Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next-2.6
[linux-2.6.git] / drivers / vhost / vhost.c
1 /* Copyright (C) 2009 Red Hat, Inc.
2  * Copyright (C) 2006 Rusty Russell IBM Corporation
3  *
4  * Author: Michael S. Tsirkin <mst@redhat.com>
5  *
6  * Inspiration, some code, and most witty comments come from
7  * Documentation/lguest/lguest.c, by Rusty Russell
8  *
9  * This work is licensed under the terms of the GNU GPL, version 2.
10  *
11  * Generic code for virtio server in host kernel.
12  */
13
14 #include <linux/eventfd.h>
15 #include <linux/vhost.h>
16 #include <linux/virtio_net.h>
17 #include <linux/mm.h>
18 #include <linux/miscdevice.h>
19 #include <linux/mutex.h>
20 #include <linux/rcupdate.h>
21 #include <linux/poll.h>
22 #include <linux/file.h>
23 #include <linux/highmem.h>
24 #include <linux/slab.h>
25 #include <linux/kthread.h>
26 #include <linux/cgroup.h>
27
28 #include <linux/net.h>
29 #include <linux/if_packet.h>
30 #include <linux/if_arp.h>
31
32 #include <net/sock.h>
33
34 #include "vhost.h"
35
36 enum {
37         VHOST_MEMORY_MAX_NREGIONS = 64,
38         VHOST_MEMORY_F_LOG = 0x1,
39 };
40
41 static void vhost_poll_func(struct file *file, wait_queue_head_t *wqh,
42                             poll_table *pt)
43 {
44         struct vhost_poll *poll;
45         poll = container_of(pt, struct vhost_poll, table);
46
47         poll->wqh = wqh;
48         add_wait_queue(wqh, &poll->wait);
49 }
50
51 static int vhost_poll_wakeup(wait_queue_t *wait, unsigned mode, int sync,
52                              void *key)
53 {
54         struct vhost_poll *poll = container_of(wait, struct vhost_poll, wait);
55
56         if (!((unsigned long)key & poll->mask))
57                 return 0;
58
59         vhost_poll_queue(poll);
60         return 0;
61 }
62
63 static void vhost_work_init(struct vhost_work *work, vhost_work_fn_t fn)
64 {
65         INIT_LIST_HEAD(&work->node);
66         work->fn = fn;
67         init_waitqueue_head(&work->done);
68         work->flushing = 0;
69         work->queue_seq = work->done_seq = 0;
70 }
71
72 /* Init poll structure */
73 void vhost_poll_init(struct vhost_poll *poll, vhost_work_fn_t fn,
74                      unsigned long mask, struct vhost_dev *dev)
75 {
76         init_waitqueue_func_entry(&poll->wait, vhost_poll_wakeup);
77         init_poll_funcptr(&poll->table, vhost_poll_func);
78         poll->mask = mask;
79         poll->dev = dev;
80
81         vhost_work_init(&poll->work, fn);
82 }
83
84 /* Start polling a file. We add ourselves to file's wait queue. The caller must
85  * keep a reference to a file until after vhost_poll_stop is called. */
86 void vhost_poll_start(struct vhost_poll *poll, struct file *file)
87 {
88         unsigned long mask;
89         mask = file->f_op->poll(file, &poll->table);
90         if (mask)
91                 vhost_poll_wakeup(&poll->wait, 0, 0, (void *)mask);
92 }
93
94 /* Stop polling a file. After this function returns, it becomes safe to drop the
95  * file reference. You must also flush afterwards. */
96 void vhost_poll_stop(struct vhost_poll *poll)
97 {
98         remove_wait_queue(poll->wqh, &poll->wait);
99 }
100
101 static void vhost_work_flush(struct vhost_dev *dev, struct vhost_work *work)
102 {
103         unsigned seq;
104         int left;
105         int flushing;
106
107         spin_lock_irq(&dev->work_lock);
108         seq = work->queue_seq;
109         work->flushing++;
110         spin_unlock_irq(&dev->work_lock);
111         wait_event(work->done, ({
112                    spin_lock_irq(&dev->work_lock);
113                    left = seq - work->done_seq <= 0;
114                    spin_unlock_irq(&dev->work_lock);
115                    left;
116         }));
117         spin_lock_irq(&dev->work_lock);
118         flushing = --work->flushing;
119         spin_unlock_irq(&dev->work_lock);
120         BUG_ON(flushing < 0);
121 }
122
123 /* Flush any work that has been scheduled. When calling this, don't hold any
124  * locks that are also used by the callback. */
125 void vhost_poll_flush(struct vhost_poll *poll)
126 {
127         vhost_work_flush(poll->dev, &poll->work);
128 }
129
130 static inline void vhost_work_queue(struct vhost_dev *dev,
131                                     struct vhost_work *work)
132 {
133         unsigned long flags;
134
135         spin_lock_irqsave(&dev->work_lock, flags);
136         if (list_empty(&work->node)) {
137                 list_add_tail(&work->node, &dev->work_list);
138                 work->queue_seq++;
139                 wake_up_process(dev->worker);
140         }
141         spin_unlock_irqrestore(&dev->work_lock, flags);
142 }
143
144 void vhost_poll_queue(struct vhost_poll *poll)
145 {
146         vhost_work_queue(poll->dev, &poll->work);
147 }
148
149 static void vhost_vq_reset(struct vhost_dev *dev,
150                            struct vhost_virtqueue *vq)
151 {
152         vq->num = 1;
153         vq->desc = NULL;
154         vq->avail = NULL;
155         vq->used = NULL;
156         vq->last_avail_idx = 0;
157         vq->avail_idx = 0;
158         vq->last_used_idx = 0;
159         vq->used_flags = 0;
160         vq->used_flags = 0;
161         vq->log_used = false;
162         vq->log_addr = -1ull;
163         vq->vhost_hlen = 0;
164         vq->sock_hlen = 0;
165         vq->private_data = NULL;
166         vq->log_base = NULL;
167         vq->error_ctx = NULL;
168         vq->error = NULL;
169         vq->kick = NULL;
170         vq->call_ctx = NULL;
171         vq->call = NULL;
172         vq->log_ctx = NULL;
173 }
174
175 static int vhost_worker(void *data)
176 {
177         struct vhost_dev *dev = data;
178         struct vhost_work *work = NULL;
179         unsigned uninitialized_var(seq);
180
181         for (;;) {
182                 /* mb paired w/ kthread_stop */
183                 set_current_state(TASK_INTERRUPTIBLE);
184
185                 spin_lock_irq(&dev->work_lock);
186                 if (work) {
187                         work->done_seq = seq;
188                         if (work->flushing)
189                                 wake_up_all(&work->done);
190                 }
191
192                 if (kthread_should_stop()) {
193                         spin_unlock_irq(&dev->work_lock);
194                         __set_current_state(TASK_RUNNING);
195                         return 0;
196                 }
197                 if (!list_empty(&dev->work_list)) {
198                         work = list_first_entry(&dev->work_list,
199                                                 struct vhost_work, node);
200                         list_del_init(&work->node);
201                         seq = work->queue_seq;
202                 } else
203                         work = NULL;
204                 spin_unlock_irq(&dev->work_lock);
205
206                 if (work) {
207                         __set_current_state(TASK_RUNNING);
208                         work->fn(work);
209                 } else
210                         schedule();
211
212         }
213 }
214
215 /* Helper to allocate iovec buffers for all vqs. */
216 static long vhost_dev_alloc_iovecs(struct vhost_dev *dev)
217 {
218         int i;
219         for (i = 0; i < dev->nvqs; ++i) {
220                 dev->vqs[i].indirect = kmalloc(sizeof *dev->vqs[i].indirect *
221                                                UIO_MAXIOV, GFP_KERNEL);
222                 dev->vqs[i].log = kmalloc(sizeof *dev->vqs[i].log * UIO_MAXIOV,
223                                           GFP_KERNEL);
224                 dev->vqs[i].heads = kmalloc(sizeof *dev->vqs[i].heads *
225                                             UIO_MAXIOV, GFP_KERNEL);
226
227                 if (!dev->vqs[i].indirect || !dev->vqs[i].log ||
228                         !dev->vqs[i].heads)
229                         goto err_nomem;
230         }
231         return 0;
232 err_nomem:
233         for (; i >= 0; --i) {
234                 kfree(dev->vqs[i].indirect);
235                 kfree(dev->vqs[i].log);
236                 kfree(dev->vqs[i].heads);
237         }
238         return -ENOMEM;
239 }
240
241 static void vhost_dev_free_iovecs(struct vhost_dev *dev)
242 {
243         int i;
244         for (i = 0; i < dev->nvqs; ++i) {
245                 kfree(dev->vqs[i].indirect);
246                 dev->vqs[i].indirect = NULL;
247                 kfree(dev->vqs[i].log);
248                 dev->vqs[i].log = NULL;
249                 kfree(dev->vqs[i].heads);
250                 dev->vqs[i].heads = NULL;
251         }
252 }
253
254 long vhost_dev_init(struct vhost_dev *dev,
255                     struct vhost_virtqueue *vqs, int nvqs)
256 {
257         int i;
258
259         dev->vqs = vqs;
260         dev->nvqs = nvqs;
261         mutex_init(&dev->mutex);
262         dev->log_ctx = NULL;
263         dev->log_file = NULL;
264         dev->memory = NULL;
265         dev->mm = NULL;
266         spin_lock_init(&dev->work_lock);
267         INIT_LIST_HEAD(&dev->work_list);
268         dev->worker = NULL;
269
270         for (i = 0; i < dev->nvqs; ++i) {
271                 dev->vqs[i].log = NULL;
272                 dev->vqs[i].indirect = NULL;
273                 dev->vqs[i].heads = NULL;
274                 dev->vqs[i].dev = dev;
275                 mutex_init(&dev->vqs[i].mutex);
276                 vhost_vq_reset(dev, dev->vqs + i);
277                 if (dev->vqs[i].handle_kick)
278                         vhost_poll_init(&dev->vqs[i].poll,
279                                         dev->vqs[i].handle_kick, POLLIN, dev);
280         }
281
282         return 0;
283 }
284
285 /* Caller should have device mutex */
286 long vhost_dev_check_owner(struct vhost_dev *dev)
287 {
288         /* Are you the owner? If not, I don't think you mean to do that */
289         return dev->mm == current->mm ? 0 : -EPERM;
290 }
291
292 struct vhost_attach_cgroups_struct {
293         struct vhost_work work;
294         struct task_struct *owner;
295         int ret;
296 };
297
298 static void vhost_attach_cgroups_work(struct vhost_work *work)
299 {
300         struct vhost_attach_cgroups_struct *s;
301         s = container_of(work, struct vhost_attach_cgroups_struct, work);
302         s->ret = cgroup_attach_task_all(s->owner, current);
303 }
304
305 static int vhost_attach_cgroups(struct vhost_dev *dev)
306 {
307         struct vhost_attach_cgroups_struct attach;
308         attach.owner = current;
309         vhost_work_init(&attach.work, vhost_attach_cgroups_work);
310         vhost_work_queue(dev, &attach.work);
311         vhost_work_flush(dev, &attach.work);
312         return attach.ret;
313 }
314
315 /* Caller should have device mutex */
316 static long vhost_dev_set_owner(struct vhost_dev *dev)
317 {
318         struct task_struct *worker;
319         int err;
320         /* Is there an owner already? */
321         if (dev->mm) {
322                 err = -EBUSY;
323                 goto err_mm;
324         }
325         /* No owner, become one */
326         dev->mm = get_task_mm(current);
327         worker = kthread_create(vhost_worker, dev, "vhost-%d", current->pid);
328         if (IS_ERR(worker)) {
329                 err = PTR_ERR(worker);
330                 goto err_worker;
331         }
332
333         dev->worker = worker;
334         wake_up_process(worker);        /* avoid contributing to loadavg */
335
336         err = vhost_attach_cgroups(dev);
337         if (err)
338                 goto err_cgroup;
339
340         err = vhost_dev_alloc_iovecs(dev);
341         if (err)
342                 goto err_cgroup;
343
344         return 0;
345 err_cgroup:
346         kthread_stop(worker);
347         dev->worker = NULL;
348 err_worker:
349         if (dev->mm)
350                 mmput(dev->mm);
351         dev->mm = NULL;
352 err_mm:
353         return err;
354 }
355
356 /* Caller should have device mutex */
357 long vhost_dev_reset_owner(struct vhost_dev *dev)
358 {
359         struct vhost_memory *memory;
360
361         /* Restore memory to default empty mapping. */
362         memory = kmalloc(offsetof(struct vhost_memory, regions), GFP_KERNEL);
363         if (!memory)
364                 return -ENOMEM;
365
366         vhost_dev_cleanup(dev);
367
368         memory->nregions = 0;
369         RCU_INIT_POINTER(dev->memory, memory);
370         return 0;
371 }
372
373 /* Caller should have device mutex */
374 void vhost_dev_cleanup(struct vhost_dev *dev)
375 {
376         int i;
377         for (i = 0; i < dev->nvqs; ++i) {
378                 if (dev->vqs[i].kick && dev->vqs[i].handle_kick) {
379                         vhost_poll_stop(&dev->vqs[i].poll);
380                         vhost_poll_flush(&dev->vqs[i].poll);
381                 }
382                 if (dev->vqs[i].error_ctx)
383                         eventfd_ctx_put(dev->vqs[i].error_ctx);
384                 if (dev->vqs[i].error)
385                         fput(dev->vqs[i].error);
386                 if (dev->vqs[i].kick)
387                         fput(dev->vqs[i].kick);
388                 if (dev->vqs[i].call_ctx)
389                         eventfd_ctx_put(dev->vqs[i].call_ctx);
390                 if (dev->vqs[i].call)
391                         fput(dev->vqs[i].call);
392                 vhost_vq_reset(dev, dev->vqs + i);
393         }
394         vhost_dev_free_iovecs(dev);
395         if (dev->log_ctx)
396                 eventfd_ctx_put(dev->log_ctx);
397         dev->log_ctx = NULL;
398         if (dev->log_file)
399                 fput(dev->log_file);
400         dev->log_file = NULL;
401         /* No one will access memory at this point */
402         kfree(rcu_dereference_protected(dev->memory,
403                                         lockdep_is_held(&dev->mutex)));
404         RCU_INIT_POINTER(dev->memory, NULL);
405         if (dev->mm)
406                 mmput(dev->mm);
407         dev->mm = NULL;
408
409         WARN_ON(!list_empty(&dev->work_list));
410         if (dev->worker) {
411                 kthread_stop(dev->worker);
412                 dev->worker = NULL;
413         }
414 }
415
416 static int log_access_ok(void __user *log_base, u64 addr, unsigned long sz)
417 {
418         u64 a = addr / VHOST_PAGE_SIZE / 8;
419         /* Make sure 64 bit math will not overflow. */
420         if (a > ULONG_MAX - (unsigned long)log_base ||
421             a + (unsigned long)log_base > ULONG_MAX)
422                 return 0;
423
424         return access_ok(VERIFY_WRITE, log_base + a,
425                          (sz + VHOST_PAGE_SIZE * 8 - 1) / VHOST_PAGE_SIZE / 8);
426 }
427
428 /* Caller should have vq mutex and device mutex. */
429 static int vq_memory_access_ok(void __user *log_base, struct vhost_memory *mem,
430                                int log_all)
431 {
432         int i;
433
434         if (!mem)
435                 return 0;
436
437         for (i = 0; i < mem->nregions; ++i) {
438                 struct vhost_memory_region *m = mem->regions + i;
439                 unsigned long a = m->userspace_addr;
440                 if (m->memory_size > ULONG_MAX)
441                         return 0;
442                 else if (!access_ok(VERIFY_WRITE, (void __user *)a,
443                                     m->memory_size))
444                         return 0;
445                 else if (log_all && !log_access_ok(log_base,
446                                                    m->guest_phys_addr,
447                                                    m->memory_size))
448                         return 0;
449         }
450         return 1;
451 }
452
453 /* Can we switch to this memory table? */
454 /* Caller should have device mutex but not vq mutex */
455 static int memory_access_ok(struct vhost_dev *d, struct vhost_memory *mem,
456                             int log_all)
457 {
458         int i;
459         for (i = 0; i < d->nvqs; ++i) {
460                 int ok;
461                 mutex_lock(&d->vqs[i].mutex);
462                 /* If ring is inactive, will check when it's enabled. */
463                 if (d->vqs[i].private_data)
464                         ok = vq_memory_access_ok(d->vqs[i].log_base, mem,
465                                                  log_all);
466                 else
467                         ok = 1;
468                 mutex_unlock(&d->vqs[i].mutex);
469                 if (!ok)
470                         return 0;
471         }
472         return 1;
473 }
474
475 static int vq_access_ok(unsigned int num,
476                         struct vring_desc __user *desc,
477                         struct vring_avail __user *avail,
478                         struct vring_used __user *used)
479 {
480         return access_ok(VERIFY_READ, desc, num * sizeof *desc) &&
481                access_ok(VERIFY_READ, avail,
482                          sizeof *avail + num * sizeof *avail->ring) &&
483                access_ok(VERIFY_WRITE, used,
484                         sizeof *used + num * sizeof *used->ring);
485 }
486
487 /* Can we log writes? */
488 /* Caller should have device mutex but not vq mutex */
489 int vhost_log_access_ok(struct vhost_dev *dev)
490 {
491         struct vhost_memory *mp;
492
493         mp = rcu_dereference_protected(dev->memory,
494                                        lockdep_is_held(&dev->mutex));
495         return memory_access_ok(dev, mp, 1);
496 }
497
498 /* Verify access for write logging. */
499 /* Caller should have vq mutex and device mutex */
500 static int vq_log_access_ok(struct vhost_virtqueue *vq, void __user *log_base)
501 {
502         struct vhost_memory *mp;
503
504         mp = rcu_dereference_protected(vq->dev->memory,
505                                        lockdep_is_held(&vq->mutex));
506         return vq_memory_access_ok(log_base, mp,
507                             vhost_has_feature(vq->dev, VHOST_F_LOG_ALL)) &&
508                 (!vq->log_used || log_access_ok(log_base, vq->log_addr,
509                                         sizeof *vq->used +
510                                         vq->num * sizeof *vq->used->ring));
511 }
512
513 /* Can we start vq? */
514 /* Caller should have vq mutex and device mutex */
515 int vhost_vq_access_ok(struct vhost_virtqueue *vq)
516 {
517         return vq_access_ok(vq->num, vq->desc, vq->avail, vq->used) &&
518                 vq_log_access_ok(vq, vq->log_base);
519 }
520
521 static long vhost_set_memory(struct vhost_dev *d, struct vhost_memory __user *m)
522 {
523         struct vhost_memory mem, *newmem, *oldmem;
524         unsigned long size = offsetof(struct vhost_memory, regions);
525         if (copy_from_user(&mem, m, size))
526                 return -EFAULT;
527         if (mem.padding)
528                 return -EOPNOTSUPP;
529         if (mem.nregions > VHOST_MEMORY_MAX_NREGIONS)
530                 return -E2BIG;
531         newmem = kmalloc(size + mem.nregions * sizeof *m->regions, GFP_KERNEL);
532         if (!newmem)
533                 return -ENOMEM;
534
535         memcpy(newmem, &mem, size);
536         if (copy_from_user(newmem->regions, m->regions,
537                            mem.nregions * sizeof *m->regions)) {
538                 kfree(newmem);
539                 return -EFAULT;
540         }
541
542         if (!memory_access_ok(d, newmem, vhost_has_feature(d, VHOST_F_LOG_ALL))) {
543                 kfree(newmem);
544                 return -EFAULT;
545         }
546         oldmem = rcu_dereference_protected(d->memory,
547                                            lockdep_is_held(&d->mutex));
548         rcu_assign_pointer(d->memory, newmem);
549         synchronize_rcu();
550         kfree(oldmem);
551         return 0;
552 }
553
554 static int init_used(struct vhost_virtqueue *vq,
555                      struct vring_used __user *used)
556 {
557         int r = put_user(vq->used_flags, &used->flags);
558         if (r)
559                 return r;
560         return get_user(vq->last_used_idx, &used->idx);
561 }
562
563 static long vhost_set_vring(struct vhost_dev *d, int ioctl, void __user *argp)
564 {
565         struct file *eventfp, *filep = NULL,
566                     *pollstart = NULL, *pollstop = NULL;
567         struct eventfd_ctx *ctx = NULL;
568         u32 __user *idxp = argp;
569         struct vhost_virtqueue *vq;
570         struct vhost_vring_state s;
571         struct vhost_vring_file f;
572         struct vhost_vring_addr a;
573         u32 idx;
574         long r;
575
576         r = get_user(idx, idxp);
577         if (r < 0)
578                 return r;
579         if (idx >= d->nvqs)
580                 return -ENOBUFS;
581
582         vq = d->vqs + idx;
583
584         mutex_lock(&vq->mutex);
585
586         switch (ioctl) {
587         case VHOST_SET_VRING_NUM:
588                 /* Resizing ring with an active backend?
589                  * You don't want to do that. */
590                 if (vq->private_data) {
591                         r = -EBUSY;
592                         break;
593                 }
594                 if (copy_from_user(&s, argp, sizeof s)) {
595                         r = -EFAULT;
596                         break;
597                 }
598                 if (!s.num || s.num > 0xffff || (s.num & (s.num - 1))) {
599                         r = -EINVAL;
600                         break;
601                 }
602                 vq->num = s.num;
603                 break;
604         case VHOST_SET_VRING_BASE:
605                 /* Moving base with an active backend?
606                  * You don't want to do that. */
607                 if (vq->private_data) {
608                         r = -EBUSY;
609                         break;
610                 }
611                 if (copy_from_user(&s, argp, sizeof s)) {
612                         r = -EFAULT;
613                         break;
614                 }
615                 if (s.num > 0xffff) {
616                         r = -EINVAL;
617                         break;
618                 }
619                 vq->last_avail_idx = s.num;
620                 /* Forget the cached index value. */
621                 vq->avail_idx = vq->last_avail_idx;
622                 break;
623         case VHOST_GET_VRING_BASE:
624                 s.index = idx;
625                 s.num = vq->last_avail_idx;
626                 if (copy_to_user(argp, &s, sizeof s))
627                         r = -EFAULT;
628                 break;
629         case VHOST_SET_VRING_ADDR:
630                 if (copy_from_user(&a, argp, sizeof a)) {
631                         r = -EFAULT;
632                         break;
633                 }
634                 if (a.flags & ~(0x1 << VHOST_VRING_F_LOG)) {
635                         r = -EOPNOTSUPP;
636                         break;
637                 }
638                 /* For 32bit, verify that the top 32bits of the user
639                    data are set to zero. */
640                 if ((u64)(unsigned long)a.desc_user_addr != a.desc_user_addr ||
641                     (u64)(unsigned long)a.used_user_addr != a.used_user_addr ||
642                     (u64)(unsigned long)a.avail_user_addr != a.avail_user_addr) {
643                         r = -EFAULT;
644                         break;
645                 }
646                 if ((a.avail_user_addr & (sizeof *vq->avail->ring - 1)) ||
647                     (a.used_user_addr & (sizeof *vq->used->ring - 1)) ||
648                     (a.log_guest_addr & (sizeof *vq->used->ring - 1))) {
649                         r = -EINVAL;
650                         break;
651                 }
652
653                 /* We only verify access here if backend is configured.
654                  * If it is not, we don't as size might not have been setup.
655                  * We will verify when backend is configured. */
656                 if (vq->private_data) {
657                         if (!vq_access_ok(vq->num,
658                                 (void __user *)(unsigned long)a.desc_user_addr,
659                                 (void __user *)(unsigned long)a.avail_user_addr,
660                                 (void __user *)(unsigned long)a.used_user_addr)) {
661                                 r = -EINVAL;
662                                 break;
663                         }
664
665                         /* Also validate log access for used ring if enabled. */
666                         if ((a.flags & (0x1 << VHOST_VRING_F_LOG)) &&
667                             !log_access_ok(vq->log_base, a.log_guest_addr,
668                                            sizeof *vq->used +
669                                            vq->num * sizeof *vq->used->ring)) {
670                                 r = -EINVAL;
671                                 break;
672                         }
673                 }
674
675                 r = init_used(vq, (struct vring_used __user *)(unsigned long)
676                               a.used_user_addr);
677                 if (r)
678                         break;
679                 vq->log_used = !!(a.flags & (0x1 << VHOST_VRING_F_LOG));
680                 vq->desc = (void __user *)(unsigned long)a.desc_user_addr;
681                 vq->avail = (void __user *)(unsigned long)a.avail_user_addr;
682                 vq->log_addr = a.log_guest_addr;
683                 vq->used = (void __user *)(unsigned long)a.used_user_addr;
684                 break;
685         case VHOST_SET_VRING_KICK:
686                 if (copy_from_user(&f, argp, sizeof f)) {
687                         r = -EFAULT;
688                         break;
689                 }
690                 eventfp = f.fd == -1 ? NULL : eventfd_fget(f.fd);
691                 if (IS_ERR(eventfp)) {
692                         r = PTR_ERR(eventfp);
693                         break;
694                 }
695                 if (eventfp != vq->kick) {
696                         pollstop = filep = vq->kick;
697                         pollstart = vq->kick = eventfp;
698                 } else
699                         filep = eventfp;
700                 break;
701         case VHOST_SET_VRING_CALL:
702                 if (copy_from_user(&f, argp, sizeof f)) {
703                         r = -EFAULT;
704                         break;
705                 }
706                 eventfp = f.fd == -1 ? NULL : eventfd_fget(f.fd);
707                 if (IS_ERR(eventfp)) {
708                         r = PTR_ERR(eventfp);
709                         break;
710                 }
711                 if (eventfp != vq->call) {
712                         filep = vq->call;
713                         ctx = vq->call_ctx;
714                         vq->call = eventfp;
715                         vq->call_ctx = eventfp ?
716                                 eventfd_ctx_fileget(eventfp) : NULL;
717                 } else
718                         filep = eventfp;
719                 break;
720         case VHOST_SET_VRING_ERR:
721                 if (copy_from_user(&f, argp, sizeof f)) {
722                         r = -EFAULT;
723                         break;
724                 }
725                 eventfp = f.fd == -1 ? NULL : eventfd_fget(f.fd);
726                 if (IS_ERR(eventfp)) {
727                         r = PTR_ERR(eventfp);
728                         break;
729                 }
730                 if (eventfp != vq->error) {
731                         filep = vq->error;
732                         vq->error = eventfp;
733                         ctx = vq->error_ctx;
734                         vq->error_ctx = eventfp ?
735                                 eventfd_ctx_fileget(eventfp) : NULL;
736                 } else
737                         filep = eventfp;
738                 break;
739         default:
740                 r = -ENOIOCTLCMD;
741         }
742
743         if (pollstop && vq->handle_kick)
744                 vhost_poll_stop(&vq->poll);
745
746         if (ctx)
747                 eventfd_ctx_put(ctx);
748         if (filep)
749                 fput(filep);
750
751         if (pollstart && vq->handle_kick)
752                 vhost_poll_start(&vq->poll, vq->kick);
753
754         mutex_unlock(&vq->mutex);
755
756         if (pollstop && vq->handle_kick)
757                 vhost_poll_flush(&vq->poll);
758         return r;
759 }
760
761 /* Caller must have device mutex */
762 long vhost_dev_ioctl(struct vhost_dev *d, unsigned int ioctl, unsigned long arg)
763 {
764         void __user *argp = (void __user *)arg;
765         struct file *eventfp, *filep = NULL;
766         struct eventfd_ctx *ctx = NULL;
767         u64 p;
768         long r;
769         int i, fd;
770
771         /* If you are not the owner, you can become one */
772         if (ioctl == VHOST_SET_OWNER) {
773                 r = vhost_dev_set_owner(d);
774                 goto done;
775         }
776
777         /* You must be the owner to do anything else */
778         r = vhost_dev_check_owner(d);
779         if (r)
780                 goto done;
781
782         switch (ioctl) {
783         case VHOST_SET_MEM_TABLE:
784                 r = vhost_set_memory(d, argp);
785                 break;
786         case VHOST_SET_LOG_BASE:
787                 if (copy_from_user(&p, argp, sizeof p)) {
788                         r = -EFAULT;
789                         break;
790                 }
791                 if ((u64)(unsigned long)p != p) {
792                         r = -EFAULT;
793                         break;
794                 }
795                 for (i = 0; i < d->nvqs; ++i) {
796                         struct vhost_virtqueue *vq;
797                         void __user *base = (void __user *)(unsigned long)p;
798                         vq = d->vqs + i;
799                         mutex_lock(&vq->mutex);
800                         /* If ring is inactive, will check when it's enabled. */
801                         if (vq->private_data && !vq_log_access_ok(vq, base))
802                                 r = -EFAULT;
803                         else
804                                 vq->log_base = base;
805                         mutex_unlock(&vq->mutex);
806                 }
807                 break;
808         case VHOST_SET_LOG_FD:
809                 r = get_user(fd, (int __user *)argp);
810                 if (r < 0)
811                         break;
812                 eventfp = fd == -1 ? NULL : eventfd_fget(fd);
813                 if (IS_ERR(eventfp)) {
814                         r = PTR_ERR(eventfp);
815                         break;
816                 }
817                 if (eventfp != d->log_file) {
818                         filep = d->log_file;
819                         ctx = d->log_ctx;
820                         d->log_ctx = eventfp ?
821                                 eventfd_ctx_fileget(eventfp) : NULL;
822                 } else
823                         filep = eventfp;
824                 for (i = 0; i < d->nvqs; ++i) {
825                         mutex_lock(&d->vqs[i].mutex);
826                         d->vqs[i].log_ctx = d->log_ctx;
827                         mutex_unlock(&d->vqs[i].mutex);
828                 }
829                 if (ctx)
830                         eventfd_ctx_put(ctx);
831                 if (filep)
832                         fput(filep);
833                 break;
834         default:
835                 r = vhost_set_vring(d, ioctl, argp);
836                 break;
837         }
838 done:
839         return r;
840 }
841
842 static const struct vhost_memory_region *find_region(struct vhost_memory *mem,
843                                                      __u64 addr, __u32 len)
844 {
845         struct vhost_memory_region *reg;
846         int i;
847         /* linear search is not brilliant, but we really have on the order of 6
848          * regions in practice */
849         for (i = 0; i < mem->nregions; ++i) {
850                 reg = mem->regions + i;
851                 if (reg->guest_phys_addr <= addr &&
852                     reg->guest_phys_addr + reg->memory_size - 1 >= addr)
853                         return reg;
854         }
855         return NULL;
856 }
857
858 /* TODO: This is really inefficient.  We need something like get_user()
859  * (instruction directly accesses the data, with an exception table entry
860  * returning -EFAULT). See Documentation/x86/exception-tables.txt.
861  */
862 static int set_bit_to_user(int nr, void __user *addr)
863 {
864         unsigned long log = (unsigned long)addr;
865         struct page *page;
866         void *base;
867         int bit = nr + (log % PAGE_SIZE) * 8;
868         int r;
869         r = get_user_pages_fast(log, 1, 1, &page);
870         if (r < 0)
871                 return r;
872         BUG_ON(r != 1);
873         base = kmap_atomic(page, KM_USER0);
874         set_bit(bit, base);
875         kunmap_atomic(base, KM_USER0);
876         set_page_dirty_lock(page);
877         put_page(page);
878         return 0;
879 }
880
881 static int log_write(void __user *log_base,
882                      u64 write_address, u64 write_length)
883 {
884         int r;
885         if (!write_length)
886                 return 0;
887         write_address /= VHOST_PAGE_SIZE;
888         for (;;) {
889                 u64 base = (u64)(unsigned long)log_base;
890                 u64 log = base + write_address / 8;
891                 int bit = write_address % 8;
892                 if ((u64)(unsigned long)log != log)
893                         return -EFAULT;
894                 r = set_bit_to_user(bit, (void __user *)(unsigned long)log);
895                 if (r < 0)
896                         return r;
897                 if (write_length <= VHOST_PAGE_SIZE)
898                         break;
899                 write_length -= VHOST_PAGE_SIZE;
900                 write_address += VHOST_PAGE_SIZE;
901         }
902         return r;
903 }
904
905 int vhost_log_write(struct vhost_virtqueue *vq, struct vhost_log *log,
906                     unsigned int log_num, u64 len)
907 {
908         int i, r;
909
910         /* Make sure data written is seen before log. */
911         smp_wmb();
912         for (i = 0; i < log_num; ++i) {
913                 u64 l = min(log[i].len, len);
914                 r = log_write(vq->log_base, log[i].addr, l);
915                 if (r < 0)
916                         return r;
917                 len -= l;
918                 if (!len) {
919                         if (vq->log_ctx)
920                                 eventfd_signal(vq->log_ctx, 1);
921                         return 0;
922                 }
923         }
924         /* Length written exceeds what we have stored. This is a bug. */
925         BUG();
926         return 0;
927 }
928
929 static int translate_desc(struct vhost_dev *dev, u64 addr, u32 len,
930                           struct iovec iov[], int iov_size)
931 {
932         const struct vhost_memory_region *reg;
933         struct vhost_memory *mem;
934         struct iovec *_iov;
935         u64 s = 0;
936         int ret = 0;
937
938         rcu_read_lock();
939
940         mem = rcu_dereference(dev->memory);
941         while ((u64)len > s) {
942                 u64 size;
943                 if (unlikely(ret >= iov_size)) {
944                         ret = -ENOBUFS;
945                         break;
946                 }
947                 reg = find_region(mem, addr, len);
948                 if (unlikely(!reg)) {
949                         ret = -EFAULT;
950                         break;
951                 }
952                 _iov = iov + ret;
953                 size = reg->memory_size - addr + reg->guest_phys_addr;
954                 _iov->iov_len = min((u64)len, size);
955                 _iov->iov_base = (void __user *)(unsigned long)
956                         (reg->userspace_addr + addr - reg->guest_phys_addr);
957                 s += size;
958                 addr += size;
959                 ++ret;
960         }
961
962         rcu_read_unlock();
963         return ret;
964 }
965
966 /* Each buffer in the virtqueues is actually a chain of descriptors.  This
967  * function returns the next descriptor in the chain,
968  * or -1U if we're at the end. */
969 static unsigned next_desc(struct vring_desc *desc)
970 {
971         unsigned int next;
972
973         /* If this descriptor says it doesn't chain, we're done. */
974         if (!(desc->flags & VRING_DESC_F_NEXT))
975                 return -1U;
976
977         /* Check they're not leading us off end of descriptors. */
978         next = desc->next;
979         /* Make sure compiler knows to grab that: we don't want it changing! */
980         /* We will use the result as an index in an array, so most
981          * architectures only need a compiler barrier here. */
982         read_barrier_depends();
983
984         return next;
985 }
986
987 static int get_indirect(struct vhost_dev *dev, struct vhost_virtqueue *vq,
988                         struct iovec iov[], unsigned int iov_size,
989                         unsigned int *out_num, unsigned int *in_num,
990                         struct vhost_log *log, unsigned int *log_num,
991                         struct vring_desc *indirect)
992 {
993         struct vring_desc desc;
994         unsigned int i = 0, count, found = 0;
995         int ret;
996
997         /* Sanity check */
998         if (unlikely(indirect->len % sizeof desc)) {
999                 vq_err(vq, "Invalid length in indirect descriptor: "
1000                        "len 0x%llx not multiple of 0x%zx\n",
1001                        (unsigned long long)indirect->len,
1002                        sizeof desc);
1003                 return -EINVAL;
1004         }
1005
1006         ret = translate_desc(dev, indirect->addr, indirect->len, vq->indirect,
1007                              UIO_MAXIOV);
1008         if (unlikely(ret < 0)) {
1009                 vq_err(vq, "Translation failure %d in indirect.\n", ret);
1010                 return ret;
1011         }
1012
1013         /* We will use the result as an address to read from, so most
1014          * architectures only need a compiler barrier here. */
1015         read_barrier_depends();
1016
1017         count = indirect->len / sizeof desc;
1018         /* Buffers are chained via a 16 bit next field, so
1019          * we can have at most 2^16 of these. */
1020         if (unlikely(count > USHRT_MAX + 1)) {
1021                 vq_err(vq, "Indirect buffer length too big: %d\n",
1022                        indirect->len);
1023                 return -E2BIG;
1024         }
1025
1026         do {
1027                 unsigned iov_count = *in_num + *out_num;
1028                 if (unlikely(++found > count)) {
1029                         vq_err(vq, "Loop detected: last one at %u "
1030                                "indirect size %u\n",
1031                                i, count);
1032                         return -EINVAL;
1033                 }
1034                 if (unlikely(memcpy_fromiovec((unsigned char *)&desc, vq->indirect,
1035                                               sizeof desc))) {
1036                         vq_err(vq, "Failed indirect descriptor: idx %d, %zx\n",
1037                                i, (size_t)indirect->addr + i * sizeof desc);
1038                         return -EINVAL;
1039                 }
1040                 if (unlikely(desc.flags & VRING_DESC_F_INDIRECT)) {
1041                         vq_err(vq, "Nested indirect descriptor: idx %d, %zx\n",
1042                                i, (size_t)indirect->addr + i * sizeof desc);
1043                         return -EINVAL;
1044                 }
1045
1046                 ret = translate_desc(dev, desc.addr, desc.len, iov + iov_count,
1047                                      iov_size - iov_count);
1048                 if (unlikely(ret < 0)) {
1049                         vq_err(vq, "Translation failure %d indirect idx %d\n",
1050                                ret, i);
1051                         return ret;
1052                 }
1053                 /* If this is an input descriptor, increment that count. */
1054                 if (desc.flags & VRING_DESC_F_WRITE) {
1055                         *in_num += ret;
1056                         if (unlikely(log)) {
1057                                 log[*log_num].addr = desc.addr;
1058                                 log[*log_num].len = desc.len;
1059                                 ++*log_num;
1060                         }
1061                 } else {
1062                         /* If it's an output descriptor, they're all supposed
1063                          * to come before any input descriptors. */
1064                         if (unlikely(*in_num)) {
1065                                 vq_err(vq, "Indirect descriptor "
1066                                        "has out after in: idx %d\n", i);
1067                                 return -EINVAL;
1068                         }
1069                         *out_num += ret;
1070                 }
1071         } while ((i = next_desc(&desc)) != -1);
1072         return 0;
1073 }
1074
1075 /* This looks in the virtqueue and for the first available buffer, and converts
1076  * it to an iovec for convenient access.  Since descriptors consist of some
1077  * number of output then some number of input descriptors, it's actually two
1078  * iovecs, but we pack them into one and note how many of each there were.
1079  *
1080  * This function returns the descriptor number found, or vq->num (which is
1081  * never a valid descriptor number) if none was found.  A negative code is
1082  * returned on error. */
1083 int vhost_get_vq_desc(struct vhost_dev *dev, struct vhost_virtqueue *vq,
1084                       struct iovec iov[], unsigned int iov_size,
1085                       unsigned int *out_num, unsigned int *in_num,
1086                       struct vhost_log *log, unsigned int *log_num)
1087 {
1088         struct vring_desc desc;
1089         unsigned int i, head, found = 0;
1090         u16 last_avail_idx;
1091         int ret;
1092
1093         /* Check it isn't doing very strange things with descriptor numbers. */
1094         last_avail_idx = vq->last_avail_idx;
1095         if (unlikely(get_user(vq->avail_idx, &vq->avail->idx))) {
1096                 vq_err(vq, "Failed to access avail idx at %p\n",
1097                        &vq->avail->idx);
1098                 return -EFAULT;
1099         }
1100
1101         if (unlikely((u16)(vq->avail_idx - last_avail_idx) > vq->num)) {
1102                 vq_err(vq, "Guest moved used index from %u to %u",
1103                        last_avail_idx, vq->avail_idx);
1104                 return -EFAULT;
1105         }
1106
1107         /* If there's nothing new since last we looked, return invalid. */
1108         if (vq->avail_idx == last_avail_idx)
1109                 return vq->num;
1110
1111         /* Only get avail ring entries after they have been exposed by guest. */
1112         smp_rmb();
1113
1114         /* Grab the next descriptor number they're advertising, and increment
1115          * the index we've seen. */
1116         if (unlikely(get_user(head,
1117                               &vq->avail->ring[last_avail_idx % vq->num]))) {
1118                 vq_err(vq, "Failed to read head: idx %d address %p\n",
1119                        last_avail_idx,
1120                        &vq->avail->ring[last_avail_idx % vq->num]);
1121                 return -EFAULT;
1122         }
1123
1124         /* If their number is silly, that's an error. */
1125         if (unlikely(head >= vq->num)) {
1126                 vq_err(vq, "Guest says index %u > %u is available",
1127                        head, vq->num);
1128                 return -EINVAL;
1129         }
1130
1131         /* When we start there are none of either input nor output. */
1132         *out_num = *in_num = 0;
1133         if (unlikely(log))
1134                 *log_num = 0;
1135
1136         i = head;
1137         do {
1138                 unsigned iov_count = *in_num + *out_num;
1139                 if (unlikely(i >= vq->num)) {
1140                         vq_err(vq, "Desc index is %u > %u, head = %u",
1141                                i, vq->num, head);
1142                         return -EINVAL;
1143                 }
1144                 if (unlikely(++found > vq->num)) {
1145                         vq_err(vq, "Loop detected: last one at %u "
1146                                "vq size %u head %u\n",
1147                                i, vq->num, head);
1148                         return -EINVAL;
1149                 }
1150                 ret = copy_from_user(&desc, vq->desc + i, sizeof desc);
1151                 if (unlikely(ret)) {
1152                         vq_err(vq, "Failed to get descriptor: idx %d addr %p\n",
1153                                i, vq->desc + i);
1154                         return -EFAULT;
1155                 }
1156                 if (desc.flags & VRING_DESC_F_INDIRECT) {
1157                         ret = get_indirect(dev, vq, iov, iov_size,
1158                                            out_num, in_num,
1159                                            log, log_num, &desc);
1160                         if (unlikely(ret < 0)) {
1161                                 vq_err(vq, "Failure detected "
1162                                        "in indirect descriptor at idx %d\n", i);
1163                                 return ret;
1164                         }
1165                         continue;
1166                 }
1167
1168                 ret = translate_desc(dev, desc.addr, desc.len, iov + iov_count,
1169                                      iov_size - iov_count);
1170                 if (unlikely(ret < 0)) {
1171                         vq_err(vq, "Translation failure %d descriptor idx %d\n",
1172                                ret, i);
1173                         return ret;
1174                 }
1175                 if (desc.flags & VRING_DESC_F_WRITE) {
1176                         /* If this is an input descriptor,
1177                          * increment that count. */
1178                         *in_num += ret;
1179                         if (unlikely(log)) {
1180                                 log[*log_num].addr = desc.addr;
1181                                 log[*log_num].len = desc.len;
1182                                 ++*log_num;
1183                         }
1184                 } else {
1185                         /* If it's an output descriptor, they're all supposed
1186                          * to come before any input descriptors. */
1187                         if (unlikely(*in_num)) {
1188                                 vq_err(vq, "Descriptor has out after in: "
1189                                        "idx %d\n", i);
1190                                 return -EINVAL;
1191                         }
1192                         *out_num += ret;
1193                 }
1194         } while ((i = next_desc(&desc)) != -1);
1195
1196         /* On success, increment avail index. */
1197         vq->last_avail_idx++;
1198         return head;
1199 }
1200
1201 /* Reverse the effect of vhost_get_vq_desc. Useful for error handling. */
1202 void vhost_discard_vq_desc(struct vhost_virtqueue *vq, int n)
1203 {
1204         vq->last_avail_idx -= n;
1205 }
1206
1207 /* After we've used one of their buffers, we tell them about it.  We'll then
1208  * want to notify the guest, using eventfd. */
1209 int vhost_add_used(struct vhost_virtqueue *vq, unsigned int head, int len)
1210 {
1211         struct vring_used_elem __user *used;
1212
1213         /* The virtqueue contains a ring of used buffers.  Get a pointer to the
1214          * next entry in that used ring. */
1215         used = &vq->used->ring[vq->last_used_idx % vq->num];
1216         if (put_user(head, &used->id)) {
1217                 vq_err(vq, "Failed to write used id");
1218                 return -EFAULT;
1219         }
1220         if (put_user(len, &used->len)) {
1221                 vq_err(vq, "Failed to write used len");
1222                 return -EFAULT;
1223         }
1224         /* Make sure buffer is written before we update index. */
1225         smp_wmb();
1226         if (put_user(vq->last_used_idx + 1, &vq->used->idx)) {
1227                 vq_err(vq, "Failed to increment used idx");
1228                 return -EFAULT;
1229         }
1230         if (unlikely(vq->log_used)) {
1231                 /* Make sure data is seen before log. */
1232                 smp_wmb();
1233                 /* Log used ring entry write. */
1234                 log_write(vq->log_base,
1235                           vq->log_addr +
1236                            ((void __user *)used - (void __user *)vq->used),
1237                           sizeof *used);
1238                 /* Log used index update. */
1239                 log_write(vq->log_base,
1240                           vq->log_addr + offsetof(struct vring_used, idx),
1241                           sizeof vq->used->idx);
1242                 if (vq->log_ctx)
1243                         eventfd_signal(vq->log_ctx, 1);
1244         }
1245         vq->last_used_idx++;
1246         return 0;
1247 }
1248
1249 static int __vhost_add_used_n(struct vhost_virtqueue *vq,
1250                             struct vring_used_elem *heads,
1251                             unsigned count)
1252 {
1253         struct vring_used_elem __user *used;
1254         int start;
1255
1256         start = vq->last_used_idx % vq->num;
1257         used = vq->used->ring + start;
1258         if (copy_to_user(used, heads, count * sizeof *used)) {
1259                 vq_err(vq, "Failed to write used");
1260                 return -EFAULT;
1261         }
1262         if (unlikely(vq->log_used)) {
1263                 /* Make sure data is seen before log. */
1264                 smp_wmb();
1265                 /* Log used ring entry write. */
1266                 log_write(vq->log_base,
1267                           vq->log_addr +
1268                            ((void __user *)used - (void __user *)vq->used),
1269                           count * sizeof *used);
1270         }
1271         vq->last_used_idx += count;
1272         return 0;
1273 }
1274
1275 /* After we've used one of their buffers, we tell them about it.  We'll then
1276  * want to notify the guest, using eventfd. */
1277 int vhost_add_used_n(struct vhost_virtqueue *vq, struct vring_used_elem *heads,
1278                      unsigned count)
1279 {
1280         int start, n, r;
1281
1282         start = vq->last_used_idx % vq->num;
1283         n = vq->num - start;
1284         if (n < count) {
1285                 r = __vhost_add_used_n(vq, heads, n);
1286                 if (r < 0)
1287                         return r;
1288                 heads += n;
1289                 count -= n;
1290         }
1291         r = __vhost_add_used_n(vq, heads, count);
1292
1293         /* Make sure buffer is written before we update index. */
1294         smp_wmb();
1295         if (put_user(vq->last_used_idx, &vq->used->idx)) {
1296                 vq_err(vq, "Failed to increment used idx");
1297                 return -EFAULT;
1298         }
1299         if (unlikely(vq->log_used)) {
1300                 /* Log used index update. */
1301                 log_write(vq->log_base,
1302                           vq->log_addr + offsetof(struct vring_used, idx),
1303                           sizeof vq->used->idx);
1304                 if (vq->log_ctx)
1305                         eventfd_signal(vq->log_ctx, 1);
1306         }
1307         return r;
1308 }
1309
1310 /* This actually signals the guest, using eventfd. */
1311 void vhost_signal(struct vhost_dev *dev, struct vhost_virtqueue *vq)
1312 {
1313         __u16 flags;
1314         /* Flush out used index updates. This is paired
1315          * with the barrier that the Guest executes when enabling
1316          * interrupts. */
1317         smp_mb();
1318
1319         if (get_user(flags, &vq->avail->flags)) {
1320                 vq_err(vq, "Failed to get flags");
1321                 return;
1322         }
1323
1324         /* If they don't want an interrupt, don't signal, unless empty. */
1325         if ((flags & VRING_AVAIL_F_NO_INTERRUPT) &&
1326             (vq->avail_idx != vq->last_avail_idx ||
1327              !vhost_has_feature(dev, VIRTIO_F_NOTIFY_ON_EMPTY)))
1328                 return;
1329
1330         /* Signal the Guest tell them we used something up. */
1331         if (vq->call_ctx)
1332                 eventfd_signal(vq->call_ctx, 1);
1333 }
1334
1335 /* And here's the combo meal deal.  Supersize me! */
1336 void vhost_add_used_and_signal(struct vhost_dev *dev,
1337                                struct vhost_virtqueue *vq,
1338                                unsigned int head, int len)
1339 {
1340         vhost_add_used(vq, head, len);
1341         vhost_signal(dev, vq);
1342 }
1343
1344 /* multi-buffer version of vhost_add_used_and_signal */
1345 void vhost_add_used_and_signal_n(struct vhost_dev *dev,
1346                                  struct vhost_virtqueue *vq,
1347                                  struct vring_used_elem *heads, unsigned count)
1348 {
1349         vhost_add_used_n(vq, heads, count);
1350         vhost_signal(dev, vq);
1351 }
1352
1353 /* OK, now we need to know about added descriptors. */
1354 bool vhost_enable_notify(struct vhost_virtqueue *vq)
1355 {
1356         u16 avail_idx;
1357         int r;
1358         if (!(vq->used_flags & VRING_USED_F_NO_NOTIFY))
1359                 return false;
1360         vq->used_flags &= ~VRING_USED_F_NO_NOTIFY;
1361         r = put_user(vq->used_flags, &vq->used->flags);
1362         if (r) {
1363                 vq_err(vq, "Failed to enable notification at %p: %d\n",
1364                        &vq->used->flags, r);
1365                 return false;
1366         }
1367         /* They could have slipped one in as we were doing that: make
1368          * sure it's written, then check again. */
1369         smp_mb();
1370         r = get_user(avail_idx, &vq->avail->idx);
1371         if (r) {
1372                 vq_err(vq, "Failed to check avail idx at %p: %d\n",
1373                        &vq->avail->idx, r);
1374                 return false;
1375         }
1376
1377         return avail_idx != vq->avail_idx;
1378 }
1379
1380 /* We don't need to be notified again. */
1381 void vhost_disable_notify(struct vhost_virtqueue *vq)
1382 {
1383         int r;
1384         if (vq->used_flags & VRING_USED_F_NO_NOTIFY)
1385                 return;
1386         vq->used_flags |= VRING_USED_F_NO_NOTIFY;
1387         r = put_user(vq->used_flags, &vq->used->flags);
1388         if (r)
1389                 vq_err(vq, "Failed to enable notification at %p: %d\n",
1390                        &vq->used->flags, r);
1391 }