Merge tag 'trace-printf-v6.13' of git://git.kernel.org/pub/scm/linux/kernel/git/trace...

[drm/drm-misc.git] / drivers / misc / vmw_vmci / vmci_context.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * VMware VMCI Driver
 *
 * Copyright (C) 2012 VMware, Inc. All rights reserved.
 */

#include <linux/vmw_vmci_defs.h>
#include <linux/vmw_vmci_api.h>
#include <linux/highmem.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/sched.h>
#include <linux/cred.h>
#include <linux/slab.h>

#include "vmci_queue_pair.h"
#include "vmci_datagram.h"
#include "vmci_doorbell.h"
#include "vmci_context.h"
#include "vmci_driver.h"
#include "vmci_event.h"

/* Use a wide upper bound for the maximum contexts. */
#define VMCI_MAX_CONTEXTS 2000

/*
 * List of current VMCI contexts.  Contexts can be added by
 * vmci_ctx_create() and removed via vmci_ctx_destroy().
 * These, along with context lookup, are protected by the
 * list structure's lock.
 */
static struct {
        struct list_head head;
        spinlock_t lock; /* Spinlock for context list operations */
} ctx_list = {
        .head = LIST_HEAD_INIT(ctx_list.head),
        .lock = __SPIN_LOCK_UNLOCKED(ctx_list.lock),
};

/* Used by contexts that did not set up notify flag pointers */
static bool ctx_dummy_notify;

static void ctx_signal_notify(struct vmci_ctx *context)
{
        *context->notify = true;
}

static void ctx_clear_notify(struct vmci_ctx *context)
{
        *context->notify = false;
}

/*
 * If nothing requires the attention of the guest, clears both
 * notify flag and call.
 */
static void ctx_clear_notify_call(struct vmci_ctx *context)
{
        if (context->pending_datagrams == 0 &&
            vmci_handle_arr_get_size(context->pending_doorbell_array) == 0)
                ctx_clear_notify(context);
}

/*
 * Sets the context's notify flag iff datagrams are pending for this
 * context.  Called from vmci_setup_notify().
 */
void vmci_ctx_check_signal_notify(struct vmci_ctx *context)
{
        spin_lock(&context->lock);
        if (context->pending_datagrams)
                ctx_signal_notify(context);
        spin_unlock(&context->lock);
}

/*
 * Allocates and initializes a VMCI context.
 */
struct vmci_ctx *vmci_ctx_create(u32 cid, u32 priv_flags,
                                 uintptr_t event_hnd,
                                 int user_version,
                                 const struct cred *cred)
{
        struct vmci_ctx *context;
        int error;

        if (cid == VMCI_INVALID_ID) {
                pr_devel("Invalid context ID for VMCI context\n");
                error = -EINVAL;
                goto err_out;
        }

        if (priv_flags & ~VMCI_PRIVILEGE_ALL_FLAGS) {
                pr_devel("Invalid flag (flags=0x%x) for VMCI context\n",
                         priv_flags);
                error = -EINVAL;
                goto err_out;
        }

        if (user_version == 0) {
                pr_devel("Invalid suer_version %d\n", user_version);
                error = -EINVAL;
                goto err_out;
        }

        context = kzalloc(sizeof(*context), GFP_KERNEL);
        if (!context) {
                pr_warn("Failed to allocate memory for VMCI context\n");
                error = -ENOMEM;
                goto err_out;
        }

        kref_init(&context->kref);
        spin_lock_init(&context->lock);
        INIT_LIST_HEAD(&context->list_item);
        INIT_LIST_HEAD(&context->datagram_queue);
        INIT_LIST_HEAD(&context->notifier_list);

        /* Initialize host-specific VMCI context. */
        init_waitqueue_head(&context->host_context.wait_queue);

        context->queue_pair_array =
                vmci_handle_arr_create(0, VMCI_MAX_GUEST_QP_COUNT);
        if (!context->queue_pair_array) {
                error = -ENOMEM;
                goto err_free_ctx;
        }

        context->doorbell_array =
                vmci_handle_arr_create(0, VMCI_MAX_GUEST_DOORBELL_COUNT);
        if (!context->doorbell_array) {
                error = -ENOMEM;
                goto err_free_qp_array;
        }

        context->pending_doorbell_array =
                vmci_handle_arr_create(0, VMCI_MAX_GUEST_DOORBELL_COUNT);
        if (!context->pending_doorbell_array) {
                error = -ENOMEM;
                goto err_free_db_array;
        }

        context->user_version = user_version;

        context->priv_flags = priv_flags;

        if (cred)
                context->cred = get_cred(cred);

        context->notify = &ctx_dummy_notify;
        context->notify_page = NULL;

        /*
         * If we collide with an existing context we generate a new
         * and use it instead. The VMX will determine if regeneration
         * is okay. Since there isn't 4B - 16 VMs running on a given
         * host, the below loop will terminate.
         */
        spin_lock(&ctx_list.lock);

        while (vmci_ctx_exists(cid)) {
                /* We reserve the lowest 16 ids for fixed contexts. */
                cid = max(cid, VMCI_RESERVED_CID_LIMIT - 1) + 1;
                if (cid == VMCI_INVALID_ID)
                        cid = VMCI_RESERVED_CID_LIMIT;
        }
        context->cid = cid;

        list_add_tail_rcu(&context->list_item, &ctx_list.head);
        spin_unlock(&ctx_list.lock);

        return context;

 err_free_db_array:
        vmci_handle_arr_destroy(context->doorbell_array);
 err_free_qp_array:
        vmci_handle_arr_destroy(context->queue_pair_array);
 err_free_ctx:
        kfree(context);
 err_out:
        return ERR_PTR(error);
}

/*
 * Destroy VMCI context.
 */
void vmci_ctx_destroy(struct vmci_ctx *context)
{
        spin_lock(&ctx_list.lock);
        list_del_rcu(&context->list_item);
        spin_unlock(&ctx_list.lock);
        synchronize_rcu();

        vmci_ctx_put(context);
}

/*
 * Fire notification for all contexts interested in given cid.
 */
static int ctx_fire_notification(u32 context_id, u32 priv_flags)
{
        u32 i, array_size;
        struct vmci_ctx *sub_ctx;
        struct vmci_handle_arr *subscriber_array;
        struct vmci_handle context_handle =
                vmci_make_handle(context_id, VMCI_EVENT_HANDLER);

        /*
         * We create an array to hold the subscribers we find when
         * scanning through all contexts.
         */
        subscriber_array = vmci_handle_arr_create(0, VMCI_MAX_CONTEXTS);
        if (subscriber_array == NULL)
                return VMCI_ERROR_NO_MEM;

        /*
         * Scan all contexts to find who is interested in being
         * notified about given contextID.
         */
        rcu_read_lock();
        list_for_each_entry_rcu(sub_ctx, &ctx_list.head, list_item) {
                struct vmci_handle_list *node;

                /*
                 * We only deliver notifications of the removal of
                 * contexts, if the two contexts are allowed to
                 * interact.
                 */
                if (vmci_deny_interaction(priv_flags, sub_ctx->priv_flags))
                        continue;

                list_for_each_entry_rcu(node, &sub_ctx->notifier_list, node) {
                        if (!vmci_handle_is_equal(node->handle, context_handle))
                                continue;

                        vmci_handle_arr_append_entry(&subscriber_array,
                                        vmci_make_handle(sub_ctx->cid,
                                                         VMCI_EVENT_HANDLER));
                }
        }
        rcu_read_unlock();

        /* Fire event to all subscribers. */
        array_size = vmci_handle_arr_get_size(subscriber_array);
        for (i = 0; i < array_size; i++) {
                int result;
                struct vmci_event_ctx ev;

                ev.msg.hdr.dst = vmci_handle_arr_get_entry(subscriber_array, i);
                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 = VMCI_EVENT_CTX_REMOVED;
                ev.payload.context_id = context_id;

                result = vmci_datagram_dispatch(VMCI_HYPERVISOR_CONTEXT_ID,
                                                &ev.msg.hdr, false);
                if (result < VMCI_SUCCESS) {
                        pr_devel("Failed to enqueue event datagram (type=%d) for context (ID=0x%x)\n",
                                 ev.msg.event_data.event,
                                 ev.msg.hdr.dst.context);
                        /* We continue to enqueue on next subscriber. */
                }
        }
        vmci_handle_arr_destroy(subscriber_array);

        return VMCI_SUCCESS;
}

/*
 * Returns the current number of pending datagrams. The call may
 * also serve as a synchronization point for the datagram queue,
 * as no enqueue operations can occur concurrently.
 */
int vmci_ctx_pending_datagrams(u32 cid, u32 *pending)
{
        struct vmci_ctx *context;

        context = vmci_ctx_get(cid);
        if (context == NULL)
                return VMCI_ERROR_INVALID_ARGS;

        spin_lock(&context->lock);
        if (pending)
                *pending = context->pending_datagrams;
        spin_unlock(&context->lock);
        vmci_ctx_put(context);

        return VMCI_SUCCESS;
}

/*
 * Queues a VMCI datagram for the appropriate target VM context.
 */
int vmci_ctx_enqueue_datagram(u32 cid, struct vmci_datagram *dg)
{
        struct vmci_datagram_queue_entry *dq_entry;
        struct vmci_ctx *context;
        struct vmci_handle dg_src;
        size_t vmci_dg_size;

        vmci_dg_size = VMCI_DG_SIZE(dg);
        if (vmci_dg_size > VMCI_MAX_DG_SIZE) {
                pr_devel("Datagram too large (bytes=%zu)\n", vmci_dg_size);
                return VMCI_ERROR_INVALID_ARGS;
        }

        /* Get the target VM's VMCI context. */
        context = vmci_ctx_get(cid);
        if (!context) {
                pr_devel("Invalid context (ID=0x%x)\n", cid);
                return VMCI_ERROR_INVALID_ARGS;
        }

        /* Allocate guest call entry and add it to the target VM's queue. */
        dq_entry = kmalloc(sizeof(*dq_entry), GFP_KERNEL);
        if (dq_entry == NULL) {
                pr_warn("Failed to allocate memory for datagram\n");
                vmci_ctx_put(context);
                return VMCI_ERROR_NO_MEM;
        }
        dq_entry->dg = dg;
        dq_entry->dg_size = vmci_dg_size;
        dg_src = dg->src;
        INIT_LIST_HEAD(&dq_entry->list_item);

        spin_lock(&context->lock);

        /*
         * We put a higher limit on datagrams from the hypervisor.  If
         * the pending datagram is not from hypervisor, then we check
         * if enqueueing it would exceed the
         * VMCI_MAX_DATAGRAM_QUEUE_SIZE limit on the destination.  If
         * the pending datagram is from hypervisor, we allow it to be
         * queued at the destination side provided we don't reach the
         * VMCI_MAX_DATAGRAM_AND_EVENT_QUEUE_SIZE limit.
         */
        if (context->datagram_queue_size + vmci_dg_size >=
            VMCI_MAX_DATAGRAM_QUEUE_SIZE &&
            (!vmci_handle_is_equal(dg_src,
                                vmci_make_handle
                                (VMCI_HYPERVISOR_CONTEXT_ID,
                                 VMCI_CONTEXT_RESOURCE_ID)) ||
             context->datagram_queue_size + vmci_dg_size >=
             VMCI_MAX_DATAGRAM_AND_EVENT_QUEUE_SIZE)) {
                spin_unlock(&context->lock);
                vmci_ctx_put(context);
                kfree(dq_entry);
                pr_devel("Context (ID=0x%x) receive queue is full\n", cid);
                return VMCI_ERROR_NO_RESOURCES;
        }

        list_add(&dq_entry->list_item, &context->datagram_queue);
        context->pending_datagrams++;
        context->datagram_queue_size += vmci_dg_size;
        ctx_signal_notify(context);
        wake_up(&context->host_context.wait_queue);
        spin_unlock(&context->lock);
        vmci_ctx_put(context);

        return vmci_dg_size;
}

/*
 * Verifies whether a context with the specified context ID exists.
 * FIXME: utility is dubious as no decisions can be reliably made
 * using this data as context can appear and disappear at any time.
 */
bool vmci_ctx_exists(u32 cid)
{
        struct vmci_ctx *context;
        bool exists = false;

        rcu_read_lock();

        list_for_each_entry_rcu(context, &ctx_list.head, list_item) {
                if (context->cid == cid) {
                        exists = true;
                        break;
                }
        }

        rcu_read_unlock();
        return exists;
}

/*
 * Retrieves VMCI context corresponding to the given cid.
 */
struct vmci_ctx *vmci_ctx_get(u32 cid)
{
        struct vmci_ctx *c, *context = NULL;

        if (cid == VMCI_INVALID_ID)
                return NULL;

        rcu_read_lock();
        list_for_each_entry_rcu(c, &ctx_list.head, list_item) {
                if (c->cid == cid) {
                        /*
                         * The context owner drops its own reference to the
                         * context only after removing it from the list and
                         * waiting for RCU grace period to expire. This
                         * means that we are not about to increase the
                         * reference count of something that is in the
                         * process of being destroyed.
                         */
                        context = c;
                        kref_get(&context->kref);
                        break;
                }
        }
        rcu_read_unlock();

        return context;
}

/*
 * Deallocates all parts of a context data structure. This
 * function doesn't lock the context, because it assumes that
 * the caller was holding the last reference to context.
 */
static void ctx_free_ctx(struct kref *kref)
{
        struct vmci_ctx *context = container_of(kref, struct vmci_ctx, kref);
        struct vmci_datagram_queue_entry *dq_entry, *dq_entry_tmp;
        struct vmci_handle temp_handle;
        struct vmci_handle_list *notifier, *tmp;

        /*
         * Fire event to all contexts interested in knowing this
         * context is dying.
         */
        ctx_fire_notification(context->cid, context->priv_flags);

        /*
         * Cleanup all queue pair resources attached to context.  If
         * the VM dies without cleaning up, this code will make sure
         * that no resources are leaked.
         */
        temp_handle = vmci_handle_arr_get_entry(context->queue_pair_array, 0);
        while (!vmci_handle_is_equal(temp_handle, VMCI_INVALID_HANDLE)) {
                if (vmci_qp_broker_detach(temp_handle,
                                          context) < VMCI_SUCCESS) {
                        /*
                         * When vmci_qp_broker_detach() succeeds it
                         * removes the handle from the array.  If
                         * detach fails, we must remove the handle
                         * ourselves.
                         */
                        vmci_handle_arr_remove_entry(context->queue_pair_array,
                                                     temp_handle);
                }
                temp_handle =
                    vmci_handle_arr_get_entry(context->queue_pair_array, 0);
        }

        /*
         * It is fine to destroy this without locking the callQueue, as
         * this is the only thread having a reference to the context.
         */
        list_for_each_entry_safe(dq_entry, dq_entry_tmp,
                                 &context->datagram_queue, list_item) {
                WARN_ON(dq_entry->dg_size != VMCI_DG_SIZE(dq_entry->dg));
                list_del(&dq_entry->list_item);
                kfree(dq_entry->dg);
                kfree(dq_entry);
        }

        list_for_each_entry_safe(notifier, tmp,
                                 &context->notifier_list, node) {
                list_del(&notifier->node);
                kfree(notifier);
        }

        vmci_handle_arr_destroy(context->queue_pair_array);
        vmci_handle_arr_destroy(context->doorbell_array);
        vmci_handle_arr_destroy(context->pending_doorbell_array);
        vmci_ctx_unset_notify(context);
        if (context->cred)
                put_cred(context->cred);
        kfree(context);
}

/*
 * Drops reference to VMCI context. If this is the last reference to
 * the context it will be deallocated. A context is created with
 * a reference count of one, and on destroy, it is removed from
 * the context list before its reference count is decremented. Thus,
 * if we reach zero, we are sure that nobody else are about to increment
 * it (they need the entry in the context list for that), and so there
 * is no need for locking.
 */
void vmci_ctx_put(struct vmci_ctx *context)
{
        kref_put(&context->kref, ctx_free_ctx);
}

/*
 * Dequeues the next datagram and returns it to caller.
 * The caller passes in a pointer to the max size datagram
 * it can handle and the datagram is only unqueued if the
 * size is less than max_size. If larger max_size is set to
 * the size of the datagram to give the caller a chance to
 * set up a larger buffer for the guestcall.
 */
int vmci_ctx_dequeue_datagram(struct vmci_ctx *context,
                              size_t *max_size,
                              struct vmci_datagram **dg)
{
        struct vmci_datagram_queue_entry *dq_entry;
        struct list_head *list_item;
        int rv;

        /* Dequeue the next datagram entry. */
        spin_lock(&context->lock);
        if (context->pending_datagrams == 0) {
                ctx_clear_notify_call(context);
                spin_unlock(&context->lock);
                pr_devel("No datagrams pending\n");
                return VMCI_ERROR_NO_MORE_DATAGRAMS;
        }

        list_item = context->datagram_queue.next;

        dq_entry =
            list_entry(list_item, struct vmci_datagram_queue_entry, list_item);

        /* Check size of caller's buffer. */
        if (*max_size < dq_entry->dg_size) {
                *max_size = dq_entry->dg_size;
                spin_unlock(&context->lock);
                pr_devel("Caller's buffer should be at least (size=%u bytes)\n",
                         (u32) *max_size);
                return VMCI_ERROR_NO_MEM;
        }

        list_del(list_item);
        context->pending_datagrams--;
        context->datagram_queue_size -= dq_entry->dg_size;
        if (context->pending_datagrams == 0) {
                ctx_clear_notify_call(context);
                rv = VMCI_SUCCESS;
        } else {
                /*
                 * Return the size of the next datagram.
                 */
                struct vmci_datagram_queue_entry *next_entry;

                list_item = context->datagram_queue.next;
                next_entry =
                    list_entry(list_item, struct vmci_datagram_queue_entry,
                               list_item);

                /*
                 * The following size_t -> int truncation is fine as
                 * the maximum size of a (routable) datagram is 68KB.
                 */
                rv = (int)next_entry->dg_size;
        }
        spin_unlock(&context->lock);

        /* Caller must free datagram. */
        *dg = dq_entry->dg;
        dq_entry->dg = NULL;
        kfree(dq_entry);

        return rv;
}

/*
 * Reverts actions set up by vmci_setup_notify().  Unmaps and unlocks the
 * page mapped/locked by vmci_setup_notify().
 */
void vmci_ctx_unset_notify(struct vmci_ctx *context)
{
        struct page *notify_page;

        spin_lock(&context->lock);

        notify_page = context->notify_page;
        context->notify = &ctx_dummy_notify;
        context->notify_page = NULL;

        spin_unlock(&context->lock);

        if (notify_page) {
                kunmap(notify_page);
                put_page(notify_page);
        }
}

/*
 * Add remote_cid to list of contexts current contexts wants
 * notifications from/about.
 */
int vmci_ctx_add_notification(u32 context_id, u32 remote_cid)
{
        struct vmci_ctx *context;
        struct vmci_handle_list *notifier, *n;
        int result;
        bool exists = false;

        context = vmci_ctx_get(context_id);
        if (!context)
                return VMCI_ERROR_NOT_FOUND;

        if (VMCI_CONTEXT_IS_VM(context_id) && VMCI_CONTEXT_IS_VM(remote_cid)) {
                pr_devel("Context removed notifications for other VMs not supported (src=0x%x, remote=0x%x)\n",
                         context_id, remote_cid);
                result = VMCI_ERROR_DST_UNREACHABLE;
                goto out;
        }

        if (context->priv_flags & VMCI_PRIVILEGE_FLAG_RESTRICTED) {
                result = VMCI_ERROR_NO_ACCESS;
                goto out;
        }

        notifier = kmalloc(sizeof(struct vmci_handle_list), GFP_KERNEL);
        if (!notifier) {
                result = VMCI_ERROR_NO_MEM;
                goto out;
        }

        INIT_LIST_HEAD(&notifier->node);
        notifier->handle = vmci_make_handle(remote_cid, VMCI_EVENT_HANDLER);

        spin_lock(&context->lock);

        if (context->n_notifiers < VMCI_MAX_CONTEXTS) {
                list_for_each_entry(n, &context->notifier_list, node) {
                        if (vmci_handle_is_equal(n->handle, notifier->handle)) {
                                exists = true;
                                break;
                        }
                }

                if (exists) {
                        kfree(notifier);
                        result = VMCI_ERROR_ALREADY_EXISTS;
                } else {
                        list_add_tail_rcu(&notifier->node,
                                          &context->notifier_list);
                        context->n_notifiers++;
                        result = VMCI_SUCCESS;
                }
        } else {
                kfree(notifier);
                result = VMCI_ERROR_NO_MEM;
        }

        spin_unlock(&context->lock);

 out:
        vmci_ctx_put(context);
        return result;
}

/*
 * Remove remote_cid from current context's list of contexts it is
 * interested in getting notifications from/about.
 */
int vmci_ctx_remove_notification(u32 context_id, u32 remote_cid)
{
        struct vmci_ctx *context;
        struct vmci_handle_list *notifier = NULL, *iter, *tmp;
        struct vmci_handle handle;

        context = vmci_ctx_get(context_id);
        if (!context)
                return VMCI_ERROR_NOT_FOUND;

        handle = vmci_make_handle(remote_cid, VMCI_EVENT_HANDLER);

        spin_lock(&context->lock);
        list_for_each_entry_safe(iter, tmp,
                                 &context->notifier_list, node) {
                if (vmci_handle_is_equal(iter->handle, handle)) {
                        list_del_rcu(&iter->node);
                        context->n_notifiers--;
                        notifier = iter;
                        break;
                }
        }
        spin_unlock(&context->lock);

        if (notifier)
                kvfree_rcu_mightsleep(notifier);

        vmci_ctx_put(context);

        return notifier ? VMCI_SUCCESS : VMCI_ERROR_NOT_FOUND;
}

static int vmci_ctx_get_chkpt_notifiers(struct vmci_ctx *context,
                                        u32 *buf_size, void **pbuf)
{
        u32 *notifiers;
        size_t data_size;
        struct vmci_handle_list *entry;
        int i = 0;

        if (context->n_notifiers == 0) {
                *buf_size = 0;
                *pbuf = NULL;
                return VMCI_SUCCESS;
        }

        data_size = context->n_notifiers * sizeof(*notifiers);
        if (*buf_size < data_size) {
                *buf_size = data_size;
                return VMCI_ERROR_MORE_DATA;
        }

        notifiers = kmalloc(data_size, GFP_ATOMIC); /* FIXME: want GFP_KERNEL */
        if (!notifiers)
                return VMCI_ERROR_NO_MEM;

        list_for_each_entry(entry, &context->notifier_list, node)
                notifiers[i++] = entry->handle.context;

        *buf_size = data_size;
        *pbuf = notifiers;
        return VMCI_SUCCESS;
}

static int vmci_ctx_get_chkpt_doorbells(struct vmci_ctx *context,
                                        u32 *buf_size, void **pbuf)
{
        struct dbell_cpt_state *dbells;
        u32 i, n_doorbells;

        n_doorbells = vmci_handle_arr_get_size(context->doorbell_array);
        if (n_doorbells > 0) {
                size_t data_size = n_doorbells * sizeof(*dbells);
                if (*buf_size < data_size) {
                        *buf_size = data_size;
                        return VMCI_ERROR_MORE_DATA;
                }

                dbells = kzalloc(data_size, GFP_ATOMIC);
                if (!dbells)
                        return VMCI_ERROR_NO_MEM;

                for (i = 0; i < n_doorbells; i++)
                        dbells[i].handle = vmci_handle_arr_get_entry(
                                                context->doorbell_array, i);

                *buf_size = data_size;
                *pbuf = dbells;
        } else {
                *buf_size = 0;
                *pbuf = NULL;
        }

        return VMCI_SUCCESS;
}

/*
 * Get current context's checkpoint state of given type.
 */
int vmci_ctx_get_chkpt_state(u32 context_id,
                             u32 cpt_type,
                             u32 *buf_size,
                             void **pbuf)
{
        struct vmci_ctx *context;
        int result;

        context = vmci_ctx_get(context_id);
        if (!context)
                return VMCI_ERROR_NOT_FOUND;

        spin_lock(&context->lock);

        switch (cpt_type) {
        case VMCI_NOTIFICATION_CPT_STATE:
                result = vmci_ctx_get_chkpt_notifiers(context, buf_size, pbuf);
                break;

        case VMCI_WELLKNOWN_CPT_STATE:
                /*
                 * For compatibility with VMX'en with VM to VM communication, we
                 * always return zero wellknown handles.
                 */

                *buf_size = 0;
                *pbuf = NULL;
                result = VMCI_SUCCESS;
                break;

        case VMCI_DOORBELL_CPT_STATE:
                result = vmci_ctx_get_chkpt_doorbells(context, buf_size, pbuf);
                break;

        default:
                pr_devel("Invalid cpt state (type=%d)\n", cpt_type);
                result = VMCI_ERROR_INVALID_ARGS;
                break;
        }

        spin_unlock(&context->lock);
        vmci_ctx_put(context);

        return result;
}

/*
 * Set current context's checkpoint state of given type.
 */
int vmci_ctx_set_chkpt_state(u32 context_id,
                             u32 cpt_type,
                             u32 buf_size,
                             void *cpt_buf)
{
        u32 i;
        u32 current_id;
        int result = VMCI_SUCCESS;
        u32 num_ids = buf_size / sizeof(u32);

        if (cpt_type == VMCI_WELLKNOWN_CPT_STATE && num_ids > 0) {
                /*
                 * We would end up here if VMX with VM to VM communication
                 * attempts to restore a checkpoint with wellknown handles.
                 */
                pr_warn("Attempt to restore checkpoint with obsolete wellknown handles\n");
                return VMCI_ERROR_OBSOLETE;
        }

        if (cpt_type != VMCI_NOTIFICATION_CPT_STATE) {
                pr_devel("Invalid cpt state (type=%d)\n", cpt_type);
                return VMCI_ERROR_INVALID_ARGS;
        }

        for (i = 0; i < num_ids && result == VMCI_SUCCESS; i++) {
                current_id = ((u32 *)cpt_buf)[i];
                result = vmci_ctx_add_notification(context_id, current_id);
                if (result != VMCI_SUCCESS)
                        break;
        }
        if (result != VMCI_SUCCESS)
                pr_devel("Failed to set cpt state (type=%d) (error=%d)\n",
                         cpt_type, result);

        return result;
}

/*
 * Retrieves the specified context's pending notifications in the
 * form of a handle array. The handle arrays returned are the
 * actual data - not a copy and should not be modified by the
 * caller. They must be released using
 * vmci_ctx_rcv_notifications_release.
 */
int vmci_ctx_rcv_notifications_get(u32 context_id,
                                   struct vmci_handle_arr **db_handle_array,
                                   struct vmci_handle_arr **qp_handle_array)
{
        struct vmci_ctx *context;
        int result = VMCI_SUCCESS;

        context = vmci_ctx_get(context_id);
        if (context == NULL)
                return VMCI_ERROR_NOT_FOUND;

        spin_lock(&context->lock);

        *db_handle_array = context->pending_doorbell_array;
        context->pending_doorbell_array =
                vmci_handle_arr_create(0, VMCI_MAX_GUEST_DOORBELL_COUNT);
        if (!context->pending_doorbell_array) {
                context->pending_doorbell_array = *db_handle_array;
                *db_handle_array = NULL;
                result = VMCI_ERROR_NO_MEM;
        }
        *qp_handle_array = NULL;

        spin_unlock(&context->lock);
        vmci_ctx_put(context);

        return result;
}

/*
 * Releases handle arrays with pending notifications previously
 * retrieved using vmci_ctx_rcv_notifications_get. If the
 * notifications were not successfully handed over to the guest,
 * success must be false.
 */
void vmci_ctx_rcv_notifications_release(u32 context_id,
                                        struct vmci_handle_arr *db_handle_array,
                                        struct vmci_handle_arr *qp_handle_array,
                                        bool success)
{
        struct vmci_ctx *context = vmci_ctx_get(context_id);

        spin_lock(&context->lock);
        if (!success) {
                struct vmci_handle handle;

                /*
                 * New notifications may have been added while we were not
                 * holding the context lock, so we transfer any new pending
                 * doorbell notifications to the old array, and reinstate the
                 * old array.
                 */

                handle = vmci_handle_arr_remove_tail(
                                        context->pending_doorbell_array);
                while (!vmci_handle_is_invalid(handle)) {
                        if (!vmci_handle_arr_has_entry(db_handle_array,
                                                       handle)) {
                                vmci_handle_arr_append_entry(
                                                &db_handle_array, handle);
                        }
                        handle = vmci_handle_arr_remove_tail(
                                        context->pending_doorbell_array);
                }
                vmci_handle_arr_destroy(context->pending_doorbell_array);
                context->pending_doorbell_array = db_handle_array;
                db_handle_array = NULL;
        } else {
                ctx_clear_notify_call(context);
        }
        spin_unlock(&context->lock);
        vmci_ctx_put(context);

        if (db_handle_array)
                vmci_handle_arr_destroy(db_handle_array);

        if (qp_handle_array)
                vmci_handle_arr_destroy(qp_handle_array);
}

/*
 * Registers that a new doorbell handle has been allocated by the
 * context. Only doorbell handles registered can be notified.
 */
int vmci_ctx_dbell_create(u32 context_id, struct vmci_handle handle)
{
        struct vmci_ctx *context;
        int result;

        if (context_id == VMCI_INVALID_ID || vmci_handle_is_invalid(handle))
                return VMCI_ERROR_INVALID_ARGS;

        context = vmci_ctx_get(context_id);
        if (context == NULL)
                return VMCI_ERROR_NOT_FOUND;

        spin_lock(&context->lock);
        if (!vmci_handle_arr_has_entry(context->doorbell_array, handle))
                result = vmci_handle_arr_append_entry(&context->doorbell_array,
                                                      handle);
        else
                result = VMCI_ERROR_DUPLICATE_ENTRY;

        spin_unlock(&context->lock);
        vmci_ctx_put(context);

        return result;
}

/*
 * Unregisters a doorbell handle that was previously registered
 * with vmci_ctx_dbell_create.
 */
int vmci_ctx_dbell_destroy(u32 context_id, struct vmci_handle handle)
{
        struct vmci_ctx *context;
        struct vmci_handle removed_handle;

        if (context_id == VMCI_INVALID_ID || vmci_handle_is_invalid(handle))
                return VMCI_ERROR_INVALID_ARGS;

        context = vmci_ctx_get(context_id);
        if (context == NULL)
                return VMCI_ERROR_NOT_FOUND;

        spin_lock(&context->lock);
        removed_handle =
            vmci_handle_arr_remove_entry(context->doorbell_array, handle);
        vmci_handle_arr_remove_entry(context->pending_doorbell_array, handle);
        spin_unlock(&context->lock);

        vmci_ctx_put(context);

        return vmci_handle_is_invalid(removed_handle) ?
            VMCI_ERROR_NOT_FOUND : VMCI_SUCCESS;
}

/*
 * Unregisters all doorbell handles that were previously
 * registered with vmci_ctx_dbell_create.
 */
int vmci_ctx_dbell_destroy_all(u32 context_id)
{
        struct vmci_ctx *context;
        struct vmci_handle handle;

        if (context_id == VMCI_INVALID_ID)
                return VMCI_ERROR_INVALID_ARGS;

        context = vmci_ctx_get(context_id);
        if (context == NULL)
                return VMCI_ERROR_NOT_FOUND;

        spin_lock(&context->lock);
        do {
                struct vmci_handle_arr *arr = context->doorbell_array;
                handle = vmci_handle_arr_remove_tail(arr);
        } while (!vmci_handle_is_invalid(handle));
        do {
                struct vmci_handle_arr *arr = context->pending_doorbell_array;
                handle = vmci_handle_arr_remove_tail(arr);
        } while (!vmci_handle_is_invalid(handle));
        spin_unlock(&context->lock);

        vmci_ctx_put(context);

        return VMCI_SUCCESS;
}

/*
 * Registers a notification of a doorbell handle initiated by the
 * specified source context. The notification of doorbells are
 * subject to the same isolation rules as datagram delivery. To
 * allow host side senders of notifications a finer granularity
 * of sender rights than those assigned to the sending context
 * itself, the host context is required to specify a different
 * set of privilege flags that will override the privileges of
 * the source context.
 */
int vmci_ctx_notify_dbell(u32 src_cid,
                          struct vmci_handle handle,
                          u32 src_priv_flags)
{
        struct vmci_ctx *dst_context;
        int result;

        if (vmci_handle_is_invalid(handle))
                return VMCI_ERROR_INVALID_ARGS;

        /* Get the target VM's VMCI context. */
        dst_context = vmci_ctx_get(handle.context);
        if (!dst_context) {
                pr_devel("Invalid context (ID=0x%x)\n", handle.context);
                return VMCI_ERROR_NOT_FOUND;
        }

        if (src_cid != handle.context) {
                u32 dst_priv_flags;

                if (VMCI_CONTEXT_IS_VM(src_cid) &&
                    VMCI_CONTEXT_IS_VM(handle.context)) {
                        pr_devel("Doorbell notification from VM to VM not supported (src=0x%x, dst=0x%x)\n",
                                 src_cid, handle.context);
                        result = VMCI_ERROR_DST_UNREACHABLE;
                        goto out;
                }

                result = vmci_dbell_get_priv_flags(handle, &dst_priv_flags);
                if (result < VMCI_SUCCESS) {
                        pr_warn("Failed to get privilege flags for destination (handle=0x%x:0x%x)\n",
                                handle.context, handle.resource);
                        goto out;
                }

                if (src_cid != VMCI_HOST_CONTEXT_ID ||
                    src_priv_flags == VMCI_NO_PRIVILEGE_FLAGS) {
                        src_priv_flags = vmci_context_get_priv_flags(src_cid);
                }

                if (vmci_deny_interaction(src_priv_flags, dst_priv_flags)) {
                        result = VMCI_ERROR_NO_ACCESS;
                        goto out;
                }
        }

        if (handle.context == VMCI_HOST_CONTEXT_ID) {
                result = vmci_dbell_host_context_notify(src_cid, handle);
        } else {
                spin_lock(&dst_context->lock);

                if (!vmci_handle_arr_has_entry(dst_context->doorbell_array,
                                               handle)) {
                        result = VMCI_ERROR_NOT_FOUND;
                } else {
                        if (!vmci_handle_arr_has_entry(
                                        dst_context->pending_doorbell_array,
                                        handle)) {
                                result = vmci_handle_arr_append_entry(
                                        &dst_context->pending_doorbell_array,
                                        handle);
                                if (result == VMCI_SUCCESS) {
                                        ctx_signal_notify(dst_context);
                                        wake_up(&dst_context->host_context.wait_queue);
                                }
                        } else {
                                result = VMCI_SUCCESS;
                        }
                }
                spin_unlock(&dst_context->lock);
        }

 out:
        vmci_ctx_put(dst_context);

        return result;
}

bool vmci_ctx_supports_host_qp(struct vmci_ctx *context)
{
        return context && context->user_version >= VMCI_VERSION_HOSTQP;
}

/*
 * Registers that a new queue pair handle has been allocated by
 * the context.
 */
int vmci_ctx_qp_create(struct vmci_ctx *context, struct vmci_handle handle)
{
        int result;

        if (context == NULL || vmci_handle_is_invalid(handle))
                return VMCI_ERROR_INVALID_ARGS;

        if (!vmci_handle_arr_has_entry(context->queue_pair_array, handle))
                result = vmci_handle_arr_append_entry(
                        &context->queue_pair_array, handle);
        else
                result = VMCI_ERROR_DUPLICATE_ENTRY;

        return result;
}

/*
 * Unregisters a queue pair handle that was previously registered
 * with vmci_ctx_qp_create.
 */
int vmci_ctx_qp_destroy(struct vmci_ctx *context, struct vmci_handle handle)
{
        struct vmci_handle hndl;

        if (context == NULL || vmci_handle_is_invalid(handle))
                return VMCI_ERROR_INVALID_ARGS;

        hndl = vmci_handle_arr_remove_entry(context->queue_pair_array, handle);

        return vmci_handle_is_invalid(hndl) ?
                VMCI_ERROR_NOT_FOUND : VMCI_SUCCESS;
}

/*
 * Determines whether a given queue pair handle is registered
 * with the given context.
 */
bool vmci_ctx_qp_exists(struct vmci_ctx *context, struct vmci_handle handle)
{
        if (context == NULL || vmci_handle_is_invalid(handle))
                return false;

        return vmci_handle_arr_has_entry(context->queue_pair_array, handle);
}

/*
 * vmci_context_get_priv_flags() - Retrieve privilege flags.
 * @context_id: The context ID of the VMCI context.
 *
 * Retrieves privilege flags of the given VMCI context ID.
 */
u32 vmci_context_get_priv_flags(u32 context_id)
{
        if (vmci_host_code_active()) {
                u32 flags;
                struct vmci_ctx *context;

                context = vmci_ctx_get(context_id);
                if (!context)
                        return VMCI_LEAST_PRIVILEGE_FLAGS;

                flags = context->priv_flags;
                vmci_ctx_put(context);
                return flags;
        }
        return VMCI_NO_PRIVILEGE_FLAGS;
}
EXPORT_SYMBOL_GPL(vmci_context_get_priv_flags);

/*
 * vmci_is_context_owner() - Determimnes if user is the context owner
 * @context_id: The context ID of the VMCI context.
 * @uid:        The host user id (real kernel value).
 *
 * Determines whether a given UID is the owner of given VMCI context.
 */
bool vmci_is_context_owner(u32 context_id, kuid_t uid)
{
        bool is_owner = false;

        if (vmci_host_code_active()) {
                struct vmci_ctx *context = vmci_ctx_get(context_id);
                if (context) {
                        if (context->cred)
                                is_owner = uid_eq(context->cred->uid, uid);
                        vmci_ctx_put(context);
                }
        }

        return is_owner;
}
EXPORT_SYMBOL_GPL(vmci_is_context_owner);