Date:	Wed, 21 Nov 2012 12:32:42 -0800
From:	George Zhang <georgezhang@...are.com>
To:	linux-kernel@...r.kernel.org, georgezhang@...are.com,
	virtualization@...ts.linux-foundation.org
Cc:	pv-drivers@...are.com, gregkh@...uxfoundation.org
Subject: [PATCH 03/12] VMCI: doorbell implementation.

VMCI doorbell code allows for notifcations between host and guest.

Signed-off-by: George Zhang <georgezhang@...are.com>
Signed-off-by: Dmitry Torokhov <dtor@...are.com>
Signed-off-by: Andy King <acking@...are.com>

---
 drivers/misc/vmw_vmci/vmci_doorbell.c |  605 +++++++++++++++++++++++++++++++++
 drivers/misc/vmw_vmci/vmci_doorbell.h |   51 +++
 2 files changed, 656 insertions(+), 0 deletions(-)
 create mode 100644 drivers/misc/vmw_vmci/vmci_doorbell.c
 create mode 100644 drivers/misc/vmw_vmci/vmci_doorbell.h

diff --git a/drivers/misc/vmw_vmci/vmci_doorbell.c b/drivers/misc/vmw_vmci/vmci_doorbell.c
new file mode 100644
index 0000000..bced12b
--- /dev/null
+++ b/drivers/misc/vmw_vmci/vmci_doorbell.c
@@ -0,0 +1,605 @@
+/*
+ * VMware VMCI Driver
+ *
+ * Copyright (C) 2012 VMware, Inc. All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the
+ * Free Software Foundation version 2 and no later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+ * or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * for more details.
+ */
+
+#include <linux/vmw_vmci_defs.h>
+#include <linux/vmw_vmci_api.h>
+#include <linux/completion.h>
+#include <linux/hash.h>
+#include <linux/kernel.h>
+#include <linux/list.h>
+#include <linux/module.h>
+#include <linux/sched.h>
+#include <linux/slab.h>
+
+#include "vmci_common_int.h"
+#include "vmci_datagram.h"
+#include "vmci_doorbell.h"
+#include "vmci_resource.h"
+#include "vmci_driver.h"
+#include "vmci_route.h"
+
+
+#define VMCI_DOORBELL_INDEX_BITS	6
+#define VMCI_DOORBELL_INDEX_TABLE_SIZE	(1 << VMCI_DOORBELL_INDEX_BITS)
+#define VMCI_DOORBELL_HASH(_idx)	hash_32(_idx, VMCI_DOORBELL_INDEX_BITS)
+
+/*
+ * DoorbellEntry describes the a doorbell notification handle allocated by the
+ * host.
+ */
+struct dbell_entry {
+	struct vmci_resource resource;
+	struct hlist_node node;
+	struct work_struct work;
+	vmci_callback notify_cb;
+	void *client_data;
+	u32 idx;
+	u32 priv_flags;
+	bool run_delayed;
+	atomic_t active;	/* Only used by guest personality */
+};
+
+/* The VMCI index table keeps track of currently registered doorbells. */
+struct dbell_index_table {
+	spinlock_t lock;	/* Index table lock */
+	struct hlist_head entries[VMCI_DOORBELL_INDEX_TABLE_SIZE];
+};
+
+static struct dbell_index_table vmci_doorbell_it = {
+	.lock = __SPIN_LOCK_UNLOCKED(vmci_doorbell_it.lock),
+};
+
+/*
+ * The max_notify_idx is one larger than the currently known bitmap index in
+ * use, and is used to determine how much of the bitmap needs to be scanned.
+ */
+static u32 max_notify_idx;
+
+/*
+ * The notify_idx_count is used for determining whether there are free entries
+ * within the bitmap (if notify_idx_count + 1 < max_notify_idx).
+ */
+static u32 notify_idx_count;
+
+/*
+ * The last_notify_idx_reserved is used to track the last index handed out - in
+ * the case where multiple handles share a notification index, we hand out
+ * indexes round robin based on last_notify_idx_reserved.
+ */
+static u32 last_notify_idx_reserved;
+
+/* This is a one entry cache used to by the index allocation. */
+static u32 last_notify_idx_released = PAGE_SIZE;
+
+
+/*
+ * Utility function that retrieves the privilege flags associated
+ * with a given doorbell handle. For guest endpoints, the
+ * privileges are determined by the context ID, but for host
+ * endpoints privileges are associated with the complete
+ * handle. Hypervisor endpoints are not yet supported.
+ */
+int vmci_dbell_get_priv_flags(struct vmci_handle handle, u32 *priv_flags)
+{
+	if (priv_flags == NULL || handle.context == VMCI_INVALID_ID)
+		return VMCI_ERROR_INVALID_ARGS;
+
+	if (handle.context == VMCI_HOST_CONTEXT_ID) {
+		struct dbell_entry *entry;
+		struct vmci_resource *resource;
+
+		resource = vmci_resource_by_handle(handle,
+						   VMCI_RESOURCE_TYPE_DOORBELL);
+		if (!resource)
+			return VMCI_ERROR_NOT_FOUND;
+
+		entry = container_of(resource, struct dbell_entry, resource);
+		*priv_flags = entry->priv_flags;
+		vmci_resource_put(resource);
+	} else if (handle.context == VMCI_HYPERVISOR_CONTEXT_ID) {
+		/*
+		 * Hypervisor endpoints for notifications are not
+		 * supported (yet).
+		 */
+		return VMCI_ERROR_INVALID_ARGS;
+	} else {
+		*priv_flags = vmci_context_get_priv_flags(handle.context);
+	}
+
+	return VMCI_SUCCESS;
+}
+
+/*
+ * Find doorbell entry by bitmap index.
+ */
+static struct dbell_entry *dbell_index_table_find(u32 idx)
+{
+	u32 bucket = VMCI_DOORBELL_HASH(idx);
+	struct dbell_entry *dbell;
+	struct hlist_node *node;
+
+	hlist_for_each_entry(dbell, node, &vmci_doorbell_it.entries[bucket],
+			     node) {
+		if (idx == dbell->idx)
+			return dbell;
+	}
+
+	return NULL;
+}
+
+/*
+ * Add the given entry to the index table.  This willi take a reference to the
+ * entry's resource so that the entry is not deleted before it is removed from
+ * the * table.
+ */
+static void dbell_index_table_add(struct dbell_entry *entry)
+{
+	u32 bucket;
+	u32 new_notify_idx;
+
+	vmci_resource_get(&entry->resource);
+
+	spin_lock_bh(&vmci_doorbell_it.lock);
+
+	/*
+	 * Below we try to allocate an index in the notification
+	 * bitmap with "not too much" sharing between resources. If we
+	 * use less that the full bitmap, we either add to the end if
+	 * there are no unused flags within the currently used area,
+	 * or we search for unused ones. If we use the full bitmap, we
+	 * allocate the index round robin.
+	 */
+	if (max_notify_idx < PAGE_SIZE || notify_idx_count < PAGE_SIZE) {
+		if (last_notify_idx_released < max_notify_idx &&
+		    !dbell_index_table_find(last_notify_idx_released)) {
+			new_notify_idx = last_notify_idx_released;
+			last_notify_idx_released = PAGE_SIZE;
+		} else {
+			bool reused = false;
+			new_notify_idx = last_notify_idx_reserved;
+			if (notify_idx_count + 1 < max_notify_idx) {
+				do {
+					if (!dbell_index_table_find
+					    (new_notify_idx)) {
+						reused = true;
+						break;
+					}
+					new_notify_idx = (new_notify_idx + 1) %
+					    max_notify_idx;
+				} while (new_notify_idx !=
+					 last_notify_idx_released);
+			}
+			if (!reused) {
+				new_notify_idx = max_notify_idx;
+				max_notify_idx++;
+			}
+		}
+	} else {
+		new_notify_idx = (last_notify_idx_reserved + 1) % PAGE_SIZE;
+	}
+
+	last_notify_idx_reserved = new_notify_idx;
+	notify_idx_count++;
+
+	entry->idx = new_notify_idx;
+	bucket = VMCI_DOORBELL_HASH(entry->idx);
+	hlist_add_head(&entry->node, &vmci_doorbell_it.entries[bucket]);
+
+	spin_unlock_bh(&vmci_doorbell_it.lock);
+}
+
+/*
+ * Remove the given entry from the index table.  This will release() the
+ * entry's resource.
+ */
+static void dbell_index_table_remove(struct dbell_entry *entry)
+{
+	spin_lock_bh(&vmci_doorbell_it.lock);
+
+	hlist_del_init(&entry->node);
+
+	notify_idx_count--;
+	if (entry->idx == max_notify_idx - 1) {
+		/*
+		 * If we delete an entry with the maximum known
+		 * notification index, we take the opportunity to
+		 * prune the current max. As there might be other
+		 * unused indices immediately below, we lower the
+		 * maximum until we hit an index in use.
+		 */
+		while (max_notify_idx > 0 &&
+		       !dbell_index_table_find(max_notify_idx - 1))
+			max_notify_idx--;
+	}
+
+	last_notify_idx_released = entry->idx;
+
+	spin_unlock_bh(&vmci_doorbell_it.lock);
+
+	vmci_resource_put(&entry->resource);
+}
+
+/*
+ * Creates a link between the given doorbell handle and the given
+ * index in the bitmap in the device backend. A notification state
+ * is created in hypervisor.
+ */
+static int dbell_link(struct vmci_handle handle, u32 notify_idx)
+{
+	struct vmci_doorbell_link_msg link_msg;
+
+	link_msg.hdr.dst = vmci_make_handle(VMCI_HYPERVISOR_CONTEXT_ID,
+					    VMCI_DOORBELL_LINK);
+	link_msg.hdr.src = VMCI_ANON_SRC_HANDLE;
+	link_msg.hdr.payload_size = sizeof(link_msg) - VMCI_DG_HEADERSIZE;
+	link_msg.handle = handle;
+	link_msg.notify_idx = notify_idx;
+
+	return vmci_send_datagram(&link_msg.hdr);
+}
+
+/*
+ * Unlinks the given doorbell handle from an index in the bitmap in
+ * the device backend. The notification state is destroyed in hypervisor.
+ */
+static int dbell_unlink(struct vmci_handle handle)
+{
+	struct vmci_doorbell_unlink_msg unlink_msg;
+
+	unlink_msg.hdr.dst = vmci_make_handle(VMCI_HYPERVISOR_CONTEXT_ID,
+					      VMCI_DOORBELL_UNLINK);
+	unlink_msg.hdr.src = VMCI_ANON_SRC_HANDLE;
+	unlink_msg.hdr.payload_size = sizeof(unlink_msg) - VMCI_DG_HEADERSIZE;
+	unlink_msg.handle = handle;
+
+	return vmci_send_datagram(&unlink_msg.hdr);
+}
+
+/*
+ * Notify another guest or the host.  We send a datagram down to the
+ * host via the hypervisor with the notification info.
+ */
+static int dbell_notify_as_guest(struct vmci_handle handle, u32 priv_flags)
+{
+	struct vmci_doorbell_notify_msg notify_msg;
+
+	notify_msg.hdr.dst = vmci_make_handle(VMCI_HYPERVISOR_CONTEXT_ID,
+					      VMCI_DOORBELL_NOTIFY);
+	notify_msg.hdr.src = VMCI_ANON_SRC_HANDLE;
+	notify_msg.hdr.payload_size = sizeof(notify_msg) - VMCI_DG_HEADERSIZE;
+	notify_msg.handle = handle;
+
+	return vmci_send_datagram(&notify_msg.hdr);
+}
+
+/*
+ * Calls the specified callback in a delayed context.
+ */
+static void dbell_delayed_dispatch(struct work_struct *work)
+{
+	struct dbell_entry *entry = container_of(work,
+						 struct dbell_entry, work);
+
+	entry->notify_cb(entry->client_data);
+	vmci_resource_put(&entry->resource);
+}
+
+/*
+ * Dispatches a doorbell notification to the host context.
+ */
+int vmci_dbell_host_context_notify(u32 src_cid, struct vmci_handle handle)
+{
+	struct dbell_entry *entry;
+	struct vmci_resource *resource;
+
+	if (VMCI_HANDLE_INVALID(handle)) {
+		pr_devel("Notifying an invalid doorbell (handle=0x%x:0x%x).\n",
+			 handle.context, handle.resource);
+		return VMCI_ERROR_INVALID_ARGS;
+	}
+
+	resource = vmci_resource_by_handle(handle,
+					   VMCI_RESOURCE_TYPE_DOORBELL);
+	if (!resource) {
+		pr_devel("Notifying an unknown doorbell (handle=0x%x:0x%x).\n",
+			 handle.context, handle.resource);
+		return VMCI_ERROR_NOT_FOUND;
+	}
+
+	entry = container_of(resource, struct dbell_entry, resource);
+	if (entry->run_delayed) {
+		schedule_work(&entry->work);
+	} else {
+		entry->notify_cb(entry->client_data);
+		vmci_resource_put(resource);
+	}
+
+	return VMCI_SUCCESS;
+}
+
+/*
+ * Register the notification bitmap with the host.
+ */
+bool vmci_dbell_register_notification_bitmap(u32 bitmap_ppn)
+{
+	int result;
+	struct vmci_notify_bm_set_msg bitmap_set_msg;
+
+	bitmap_set_msg.hdr.dst = vmci_make_handle(VMCI_HYPERVISOR_CONTEXT_ID,
+						  VMCI_SET_NOTIFY_BITMAP);
+	bitmap_set_msg.hdr.src = VMCI_ANON_SRC_HANDLE;
+	bitmap_set_msg.hdr.payload_size = sizeof(bitmap_set_msg) -
+	    VMCI_DG_HEADERSIZE;
+	bitmap_set_msg.bitmap_ppn = bitmap_ppn;
+
+	result = vmci_send_datagram(&bitmap_set_msg.hdr);
+	if (result != VMCI_SUCCESS) {
+		pr_devel("Failed to register (PPN=%u) as notification bitmap (error=%d).\n",
+			 bitmap_ppn, result);
+		return false;
+	}
+	return true;
+}
+
+/*
+ * Executes or schedules the handlers for a given notify index.
+ */
+static void dbell_fire_entries(u32 notify_idx)
+{
+	u32 bucket = VMCI_DOORBELL_HASH(notify_idx);
+	struct dbell_entry *dbell;
+	struct hlist_node *node;
+
+	spin_lock_bh(&vmci_doorbell_it.lock);
+
+	hlist_for_each_entry(dbell, node,
+			     &vmci_doorbell_it.entries[bucket], node) {
+		if (dbell->idx == notify_idx &&
+		    atomic_read(&dbell->active) == 1) {
+			if (dbell->run_delayed) {
+				vmci_resource_get(&dbell->resource);
+				schedule_work(&dbell->work);
+			} else {
+				dbell->notify_cb(dbell->client_data);
+			}
+		}
+	}
+
+	spin_unlock_bh(&vmci_doorbell_it.lock);
+}
+
+/*
+ * Scans the notification bitmap, collects pending notifications,
+ * resets the bitmap and invokes appropriate callbacks.
+ */
+void vmci_dbell_scan_notification_entries(u8 *bitmap)
+{
+	u32 idx;
+
+	for (idx = 0; idx < max_notify_idx; idx++) {
+		if (bitmap[idx] & 0x1) {
+			bitmap[idx] &= ~1;
+			dbell_fire_entries(idx);
+		}
+	}
+}
+
+/*
+ * vmci_doorbell_create() - Creates a doorbell
+ * @handle:     A handle used to track the resource.  Can be invalid.
+ * @flags:      Flag that determines context of callback.
+ * @priv_flags: Privileges flags.
+ * @notify_cb:  The callback to be ivoked when the doorbell fires.
+ * @client_data:        A parameter to be passed to the callback.
+ *
+ * Creates a doorbell with the given callback. If the handle is
+ * VMCI_INVALID_HANDLE, a free handle will be assigned, if
+ * possible. The callback can be run immediately (potentially with
+ * locks held - the default) or delayed (in a kernel thread) by
+ * specifying the flag VMCI_FLAG_DELAYED_CB. If delayed execution
+ * is selected, a given callback may not be run if the kernel is
+ * unable to allocate memory for the delayed execution (highly
+ * unlikely).
+ */
+int vmci_doorbell_create(struct vmci_handle *handle,
+			 u32 flags,
+			 u32 priv_flags,
+			 vmci_callback notify_cb, void *client_data)
+{
+	struct dbell_entry *entry;
+	struct vmci_handle new_handle;
+	int result;
+
+	if (!handle || !notify_cb || flags & ~VMCI_FLAG_DELAYED_CB ||
+	    priv_flags & ~VMCI_PRIVILEGE_ALL_FLAGS)
+		return VMCI_ERROR_INVALID_ARGS;
+
+	entry = kmalloc(sizeof(*entry), GFP_KERNEL);
+	if (entry == NULL) {
+		pr_warn("Failed allocating memory for datagram entry.\n");
+		return VMCI_ERROR_NO_MEM;
+	}
+
+	if (VMCI_HANDLE_INVALID(*handle)) {
+		u32 context_id = vmci_get_context_id();
+
+		/* Let resource code allocate a free ID for us */
+		new_handle = vmci_make_handle(context_id, VMCI_INVALID_ID);
+	} else {
+		bool valid_context = false;
+
+		/*
+		 * Validate the handle.  We must do both of the checks below
+		 * because we can be acting as both a host and a guest at the
+		 * same time. We always allow the host context ID, since the
+		 * host functionality is in practice always there with the
+		 * unified driver.
+		 */
+		if (handle->context == VMCI_HOST_CONTEXT_ID ||
+		    (vmci_guest_code_active() &&
+		     vmci_get_context_id() == handle->context)) {
+			valid_context = true;
+		}
+
+		if (!valid_context || handle->resource == VMCI_INVALID_ID) {
+			pr_devel("Invalid argument (handle=0x%x:0x%x).\n",
+				 handle->context, handle->resource);
+			result = VMCI_ERROR_INVALID_ARGS;
+			goto free_mem;
+		}
+
+		new_handle = *handle;
+	}
+
+	entry->idx = 0;
+	INIT_HLIST_NODE(&entry->node);
+	entry->priv_flags = priv_flags;
+	INIT_WORK(&entry->work, dbell_delayed_dispatch);
+	entry->run_delayed = flags & VMCI_FLAG_DELAYED_CB;
+	entry->notify_cb = notify_cb;
+	entry->client_data = client_data;
+	atomic_set(&entry->active, 0);
+
+	result = vmci_resource_add(&entry->resource,
+				   VMCI_RESOURCE_TYPE_DOORBELL,
+				   new_handle);
+	if (result != VMCI_SUCCESS) {
+		pr_warn("Failed to add new resource (handle=0x%x:0x%x), error: %d\n",
+			new_handle.context, new_handle.resource, result);
+		goto free_mem;
+	}
+
+	new_handle = vmci_resource_handle(&entry->resource);
+	if (vmci_guest_code_active()) {
+		dbell_index_table_add(entry);
+		result = dbell_link(new_handle, entry->idx);
+		if (VMCI_SUCCESS != result)
+			goto destroy_resource;
+
+		atomic_set(&entry->active, 1);
+	}
+
+	*handle = new_handle;
+
+	return result;
+
+ destroy_resource:
+	dbell_index_table_remove(entry);
+	vmci_resource_remove(&entry->resource);
+ free_mem:
+	kfree(entry);
+	return result;
+}
+EXPORT_SYMBOL_GPL(vmci_doorbell_create);
+
+/*
+ * vmci_doorbell_destroy() - Destroy a doorbell.
+ * @handle:     The handle tracking the resource.
+ *
+ * Destroys a doorbell previously created with vmcii_doorbell_create. This
+ * operation may block waiting for a callback to finish.
+ */
+int vmci_doorbell_destroy(struct vmci_handle handle)
+{
+	struct dbell_entry *entry;
+	struct vmci_resource *resource;
+
+	if (VMCI_HANDLE_INVALID(handle))
+		return VMCI_ERROR_INVALID_ARGS;
+
+	resource = vmci_resource_by_handle(handle,
+					   VMCI_RESOURCE_TYPE_DOORBELL);
+	if (!resource) {
+		pr_devel("Failed to destroy doorbell (handle=0x%x:0x%x).\n",
+			 handle.context, handle.resource);
+		return VMCI_ERROR_NOT_FOUND;
+	}
+
+	entry = container_of(resource, struct dbell_entry, resource);
+
+	if (vmci_guest_code_active()) {
+		int result;
+
+		dbell_index_table_remove(entry);
+
+		result = dbell_unlink(handle);
+		if (VMCI_SUCCESS != result) {
+
+			/*
+			 * The only reason this should fail would be
+			 * an inconsistency between guest and
+			 * hypervisor state, where the guest believes
+			 * it has an active registration whereas the
+			 * hypervisor doesn't. One case where this may
+			 * happen is if a doorbell is unregistered
+			 * following a hibernation at a time where the
+			 * doorbell state hasn't been restored on the
+			 * hypervisor side yet. Since the handle has
+			 * now been removed in the guest, we just
+			 * print a warning and return success.
+			 */
+			pr_devel("Unlink of doorbell (handle=0x%x:0x%x) unknown by hypervisor (error=%d).\n",
+				 handle.context, handle.resource, result);
+		}
+	}
+
+	/*
+	 * Now remove the resource from the table.  It might still be in use
+	 * after this, in a callback or still on the delayed work queue.
+	 */
+	vmci_resource_put(&entry->resource);
+	vmci_resource_remove(&entry->resource);
+
+	kfree(entry);
+
+	return VMCI_SUCCESS;
+}
+EXPORT_SYMBOL_GPL(vmci_doorbell_destroy);
+
+/*
+ * vmci_doorbell_notify() - Ring the doorbell (and hide in the bushes).
+ * @dst:        The handlle identifying the doorbell resource
+ * @priv_flags: Priviledge flags.
+ *
+ * Generates a notification on the doorbell identified by the
+ * handle. For host side generation of notifications, the caller
+ * can specify what the privilege of the calling side is.
+ */
+int vmci_doorbell_notify(struct vmci_handle dst, u32 priv_flags)
+{
+	int retval;
+	enum vmci_route route;
+	struct vmci_handle src;
+
+	if (VMCI_HANDLE_INVALID(dst) ||
+	    (priv_flags & ~VMCI_PRIVILEGE_ALL_FLAGS))
+		return VMCI_ERROR_INVALID_ARGS;
+
+	src = VMCI_INVALID_HANDLE;
+	retval = vmci_route(&src, &dst, false, &route);
+	if (retval < VMCI_SUCCESS)
+		return retval;
+
+	if (VMCI_ROUTE_AS_HOST == route)
+		return vmci_ctx_notify_dbell(VMCI_HOST_CONTEXT_ID,
+					     dst, priv_flags);
+
+	if (VMCI_ROUTE_AS_GUEST == route)
+		return dbell_notify_as_guest(dst, priv_flags);
+
+	pr_warn("Unknown route (%d) for doorbell.\n", route);
+	return VMCI_ERROR_DST_UNREACHABLE;
+}
+EXPORT_SYMBOL_GPL(vmci_doorbell_notify);
diff --git a/drivers/misc/vmw_vmci/vmci_doorbell.h b/drivers/misc/vmw_vmci/vmci_doorbell.h
new file mode 100644
index 0000000..e4c0b17
--- /dev/null
+++ b/drivers/misc/vmw_vmci/vmci_doorbell.h
@@ -0,0 +1,51 @@
+/*
+ * 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_DOORBELL_H
+#define VMCI_DOORBELL_H
+
+#include <linux/vmw_vmci_defs.h>
+#include <linux/types.h>
+
+#include "vmci_driver.h"
+
+/*
+ * VMCINotifyResourceInfo: Used to create and destroy doorbells, and
+ * generate a notification for a doorbell or queue pair.
+ */
+struct vmci_dbell_notify_resource_info {
+	struct vmci_handle handle;
+	u16 resource;
+	u16 action;
+	s32 result;
+};
+
+/*
+ * Structure used for checkpointing the doorbell mappings. It is
+ * written to the checkpoint as is, so changing this structure will
+ * break checkpoint compatibility.
+ */
+struct dbell_cpt_state {
+	struct vmci_handle handle;
+	u64 bitmap_idx;
+};
+
+int vmci_dbell_host_context_notify(u32 src_cid, struct vmci_handle handle);
+int vmci_dbell_get_priv_flags(struct vmci_handle handle, u32 *priv_flags);
+
+bool vmci_dbell_register_notification_bitmap(u32 bitmap_ppn);
+void vmci_dbell_scan_notification_entries(u8 *bitmap);
+
+#endif /* VMCI_DOORBELL_H */

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