LOCAL;
+
+	if (context_id != VMCI_HOST_CONTEXT_ID) {
+		bool headers_mapped;
+
+		/*
+		 * Pre NOVMVM vmx'en may detach from a queue pair
+		 * before setting the page store, and in that case
+		 * there is no user memory to detach from. Also, more
+		 * recent VMX'en may detach from a queue pair in the
+		 * quiesced state.
+		 */
+
+		qp_acquire_queue_mutex(entry->produce_q);
+		headers_mapped = entry->produce_q->q_header ||
+		    entry->consume_q->q_header;
+		if (QPBROKERSTATE_HAS_MEM(entry)) {
+			result =
+			    qp_host_unmap_queues(INVALID_VMCI_GUEST_MEM_ID,
+						 entry->produce_q,
+						 entry->consume_q);
+			if (result < VMCI_SUCCESS)
+				pr_warn("Failed to unmap queue headers for queue pair (handle=0x%x:0x%x,result=%d)\n",
+					handle.context, handle.resource,
+					result);
+
+			if (entry->vmci_page_files)
+				qp_host_unregister_user_memory(entry->produce_q,
+							       entry->
+							       consume_q);
+			else
+				qp_host_unregister_user_memory(entry->produce_q,
+							       entry->
+							       consume_q);
+
+		}
+
+		if (!headers_mapped)
+			qp_reset_saved_headers(entry);
+
+		qp_release_queue_mutex(entry->produce_q);
+
+		if (!headers_mapped && entry->wakeup_cb)
+			entry->wakeup_cb(entry->client_data);
+
+	} else {
+		if (entry->wakeup_cb) {
+			entry->wakeup_cb = NULL;
+			entry->client_data = NULL;
+		}
+	}
+
+	if (entry->qp.ref_count == 0) {
+		qp_list_remove_entry(&qp_broker_list, &entry->qp);
+
+		if (is_local)
+			kfree(entry->local_mem);
+
+		qp_cleanup_queue_mutex(entry->produce_q, entry->consume_q);
+		qp_host_free_queue(entry->produce_q, entry->qp.produce_size);
+		qp_host_free_queue(entry->consume_q, entry->qp.consume_size);
+		/* Unlink from resource hash table and free callback */
+		vmci_resource_remove(&entry->resource);
+
+		kfree(entry);
+
+		vmci_ctx_qp_destroy(context, handle);
+	} else {
+		qp_notify_peer(false, handle, context_id, peer_id);
+		if (context_id == VMCI_HOST_CONTEXT_ID &&
+		    QPBROKERSTATE_HAS_MEM(entry)) {
+			entry->state = VMCIQPB_SHUTDOWN_MEM;
+		} else {
+			entry->state = VMCIQPB_SHUTDOWN_NO_MEM;
+		}
+
+		if (!is_local)
+			vmci_ctx_qp_destroy(context, handle);
+
+	}
+	result = VMCI_SUCCESS;
+ out:
+	mutex_unlock(&qp_broker_list.mutex);
+	return result;
+}
+
+/*
+ * Establishes the necessary mappings for a queue pair given a
+ * reference to the queue pair guest memory. This is usually
+ * called when a guest is unquiesced and the VMX is allowed to
+ * map guest memory once again.
+ */
+int vmci_qp_broker_map(struct vmci_handle handle,
+		       struct vmci_ctx *context,
+		       u64 guest_mem)
+{
+	struct qp_broker_entry *entry;
+	const u32 context_id = vmci_ctx_get_id(context);
+	bool is_local = false;
+	int result;
+
+	if (vmci_handle_is_invalid(handle) || !context ||
+	    context_id == VMCI_INVALID_ID)
+		return VMCI_ERROR_INVALID_ARGS;
+
+	mutex_lock(&qp_broker_list.mutex);
+
+	if (!vmci_ctx_qp_exists(context, handle)) {
+		pr_devel("Context (ID=0x%x) not attached to queue pair (handle=0x%x:0x%x)\n",
+			 context_id, handle.context, handle.resource);
+		result = VMCI_ERROR_NOT_FOUND;
+		goto out;
+	}
+
+	entry = qp_broker_handle_to_entry(handle);
+	if (!entry) {
+		pr_devel("Context (ID=0x%x) reports being attached to queue pair (handle=0x%x:0x%x) that isn't present in broker\n",
+			 context_id, handle.context, handle.resource);
+		result = VMCI_ERROR_NOT_FOUND;
+		goto out;
+	}
+
+	if (context_id != entry->create_id && context_id != entry->attach_id) {
+		result = VMCI_ERROR_QUEUEPAIR_NOTATTACHED;
+		goto out;
+	}
+
+	is_local = entry->qp.flags & VMCI_QPFLAG_LOCAL;
+	result = VMCI_SUCCESS;
+
+	if (context_id != VMCI_HOST_CONTEXT_ID) {
+		struct vmci_qp_page_store page_store;
+
+		page_store.pages = guest_mem;
+		page_store.len = QPE_NUM_PAGES(entry->qp);
+
+		qp_acquire_queue_mutex(entry->produce_q);
+		qp_reset_saved_headers(entry);
+		result =
+		    qp_host_register_user_memory(&page_store,
+						 entry->produce_q,
+						 entry->consume_q);
+		qp_release_queue_mutex(entry->produce_q);
+		if (result == VMCI_SUCCESS) {
+			/* Move state from *_NO_MEM to *_MEM */
+
+			entry->state++;
+
+			if (entry->wakeup_cb)
+				entry->wakeup_cb(entry->client_data);
+		}
+	}
+
+ out:
+	mutex_unlock(&qp_broker_list.mutex);
+	return result;
+}
+
+/*
+ * Saves a snapshot of the queue headers for the given QP broker
+ * entry. Should be used when guest memory is unmapped.
+ * Results:
+ * VMCI_SUCCESS on success, appropriate error code if guest memory
+ * can't be accessed..
+ */
+static int qp_save_headers(struct qp_broker_entry *entry)
+{
+	int result;
+
+	if (entry->produce_q->saved_header != NULL &&
+	    entry->consume_q->saved_header != NULL) {
+		/*
+		 *  If the headers have already been saved, we don't need to do
+		 *  it again, and we don't want to map in the headers
+		 *  unnecessarily.
+		 */
+
+		return VMCI_SUCCESS;
+	}
+
+	if (NULL == entry->produce_q->q_header ||
+	    NULL == entry->consume_q->q_header) {
+		result = qp_host_map_queues(entry->produce_q, entry->consume_q);
+		if (result < VMCI_SUCCESS)
+			return result;
+	}
+
+	memcpy(&entry->saved_produce_q, entry->produce_q->q_header,
+	       sizeof(entry->saved_produce_q));
+	entry->produce_q->saved_header = &entry->saved_produce_q;
+	memcpy(&entry->saved_consume_q, entry->consume_q->q_header,
+	       sizeof(entry->saved_consume_q));
+	entry->consume_q->saved_header = &entry->saved_consume_q;
+
+	return VMCI_SUCCESS;
+}
+
+/*
+ * Removes all references to the guest memory of a given queue pair, and
+ * will move the queue pair from state *_MEM to *_NO_MEM. It is usually
+ * called when a VM is being quiesced where access to guest memory should
+ * avoided.
+ */
+int vmci_qp_broker_unmap(struct vmci_handle handle,
+			 struct vmci_ctx *context,
+			 u32 gid)
+{
+	struct qp_broker_entry *entry;
+	const u32 context_id = vmci_ctx_get_id(context);
+	bool is_local = false;
+	int result;
+
+	if (vmci_handle_is_invalid(handle) || !context ||
+	    context_id == VMCI_INVALID_ID)
+		return VMCI_ERROR_INVALID_ARGS;
+
+	mutex_lock(&qp_broker_list.mutex);
+
+	if (!vmci_ctx_qp_exists(context, handle)) {
+		pr_devel("Context (ID=0x%x) not attached to queue pair (handle=0x%x:0x%x)\n",
+			 context_id, handle.context, handle.resource);
+		result = VMCI_ERROR_NOT_FOUND;
+		goto out;
+	}
+
+	entry = qp_broker_handle_to_entry(handle);
+	if (!entry) {
+		pr_devel("Context (ID=0x%x) reports being attached to queue pair (handle=0x%x:0x%x) that isn't present in broker\n",
+			 context_id, handle.context, handle.resource);
+		result = VMCI_ERROR_NOT_FOUND;
+		goto out;
+	}
+
+	if (context_id != entry->create_id && context_id != entry->attach_id) {
+		result = VMCI_ERROR_QUEUEPAIR_NOTATTACHED;
+		goto out;
+	}
+
+	is_local = entry->qp.flags & VMCI_QPFLAG_LOCAL;
+
+	if (context_id != VMCI_HOST_CONTEXT_ID) {
+		qp_acquire_queue_mutex(entry->produce_q);
+		result = qp_save_headers(entry);
+		if (result < VMCI_SUCCESS)
+			pr_warn("Failed to save queue headers for queue pair (handle=0x%x:0x%x,result=%d)\n",
+				handle.context, handle.resource, result);
+
+		qp_host_unmap_queues(gid, entry->produce_q, entry->consume_q);
+
+		/*
+		 * On hosted, when we unmap queue pairs, the VMX will also
+		 * unmap the guest memory, so we invalidate the previously
+		 * registered memory. If the queue pair is mapped again at a
+		 * later point in time, we will need to reregister the user
+		 * memory with a possibly new user VA.
+		 */
+		qp_host_unregister_user_memory(entry->produce_q,
+					       entry->consume_q);
+
+		/*
+		 * Move state from *_MEM to *_NO_MEM.
+		 */
+		entry->state--;
+
+		qp_release_queue_mutex(entry->produce_q);
+	}
+
+	result = VMCI_SUCCESS;
+
+ out:
+	mutex_unlock(&qp_broker_list.mutex);
+	return result;
+}
+
+/*
+ * Destroys all guest queue pair endpoints. If active guest queue
+ * pairs still exist, hypercalls to attempt detach from these
+ * queue pairs will be made. Any failure to detach is silently
+ * ignored.
+ */
+void vmci_qp_guest_endpoints_exit(void)
+{
+	struct qp_entry *entry;
+	struct qp_guest_endpoint *ep;
+
+	mutex_lock(&qp_guest_endpoints.mutex);
+
+	while ((entry = qp_list_get_head(&qp_guest_endpoints))) {
+		ep = (struct qp_guest_endpoint *)entry;
+
+		/* Don't make a hypercall for local queue_pairs. */
+		if (!(entry->flags & VMCI_QPFLAG_LOCAL))
+			qp_detatch_hypercall(entry->handle);
+
+		/* We cannot fail the exit, so let's reset ref_count. */
+		entry->ref_count = 0;
+		qp_list_remove_entry(&qp_guest_endpoints, entry);
+
+		qp_guest_endpoint_destroy(ep);
+	}
+
+	mutex_unlock(&qp_guest_endpoints.mutex);
+}
+
+/*
+ * Helper routine that will lock the queue pair before subsequent
+ * operations.
+ * Note: Non-blocking on the host side is currently only implemented in ESX.
+ * Since non-blocking isn't yet implemented on the host personality we
+ * have no reason to acquire a spin lock.  So to avoid the use of an
+ * unnecessary lock only acquire the mutex if we can block.
+ * Note: It is assumed that QPFLAG_PINNED implies QPFLAG_NONBLOCK.  Therefore
+ * we can use the same locking function for access to both the queue
+ * and the queue headers as it is the same logic.  Assert this behvior.
+ */
+static void qp_lock(const struct vmci_qp *qpair)
+{
+	if (vmci_can_block(qpair->flags))
+		qp_acquire_queue_mutex(qpair->produce_q);
+}
+
+/*
+ * Helper routine that unlocks the queue pair after calling
+ * qp_lock.  Respects non-blocking and pinning flags.
+ */
+static void qp_unlock(const struct vmci_qp *qpair)
+{
+	if (vmci_can_block(qpair->flags))
+		qp_release_queue_mutex(qpair->produce_q);
+}
+
+/*
+ * The queue headers may not be mapped at all times. If a queue is
+ * currently not mapped, it will be attempted to do so.
+ */
+static int qp_map_queue_headers(struct vmci_queue *produce_q,
+				struct vmci_queue *consume_q,
+				bool can_block)
+{
+	int result;
+
+	if (NULL == produce_q->q_header || NULL == consume_q->q_header) {
+		if (can_block)
+			result = qp_host_map_queues(produce_q, consume_q);
+		else
+			result = VMCI_ERROR_QUEUEPAIR_NOT_READY;
+
+		if (result < VMCI_SUCCESS)
+			return (produce_q->saved_header &&
+				consume_q->saved_header) ?
+			    VMCI_ERROR_QUEUEPAIR_NOT_READY :
+			    VMCI_ERROR_QUEUEPAIR_NOTATTACHED;
+	}
+
+	return VMCI_SUCCESS;
+}
+
+/*
+ * Helper routine that will retrieve the produce and consume
+ * headers of a given queue pair. If the guest memory of the
+ * queue pair is currently not available, the saved queue headers
+ * will be returned, if these are available.
+ */
+static int qp_get_queue_headers(const struct vmci_qp *qpair,
+				struct vmci_queue_header **produce_q_header,
+				struct vmci_queue_header **consume_q_header)
+{
+	int result;
+
+	result = qp_map_queue_headers(qpair->produce_q, qpair->consume_q,
+				      vmci_can_block(qpair->flags));
+	if (result == VMCI_SUCCESS) {
+		*produce_q_header = qpair->produce_q->q_header;
+		*consume_q_header = qpair->consume_q->q_header;
+	} else if (qpair->produce_q->saved_header &&
+		   qpair->consume_q->saved_header) {
+		*produce_q_header = qpair->produce_q->saved_header;
+		*consume_q_header = qpair->consume_q->saved_header;
+		result = VMCI_SUCCESS;
+	}
+
+	return result;
+}
+
+/*
+ * Callback from VMCI queue pair broker indicating that a queue
+ * pair that was previously not ready, now either is ready or
+ * gone forever.
+ */
+static int qp_wakeup_cb(void *client_data)
+{
+	struct vmci_qp *qpair = (struct vmci_qp *)client_data;
+
+	qp_lock(qpair);
+	while (qpair->blocked > 0) {
+		qpair->blocked--;
+		qpair->generation++;
+		wake_up(&qpair->event);
+	}
+	qp_unlock(qpair);
+
+	return VMCI_SUCCESS;
+}
+
+/*
+ * Makes the calling thread wait for the queue pair to become
+ * ready for host side access.  Returns true when thread is
+ * woken up after queue pair state change, false otherwise.
+ */
+static bool qp_wait_for_ready_queue(struct vmci_qp *qpair)
+{
+	unsigned int generation;
+
+	if (qpair->flags & VMCI_QPFLAG_NONBLOCK)
+		return false;
+
+	qpair->blocked++;
+	generation = qpair->generation;
+	qp_unlock(qpair);
+	wait_event(qpair->event, generation != qpair->generation);
+	qp_lock(qpair);
+
+	return true;
+}
+
+/*
+ * Enqueues a given buffer to the produce queue using the provided
+ * function. As many bytes as possible (space available in the queue)
+ * are enqueued.  Assumes the queue->mutex has been acquired.  Returns
+ * VMCI_ERROR_QUEUEPAIR_NOSPACE if no space was available to enqueue
+ * data, VMCI_ERROR_INVALID_SIZE, if any queue pointer is outside the
+ * queue (as defined by the queue size), VMCI_ERROR_INVALID_ARGS, if
+ * an error occured when accessing the buffer,
+ * VMCI_ERROR_QUEUEPAIR_NOTATTACHED, if the queue pair pages aren't
+ * available.  Otherwise, the number of bytes written to the queue is
+ * returned.  Updates the tail pointer of the produce queue.
+ */
+static ssize_t qp_enqueue_locked(struct vmci_queue *produce_q,
+				 struct vmci_queue *consume_q,
+				 const u64 produce_q_size,
+				 const void *buf,
+				 size_t buf_size,
+				 vmci_memcpy_to_queue_func memcpy_to_queue,
+				 bool can_block)
+{
+	s64 free_space;
+	u64 tail;
+	size_t written;
+	ssize_t result;
+
+	result = qp_map_queue_headers(produce_q, consume_q, can_block);
+	if (unlikely(result != VMCI_SUCCESS))
+		return result;
+
+	free_space = vmci_q_header_free_space(produce_q->q_header,
+					      consume_q->q_header,
+					      produce_q_size);
+	if (free_space == 0)
+		return VMCI_ERROR_QUEUEPAIR_NOSPACE;
+
+	if (free_space < VMCI_SUCCESS)
+		return (ssize_t) free_space;
+
+	written = (size_t) (free_space > buf_size ? buf_size : free_space);
+	tail = vmci_q_header_producer_tail(produce_q->q_header);
+	if (likely(tail + written < produce_q_size)) {
+		result = memcpy_to_queue(produce_q, tail, buf, 0, written);
+	} else {
+		/* Tail pointer wraps around. */
+
+		const size_t tmp = (size_t) (produce_q_size - tail);
+
+		result = memcpy_to_queue(produce_q, tail, buf, 0, tmp);
+		if (result >= VMCI_SUCCESS)
+			result = memcpy_to_queue(produce_q, 0, buf, tmp,
+						 written - tmp);
+	}
+
+	if (result < VMCI_SUCCESS)
+		return result;
+
+	vmci_q_header_add_producer_tail(produce_q->q_header, written,
+					produce_q_size);
+	return written;
+}
+
+/*
+ * Dequeues data (if available) from the given consume queue. Writes data
+ * to the user provided buffer using the provided function.
+ * Assumes the queue->mutex has been acquired.
+ * Results:
+ * VMCI_ERROR_QUEUEPAIR_NODATA if no data was available to dequeue.
+ * VMCI_ERROR_INVALID_SIZE, if any queue pointer is outside the queue
+ * (as defined by the queue size).
+ * VMCI_ERROR_INVALID_ARGS, if an error occured when accessing the buffer.
+ * Otherwise the number of bytes dequeued is returned.
+ * Side effects:
+ * Updates the head pointer of the consume queue.
+ */
+static ssize_t qp_dequeue_locked(struct vmci_queue *produce_q,
+				 struct vmci_queue *consume_q,
+				 const u64 consume_q_size,
+				 void *buf,
+				 size_t buf_size,
+				 vmci_memcpy_from_queue_func memcpy_from_queue,
+				 bool update_consumer,
+				 bool can_block)
+{
+	s64 buf_ready;
+	u64 head;
+	size_t read;
+	ssize_t result;
+
+	result = qp_map_queue_headers(produce_q, consume_q, can_block);
+	if (unlikely(result != VMCI_SUCCESS))
+		return result;
+
+	buf_ready = vmci_q_header_buf_ready(consume_q->q_header,
+					    produce_q->q_header,
+					    consume_q_size);
+	if (buf_ready == 0)
+		return VMCI_ERROR_QUEUEPAIR_NODATA;
+
+	if (buf_ready < VMCI_SUCCESS)
+		return (ssize_t) buf_ready;
+
+	read = (size_t) (buf_ready > buf_size ? buf_size : buf_ready);
+	head = vmci_q_header_consumer_head(produce_q->q_header);
+	if (likely(head + read < consume_q_size)) {
+		result = memcpy_from_queue(buf, 0, consume_q, head, read);
+	} else {
+		/* Head pointer wraps around. */
+
+		const size_t tmp = (size_t) (consume_q_size - head);
+
+		result = memcpy_from_queue(buf, 0, consume_q, head, tmp);
+		if (result >= VMCI_SUCCESS)
+			result = memcpy_from_queue(buf, tmp, consume_q, 0,
+						   read - tmp);
+
+	}
+
+	if (result < VMCI_SUCCESS)
+		return result;
+
+	if (update_consumer)
+		vmci_q_header_add_consumer_head(produce_q->q_header,
+						read, consume_q_size);
+
+	return read;
+}
+
+/*
+ * vmci_qpair_alloc() - Allocates a queue pair.
+ * @qpair:      Pointer for the new vmci_qp struct.
+ * @handle:     Handle to track the resource.
+ * @produce_qsize:      Desired size of the producer queue.
+ * @consume_qsize:      Desired size of the consumer queue.
+ * @peer:       ContextID of the peer.
+ * @flags:      VMCI flags.
+ * @priv_flags: VMCI priviledge flags.
+ *
+ * This is the client interface for allocating the memory for a
+ * vmci_qp structure and then attaching to the underlying
+ * queue.  If an error occurs allocating the memory for the
+ * vmci_qp structure no attempt is made to attach.  If an
+ * error occurs attaching, then the structure is freed.
+ */
+int vmci_qpair_alloc(struct vmci_qp **qpair,
+		     struct vmci_handle *handle,
+		     u64 produce_qsize,
+		     u64 consume_qsize,
+		     u32 peer,
+		     u32 flags,
+		     u32 priv_flags)
+{
+	struct vmci_qp *my_qpair;
+	int retval;
+	struct vmci_handle src = VMCI_INVALID_HANDLE;
+	struct vmci_handle dst = vmci_make_handle(peer, VMCI_INVALID_ID);
+	enum vmci_route route;
+	vmci_event_release_cb wakeup_cb;
+	void *client_data;
+
+	/*
+	 * Restrict the size of a queuepair.  The device already
+	 * enforces a limit on the total amount of memory that can be
+	 * allocated to queuepairs for a guest.  However, we try to
+	 * allocate this memory before we make the queuepair
+	 * allocation hypercall.  On Linux, we allocate each page
+	 * separately, which means rather than fail, the guest will
+	 * thrash while it tries to allocate, and will become
+	 * increasingly unresponsive to the point where it appears to
+	 * be hung.  So we place a limit on the size of an individual
+	 * queuepair here, and leave the device to enforce the
+	 * restriction on total queuepair memory.  (Note that this
+	 * doesn't prevent all cases; a user with only this much
+	 * physical memory could still get into trouble.)  The error
+	 * used by the device is NO_RESOURCES, so use that here too.
+	 */
+
+	if (produce_qsize + consume_qsize < max(produce_qsize, consume_qsize) ||
+	    produce_qsize + consume_qsize > VMCI_MAX_GUEST_QP_MEMORY)
+		return VMCI_ERROR_NO_RESOURCES;
+
+	retval = vmci_route(&src, &dst, false, &route);
+	if (retval < VMCI_SUCCESS)
+		route = vmci_guest_code_active() ?
+		    VMCI_ROUTE_AS_GUEST : VMCI_ROUTE_AS_HOST;
+
+	/* If NONBLOCK or PINNED is set, we better be the guest personality. */
+	if ((!vmci_can_block(flags) || vmci_qp_pinned(flags)) &&
+	    VMCI_ROUTE_AS_GUEST != route) {
+		pr_devel("Not guest personality w/ NONBLOCK OR PINNED set");
+		return VMCI_ERROR_INVALID_ARGS;
+	}
+
+	/*
+	 * Limit the size of pinned QPs and check sanity.
+	 *
+	 * Pinned pages implies non-blocking mode.  Mutexes aren't acquired
+	 * when the NONBLOCK flag is set in qpair code; and also should not be
+	 * acquired when the PINNED flagged is set.  Since pinning pages
+	 * implies we want speed, it makes no sense not to have NONBLOCK
+	 * set if PINNED is set.  Hence enforce this implication.
+	 */
+	if (vmci_qp_pinned(flags)) {
+		if (vmci_can_block(flags)) {
+			pr_err("Attempted to enable pinning w/o non-blocking");
+			return VMCI_ERROR_INVALID_ARGS;
+		}
+
+		if (produce_qsize + consume_qsize > VMCI_MAX_PINNED_QP_MEMORY)
+			return VMCI_ERROR_NO_RESOURCES;
+	}
+
+	my_qpair = kzalloc(sizeof(*my_qpair), GFP_KERNEL);
+	if (!my_qpair)
+		return VMCI_ERROR_NO_MEM;
+
+	my_qpair->produce_q_size = produce_qsize;
+	my_qpair->consume_q_size = consume_qsize;
+	my_qpair->peer = peer;
+	my_qpair->flags = flags;
+	my_qpair->priv_flags = priv_flags;
+
+	wakeup_cb = NULL;
+	client_data = NULL;
+
+	if (VMCI_ROUTE_AS_HOST == route) {
+		my_qpair->guest_endpoint = false;
+		if (!(flags & VMCI_QPFLAG_LOCAL)) {
+			my_qpair->blocked = 0;
+			my_qpair->generation = 0;
+			init_waitqueue_head(&my_qpair->event);
+			wakeup_cb = qp_wakeup_cb;
+			client_data = (void *)my_qpair;
+		}
+	} else {
+		my_qpair->guest_endpoint = true;
+	}
+
+	retval = vmci_qp_alloc(handle,
+			       &my_qpair->produce_q,
+			       my_qpair->produce_q_size,
+			       &my_qpair->consume_q,
+			       my_qpair->consume_q_size,
+			       my_qpair->peer,
+			       my_qpair->flags,
+			       my_qpair->priv_flags,
+			       my_qpair->guest_endpoint,
+			       wakeup_cb, client_data);
+
+	if (retval < VMCI_SUCCESS) {
+		kfree(my_qpair);
+		return retval;
+	}
+
+	*qpair = my_qpair;
+	my_qpair->handle = *handle;
+
+	return retval;
+}
+EXPORT_SYMBOL_GPL(vmci_qpair_alloc);
+
+/*
+ * vmci_qpair_detach() - Detatches the client from a queue pair.
+ * @qpair:      Reference of a pointer to the qpair struct.
+ *
+ * This is the client interface for detaching from a VMCIQPair.
+ * Note that this routine will free the memory allocated for the
+ * vmci_qp structure too.
+ */
+int vmci_qpair_detach(struct vmci_qp **qpair)
+{
+	int result;
+	struct vmci_qp *old_qpair;
+
+	if (!qpair || !(*qpair))
+		return VMCI_ERROR_INVALID_ARGS;
+
+	old_qpair = *qpair;
+	result = qp_detatch(old_qpair->handle, old_qpair->guest_endpoint);
+
+	/*
+	 * The guest can fail to detach for a number of reasons, and
+	 * if it does so, it will cleanup the entry (if there is one).
+	 * The host can fail too, but it won't cleanup the entry
+	 * immediately, it will do that later when the context is
+	 * freed.  Either way, we need to release the qpair struct
+	 * here; there isn't much the caller can do, and we don't want
+	 * to leak.
+	 */
+
+	memset(old_qpair, 0, sizeof(*old_qpair));
+	old_qpair->handle = VMCI_INVALID_HANDLE;
+	old_qpair->peer = VMCI_INVALID_ID;
+	kfree(old_qpair);
+	*qpair = NULL;
+
+	return result;
+}
+EXPORT_SYMBOL_GPL(vmci_qpair_detach);
+
+/*
+ * vmci_qpair_get_produce_indexes() - Retrieves the indexes of the producer.
+ * @qpair:      Pointer to the queue pair struct.
+ * @producer_tail:      Reference used for storing producer tail index.
+ * @consumer_head:      Reference used for storing the consumer head index.
+ *
+ * This is the client interface for getting the current indexes of the
+ * QPair from the point of the view of the caller as the producer.
+ */
+int vmci_qpair_get_produce_indexes(const struct vmci_qp *qpair,
+				   u64 *producer_tail,
+				   u64 *consumer_head)
+{
+	struct vmci_queue_header *produce_q_header;
+	struct vmci_queue_header *consume_q_header;
+	int result;
+
+	if (!qpair)
+		return VMCI_ERROR_INVALID_ARGS;
+
+	qp_lock(qpair);
+	result =
+	    qp_get_queue_headers(qpair, &produce_q_header, &consume_q_header);
+	if (result == VMCI_SUCCESS)
+		vmci_q_header_get_pointers(produce_q_header, consume_q_header,
+					   producer_tail, consumer_head);
+	qp_unlock(qpair);
+
+	if (result == VMCI_SUCCESS &&
+	    ((producer_tail && *producer_tail >= qpair->produce_q_size) ||
+	     (consumer_head && *consumer_head >= qpair->produce_q_size)))
+		return VMCI_ERROR_INVALID_SIZE;
+
+	return result;
+}
+EXPORT_SYMBOL_GPL(vmci_qpair_get_produce_indexes);
+
+/*
+ * vmci_qpair_get_consume_indexes() - Retrieves the indexes of the comsumer.
+ * @qpair:      Pointer to the queue pair struct.
+ * @consumer_tail:      Reference used for storing consumer tail index.
+ * @producer_head:      Reference used for storing the producer head index.
+ *
+ * This is the client interface for getting the current indexes of the
+ * QPair from the point of the view of the caller as the consumer.
+ */
+int vmci_qpair_get_consume_indexes(const struct vmci_qp *qpair,
+				   u64 *consumer_tail,
+				   u64 *producer_head)
+{
+	struct vmci_queue_header *produce_q_header;
+	struct vmci_queue_header *consume_q_header;
+	int result;
+
+	if (!qpair)
+		return VMCI_ERROR_INVALID_ARGS;
+
+	qp_lock(qpair);
+	result =
+	    qp_get_queue_headers(qpair, &produce_q_header, &consume_q_header);
+	if (result == VMCI_SUCCESS)
+		vmci_q_header_get_pointers(consume_q_header, produce_q_header,
+					   consumer_tail, producer_head);
+	qp_unlock(qpair);
+
+	if (result == VMCI_SUCCESS &&
+	    ((consumer_tail && *consumer_tail >= qpair->consume_q_size) ||
+	     (producer_head && *producer_head >= qpair->consume_q_size)))
+		return VMCI_ERROR_INVALID_SIZE;
+
+	return result;
+}
+EXPORT_SYMBOL_GPL(vmci_qpair_get_consume_indexes);
+
+/*
+ * vmci_qpair_produce_free_space() - Retrieves free space in producer queue.
+ * @qpair:      Pointer to the queue pair struct.
+ *
+ * This is the client interface for getting the amount of free
+ * space in the QPair from the point of the view of the caller as
+ * the producer which is the common case.  Returns < 0 if err, else
+ * available bytes into which data can be enqueued if > 0.
+ */
+s64 vmci_qpair_produce_free_space(const struct vmci_qp *qpair)
+{
+	struct vmci_queue_header *produce_q_header;
+	struct vmci_queue_header *consume_q_header;
+	s64 result;
+
+	if (!qpair)
+		return VMCI_ERROR_INVALID_ARGS;
+
+	qp_lock(qpair);
+	result =
+	    qp_get_queue_headers(qpair, &produce_q_header, &consume_q_header);
+	if (result == VMCI_SUCCESS)
+		result = vmci_q_header_free_space(produce_q_header,
+						  consume_q_header,
+						  qpair->produce_q_size);
+	else
+		result = 0;
+
+	qp_unlock(qpair);
+
+	return result;
+}
+EXPORT_SYMBOL_GPL(vmci_qpair_produce_free_space);
+
+/*
+ * vmci_qpair_consume_free_space() - Retrieves free space in consumer queue.
+ * @qpair:      Pointer to the queue pair struct.
+ *
+ * This is the client interface for getting the amount of free
+ * space in the QPair from the point of the view of the caller as
+ * the consumer which is not the common case.  Returns < 0 if err, else
+ * available bytes into which data can be enqueued if > 0.
+ */
+s64 vmci_qpair_consume_free_space(const struct vmci_qp *qpair)
+{
+	struct vmci_queue_header *produce_q_header;
+	struct vmci_queue_header *consume_q_header;
+	s64 result;
+
+	if (!qpair)
+		return VMCI_ERROR_INVALID_ARGS;
+
+	qp_lock(qpair);
+	result =
+	    qp_get_queue_headers(qpair, &produce_q_header, &consume_q_header);
+	if (result == VMCI_SUCCESS)
+		result = vmci_q_header_free_space(consume_q_header,
+						  produce_q_header,
+						  qpair->consume_q_size);
+	else
+		result = 0;
+
+	qp_unlock(qpair);
+
+	return result;
+}
+EXPORT_SYMBOL_GPL(vmci_qpair_consume_free_space);
+
+/*
+ * vmci_qpair_produce_buf_ready() - Gets bytes ready to read from
+ * producer queue.
+ * @qpair:      Pointer to the queue pair struct.
+ *
+ * This is the client interface for getting the amount of
+ * enqueued data in the QPair from the point of the view of the
+ * caller as the producer which is not the common case.  Returns < 0 if err,
+ * else available bytes that may be read.
+ */
+s64 vmci_qpair_produce_buf_ready(const struct vmci_qp *qpair)
+{
+	struct vmci_queue_header *produce_q_header;
+	struct vmci_queue_header *consume_q_header;
+	s64 result;
+
+	if (!qpair)
+		return VMCI_ERROR_INVALID_ARGS;
+
+	qp_lock(qpair);
+	result =
+	    qp_get_queue_headers(qpair, &produce_q_header, &consume_q_header);
+	if (result == VMCI_SUCCESS)
+		result = vmci_q_header_buf_ready(produce_q_header,
+						 consume_q_header,
+						 qpair->produce_q_size);
+	else
+		result = 0;
+
+	qp_unlock(qpair);
+
+	return result;
+}
+EXPORT_SYMBOL_GPL(vmci_qpair_produce_buf_ready);
+
+/*
+ * vmci_qpair_consume_buf_ready() - Gets bytes ready to read from
+ * consumer queue.
+ * @qpair:      Pointer to the queue pair struct.
+ *
+ * This is the client interface for getting the amount of
+ * enqueued data in the QPair from the point of the view of the
+ * caller as the consumer which is the normal case.  Returns < 0 if err,
+ * else available bytes that may be read.
+ */
+s64 vmci_qpair_consume_buf_ready(const struct vmci_qp *qpair)
+{
+	struct vmci_queue_header *produce_q_header;
+	struct vmci_queue_header *consume_q_header;
+	s64 result;
+
+	if (!qpair)
+		return VMCI_ERROR_INVALID_ARGS;
+
+	qp_lock(qpair);
+	result =
+	    qp_get_queue_headers(qpair, &produce_q_header, &consume_q_header);
+	if (result == VMCI_SUCCESS)
+		result = vmci_q_header_buf_ready(consume_q_header,
+						 produce_q_header,
+						 qpair->consume_q_size);
+	else
+		result = 0;
+
+	qp_unlock(qpair);
+
+	return result;
+}
+EXPORT_SYMBOL_GPL(vmci_qpair_consume_buf_ready);
+
+/*
+ * vmci_qpair_enqueue() - Throw data on the queue.
+ * @qpair:      Pointer to the queue pair struct.
+ * @buf:        Pointer to buffer containing data
+ * @buf_size:   Length of buffer.
+ * @buf_type:   Buffer type (Unused).
+ *
+ * This is the client interface for enqueueing data into the queue.
+ * Returns number of bytes enqueued or < 0 on error.
+ */
+ssize_t vmci_qpair_enqueue(struct vmci_qp *qpair,
+			   const void *buf,
+			   size_t buf_size,
+			   int buf_type)
+{
+	ssize_t result;
+
+	if (!qpair || !buf)
+		return VMCI_ERROR_INVALID_ARGS;
+
+	qp_lock(qpair);
+
+	do {
+		result = qp_enqueue_locked(qpair->produce_q,
+					   qpair->consume_q,
+					   qpair->produce_q_size,
+					   buf, buf_size,
+					   qp_memcpy_to_queue,
+					   vmci_can_block(qpair->flags));
+
+		if (result == VMCI_ERROR_QUEUEPAIR_NOT_READY &&
+		    !qp_wait_for_ready_queue(qpair))
+			result = VMCI_ERROR_WOULD_BLOCK;
+
+	} while (result == VMCI_ERROR_QUEUEPAIR_NOT_READY);
+
+	qp_unlock(qpair);
+
+	return result;
+}
+EXPORT_SYMBOL_GPL(vmci_qpair_enqueue);
+
+/*
+ * vmci_qpair_dequeue() - Get data from the queue.
+ * @qpair:      Pointer to the queue pair struct.
+ * @buf:        Pointer to buffer for the data
+ * @buf_size:   Length of buffer.
+ * @buf_type:   Buffer type (Unused).
+ *
+ * This is the client interface for dequeueing data from the queue.
+ * Returns number of bytes dequeued or < 0 on error.
+ */
+ssize_t vmci_qpair_dequeue(struct vmci_qp *qpair,
+			   void *buf,
+			   size_t buf_size,
+			   int buf_type)
+{
+	ssize_t result;
+
+	if (!qpair || !buf)
+		return VMCI_ERROR_INVALID_ARGS;
+
+	qp_lock(qpair);
+
+	do {
+		result = qp_dequeue_locked(qpair->produce_q,
+					   qpair->consume_q,
+					   qpair->consume_q_size,
+					   buf, buf_size,
+					   qp_memcpy_from_queue, true,
+					   vmci_can_block(qpair->flags));
+
+		if (result == VMCI_ERROR_QUEUEPAIR_NOT_READY &&
+		    !qp_wait_for_ready_queue(qpair))
+			result = VMCI_ERROR_WOULD_BLOCK;
+
+	} while (result == VMCI_ERROR_QUEUEPAIR_NOT_READY);
+
+	qp_unlock(qpair);
+
+	return result;
+}
+EXPORT_SYMBOL_GPL(vmci_qpair_dequeue);
+
+/*
+ * vmci_qpair_peek() - Peek at the data in the queue.
+ * @qpair:      Pointer to the queue pair struct.
+ * @buf:        Pointer to buffer for the data
+ * @buf_size:   Length of buffer.
+ * @buf_type:   Buffer type (Unused on Linux).
+ *
+ * This is the client interface for peeking into a queue.  (I.e.,
+ * copy data from the queue without updating the head pointer.)
+ * Returns number of bytes dequeued or < 0 on error.
+ */
+ssize_t vmci_qpair_peek(struct vmci_qp *qpair,
+			void *buf,
+			size_t buf_size,
+			int buf_type)
+{
+	ssize_t result;
+
+	if (!qpair || !buf)
+		return VMCI_ERROR_INVALID_ARGS;
+
+	qp_lock(qpair);
+
+	do {
+		result = qp_dequeue_locked(qpair->produce_q,
+					   qpair->consume_q,
+					   qpair->consume_q_size,
+					   buf, buf_size,
+					   qp_memcpy_from_queue, false,
+					   vmci_can_block(qpair->flags));
+
+		if (result == VMCI_ERROR_QUEUEPAIR_NOT_READY &&
+		    !qp_wait_for_ready_queue(qpair))
+			result = VMCI_ERROR_WOULD_BLOCK;
+
+	} while (result == VMCI_ERROR_QUEUEPAIR_NOT_READY);
+
+	qp_unlock(qpair);
+
+	return result;
+}
+EXPORT_SYMBOL_GPL(vmci_qpair_peek);
+
+/*
+ * vmci_qpair_enquev() - Throw data on the queue using iov.
+ * @qpair:      Pointer to the queue pair struct.
+ * @iov:        Pointer to buffer containing data
+ * @iov_size:   Length of buffer.
+ * @buf_type:   Buffer type (Unused).
+ *
+ * This is the client interface for enqueueing data into the queue.
+ * This function uses IO vectors to handle the work. Returns number
+ * of bytes enqueued or < 0 on error.
+ */
+ssize_t vmci_qpair_enquev(struct vmci_qp *qpair,
+			  void *iov,
+			  size_t iov_size,
+			  int buf_type)
+{
+	ssize_t result;
+
+	if (!qpair || !iov)
+		return VMCI_ERROR_INVALID_ARGS;
+
+	qp_lock(qpair);
+
+	do {
+		result = qp_enqueue_locked(qpair->produce_q,
+					   qpair->consume_q,
+					   qpair->produce_q_size,
+					   iov, iov_size,
+					   qp_memcpy_to_queue_iov,
+					   vmci_can_block(qpair->flags));
+
+		if (result == VMCI_ERROR_QUEUEPAIR_NOT_READY &&
+		    !qp_wait_for_ready_queue(qpair))
+			result = VMCI_ERROR_WOULD_BLOCK;
+
+	} while (result == VMCI_ERROR_QUEUEPAIR_NOT_READY);
+
+	qp_unlock(qpair);
+
+	return result;
+}
+EXPORT_SYMBOL_GPL(vmci_qpair_enquev);
+
+/*
+ * vmci_qpair_dequev() - Get data from the queue using iov.
+ * @qpair:      Pointer to the queue pair struct.
+ * @iov:        Pointer to buffer for the data
+ * @iov_size:   Length of buffer.
+ * @buf_type:   Buffer type (Unused).
+ *
+ * This is the client interface for dequeueing data from the queue.
+ * This function uses IO vectors to handle the work. Returns number
+ * of bytes dequeued or < 0 on error.
+ */
+ssize_t vmci_qpair_dequev(struct vmci_qp *qpair,
+			  void *iov,
+			  size_t iov_size,
+			  int buf_type)
+{
+	ssize_t result;
+
+	qp_lock(qpair);
+
+	if (!qpair || !iov)
+		return VMCI_ERROR_INVALID_ARGS;
+
+	do {
+		result = qp_dequeue_locked(qpair->produce_q,
+					   qpair->consume_q,
+					   qpair->consume_q_size,
+					   iov, iov_size,
+					   qp_memcpy_from_queue_iov,
+					   true, vmci_can_block(qpair->flags));
+
+		if (result == VMCI_ERROR_QUEUEPAIR_NOT_READY &&
+		    !qp_wait_for_ready_queue(qpair))
+			result = VMCI_ERROR_WOULD_BLOCK;
+
+	} while (result == VMCI_ERROR_QUEUEPAIR_NOT_READY);
+
+	qp_unlock(qpair);
+
+	return result;
+}
+EXPORT_SYMBOL_GPL(vmci_qpair_dequev);
+
+/*
+ * vmci_qpair_peekv() - Peek at the data in the queue using iov.
+ * @qpair:      Pointer to the queue pair struct.
+ * @iov:        Pointer to buffer for the data
+ * @iov_size:   Length of buffer.
+ * @buf_type:   Buffer type (Unused on Linux).
+ *
+ * This is the client interface for peeking into a queue.  (I.e.,
+ * copy data from the queue without updating the head pointer.)
+ * This function uses IO vectors to handle the work. Returns number
+ * of bytes peeked or < 0 on error.
+ */
+ssize_t vmci_qpair_peekv(struct vmci_qp *qpair,
+			 void *iov,
+			 size_t iov_size,
+			 int buf_type)
+{
+	ssize_t result;
+
+	if (!qpair || !iov)
+		return VMCI_ERROR_INVALID_ARGS;
+
+	qp_lock(qpair);
+
+	do {
+		result = qp_dequeue_locked(qpair->produce_q,
+					   qpair->consume_q,
+					   qpair->consume_q_size,
+					   iov, iov_size,
+					   qp_memcpy_from_queue_iov,
+					   false, vmci_can_block(qpair->flags));
+
+		if (result == VMCI_ERROR_QUEUEPAIR_NOT_READY &&
+		    !qp_wait_for_ready_queue(qpair))
+			result = VMCI_ERROR_WOULD_BLOCK;
+
+	} while (result == VMCI_ERROR_QUEUEPAIR_NOT_READY);
+
+	qp_unlock(qpair);
+	return result;
+}
+EXPORT_SYMBOL_GPL(vmci_qpair_peekv);
diff --git a/drivers/misc/vmw_vmci/vmci_queue_pair.h b/drivers/misc/vmw_vmci/vmci_queue_pair.h
new file mode 100644
index 0000000..8d8d6a1
--- /dev/null
+++ b/drivers/misc/vmw_vmci/vmci_queue_pair.h
@@ -0,0 +1,191 @@
+/*
+ * 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.
+ */
+
+#ifndef _VMCI_QUEUE_PAIR_H_
+#define _VMCI_QUEUE_PAIR_H_
+
+#include <linux/vmw_vmci_defs.h>
+#include <linux/types.h>
+
+#include "vmci_context.h"
+
+/* Callback needed for correctly waiting on events. */
+typedef int (*vmci_event_release_cb) (void *client_data);
+
+/* Guest device port I/O. */
+struct PPNSet {
+	u64 num_produce_pages;
+	u64 num_consume_pages;
+	u32 *produce_ppns;
+	u32 *consume_ppns;
+	bool initialized;
+};
+
+/* VMCIqueue_pairAllocInfo */
+struct vmci_qp_alloc_info {
+	struct vmci_handle handle;
+	u32 peer;
+	u32 flags;
+	u64 produce_size;
+	u64 consume_size;
+	u64 ppn_va;	/* Start VA of queue pair PPNs. */
+	u64 num_ppns;
+	s32 result;
+	u32 version;
+};
+
+/* VMCIqueue_pairSetVAInfo */
+struct vmci_qp_set_va_info {
+	struct vmci_handle handle;
+	u64 va;		/* Start VA of queue pair PPNs. */
+	u64 num_ppns;
+	u32 version;
+	s32 result;
+};
+
+/*
+ * For backwards compatibility, here is a version of the
+ * VMCIqueue_pairPageFileInfo before host support end-points was added.
+ * Note that the current version of that structure requires VMX to
+ * pass down the VA of the mapped file.  Before host support was added
+ * there was nothing of the sort.  So, when the driver sees the ioctl
+ * with a parameter that is the sizeof
+ * VMCIqueue_pairPageFileInfo_NoHostQP then it can infer that the version
+ * of VMX running can't attach to host end points because it doesn't
+ * provide the VA of the mapped files.
+ *
+ * The Linux driver doesn't get an indication of the size of the
+ * structure passed down from user space.  So, to fix a long standing
+ * but unfiled bug, the _pad field has been renamed to version.
+ * Existing versions of VMX always initialize the PageFileInfo
+ * structure so that _pad, er, version is set to 0.
+ *
+ * A version value of 1 indicates that the size of the structure has
+ * been increased to include two UVA's: produce_uva and consume_uva.
+ * These UVA's are of the mmap()'d queue contents backing files.
+ *
+ * In addition, if when VMX is sending down the
+ * VMCIqueue_pairPageFileInfo structure it gets an error then it will
+ * try again with the _NoHostQP version of the file to see if an older
+ * VMCI kernel module is running.
+ */
+
+/* VMCIqueue_pairPageFileInfo */
+struct vmci_qp_page_file_info {
+	struct vmci_handle handle;
+	u64 produce_page_file;	  /* User VA. */
+	u64 consume_page_file;	  /* User VA. */
+	u64 produce_page_file_size;  /* Size of the file name array. */
+	u64 consume_page_file_size;  /* Size of the file name array. */
+	s32 result;
+	u32 version;	/* Was _pad. */
+	u64 produce_va;	/* User VA of the mapped file. */
+	u64 consume_va;	/* User VA of the mapped file. */
+};
+
+/* vmci queuepair detach info */
+struct vmci_qp_dtch_info {
+	struct vmci_handle handle;
+	s32 result;
+	u32 _pad;
+};
+
+/*
+ * struct vmci_qp_page_store describes how the memory of a given queue pair
+ * is backed. When the queue pair is between the host and a guest, the
+ * page store consists of references to the guest pages. On vmkernel,
+ * this is a list of PPNs, and on hosted, it is a user VA where the
+ * queue pair is mapped into the VMX address space.
+ */
+struct vmci_qp_page_store {
+	/* Reference to pages backing the queue pair. */
+	u64 pages;
+	/* Length of pageList/virtual addres range (in pages). */
+	u32 len;
+};
+
+/*
+ * This data type contains the information about a queue.
+ * There are two queues (hence, queue pairs) per transaction model between a
+ * pair of end points, A & B.  One queue is used by end point A to transmit
+ * commands and responses to B.  The other queue is used by B to transmit
+ * commands and responses.
+ *
+ * struct vmci_queue_kern_if is a per-OS defined Queue structure.  It contains
+ * either a direct pointer to the linear address of the buffer contents or a
+ * pointer to structures which help the OS locate those data pages.  See
+ * vmciKernelIf.c for each platform for its definition.
+ */
+struct vmci_queue {
+	struct vmci_queue_header *q_header;
+	struct vmci_queue_header *saved_header;
+	struct vmci_queue_kern_if *kernel_if;
+};
+
+/*
+ * Utility function that checks whether the fields of the page
+ * store contain valid values.
+ * Result:
+ * true if the page store is wellformed. false otherwise.
+ */
+static inline bool
+VMCI_QP_PAGESTORE_IS_WELLFORMED(struct vmci_qp_page_store *page_store)
+{
+	return page_store->len >= 2;
+}
+
+/*
+ * Helper function to check if the non-blocking flag
+ * is set for a given queue pair.
+ */
+static inline bool vmci_can_block(u32 flags)
+{
+	return !(flags & VMCI_QPFLAG_NONBLOCK);
+}
+
+/*
+ * Helper function to check if the queue pair is pinned
+ * into memory.
+ */
+static inline bool vmci_qp_pinned(u32 flags)
+{
+	return flags & VMCI_QPFLAG_PINNED;
+}
+
+void vmci_qp_broker_exit(void);
+int vmci_qp_broker_alloc(struct vmci_handle handle, u32 peer,
+			 u32 flags, u32 priv_flags,
+			 u64 produce_size, u64 consume_size,
+			 struct vmci_qp_page_store *page_store,
+			 struct vmci_ctx *context);
+int vmci_qp_broker_set_page_store(struct vmci_handle handle,
+				  u64 produce_uva, u64 consume_uva,
+				  struct vmci_ctx *context);
+int vmci_qp_broker_detach(struct vmci_handle handle, struct vmci_ctx *context);
+
+void vmci_qp_guest_endpoints_exit(void);
+
+int vmci_qp_alloc(struct vmci_handle *handle,
+		  struct vmci_queue **produce_q, u64 produce_size,
+		  struct vmci_queue **consume_q, u64 consume_size,
+		  u32 peer, u32 flags, u32 priv_flags,
+		  bool guest_endpoint, vmci_event_release_cb wakeup_cb,
+		  void *client_data);
+int vmci_qp_broker_map(struct vmci_handle handle,
+		       struct vmci_ctx *context, u64 guest_mem);
+int vmci_qp_broker_unmap(struct vmci_handle handle,
+			 struct vmci_ctx *context, u32 gid);
+
+#endif /* _VMCI_QUEUE_PAIR_H_ */