vhost: support event index
[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 #define vhost_used_event(vq) ((u16 __user *)&vq->avail->ring[vq->num])
41 #define vhost_avail_event(vq) ((u16 __user *)&vq->used->ring[vq->num])
42
43 static void vhost_poll_func(struct file *file, wait_queue_head_t *wqh,
44                             poll_table *pt)
45 {
46         struct vhost_poll *poll;
47
48         poll = container_of(pt, struct vhost_poll, table);
49         poll->wqh = wqh;
50         add_wait_queue(wqh, &poll->wait);
51 }
52
53 static int vhost_poll_wakeup(wait_queue_t *wait, unsigned mode, int sync,
54                              void *key)
55 {
56         struct vhost_poll *poll = container_of(wait, struct vhost_poll, wait);
57
58         if (!((unsigned long)key & poll->mask))
59                 return 0;
60
61         vhost_poll_queue(poll);
62         return 0;
63 }
64
65 static void vhost_work_init(struct vhost_work *work, vhost_work_fn_t fn)
66 {
67         INIT_LIST_HEAD(&work->node);
68         work->fn = fn;
69         init_waitqueue_head(&work->done);
70         work->flushing = 0;
71         work->queue_seq = work->done_seq = 0;
72 }
73
74 /* Init poll structure */
75 void vhost_poll_init(struct vhost_poll *poll, vhost_work_fn_t fn,
76                      unsigned long mask, struct vhost_dev *dev)
77 {
78         init_waitqueue_func_entry(&poll->wait, vhost_poll_wakeup);
79         init_poll_funcptr(&poll->table, vhost_poll_func);
80         poll->mask = mask;
81         poll->dev = dev;
82
83         vhost_work_init(&poll->work, fn);
84 }
85
86 /* Start polling a file. We add ourselves to file's wait queue. The caller must
87  * keep a reference to a file until after vhost_poll_stop is called. */
88 void vhost_poll_start(struct vhost_poll *poll, struct file *file)
89 {
90         unsigned long mask;
91
92         mask = file->f_op->poll(file, &poll->table);
93         if (mask)
94                 vhost_poll_wakeup(&poll->wait, 0, 0, (void *)mask);
95 }
96
97 /* Stop polling a file. After this function returns, it becomes safe to drop the
98  * file reference. You must also flush afterwards. */
99 void vhost_poll_stop(struct vhost_poll *poll)
100 {
101         remove_wait_queue(poll->wqh, &poll->wait);
102 }
103
104 static bool vhost_work_seq_done(struct vhost_dev *dev, struct vhost_work *work,
105                                 unsigned seq)
106 {
107         int left;
108
109         spin_lock_irq(&dev->work_lock);
110         left = seq - work->done_seq;
111         spin_unlock_irq(&dev->work_lock);
112         return left <= 0;
113 }
114
115 static void vhost_work_flush(struct vhost_dev *dev, struct vhost_work *work)
116 {
117         unsigned seq;
118         int flushing;
119
120         spin_lock_irq(&dev->work_lock);
121         seq = work->queue_seq;
122         work->flushing++;
123         spin_unlock_irq(&dev->work_lock);
124         wait_event(work->done, vhost_work_seq_done(dev, work, seq));
125         spin_lock_irq(&dev->work_lock);
126         flushing = --work->flushing;
127         spin_unlock_irq(&dev->work_lock);
128         BUG_ON(flushing < 0);
129 }
130
131 /* Flush any work that has been scheduled. When calling this, don't hold any
132  * locks that are also used by the callback. */
133 void vhost_poll_flush(struct vhost_poll *poll)
134 {
135         vhost_work_flush(poll->dev, &poll->work);
136 }
137
138 static inline void vhost_work_queue(struct vhost_dev *dev,
139                                     struct vhost_work *work)
140 {
141         unsigned long flags;
142
143         spin_lock_irqsave(&dev->work_lock, flags);
144         if (list_empty(&work->node)) {
145                 list_add_tail(&work->node, &dev->work_list);
146                 work->queue_seq++;
147                 wake_up_process(dev->worker);
148         }
149         spin_unlock_irqrestore(&dev->work_lock, flags);
150 }
151
152 void vhost_poll_queue(struct vhost_poll *poll)
153 {
154         vhost_work_queue(poll->dev, &poll->work);
155 }
156
157 static void vhost_vq_reset(struct vhost_dev *dev,
158                            struct vhost_virtqueue *vq)
159 {
160         vq->num = 1;
161         vq->desc = NULL;
162         vq->avail = NULL;
163         vq->used = NULL;
164         vq->last_avail_idx = 0;
165         vq->avail_idx = 0;
166         vq->last_used_idx = 0;
167         vq->signalled_used = 0;
168         vq->signalled_used_valid = false;
169         vq->used_flags = 0;
170         vq->log_used = false;
171         vq->log_addr = -1ull;
172         vq->vhost_hlen = 0;
173         vq->sock_hlen = 0;
174         vq->private_data = NULL;
175         vq->log_base = NULL;
176         vq->error_ctx = NULL;
177         vq->error = NULL;
178         vq->kick = NULL;
179         vq->call_ctx = NULL;
180         vq->call = NULL;
181         vq->log_ctx = NULL;
182 }
183
184 static int vhost_worker(void *data)
185 {
186         struct vhost_dev *dev = data;
187         struct vhost_work *work = NULL;
188         unsigned uninitialized_var(seq);
189
190         use_mm(dev->mm);
191
192         for (;;) {
193                 /* mb paired w/ kthread_stop */
194                 set_current_state(TASK_INTERRUPTIBLE);
195
196                 spin_lock_irq(&dev->work_lock);
197                 if (work) {
198                         work->done_seq = seq;
199                         if (work->flushing)
200                                 wake_up_all(&work->done);
201                 }
202
203                 if (kthread_should_stop()) {
204                         spin_unlock_irq(&dev->work_lock);
205                         __set_current_state(TASK_RUNNING);
206                         break;
207                 }
208                 if (!list_empty(&dev->work_list)) {
209                         work = list_first_entry(&dev->work_list,
210                                                 struct vhost_work, node);
211                         list_del_init(&work->node);
212                         seq = work->queue_seq;
213                 } else
214                         work = NULL;
215                 spin_unlock_irq(&dev->work_lock);
216
217                 if (work) {
218                         __set_current_state(TASK_RUNNING);
219                         work->fn(work);
220                 } else
221                         schedule();
222
223         }
224         unuse_mm(dev->mm);
225         return 0;
226 }
227
228 /* Helper to allocate iovec buffers for all vqs. */
229 static long vhost_dev_alloc_iovecs(struct vhost_dev *dev)
230 {
231         int i;
232
233         for (i = 0; i < dev->nvqs; ++i) {
234                 dev->vqs[i].indirect = kmalloc(sizeof *dev->vqs[i].indirect *
235                                                UIO_MAXIOV, GFP_KERNEL);
236                 dev->vqs[i].log = kmalloc(sizeof *dev->vqs[i].log * UIO_MAXIOV,
237                                           GFP_KERNEL);
238                 dev->vqs[i].heads = kmalloc(sizeof *dev->vqs[i].heads *
239                                             UIO_MAXIOV, GFP_KERNEL);
240
241                 if (!dev->vqs[i].indirect || !dev->vqs[i].log ||
242                         !dev->vqs[i].heads)
243                         goto err_nomem;
244         }
245         return 0;
246
247 err_nomem:
248         for (; i >= 0; --i) {
249                 kfree(dev->vqs[i].indirect);
250                 kfree(dev->vqs[i].log);
251                 kfree(dev->vqs[i].heads);
252         }
253         return -ENOMEM;
254 }
255
256 static void vhost_dev_free_iovecs(struct vhost_dev *dev)
257 {
258         int i;
259
260         for (i = 0; i < dev->nvqs; ++i) {
261                 kfree(dev->vqs[i].indirect);
262                 dev->vqs[i].indirect = NULL;
263                 kfree(dev->vqs[i].log);
264                 dev->vqs[i].log = NULL;
265                 kfree(dev->vqs[i].heads);
266                 dev->vqs[i].heads = NULL;
267         }
268 }
269
270 long vhost_dev_init(struct vhost_dev *dev,
271                     struct vhost_virtqueue *vqs, int nvqs)
272 {
273         int i;
274
275         dev->vqs = vqs;
276         dev->nvqs = nvqs;
277         mutex_init(&dev->mutex);
278         dev->log_ctx = NULL;
279         dev->log_file = NULL;
280         dev->memory = NULL;
281         dev->mm = NULL;
282         spin_lock_init(&dev->work_lock);
283         INIT_LIST_HEAD(&dev->work_list);
284         dev->worker = NULL;
285
286         for (i = 0; i < dev->nvqs; ++i) {
287                 dev->vqs[i].log = NULL;
288                 dev->vqs[i].indirect = NULL;
289                 dev->vqs[i].heads = NULL;
290                 dev->vqs[i].dev = dev;
291                 mutex_init(&dev->vqs[i].mutex);
292                 vhost_vq_reset(dev, dev->vqs + i);
293                 if (dev->vqs[i].handle_kick)
294                         vhost_poll_init(&dev->vqs[i].poll,
295                                         dev->vqs[i].handle_kick, POLLIN, dev);
296         }
297
298         return 0;
299 }
300
301 /* Caller should have device mutex */
302 long vhost_dev_check_owner(struct vhost_dev *dev)
303 {
304         /* Are you the owner? If not, I don't think you mean to do that */
305         return dev->mm == current->mm ? 0 : -EPERM;
306 }
307
308 struct vhost_attach_cgroups_struct {
309         struct vhost_work work;
310         struct task_struct *owner;
311         int ret;
312 };
313
314 static void vhost_attach_cgroups_work(struct vhost_work *work)
315 {
316         struct vhost_attach_cgroups_struct *s;
317
318         s = container_of(work, struct vhost_attach_cgroups_struct, work);
319         s->ret = cgroup_attach_task_all(s->owner, current);
320 }
321
322 static int vhost_attach_cgroups(struct vhost_dev *dev)
323 {
324         struct vhost_attach_cgroups_struct attach;
325
326         attach.owner = current;
327         vhost_work_init(&attach.work, vhost_attach_cgroups_work);
328         vhost_work_queue(dev, &attach.work);
329         vhost_work_flush(dev, &attach.work);
330         return attach.ret;
331 }
332
333 /* Caller should have device mutex */
334 static long vhost_dev_set_owner(struct vhost_dev *dev)
335 {
336         struct task_struct *worker;
337         int err;
338
339         /* Is there an owner already? */
340         if (dev->mm) {
341                 err = -EBUSY;
342                 goto err_mm;
343         }
344
345         /* No owner, become one */
346         dev->mm = get_task_mm(current);
347         worker = kthread_create(vhost_worker, dev, "vhost-%d", current->pid);
348         if (IS_ERR(worker)) {
349                 err = PTR_ERR(worker);
350                 goto err_worker;
351         }
352
353         dev->worker = worker;
354         wake_up_process(worker);        /* avoid contributing to loadavg */
355
356         err = vhost_attach_cgroups(dev);
357         if (err)
358                 goto err_cgroup;
359
360         err = vhost_dev_alloc_iovecs(dev);
361         if (err)
362                 goto err_cgroup;
363
364         return 0;
365 err_cgroup:
366         kthread_stop(worker);
367         dev->worker = NULL;
368 err_worker:
369         if (dev->mm)
370                 mmput(dev->mm);
371         dev->mm = NULL;
372 err_mm:
373         return err;
374 }
375
376 /* Caller should have device mutex */
377 long vhost_dev_reset_owner(struct vhost_dev *dev)
378 {
379         struct vhost_memory *memory;
380
381         /* Restore memory to default empty mapping. */
382         memory = kmalloc(offsetof(struct vhost_memory, regions), GFP_KERNEL);
383         if (!memory)
384                 return -ENOMEM;
385
386         vhost_dev_cleanup(dev);
387
388         memory->nregions = 0;
389         RCU_INIT_POINTER(dev->memory, memory);
390         return 0;
391 }
392
393 /* Caller should have device mutex */
394 void vhost_dev_cleanup(struct vhost_dev *dev)
395 {
396         int i;
397
398         for (i = 0; i < dev->nvqs; ++i) {
399                 if (dev->vqs[i].kick && dev->vqs[i].handle_kick) {
400                         vhost_poll_stop(&dev->vqs[i].poll);
401                         vhost_poll_flush(&dev->vqs[i].poll);
402                 }
403                 if (dev->vqs[i].error_ctx)
404                         eventfd_ctx_put(dev->vqs[i].error_ctx);
405                 if (dev->vqs[i].error)
406                         fput(dev->vqs[i].error);
407                 if (dev->vqs[i].kick)
408                         fput(dev->vqs[i].kick);
409                 if (dev->vqs[i].call_ctx)
410                         eventfd_ctx_put(dev->vqs[i].call_ctx);
411                 if (dev->vqs[i].call)
412                         fput(dev->vqs[i].call);
413                 vhost_vq_reset(dev, dev->vqs + i);
414         }
415         vhost_dev_free_iovecs(dev);
416         if (dev->log_ctx)
417                 eventfd_ctx_put(dev->log_ctx);
418         dev->log_ctx = NULL;
419         if (dev->log_file)
420                 fput(dev->log_file);
421         dev->log_file = NULL;
422         /* No one will access memory at this point */
423         kfree(rcu_dereference_protected(dev->memory,
424                                         lockdep_is_held(&dev->mutex)));
425         RCU_INIT_POINTER(dev->memory, NULL);
426         WARN_ON(!list_empty(&dev->work_list));
427         if (dev->worker) {
428                 kthread_stop(dev->worker);
429                 dev->worker = NULL;
430         }
431         if (dev->mm)
432                 mmput(dev->mm);
433         dev->mm = NULL;
434 }
435
436 static int log_access_ok(void __user *log_base, u64 addr, unsigned long sz)
437 {
438         u64 a = addr / VHOST_PAGE_SIZE / 8;
439
440         /* Make sure 64 bit math will not overflow. */
441         if (a > ULONG_MAX - (unsigned long)log_base ||
442             a + (unsigned long)log_base > ULONG_MAX)
443                 return 0;
444
445         return access_ok(VERIFY_WRITE, log_base + a,
446                          (sz + VHOST_PAGE_SIZE * 8 - 1) / VHOST_PAGE_SIZE / 8);
447 }
448
449 /* Caller should have vq mutex and device mutex. */
450 static int vq_memory_access_ok(void __user *log_base, struct vhost_memory *mem,
451                                int log_all)
452 {
453         int i;
454
455         if (!mem)
456                 return 0;
457
458         for (i = 0; i < mem->nregions; ++i) {
459                 struct vhost_memory_region *m = mem->regions + i;
460                 unsigned long a = m->userspace_addr;
461                 if (m->memory_size > ULONG_MAX)
462                         return 0;
463                 else if (!access_ok(VERIFY_WRITE, (void __user *)a,
464                                     m->memory_size))
465                         return 0;
466                 else if (log_all && !log_access_ok(log_base,
467                                                    m->guest_phys_addr,
468                                                    m->memory_size))
469                         return 0;
470         }
471         return 1;
472 }
473
474 /* Can we switch to this memory table? */
475 /* Caller should have device mutex but not vq mutex */
476 static int memory_access_ok(struct vhost_dev *d, struct vhost_memory *mem,
477                             int log_all)
478 {
479         int i;
480
481         for (i = 0; i < d->nvqs; ++i) {
482                 int ok;
483                 mutex_lock(&d->vqs[i].mutex);
484                 /* If ring is inactive, will check when it's enabled. */
485                 if (d->vqs[i].private_data)
486                         ok = vq_memory_access_ok(d->vqs[i].log_base, mem,
487                                                  log_all);
488                 else
489                         ok = 1;
490                 mutex_unlock(&d->vqs[i].mutex);
491                 if (!ok)
492                         return 0;
493         }
494         return 1;
495 }
496
497 static int vq_access_ok(struct vhost_dev *d, unsigned int num,
498                         struct vring_desc __user *desc,
499                         struct vring_avail __user *avail,
500                         struct vring_used __user *used)
501 {
502         size_t s = vhost_has_feature(d, VIRTIO_RING_F_EVENT_IDX) ? 2 : 0;
503         return access_ok(VERIFY_READ, desc, num * sizeof *desc) &&
504                access_ok(VERIFY_READ, avail,
505                          sizeof *avail + num * sizeof *avail->ring + s) &&
506                access_ok(VERIFY_WRITE, used,
507                         sizeof *used + num * sizeof *used->ring + s);
508 }
509
510 /* Can we log writes? */
511 /* Caller should have device mutex but not vq mutex */
512 int vhost_log_access_ok(struct vhost_dev *dev)
513 {
514         struct vhost_memory *mp;
515
516         mp = rcu_dereference_protected(dev->memory,
517                                        lockdep_is_held(&dev->mutex));
518         return memory_access_ok(dev, mp, 1);
519 }
520
521 /* Verify access for write logging. */
522 /* Caller should have vq mutex and device mutex */
523 static int vq_log_access_ok(struct vhost_dev *d, struct vhost_virtqueue *vq,
524                             void __user *log_base)
525 {
526         struct vhost_memory *mp;
527         size_t s = vhost_has_feature(d, VIRTIO_RING_F_EVENT_IDX) ? 2 : 0;
528
529         mp = rcu_dereference_protected(vq->dev->memory,
530                                        lockdep_is_held(&vq->mutex));
531         return vq_memory_access_ok(log_base, mp,
532                             vhost_has_feature(vq->dev, VHOST_F_LOG_ALL)) &&
533                 (!vq->log_used || log_access_ok(log_base, vq->log_addr,
534                                         sizeof *vq->used +
535                                         vq->num * sizeof *vq->used->ring + s));
536 }
537
538 /* Can we start vq? */
539 /* Caller should have vq mutex and device mutex */
540 int vhost_vq_access_ok(struct vhost_virtqueue *vq)
541 {
542         return vq_access_ok(vq->dev, vq->num, vq->desc, vq->avail, vq->used) &&
543                 vq_log_access_ok(vq->dev, vq, vq->log_base);
544 }
545
546 static long vhost_set_memory(struct vhost_dev *d, struct vhost_memory __user *m)
547 {
548         struct vhost_memory mem, *newmem, *oldmem;
549         unsigned long size = offsetof(struct vhost_memory, regions);
550
551         if (copy_from_user(&mem, m, size))
552                 return -EFAULT;
553         if (mem.padding)
554                 return -EOPNOTSUPP;
555         if (mem.nregions > VHOST_MEMORY_MAX_NREGIONS)
556                 return -E2BIG;
557         newmem = kmalloc(size + mem.nregions * sizeof *m->regions, GFP_KERNEL);
558         if (!newmem)
559                 return -ENOMEM;
560
561         memcpy(newmem, &mem, size);
562         if (copy_from_user(newmem->regions, m->regions,
563                            mem.nregions * sizeof *m->regions)) {
564                 kfree(newmem);
565                 return -EFAULT;
566         }
567
568         if (!memory_access_ok(d, newmem,
569                               vhost_has_feature(d, VHOST_F_LOG_ALL))) {
570                 kfree(newmem);
571                 return -EFAULT;
572         }
573         oldmem = rcu_dereference_protected(d->memory,
574                                            lockdep_is_held(&d->mutex));
575         rcu_assign_pointer(d->memory, newmem);
576         synchronize_rcu();
577         kfree(oldmem);
578         return 0;
579 }
580
581 static int init_used(struct vhost_virtqueue *vq,
582                      struct vring_used __user *used)
583 {
584         int r = put_user(vq->used_flags, &used->flags);
585
586         if (r)
587                 return r;
588         vq->signalled_used_valid = false;
589         return get_user(vq->last_used_idx, &used->idx);
590 }
591
592 static long vhost_set_vring(struct vhost_dev *d, int ioctl, void __user *argp)
593 {
594         struct file *eventfp, *filep = NULL,
595                     *pollstart = NULL, *pollstop = NULL;
596         struct eventfd_ctx *ctx = NULL;
597         u32 __user *idxp = argp;
598         struct vhost_virtqueue *vq;
599         struct vhost_vring_state s;
600         struct vhost_vring_file f;
601         struct vhost_vring_addr a;
602         u32 idx;
603         long r;
604
605         r = get_user(idx, idxp);
606         if (r < 0)
607                 return r;
608         if (idx >= d->nvqs)
609                 return -ENOBUFS;
610
611         vq = d->vqs + idx;
612
613         mutex_lock(&vq->mutex);
614
615         switch (ioctl) {
616         case VHOST_SET_VRING_NUM:
617                 /* Resizing ring with an active backend?
618                  * You don't want to do that. */
619                 if (vq->private_data) {
620                         r = -EBUSY;
621                         break;
622                 }
623                 if (copy_from_user(&s, argp, sizeof s)) {
624                         r = -EFAULT;
625                         break;
626                 }
627                 if (!s.num || s.num > 0xffff || (s.num & (s.num - 1))) {
628                         r = -EINVAL;
629                         break;
630                 }
631                 vq->num = s.num;
632                 break;
633         case VHOST_SET_VRING_BASE:
634                 /* Moving base with an active backend?
635                  * You don't want to do that. */
636                 if (vq->private_data) {
637                         r = -EBUSY;
638                         break;
639                 }
640                 if (copy_from_user(&s, argp, sizeof s)) {
641                         r = -EFAULT;
642                         break;
643                 }
644                 if (s.num > 0xffff) {
645                         r = -EINVAL;
646                         break;
647                 }
648                 vq->last_avail_idx = s.num;
649                 /* Forget the cached index value. */
650                 vq->avail_idx = vq->last_avail_idx;
651                 break;
652         case VHOST_GET_VRING_BASE:
653                 s.index = idx;
654                 s.num = vq->last_avail_idx;
655                 if (copy_to_user(argp, &s, sizeof s))
656                         r = -EFAULT;
657                 break;
658         case VHOST_SET_VRING_ADDR:
659                 if (copy_from_user(&a, argp, sizeof a)) {
660                         r = -EFAULT;
661                         break;
662                 }
663                 if (a.flags & ~(0x1 << VHOST_VRING_F_LOG)) {
664                         r = -EOPNOTSUPP;
665                         break;
666                 }
667                 /* For 32bit, verify that the top 32bits of the user
668                    data are set to zero. */
669                 if ((u64)(unsigned long)a.desc_user_addr != a.desc_user_addr ||
670                     (u64)(unsigned long)a.used_user_addr != a.used_user_addr ||
671                     (u64)(unsigned long)a.avail_user_addr != a.avail_user_addr) {
672                         r = -EFAULT;
673                         break;
674                 }
675                 if ((a.avail_user_addr & (sizeof *vq->avail->ring - 1)) ||
676                     (a.used_user_addr & (sizeof *vq->used->ring - 1)) ||
677                     (a.log_guest_addr & (sizeof *vq->used->ring - 1))) {
678                         r = -EINVAL;
679                         break;
680                 }
681
682                 /* We only verify access here if backend is configured.
683                  * If it is not, we don't as size might not have been setup.
684                  * We will verify when backend is configured. */
685                 if (vq->private_data) {
686                         if (!vq_access_ok(d, vq->num,
687                                 (void __user *)(unsigned long)a.desc_user_addr,
688                                 (void __user *)(unsigned long)a.avail_user_addr,
689                                 (void __user *)(unsigned long)a.used_user_addr)) {
690                                 r = -EINVAL;
691                                 break;
692                         }
693
694                         /* Also validate log access for used ring if enabled. */
695                         if ((a.flags & (0x1 << VHOST_VRING_F_LOG)) &&
696                             !log_access_ok(vq->log_base, a.log_guest_addr,
697                                            sizeof *vq->used +
698                                            vq->num * sizeof *vq->used->ring)) {
699                                 r = -EINVAL;
700                                 break;
701                         }
702                 }
703
704                 r = init_used(vq, (struct vring_used __user *)(unsigned long)
705                               a.used_user_addr);
706                 if (r)
707                         break;
708                 vq->log_used = !!(a.flags & (0x1 << VHOST_VRING_F_LOG));
709                 vq->desc = (void __user *)(unsigned long)a.desc_user_addr;
710                 vq->avail = (void __user *)(unsigned long)a.avail_user_addr;
711                 vq->log_addr = a.log_guest_addr;
712                 vq->used = (void __user *)(unsigned long)a.used_user_addr;
713                 break;
714         case VHOST_SET_VRING_KICK:
715                 if (copy_from_user(&f, argp, sizeof f)) {
716                         r = -EFAULT;
717                         break;
718                 }
719                 eventfp = f.fd == -1 ? NULL : eventfd_fget(f.fd);
720                 if (IS_ERR(eventfp)) {
721                         r = PTR_ERR(eventfp);
722                         break;
723                 }
724                 if (eventfp != vq->kick) {
725                         pollstop = filep = vq->kick;
726                         pollstart = vq->kick = eventfp;
727                 } else
728                         filep = eventfp;
729                 break;
730         case VHOST_SET_VRING_CALL:
731                 if (copy_from_user(&f, argp, sizeof f)) {
732                         r = -EFAULT;
733                         break;
734                 }
735                 eventfp = f.fd == -1 ? NULL : eventfd_fget(f.fd);
736                 if (IS_ERR(eventfp)) {
737                         r = PTR_ERR(eventfp);
738                         break;
739                 }
740                 if (eventfp != vq->call) {
741                         filep = vq->call;
742                         ctx = vq->call_ctx;
743                         vq->call = eventfp;
744                         vq->call_ctx = eventfp ?
745                                 eventfd_ctx_fileget(eventfp) : NULL;
746                 } else
747                         filep = eventfp;
748                 break;
749         case VHOST_SET_VRING_ERR:
750                 if (copy_from_user(&f, argp, sizeof f)) {
751                         r = -EFAULT;
752                         break;
753                 }
754                 eventfp = f.fd == -1 ? NULL : eventfd_fget(f.fd);
755                 if (IS_ERR(eventfp)) {
756                         r = PTR_ERR(eventfp);
757                         break;
758                 }
759                 if (eventfp != vq->error) {
760                         filep = vq->error;
761                         vq->error = eventfp;
762                         ctx = vq->error_ctx;
763                         vq->error_ctx = eventfp ?
764                                 eventfd_ctx_fileget(eventfp) : NULL;
765                 } else
766                         filep = eventfp;
767                 break;
768         default:
769                 r = -ENOIOCTLCMD;
770         }
771
772         if (pollstop && vq->handle_kick)
773                 vhost_poll_stop(&vq->poll);
774
775         if (ctx)
776                 eventfd_ctx_put(ctx);
777         if (filep)
778                 fput(filep);
779
780         if (pollstart && vq->handle_kick)
781                 vhost_poll_start(&vq->poll, vq->kick);
782
783         mutex_unlock(&vq->mutex);
784
785         if (pollstop && vq->handle_kick)
786                 vhost_poll_flush(&vq->poll);
787         return r;
788 }
789
790 /* Caller must have device mutex */
791 long vhost_dev_ioctl(struct vhost_dev *d, unsigned int ioctl, unsigned long arg)
792 {
793         void __user *argp = (void __user *)arg;
794         struct file *eventfp, *filep = NULL;
795         struct eventfd_ctx *ctx = NULL;
796         u64 p;
797         long r;
798         int i, fd;
799
800         /* If you are not the owner, you can become one */
801         if (ioctl == VHOST_SET_OWNER) {
802                 r = vhost_dev_set_owner(d);
803                 goto done;
804         }
805
806         /* You must be the owner to do anything else */
807         r = vhost_dev_check_owner(d);
808         if (r)
809                 goto done;
810
811         switch (ioctl) {
812         case VHOST_SET_MEM_TABLE:
813                 r = vhost_set_memory(d, argp);
814                 break;
815         case VHOST_SET_LOG_BASE:
816                 if (copy_from_user(&p, argp, sizeof p)) {
817                         r = -EFAULT;
818                         break;
819                 }
820                 if ((u64)(unsigned long)p != p) {
821                         r = -EFAULT;
822                         break;
823                 }
824                 for (i = 0; i < d->nvqs; ++i) {
825                         struct vhost_virtqueue *vq;
826                         void __user *base = (void __user *)(unsigned long)p;
827                         vq = d->vqs + i;
828                         mutex_lock(&vq->mutex);
829                         /* If ring is inactive, will check when it's enabled. */
830                         if (vq->private_data && !vq_log_access_ok(d, vq, base))
831                                 r = -EFAULT;
832                         else
833                                 vq->log_base = base;
834                         mutex_unlock(&vq->mutex);
835                 }
836                 break;
837         case VHOST_SET_LOG_FD:
838                 r = get_user(fd, (int __user *)argp);
839                 if (r < 0)
840                         break;
841                 eventfp = fd == -1 ? NULL : eventfd_fget(fd);
842                 if (IS_ERR(eventfp)) {
843                         r = PTR_ERR(eventfp);
844                         break;
845                 }
846                 if (eventfp != d->log_file) {
847                         filep = d->log_file;
848                         ctx = d->log_ctx;
849                         d->log_ctx = eventfp ?
850                                 eventfd_ctx_fileget(eventfp) : NULL;
851                 } else
852                         filep = eventfp;
853                 for (i = 0; i < d->nvqs; ++i) {
854                         mutex_lock(&d->vqs[i].mutex);
855                         d->vqs[i].log_ctx = d->log_ctx;
856                         mutex_unlock(&d->vqs[i].mutex);
857                 }
858                 if (ctx)
859                         eventfd_ctx_put(ctx);
860                 if (filep)
861                         fput(filep);
862                 break;
863         default:
864                 r = vhost_set_vring(d, ioctl, argp);
865                 break;
866         }
867 done:
868         return r;
869 }
870
871 static const struct vhost_memory_region *find_region(struct vhost_memory *mem,
872                                                      __u64 addr, __u32 len)
873 {
874         struct vhost_memory_region *reg;
875         int i;
876
877         /* linear search is not brilliant, but we really have on the order of 6
878          * regions in practice */
879         for (i = 0; i < mem->nregions; ++i) {
880                 reg = mem->regions + i;
881                 if (reg->guest_phys_addr <= addr &&
882                     reg->guest_phys_addr + reg->memory_size - 1 >= addr)
883                         return reg;
884         }
885         return NULL;
886 }
887
888 /* TODO: This is really inefficient.  We need something like get_user()
889  * (instruction directly accesses the data, with an exception table entry
890  * returning -EFAULT). See Documentation/x86/exception-tables.txt.
891  */
892 static int set_bit_to_user(int nr, void __user *addr)
893 {
894         unsigned long log = (unsigned long)addr;
895         struct page *page;
896         void *base;
897         int bit = nr + (log % PAGE_SIZE) * 8;
898         int r;
899
900         r = get_user_pages_fast(log, 1, 1, &page);
901         if (r < 0)
902                 return r;
903         BUG_ON(r != 1);
904         base = kmap_atomic(page, KM_USER0);
905         set_bit(bit, base);
906         kunmap_atomic(base, KM_USER0);
907         set_page_dirty_lock(page);
908         put_page(page);
909         return 0;
910 }
911
912 static int log_write(void __user *log_base,
913                      u64 write_address, u64 write_length)
914 {
915         u64 write_page = write_address / VHOST_PAGE_SIZE;
916         int r;
917
918         if (!write_length)
919                 return 0;
920         write_length += write_address % VHOST_PAGE_SIZE;
921         for (;;) {
922                 u64 base = (u64)(unsigned long)log_base;
923                 u64 log = base + write_page / 8;
924                 int bit = write_page % 8;
925                 if ((u64)(unsigned long)log != log)
926                         return -EFAULT;
927                 r = set_bit_to_user(bit, (void __user *)(unsigned long)log);
928                 if (r < 0)
929                         return r;
930                 if (write_length <= VHOST_PAGE_SIZE)
931                         break;
932                 write_length -= VHOST_PAGE_SIZE;
933                 write_page += 1;
934         }
935         return r;
936 }
937
938 int vhost_log_write(struct vhost_virtqueue *vq, struct vhost_log *log,
939                     unsigned int log_num, u64 len)
940 {
941         int i, r;
942
943         /* Make sure data written is seen before log. */
944         smp_wmb();
945         for (i = 0; i < log_num; ++i) {
946                 u64 l = min(log[i].len, len);
947                 r = log_write(vq->log_base, log[i].addr, l);
948                 if (r < 0)
949                         return r;
950                 len -= l;
951                 if (!len) {
952                         if (vq->log_ctx)
953                                 eventfd_signal(vq->log_ctx, 1);
954                         return 0;
955                 }
956         }
957         /* Length written exceeds what we have stored. This is a bug. */
958         BUG();
959         return 0;
960 }
961
962 static int translate_desc(struct vhost_dev *dev, u64 addr, u32 len,
963                           struct iovec iov[], int iov_size)
964 {
965         const struct vhost_memory_region *reg;
966         struct vhost_memory *mem;
967         struct iovec *_iov;
968         u64 s = 0;
969         int ret = 0;
970
971         rcu_read_lock();
972
973         mem = rcu_dereference(dev->memory);
974         while ((u64)len > s) {
975                 u64 size;
976                 if (unlikely(ret >= iov_size)) {
977                         ret = -ENOBUFS;
978                         break;
979                 }
980                 reg = find_region(mem, addr, len);
981                 if (unlikely(!reg)) {
982                         ret = -EFAULT;
983                         break;
984                 }
985                 _iov = iov + ret;
986                 size = reg->memory_size - addr + reg->guest_phys_addr;
987                 _iov->iov_len = min((u64)len, size);
988                 _iov->iov_base = (void __user *)(unsigned long)
989                         (reg->userspace_addr + addr - reg->guest_phys_addr);
990                 s += size;
991                 addr += size;
992                 ++ret;
993         }
994
995         rcu_read_unlock();
996         return ret;
997 }
998
999 /* Each buffer in the virtqueues is actually a chain of descriptors.  This
1000  * function returns the next descriptor in the chain,
1001  * or -1U if we're at the end. */
1002 static unsigned next_desc(struct vring_desc *desc)
1003 {
1004         unsigned int next;
1005
1006         /* If this descriptor says it doesn't chain, we're done. */
1007         if (!(desc->flags & VRING_DESC_F_NEXT))
1008                 return -1U;
1009
1010         /* Check they're not leading us off end of descriptors. */
1011         next = desc->next;
1012         /* Make sure compiler knows to grab that: we don't want it changing! */
1013         /* We will use the result as an index in an array, so most
1014          * architectures only need a compiler barrier here. */
1015         read_barrier_depends();
1016
1017         return next;
1018 }
1019
1020 static int get_indirect(struct vhost_dev *dev, struct vhost_virtqueue *vq,
1021                         struct iovec iov[], unsigned int iov_size,
1022                         unsigned int *out_num, unsigned int *in_num,
1023                         struct vhost_log *log, unsigned int *log_num,
1024                         struct vring_desc *indirect)
1025 {
1026         struct vring_desc desc;
1027         unsigned int i = 0, count, found = 0;
1028         int ret;
1029
1030         /* Sanity check */
1031         if (unlikely(indirect->len % sizeof desc)) {
1032                 vq_err(vq, "Invalid length in indirect descriptor: "
1033                        "len 0x%llx not multiple of 0x%zx\n",
1034                        (unsigned long long)indirect->len,
1035                        sizeof desc);
1036                 return -EINVAL;
1037         }
1038
1039         ret = translate_desc(dev, indirect->addr, indirect->len, vq->indirect,
1040                              UIO_MAXIOV);
1041         if (unlikely(ret < 0)) {
1042                 vq_err(vq, "Translation failure %d in indirect.\n", ret);
1043                 return ret;
1044         }
1045
1046         /* We will use the result as an address to read from, so most
1047          * architectures only need a compiler barrier here. */
1048         read_barrier_depends();
1049
1050         count = indirect->len / sizeof desc;
1051         /* Buffers are chained via a 16 bit next field, so
1052          * we can have at most 2^16 of these. */
1053         if (unlikely(count > USHRT_MAX + 1)) {
1054                 vq_err(vq, "Indirect buffer length too big: %d\n",
1055                        indirect->len);
1056                 return -E2BIG;
1057         }
1058
1059         do {
1060                 unsigned iov_count = *in_num + *out_num;
1061                 if (unlikely(++found > count)) {
1062                         vq_err(vq, "Loop detected: last one at %u "
1063                                "indirect size %u\n",
1064                                i, count);
1065                         return -EINVAL;
1066                 }
1067                 if (unlikely(memcpy_fromiovec((unsigned char *)&desc,
1068                                               vq->indirect, sizeof desc))) {
1069                         vq_err(vq, "Failed indirect descriptor: idx %d, %zx\n",
1070                                i, (size_t)indirect->addr + i * sizeof desc);
1071                         return -EINVAL;
1072                 }
1073                 if (unlikely(desc.flags & VRING_DESC_F_INDIRECT)) {
1074                         vq_err(vq, "Nested indirect descriptor: idx %d, %zx\n",
1075                                i, (size_t)indirect->addr + i * sizeof desc);
1076                         return -EINVAL;
1077                 }
1078
1079                 ret = translate_desc(dev, desc.addr, desc.len, iov + iov_count,
1080                                      iov_size - iov_count);
1081                 if (unlikely(ret < 0)) {
1082                         vq_err(vq, "Translation failure %d indirect idx %d\n",
1083                                ret, i);
1084                         return ret;
1085                 }
1086                 /* If this is an input descriptor, increment that count. */
1087                 if (desc.flags & VRING_DESC_F_WRITE) {
1088                         *in_num += ret;
1089                         if (unlikely(log)) {
1090                                 log[*log_num].addr = desc.addr;
1091                                 log[*log_num].len = desc.len;
1092                                 ++*log_num;
1093                         }
1094                 } else {
1095                         /* If it's an output descriptor, they're all supposed
1096                          * to come before any input descriptors. */
1097                         if (unlikely(*in_num)) {
1098                                 vq_err(vq, "Indirect descriptor "
1099                                        "has out after in: idx %d\n", i);
1100                                 return -EINVAL;
1101                         }
1102                         *out_num += ret;
1103                 }
1104         } while ((i = next_desc(&desc)) != -1);
1105         return 0;
1106 }
1107
1108 /* This looks in the virtqueue and for the first available buffer, and converts
1109  * it to an iovec for convenient access.  Since descriptors consist of some
1110  * number of output then some number of input descriptors, it's actually two
1111  * iovecs, but we pack them into one and note how many of each there were.
1112  *
1113  * This function returns the descriptor number found, or vq->num (which is
1114  * never a valid descriptor number) if none was found.  A negative code is
1115  * returned on error. */
1116 int vhost_get_vq_desc(struct vhost_dev *dev, struct vhost_virtqueue *vq,
1117                       struct iovec iov[], unsigned int iov_size,
1118                       unsigned int *out_num, unsigned int *in_num,
1119                       struct vhost_log *log, unsigned int *log_num)
1120 {
1121         struct vring_desc desc;
1122         unsigned int i, head, found = 0;
1123         u16 last_avail_idx;
1124         int ret;
1125
1126         /* Check it isn't doing very strange things with descriptor numbers. */
1127         last_avail_idx = vq->last_avail_idx;
1128         if (unlikely(__get_user(vq->avail_idx, &vq->avail->idx))) {
1129                 vq_err(vq, "Failed to access avail idx at %p\n",
1130                        &vq->avail->idx);
1131                 return -EFAULT;
1132         }
1133
1134         if (unlikely((u16)(vq->avail_idx - last_avail_idx) > vq->num)) {
1135                 vq_err(vq, "Guest moved used index from %u to %u",
1136                        last_avail_idx, vq->avail_idx);
1137                 return -EFAULT;
1138         }
1139
1140         /* If there's nothing new since last we looked, return invalid. */
1141         if (vq->avail_idx == last_avail_idx)
1142                 return vq->num;
1143
1144         /* Only get avail ring entries after they have been exposed by guest. */
1145         smp_rmb();
1146
1147         /* Grab the next descriptor number they're advertising, and increment
1148          * the index we've seen. */
1149         if (unlikely(__get_user(head,
1150                                 &vq->avail->ring[last_avail_idx % vq->num]))) {
1151                 vq_err(vq, "Failed to read head: idx %d address %p\n",
1152                        last_avail_idx,
1153                        &vq->avail->ring[last_avail_idx % vq->num]);
1154                 return -EFAULT;
1155         }
1156
1157         /* If their number is silly, that's an error. */
1158         if (unlikely(head >= vq->num)) {
1159                 vq_err(vq, "Guest says index %u > %u is available",
1160                        head, vq->num);
1161                 return -EINVAL;
1162         }
1163
1164         /* When we start there are none of either input nor output. */
1165         *out_num = *in_num = 0;
1166         if (unlikely(log))
1167                 *log_num = 0;
1168
1169         i = head;
1170         do {
1171                 unsigned iov_count = *in_num + *out_num;
1172                 if (unlikely(i >= vq->num)) {
1173                         vq_err(vq, "Desc index is %u > %u, head = %u",
1174                                i, vq->num, head);
1175                         return -EINVAL;
1176                 }
1177                 if (unlikely(++found > vq->num)) {
1178                         vq_err(vq, "Loop detected: last one at %u "
1179                                "vq size %u head %u\n",
1180                                i, vq->num, head);
1181                         return -EINVAL;
1182                 }
1183                 ret = __copy_from_user(&desc, vq->desc + i, sizeof desc);
1184                 if (unlikely(ret)) {
1185                         vq_err(vq, "Failed to get descriptor: idx %d addr %p\n",
1186                                i, vq->desc + i);
1187                         return -EFAULT;
1188                 }
1189                 if (desc.flags & VRING_DESC_F_INDIRECT) {
1190                         ret = get_indirect(dev, vq, iov, iov_size,
1191                                            out_num, in_num,
1192                                            log, log_num, &desc);
1193                         if (unlikely(ret < 0)) {
1194                                 vq_err(vq, "Failure detected "
1195                                        "in indirect descriptor at idx %d\n", i);
1196                                 return ret;
1197                         }
1198                         continue;
1199                 }
1200
1201                 ret = translate_desc(dev, desc.addr, desc.len, iov + iov_count,
1202                                      iov_size - iov_count);
1203                 if (unlikely(ret < 0)) {
1204                         vq_err(vq, "Translation failure %d descriptor idx %d\n",
1205                                ret, i);
1206                         return ret;
1207                 }
1208                 if (desc.flags & VRING_DESC_F_WRITE) {
1209                         /* If this is an input descriptor,
1210                          * increment that count. */
1211                         *in_num += ret;
1212                         if (unlikely(log)) {
1213                                 log[*log_num].addr = desc.addr;
1214                                 log[*log_num].len = desc.len;
1215                                 ++*log_num;
1216                         }
1217                 } else {
1218                         /* If it's an output descriptor, they're all supposed
1219                          * to come before any input descriptors. */
1220                         if (unlikely(*in_num)) {
1221                                 vq_err(vq, "Descriptor has out after in: "
1222                                        "idx %d\n", i);
1223                                 return -EINVAL;
1224                         }
1225                         *out_num += ret;
1226                 }
1227         } while ((i = next_desc(&desc)) != -1);
1228
1229         /* On success, increment avail index. */
1230         vq->last_avail_idx++;
1231
1232         /* Assume notifications from guest are disabled at this point,
1233          * if they aren't we would need to update avail_event index. */
1234         BUG_ON(!(vq->used_flags & VRING_USED_F_NO_NOTIFY));
1235         return head;
1236 }
1237
1238 /* Reverse the effect of vhost_get_vq_desc. Useful for error handling. */
1239 void vhost_discard_vq_desc(struct vhost_virtqueue *vq, int n)
1240 {
1241         vq->last_avail_idx -= n;
1242 }
1243
1244 /* After we've used one of their buffers, we tell them about it.  We'll then
1245  * want to notify the guest, using eventfd. */
1246 int vhost_add_used(struct vhost_virtqueue *vq, unsigned int head, int len)
1247 {
1248         struct vring_used_elem __user *used;
1249
1250         /* The virtqueue contains a ring of used buffers.  Get a pointer to the
1251          * next entry in that used ring. */
1252         used = &vq->used->ring[vq->last_used_idx % vq->num];
1253         if (__put_user(head, &used->id)) {
1254                 vq_err(vq, "Failed to write used id");
1255                 return -EFAULT;
1256         }
1257         if (__put_user(len, &used->len)) {
1258                 vq_err(vq, "Failed to write used len");
1259                 return -EFAULT;
1260         }
1261         /* Make sure buffer is written before we update index. */
1262         smp_wmb();
1263         if (__put_user(vq->last_used_idx + 1, &vq->used->idx)) {
1264                 vq_err(vq, "Failed to increment used idx");
1265                 return -EFAULT;
1266         }
1267         if (unlikely(vq->log_used)) {
1268                 /* Make sure data is seen before log. */
1269                 smp_wmb();
1270                 /* Log used ring entry write. */
1271                 log_write(vq->log_base,
1272                           vq->log_addr +
1273                            ((void __user *)used - (void __user *)vq->used),
1274                           sizeof *used);
1275                 /* Log used index update. */
1276                 log_write(vq->log_base,
1277                           vq->log_addr + offsetof(struct vring_used, idx),
1278                           sizeof vq->used->idx);
1279                 if (vq->log_ctx)
1280                         eventfd_signal(vq->log_ctx, 1);
1281         }
1282         vq->last_used_idx++;
1283         /* If the driver never bothers to signal in a very long while,
1284          * used index might wrap around. If that happens, invalidate
1285          * signalled_used index we stored. TODO: make sure driver
1286          * signals at least once in 2^16 and remove this. */
1287         if (unlikely(vq->last_used_idx == vq->signalled_used))
1288                 vq->signalled_used_valid = false;
1289         return 0;
1290 }
1291
1292 static int __vhost_add_used_n(struct vhost_virtqueue *vq,
1293                             struct vring_used_elem *heads,
1294                             unsigned count)
1295 {
1296         struct vring_used_elem __user *used;
1297         u16 old, new;
1298         int start;
1299
1300         start = vq->last_used_idx % vq->num;
1301         used = vq->used->ring + start;
1302         if (__copy_to_user(used, heads, count * sizeof *used)) {
1303                 vq_err(vq, "Failed to write used");
1304                 return -EFAULT;
1305         }
1306         if (unlikely(vq->log_used)) {
1307                 /* Make sure data is seen before log. */
1308                 smp_wmb();
1309                 /* Log used ring entry write. */
1310                 log_write(vq->log_base,
1311                           vq->log_addr +
1312                            ((void __user *)used - (void __user *)vq->used),
1313                           count * sizeof *used);
1314         }
1315         old = vq->last_used_idx;
1316         new = (vq->last_used_idx += count);
1317         /* If the driver never bothers to signal in a very long while,
1318          * used index might wrap around. If that happens, invalidate
1319          * signalled_used index we stored. TODO: make sure driver
1320          * signals at least once in 2^16 and remove this. */
1321         if (unlikely((u16)(new - vq->signalled_used) < (u16)(new - old)))
1322                 vq->signalled_used_valid = false;
1323         return 0;
1324 }
1325
1326 /* After we've used one of their buffers, we tell them about it.  We'll then
1327  * want to notify the guest, using eventfd. */
1328 int vhost_add_used_n(struct vhost_virtqueue *vq, struct vring_used_elem *heads,
1329                      unsigned count)
1330 {
1331         int start, n, r;
1332
1333         start = vq->last_used_idx % vq->num;
1334         n = vq->num - start;
1335         if (n < count) {
1336                 r = __vhost_add_used_n(vq, heads, n);
1337                 if (r < 0)
1338                         return r;
1339                 heads += n;
1340                 count -= n;
1341         }
1342         r = __vhost_add_used_n(vq, heads, count);
1343
1344         /* Make sure buffer is written before we update index. */
1345         smp_wmb();
1346         if (put_user(vq->last_used_idx, &vq->used->idx)) {
1347                 vq_err(vq, "Failed to increment used idx");
1348                 return -EFAULT;
1349         }
1350         if (unlikely(vq->log_used)) {
1351                 /* Log used index update. */
1352                 log_write(vq->log_base,
1353                           vq->log_addr + offsetof(struct vring_used, idx),
1354                           sizeof vq->used->idx);
1355                 if (vq->log_ctx)
1356                         eventfd_signal(vq->log_ctx, 1);
1357         }
1358         return r;
1359 }
1360
1361 static bool vhost_notify(struct vhost_dev *dev, struct vhost_virtqueue *vq)
1362 {
1363         __u16 old, new, event;
1364         bool v;
1365         /* Flush out used index updates. This is paired
1366          * with the barrier that the Guest executes when enabling
1367          * interrupts. */
1368         smp_mb();
1369
1370         if (vhost_has_feature(dev, VIRTIO_F_NOTIFY_ON_EMPTY) &&
1371             unlikely(vq->avail_idx == vq->last_avail_idx))
1372                 return true;
1373
1374         if (!vhost_has_feature(dev, VIRTIO_RING_F_EVENT_IDX)) {
1375                 __u16 flags;
1376                 if (__get_user(flags, &vq->avail->flags)) {
1377                         vq_err(vq, "Failed to get flags");
1378                         return true;
1379                 }
1380                 return !(flags & VRING_AVAIL_F_NO_INTERRUPT);
1381         }
1382         old = vq->signalled_used;
1383         v = vq->signalled_used_valid;
1384         new = vq->signalled_used = vq->last_used_idx;
1385         vq->signalled_used_valid = true;
1386
1387         if (unlikely(!v))
1388                 return true;
1389
1390         if (get_user(event, vhost_used_event(vq))) {
1391                 vq_err(vq, "Failed to get used event idx");
1392                 return true;
1393         }
1394         return vring_need_event(event, new, old);
1395 }
1396
1397 /* This actually signals the guest, using eventfd. */
1398 void vhost_signal(struct vhost_dev *dev, struct vhost_virtqueue *vq)
1399 {
1400         /* Signal the Guest tell them we used something up. */
1401         if (vq->call_ctx && vhost_notify(dev, vq))
1402                 eventfd_signal(vq->call_ctx, 1);
1403 }
1404
1405 /* And here's the combo meal deal.  Supersize me! */
1406 void vhost_add_used_and_signal(struct vhost_dev *dev,
1407                                struct vhost_virtqueue *vq,
1408                                unsigned int head, int len)
1409 {
1410         vhost_add_used(vq, head, len);
1411         vhost_signal(dev, vq);
1412 }
1413
1414 /* multi-buffer version of vhost_add_used_and_signal */
1415 void vhost_add_used_and_signal_n(struct vhost_dev *dev,
1416                                  struct vhost_virtqueue *vq,
1417                                  struct vring_used_elem *heads, unsigned count)
1418 {
1419         vhost_add_used_n(vq, heads, count);
1420         vhost_signal(dev, vq);
1421 }
1422
1423 /* OK, now we need to know about added descriptors. */
1424 bool vhost_enable_notify(struct vhost_dev *dev, struct vhost_virtqueue *vq)
1425 {
1426         u16 avail_idx;
1427         int r;
1428
1429         if (!(vq->used_flags & VRING_USED_F_NO_NOTIFY))
1430                 return false;
1431         vq->used_flags &= ~VRING_USED_F_NO_NOTIFY;
1432         if (!vhost_has_feature(dev, VIRTIO_RING_F_EVENT_IDX)) {
1433                 r = put_user(vq->used_flags, &vq->used->flags);
1434                 if (r) {
1435                         vq_err(vq, "Failed to enable notification at %p: %d\n",
1436                                &vq->used->flags, r);
1437                         return false;
1438                 }
1439         } else {
1440                 r = put_user(vq->avail_idx, vhost_avail_event(vq));
1441                 if (r) {
1442                         vq_err(vq, "Failed to update avail event index at %p: %d\n",
1443                                vhost_avail_event(vq), r);
1444                         return false;
1445                 }
1446         }
1447         if (unlikely(vq->log_used)) {
1448                 void __user *used;
1449                 /* Make sure data is seen before log. */
1450                 smp_wmb();
1451                 used = vhost_has_feature(dev, VIRTIO_RING_F_EVENT_IDX) ?
1452                         &vq->used->flags : vhost_avail_event(vq);
1453                 /* Log used flags or event index entry write. Both are 16 bit
1454                  * fields. */
1455                 log_write(vq->log_base, vq->log_addr +
1456                            (used - (void __user *)vq->used),
1457                           sizeof(u16));
1458                 if (vq->log_ctx)
1459                         eventfd_signal(vq->log_ctx, 1);
1460         }
1461         /* They could have slipped one in as we were doing that: make
1462          * sure it's written, then check again. */
1463         smp_mb();
1464         r = __get_user(avail_idx, &vq->avail->idx);
1465         if (r) {
1466                 vq_err(vq, "Failed to check avail idx at %p: %d\n",
1467                        &vq->avail->idx, r);
1468                 return false;
1469         }
1470
1471         return avail_idx != vq->avail_idx;
1472 }
1473
1474 /* We don't need to be notified again. */
1475 void vhost_disable_notify(struct vhost_dev *dev, struct vhost_virtqueue *vq)
1476 {
1477         int r;
1478
1479         if (vq->used_flags & VRING_USED_F_NO_NOTIFY)
1480                 return;
1481         vq->used_flags |= VRING_USED_F_NO_NOTIFY;
1482         if (!vhost_has_feature(dev, VIRTIO_RING_F_EVENT_IDX)) {
1483                 r = put_user(vq->used_flags, &vq->used->flags);
1484                 if (r)
1485                         vq_err(vq, "Failed to enable notification at %p: %d\n",
1486                                &vq->used->flags, r);
1487         }
1488 }