7aa4eea930f1310077012eeab05a511bd1febdfe
[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/virtual/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/mmu_context.h>
19 #include <linux/miscdevice.h>
20 #include <linux/mutex.h>
21 #include <linux/rcupdate.h>
22 #include <linux/poll.h>
23 #include <linux/file.h>
24 #include <linux/highmem.h>
25 #include <linux/slab.h>
26 #include <linux/kthread.h>
27 #include <linux/cgroup.h>
28
29 #include <linux/net.h>
30 #include <linux/if_packet.h>
31 #include <linux/if_arp.h>
32
33 #include "vhost.h"
34
35 enum {
36         VHOST_MEMORY_MAX_NREGIONS = 64,
37         VHOST_MEMORY_F_LOG = 0x1,
38 };
39
40 static void vhost_poll_func(struct file *file, wait_queue_head_t *wqh,
41                             poll_table *pt)
42 {
43         struct vhost_poll *poll;
44
45         poll = container_of(pt, struct vhost_poll, table);
46         poll->wqh = wqh;
47         add_wait_queue(wqh, &poll->wait);
48 }
49
50 static int vhost_poll_wakeup(wait_queue_t *wait, unsigned mode, int sync,
51                              void *key)
52 {
53         struct vhost_poll *poll = container_of(wait, struct vhost_poll, wait);
54
55         if (!((unsigned long)key & poll->mask))
56                 return 0;
57
58         vhost_poll_queue(poll);
59         return 0;
60 }
61
62 static void vhost_work_init(struct vhost_work *work, vhost_work_fn_t fn)
63 {
64         INIT_LIST_HEAD(&work->node);
65         work->fn = fn;
66         init_waitqueue_head(&work->done);
67         work->flushing = 0;
68         work->queue_seq = work->done_seq = 0;
69 }
70
71 /* Init poll structure */
72 void vhost_poll_init(struct vhost_poll *poll, vhost_work_fn_t fn,
73                      unsigned long mask, struct vhost_dev *dev)
74 {
75         init_waitqueue_func_entry(&poll->wait, vhost_poll_wakeup);
76         init_poll_funcptr(&poll->table, vhost_poll_func);
77         poll->mask = mask;
78         poll->dev = dev;
79
80         vhost_work_init(&poll->work, fn);
81 }
82
83 /* Start polling a file. We add ourselves to file's wait queue. The caller must
84  * keep a reference to a file until after vhost_poll_stop is called. */
85 void vhost_poll_start(struct vhost_poll *poll, struct file *file)
86 {
87         unsigned long mask;
88
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 bool vhost_work_seq_done(struct vhost_dev *dev, struct vhost_work *work,
102                                 unsigned seq)
103 {
104         int left;
105
106         spin_lock_irq(&dev->work_lock);
107         left = seq - work->done_seq;
108         spin_unlock_irq(&dev->work_lock);
109         return left <= 0;
110 }
111
112 static void vhost_work_flush(struct vhost_dev *dev, struct vhost_work *work)
113 {
114         unsigned seq;
115         int flushing;
116
117         spin_lock_irq(&dev->work_lock);
118         seq = work->queue_seq;
119         work->flushing++;
120         spin_unlock_irq(&dev->work_lock);
121         wait_event(work->done, vhost_work_seq_done(dev, work, seq));
122         spin_lock_irq(&dev->work_lock);
123         flushing = --work->flushing;
124         spin_unlock_irq(&dev->work_lock);
125         BUG_ON(flushing < 0);
126 }
127
128 /* Flush any work that has been scheduled. When calling this, don't hold any
129  * locks that are also used by the callback. */
130 void vhost_poll_flush(struct vhost_poll *poll)
131 {
132         vhost_work_flush(poll->dev, &poll->work);
133 }
134
135 static inline void vhost_work_queue(struct vhost_dev *dev,
136                                     struct vhost_work *work)
137 {
138         unsigned long flags;
139
140         spin_lock_irqsave(&dev->work_lock, flags);
141         if (list_empty(&work->node)) {
142                 list_add_tail(&work->node, &dev->work_list);
143                 work->queue_seq++;
144                 wake_up_process(dev->worker);
145         }
146         spin_unlock_irqrestore(&dev->work_lock, flags);
147 }
148
149 void vhost_poll_queue(struct vhost_poll *poll)
150 {
151         vhost_work_queue(poll->dev, &poll->work);
152 }
153
154 static void vhost_vq_reset(struct vhost_dev *dev,
155                            struct vhost_virtqueue *vq)
156 {
157         vq->num = 1;
158         vq->desc = NULL;
159         vq->avail = NULL;
160         vq->used = NULL;
161         vq->last_avail_idx = 0;
162         vq->avail_idx = 0;
163         vq->last_used_idx = 0;
164         vq->used_flags = 0;
165         vq->log_used = false;
166         vq->log_addr = -1ull;
167         vq->vhost_hlen = 0;
168         vq->sock_hlen = 0;
169         vq->private_data = NULL;
170         vq->log_base = NULL;
171         vq->error_ctx = NULL;
172         vq->error = NULL;
173         vq->kick = NULL;
174         vq->call_ctx = NULL;
175         vq->call = NULL;
176         vq->log_ctx = NULL;
177 }
178
179 static int vhost_worker(void *data)
180 {
181         struct vhost_dev *dev = data;
182         struct vhost_work *work = NULL;
183         unsigned uninitialized_var(seq);
184
185         use_mm(dev->mm);
186
187         for (;;) {
188                 /* mb paired w/ kthread_stop */
189                 set_current_state(TASK_INTERRUPTIBLE);
190
191                 spin_lock_irq(&dev->work_lock);
192                 if (work) {
193                         work->done_seq = seq;
194                         if (work->flushing)
195                                 wake_up_all(&work->done);
196                 }
197
198                 if (kthread_should_stop()) {
199                         spin_unlock_irq(&dev->work_lock);
200                         __set_current_state(TASK_RUNNING);
201                         break;
202                 }
203                 if (!list_empty(&dev->work_list)) {
204                         work = list_first_entry(&dev->work_list,
205                                                 struct vhost_work, node);
206                         list_del_init(&work->node);
207                         seq = work->queue_seq;
208                 } else
209                         work = NULL;
210                 spin_unlock_irq(&dev->work_lock);
211
212                 if (work) {
213                         __set_current_state(TASK_RUNNING);
214                         work->fn(work);
215                 } else
216                         schedule();
217
218         }
219         unuse_mm(dev->mm);
220         return 0;
221 }
222
223 /* Helper to allocate iovec buffers for all vqs. */
224 static long vhost_dev_alloc_iovecs(struct vhost_dev *dev)
225 {
226         int i;
227
228         for (i = 0; i < dev->nvqs; ++i) {
229                 dev->vqs[i].indirect = kmalloc(sizeof *dev->vqs[i].indirect *
230                                                UIO_MAXIOV, GFP_KERNEL);
231                 dev->vqs[i].log = kmalloc(sizeof *dev->vqs[i].log * UIO_MAXIOV,
232                                           GFP_KERNEL);
233                 dev->vqs[i].heads = kmalloc(sizeof *dev->vqs[i].heads *
234                                             UIO_MAXIOV, GFP_KERNEL);
235
236                 if (!dev->vqs[i].indirect || !dev->vqs[i].log ||
237                         !dev->vqs[i].heads)
238                         goto err_nomem;
239         }
240         return 0;
241
242 err_nomem:
243         for (; i >= 0; --i) {
244                 kfree(dev->vqs[i].indirect);
245                 kfree(dev->vqs[i].log);
246                 kfree(dev->vqs[i].heads);
247         }
248         return -ENOMEM;
249 }
250
251 static void vhost_dev_free_iovecs(struct vhost_dev *dev)
252 {
253         int i;
254
255         for (i = 0; i < dev->nvqs; ++i) {
256                 kfree(dev->vqs[i].indirect);
257                 dev->vqs[i].indirect = NULL;
258                 kfree(dev->vqs[i].log);
259                 dev->vqs[i].log = NULL;
260                 kfree(dev->vqs[i].heads);
261                 dev->vqs[i].heads = NULL;
262         }
263 }
264
265 long vhost_dev_init(struct vhost_dev *dev,
266                     struct vhost_virtqueue *vqs, int nvqs)
267 {
268         int i;
269
270         dev->vqs = vqs;
271         dev->nvqs = nvqs;
272         mutex_init(&dev->mutex);
273         dev->log_ctx = NULL;
274         dev->log_file = NULL;
275         dev->memory = NULL;
276         dev->mm = NULL;
277         spin_lock_init(&dev->work_lock);
278         INIT_LIST_HEAD(&dev->work_list);
279         dev->worker = NULL;
280
281         for (i = 0; i < dev->nvqs; ++i) {
282                 dev->vqs[i].log = NULL;
283                 dev->vqs[i].indirect = NULL;
284                 dev->vqs[i].heads = NULL;
285                 dev->vqs[i].dev = dev;
286                 mutex_init(&dev->vqs[i].mutex);
287                 vhost_vq_reset(dev, dev->vqs + i);
288                 if (dev->vqs[i].handle_kick)
289                         vhost_poll_init(&dev->vqs[i].poll,
290                                         dev->vqs[i].handle_kick, POLLIN, dev);
291         }
292
293         return 0;
294 }
295
296 /* Caller should have device mutex */
297 long vhost_dev_check_owner(struct vhost_dev *dev)
298 {
299         /* Are you the owner? If not, I don't think you mean to do that */
300         return dev->mm == current->mm ? 0 : -EPERM;
301 }
302
303 struct vhost_attach_cgroups_struct {
304         struct vhost_work work;
305         struct task_struct *owner;
306         int ret;
307 };
308
309 static void vhost_attach_cgroups_work(struct vhost_work *work)
310 {
311         struct vhost_attach_cgroups_struct *s;
312
313         s = container_of(work, struct vhost_attach_cgroups_struct, work);
314         s->ret = cgroup_attach_task_all(s->owner, current);
315 }
316
317 static int vhost_attach_cgroups(struct vhost_dev *dev)
318 {
319         struct vhost_attach_cgroups_struct attach;
320
321         attach.owner = current;
322         vhost_work_init(&attach.work, vhost_attach_cgroups_work);
323         vhost_work_queue(dev, &attach.work);
324         vhost_work_flush(dev, &attach.work);
325         return attach.ret;
326 }
327
328 /* Caller should have device mutex */
329 static long vhost_dev_set_owner(struct vhost_dev *dev)
330 {
331         struct task_struct *worker;
332         int err;
333
334         /* Is there an owner already? */
335         if (dev->mm) {
336                 err = -EBUSY;
337                 goto err_mm;
338         }
339
340         /* No owner, become one */
341         dev->mm = get_task_mm(current);
342         worker = kthread_create(vhost_worker, dev, "vhost-%d", current->pid);
343         if (IS_ERR(worker)) {
344                 err = PTR_ERR(worker);
345                 goto err_worker;
346         }
347
348         dev->worker = worker;
349         wake_up_process(worker);        /* avoid contributing to loadavg */
350
351         err = vhost_attach_cgroups(dev);
352         if (err)
353                 goto err_cgroup;
354
355         err = vhost_dev_alloc_iovecs(dev);
356         if (err)
357                 goto err_cgroup;
358
359         return 0;
360 err_cgroup:
361         kthread_stop(worker);
362         dev->worker = NULL;
363 err_worker:
364         if (dev->mm)
365                 mmput(dev->mm);
366         dev->mm = NULL;
367 err_mm:
368         return err;
369 }
370
371 /* Caller should have device mutex */
372 long vhost_dev_reset_owner(struct vhost_dev *dev)
373 {
374         struct vhost_memory *memory;
375
376         /* Restore memory to default empty mapping. */
377         memory = kmalloc(offsetof(struct vhost_memory, regions), GFP_KERNEL);
378         if (!memory)
379                 return -ENOMEM;
380
381         vhost_dev_cleanup(dev);
382
383         memory->nregions = 0;
384         RCU_INIT_POINTER(dev->memory, memory);
385         return 0;
386 }
387
388 /* Caller should have device mutex */
389 void vhost_dev_cleanup(struct vhost_dev *dev)
390 {
391         int i;
392
393         for (i = 0; i < dev->nvqs; ++i) {
394                 if (dev->vqs[i].kick && dev->vqs[i].handle_kick) {
395                         vhost_poll_stop(&dev->vqs[i].poll);
396                         vhost_poll_flush(&dev->vqs[i].poll);
397                 }
398                 if (dev->vqs[i].error_ctx)
399                         eventfd_ctx_put(dev->vqs[i].error_ctx);
400                 if (dev->vqs[i].error)
401                         fput(dev->vqs[i].error);
402                 if (dev->vqs[i].kick)
403                         fput(dev->vqs[i].kick);
404                 if (dev->vqs[i].call_ctx)
405                         eventfd_ctx_put(dev->vqs[i].call_ctx);
406                 if (dev->vqs[i].call)
407                         fput(dev->vqs[i].call);
408                 vhost_vq_reset(dev, dev->vqs + i);
409         }
410         vhost_dev_free_iovecs(dev);
411         if (dev->log_ctx)
412                 eventfd_ctx_put(dev->log_ctx);
413         dev->log_ctx = NULL;
414         if (dev->log_file)
415                 fput(dev->log_file);
416         dev->log_file = NULL;
417         /* No one will access memory at this point */
418         kfree(rcu_dereference_protected(dev->memory,
419                                         lockdep_is_held(&dev->mutex)));
420         RCU_INIT_POINTER(dev->memory, NULL);
421         WARN_ON(!list_empty(&dev->work_list));
422         if (dev->worker) {
423                 kthread_stop(dev->worker);
424                 dev->worker = NULL;
425         }
426         if (dev->mm)
427                 mmput(dev->mm);
428         dev->mm = NULL;
429 }
430
431 static int log_access_ok(void __user *log_base, u64 addr, unsigned long sz)
432 {
433         u64 a = addr / VHOST_PAGE_SIZE / 8;
434
435         /* Make sure 64 bit math will not overflow. */
436         if (a > ULONG_MAX - (unsigned long)log_base ||
437             a + (unsigned long)log_base > ULONG_MAX)
438                 return 0;
439
440         return access_ok(VERIFY_WRITE, log_base + a,
441                          (sz + VHOST_PAGE_SIZE * 8 - 1) / VHOST_PAGE_SIZE / 8);
442 }
443
444 /* Caller should have vq mutex and device mutex. */
445 static int vq_memory_access_ok(void __user *log_base, struct vhost_memory *mem,
446                                int log_all)
447 {
448         int i;
449
450         if (!mem)
451                 return 0;
452
453         for (i = 0; i < mem->nregions; ++i) {
454                 struct vhost_memory_region *m = mem->regions + i;
455                 unsigned long a = m->userspace_addr;
456                 if (m->memory_size > ULONG_MAX)
457                         return 0;
458                 else if (!access_ok(VERIFY_WRITE, (void __user *)a,
459                                     m->memory_size))
460                         return 0;
461                 else if (log_all && !log_access_ok(log_base,
462                                                    m->guest_phys_addr,
463                                                    m->memory_size))
464                         return 0;
465         }
466         return 1;
467 }
468
469 /* Can we switch to this memory table? */
470 /* Caller should have device mutex but not vq mutex */
471 static int memory_access_ok(struct vhost_dev *d, struct vhost_memory *mem,
472                             int log_all)
473 {
474         int i;
475
476         for (i = 0; i < d->nvqs; ++i) {
477                 int ok;
478                 mutex_lock(&d->vqs[i].mutex);
479                 /* If ring is inactive, will check when it's enabled. */
480                 if (d->vqs[i].private_data)
481                         ok = vq_memory_access_ok(d->vqs[i].log_base, mem,
482                                                  log_all);
483                 else
484                         ok = 1;
485                 mutex_unlock(&d->vqs[i].mutex);
486                 if (!ok)
487                         return 0;
488         }
489         return 1;
490 }
491
492 static int vq_access_ok(unsigned int num,
493                         struct vring_desc __user *desc,
494                         struct vring_avail __user *avail,
495                         struct vring_used __user *used)
496 {
497         return access_ok(VERIFY_READ, desc, num * sizeof *desc) &&
498                access_ok(VERIFY_READ, avail,
499                          sizeof *avail + num * sizeof *avail->ring) &&
500                access_ok(VERIFY_WRITE, used,
501                         sizeof *used + num * sizeof *used->ring);
502 }
503
504 /* Can we log writes? */
505 /* Caller should have device mutex but not vq mutex */
506 int vhost_log_access_ok(struct vhost_dev *dev)
507 {
508         struct vhost_memory *mp;
509
510         mp = rcu_dereference_protected(dev->memory,
511                                        lockdep_is_held(&dev->mutex));
512         return memory_access_ok(dev, mp, 1);
513 }
514
515 /* Verify access for write logging. */
516 /* Caller should have vq mutex and device mutex */
517 static int vq_log_access_ok(struct vhost_virtqueue *vq, void __user *log_base)
518 {
519         struct vhost_memory *mp;
520
521         mp = rcu_dereference_protected(vq->dev->memory,
522                                        lockdep_is_held(&vq->mutex));
523         return vq_memory_access_ok(log_base, mp,
524                             vhost_has_feature(vq->dev, VHOST_F_LOG_ALL)) &&
525                 (!vq->log_used || log_access_ok(log_base, vq->log_addr,
526                                         sizeof *vq->used +
527                                         vq->num * sizeof *vq->used->ring));
528 }
529
530 /* Can we start vq? */
531 /* Caller should have vq mutex and device mutex */
532 int vhost_vq_access_ok(struct vhost_virtqueue *vq)
533 {
534         return vq_access_ok(vq->num, vq->desc, vq->avail, vq->used) &&
535                 vq_log_access_ok(vq, vq->log_base);
536 }
537
538 static long vhost_set_memory(struct vhost_dev *d, struct vhost_memory __user *m)
539 {
540         struct vhost_memory mem, *newmem, *oldmem;
541         unsigned long size = offsetof(struct vhost_memory, regions);
542
543         if (copy_from_user(&mem, m, size))
544                 return -EFAULT;
545         if (mem.padding)
546                 return -EOPNOTSUPP;
547         if (mem.nregions > VHOST_MEMORY_MAX_NREGIONS)
548                 return -E2BIG;
549         newmem = kmalloc(size + mem.nregions * sizeof *m->regions, GFP_KERNEL);
550         if (!newmem)
551                 return -ENOMEM;
552
553         memcpy(newmem, &mem, size);
554         if (copy_from_user(newmem->regions, m->regions,
555                            mem.nregions * sizeof *m->regions)) {
556                 kfree(newmem);
557                 return -EFAULT;
558         }
559
560         if (!memory_access_ok(d, newmem,
561                               vhost_has_feature(d, VHOST_F_LOG_ALL))) {
562                 kfree(newmem);
563                 return -EFAULT;
564         }
565         oldmem = rcu_dereference_protected(d->memory,
566                                            lockdep_is_held(&d->mutex));
567         rcu_assign_pointer(d->memory, newmem);
568         synchronize_rcu();
569         kfree(oldmem);
570         return 0;
571 }
572
573 static int init_used(struct vhost_virtqueue *vq,
574                      struct vring_used __user *used)
575 {
576         int r = put_user(vq->used_flags, &used->flags);
577
578         if (r)
579                 return r;
580         return get_user(vq->last_used_idx, &used->idx);
581 }
582
583 static long vhost_set_vring(struct vhost_dev *d, int ioctl, void __user *argp)
584 {
585         struct file *eventfp, *filep = NULL,
586                     *pollstart = NULL, *pollstop = NULL;
587         struct eventfd_ctx *ctx = NULL;
588         u32 __user *idxp = argp;
589         struct vhost_virtqueue *vq;
590         struct vhost_vring_state s;
591         struct vhost_vring_file f;
592         struct vhost_vring_addr a;
593         u32 idx;
594         long r;
595
596         r = get_user(idx, idxp);
597         if (r < 0)
598                 return r;
599         if (idx >= d->nvqs)
600                 return -ENOBUFS;
601
602         vq = d->vqs + idx;
603
604         mutex_lock(&vq->mutex);
605
606         switch (ioctl) {
607         case VHOST_SET_VRING_NUM:
608                 /* Resizing ring with an active backend?
609                  * You don't want to do that. */
610                 if (vq->private_data) {
611                         r = -EBUSY;
612                         break;
613                 }
614                 if (copy_from_user(&s, argp, sizeof s)) {
615                         r = -EFAULT;
616                         break;
617                 }
618                 if (!s.num || s.num > 0xffff || (s.num & (s.num - 1))) {
619                         r = -EINVAL;
620                         break;
621                 }
622                 vq->num = s.num;
623                 break;
624         case VHOST_SET_VRING_BASE:
625                 /* Moving base with an active backend?
626                  * You don't want to do that. */
627                 if (vq->private_data) {
628                         r = -EBUSY;
629                         break;
630                 }
631                 if (copy_from_user(&s, argp, sizeof s)) {
632                         r = -EFAULT;
633                         break;
634                 }
635                 if (s.num > 0xffff) {
636                         r = -EINVAL;
637                         break;
638                 }
639                 vq->last_avail_idx = s.num;
640                 /* Forget the cached index value. */
641                 vq->avail_idx = vq->last_avail_idx;
642                 break;
643         case VHOST_GET_VRING_BASE:
644                 s.index = idx;
645                 s.num = vq->last_avail_idx;
646                 if (copy_to_user(argp, &s, sizeof s))
647                         r = -EFAULT;
648                 break;
649         case VHOST_SET_VRING_ADDR:
650                 if (copy_from_user(&a, argp, sizeof a)) {
651                         r = -EFAULT;
652                         break;
653                 }
654                 if (a.flags & ~(0x1 << VHOST_VRING_F_LOG)) {
655                         r = -EOPNOTSUPP;
656                         break;
657                 }
658                 /* For 32bit, verify that the top 32bits of the user
659                    data are set to zero. */
660                 if ((u64)(unsigned long)a.desc_user_addr != a.desc_user_addr ||
661                     (u64)(unsigned long)a.used_user_addr != a.used_user_addr ||
662                     (u64)(unsigned long)a.avail_user_addr != a.avail_user_addr) {
663                         r = -EFAULT;
664                         break;
665                 }
666                 if ((a.avail_user_addr & (sizeof *vq->avail->ring - 1)) ||
667                     (a.used_user_addr & (sizeof *vq->used->ring - 1)) ||
668                     (a.log_guest_addr & (sizeof *vq->used->ring - 1))) {
669                         r = -EINVAL;
670                         break;
671                 }
672
673                 /* We only verify access here if backend is configured.
674                  * If it is not, we don't as size might not have been setup.
675                  * We will verify when backend is configured. */
676                 if (vq->private_data) {
677                         if (!vq_access_ok(vq->num,
678                                 (void __user *)(unsigned long)a.desc_user_addr,
679                                 (void __user *)(unsigned long)a.avail_user_addr,
680                                 (void __user *)(unsigned long)a.used_user_addr)) {
681                                 r = -EINVAL;
682                                 break;
683                         }
684
685                         /* Also validate log access for used ring if enabled. */
686                         if ((a.flags & (0x1 << VHOST_VRING_F_LOG)) &&
687                             !log_access_ok(vq->log_base, a.log_guest_addr,
688                                            sizeof *vq->used +
689                                            vq->num * sizeof *vq->used->ring)) {
690                                 r = -EINVAL;
691                                 break;
692                         }
693                 }
694
695                 r = init_used(vq, (struct vring_used __user *)(unsigned long)
696                               a.used_user_addr);
697                 if (r)
698                         break;
699                 vq->log_used = !!(a.flags & (0x1 << VHOST_VRING_F_LOG));
700                 vq->desc = (void __user *)(unsigned long)a.desc_user_addr;
701                 vq->avail = (void __user *)(unsigned long)a.avail_user_addr;
702                 vq->log_addr = a.log_guest_addr;
703                 vq->used = (void __user *)(unsigned long)a.used_user_addr;
704                 break;
705         case VHOST_SET_VRING_KICK:
706                 if (copy_from_user(&f, argp, sizeof f)) {
707                         r = -EFAULT;
708                         break;
709                 }
710                 eventfp = f.fd == -1 ? NULL : eventfd_fget(f.fd);
711                 if (IS_ERR(eventfp)) {
712                         r = PTR_ERR(eventfp);
713                         break;
714                 }
715                 if (eventfp != vq->kick) {
716                         pollstop = filep = vq->kick;
717                         pollstart = vq->kick = eventfp;
718                 } else
719                         filep = eventfp;
720                 break;
721         case VHOST_SET_VRING_CALL:
722                 if (copy_from_user(&f, argp, sizeof f)) {
723                         r = -EFAULT;
724                         break;
725                 }
726                 eventfp = f.fd == -1 ? NULL : eventfd_fget(f.fd);
727                 if (IS_ERR(eventfp)) {
728                         r = PTR_ERR(eventfp);
729                         break;
730                 }
731                 if (eventfp != vq->call) {
732                         filep = vq->call;
733                         ctx = vq->call_ctx;
734                         vq->call = eventfp;
735                         vq->call_ctx = eventfp ?
736                                 eventfd_ctx_fileget(eventfp) : NULL;
737                 } else
738                         filep = eventfp;
739                 break;
740         case VHOST_SET_VRING_ERR:
741                 if (copy_from_user(&f, argp, sizeof f)) {
742                         r = -EFAULT;
743                         break;
744                 }
745                 eventfp = f.fd == -1 ? NULL : eventfd_fget(f.fd);
746                 if (IS_ERR(eventfp)) {
747                         r = PTR_ERR(eventfp);
748                         break;
749                 }
750                 if (eventfp != vq->error) {
751                         filep = vq->error;
752                         vq->error = eventfp;
753                         ctx = vq->error_ctx;
754                         vq->error_ctx = eventfp ?
755                                 eventfd_ctx_fileget(eventfp) : NULL;
756                 } else
757                         filep = eventfp;
758                 break;
759         default:
760                 r = -ENOIOCTLCMD;
761         }
762
763         if (pollstop && vq->handle_kick)
764                 vhost_poll_stop(&vq->poll);
765
766         if (ctx)
767                 eventfd_ctx_put(ctx);
768         if (filep)
769                 fput(filep);
770
771         if (pollstart && vq->handle_kick)
772                 vhost_poll_start(&vq->poll, vq->kick);
773
774         mutex_unlock(&vq->mutex);
775
776         if (pollstop && vq->handle_kick)
777                 vhost_poll_flush(&vq->poll);
778         return r;
779 }
780
781 /* Caller must have device mutex */
782 long vhost_dev_ioctl(struct vhost_dev *d, unsigned int ioctl, unsigned long arg)
783 {
784         void __user *argp = (void __user *)arg;
785         struct file *eventfp, *filep = NULL;
786         struct eventfd_ctx *ctx = NULL;
787         u64 p;
788         long r;
789         int i, fd;
790
791         /* If you are not the owner, you can become one */
792         if (ioctl == VHOST_SET_OWNER) {
793                 r = vhost_dev_set_owner(d);
794                 goto done;
795         }
796
797         /* You must be the owner to do anything else */
798         r = vhost_dev_check_owner(d);
799         if (r)
800                 goto done;
801
802         switch (ioctl) {
803         case VHOST_SET_MEM_TABLE:
804                 r = vhost_set_memory(d, argp);
805                 break;
806         case VHOST_SET_LOG_BASE:
807                 if (copy_from_user(&p, argp, sizeof p)) {
808                         r = -EFAULT;
809                         break;
810                 }
811                 if ((u64)(unsigned long)p != p) {
812                         r = -EFAULT;
813                         break;
814                 }
815                 for (i = 0; i < d->nvqs; ++i) {
816                         struct vhost_virtqueue *vq;
817                         void __user *base = (void __user *)(unsigned long)p;
818                         vq = d->vqs + i;
819                         mutex_lock(&vq->mutex);
820                         /* If ring is inactive, will check when it's enabled. */
821                         if (vq->private_data && !vq_log_access_ok(vq, base))
822                                 r = -EFAULT;
823                         else
824                                 vq->log_base = base;
825                         mutex_unlock(&vq->mutex);
826                 }
827                 break;
828         case VHOST_SET_LOG_FD:
829                 r = get_user(fd, (int __user *)argp);
830                 if (r < 0)
831                         break;
832                 eventfp = fd == -1 ? NULL : eventfd_fget(fd);
833                 if (IS_ERR(eventfp)) {
834                         r = PTR_ERR(eventfp);
835                         break;
836                 }
837                 if (eventfp != d->log_file) {
838                         filep = d->log_file;
839                         ctx = d->log_ctx;
840                         d->log_ctx = eventfp ?
841                                 eventfd_ctx_fileget(eventfp) : NULL;
842                 } else
843                         filep = eventfp;
844                 for (i = 0; i < d->nvqs; ++i) {
845                         mutex_lock(&d->vqs[i].mutex);
846                         d->vqs[i].log_ctx = d->log_ctx;
847                         mutex_unlock(&d->vqs[i].mutex);
848                 }
849                 if (ctx)
850                         eventfd_ctx_put(ctx);
851                 if (filep)
852                         fput(filep);
853                 break;
854         default:
855                 r = vhost_set_vring(d, ioctl, argp);
856                 break;
857         }
858 done:
859         return r;
860 }
861
862 static const struct vhost_memory_region *find_region(struct vhost_memory *mem,
863                                                      __u64 addr, __u32 len)
864 {
865         struct vhost_memory_region *reg;
866         int i;
867
868         /* linear search is not brilliant, but we really have on the order of 6
869          * regions in practice */
870         for (i = 0; i < mem->nregions; ++i) {
871                 reg = mem->regions + i;
872                 if (reg->guest_phys_addr <= addr &&
873                     reg->guest_phys_addr + reg->memory_size - 1 >= addr)
874                         return reg;
875         }
876         return NULL;
877 }
878
879 /* TODO: This is really inefficient.  We need something like get_user()
880  * (instruction directly accesses the data, with an exception table entry
881  * returning -EFAULT). See Documentation/x86/exception-tables.txt.
882  */
883 static int set_bit_to_user(int nr, void __user *addr)
884 {
885         unsigned long log = (unsigned long)addr;
886         struct page *page;
887         void *base;
888         int bit = nr + (log % PAGE_SIZE) * 8;
889         int r;
890
891         r = get_user_pages_fast(log, 1, 1, &page);
892         if (r < 0)
893                 return r;
894         BUG_ON(r != 1);
895         base = kmap_atomic(page, KM_USER0);
896         set_bit(bit, base);
897         kunmap_atomic(base, KM_USER0);
898         set_page_dirty_lock(page);
899         put_page(page);
900         return 0;
901 }
902
903 static int log_write(void __user *log_base,
904                      u64 write_address, u64 write_length)
905 {
906         u64 write_page = write_address / VHOST_PAGE_SIZE;
907         int r;
908
909         if (!write_length)
910                 return 0;
911         write_length += write_address % VHOST_PAGE_SIZE;
912         for (;;) {
913                 u64 base = (u64)(unsigned long)log_base;
914                 u64 log = base + write_page / 8;
915                 int bit = write_page % 8;
916                 if ((u64)(unsigned long)log != log)
917                         return -EFAULT;
918                 r = set_bit_to_user(bit, (void __user *)(unsigned long)log);
919                 if (r < 0)
920                         return r;
921                 if (write_length <= VHOST_PAGE_SIZE)
922                         break;
923                 write_length -= VHOST_PAGE_SIZE;
924                 write_page += 1;
925         }
926         return r;
927 }
928
929 int vhost_log_write(struct vhost_virtqueue *vq, struct vhost_log *log,
930                     unsigned int log_num, u64 len)
931 {
932         int i, r;
933
934         /* Make sure data written is seen before log. */
935         smp_wmb();
936         for (i = 0; i < log_num; ++i) {
937                 u64 l = min(log[i].len, len);
938                 r = log_write(vq->log_base, log[i].addr, l);
939                 if (r < 0)
940                         return r;
941                 len -= l;
942                 if (!len) {
943                         if (vq->log_ctx)
944                                 eventfd_signal(vq->log_ctx, 1);
945                         return 0;
946                 }
947         }
948         /* Length written exceeds what we have stored. This is a bug. */
949         BUG();
950         return 0;
951 }
952
953 static int translate_desc(struct vhost_dev *dev, u64 addr, u32 len,
954                           struct iovec iov[], int iov_size)
955 {
956         const struct vhost_memory_region *reg;
957         struct vhost_memory *mem;
958         struct iovec *_iov;
959         u64 s = 0;
960         int ret = 0;
961
962         rcu_read_lock();
963
964         mem = rcu_dereference(dev->memory);
965         while ((u64)len > s) {
966                 u64 size;
967                 if (unlikely(ret >= iov_size)) {
968                         ret = -ENOBUFS;
969                         break;
970                 }
971                 reg = find_region(mem, addr, len);
972                 if (unlikely(!reg)) {
973                         ret = -EFAULT;
974                         break;
975                 }
976                 _iov = iov + ret;
977                 size = reg->memory_size - addr + reg->guest_phys_addr;
978                 _iov->iov_len = min((u64)len, size);
979                 _iov->iov_base = (void __user *)(unsigned long)
980                         (reg->userspace_addr + addr - reg->guest_phys_addr);
981                 s += size;
982                 addr += size;
983                 ++ret;
984         }
985
986         rcu_read_unlock();
987         return ret;
988 }
989
990 /* Each buffer in the virtqueues is actually a chain of descriptors.  This
991  * function returns the next descriptor in the chain,
992  * or -1U if we're at the end. */
993 static unsigned next_desc(struct vring_desc *desc)
994 {
995         unsigned int next;
996
997         /* If this descriptor says it doesn't chain, we're done. */
998         if (!(desc->flags & VRING_DESC_F_NEXT))
999                 return -1U;
1000
1001         /* Check they're not leading us off end of descriptors. */
1002         next = desc->next;
1003         /* Make sure compiler knows to grab that: we don't want it changing! */
1004         /* We will use the result as an index in an array, so most
1005          * architectures only need a compiler barrier here. */
1006         read_barrier_depends();
1007
1008         return next;
1009 }
1010
1011 static int get_indirect(struct vhost_dev *dev, struct vhost_virtqueue *vq,
1012                         struct iovec iov[], unsigned int iov_size,
1013                         unsigned int *out_num, unsigned int *in_num,
1014                         struct vhost_log *log, unsigned int *log_num,
1015                         struct vring_desc *indirect)
1016 {
1017         struct vring_desc desc;
1018         unsigned int i = 0, count, found = 0;
1019         int ret;
1020
1021         /* Sanity check */
1022         if (unlikely(indirect->len % sizeof desc)) {
1023                 vq_err(vq, "Invalid length in indirect descriptor: "
1024                        "len 0x%llx not multiple of 0x%zx\n",
1025                        (unsigned long long)indirect->len,
1026                        sizeof desc);
1027                 return -EINVAL;
1028         }
1029
1030         ret = translate_desc(dev, indirect->addr, indirect->len, vq->indirect,
1031                              UIO_MAXIOV);
1032         if (unlikely(ret < 0)) {
1033                 vq_err(vq, "Translation failure %d in indirect.\n", ret);
1034                 return ret;
1035         }
1036
1037         /* We will use the result as an address to read from, so most
1038          * architectures only need a compiler barrier here. */
1039         read_barrier_depends();
1040
1041         count = indirect->len / sizeof desc;
1042         /* Buffers are chained via a 16 bit next field, so
1043          * we can have at most 2^16 of these. */
1044         if (unlikely(count > USHRT_MAX + 1)) {
1045                 vq_err(vq, "Indirect buffer length too big: %d\n",
1046                        indirect->len);
1047                 return -E2BIG;
1048         }
1049
1050         do {
1051                 unsigned iov_count = *in_num + *out_num;
1052                 if (unlikely(++found > count)) {
1053                         vq_err(vq, "Loop detected: last one at %u "
1054                                "indirect size %u\n",
1055                                i, count);
1056                         return -EINVAL;
1057                 }
1058                 if (unlikely(memcpy_fromiovec((unsigned char *)&desc,
1059                                               vq->indirect, sizeof desc))) {
1060                         vq_err(vq, "Failed indirect descriptor: idx %d, %zx\n",
1061                                i, (size_t)indirect->addr + i * sizeof desc);
1062                         return -EINVAL;
1063                 }
1064                 if (unlikely(desc.flags & VRING_DESC_F_INDIRECT)) {
1065                         vq_err(vq, "Nested indirect descriptor: idx %d, %zx\n",
1066                                i, (size_t)indirect->addr + i * sizeof desc);
1067                         return -EINVAL;
1068                 }
1069
1070                 ret = translate_desc(dev, desc.addr, desc.len, iov + iov_count,
1071                                      iov_size - iov_count);
1072                 if (unlikely(ret < 0)) {
1073                         vq_err(vq, "Translation failure %d indirect idx %d\n",
1074                                ret, i);
1075                         return ret;
1076                 }
1077                 /* If this is an input descriptor, increment that count. */
1078                 if (desc.flags & VRING_DESC_F_WRITE) {
1079                         *in_num += ret;
1080                         if (unlikely(log)) {
1081                                 log[*log_num].addr = desc.addr;
1082                                 log[*log_num].len = desc.len;
1083                                 ++*log_num;
1084                         }
1085                 } else {
1086                         /* If it's an output descriptor, they're all supposed
1087                          * to come before any input descriptors. */
1088                         if (unlikely(*in_num)) {
1089                                 vq_err(vq, "Indirect descriptor "
1090                                        "has out after in: idx %d\n", i);
1091                                 return -EINVAL;
1092                         }
1093                         *out_num += ret;
1094                 }
1095         } while ((i = next_desc(&desc)) != -1);
1096         return 0;
1097 }
1098
1099 /* This looks in the virtqueue and for the first available buffer, and converts
1100  * it to an iovec for convenient access.  Since descriptors consist of some
1101  * number of output then some number of input descriptors, it's actually two
1102  * iovecs, but we pack them into one and note how many of each there were.
1103  *
1104  * This function returns the descriptor number found, or vq->num (which is
1105  * never a valid descriptor number) if none was found.  A negative code is
1106  * returned on error. */
1107 int vhost_get_vq_desc(struct vhost_dev *dev, struct vhost_virtqueue *vq,
1108                       struct iovec iov[], unsigned int iov_size,
1109                       unsigned int *out_num, unsigned int *in_num,
1110                       struct vhost_log *log, unsigned int *log_num)
1111 {
1112         struct vring_desc desc;
1113         unsigned int i, head, found = 0;
1114         u16 last_avail_idx;
1115         int ret;
1116
1117         /* Check it isn't doing very strange things with descriptor numbers. */
1118         last_avail_idx = vq->last_avail_idx;
1119         if (unlikely(__get_user(vq->avail_idx, &vq->avail->idx))) {
1120                 vq_err(vq, "Failed to access avail idx at %p\n",
1121                        &vq->avail->idx);
1122                 return -EFAULT;
1123         }
1124
1125         if (unlikely((u16)(vq->avail_idx - last_avail_idx) > vq->num)) {
1126                 vq_err(vq, "Guest moved used index from %u to %u",
1127                        last_avail_idx, vq->avail_idx);
1128                 return -EFAULT;
1129         }
1130
1131         /* If there's nothing new since last we looked, return invalid. */
1132         if (vq->avail_idx == last_avail_idx)
1133                 return vq->num;
1134
1135         /* Only get avail ring entries after they have been exposed by guest. */
1136         smp_rmb();
1137
1138         /* Grab the next descriptor number they're advertising, and increment
1139          * the index we've seen. */
1140         if (unlikely(__get_user(head,
1141                                 &vq->avail->ring[last_avail_idx % vq->num]))) {
1142                 vq_err(vq, "Failed to read head: idx %d address %p\n",
1143                        last_avail_idx,
1144                        &vq->avail->ring[last_avail_idx % vq->num]);
1145                 return -EFAULT;
1146         }
1147
1148         /* If their number is silly, that's an error. */
1149         if (unlikely(head >= vq->num)) {
1150                 vq_err(vq, "Guest says index %u > %u is available",
1151                        head, vq->num);
1152                 return -EINVAL;
1153         }
1154
1155         /* When we start there are none of either input nor output. */
1156         *out_num = *in_num = 0;
1157         if (unlikely(log))
1158                 *log_num = 0;
1159
1160         i = head;
1161         do {
1162                 unsigned iov_count = *in_num + *out_num;
1163                 if (unlikely(i >= vq->num)) {
1164                         vq_err(vq, "Desc index is %u > %u, head = %u",
1165                                i, vq->num, head);
1166                         return -EINVAL;
1167                 }
1168                 if (unlikely(++found > vq->num)) {
1169                         vq_err(vq, "Loop detected: last one at %u "
1170                                "vq size %u head %u\n",
1171                                i, vq->num, head);
1172                         return -EINVAL;
1173                 }
1174                 ret = __copy_from_user(&desc, vq->desc + i, sizeof desc);
1175                 if (unlikely(ret)) {
1176                         vq_err(vq, "Failed to get descriptor: idx %d addr %p\n",
1177                                i, vq->desc + i);
1178                         return -EFAULT;
1179                 }
1180                 if (desc.flags & VRING_DESC_F_INDIRECT) {
1181                         ret = get_indirect(dev, vq, iov, iov_size,
1182                                            out_num, in_num,
1183                                            log, log_num, &desc);
1184                         if (unlikely(ret < 0)) {
1185                                 vq_err(vq, "Failure detected "
1186                                        "in indirect descriptor at idx %d\n", i);
1187                                 return ret;
1188                         }
1189                         continue;
1190                 }
1191
1192                 ret = translate_desc(dev, desc.addr, desc.len, iov + iov_count,
1193                                      iov_size - iov_count);
1194                 if (unlikely(ret < 0)) {
1195                         vq_err(vq, "Translation failure %d descriptor idx %d\n",
1196                                ret, i);
1197                         return ret;
1198                 }
1199                 if (desc.flags & VRING_DESC_F_WRITE) {
1200                         /* If this is an input descriptor,
1201                          * increment that count. */
1202                         *in_num += ret;
1203                         if (unlikely(log)) {
1204                                 log[*log_num].addr = desc.addr;
1205                                 log[*log_num].len = desc.len;
1206                                 ++*log_num;
1207                         }
1208                 } else {
1209                         /* If it's an output descriptor, they're all supposed
1210                          * to come before any input descriptors. */
1211                         if (unlikely(*in_num)) {
1212                                 vq_err(vq, "Descriptor has out after in: "
1213                                        "idx %d\n", i);
1214                                 return -EINVAL;
1215                         }
1216                         *out_num += ret;
1217                 }
1218         } while ((i = next_desc(&desc)) != -1);
1219
1220         /* On success, increment avail index. */
1221         vq->last_avail_idx++;
1222         return head;
1223 }
1224
1225 /* Reverse the effect of vhost_get_vq_desc. Useful for error handling. */
1226 void vhost_discard_vq_desc(struct vhost_virtqueue *vq, int n)
1227 {
1228         vq->last_avail_idx -= n;
1229 }
1230
1231 /* After we've used one of their buffers, we tell them about it.  We'll then
1232  * want to notify the guest, using eventfd. */
1233 int vhost_add_used(struct vhost_virtqueue *vq, unsigned int head, int len)
1234 {
1235         struct vring_used_elem __user *used;
1236
1237         /* The virtqueue contains a ring of used buffers.  Get a pointer to the
1238          * next entry in that used ring. */
1239         used = &vq->used->ring[vq->last_used_idx % vq->num];
1240         if (__put_user(head, &used->id)) {
1241                 vq_err(vq, "Failed to write used id");
1242                 return -EFAULT;
1243         }
1244         if (__put_user(len, &used->len)) {
1245                 vq_err(vq, "Failed to write used len");
1246                 return -EFAULT;
1247         }
1248         /* Make sure buffer is written before we update index. */
1249         smp_wmb();
1250         if (__put_user(vq->last_used_idx + 1, &vq->used->idx)) {
1251                 vq_err(vq, "Failed to increment used idx");
1252                 return -EFAULT;
1253         }
1254         if (unlikely(vq->log_used)) {
1255                 /* Make sure data is seen before log. */
1256                 smp_wmb();
1257                 /* Log used ring entry write. */
1258                 log_write(vq->log_base,
1259                           vq->log_addr +
1260                            ((void __user *)used - (void __user *)vq->used),
1261                           sizeof *used);
1262                 /* Log used index update. */
1263                 log_write(vq->log_base,
1264                           vq->log_addr + offsetof(struct vring_used, idx),
1265                           sizeof vq->used->idx);
1266                 if (vq->log_ctx)
1267                         eventfd_signal(vq->log_ctx, 1);
1268         }
1269         vq->last_used_idx++;
1270         return 0;
1271 }
1272
1273 static int __vhost_add_used_n(struct vhost_virtqueue *vq,
1274                             struct vring_used_elem *heads,
1275                             unsigned count)
1276 {
1277         struct vring_used_elem __user *used;
1278         int start;
1279
1280         start = vq->last_used_idx % vq->num;
1281         used = vq->used->ring + start;
1282         if (__copy_to_user(used, heads, count * sizeof *used)) {
1283                 vq_err(vq, "Failed to write used");
1284                 return -EFAULT;
1285         }
1286         if (unlikely(vq->log_used)) {
1287                 /* Make sure data is seen before log. */
1288                 smp_wmb();
1289                 /* Log used ring entry write. */
1290                 log_write(vq->log_base,
1291                           vq->log_addr +
1292                            ((void __user *)used - (void __user *)vq->used),
1293                           count * sizeof *used);
1294         }
1295         vq->last_used_idx += count;
1296         return 0;
1297 }
1298
1299 /* After we've used one of their buffers, we tell them about it.  We'll then
1300  * want to notify the guest, using eventfd. */
1301 int vhost_add_used_n(struct vhost_virtqueue *vq, struct vring_used_elem *heads,
1302                      unsigned count)
1303 {
1304         int start, n, r;
1305
1306         start = vq->last_used_idx % vq->num;
1307         n = vq->num - start;
1308         if (n < count) {
1309                 r = __vhost_add_used_n(vq, heads, n);
1310                 if (r < 0)
1311                         return r;
1312                 heads += n;
1313                 count -= n;
1314         }
1315         r = __vhost_add_used_n(vq, heads, count);
1316
1317         /* Make sure buffer is written before we update index. */
1318         smp_wmb();
1319         if (put_user(vq->last_used_idx, &vq->used->idx)) {
1320                 vq_err(vq, "Failed to increment used idx");
1321                 return -EFAULT;
1322         }
1323         if (unlikely(vq->log_used)) {
1324                 /* Log used index update. */
1325                 log_write(vq->log_base,
1326                           vq->log_addr + offsetof(struct vring_used, idx),
1327                           sizeof vq->used->idx);
1328                 if (vq->log_ctx)
1329                         eventfd_signal(vq->log_ctx, 1);
1330         }
1331         return r;
1332 }
1333
1334 /* This actually signals the guest, using eventfd. */
1335 void vhost_signal(struct vhost_dev *dev, struct vhost_virtqueue *vq)
1336 {
1337         __u16 flags;
1338
1339         /* Flush out used index updates. This is paired
1340          * with the barrier that the Guest executes when enabling
1341          * interrupts. */
1342         smp_mb();
1343
1344         if (__get_user(flags, &vq->avail->flags)) {
1345                 vq_err(vq, "Failed to get flags");
1346                 return;
1347         }
1348
1349         /* If they don't want an interrupt, don't signal, unless empty. */
1350         if ((flags & VRING_AVAIL_F_NO_INTERRUPT) &&
1351             (vq->avail_idx != vq->last_avail_idx ||
1352              !vhost_has_feature(dev, VIRTIO_F_NOTIFY_ON_EMPTY)))
1353                 return;
1354
1355         /* Signal the Guest tell them we used something up. */
1356         if (vq->call_ctx)
1357                 eventfd_signal(vq->call_ctx, 1);
1358 }
1359
1360 /* And here's the combo meal deal.  Supersize me! */
1361 void vhost_add_used_and_signal(struct vhost_dev *dev,
1362                                struct vhost_virtqueue *vq,
1363                                unsigned int head, int len)
1364 {
1365         vhost_add_used(vq, head, len);
1366         vhost_signal(dev, vq);
1367 }
1368
1369 /* multi-buffer version of vhost_add_used_and_signal */
1370 void vhost_add_used_and_signal_n(struct vhost_dev *dev,
1371                                  struct vhost_virtqueue *vq,
1372                                  struct vring_used_elem *heads, unsigned count)
1373 {
1374         vhost_add_used_n(vq, heads, count);
1375         vhost_signal(dev, vq);
1376 }
1377
1378 /* OK, now we need to know about added descriptors. */
1379 bool vhost_enable_notify(struct vhost_virtqueue *vq)
1380 {
1381         u16 avail_idx;
1382         int r;
1383
1384         if (!(vq->used_flags & VRING_USED_F_NO_NOTIFY))
1385                 return false;
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                 return false;
1392         }
1393         /* They could have slipped one in as we were doing that: make
1394          * sure it's written, then check again. */
1395         smp_mb();
1396         r = __get_user(avail_idx, &vq->avail->idx);
1397         if (r) {
1398                 vq_err(vq, "Failed to check avail idx at %p: %d\n",
1399                        &vq->avail->idx, r);
1400                 return false;
1401         }
1402
1403         return avail_idx != vq->avail_idx;
1404 }
1405
1406 /* We don't need to be notified again. */
1407 void vhost_disable_notify(struct vhost_virtqueue *vq)
1408 {
1409         int r;
1410
1411         if (vq->used_flags & VRING_USED_F_NO_NOTIFY)
1412                 return;
1413         vq->used_flags |= VRING_USED_F_NO_NOTIFY;
1414         r = put_user(vq->used_flags, &vq->used->flags);
1415         if (r)
1416                 vq_err(vq, "Failed to enable notification at %p: %d\n",
1417                        &vq->used->flags, r);
1418 }