text: /* Copyright (C) 2009 Red Hat, Inc.
   * Copyright (C) 2006 Rusty Russell IBM Corporation
   *
   * Author: Michael S. Tsirkin <mst@redhat.com>
   *
   * Inspiration, some code, and most witty comments come from
   * Documentation/virtual/lguest/lguest.c, by Rusty Russell
   *
   * This work is licensed under the terms of the GNU GPL, version 2.
   *
   * Generic code for virtio server in host kernel.
   */
  
  #include <linux/eventfd.h>
  #include <linux/vhost.h>
  #include <linux/uio.h>
  #include <linux/mm.h>
  #include <linux/mmu_context.h>
  #include <linux/miscdevice.h>
  #include <linux/mutex.h>
  #include <linux/poll.h>
  #include <linux/file.h>
  #include <linux/highmem.h>
  #include <linux/slab.h>
  #include <linux/vmalloc.h>
  #include <linux/kthread.h>
  #include <linux/cgroup.h>
  #include <linux/module.h>
  #include <linux/sort.h>
  #include <linux/sched/mm.h>
  #include <linux/sched/signal.h>
  #include <linux/interval_tree_generic.h>
  #include <linux/nospec.h>
  
  #include "vhost.h"
  
  static ushort max_mem_regions = 64;
  module_param(max_mem_regions, ushort, 0444);
  MODULE_PARM_DESC(max_mem_regions,
  	"Maximum number of memory regions in memory map. (default: 64)");
  static int max_iotlb_entries = 2048;
  module_param(max_iotlb_entries, int, 0444);
  MODULE_PARM_DESC(max_iotlb_entries,
  	"Maximum number of iotlb entries. (default: 2048)");
  
  enum {
  	VHOST_MEMORY_F_LOG = 0x1,
  };
  
  #define vhost_used_event(vq) ((__virtio16 __user *)&vq->avail->ring[vq->num])
  #define vhost_avail_event(vq) ((__virtio16 __user *)&vq->used->ring[vq->num])
  
  INTERVAL_TREE_DEFINE(struct vhost_umem_node,
  		     rb, __u64, __subtree_last,
  		     START, LAST, static inline, vhost_umem_interval_tree);
  
  #ifdef CONFIG_VHOST_CROSS_ENDIAN_LEGACY
  static void vhost_disable_cross_endian(struct vhost_virtqueue *vq)
  {
  	vq->user_be = !virtio_legacy_is_little_endian();
  }
  
  static void vhost_enable_cross_endian_big(struct vhost_virtqueue *vq)
  {
  	vq->user_be = true;
  }
  
  static void vhost_enable_cross_endian_little(struct vhost_virtqueue *vq)
  {
  	vq->user_be = false;
  }
  
  static long vhost_set_vring_endian(struct vhost_virtqueue *vq, int __user *argp)
  {
  	struct vhost_vring_state s;
  
  	if (vq->private_data)
  		return -EBUSY;
  
  	if (copy_from_user(&s, argp, sizeof(s)))
  		return -EFAULT;
  
  	if (s.num != VHOST_VRING_LITTLE_ENDIAN &&
  	    s.num != VHOST_VRING_BIG_ENDIAN)
  		return -EINVAL;
  
  	if (s.num == VHOST_VRING_BIG_ENDIAN)
  		vhost_enable_cross_endian_big(vq);
  	else
  		vhost_enable_cross_endian_little(vq);
  
  	return 0;
  }
  
  static long vhost_get_vring_endian(struct vhost_virtqueue *vq, u32 idx,
  				   int __user *argp)
  {
  	struct vhost_vring_state s = {
  		.index = idx,
  		.num = vq->user_be
  	};
  
  	if (copy_to_user(argp, &s, sizeof(s)))
  		return -EFAULT;
  
  	return 0;
  }
  
  static void vhost_init_is_le(struct vhost_virtqueue *vq)
  {
  	/* Note for legacy virtio: user_be is initialized at reset time
  	 * according to the host endianness. If userspace does not set an
  	 * explicit endianness, the default behavior is native endian, as
  	 * expected by legacy virtio.
  	 */
  	vq->is_le = vhost_has_feature(vq, VIRTIO_F_VERSION_1) || !vq->user_be;
  }
  #else
  static void vhost_disable_cross_endian(struct vhost_virtqueue *vq)
  {
  }
  
  static long vhost_set_vring_endian(struct vhost_virtqueue *vq, int __user *argp)
  {
  	return -ENOIOCTLCMD;
  }
  
  static long vhost_get_vring_endian(struct vhost_virtqueue *vq, u32 idx,
  				   int __user *argp)
  {
  	return -ENOIOCTLCMD;
  }
  
  static void vhost_init_is_le(struct vhost_virtqueue *vq)
  {
  	vq->is_le = vhost_has_feature(vq, VIRTIO_F_VERSION_1)
  		|| virtio_legacy_is_little_endian();
  }
  #endif /* CONFIG_VHOST_CROSS_ENDIAN_LEGACY */
  
  static void vhost_reset_is_le(struct vhost_virtqueue *vq)
  {
  	vhost_init_is_le(vq);
  }
  
  struct vhost_flush_struct {
  	struct vhost_work work;
  	struct completion wait_event;
  };
  
  static void vhost_flush_work(struct vhost_work *work)
  {
  	struct vhost_flush_struct *s;
  
  	s = container_of(work, struct vhost_flush_struct, work);
  	complete(&s->wait_event);
  }
  
  static void vhost_poll_func(struct file *file, wait_queue_head_t *wqh,
  			    poll_table *pt)
  {
  	struct vhost_poll *poll;
  
  	poll = container_of(pt, struct vhost_poll, table);
  	poll->wqh = wqh;
  	add_wait_queue(wqh, &poll->wait);
  }
  
  static int vhost_poll_wakeup(wait_queue_entry_t *wait, unsigned mode, int sync,
  			     void *key)
  {
  	struct vhost_poll *poll = container_of(wait, struct vhost_poll, wait);
  
  	if (!(key_to_poll(key) & poll->mask))
  		return 0;
  
  	vhost_poll_queue(poll);
  	return 0;
  }
  
  void vhost_work_init(struct vhost_work *work, vhost_work_fn_t fn)
  {
  	clear_bit(VHOST_WORK_QUEUED, &work->flags);
  	work->fn = fn;
  }
  EXPORT_SYMBOL_GPL(vhost_work_init);
  
  /* Init poll structure */
  void vhost_poll_init(struct vhost_poll *poll, vhost_work_fn_t fn,
  		     __poll_t mask, struct vhost_dev *dev)
  {
  	init_waitqueue_func_entry(&poll->wait, vhost_poll_wakeup);
  	init_poll_funcptr(&poll->table, vhost_poll_func);
  	poll->mask = mask;
  	poll->dev = dev;
  	poll->wqh = NULL;
  
  	vhost_work_init(&poll->work, fn);
  }
  EXPORT_SYMBOL_GPL(vhost_poll_init);
  
  /* Start polling a file. We add ourselves to file's wait queue. The caller must
   * keep a reference to a file until after vhost_poll_stop is called. */
  int vhost_poll_start(struct vhost_poll *poll, struct file *file)
  {
  	__poll_t mask;
  	int ret = 0;
  
  	if (poll->wqh)
  		return 0;
  
  	mask = vfs_poll(file, &poll->table);
  	if (mask)
  		vhost_poll_wakeup(&poll->wait, 0, 0, poll_to_key(mask));
  	if (mask & EPOLLERR) {
  		vhost_poll_stop(poll);
  		ret = -EINVAL;
  	}
  
  	return ret;
  }
  EXPORT_SYMBOL_GPL(vhost_poll_start);
  
  /* Stop polling a file. After this function returns, it becomes safe to drop the
   * file reference. You must also flush afterwards. */
  void vhost_poll_stop(struct vhost_poll *poll)
  {
  	if (poll->wqh) {
  		remove_wait_queue(poll->wqh, &poll->wait);
  		poll->wqh = NULL;
  	}
  }
  EXPORT_SYMBOL_GPL(vhost_poll_stop);
  
  void vhost_work_flush(struct vhost_dev *dev, struct vhost_work *work)
  {
  	struct vhost_flush_struct flush;
  
  	if (dev->worker) {
  		init_completion(&flush.wait_event);
  		vhost_work_init(&flush.work, vhost_flush_work);
  
  		vhost_work_queue(dev, &flush.work);
  		wait_for_completion(&flush.wait_event);
  	}
  }
  EXPORT_SYMBOL_GPL(vhost_work_flush);
  
  /* Flush any work that has been scheduled. When calling this, don't hold any
   * locks that are also used by the callback. */
  void vhost_poll_flush(struct vhost_poll *poll)
  {
  	vhost_work_flush(poll->dev, &poll->work);
  }
  EXPORT_SYMBOL_GPL(vhost_poll_flush);
  
  void vhost_work_queue(struct vhost_dev *dev, struct vhost_work *work)
  {
  	if (!dev->worker)
  		return;
  
  	if (!test_and_set_bit(VHOST_WORK_QUEUED, &work->flags)) {
  		/* We can only add the work to the list after we're
  		 * sure it was not in the list.
  		 * test_and_set_bit() implies a memory barrier.
  		 */
  		llist_add(&work->node, &dev->work_list);
  		wake_up_process(dev->worker);
  	}
  }
  EXPORT_SYMBOL_GPL(vhost_work_queue);
  
  /* A lockless hint for busy polling code to exit the loop */
  bool vhost_has_work(struct vhost_dev *dev)
  {
  	return !llist_empty(&dev->work_list);
  }
  EXPORT_SYMBOL_GPL(vhost_has_work);
  
  void vhost_poll_queue(struct vhost_poll *poll)
  {
  	vhost_work_queue(poll->dev, &poll->work);
  }
  EXPORT_SYMBOL_GPL(vhost_poll_queue);
  
  static void __vhost_vq_meta_reset(struct vhost_virtqueue *vq)
  {
  	int j;
  
  	for (j = 0; j < VHOST_NUM_ADDRS; j++)
  		vq->meta_iotlb[j] = NULL;
  }
  
  static void vhost_vq_meta_reset(struct vhost_dev *d)
  {
  	int i;
  
  	for (i = 0; i < d->nvqs; ++i)
  		__vhost_vq_meta_reset(d->vqs[i]);
  }
  
  static void vhost_vq_reset(struct vhost_dev *dev,
  			   struct vhost_virtqueue *vq)
  {
  	vq->num = 1;
  	vq->desc = NULL;
  	vq->avail = NULL;
  	vq->used = NULL;
  	vq->last_avail_idx = 0;
  	vq->avail_idx = 0;
  	vq->last_used_idx = 0;
  	vq->signalled_used = 0;
  	vq->signalled_used_valid = false;
  	vq->used_flags = 0;
  	vq->log_used = false;
  	vq->log_addr = -1ull;
  	vq->private_data = NULL;
  	vq->acked_features = 0;
  	vq->acked_backend_features = 0;
  	vq->log_base = NULL;
  	vq->error_ctx = NULL;
  	vq->kick = NULL;
  	vq->call_ctx = NULL;
  	vq->log_ctx = NULL;
  	vhost_reset_is_le(vq);
  	vhost_disable_cross_endian(vq);
  	vq->busyloop_timeout = 0;
  	vq->umem = NULL;
  	vq->iotlb = NULL;
  	__vhost_vq_meta_reset(vq);
  }
  
  static int vhost_worker(void *data)
  {
  	struct vhost_dev *dev = data;
  	struct vhost_work *work, *work_next;
  	struct llist_node *node;
  	mm_segment_t oldfs = get_fs();
  
  	set_fs(USER_DS);
  	use_mm(dev->mm);
  
  	for (;;) {
  		/* mb paired w/ kthread_stop */
  		set_current_state(TASK_INTERRUPTIBLE);
  
  		if (kthread_should_stop()) {
  			__set_current_state(TASK_RUNNING);
  			break;
  		}
  
  		node = llist_del_all(&dev->work_list);
  		if (!node)
  			schedule();
  
  		node = llist_reverse_order(node);
  		/* make sure flag is seen after deletion */
  		smp_wmb();
  		llist_for_each_entry_safe(work, work_next, node, node) {
  			clear_bit(VHOST_WORK_QUEUED, &work->flags);
  			__set_current_state(TASK_RUNNING);
  			work->fn(work);
  			if (need_resched())
  				schedule();
  		}
  	}
  	unuse_mm(dev->mm);
  	set_fs(oldfs);
  	return 0;
  }
  
  static void vhost_vq_free_iovecs(struct vhost_virtqueue *vq)
  {
  	kfree(vq->indirect);
  	vq->indirect = NULL;
  	kfree(vq->log);
  	vq->log = NULL;
  	kfree(vq->heads);
  	vq->heads = NULL;
  }
  
  /* Helper to allocate iovec buffers for all vqs. */
  static long vhost_dev_alloc_iovecs(struct vhost_dev *dev)
  {
  	struct vhost_virtqueue *vq;
  	int i;
  
  	for (i = 0; i < dev->nvqs; ++i) {
  		vq = dev->vqs[i];
  		vq->indirect = kmalloc_array(UIO_MAXIOV,
  					     sizeof(*vq->indirect),
  					     GFP_KERNEL);
  		vq->log = kmalloc_array(dev->iov_limit, sizeof(*vq->log),
  					GFP_KERNEL);
  		vq->heads = kmalloc_array(dev->iov_limit, sizeof(*vq->heads),
  					  GFP_KERNEL);
  		if (!vq->indirect || !vq->log || !vq->heads)
  			goto err_nomem;
  	}
  	return 0;
  
  err_nomem:
  	for (; i >= 0; --i)
  		vhost_vq_free_iovecs(dev->vqs[i]);
  	return -ENOMEM;
  }
  
  static void vhost_dev_free_iovecs(struct vhost_dev *dev)
  {
  	int i;
  
  	for (i = 0; i < dev->nvqs; ++i)
  		vhost_vq_free_iovecs(dev->vqs[i]);
  }
  
  void vhost_dev_init(struct vhost_dev *dev,
  		    struct vhost_virtqueue **vqs, int nvqs, int iov_limit)
  {
  	struct vhost_virtqueue *vq;
  	int i;
  
  	dev->vqs = vqs;
  	dev->nvqs = nvqs;
  	mutex_init(&dev->mutex);
  	dev->log_ctx = NULL;
  	dev->umem = NULL;
  	dev->iotlb = NULL;
  	dev->mm = NULL;
  	dev->worker = NULL;
  	dev->iov_limit = iov_limit;
  	init_llist_head(&dev->work_list);
  	init_waitqueue_head(&dev->wait);
  	INIT_LIST_HEAD(&dev->read_list);
  	INIT_LIST_HEAD(&dev->pending_list);
  	spin_lock_init(&dev->iotlb_lock);
  
  
  	for (i = 0; i < dev->nvqs; ++i) {
  		vq = dev->vqs[i];
  		vq->log = NULL;
  		vq->indirect = NULL;
  		vq->heads = NULL;
  		vq->dev = dev;
  		mutex_init(&vq->mutex);
  		vhost_vq_reset(dev, vq);
  		if (vq->handle_kick)
  			vhost_poll_init(&vq->poll, vq->handle_kick,
  					EPOLLIN, dev);
  	}
  }
  EXPORT_SYMBOL_GPL(vhost_dev_init);
  
  /* Caller should have device mutex */
  long vhost_dev_check_owner(struct vhost_dev *dev)
  {
  	/* Are you the owner? If not, I don't think you mean to do that */
  	return dev->mm == current->mm ? 0 : -EPERM;
  }
  EXPORT_SYMBOL_GPL(vhost_dev_check_owner);
  
  struct vhost_attach_cgroups_struct {
  	struct vhost_work work;
  	struct task_struct *owner;
  	int ret;
  };
  
  static void vhost_attach_cgroups_work(struct vhost_work *work)
  {
  	struct vhost_attach_cgroups_struct *s;
  
  	s = container_of(work, struct vhost_attach_cgroups_struct, work);
  	s->ret = cgroup_attach_task_all(s->owner, current);
  }
  
  static int vhost_attach_cgroups(struct vhost_dev *dev)
  {
  	struct vhost_attach_cgroups_struct attach;
  
  	attach.owner = current;
  	vhost_work_init(&attach.work, vhost_attach_cgroups_work);
  	vhost_work_queue(dev, &attach.work);
  	vhost_work_flush(dev, &attach.work);
  	return attach.ret;
  }
  
  /* Caller should have device mutex */
  bool vhost_dev_has_owner(struct vhost_dev *dev)
  {
  	return dev->mm;
  }
  EXPORT_SYMBOL_GPL(vhost_dev_has_owner);
  
  /* Caller should have device mutex */
  long vhost_dev_set_owner(struct vhost_dev *dev)
  {
  	struct task_struct *worker;
  	int err;
  
  	/* Is there an owner already? */
  	if (vhost_dev_has_owner(dev)) {
  		err = -EBUSY;
  		goto err_mm;
  	}
  
  	/* No owner, become one */
  	dev->mm = get_task_mm(current);
  	worker = kthread_create(vhost_worker, dev, "vhost-%d", current->pid);
  	if (IS_ERR(worker)) {
  		err = PTR_ERR(worker);
  		goto err_worker;
  	}
  
  	dev->worker = worker;
  	wake_up_process(worker);	/* avoid contributing to loadavg */
  
  	err = vhost_attach_cgroups(dev);
  	if (err)
  		goto err_cgroup;
  
  	err = vhost_dev_alloc_iovecs(dev);
  	if (err)
  		goto err_cgroup;
  
  	return 0;
  err_cgroup:
  	kthread_stop(worker);
  	dev->worker = NULL;
  err_worker:
  	if (dev->mm)
  		mmput(dev->mm);
  	dev->mm = NULL;
  err_mm:
  	return err;
  }
  EXPORT_SYMBOL_GPL(vhost_dev_set_owner);
  
  struct vhost_umem *vhost_dev_reset_owner_prepare(void)
  {
  	return kvzalloc(sizeof(struct vhost_umem), GFP_KERNEL);
  }
  EXPORT_SYMBOL_GPL(vhost_dev_reset_owner_prepare);
  
  /* Caller should have device mutex */
  void vhost_dev_reset_owner(struct vhost_dev *dev, struct vhost_umem *umem)
  {
  	int i;
  
  	vhost_dev_cleanup(dev);
  
  	/* Restore memory to default empty mapping. */
  	INIT_LIST_HEAD(&umem->umem_list);
  	dev->umem = umem;
  	/* We don't need VQ locks below since vhost_dev_cleanup makes sure
  	 * VQs aren't running.
  	 */
  	for (i = 0; i < dev->nvqs; ++i)
  		dev->vqs[i]->umem = umem;
  }
  EXPORT_SYMBOL_GPL(vhost_dev_reset_owner);
  
  void vhost_dev_stop(struct vhost_dev *dev)
  {
  	int i;
  
  	for (i = 0; i < dev->nvqs; ++i) {
  		if (dev->vqs[i]->kick && dev->vqs[i]->handle_kick) {
  			vhost_poll_stop(&dev->vqs[i]->poll);
  			vhost_poll_flush(&dev->vqs[i]->poll);
  		}
  	}
  }
  EXPORT_SYMBOL_GPL(vhost_dev_stop);
  
  static void vhost_umem_free(struct vhost_umem *umem,
  			    struct vhost_umem_node *node)
  {
  	vhost_umem_interval_tree_remove(node, &umem->umem_tree);
  	list_del(&node->link);
  	kfree(node);
  	umem->numem--;
  }
  
  static void vhost_umem_clean(struct vhost_umem *umem)
  {
  	struct vhost_umem_node *node, *tmp;
  
  	if (!umem)
  		return;
  
  	list_for_each_entry_safe(node, tmp, &umem->umem_list, link)
  		vhost_umem_free(umem, node);
  
  	kvfree(umem);
  }
  
  static void vhost_clear_msg(struct vhost_dev *dev)
  {
  	struct vhost_msg_node *node, *n;
  
  	spin_lock(&dev->iotlb_lock);
  
  	list_for_each_entry_safe(node, n, &dev->read_list, node) {
  		list_del(&node->node);
  		kfree(node);
  	}
  
  	list_for_each_entry_safe(node, n, &dev->pending_list, node) {
  		list_del(&node->node);
  		kfree(node);
  	}
  
  	spin_unlock(&dev->iotlb_lock);
  }
  
  void vhost_dev_cleanup(struct vhost_dev *dev)
  {
  	int i;
  
  	for (i = 0; i < dev->nvqs; ++i) {
  		if (dev->vqs[i]->error_ctx)
  			eventfd_ctx_put(dev->vqs[i]->error_ctx);
  		if (dev->vqs[i]->kick)
  			fput(dev->vqs[i]->kick);
  		if (dev->vqs[i]->call_ctx)
  			eventfd_ctx_put(dev->vqs[i]->call_ctx);
  		vhost_vq_reset(dev, dev->vqs[i]);
  	}
  	vhost_dev_free_iovecs(dev);
  	if (dev->log_ctx)
  		eventfd_ctx_put(dev->log_ctx);
  	dev->log_ctx = NULL;
  	/* No one will access memory at this point */
  	vhost_umem_clean(dev->umem);
  	dev->umem = NULL;
  	vhost_umem_clean(dev->iotlb);
  	dev->iotlb = NULL;
  	vhost_clear_msg(dev);
  	wake_up_interruptible_poll(&dev->wait, EPOLLIN | EPOLLRDNORM);
  	WARN_ON(!llist_empty(&dev->work_list));
  	if (dev->worker) {
  		kthread_stop(dev->worker);
  		dev->worker = NULL;
  	}
  	if (dev->mm)
  		mmput(dev->mm);
  	dev->mm = NULL;
  }
  EXPORT_SYMBOL_GPL(vhost_dev_cleanup);
  
  static bool log_access_ok(void __user *log_base, u64 addr, unsigned long sz)
  {
  	u64 a = addr / VHOST_PAGE_SIZE / 8;
  
  	/* Make sure 64 bit math will not overflow. */
  	if (a > ULONG_MAX - (unsigned long)log_base ||
  	    a + (unsigned long)log_base > ULONG_MAX)
  		return false;
  
  	return access_ok(log_base + a,
  			 (sz + VHOST_PAGE_SIZE * 8 - 1) / VHOST_PAGE_SIZE / 8);
  }
  
  static bool vhost_overflow(u64 uaddr, u64 size)
  {
  	/* Make sure 64 bit math will not overflow. */
  	return uaddr > ULONG_MAX || size > ULONG_MAX || uaddr > ULONG_MAX - size;
  }
  
  /* Caller should have vq mutex and device mutex. */
  static bool vq_memory_access_ok(void __user *log_base, struct vhost_umem *umem,
  				int log_all)
  {
  	struct vhost_umem_node *node;
  
  	if (!umem)
  		return false;
  
  	list_for_each_entry(node, &umem->umem_list, link) {
  		unsigned long a = node->userspace_addr;
  
  		if (vhost_overflow(node->userspace_addr, node->size))
  			return false;
  
  
  		if (!access_ok((void __user *)a,
  				    node->size))
  			return false;
  		else if (log_all && !log_access_ok(log_base,
  						   node->start,
  						   node->size))
  			return false;
  	}
  	return true;
  }
  
  static inline void __user *vhost_vq_meta_fetch(struct vhost_virtqueue *vq,
  					       u64 addr, unsigned int size,
  					       int type)
  {
  	const struct vhost_umem_node *node = vq->meta_iotlb[type];
  
  	if (!node)
  		return NULL;
  
  	return (void *)(uintptr_t)(node->userspace_addr + addr - node->start);
  }
  
  /* Can we switch to this memory table? */
  /* Caller should have device mutex but not vq mutex */
  static bool memory_access_ok(struct vhost_dev *d, struct vhost_umem *umem,
  			     int log_all)
  {
  	int i;
  
  	for (i = 0; i < d->nvqs; ++i) {
  		bool ok;
  		bool log;
  
  		mutex_lock(&d->vqs[i]->mutex);
  		log = log_all || vhost_has_feature(d->vqs[i], VHOST_F_LOG_ALL);
  		/* If ring is inactive, will check when it's enabled. */
  		if (d->vqs[i]->private_data)
  			ok = vq_memory_access_ok(d->vqs[i]->log_base,
  						 umem, log);
  		else
  			ok = true;
  		mutex_unlock(&d->vqs[i]->mutex);
  		if (!ok)
  			return false;
  	}
  	return true;
  }
  
  static int translate_desc(struct vhost_virtqueue *vq, u64 addr, u32 len,
  			  struct iovec iov[], int iov_size, int access);
  
  static int vhost_copy_to_user(struct vhost_virtqueue *vq, void __user *to,
  			      const void *from, unsigned size)
  {
  	int ret;
  
  	if (!vq->iotlb)
  		return __copy_to_user(to, from, size);
  	else {
  		/* This function should be called after iotlb
  		 * prefetch, which means we're sure that all vq
  		 * could be access through iotlb. So -EAGAIN should
  		 * not happen in this case.
  		 */
  		struct iov_iter t;
  		void __user *uaddr = vhost_vq_meta_fetch(vq,
  				     (u64)(uintptr_t)to, size,
  				     VHOST_ADDR_USED);
  
  		if (uaddr)
  			return __copy_to_user(uaddr, from, size);
  
  		ret = translate_desc(vq, (u64)(uintptr_t)to, size, vq->iotlb_iov,
  				     ARRAY_SIZE(vq->iotlb_iov),
  				     VHOST_ACCESS_WO);
  		if (ret < 0)
  			goto out;
  		iov_iter_init(&t, WRITE, vq->iotlb_iov, ret, size);
  		ret = copy_to_iter(from, size, &t);
  		if (ret == size)
  			ret = 0;
  	}
  out:
  	return ret;
  }
  
  static int vhost_copy_from_user(struct vhost_virtqueue *vq, void *to,
  				void __user *from, unsigned size)
  {
  	int ret;
  
  	if (!vq->iotlb)
  		return __copy_from_user(to, from, size);
  	else {
  		/* This function should be called after iotlb
  		 * prefetch, which means we're sure that vq
  		 * could be access through iotlb. So -EAGAIN should
  		 * not happen in this case.
  		 */
  		void __user *uaddr = vhost_vq_meta_fetch(vq,
  				     (u64)(uintptr_t)from, size,
  				     VHOST_ADDR_DESC);
  		struct iov_iter f;
  
  		if (uaddr)
  			return __copy_from_user(to, uaddr, size);
  
  		ret = translate_desc(vq, (u64)(uintptr_t)from, size, vq->iotlb_iov,
  				     ARRAY_SIZE(vq->iotlb_iov),
  				     VHOST_ACCESS_RO);
  		if (ret < 0) {
  			vq_err(vq, "IOTLB translation failure: uaddr "
  			       "%p size 0x%llx\n", from,
  			       (unsigned long long) size);
  			goto out;
  		}
  		iov_iter_init(&f, READ, vq->iotlb_iov, ret, size);
  		ret = copy_from_iter(to, size, &f);
  		if (ret == size)
  			ret = 0;
  	}
  
  out:
  	return ret;
  }
  
  static void __user *__vhost_get_user_slow(struct vhost_virtqueue *vq,
  					  void __user *addr, unsigned int size,
  					  int type)
  {
  	int ret;
  
  	ret = translate_desc(vq, (u64)(uintptr_t)addr, size, vq->iotlb_iov,
  			     ARRAY_SIZE(vq->iotlb_iov),
  			     VHOST_ACCESS_RO);
  	if (ret < 0) {
  		vq_err(vq, "IOTLB translation failure: uaddr "
  			"%p size 0x%llx\n", addr,
  			(unsigned long long) size);
  		return NULL;
  	}
  
  	if (ret != 1 || vq->iotlb_iov[0].iov_len != size) {
  		vq_err(vq, "Non atomic userspace memory access: uaddr "
  			"%p size 0x%llx\n", addr,
  			(unsigned long long) size);
  		return NULL;
  	}
  
  	return vq->iotlb_iov[0].iov_base;
  }
  
  /* This function should be called after iotlb
   * prefetch, which means we're sure that vq
   * could be access through iotlb. So -EAGAIN should
   * not happen in this case.
   */
  static inline void __user *__vhost_get_user(struct vhost_virtqueue *vq,
  					    void *addr, unsigned int size,
  					    int type)
  {
  	void __user *uaddr = vhost_vq_meta_fetch(vq,
  			     (u64)(uintptr_t)addr, size, type);
  	if (uaddr)
  		return uaddr;
  
  	return __vhost_get_user_slow(vq, addr, size, type);
  }
  
  #define vhost_put_user(vq, x, ptr)		\
  ({ \
  	int ret = -EFAULT; \
  	if (!vq->iotlb) { \
  		ret = __put_user(x, ptr); \
  	} else { \
  		__typeof__(ptr) to = \
  			(__typeof__(ptr)) __vhost_get_user(vq, ptr,	\
  					  sizeof(*ptr), VHOST_ADDR_USED); \
  		if (to != NULL) \
  			ret = __put_user(x, to); \
  		else \
  			ret = -EFAULT;	\
  	} \
  	ret; \
  })
  
  #define vhost_get_user(vq, x, ptr, type)		\
  ({ \
  	int ret; \
  	if (!vq->iotlb) { \
  		ret = __get_user(x, ptr); \
  	} else { \
  		__typeof__(ptr) from = \
  			(__typeof__(ptr)) __vhost_get_user(vq, ptr, \
  							   sizeof(*ptr), \
  							   type); \
  		if (from != NULL) \
  			ret = __get_user(x, from); \
  		else \
  			ret = -EFAULT; \
  	} \
  	ret; \
  })
  
  #define vhost_get_avail(vq, x, ptr) \
  	vhost_get_user(vq, x, ptr, VHOST_ADDR_AVAIL)
  
  #define vhost_get_used(vq, x, ptr) \
  	vhost_get_user(vq, x, ptr, VHOST_ADDR_USED)
  
  static void vhost_dev_lock_vqs(struct vhost_dev *d)
  {
  	int i = 0;
  	for (i = 0; i < d->nvqs; ++i)
  		mutex_lock_nested(&d->vqs[i]->mutex, i);
  }
  
  static void vhost_dev_unlock_vqs(struct vhost_dev *d)
  {
  	int i = 0;
  	for (i = 0; i < d->nvqs; ++i)
  		mutex_unlock(&d->vqs[i]->mutex);
  }
  
  static int vhost_new_umem_range(struct vhost_umem *umem,
  				u64 start, u64 size, u64 end,
  				u64 userspace_addr, int perm)
  {
  	struct vhost_umem_node *tmp, *node;
  
  	if (!size)
  		return -EFAULT;
  
  	node = kmalloc(sizeof(*node), GFP_ATOMIC);
  	if (!node)
  		return -ENOMEM;
  
  	if (umem->numem == max_iotlb_entries) {
  		tmp = list_first_entry(&umem->umem_list, typeof(*tmp), link);
  		vhost_umem_free(umem, tmp);
  	}
  
  	node->start = start;
  	node->size = size;
  	node->last = end;
  	node->userspace_addr = userspace_addr;
  	node->perm = perm;
  	INIT_LIST_HEAD(&node->link);
  	list_add_tail(&node->link, &umem->umem_list);
  	vhost_umem_interval_tree_insert(node, &umem->umem_tree);
  	umem->numem++;
  
  	return 0;
  }
  
  static void vhost_del_umem_range(struct vhost_umem *umem,
  				 u64 start, u64 end)
  {
  	struct vhost_umem_node *node;
  
  	while ((node = vhost_umem_interval_tree_iter_first(&umem->umem_tree,
  							   start, end)))
  		vhost_umem_free(umem, node);
  }
  
  static void vhost_iotlb_notify_vq(struct vhost_dev *d,
  				  struct vhost_iotlb_msg *msg)
  {
  	struct vhost_msg_node *node, *n;
  
  	spin_lock(&d->iotlb_lock);
  
  	list_for_each_entry_safe(node, n, &d->pending_list, node) {
  		struct vhost_iotlb_msg *vq_msg = &node->msg.iotlb;
  		if (msg->iova <= vq_msg->iova &&
  		    msg->iova + msg->size - 1 >= vq_msg->iova &&
  		    vq_msg->type == VHOST_IOTLB_MISS) {
  			vhost_poll_queue(&node->vq->poll);
  			list_del(&node->node);
  			kfree(node);
  		}
  	}
  
  	spin_unlock(&d->iotlb_lock);
  }
  
  static bool umem_access_ok(u64 uaddr, u64 size, int access)
  {
  	unsigned long a = uaddr;
  
  	/* Make sure 64 bit math will not overflow. */
  	if (vhost_overflow(uaddr, size))
  		return false;
  
  	if ((access & VHOST_ACCESS_RO) &&
  	    !access_ok((void __user *)a, size))
  		return false;
  	if ((access & VHOST_ACCESS_WO) &&
  	    !access_ok((void __user *)a, size))
  		return false;
  	return true;
  }
  
  static int vhost_process_iotlb_msg(struct vhost_dev *dev,
  				   struct vhost_iotlb_msg *msg)
  {
  	int ret = 0;
  
  	mutex_lock(&dev->mutex);
  	vhost_dev_lock_vqs(dev);
  	switch (msg->type) {
  	case VHOST_IOTLB_UPDATE:
  		if (!dev->iotlb) {
  			ret = -EFAULT;
  			break;
  		}
  		if (!umem_access_ok(msg->uaddr, msg->size, msg->perm)) {
  			ret = -EFAULT;
  			break;
  		}
  		vhost_vq_meta_reset(dev);
  		if (vhost_new_umem_range(dev->iotlb, msg->iova, msg->size,
  					 msg->iova + msg->size - 1,
  					 msg->uaddr, msg->perm)) {
  			ret = -ENOMEM;
  			break;
  		}
  		vhost_iotlb_notify_vq(dev, msg);
  		break;
  	case VHOST_IOTLB_INVALIDATE:
  		if (!dev->iotlb) {
  			ret = -EFAULT;
  			break;
  		}
  		vhost_vq_meta_reset(dev);
  		vhost_del_umem_range(dev->iotlb, msg->iova,
  				     msg->iova + msg->size - 1);
  		break;
  	default:
  		ret = -EINVAL;
  		break;
  	}
  
  	vhost_dev_unlock_vqs(dev);
  	mutex_unlock(&dev->mutex);
  
  	return ret;
  }
  ssize_t vhost_chr_write_iter(struct vhost_dev *dev,
  			     struct iov_iter *from)
  {
  	struct vhost_iotlb_msg msg;
  	size_t offset;
  	int type, ret;
  
  	ret = copy_from_iter(&type, sizeof(type), from);
  	if (ret != sizeof(type)) {
  		ret = -EINVAL;
  		goto done;
  	}
  
  	switch (type) {
  	case VHOST_IOTLB_MSG:
  		/* There maybe a hole after type for V1 message type,
  		 * so skip it here.
  		 */
  		offset = offsetof(struct vhost_msg, iotlb) - sizeof(int);
  		break;
  	case VHOST_IOTLB_MSG_V2:
  		offset = sizeof(__u32);
  		break;
  	default:
  		ret = -EINVAL;
  		goto done;
  	}
  
  	iov_iter_advance(from, offset);
  	ret = copy_from_iter(&msg, sizeof(msg), from);
  	if (ret != sizeof(msg)) {
  		ret = -EINVAL;
  		goto done;
  	}
  	if (vhost_process_iotlb_msg(dev, &msg)) {
  		ret = -EFAULT;
  		goto done;
  	}
  
  	ret = (type == VHOST_IOTLB_MSG) ? sizeof(struct vhost_msg) :
  	      sizeof(struct vhost_msg_v2);
  done:
  	return ret;
  }
  EXPORT_SYMBOL(vhost_chr_write_iter);
  
  __poll_t vhost_chr_poll(struct file *file, struct vhost_dev *dev,
  			    poll_table *wait)
  {
  	__poll_t mask = 0;
  
  	poll_wait(file, &dev->wait, wait);
  
  	if (!list_empty(&dev->read_list))
  		mask |= EPOLLIN | EPOLLRDNORM;
  
  	return mask;
  }
  EXPORT_SYMBOL(vhost_chr_poll);
  
  ssize_t vhost_chr_read_iter(struct vhost_dev *dev, struct iov_iter *to,
  			    int noblock)
  {
  	DEFINE_WAIT(wait);
  	struct vhost_msg_node *node;
  	ssize_t ret = 0;
  	unsigned size = sizeof(struct vhost_msg);
  
  	if (iov_iter_count(to) < size)
  		return 0;
  
  	while (1) {
  		if (!noblock)
  			prepare_to_wait(&dev->wait, &wait,
  					TASK_INTERRUPTIBLE);
  
  		node = vhost_dequeue_msg(dev, &dev->read_list);
  		if (node)
  			break;
  		if (noblock) {
  			ret = -EAGAIN;
  			break;
  		}
  		if (signal_pending(current)) {
  			ret = -ERESTARTSYS;
  			break;
  		}
  		if (!dev->iotlb) {
  			ret = -EBADFD;
  			break;
  		}
  
  		schedule();
  	}
  
  	if (!noblock)
  		finish_wait(&dev->wait, &wait);
  
  	if (node) {
  		struct vhost_iotlb_msg *msg;
  		void *start = &node->msg;
  
  		switch (node->msg.type) {
  		case VHOST_IOTLB_MSG:
  			size = sizeof(node->msg);
  			msg = &node->msg.iotlb;
  			break;
  		case VHOST_IOTLB_MSG_V2:
  			size = sizeof(node->msg_v2);
  			msg = &node->msg_v2.iotlb;
  			break;
  		default:
  			BUG();
  			break;
  		}
  
  		ret = copy_to_iter(start, size, to);
  		if (ret != size || msg->type != VHOST_IOTLB_MISS) {
  			kfree(node);
  			return ret;
  		}
  		vhost_enqueue_msg(dev, &dev->pending_list, node);
  	}
  
  	return ret;
  }
  EXPORT_SYMBOL_GPL(vhost_chr_read_iter);
  
  static int vhost_iotlb_miss(struct vhost_virtqueue *vq, u64 iova, int access)
  {
  	struct vhost_dev *dev = vq->dev;
  	struct vhost_msg_node *node;
  	struct vhost_iotlb_msg *msg;
  	bool v2 = vhost_backend_has_feature(vq, VHOST_BACKEND_F_IOTLB_MSG_V2);
  
  	node = vhost_new_msg(vq, v2 ? VHOST_IOTLB_MSG_V2 : VHOST_IOTLB_MSG);
  	if (!node)
  		return -ENOMEM;
  
  	if (v2) {
  		node->msg_v2.type = VHOST_IOTLB_MSG_V2;
  		msg = &node->msg_v2.iotlb;
  	} else {
  		msg = &node->msg.iotlb;
  	}
  
  	msg->type = VHOST_IOTLB_MISS;
  	msg->iova = iova;
  	msg->perm = access;
  
  	vhost_enqueue_msg(dev, &dev->read_list, node);
  
  	return 0;
  }
  
  static bool vq_access_ok(struct vhost_virtqueue *vq, unsigned int num,
  			 struct vring_desc __user *desc,
  			 struct vring_avail __user *avail,
  			 struct vring_used __user *used)
  
  {
  	size_t s __maybe_unused = vhost_has_feature(vq, VIRTIO_RING_F_EVENT_IDX) ? 2 : 0;
  
  	return access_ok(desc, num * sizeof *desc) &&
  	       access_ok(avail,
  			 sizeof *avail + num * sizeof *avail->ring + s) &&
  	       access_ok(used,
  			sizeof *used + num * sizeof *used->ring + s);
  }
  
  static void vhost_vq_meta_update(struct vhost_virtqueue *vq,
  				 const struct vhost_umem_node *node,
  				 int type)
  {
  	int access = (type == VHOST_ADDR_USED) ?
  		     VHOST_ACCESS_WO : VHOST_ACCESS_RO;
  
  	if (likely(node->perm & access))
  		vq->meta_iotlb[type] = node;
  }
  
  static bool iotlb_access_ok(struct vhost_virtqueue *vq,
  			    int access, u64 addr, u64 len, int type)
  {
  	const struct vhost_umem_node *node;
  	struct vhost_umem *umem = vq->iotlb;
  	u64 s = 0, size, orig_addr = addr, last = addr + len - 1;
  
  	if (vhost_vq_meta_fetch(vq, addr, len, type))
  		return true;
  
  	while (len > s) {
  		node = vhost_umem_interval_tree_iter_first(&umem->umem_tree,
  							   addr,
  							   last);
  		if (node == NULL || node->start > addr) {
  			vhost_iotlb_miss(vq, addr, access);
  			return false;
  		} else if (!(node->perm & access)) {
  			/* Report the possible access violation by
  			 * request another translation from userspace.
  			 */
  			return false;
  		}
  
  		size = node->size - addr + node->start;
  
  		if (orig_addr == addr && size >= len)
  			vhost_vq_meta_update(vq, node, type);
  
  		s += size;
  		addr += size;
  	}
  
  	return true;
  }
  
  int vq_iotlb_prefetch(struct vhost_virtqueue *vq)
  {
  	size_t s = vhost_has_feature(vq, VIRTIO_RING_F_EVENT_IDX) ? 2 : 0;
  	unsigned int num = vq->num;
  
  	if (!vq->iotlb)
  		return 1;
  
  	return iotlb_access_ok(vq, VHOST_ACCESS_RO, (u64)(uintptr_t)vq->desc,
  			       num * sizeof(*vq->desc), VHOST_ADDR_DESC) &&
  	       iotlb_access_ok(vq, VHOST_ACCESS_RO, (u64)(uintptr_t)vq->avail,
  			       sizeof *vq->avail +
  			       num * sizeof(*vq->avail->ring) + s,
  			       VHOST_ADDR_AVAIL) &&
  	       iotlb_access_ok(vq, VHOST_ACCESS_WO, (u64)(uintptr_t)vq->used,
  			       sizeof *vq->used +
  			       num * sizeof(*vq->used->ring) + s,
  			       VHOST_ADDR_USED);
  }
  EXPORT_SYMBOL_GPL(vq_iotlb_prefetch);
  
  /* Can we log writes? */
  /* Caller should have device mutex but not vq mutex */
  bool vhost_log_access_ok(struct vhost_dev *dev)
  {
  	return memory_access_ok(dev, dev->umem, 1);
  }
  EXPORT_SYMBOL_GPL(vhost_log_access_ok);
  
  /* Verify access for write logging. */
  /* Caller should have vq mutex and device mutex */
  static bool vq_log_access_ok(struct vhost_virtqueue *vq,
  			     void __user *log_base)
  {
  	size_t s = vhost_has_feature(vq, VIRTIO_RING_F_EVENT_IDX) ? 2 : 0;
  
  	return vq_memory_access_ok(log_base, vq->umem,
  				   vhost_has_feature(vq, VHOST_F_LOG_ALL)) &&
  		(!vq->log_used || log_access_ok(log_base, vq->log_addr,
  					sizeof *vq->used +
  					vq->num * sizeof *vq->used->ring + s));
  }
  
  /* Can we start vq? */
  /* Caller should have vq mutex and device mutex */
  bool vhost_vq_access_ok(struct vhost_virtqueue *vq)
  {
  	if (!vq_log_access_ok(vq, vq->log_base))
  		return false;
  
  	/* Access validation occurs at prefetch time with IOTLB */
  	if (vq->iotlb)
  		return true;
  
  	return vq_access_ok(vq, vq->num, vq->desc, vq->avail, vq->used);
  }
  EXPORT_SYMBOL_GPL(vhost_vq_access_ok);
  
  static struct vhost_umem *vhost_umem_alloc(void)
  {
  	struct vhost_umem *umem = kvzalloc(sizeof(*umem), GFP_KERNEL);
  
  	if (!umem)
  		return NULL;
  
  	umem->umem_tree = RB_ROOT_CACHED;
  	umem->numem = 0;
  	INIT_LIST_HEAD(&umem->umem_list);
  
  	return umem;
  }
  
  static long vhost_set_memory(struct vhost_dev *d, struct vhost_memory __user *m)
  {
  	struct vhost_memory mem, *newmem;
  	struct vhost_memory_region *region;
  	struct vhost_umem *newumem, *oldumem;
  	unsigned long size = offsetof(struct vhost_memory, regions);
  	int i;
  
  	if (copy_from_user(&mem, m, size))
  		return -EFAULT;
  	if (mem.padding)
  		return -EOPNOTSUPP;
  	if (mem.nregions > max_mem_regions)
  		return -E2BIG;
  	newmem = kvzalloc(struct_size(newmem, regions, mem.nregions),
  			GFP_KERNEL);
  	if (!newmem)
  		return -ENOMEM;
  
  	memcpy(newmem, &mem, size);
  	if (copy_from_user(newmem->regions, m->regions,
  			   mem.nregions * sizeof *m->regions)) {
  		kvfree(newmem);
  		return -EFAULT;
  	}
  
  	newumem = vhost_umem_alloc();
  	if (!newumem) {
  		kvfree(newmem);
  		return -ENOMEM;
  	}
  
  	for (region = newmem->regions;
  	     region < newmem->regions + mem.nregions;
  	     region++) {
  		if (vhost_new_umem_range(newumem,
  					 region->guest_phys_addr,
  					 region->memory_size,
  					 region->guest_phys_addr +
  					 region->memory_size - 1,
  					 region->userspace_addr,
  					 VHOST_ACCESS_RW))
  			goto err;
  	}
  
  	if (!memory_access_ok(d, newumem, 0))
  		goto err;
  
  	oldumem = d->umem;
  	d->umem = newumem;
  
  	/* All memory accesses are done under some VQ mutex. */
  	for (i = 0; i < d->nvqs; ++i) {
  		mutex_lock(&d->vqs[i]->mutex);
  		d->vqs[i]->umem = newumem;
  		mutex_unlock(&d->vqs[i]->mutex);
  	}
  
  	kvfree(newmem);
  	vhost_umem_clean(oldumem);
  	return 0;
  
  err:
  	vhost_umem_clean(newumem);
  	kvfree(newmem);
  	return -EFAULT;
  }
  
  long vhost_vring_ioctl(struct vhost_dev *d, unsigned int ioctl, void __user *argp)
  {
  	struct file *eventfp, *filep = NULL;
  	bool pollstart = false, pollstop = false;
  	struct eventfd_ctx *ctx = NULL;
  	u32 __user *idxp = argp;
  	struct vhost_virtqueue *vq;
  	struct vhost_vring_state s;
  	struct vhost_vring_file f;
  	struct vhost_vring_addr a;
  	u32 idx;
  	long r;
  
  	r = get_user(idx, idxp);
  	if (r < 0)
  		return r;
  	if (idx >= d->nvqs)
  		return -ENOBUFS;
  
  	idx = array_index_nospec(idx, d->nvqs);
  	vq = d->vqs[idx];
  
  	mutex_lock(&vq->mutex);
  
  	switch (ioctl) {
  	case VHOST_SET_VRING_NUM:
  		/* Resizing ring with an active backend?
  		 * You don't want to do that. */
  		if (vq->private_data) {
  			r = -EBUSY;
  			break;
  		}
  		if (copy_from_user(&s, argp, sizeof s)) {
  			r = -EFAULT;
  			break;
  		}
  		if (!s.num || s.num > 0xffff || (s.num & (s.num - 1))) {
  			r = -EINVAL;
  			break;
  		}
  		vq->num = s.num;
  		break;
  	case VHOST_SET_VRING_BASE:
  		/* Moving base with an active backend?
  		 * You don't want to do that. */
  		if (vq->private_data) {
  			r = -EBUSY;
  			break;
  		}
  		if (copy_from_user(&s, argp, sizeof s)) {
  			r = -EFAULT;
  			break;
  		}
  		if (s.num > 0xffff) {
  			r = -EINVAL;
  			break;
  		}
  		vq->last_avail_idx = s.num;
  		/* Forget the cached index value. */
  		vq->avail_idx = vq->last_avail_idx;
  		break;
  	case VHOST_GET_VRING_BASE:
  		s.index = idx;
  		s.num = vq->last_avail_idx;
  		if (copy_to_user(argp, &s, sizeof s))
  			r = -EFAULT;
  		break;
  	case VHOST_SET_VRING_ADDR:
  		if (copy_from_user(&a, argp, sizeof a)) {
  			r = -EFAULT;
  			break;
  		}
  		if (a.flags & ~(0x1 << VHOST_VRING_F_LOG)) {
  			r = -EOPNOTSUPP;
  			break;
  		}
  		/* For 32bit, verify that the top 32bits of the user
  		   data are set to zero. */
  		if ((u64)(unsigned long)a.desc_user_addr != a.desc_user_addr ||
  		    (u64)(unsigned long)a.used_user_addr != a.used_user_addr ||
  		    (u64)(unsigned long)a.avail_user_addr != a.avail_user_addr) {
  			r = -EFAULT;
  			break;
  		}
  
  		/* Make sure it's safe to cast pointers to vring types. */
  		BUILD_BUG_ON(__alignof__ *vq->avail > VRING_AVAIL_ALIGN_SIZE);
  		BUILD_BUG_ON(__alignof__ *vq->used > VRING_USED_ALIGN_SIZE);
  		if ((a.avail_user_addr & (VRING_AVAIL_ALIGN_SIZE - 1)) ||
  		    (a.used_user_addr & (VRING_USED_ALIGN_SIZE - 1)) ||
  		    (a.log_guest_addr & (VRING_USED_ALIGN_SIZE - 1))) {
  			r = -EINVAL;
  			break;
  		}
  
  		/* We only verify access here if backend is configured.
  		 * If it is not, we don't as size might not have been setup.
  		 * We will verify when backend is configured. */
  		if (vq->private_data) {
  			if (!vq_access_ok(vq, vq->num,
  				(void __user *)(unsigned long)a.desc_user_addr,
  				(void __user *)(unsigned long)a.avail_user_addr,
  				(void __user *)(unsigned long)a.used_user_addr)) {
  				r = -EINVAL;
  				break;
  			}
  
  			/* Also validate log access for used ring if enabled. */
  			if ((a.flags & (0x1 << VHOST_VRING_F_LOG)) &&
  			    !log_access_ok(vq->log_base, a.log_guest_addr,
  					   sizeof *vq->used +
  					   vq->num * sizeof *vq->used->ring)) {
  				r = -EINVAL;
  				break;
  			}
  		}
  
  		vq->log_used = !!(a.flags & (0x1 << VHOST_VRING_F_LOG));
  		vq->desc = (void __user *)(unsigned long)a.desc_user_addr;
  		vq->avail = (void __user *)(unsigned long)a.avail_user_addr;
  		vq->log_addr = a.log_guest_addr;
  		vq->used = (void __user *)(unsigned long)a.used_user_addr;
  		break;
  	case VHOST_SET_VRING_KICK:
  		if (copy_from_user(&f, argp, sizeof f)) {
  			r = -EFAULT;
  			break;
  		}
  		eventfp = f.fd == -1 ? NULL : eventfd_fget(f.fd);
  		if (IS_ERR(eventfp)) {
  			r = PTR_ERR(eventfp);
  			break;
  		}
  		if (eventfp != vq->kick) {
  			pollstop = (filep = vq->kick) != NULL;
  			pollstart = (vq->kick = eventfp) != NULL;
  		} else
  			filep = eventfp;
  		break;
  	case VHOST_SET_VRING_CALL:
  		if (copy_from_user(&f, argp, sizeof f)) {
  			r = -EFAULT;
  			break;
  		}
  		ctx = f.fd == -1 ? NULL : eventfd_ctx_fdget(f.fd);
  		if (IS_ERR(ctx)) {
  			r = PTR_ERR(ctx);
  			break;
  		}
  		swap(ctx, vq->call_ctx);
  		break;
  	case VHOST_SET_VRING_ERR:
  		if (copy_from_user(&f, argp, sizeof f)) {
  			r = -EFAULT;
  			break;
  		}
  		ctx = f.fd == -1 ? NULL : eventfd_ctx_fdget(f.fd);
  		if (IS_ERR(ctx)) {
  			r = PTR_ERR(ctx);
  			break;
  		}
  		swap(ctx, vq->error_ctx);
  		break;
  	case VHOST_SET_VRING_ENDIAN:
  		r = vhost_set_vring_endian(vq, argp);
  		break;
  	case VHOST_GET_VRING_ENDIAN:
  		r = vhost_get_vring_endian(vq, idx, argp);
  		break;
  	case VHOST_SET_VRING_BUSYLOOP_TIMEOUT:
  		if (copy_from_user(&s, argp, sizeof(s))) {
  			r = -EFAULT;
  			break;
  		}
  		vq->busyloop_timeout = s.num;
  		break;
  	case VHOST_GET_VRING_BUSYLOOP_TIMEOUT:
  		s.index = idx;
  		s.num = vq->busyloop_timeout;
  		if (copy_to_user(argp, &s, sizeof(s)))
  			r = -EFAULT;
  		break;
  	default:
  		r = -ENOIOCTLCMD;
  	}
  
  	if (pollstop && vq->handle_kick)
  		vhost_poll_stop(&vq->poll);
  
  	if (!IS_ERR_OR_NULL(ctx))
  		eventfd_ctx_put(ctx);
  	if (filep)
  		fput(filep);
  
  	if (pollstart && vq->handle_kick)
  		r = vhost_poll_start(&vq->poll, vq->kick);
  
  	mutex_unlock(&vq->mutex);
  
  	if (pollstop && vq->handle_kick)
  		vhost_poll_flush(&vq->poll);
  	return r;
  }
  EXPORT_SYMBOL_GPL(vhost_vring_ioctl);
  
  int vhost_init_device_iotlb(struct vhost_dev *d, bool enabled)
  {
  	struct vhost_umem *niotlb, *oiotlb;
  	int i;
  
  	niotlb = vhost_umem_alloc();
  	if (!niotlb)
  		return -ENOMEM;
  
  	oiotlb = d->iotlb;
  	d->iotlb = niotlb;
  
  	for (i = 0; i < d->nvqs; ++i) {
  		struct vhost_virtqueue *vq = d->vqs[i];
  
  		mutex_lock(&vq->mutex);
  		vq->iotlb = niotlb;
  		__vhost_vq_meta_reset(vq);
  		mutex_unlock(&vq->mutex);
  	}
  
  	vhost_umem_clean(oiotlb);
  
  	return 0;
  }
  EXPORT_SYMBOL_GPL(vhost_init_device_iotlb);
  
  /* Caller must have device mutex */
  long vhost_dev_ioctl(struct vhost_dev *d, unsigned int ioctl, void __user *argp)
  {
  	struct eventfd_ctx *ctx;
  	u64 p;
  	long r;
  	int i, fd;
  
  	/* If you are not the owner, you can become one */
  	if (ioctl == VHOST_SET_OWNER) {
  		r = vhost_dev_set_owner(d);
  		goto done;
  	}
  
  	/* You must be the owner to do anything else */
  	r = vhost_dev_check_owner(d);
  	if (r)
  		goto done;
  
  	switch (ioctl) {
  	case VHOST_SET_MEM_TABLE:
  		r = vhost_set_memory(d, argp);
  		break;
  	case VHOST_SET_LOG_BASE:
  		if (copy_from_user(&p, argp, sizeof p)) {
  			r = -EFAULT;
  			break;
  		}
  		if ((u64)(unsigned long)p != p) {
  			r = -EFAULT;
  			break;
  		}
  		for (i = 0; i < d->nvqs; ++i) {
  			struct vhost_virtqueue *vq;
  			void __user *base = (void __user *)(unsigned long)p;
  			vq = d->vqs[i];
  			mutex_lock(&vq->mutex);
  			/* If ring is inactive, will check when it's enabled. */
  			if (vq->private_data && !vq_log_access_ok(vq, base))
  				r = -EFAULT;
  			else
  				vq->log_base = base;
  			mutex_unlock(&vq->mutex);
  		}
  		break;
  	case VHOST_SET_LOG_FD:
  		r = get_user(fd, (int __user *)argp);
  		if (r < 0)
  			break;
  		ctx = fd == -1 ? NULL : eventfd_ctx_fdget(fd);
  		if (IS_ERR(ctx)) {
  			r = PTR_ERR(ctx);
  			break;
  		}
  		swap(ctx, d->log_ctx);
  		for (i = 0; i < d->nvqs; ++i) {
  			mutex_lock(&d->vqs[i]->mutex);
  			d->vqs[i]->log_ctx = d->log_ctx;
  			mutex_unlock(&d->vqs[i]->mutex);
  		}
  		if (ctx)
  			eventfd_ctx_put(ctx);
  		break;
  	default:
  		r = -ENOIOCTLCMD;
  		break;
  	}
  done:
  	return r;
  }
  EXPORT_SYMBOL_GPL(vhost_dev_ioctl);
  
  /* TODO: This is really inefficient.  We need something like get_user()
   * (instruction directly accesses the data, with an exception table entry
   * returning -EFAULT). See Documentation/x86/exception-tables.txt.
   */
  static int set_bit_to_user(int nr, void __user *addr)
  {
  	unsigned long log = (unsigned long)addr;
  	struct page *page;
  	void *base;
  	int bit = nr + (log % PAGE_SIZE) * 8;
  	int r;
  
  	r = get_user_pages_fast(log, 1, 1, &page);
  	if (r < 0)
  		return r;
  	BUG_ON(r != 1);
  	base = kmap_atomic(page);
  	set_bit(bit, base);
  	kunmap_atomic(base);
  	set_page_dirty_lock(page);
  	put_page(page);
  	return 0;
  }
  
  static int log_write(void __user *log_base,
  		     u64 write_address, u64 write_length)
  {
  	u64 write_page = write_address / VHOST_PAGE_SIZE;
  	int r;
  
  	if (!write_length)
  		return 0;
  	write_length += write_address % VHOST_PAGE_SIZE;
  	for (;;) {
  		u64 base = (u64)(unsigned long)log_base;
  		u64 log = base + write_page / 8;
  		int bit = write_page % 8;
  		if ((u64)(unsigned long)log != log)
  			return -EFAULT;
  		r = set_bit_to_user(bit, (void __user *)(unsigned long)log);
  		if (r < 0)
  			return r;
  		if (write_length <= VHOST_PAGE_SIZE)
  			break;
  		write_length -= VHOST_PAGE_SIZE;
  		write_page += 1;
  	}
  	return r;
  }
  
  static int log_write_hva(struct vhost_virtqueue *vq, u64 hva, u64 len)
  {
  	struct vhost_umem *umem = vq->umem;
  	struct vhost_umem_node *u;
  	u64 start, end, l, min;
  	int r;
  	bool hit = false;
  
  	while (len) {
  		min = len;
  		/* More than one GPAs can be mapped into a single HVA. So
  		 * iterate all possible umems here to be safe.
  		 */
  		list_for_each_entry(u, &umem->umem_list, link) {
  			if (u->userspace_addr > hva - 1 + len ||
  			    u->userspace_addr - 1 + u->size < hva)
  				continue;
  			start = max(u->userspace_addr, hva);
  			end = min(u->userspace_addr - 1 + u->size,
  				  hva - 1 + len);
  			l = end - start + 1;
  			r = log_write(vq->log_base,
  				      u->start + start - u->userspace_addr,
  				      l);
  			if (r < 0)
  				return r;
  			hit = true;
  			min = min(l, min);
  		}
  
  		if (!hit)
  			return -EFAULT;
  
  		len -= min;
  		hva += min;
  	}
  
  	return 0;
  }
  
  static int log_used(struct vhost_virtqueue *vq, u64 used_offset, u64 len)
  {
  	struct iovec iov[64];
  	int i, ret;
  
  	if (!vq->iotlb)
  		return log_write(vq->log_base, vq->log_addr + used_offset, len);
  
  	ret = translate_desc(vq, (uintptr_t)vq->used + used_offset,
  			     len, iov, 64, VHOST_ACCESS_WO);
  	if (ret < 0)
  		return ret;
  
  	for (i = 0; i < ret; i++) {
  		ret = log_write_hva(vq,	(uintptr_t)iov[i].iov_base,
  				    iov[i].iov_len);
  		if (ret)
  			return ret;
  	}
  
  	return 0;
  }
  
  int vhost_log_write(struct vhost_virtqueue *vq, struct vhost_log *log,
  		    unsigned int log_num, u64 len, struct iovec *iov, int count)
  {
  	int i, r;
  
  	/* Make sure data written is seen before log. */
  	smp_wmb();
  
  	if (vq->iotlb) {
  		for (i = 0; i < count; i++) {
  			r = log_write_hva(vq, (uintptr_t)iov[i].iov_base,
  					  iov[i].iov_len);
  			if (r < 0)
  				return r;
  		}
  		return 0;
  	}
  
  	for (i = 0; i < log_num; ++i) {
  		u64 l = min(log[i].len, len);
  		r = log_write(vq->log_base, log[i].addr, l);
  		if (r < 0)
  			return r;
  		len -= l;
  		if (!len) {
  			if (vq->log_ctx)
  				eventfd_signal(vq->log_ctx, 1);
  			return 0;
  		}
  	}
  	/* Length written exceeds what we have stored. This is a bug. */
  	BUG();
  	return 0;
  }
  EXPORT_SYMBOL_GPL(vhost_log_write);
  
  static int vhost_update_used_flags(struct vhost_virtqueue *vq)
  {
  	void __user *used;
  	if (vhost_put_user(vq, cpu_to_vhost16(vq, vq->used_flags),
  			   &vq->used->flags) < 0)
  		return -EFAULT;
  	if (unlikely(vq->log_used)) {
  		/* Make sure the flag is seen before log. */
  		smp_wmb();
  		/* Log used flag write. */
  		used = &vq->used->flags;
  		log_used(vq, (used - (void __user *)vq->used),
  			 sizeof vq->used->flags);
  		if (vq->log_ctx)
  			eventfd_signal(vq->log_ctx, 1);
  	}
  	return 0;
  }
  
  static int vhost_update_avail_event(struct vhost_virtqueue *vq, u16 avail_event)
  {
  	if (vhost_put_user(vq, cpu_to_vhost16(vq, vq->avail_idx),
  			   vhost_avail_event(vq)))
  		return -EFAULT;
  	if (unlikely(vq->log_used)) {
  		void __user *used;
  		/* Make sure the event is seen before log. */
  		smp_wmb();
  		/* Log avail event write */
  		used = vhost_avail_event(vq);
  		log_used(vq, (used - (void __user *)vq->used),
  			 sizeof *vhost_avail_event(vq));
  		if (vq->log_ctx)
  			eventfd_signal(vq->log_ctx, 1);
  	}
  	return 0;
  }
  
  int vhost_vq_init_access(struct vhost_virtqueue *vq)
  {
  	__virtio16 last_used_idx;
  	int r;
  	bool is_le = vq->is_le;
  
  	if (!vq->private_data)
  		return 0;
  
  	vhost_init_is_le(vq);
  
  	r = vhost_update_used_flags(vq);
  	if (r)
  		goto err;
  	vq->signalled_used_valid = false;
  	if (!vq->iotlb &&
  	    !access_ok(&vq->used->idx, sizeof vq->used->idx)) {
  		r = -EFAULT;
  		goto err;
  	}
  	r = vhost_get_used(vq, last_used_idx, &vq->used->idx);
  	if (r) {
  		vq_err(vq, "Can't access used idx at %p\n",
  		       &vq->used->idx);
  		goto err;
  	}
  	vq->last_used_idx = vhost16_to_cpu(vq, last_used_idx);
  	return 0;
  
  err:
  	vq->is_le = is_le;
  	return r;
  }
  EXPORT_SYMBOL_GPL(vhost_vq_init_access);
  
  static int translate_desc(struct vhost_virtqueue *vq, u64 addr, u32 len,
  			  struct iovec iov[], int iov_size, int access)
  {
  	const struct vhost_umem_node *node;
  	struct vhost_dev *dev = vq->dev;
  	struct vhost_umem *umem = dev->iotlb ? dev->iotlb : dev->umem;
  	struct iovec *_iov;
  	u64 s = 0;
  	int ret = 0;
  
  	while ((u64)len > s) {
  		u64 size;
  		if (unlikely(ret >= iov_size)) {
  			ret = -ENOBUFS;
  			break;
  		}
  
  		node = vhost_umem_interval_tree_iter_first(&umem->umem_tree,
  							addr, addr + len - 1);
  		if (node == NULL || node->start > addr) {
  			if (umem != dev->iotlb) {
  				ret = -EFAULT;
  				break;
  			}
  			ret = -EAGAIN;
  			break;
  		} else if (!(node->perm & access)) {
  			ret = -EPERM;
  			break;
  		}
  
  		_iov = iov + ret;
  		size = node->size - addr + node->start;
  		_iov->iov_len = min((u64)len - s, size);
  		_iov->iov_base = (void __user *)(unsigned long)
  			(node->userspace_addr + addr - node->start);
  		s += size;
  		addr += size;
  		++ret;
  	}
  
  	if (ret == -EAGAIN)
  		vhost_iotlb_miss(vq, addr, access);
  	return ret;
  }
  
  /* Each buffer in the virtqueues is actually a chain of descriptors.  This
   * function returns the next descriptor in the chain,
   * or -1U if we're at the end. */
  static unsigned next_desc(struct vhost_virtqueue *vq, struct vring_desc *desc)
  {
  	unsigned int next;
  
  	/* If this descriptor says it doesn't chain, we're done. */
  	if (!(desc->flags & cpu_to_vhost16(vq, VRING_DESC_F_NEXT)))
  		return -1U;
  
  	/* Check they're not leading us off end of descriptors. */
  	next = vhost16_to_cpu(vq, READ_ONCE(desc->next));
  	return next;
  }
  
  static int get_indirect(struct vhost_virtqueue *vq,
  			struct iovec iov[], unsigned int iov_size,
  			unsigned int *out_num, unsigned int *in_num,
  			struct vhost_log *log, unsigned int *log_num,
  			struct vring_desc *indirect)
  {
  	struct vring_desc desc;
  	unsigned int i = 0, count, found = 0;
  	u32 len = vhost32_to_cpu(vq, indirect->len);
  	struct iov_iter from;
  	int ret, access;
  
  	/* Sanity check */
  	if (unlikely(len % sizeof desc)) {
  		vq_err(vq, "Invalid length in indirect descriptor: "
  		       "len 0x%llx not multiple of 0x%zx\n",
  		       (unsigned long long)len,
  		       sizeof desc);
  		return -EINVAL;
  	}
  
  	ret = translate_desc(vq, vhost64_to_cpu(vq, indirect->addr), len, vq->indirect,
  			     UIO_MAXIOV, VHOST_ACCESS_RO);
  	if (unlikely(ret < 0)) {
  		if (ret != -EAGAIN)
  			vq_err(vq, "Translation failure %d in indirect.\n", ret);
  		return ret;
  	}
  	iov_iter_init(&from, READ, vq->indirect, ret, len);
  
  	/* We will use the result as an address to read from, so most
  	 * architectures only need a compiler barrier here. */
  	read_barrier_depends();
  
  	count = len / sizeof desc;
  	/* Buffers are chained via a 16 bit next field, so
  	 * we can have at most 2^16 of these. */
  	if (unlikely(count > USHRT_MAX + 1)) {
  		vq_err(vq, "Indirect buffer length too big: %d\n",
  		       indirect->len);
  		return -E2BIG;
  	}
  
  	do {
  		unsigned iov_count = *in_num + *out_num;
  		if (unlikely(++found > count)) {
  			vq_err(vq, "Loop detected: last one at %u "
  			       "indirect size %u\n",
  			       i, count);
  			return -EINVAL;
  		}
  		if (unlikely(!copy_from_iter_full(&desc, sizeof(desc), &from))) {
  			vq_err(vq, "Failed indirect descriptor: idx %d, %zx\n",
  			       i, (size_t)vhost64_to_cpu(vq, indirect->addr) + i * sizeof desc);
  			return -EINVAL;
  		}
  		if (unlikely(desc.flags & cpu_to_vhost16(vq, VRING_DESC_F_INDIRECT))) {
  			vq_err(vq, "Nested indirect descriptor: idx %d, %zx\n",
  			       i, (size_t)vhost64_to_cpu(vq, indirect->addr) + i * sizeof desc);
  			return -EINVAL;
  		}
  
  		if (desc.flags & cpu_to_vhost16(vq, VRING_DESC_F_WRITE))
  			access = VHOST_ACCESS_WO;
  		else
  			access = VHOST_ACCESS_RO;
  
  		ret = translate_desc(vq, vhost64_to_cpu(vq, desc.addr),
  				     vhost32_to_cpu(vq, desc.len), iov + iov_count,
  				     iov_size - iov_count, access);
  		if (unlikely(ret < 0)) {
  			if (ret != -EAGAIN)
  				vq_err(vq, "Translation failure %d indirect idx %d\n",
  					ret, i);
  			return ret;
  		}
  		/* If this is an input descriptor, increment that count. */
  		if (access == VHOST_ACCESS_WO) {
  			*in_num += ret;
  			if (unlikely(log)) {
  				log[*log_num].addr = vhost64_to_cpu(vq, desc.addr);
  				log[*log_num].len = vhost32_to_cpu(vq, desc.len);
  				++*log_num;
  			}
  		} else {
  			/* If it's an output descriptor, they're all supposed
  			 * to come before any input descriptors. */
  			if (unlikely(*in_num)) {
  				vq_err(vq, "Indirect descriptor "
  				       "has out after in: idx %d\n", i);
  				return -EINVAL;
  			}
  			*out_num += ret;
  		}
  	} while ((i = next_desc(vq, &desc)) != -1);
  	return 0;
  }
  
  /* This looks in the virtqueue and for the first available buffer, and converts
   * it to an iovec for convenient access.  Since descriptors consist of some
   * number of output then some number of input descriptors, it's actually two
   * iovecs, but we pack them into one and note how many of each there were.
   *
   * This function returns the descriptor number found, or vq->num (which is
   * never a valid descriptor number) if none was found.  A negative code is
   * returned on error. */
  int vhost_get_vq_desc(struct vhost_virtqueue *vq,
  		      struct iovec iov[], unsigned int iov_size,
  		      unsigned int *out_num, unsigned int *in_num,
  		      struct vhost_log *log, unsigned int *log_num)
  {
  	struct vring_desc desc;
  	unsigned int i, head, found = 0;
  	u16 last_avail_idx;
  	__virtio16 avail_idx;
  	__virtio16 ring_head;
  	int ret, access;
  
  	/* Check it isn't doing very strange things with descriptor numbers. */
  	last_avail_idx = vq->last_avail_idx;
  
  	if (vq->avail_idx == vq->last_avail_idx) {
  		if (unlikely(vhost_get_avail(vq, avail_idx, &vq->avail->idx))) {
  			vq_err(vq, "Failed to access avail idx at %p\n",
  				&vq->avail->idx);
  			return -EFAULT;
  		}
  		vq->avail_idx = vhost16_to_cpu(vq, avail_idx);
  
  		if (unlikely((u16)(vq->avail_idx - last_avail_idx) > vq->num)) {
  			vq_err(vq, "Guest moved used index from %u to %u",
  				last_avail_idx, vq->avail_idx);
  			return -EFAULT;
  		}
  
  		/* If there's nothing new since last we looked, return
  		 * invalid.
  		 */
  		if (vq->avail_idx == last_avail_idx)
  			return vq->num;
  
  		/* Only get avail ring entries after they have been
  		 * exposed by guest.
  		 */
  		smp_rmb();
  	}
  
  	/* Grab the next descriptor number they're advertising, and increment
  	 * the index we've seen. */
  	if (unlikely(vhost_get_avail(vq, ring_head,
  		     &vq->avail->ring[last_avail_idx & (vq->num - 1)]))) {
  		vq_err(vq, "Failed to read head: idx %d address %p\n",
  		       last_avail_idx,
  		       &vq->avail->ring[last_avail_idx % vq->num]);
  		return -EFAULT;
  	}
  
  	head = vhost16_to_cpu(vq, ring_head);
  
  	/* If their number is silly, that's an error. */
  	if (unlikely(head >= vq->num)) {
  		vq_err(vq, "Guest says index %u > %u is available",
  		       head, vq->num);
  		return -EINVAL;
  	}
  
  	/* When we start there are none of either input nor output. */
  	*out_num = *in_num = 0;
  	if (unlikely(log))
  		*log_num = 0;
  
  	i = head;
  	do {
  		unsigned iov_count = *in_num + *out_num;
  		if (unlikely(i >= vq->num)) {
  			vq_err(vq, "Desc index is %u > %u, head = %u",
  			       i, vq->num, head);
  			return -EINVAL;
  		}
  		if (unlikely(++found > vq->num)) {
  			vq_err(vq, "Loop detected: last one at %u "
  			       "vq size %u head %u\n",
  			       i, vq->num, head);
  			return -EINVAL;
  		}
  		ret = vhost_copy_from_user(vq, &desc, vq->desc + i,
  					   sizeof desc);
  		if (unlikely(ret)) {
  			vq_err(vq, "Failed to get descriptor: idx %d addr %p\n",
  			       i, vq->desc + i);
  			return -EFAULT;
  		}
  		if (desc.flags & cpu_to_vhost16(vq, VRING_DESC_F_INDIRECT)) {
  			ret = get_indirect(vq, iov, iov_size,
  					   out_num, in_num,
  					   log, log_num, &desc);
  			if (unlikely(ret < 0)) {
  				if (ret != -EAGAIN)
  					vq_err(vq, "Failure detected "
  						"in indirect descriptor at idx %d\n", i);
  				return ret;
  			}
  			continue;
  		}
  
  		if (desc.flags & cpu_to_vhost16(vq, VRING_DESC_F_WRITE))
  			access = VHOST_ACCESS_WO;
  		else
  			access = VHOST_ACCESS_RO;
  		ret = translate_desc(vq, vhost64_to_cpu(vq, desc.addr),
  				     vhost32_to_cpu(vq, desc.len), iov + iov_count,
  				     iov_size - iov_count, access);
  		if (unlikely(ret < 0)) {
  			if (ret != -EAGAIN)
  				vq_err(vq, "Translation failure %d descriptor idx %d\n",
  					ret, i);
  			return ret;
  		}
  		if (access == VHOST_ACCESS_WO) {
  			/* If this is an input descriptor,
  			 * increment that count. */
  			*in_num += ret;
  			if (unlikely(log)) {
  				log[*log_num].addr = vhost64_to_cpu(vq, desc.addr);
  				log[*log_num].len = vhost32_to_cpu(vq, desc.len);
  				++*log_num;
  			}
  		} else {
  			/* If it's an output descriptor, they're all supposed
  			 * to come before any input descriptors. */
  			if (unlikely(*in_num)) {
  				vq_err(vq, "Descriptor has out after in: "
  				       "idx %d\n", i);
  				return -EINVAL;
  			}
  			*out_num += ret;
  		}
  	} while ((i = next_desc(vq, &desc)) != -1);
  
  	/* On success, increment avail index. */
  	vq->last_avail_idx++;
  
  	/* Assume notifications from guest are disabled at this point,
  	 * if they aren't we would need to update avail_event index. */
  	BUG_ON(!(vq->used_flags & VRING_USED_F_NO_NOTIFY));
  	return head;
  }
  EXPORT_SYMBOL_GPL(vhost_get_vq_desc);
  
  /* Reverse the effect of vhost_get_vq_desc. Useful for error handling. */
  void vhost_discard_vq_desc(struct vhost_virtqueue *vq, int n)
  {
  	vq->last_avail_idx -= n;
  }
  EXPORT_SYMBOL_GPL(vhost_discard_vq_desc);
  
  /* After we've used one of their buffers, we tell them about it.  We'll then
   * want to notify the guest, using eventfd. */
  int vhost_add_used(struct vhost_virtqueue *vq, unsigned int head, int len)
  {
  	struct vring_used_elem heads = {
  		cpu_to_vhost32(vq, head),
  		cpu_to_vhost32(vq, len)
  	};
  
  	return vhost_add_used_n(vq, &heads, 1);
  }
  EXPORT_SYMBOL_GPL(vhost_add_used);
  
  static int __vhost_add_used_n(struct vhost_virtqueue *vq,
  			    struct vring_used_elem *heads,
  			    unsigned count)
  {
  	struct vring_used_elem __user *used;
  	u16 old, new;
  	int start;
  
  	start = vq->last_used_idx & (vq->num - 1);
  	used = vq->used->ring + start;
  	if (count == 1) {
  		if (vhost_put_user(vq, heads[0].id, &used->id)) {
  			vq_err(vq, "Failed to write used id");
  			return -EFAULT;
  		}
  		if (vhost_put_user(vq, heads[0].len, &used->len)) {
  			vq_err(vq, "Failed to write used len");
  			return -EFAULT;
  		}
  	} else if (vhost_copy_to_user(vq, used, heads, count * sizeof *used)) {
  		vq_err(vq, "Failed to write used");
  		return -EFAULT;
  	}
  	if (unlikely(vq->log_used)) {
  		/* Make sure data is seen before log. */
  		smp_wmb();
  		/* Log used ring entry write. */
  		log_used(vq, ((void __user *)used - (void __user *)vq->used),
  			 count * sizeof *used);
  	}
  	old = vq->last_used_idx;
  	new = (vq->last_used_idx += count);
  	/* If the driver never bothers to signal in a very long while,
  	 * used index might wrap around. If that happens, invalidate
  	 * signalled_used index we stored. TODO: make sure driver
  	 * signals at least once in 2^16 and remove this. */
  	if (unlikely((u16)(new - vq->signalled_used) < (u16)(new - old)))
  		vq->signalled_used_valid = false;
  	return 0;
  }
  
  /* After we've used one of their buffers, we tell them about it.  We'll then
   * want to notify the guest, using eventfd. */
  int vhost_add_used_n(struct vhost_virtqueue *vq, struct vring_used_elem *heads,
  		     unsigned count)
  {
  	int start, n, r;
  
  	start = vq->last_used_idx & (vq->num - 1);
  	n = vq->num - start;
  	if (n < count) {
  		r = __vhost_add_used_n(vq, heads, n);
  		if (r < 0)
  			return r;
  		heads += n;
  		count -= n;
  	}
  	r = __vhost_add_used_n(vq, heads, count);
  
  	/* Make sure buffer is written before we update index. */
  	smp_wmb();
  	if (vhost_put_user(vq, cpu_to_vhost16(vq, vq->last_used_idx),
  			   &vq->used->idx)) {
  		vq_err(vq, "Failed to increment used idx");
  		return -EFAULT;
  	}
  	if (unlikely(vq->log_used)) {
  		/* Make sure used idx is seen before log. */
  		smp_wmb();
  		/* Log used index update. */
  		log_used(vq, offsetof(struct vring_used, idx),
  			 sizeof vq->used->idx);
  		if (vq->log_ctx)
  			eventfd_signal(vq->log_ctx, 1);
  	}
  	return r;
  }
  EXPORT_SYMBOL_GPL(vhost_add_used_n);
  
  static bool vhost_notify(struct vhost_dev *dev, struct vhost_virtqueue *vq)
  {
  	__u16 old, new;
  	__virtio16 event;
  	bool v;
  	/* Flush out used index updates. This is paired
  	 * with the barrier that the Guest executes when enabling
  	 * interrupts. */
  	smp_mb();
  
  	if (vhost_has_feature(vq, VIRTIO_F_NOTIFY_ON_EMPTY) &&
  	    unlikely(vq->avail_idx == vq->last_avail_idx))
  		return true;
  
  	if (!vhost_has_feature(vq, VIRTIO_RING_F_EVENT_IDX)) {
  		__virtio16 flags;
  		if (vhost_get_avail(vq, flags, &vq->avail->flags)) {
  			vq_err(vq, "Failed to get flags");
  			return true;
  		}
  		return !(flags & cpu_to_vhost16(vq, VRING_AVAIL_F_NO_INTERRUPT));
  	}
  	old = vq->signalled_used;
  	v = vq->signalled_used_valid;
  	new = vq->signalled_used = vq->last_used_idx;
  	vq->signalled_used_valid = true;
  
  	if (unlikely(!v))
  		return true;
  
  	if (vhost_get_avail(vq, event, vhost_used_event(vq))) {
  		vq_err(vq, "Failed to get used event idx");
  		return true;
  	}
  	return vring_need_event(vhost16_to_cpu(vq, event), new, old);
  }
  
  /* This actually signals the guest, using eventfd. */
  void vhost_signal(struct vhost_dev *dev, struct vhost_virtqueue *vq)
  {
  	/* Signal the Guest tell them we used something up. */
  	if (vq->call_ctx && vhost_notify(dev, vq))
  		eventfd_signal(vq->call_ctx, 1);
  }
  EXPORT_SYMBOL_GPL(vhost_signal);
  
  /* And here's the combo meal deal.  Supersize me! */
  void vhost_add_used_and_signal(struct vhost_dev *dev,
  			       struct vhost_virtqueue *vq,
  			       unsigned int head, int len)
  {
  	vhost_add_used(vq, head, len);
  	vhost_signal(dev, vq);
  }
  EXPORT_SYMBOL_GPL(vhost_add_used_and_signal);
  
  /* multi-buffer version of vhost_add_used_and_signal */
  void vhost_add_used_and_signal_n(struct vhost_dev *dev,
  				 struct vhost_virtqueue *vq,
  				 struct vring_used_elem *heads, unsigned count)
  {
  	vhost_add_used_n(vq, heads, count);
  	vhost_signal(dev, vq);
  }
  EXPORT_SYMBOL_GPL(vhost_add_used_and_signal_n);
  
  /* return true if we're sure that avaiable ring is empty */
  bool vhost_vq_avail_empty(struct vhost_dev *dev, struct vhost_virtqueue *vq)
  {
  	__virtio16 avail_idx;
  	int r;
  
  	if (vq->avail_idx != vq->last_avail_idx)
  		return false;
  
  	r = vhost_get_avail(vq, avail_idx, &vq->avail->idx);
  	if (unlikely(r))
  		return false;
  	vq->avail_idx = vhost16_to_cpu(vq, avail_idx);
  
  	return vq->avail_idx == vq->last_avail_idx;
  }
  EXPORT_SYMBOL_GPL(vhost_vq_avail_empty);
  
  /* OK, now we need to know about added descriptors. */
  bool vhost_enable_notify(struct vhost_dev *dev, struct vhost_virtqueue *vq)
  {
  	__virtio16 avail_idx;
  	int r;
  
  	if (!(vq->used_flags & VRING_USED_F_NO_NOTIFY))
  		return false;
  	vq->used_flags &= ~VRING_USED_F_NO_NOTIFY;
  	if (!vhost_has_feature(vq, VIRTIO_RING_F_EVENT_IDX)) {
  		r = vhost_update_used_flags(vq);
  		if (r) {
  			vq_err(vq, "Failed to enable notification at %p: %d\n",
  			       &vq->used->flags, r);
  			return false;
  		}
  	} else {
  		r = vhost_update_avail_event(vq, vq->avail_idx);
  		if (r) {
  			vq_err(vq, "Failed to update avail event index at %p: %d\n",
  			       vhost_avail_event(vq), r);
  			return false;
  		}
  	}
  	/* They could have slipped one in as we were doing that: make
  	 * sure it's written, then check again. */
  	smp_mb();
  	r = vhost_get_avail(vq, avail_idx, &vq->avail->idx);
  	if (r) {
  		vq_err(vq, "Failed to check avail idx at %p: %d\n",
  		       &vq->avail->idx, r);
  		return false;
  	}
  
  	return vhost16_to_cpu(vq, avail_idx) != vq->avail_idx;
  }
  EXPORT_SYMBOL_GPL(vhost_enable_notify);
  
  /* We don't need to be notified again. */
  void vhost_disable_notify(struct vhost_dev *dev, struct vhost_virtqueue *vq)
  {
  	int r;
  
  	if (vq->used_flags & VRING_USED_F_NO_NOTIFY)
  		return;
  	vq->used_flags |= VRING_USED_F_NO_NOTIFY;
  	if (!vhost_has_feature(vq, VIRTIO_RING_F_EVENT_IDX)) {
  		r = vhost_update_used_flags(vq);
  		if (r)
  			vq_err(vq, "Failed to enable notification at %p: %d\n",
  			       &vq->used->flags, r);
  	}
  }
  EXPORT_SYMBOL_GPL(vhost_disable_notify);
  
  /* Create a new message. */
  struct vhost_msg_node *vhost_new_msg(struct vhost_virtqueue *vq, int type)
  {
  	struct vhost_msg_node *node = kmalloc(sizeof *node, GFP_KERNEL);
  	if (!node)
  		return NULL;
  
  	/* Make sure all padding within the structure is initialized. */
  	memset(&node->msg, 0, sizeof node->msg);
  	node->vq = vq;
  	node->msg.type = type;
  	return node;
  }
  EXPORT_SYMBOL_GPL(vhost_new_msg);
  
  void vhost_enqueue_msg(struct vhost_dev *dev, struct list_head *head,
  		       struct vhost_msg_node *node)
  {
  	spin_lock(&dev->iotlb_lock);
  	list_add_tail(&node->node, head);
  	spin_unlock(&dev->iotlb_lock);
  
  	wake_up_interruptible_poll(&dev->wait, EPOLLIN | EPOLLRDNORM);
  }
  EXPORT_SYMBOL_GPL(vhost_enqueue_msg);
  
  struct vhost_msg_node *vhost_dequeue_msg(struct vhost_dev *dev,
  					 struct list_head *head)
  {
  	struct vhost_msg_node *node = NULL;
  
  	spin_lock(&dev->iotlb_lock);
  	if (!list_empty(head)) {
  		node = list_first_entry(head, struct vhost_msg_node,
  					node);
  		list_del(&node->node);
  	}
  	spin_unlock(&dev->iotlb_lock);
  
  	return node;
  }
  EXPORT_SYMBOL_GPL(vhost_dequeue_msg);
  
  
  static int __init vhost_init(void)
  {
  	return 0;
  }
  
  static void __exit vhost_exit(void)
  {
  }
  
  module_init(vhost_init);
  module_exit(vhost_exit);
  
  MODULE_VERSION("0.0.1");
  MODULE_LICENSE("GPL v2");
  MODULE_AUTHOR("Michael S. Tsirkin");
  MODULE_DESCRIPTION("Host kernel accelerator for virtio");
  