vhost.c 39.6 KB
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/* 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
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 * Documentation/virtual/lguest/lguest.c, by Rusty Russell
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 *
 * 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/virtio_net.h>
#include <linux/mm.h>
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#include <linux/mmu_context.h>
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#include <linux/miscdevice.h>
#include <linux/mutex.h>
#include <linux/rcupdate.h>
#include <linux/poll.h>
#include <linux/file.h>
#include <linux/highmem.h>
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#include <linux/slab.h>
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#include <linux/kthread.h>
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#include <linux/cgroup.h>
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#include "vhost.h"

enum {
	VHOST_MEMORY_MAX_NREGIONS = 64,
	VHOST_MEMORY_F_LOG = 0x1,
};

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static unsigned vhost_zcopy_mask __read_mostly;

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#define vhost_used_event(vq) ((u16 __user *)&vq->avail->ring[vq->num])
#define vhost_avail_event(vq) ((u16 __user *)&vq->used->ring[vq->num])

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static void vhost_poll_func(struct file *file, wait_queue_head_t *wqh,
			    poll_table *pt)
{
	struct vhost_poll *poll;

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	poll = container_of(pt, struct vhost_poll, table);
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	poll->wqh = wqh;
	add_wait_queue(wqh, &poll->wait);
}

static int vhost_poll_wakeup(wait_queue_t *wait, unsigned mode, int sync,
			     void *key)
{
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	struct vhost_poll *poll = container_of(wait, struct vhost_poll, wait);

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	if (!((unsigned long)key & poll->mask))
		return 0;

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	vhost_poll_queue(poll);
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	return 0;
}

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void vhost_work_init(struct vhost_work *work, vhost_work_fn_t fn)
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{
	INIT_LIST_HEAD(&work->node);
	work->fn = fn;
	init_waitqueue_head(&work->done);
	work->flushing = 0;
	work->queue_seq = work->done_seq = 0;
}

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/* Init poll structure */
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void vhost_poll_init(struct vhost_poll *poll, vhost_work_fn_t fn,
		     unsigned long mask, struct vhost_dev *dev)
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{
	init_waitqueue_func_entry(&poll->wait, vhost_poll_wakeup);
	init_poll_funcptr(&poll->table, vhost_poll_func);
	poll->mask = mask;
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	poll->dev = dev;

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	vhost_work_init(&poll->work, fn);
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}

/* 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. */
void vhost_poll_start(struct vhost_poll *poll, struct file *file)
{
	unsigned long mask;
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	mask = file->f_op->poll(file, &poll->table);
	if (mask)
		vhost_poll_wakeup(&poll->wait, 0, 0, (void *)mask);
}

/* 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)
{
	remove_wait_queue(poll->wqh, &poll->wait);
}

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static bool vhost_work_seq_done(struct vhost_dev *dev, struct vhost_work *work,
				unsigned seq)
{
	int left;
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	spin_lock_irq(&dev->work_lock);
	left = seq - work->done_seq;
	spin_unlock_irq(&dev->work_lock);
	return left <= 0;
}

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static void vhost_work_flush(struct vhost_dev *dev, struct vhost_work *work)
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{
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	unsigned seq;
	int flushing;

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	spin_lock_irq(&dev->work_lock);
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	seq = work->queue_seq;
	work->flushing++;
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	spin_unlock_irq(&dev->work_lock);
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	wait_event(work->done, vhost_work_seq_done(dev, work, seq));
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	spin_lock_irq(&dev->work_lock);
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	flushing = --work->flushing;
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	spin_unlock_irq(&dev->work_lock);
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	BUG_ON(flushing < 0);
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}

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/* 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);
}

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void vhost_work_queue(struct vhost_dev *dev, struct vhost_work *work)
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{
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	unsigned long flags;

	spin_lock_irqsave(&dev->work_lock, flags);
	if (list_empty(&work->node)) {
		list_add_tail(&work->node, &dev->work_list);
		work->queue_seq++;
		wake_up_process(dev->worker);
	}
	spin_unlock_irqrestore(&dev->work_lock, flags);
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}

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void vhost_poll_queue(struct vhost_poll *poll)
{
	vhost_work_queue(poll->dev, &poll->work);
}

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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;
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	vq->signalled_used = 0;
	vq->signalled_used_valid = false;
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	vq->used_flags = 0;
	vq->log_used = false;
	vq->log_addr = -1ull;
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	vq->vhost_hlen = 0;
	vq->sock_hlen = 0;
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	vq->private_data = NULL;
	vq->log_base = NULL;
	vq->error_ctx = NULL;
	vq->error = NULL;
	vq->kick = NULL;
	vq->call_ctx = NULL;
	vq->call = NULL;
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	vq->log_ctx = NULL;
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	vq->upend_idx = 0;
	vq->done_idx = 0;
	vq->ubufs = NULL;
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}

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static int vhost_worker(void *data)
{
	struct vhost_dev *dev = data;
	struct vhost_work *work = NULL;
	unsigned uninitialized_var(seq);
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	mm_segment_t oldfs = get_fs();
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	set_fs(USER_DS);
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	use_mm(dev->mm);

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	for (;;) {
		/* mb paired w/ kthread_stop */
		set_current_state(TASK_INTERRUPTIBLE);

		spin_lock_irq(&dev->work_lock);
		if (work) {
			work->done_seq = seq;
			if (work->flushing)
				wake_up_all(&work->done);
		}

		if (kthread_should_stop()) {
			spin_unlock_irq(&dev->work_lock);
			__set_current_state(TASK_RUNNING);
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			break;
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		}
		if (!list_empty(&dev->work_list)) {
			work = list_first_entry(&dev->work_list,
						struct vhost_work, node);
			list_del_init(&work->node);
			seq = work->queue_seq;
		} else
			work = NULL;
		spin_unlock_irq(&dev->work_lock);

		if (work) {
			__set_current_state(TASK_RUNNING);
			work->fn(work);
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			if (need_resched())
				schedule();
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		} else
			schedule();

	}
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	unuse_mm(dev->mm);
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	set_fs(oldfs);
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	return 0;
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}

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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;
	kfree(vq->ubuf_info);
	vq->ubuf_info = NULL;
}

void vhost_enable_zcopy(int vq)
{
	vhost_zcopy_mask |= 0x1 << vq;
}

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/* Helper to allocate iovec buffers for all vqs. */
static long vhost_dev_alloc_iovecs(struct vhost_dev *dev)
{
	int i;
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	bool zcopy;
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	for (i = 0; i < dev->nvqs; ++i) {
		dev->vqs[i].indirect = kmalloc(sizeof *dev->vqs[i].indirect *
					       UIO_MAXIOV, GFP_KERNEL);
		dev->vqs[i].log = kmalloc(sizeof *dev->vqs[i].log * UIO_MAXIOV,
					  GFP_KERNEL);
		dev->vqs[i].heads = kmalloc(sizeof *dev->vqs[i].heads *
					    UIO_MAXIOV, GFP_KERNEL);
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		zcopy = vhost_zcopy_mask & (0x1 << i);
		if (zcopy)
			dev->vqs[i].ubuf_info =
				kmalloc(sizeof *dev->vqs[i].ubuf_info *
					UIO_MAXIOV, GFP_KERNEL);
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		if (!dev->vqs[i].indirect || !dev->vqs[i].log ||
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			!dev->vqs[i].heads ||
			(zcopy && !dev->vqs[i].ubuf_info))
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			goto err_nomem;
	}
	return 0;
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err_nomem:
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	for (; i >= 0; --i)
		vhost_vq_free_iovecs(&dev->vqs[i]);
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	return -ENOMEM;
}

static void vhost_dev_free_iovecs(struct vhost_dev *dev)
{
	int i;
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	for (i = 0; i < dev->nvqs; ++i)
		vhost_vq_free_iovecs(&dev->vqs[i]);
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}

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long vhost_dev_init(struct vhost_dev *dev,
		    struct vhost_virtqueue *vqs, int nvqs)
{
	int i;
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	dev->vqs = vqs;
	dev->nvqs = nvqs;
	mutex_init(&dev->mutex);
	dev->log_ctx = NULL;
	dev->log_file = NULL;
	dev->memory = NULL;
	dev->mm = NULL;
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	spin_lock_init(&dev->work_lock);
	INIT_LIST_HEAD(&dev->work_list);
	dev->worker = NULL;
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	for (i = 0; i < dev->nvqs; ++i) {
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		dev->vqs[i].log = NULL;
		dev->vqs[i].indirect = NULL;
		dev->vqs[i].heads = NULL;
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		dev->vqs[i].ubuf_info = NULL;
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		dev->vqs[i].dev = dev;
		mutex_init(&dev->vqs[i].mutex);
		vhost_vq_reset(dev, dev->vqs + i);
		if (dev->vqs[i].handle_kick)
			vhost_poll_init(&dev->vqs[i].poll,
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					dev->vqs[i].handle_kick, POLLIN, dev);
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	}
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	return 0;
}

/* 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;
}

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struct vhost_attach_cgroups_struct {
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	struct vhost_work work;
	struct task_struct *owner;
	int ret;
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};

static void vhost_attach_cgroups_work(struct vhost_work *work)
{
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	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);
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}

static int vhost_attach_cgroups(struct vhost_dev *dev)
{
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	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;
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}

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/* Caller should have device mutex */
static long vhost_dev_set_owner(struct vhost_dev *dev)
{
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	struct task_struct *worker;
	int err;
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	/* Is there an owner already? */
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	if (dev->mm) {
		err = -EBUSY;
		goto err_mm;
	}
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	/* No owner, become one */
	dev->mm = get_task_mm(current);
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	worker = kthread_create(vhost_worker, dev, "vhost-%d", current->pid);
	if (IS_ERR(worker)) {
		err = PTR_ERR(worker);
		goto err_worker;
	}

	dev->worker = worker;
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	wake_up_process(worker);	/* avoid contributing to loadavg */

	err = vhost_attach_cgroups(dev);
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	if (err)
		goto err_cgroup;
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	err = vhost_dev_alloc_iovecs(dev);
	if (err)
		goto err_cgroup;

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	return 0;
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err_cgroup:
	kthread_stop(worker);
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	dev->worker = NULL;
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err_worker:
	if (dev->mm)
		mmput(dev->mm);
	dev->mm = NULL;
err_mm:
	return err;
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}

/* Caller should have device mutex */
long vhost_dev_reset_owner(struct vhost_dev *dev)
{
	struct vhost_memory *memory;

	/* Restore memory to default empty mapping. */
	memory = kmalloc(offsetof(struct vhost_memory, regions), GFP_KERNEL);
	if (!memory)
		return -ENOMEM;

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	vhost_dev_cleanup(dev, true);
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	memory->nregions = 0;
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	RCU_INIT_POINTER(dev->memory, memory);
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	return 0;
}

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void vhost_dev_stop(struct vhost_dev *dev)
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{
	int i;
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	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);
		}
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	}
}

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/* Caller should have device mutex if and only if locked is set */
void vhost_dev_cleanup(struct vhost_dev *dev, bool locked)
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{
	int i;
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	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].error)
			fput(dev->vqs[i].error);
		if (dev->vqs[i].kick)
			fput(dev->vqs[i].kick);
		if (dev->vqs[i].call_ctx)
			eventfd_ctx_put(dev->vqs[i].call_ctx);
		if (dev->vqs[i].call)
			fput(dev->vqs[i].call);
		vhost_vq_reset(dev, dev->vqs + i);
	}
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	vhost_dev_free_iovecs(dev);
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	if (dev->log_ctx)
		eventfd_ctx_put(dev->log_ctx);
	dev->log_ctx = NULL;
	if (dev->log_file)
		fput(dev->log_file);
	dev->log_file = NULL;
	/* No one will access memory at this point */
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	kfree(rcu_dereference_protected(dev->memory,
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					locked ==
						lockdep_is_held(&dev->mutex)));
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	RCU_INIT_POINTER(dev->memory, NULL);
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	WARN_ON(!list_empty(&dev->work_list));
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	if (dev->worker) {
		kthread_stop(dev->worker);
		dev->worker = NULL;
	}
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	if (dev->mm)
		mmput(dev->mm);
	dev->mm = NULL;
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}

static int log_access_ok(void __user *log_base, u64 addr, unsigned long sz)
{
	u64 a = addr / VHOST_PAGE_SIZE / 8;
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	/* Make sure 64 bit math will not overflow. */
	if (a > ULONG_MAX - (unsigned long)log_base ||
	    a + (unsigned long)log_base > ULONG_MAX)
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		return 0;
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	return access_ok(VERIFY_WRITE, log_base + a,
			 (sz + VHOST_PAGE_SIZE * 8 - 1) / VHOST_PAGE_SIZE / 8);
}

/* Caller should have vq mutex and device mutex. */
static int vq_memory_access_ok(void __user *log_base, struct vhost_memory *mem,
			       int log_all)
{
	int i;
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	if (!mem)
		return 0;
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	for (i = 0; i < mem->nregions; ++i) {
		struct vhost_memory_region *m = mem->regions + i;
		unsigned long a = m->userspace_addr;
		if (m->memory_size > ULONG_MAX)
			return 0;
		else if (!access_ok(VERIFY_WRITE, (void __user *)a,
				    m->memory_size))
			return 0;
		else if (log_all && !log_access_ok(log_base,
						   m->guest_phys_addr,
						   m->memory_size))
			return 0;
	}
	return 1;
}

/* Can we switch to this memory table? */
/* Caller should have device mutex but not vq mutex */
static int memory_access_ok(struct vhost_dev *d, struct vhost_memory *mem,
			    int log_all)
{
	int i;
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	for (i = 0; i < d->nvqs; ++i) {
		int ok;
		mutex_lock(&d->vqs[i].mutex);
		/* 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, mem,
						 log_all);
		else
			ok = 1;
		mutex_unlock(&d->vqs[i].mutex);
		if (!ok)
			return 0;
	}
	return 1;
}

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static int vq_access_ok(struct vhost_dev *d, unsigned int num,
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			struct vring_desc __user *desc,
			struct vring_avail __user *avail,
			struct vring_used __user *used)
{
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	size_t s = vhost_has_feature(d, VIRTIO_RING_F_EVENT_IDX) ? 2 : 0;
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	return access_ok(VERIFY_READ, desc, num * sizeof *desc) &&
	       access_ok(VERIFY_READ, avail,
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			 sizeof *avail + num * sizeof *avail->ring + s) &&
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	       access_ok(VERIFY_WRITE, used,
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			sizeof *used + num * sizeof *used->ring + s);
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}

/* Can we log writes? */
/* Caller should have device mutex but not vq mutex */
int vhost_log_access_ok(struct vhost_dev *dev)
{
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	struct vhost_memory *mp;

	mp = rcu_dereference_protected(dev->memory,
				       lockdep_is_held(&dev->mutex));
	return memory_access_ok(dev, mp, 1);
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}

/* Verify access for write logging. */
/* Caller should have vq mutex and device mutex */
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static int vq_log_access_ok(struct vhost_dev *d, struct vhost_virtqueue *vq,
			    void __user *log_base)
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{
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	struct vhost_memory *mp;
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	size_t s = vhost_has_feature(d, VIRTIO_RING_F_EVENT_IDX) ? 2 : 0;
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	mp = rcu_dereference_protected(vq->dev->memory,
				       lockdep_is_held(&vq->mutex));
	return vq_memory_access_ok(log_base, mp,
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			    vhost_has_feature(vq->dev, VHOST_F_LOG_ALL)) &&
		(!vq->log_used || log_access_ok(log_base, vq->log_addr,
					sizeof *vq->used +
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					vq->num * sizeof *vq->used->ring + s));
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}

/* Can we start vq? */
/* Caller should have vq mutex and device mutex */
int vhost_vq_access_ok(struct vhost_virtqueue *vq)
{
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	return vq_access_ok(vq->dev, vq->num, vq->desc, vq->avail, vq->used) &&
		vq_log_access_ok(vq->dev, vq, vq->log_base);
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}

static long vhost_set_memory(struct vhost_dev *d, struct vhost_memory __user *m)
{
	struct vhost_memory mem, *newmem, *oldmem;
	unsigned long size = offsetof(struct vhost_memory, regions);
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	if (copy_from_user(&mem, m, size))
		return -EFAULT;
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	if (mem.padding)
		return -EOPNOTSUPP;
	if (mem.nregions > VHOST_MEMORY_MAX_NREGIONS)
		return -E2BIG;
	newmem = kmalloc(size + mem.nregions * sizeof *m->regions, GFP_KERNEL);
	if (!newmem)
		return -ENOMEM;

	memcpy(newmem, &mem, size);
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	if (copy_from_user(newmem->regions, m->regions,
			   mem.nregions * sizeof *m->regions)) {
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		kfree(newmem);
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		return -EFAULT;
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	}

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	if (!memory_access_ok(d, newmem,
			      vhost_has_feature(d, VHOST_F_LOG_ALL))) {
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		kfree(newmem);
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		return -EFAULT;
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	}
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	oldmem = rcu_dereference_protected(d->memory,
					   lockdep_is_held(&d->mutex));
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	rcu_assign_pointer(d->memory, newmem);
	synchronize_rcu();
	kfree(oldmem);
	return 0;
}

static long vhost_set_vring(struct vhost_dev *d, int ioctl, void __user *argp)
{
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	struct file *eventfp, *filep = NULL;
	bool pollstart = false, pollstop = false;
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	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;
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	if (idx >= d->nvqs)
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		return -ENOBUFS;

	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;
		}
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		if (copy_from_user(&s, argp, sizeof s)) {
			r = -EFAULT;
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			break;
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		}
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		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;
		}
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		if (copy_from_user(&s, argp, sizeof s)) {
			r = -EFAULT;
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			break;
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		}
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		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;
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		if (copy_to_user(argp, &s, sizeof s))
			r = -EFAULT;
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		break;
	case VHOST_SET_VRING_ADDR:
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		if (copy_from_user(&a, argp, sizeof a)) {
			r = -EFAULT;
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			break;
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		}
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		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;
		}
		if ((a.avail_user_addr & (sizeof *vq->avail->ring - 1)) ||
		    (a.used_user_addr & (sizeof *vq->used->ring - 1)) ||
		    (a.log_guest_addr & (sizeof *vq->used->ring - 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) {
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			if (!vq_access_ok(d, vq->num,
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				(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:
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		if (copy_from_user(&f, argp, sizeof f)) {
			r = -EFAULT;
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			break;
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		}
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		eventfp = f.fd == -1 ? NULL : eventfd_fget(f.fd);
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		if (IS_ERR(eventfp)) {
			r = PTR_ERR(eventfp);
			break;
		}
738
		if (eventfp != vq->kick) {
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			pollstop = (filep = vq->kick) != NULL;
			pollstart = (vq->kick = eventfp) != NULL;
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		} else
			filep = eventfp;
		break;
	case VHOST_SET_VRING_CALL:
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		if (copy_from_user(&f, argp, sizeof f)) {
			r = -EFAULT;
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			break;
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		}
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		eventfp = f.fd == -1 ? NULL : eventfd_fget(f.fd);
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		if (IS_ERR(eventfp)) {
			r = PTR_ERR(eventfp);
			break;
		}
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		if (eventfp != vq->call) {
			filep = vq->call;
			ctx = vq->call_ctx;
			vq->call = eventfp;
			vq->call_ctx = eventfp ?
				eventfd_ctx_fileget(eventfp) : NULL;
		} else
			filep = eventfp;
		break;
	case VHOST_SET_VRING_ERR:
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		if (copy_from_user(&f, argp, sizeof f)) {
			r = -EFAULT;
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			break;
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		}
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		eventfp = f.fd == -1 ? NULL : eventfd_fget(f.fd);
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		if (IS_ERR(eventfp)) {
			r = PTR_ERR(eventfp);
			break;
		}
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		if (eventfp != vq->error) {
			filep = vq->error;
			vq->error = eventfp;
			ctx = vq->error_ctx;
			vq->error_ctx = eventfp ?
				eventfd_ctx_fileget(eventfp) : NULL;
		} else
			filep = eventfp;
		break;
	default:
		r = -ENOIOCTLCMD;
	}

	if (pollstop && vq->handle_kick)
		vhost_poll_stop(&vq->poll);

	if (ctx)
		eventfd_ctx_put(ctx);
	if (filep)
		fput(filep);

	if (pollstart && vq->handle_kick)
		vhost_poll_start(&vq->poll, vq->kick);

	mutex_unlock(&vq->mutex);

	if (pollstop && vq->handle_kick)
		vhost_poll_flush(&vq->poll);
	return r;
}

/* Caller must have device mutex */
long vhost_dev_ioctl(struct vhost_dev *d, unsigned int ioctl, unsigned long arg)
{
	void __user *argp = (void __user *)arg;
	struct file *eventfp, *filep = NULL;
	struct eventfd_ctx *ctx = NULL;
	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:
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		if (copy_from_user(&p, argp, sizeof p)) {
			r = -EFAULT;
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			break;
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		}
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		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. */
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			if (vq->private_data && !vq_log_access_ok(d, vq, base))
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				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;
		eventfp = fd == -1 ? NULL : eventfd_fget(fd);
		if (IS_ERR(eventfp)) {
			r = PTR_ERR(eventfp);
			break;
		}
		if (eventfp != d->log_file) {
			filep = d->log_file;
			ctx = d->log_ctx;
			d->log_ctx = eventfp ?
				eventfd_ctx_fileget(eventfp) : NULL;
		} else
			filep = eventfp;
		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);
		if (filep)
			fput(filep);
		break;
	default:
		r = vhost_set_vring(d, ioctl, argp);
		break;
	}
done:
	return r;
}

static const struct vhost_memory_region *find_region(struct vhost_memory *mem,
						     __u64 addr, __u32 len)
{
	struct vhost_memory_region *reg;
	int i;
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	/* linear search is not brilliant, but we really have on the order of 6
	 * regions in practice */
	for (i = 0; i < mem->nregions; ++i) {
		reg = mem->regions + i;
		if (reg->guest_phys_addr <= addr &&
		    reg->guest_phys_addr + reg->memory_size - 1 >= addr)
			return reg;
	}
	return NULL;
}

/* 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;
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	r = get_user_pages_fast(log, 1, 1, &page);
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	if (r < 0)
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		return r;
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	BUG_ON(r != 1);
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	base = kmap_atomic(page);
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	set_bit(bit, base);
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	kunmap_atomic(base);
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	set_page_dirty_lock(page);
	put_page(page);
	return 0;
}

static int log_write(void __user *log_base,
		     u64 write_address, u64 write_length)
{
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	u64 write_page = write_address / VHOST_PAGE_SIZE;
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	int r;
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	if (!write_length)
		return 0;
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	write_length += write_address % VHOST_PAGE_SIZE;
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	for (;;) {
		u64 base = (u64)(unsigned long)log_base;
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		u64 log = base + write_page / 8;
		int bit = write_page % 8;
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		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;
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		write_page += 1;
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	}
	return r;
}

int vhost_log_write(struct vhost_virtqueue *vq, struct vhost_log *log,
		    unsigned int log_num, u64 len)
{
	int i, r;

	/* Make sure data written is seen before log. */
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	smp_wmb();
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	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;
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		if (!len) {
			if (vq->log_ctx)
				eventfd_signal(vq->log_ctx, 1);
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			return 0;
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		}
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	}
	/* Length written exceeds what we have stored. This is a bug. */
	BUG();
	return 0;
}

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static int vhost_update_used_flags(struct vhost_virtqueue *vq)
{
	void __user *used;
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	if (__put_user(vq->used_flags, &vq->used->flags) < 0)
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		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_write(vq->log_base, vq->log_addr +
			  (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)
{
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	if (__put_user(vq->avail_idx, vhost_avail_event(vq)))
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		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_write(vq->log_base, vq->log_addr +
			  (used - (void __user *)vq->used),
			  sizeof *vhost_avail_event(vq));
		if (vq->log_ctx)
			eventfd_signal(vq->log_ctx, 1);
	}
	return 0;
}

int vhost_init_used(struct vhost_virtqueue *vq)
{
	int r;
	if (!vq->private_data)
		return 0;

	r = vhost_update_used_flags(vq);
	if (r)
		return r;
	vq->signalled_used_valid = false;
	return get_user(vq->last_used_idx, &vq->used->idx);
}

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static int translate_desc(struct vhost_dev *dev, u64 addr, u32 len,
			  struct iovec iov[], int iov_size)
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{
	const struct vhost_memory_region *reg;
	struct vhost_memory *mem;
	struct iovec *_iov;
	u64 s = 0;
	int ret = 0;

	rcu_read_lock();

	mem = rcu_dereference(dev->memory);
	while ((u64)len > s) {
		u64 size;
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		if (unlikely(ret >= iov_size)) {
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			ret = -ENOBUFS;
			break;
		}
		reg = find_region(mem, addr, len);
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		if (unlikely(!reg)) {
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			ret = -EFAULT;
			break;
		}
		_iov = iov + ret;
		size = reg->memory_size - addr + reg->guest_phys_addr;
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		_iov->iov_len = min((u64)len - s, size);
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		_iov->iov_base = (void __user *)(unsigned long)
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			(reg->userspace_addr + addr - reg->guest_phys_addr);
		s += size;
		addr += size;
		++ret;
	}

	rcu_read_unlock();
	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 vring_desc *desc)
{
	unsigned int next;

	/* If this descriptor says it doesn't chain, we're done. */
	if (!(desc->flags & VRING_DESC_F_NEXT))
		return -1U;

	/* Check they're not leading us off end of descriptors. */
	next = desc->next;
	/* Make sure compiler knows to grab that: we don't want it changing! */
	/* We will use the result as an index in an array, so most
	 * architectures only need a compiler barrier here. */
	read_barrier_depends();

	return next;
}

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static int get_indirect(struct vhost_dev *dev, 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)
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{
	struct vring_desc desc;
	unsigned int i = 0, count, found = 0;
	int ret;

	/* Sanity check */
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	if (unlikely(indirect->len % sizeof desc)) {
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		vq_err(vq, "Invalid length in indirect descriptor: "
		       "len 0x%llx not multiple of 0x%zx\n",
		       (unsigned long long)indirect->len,
		       sizeof desc);
		return -EINVAL;
	}

	ret = translate_desc(dev, indirect->addr, indirect->len, vq->indirect,
Jason Wang's avatar
Jason Wang committed
1105
			     UIO_MAXIOV);
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	if (unlikely(ret < 0)) {
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		vq_err(vq, "Translation failure %d in indirect.\n", ret);
		return ret;
	}

	/* We will use the result as an address to read from, so most
	 * architectures only need a compiler barrier here. */
	read_barrier_depends();

	count = indirect->len / sizeof desc;
	/* Buffers are chained via a 16 bit next field, so
	 * we can have at most 2^16 of these. */
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	if (unlikely(count > USHRT_MAX + 1)) {
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		vq_err(vq, "Indirect buffer length too big: %d\n",
		       indirect->len);
		return -E2BIG;
	}

	do {
		unsigned iov_count = *in_num + *out_num;
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		if (unlikely(++found > count)) {
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			vq_err(vq, "Loop detected: last one at %u "
			       "indirect size %u\n",
			       i, count);
			return -EINVAL;
		}
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		if (unlikely(memcpy_fromiovec((unsigned char *)&desc,
					      vq->indirect, sizeof desc))) {
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			vq_err(vq, "Failed indirect descriptor: idx %d, %zx\n",
			       i, (size_t)indirect->addr + i * sizeof desc);
			return -EINVAL;
		}
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		if (unlikely(desc.flags & VRING_DESC_F_INDIRECT)) {
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			vq_err(vq, "Nested indirect descriptor: idx %d, %zx\n",
			       i, (size_t)indirect->addr + i * sizeof desc);
			return -EINVAL;
		}

		ret = translate_desc(dev, desc.addr, desc.len, iov + iov_count,
				     iov_size - iov_count);
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		if (unlikely(ret < 0)) {
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			vq_err(vq, "Translation failure %d indirect idx %d\n",
			       ret, i);
			return ret;
		}
		/* If this is an input descriptor, increment that count. */
		if (desc.flags & VRING_DESC_F_WRITE) {
			*in_num += ret;
			if (unlikely(log)) {
				log[*log_num].addr = desc.addr;
				log[*log_num].len = desc.len;
				++*log_num;
			}
		} else {
			/* If it's an output descriptor, they're all supposed
			 * to come before any input descriptors. */
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			if (unlikely(*in_num)) {
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				vq_err(vq, "Indirect descriptor "
				       "has out after in: idx %d\n", i);
				return -EINVAL;
			}
			*out_num += ret;
		}
	} while ((i = next_desc(&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.
 *
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 * 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_dev *dev, 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)
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{
	struct vring_desc desc;
	unsigned int i, head, found = 0;
	u16 last_avail_idx;
	int ret;

	/* Check it isn't doing very strange things with descriptor numbers. */
	last_avail_idx = vq->last_avail_idx;
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	if (unlikely(__get_user(vq->avail_idx, &vq->avail->idx))) {
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		vq_err(vq, "Failed to access avail idx at %p\n",
		       &vq->avail->idx);
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		return -EFAULT;
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	}

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	if (unlikely((u16)(vq->avail_idx - last_avail_idx) > vq->num)) {
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		vq_err(vq, "Guest moved used index from %u to %u",
		       last_avail_idx, vq->avail_idx);
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		return -EFAULT;
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	}

	/* 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. */
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	smp_rmb();
1211 1212 1213

	/* Grab the next descriptor number they're advertising, and increment
	 * the index we've seen. */
1214 1215
	if (unlikely(__get_user(head,
				&vq->avail->ring[last_avail_idx % vq->num]))) {
1216 1217 1218
		vq_err(vq, "Failed to read head: idx %d address %p\n",
		       last_avail_idx,
		       &vq->avail->ring[last_avail_idx % vq->num]);
1219
		return -EFAULT;
1220 1221 1222
	}

	/* If their number is silly, that's an error. */
1223
	if (unlikely(head >= vq->num)) {
1224 1225
		vq_err(vq, "Guest says index %u > %u is available",
		       head, vq->num);
1226
		return -EINVAL;
1227 1228 1229 1230 1231 1232 1233 1234 1235 1236
	}

	/* 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;
1237
		if (unlikely(i >= vq->num)) {
1238 1239
			vq_err(vq, "Desc index is %u > %u, head = %u",
			       i, vq->num, head);
1240
			return -EINVAL;
1241
		}
1242
		if (unlikely(++found > vq->num)) {
1243 1244 1245
			vq_err(vq, "Loop detected: last one at %u "
			       "vq size %u head %u\n",
			       i, vq->num, head);
1246
			return -EINVAL;
1247
		}
1248
		ret = __copy_from_user(&desc, vq->desc + i, sizeof desc);
1249
		if (unlikely(ret)) {
1250 1251
			vq_err(vq, "Failed to get descriptor: idx %d addr %p\n",
			       i, vq->desc + i);
1252
			return -EFAULT;
1253 1254 1255 1256 1257
		}
		if (desc.flags & VRING_DESC_F_INDIRECT) {
			ret = get_indirect(dev, vq, iov, iov_size,
					   out_num, in_num,
					   log, log_num, &desc);
1258
			if (unlikely(ret < 0)) {
1259 1260
				vq_err(vq, "Failure detected "
				       "in indirect descriptor at idx %d\n", i);
1261
				return ret;
1262 1263 1264 1265 1266 1267
			}
			continue;
		}

		ret = translate_desc(dev, desc.addr, desc.len, iov + iov_count,
				     iov_size - iov_count);
1268
		if (unlikely(ret < 0)) {
1269 1270
			vq_err(vq, "Translation failure %d descriptor idx %d\n",
			       ret, i);
1271
			return ret;
1272 1273 1274 1275 1276 1277 1278 1279 1280 1281 1282 1283 1284
		}
		if (desc.flags & VRING_DESC_F_WRITE) {
			/* If this is an input descriptor,
			 * increment that count. */
			*in_num += ret;
			if (unlikely(log)) {
				log[*log_num].addr = desc.addr;
				log[*log_num].len = desc.len;
				++*log_num;
			}
		} else {
			/* If it's an output descriptor, they're all supposed
			 * to come before any input descriptors. */
1285
			if (unlikely(*in_num)) {
1286 1287
				vq_err(vq, "Descriptor has out after in: "
				       "idx %d\n", i);
1288
				return -EINVAL;
1289 1290 1291 1292 1293 1294 1295
			}
			*out_num += ret;
		}
	} while ((i = next_desc(&desc)) != -1);

	/* On success, increment avail index. */
	vq->last_avail_idx++;
1296 1297 1298 1299

	/* 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));
1300 1301 1302 1303
	return head;
}

/* Reverse the effect of vhost_get_vq_desc. Useful for error handling. */
1304
void vhost_discard_vq_desc(struct vhost_virtqueue *vq, int n)
1305
{
1306
	vq->last_avail_idx -= n;
1307 1308 1309 1310 1311 1312
}

/* 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)
{
1313
	struct vring_used_elem __user *used;
1314 1315 1316 1317

	/* The virtqueue contains a ring of used buffers.  Get a pointer to the
	 * next entry in that used ring. */
	used = &vq->used->ring[vq->last_used_idx % vq->num];
1318
	if (__put_user(head, &used->id)) {
1319 1320 1321
		vq_err(vq, "Failed to write used id");
		return -EFAULT;
	}
1322
	if (__put_user(len, &used->len)) {
1323 1324 1325 1326
		vq_err(vq, "Failed to write used len");
		return -EFAULT;
	}
	/* Make sure buffer is written before we update index. */
1327
	smp_wmb();
1328
	if (__put_user(vq->last_used_idx + 1, &vq->used->idx)) {
1329 1330 1331 1332 1333
		vq_err(vq, "Failed to increment used idx");
		return -EFAULT;
	}
	if (unlikely(vq->log_used)) {
		/* Make sure data is seen before log. */
1334
		smp_wmb();
1335 1336
		/* Log used ring entry write. */
		log_write(vq->log_base,
1337 1338
			  vq->log_addr +
			   ((void __user *)used - (void __user *)vq->used),
1339 1340 1341 1342 1343
			  sizeof *used);
		/* Log used index update. */
		log_write(vq->log_base,
			  vq->log_addr + offsetof(struct vring_used, idx),
			  sizeof vq->used->idx);
1344 1345 1346 1347
		if (vq->log_ctx)
			eventfd_signal(vq->log_ctx, 1);
	}
	vq->last_used_idx++;
1348 1349 1350 1351 1352 1353
	/* 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(vq->last_used_idx == vq->signalled_used))
		vq->signalled_used_valid = false;
1354 1355 1356
	return 0;
}

1357 1358 1359 1360 1361
static int __vhost_add_used_n(struct vhost_virtqueue *vq,
			    struct vring_used_elem *heads,
			    unsigned count)
{
	struct vring_used_elem __user *used;
1362
	u16 old, new;
1363 1364 1365 1366
	int start;

	start = vq->last_used_idx % vq->num;
	used = vq->used->ring + start;
1367
	if (__copy_to_user(used, heads, count * sizeof *used)) {
1368 1369 1370 1371 1372 1373 1374 1375 1376 1377 1378 1379
		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_write(vq->log_base,
			  vq->log_addr +
			   ((void __user *)used - (void __user *)vq->used),
			  count * sizeof *used);
	}
1380 1381 1382 1383 1384 1385 1386 1387
	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;
1388 1389 1390 1391 1392 1393 1394 1395 1396 1397 1398 1399 1400 1401 1402 1403 1404 1405 1406 1407 1408 1409 1410 1411 1412 1413 1414 1415 1416 1417 1418 1419 1420 1421 1422 1423 1424 1425
	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;
	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 (put_user(vq->last_used_idx, &vq->used->idx)) {
		vq_err(vq, "Failed to increment used idx");
		return -