1 /* Copyright (C) 2009 Red Hat, Inc.
2 * Copyright (C) 2006 Rusty Russell IBM Corporation
4 * Author: Michael S. Tsirkin <mst@redhat.com>
6 * Inspiration, some code, and most witty comments come from
7 * Documentation/virtual/lguest/lguest.c, by Rusty Russell
9 * This work is licensed under the terms of the GNU GPL, version 2.
11 * Generic code for virtio server in host kernel.
14 #include <linux/eventfd.h>
15 #include <linux/vhost.h>
16 #include <linux/socket.h> /* memcpy_fromiovec */
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>
32 VHOST_MEMORY_MAX_NREGIONS = 64,
33 VHOST_MEMORY_F_LOG = 0x1,
36 #define vhost_used_event(vq) ((u16 __user *)&vq->avail->ring[vq->num])
37 #define vhost_avail_event(vq) ((u16 __user *)&vq->used->ring[vq->num])
39 static void vhost_poll_func(struct file *file, wait_queue_head_t *wqh,
42 struct vhost_poll *poll;
44 poll = container_of(pt, struct vhost_poll, table);
46 add_wait_queue(wqh, &poll->wait);
49 static int vhost_poll_wakeup(wait_queue_t *wait, unsigned mode, int sync,
52 struct vhost_poll *poll = container_of(wait, struct vhost_poll, wait);
54 if (!((unsigned long)key & poll->mask))
57 vhost_poll_queue(poll);
61 void vhost_work_init(struct vhost_work *work, vhost_work_fn_t fn)
63 INIT_LIST_HEAD(&work->node);
65 init_waitqueue_head(&work->done);
67 work->queue_seq = work->done_seq = 0;
70 /* Init poll structure */
71 void vhost_poll_init(struct vhost_poll *poll, vhost_work_fn_t fn,
72 unsigned long mask, struct vhost_dev *dev)
74 init_waitqueue_func_entry(&poll->wait, vhost_poll_wakeup);
75 init_poll_funcptr(&poll->table, vhost_poll_func);
80 vhost_work_init(&poll->work, fn);
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 int vhost_poll_start(struct vhost_poll *poll, struct file *file)
93 mask = file->f_op->poll(file, &poll->table);
95 vhost_poll_wakeup(&poll->wait, 0, 0, (void *)mask);
98 remove_wait_queue(poll->wqh, &poll->wait);
105 /* Stop polling a file. After this function returns, it becomes safe to drop the
106 * file reference. You must also flush afterwards. */
107 void vhost_poll_stop(struct vhost_poll *poll)
110 remove_wait_queue(poll->wqh, &poll->wait);
115 static bool vhost_work_seq_done(struct vhost_dev *dev, struct vhost_work *work,
120 spin_lock_irq(&dev->work_lock);
121 left = seq - work->done_seq;
122 spin_unlock_irq(&dev->work_lock);
126 static void vhost_work_flush(struct vhost_dev *dev, struct vhost_work *work)
131 spin_lock_irq(&dev->work_lock);
132 seq = work->queue_seq;
134 spin_unlock_irq(&dev->work_lock);
135 wait_event(work->done, vhost_work_seq_done(dev, work, seq));
136 spin_lock_irq(&dev->work_lock);
137 flushing = --work->flushing;
138 spin_unlock_irq(&dev->work_lock);
139 BUG_ON(flushing < 0);
142 /* Flush any work that has been scheduled. When calling this, don't hold any
143 * locks that are also used by the callback. */
144 void vhost_poll_flush(struct vhost_poll *poll)
146 vhost_work_flush(poll->dev, &poll->work);
149 void vhost_work_queue(struct vhost_dev *dev, struct vhost_work *work)
153 spin_lock_irqsave(&dev->work_lock, flags);
154 if (list_empty(&work->node)) {
155 list_add_tail(&work->node, &dev->work_list);
157 wake_up_process(dev->worker);
159 spin_unlock_irqrestore(&dev->work_lock, flags);
162 void vhost_poll_queue(struct vhost_poll *poll)
164 vhost_work_queue(poll->dev, &poll->work);
167 static void vhost_vq_reset(struct vhost_dev *dev,
168 struct vhost_virtqueue *vq)
174 vq->last_avail_idx = 0;
176 vq->last_used_idx = 0;
177 vq->signalled_used = 0;
178 vq->signalled_used_valid = false;
180 vq->log_used = false;
181 vq->log_addr = -1ull;
182 vq->private_data = NULL;
184 vq->error_ctx = NULL;
192 static int vhost_worker(void *data)
194 struct vhost_dev *dev = data;
195 struct vhost_work *work = NULL;
196 unsigned uninitialized_var(seq);
197 mm_segment_t oldfs = get_fs();
203 /* mb paired w/ kthread_stop */
204 set_current_state(TASK_INTERRUPTIBLE);
206 spin_lock_irq(&dev->work_lock);
208 work->done_seq = seq;
210 wake_up_all(&work->done);
213 if (kthread_should_stop()) {
214 spin_unlock_irq(&dev->work_lock);
215 __set_current_state(TASK_RUNNING);
218 if (!list_empty(&dev->work_list)) {
219 work = list_first_entry(&dev->work_list,
220 struct vhost_work, node);
221 list_del_init(&work->node);
222 seq = work->queue_seq;
225 spin_unlock_irq(&dev->work_lock);
228 __set_current_state(TASK_RUNNING);
241 static void vhost_vq_free_iovecs(struct vhost_virtqueue *vq)
251 /* Helper to allocate iovec buffers for all vqs. */
252 static long vhost_dev_alloc_iovecs(struct vhost_dev *dev)
256 for (i = 0; i < dev->nvqs; ++i) {
257 dev->vqs[i]->indirect = kmalloc(sizeof *dev->vqs[i]->indirect *
258 UIO_MAXIOV, GFP_KERNEL);
259 dev->vqs[i]->log = kmalloc(sizeof *dev->vqs[i]->log * UIO_MAXIOV,
261 dev->vqs[i]->heads = kmalloc(sizeof *dev->vqs[i]->heads *
262 UIO_MAXIOV, GFP_KERNEL);
263 if (!dev->vqs[i]->indirect || !dev->vqs[i]->log ||
271 vhost_vq_free_iovecs(dev->vqs[i]);
275 static void vhost_dev_free_iovecs(struct vhost_dev *dev)
279 for (i = 0; i < dev->nvqs; ++i)
280 vhost_vq_free_iovecs(dev->vqs[i]);
283 long vhost_dev_init(struct vhost_dev *dev,
284 struct vhost_virtqueue **vqs, int nvqs)
290 mutex_init(&dev->mutex);
292 dev->log_file = NULL;
295 spin_lock_init(&dev->work_lock);
296 INIT_LIST_HEAD(&dev->work_list);
299 for (i = 0; i < dev->nvqs; ++i) {
300 dev->vqs[i]->log = NULL;
301 dev->vqs[i]->indirect = NULL;
302 dev->vqs[i]->heads = NULL;
303 dev->vqs[i]->dev = dev;
304 mutex_init(&dev->vqs[i]->mutex);
305 vhost_vq_reset(dev, dev->vqs[i]);
306 if (dev->vqs[i]->handle_kick)
307 vhost_poll_init(&dev->vqs[i]->poll,
308 dev->vqs[i]->handle_kick, POLLIN, dev);
314 /* Caller should have device mutex */
315 long vhost_dev_check_owner(struct vhost_dev *dev)
317 /* Are you the owner? If not, I don't think you mean to do that */
318 return dev->mm == current->mm ? 0 : -EPERM;
321 struct vhost_attach_cgroups_struct {
322 struct vhost_work work;
323 struct task_struct *owner;
327 static void vhost_attach_cgroups_work(struct vhost_work *work)
329 struct vhost_attach_cgroups_struct *s;
331 s = container_of(work, struct vhost_attach_cgroups_struct, work);
332 s->ret = cgroup_attach_task_all(s->owner, current);
335 static int vhost_attach_cgroups(struct vhost_dev *dev)
337 struct vhost_attach_cgroups_struct attach;
339 attach.owner = current;
340 vhost_work_init(&attach.work, vhost_attach_cgroups_work);
341 vhost_work_queue(dev, &attach.work);
342 vhost_work_flush(dev, &attach.work);
346 /* Caller should have device mutex */
347 bool vhost_dev_has_owner(struct vhost_dev *dev)
352 /* Caller should have device mutex */
353 long vhost_dev_set_owner(struct vhost_dev *dev)
355 struct task_struct *worker;
358 /* Is there an owner already? */
359 if (vhost_dev_has_owner(dev)) {
364 /* No owner, become one */
365 dev->mm = get_task_mm(current);
366 worker = kthread_create(vhost_worker, dev, "vhost-%d", current->pid);
367 if (IS_ERR(worker)) {
368 err = PTR_ERR(worker);
372 dev->worker = worker;
373 wake_up_process(worker); /* avoid contributing to loadavg */
375 err = vhost_attach_cgroups(dev);
379 err = vhost_dev_alloc_iovecs(dev);
385 kthread_stop(worker);
395 struct vhost_memory *vhost_dev_reset_owner_prepare(void)
397 return kmalloc(offsetof(struct vhost_memory, regions), GFP_KERNEL);
400 /* Caller should have device mutex */
401 void vhost_dev_reset_owner(struct vhost_dev *dev, struct vhost_memory *memory)
403 vhost_dev_cleanup(dev, true);
405 /* Restore memory to default empty mapping. */
406 memory->nregions = 0;
407 RCU_INIT_POINTER(dev->memory, memory);
410 void vhost_dev_stop(struct vhost_dev *dev)
414 for (i = 0; i < dev->nvqs; ++i) {
415 if (dev->vqs[i]->kick && dev->vqs[i]->handle_kick) {
416 vhost_poll_stop(&dev->vqs[i]->poll);
417 vhost_poll_flush(&dev->vqs[i]->poll);
422 /* Caller should have device mutex if and only if locked is set */
423 void vhost_dev_cleanup(struct vhost_dev *dev, bool locked)
427 for (i = 0; i < dev->nvqs; ++i) {
428 if (dev->vqs[i]->error_ctx)
429 eventfd_ctx_put(dev->vqs[i]->error_ctx);
430 if (dev->vqs[i]->error)
431 fput(dev->vqs[i]->error);
432 if (dev->vqs[i]->kick)
433 fput(dev->vqs[i]->kick);
434 if (dev->vqs[i]->call_ctx)
435 eventfd_ctx_put(dev->vqs[i]->call_ctx);
436 if (dev->vqs[i]->call)
437 fput(dev->vqs[i]->call);
438 vhost_vq_reset(dev, dev->vqs[i]);
440 vhost_dev_free_iovecs(dev);
442 eventfd_ctx_put(dev->log_ctx);
446 dev->log_file = NULL;
447 /* No one will access memory at this point */
448 kfree(rcu_dereference_protected(dev->memory,
450 lockdep_is_held(&dev->mutex)));
451 RCU_INIT_POINTER(dev->memory, NULL);
452 WARN_ON(!list_empty(&dev->work_list));
454 kthread_stop(dev->worker);
462 static int log_access_ok(void __user *log_base, u64 addr, unsigned long sz)
464 u64 a = addr / VHOST_PAGE_SIZE / 8;
466 /* Make sure 64 bit math will not overflow. */
467 if (a > ULONG_MAX - (unsigned long)log_base ||
468 a + (unsigned long)log_base > ULONG_MAX)
471 return access_ok(VERIFY_WRITE, log_base + a,
472 (sz + VHOST_PAGE_SIZE * 8 - 1) / VHOST_PAGE_SIZE / 8);
475 /* Caller should have vq mutex and device mutex. */
476 static int vq_memory_access_ok(void __user *log_base, struct vhost_memory *mem,
484 for (i = 0; i < mem->nregions; ++i) {
485 struct vhost_memory_region *m = mem->regions + i;
486 unsigned long a = m->userspace_addr;
487 if (m->memory_size > ULONG_MAX)
489 else if (!access_ok(VERIFY_WRITE, (void __user *)a,
492 else if (log_all && !log_access_ok(log_base,
500 /* Can we switch to this memory table? */
501 /* Caller should have device mutex but not vq mutex */
502 static int memory_access_ok(struct vhost_dev *d, struct vhost_memory *mem,
507 for (i = 0; i < d->nvqs; ++i) {
509 mutex_lock(&d->vqs[i]->mutex);
510 /* If ring is inactive, will check when it's enabled. */
511 if (d->vqs[i]->private_data)
512 ok = vq_memory_access_ok(d->vqs[i]->log_base, mem,
516 mutex_unlock(&d->vqs[i]->mutex);
523 static int vq_access_ok(struct vhost_dev *d, unsigned int num,
524 struct vring_desc __user *desc,
525 struct vring_avail __user *avail,
526 struct vring_used __user *used)
528 size_t s = vhost_has_feature(d, VIRTIO_RING_F_EVENT_IDX) ? 2 : 0;
529 return access_ok(VERIFY_READ, desc, num * sizeof *desc) &&
530 access_ok(VERIFY_READ, avail,
531 sizeof *avail + num * sizeof *avail->ring + s) &&
532 access_ok(VERIFY_WRITE, used,
533 sizeof *used + num * sizeof *used->ring + s);
536 /* Can we log writes? */
537 /* Caller should have device mutex but not vq mutex */
538 int vhost_log_access_ok(struct vhost_dev *dev)
540 struct vhost_memory *mp;
542 mp = rcu_dereference_protected(dev->memory,
543 lockdep_is_held(&dev->mutex));
544 return memory_access_ok(dev, mp, 1);
547 /* Verify access for write logging. */
548 /* Caller should have vq mutex and device mutex */
549 static int vq_log_access_ok(struct vhost_dev *d, struct vhost_virtqueue *vq,
550 void __user *log_base)
552 struct vhost_memory *mp;
553 size_t s = vhost_has_feature(d, VIRTIO_RING_F_EVENT_IDX) ? 2 : 0;
555 mp = rcu_dereference_protected(vq->dev->memory,
556 lockdep_is_held(&vq->mutex));
557 return vq_memory_access_ok(log_base, mp,
558 vhost_has_feature(vq->dev, VHOST_F_LOG_ALL)) &&
559 (!vq->log_used || log_access_ok(log_base, vq->log_addr,
561 vq->num * sizeof *vq->used->ring + s));
564 /* Can we start vq? */
565 /* Caller should have vq mutex and device mutex */
566 int vhost_vq_access_ok(struct vhost_virtqueue *vq)
568 return vq_access_ok(vq->dev, vq->num, vq->desc, vq->avail, vq->used) &&
569 vq_log_access_ok(vq->dev, vq, vq->log_base);
572 static long vhost_set_memory(struct vhost_dev *d, struct vhost_memory __user *m)
574 struct vhost_memory mem, *newmem, *oldmem;
575 unsigned long size = offsetof(struct vhost_memory, regions);
577 if (copy_from_user(&mem, m, size))
581 if (mem.nregions > VHOST_MEMORY_MAX_NREGIONS)
583 newmem = kmalloc(size + mem.nregions * sizeof *m->regions, GFP_KERNEL);
587 memcpy(newmem, &mem, size);
588 if (copy_from_user(newmem->regions, m->regions,
589 mem.nregions * sizeof *m->regions)) {
594 if (!memory_access_ok(d, newmem,
595 vhost_has_feature(d, VHOST_F_LOG_ALL))) {
599 oldmem = rcu_dereference_protected(d->memory,
600 lockdep_is_held(&d->mutex));
601 rcu_assign_pointer(d->memory, newmem);
607 long vhost_vring_ioctl(struct vhost_dev *d, int ioctl, void __user *argp)
609 struct file *eventfp, *filep = NULL;
610 bool pollstart = false, pollstop = false;
611 struct eventfd_ctx *ctx = NULL;
612 u32 __user *idxp = argp;
613 struct vhost_virtqueue *vq;
614 struct vhost_vring_state s;
615 struct vhost_vring_file f;
616 struct vhost_vring_addr a;
620 r = get_user(idx, idxp);
628 mutex_lock(&vq->mutex);
631 case VHOST_SET_VRING_NUM:
632 /* Resizing ring with an active backend?
633 * You don't want to do that. */
634 if (vq->private_data) {
638 if (copy_from_user(&s, argp, sizeof s)) {
642 if (!s.num || s.num > 0xffff || (s.num & (s.num - 1))) {
648 case VHOST_SET_VRING_BASE:
649 /* Moving base with an active backend?
650 * You don't want to do that. */
651 if (vq->private_data) {
655 if (copy_from_user(&s, argp, sizeof s)) {
659 if (s.num > 0xffff) {
663 vq->last_avail_idx = s.num;
664 /* Forget the cached index value. */
665 vq->avail_idx = vq->last_avail_idx;
667 case VHOST_GET_VRING_BASE:
669 s.num = vq->last_avail_idx;
670 if (copy_to_user(argp, &s, sizeof s))
673 case VHOST_SET_VRING_ADDR:
674 if (copy_from_user(&a, argp, sizeof a)) {
678 if (a.flags & ~(0x1 << VHOST_VRING_F_LOG)) {
682 /* For 32bit, verify that the top 32bits of the user
683 data are set to zero. */
684 if ((u64)(unsigned long)a.desc_user_addr != a.desc_user_addr ||
685 (u64)(unsigned long)a.used_user_addr != a.used_user_addr ||
686 (u64)(unsigned long)a.avail_user_addr != a.avail_user_addr) {
690 if ((a.avail_user_addr & (sizeof *vq->avail->ring - 1)) ||
691 (a.used_user_addr & (sizeof *vq->used->ring - 1)) ||
692 (a.log_guest_addr & (sizeof *vq->used->ring - 1))) {
697 /* We only verify access here if backend is configured.
698 * If it is not, we don't as size might not have been setup.
699 * We will verify when backend is configured. */
700 if (vq->private_data) {
701 if (!vq_access_ok(d, vq->num,
702 (void __user *)(unsigned long)a.desc_user_addr,
703 (void __user *)(unsigned long)a.avail_user_addr,
704 (void __user *)(unsigned long)a.used_user_addr)) {
709 /* Also validate log access for used ring if enabled. */
710 if ((a.flags & (0x1 << VHOST_VRING_F_LOG)) &&
711 !log_access_ok(vq->log_base, a.log_guest_addr,
713 vq->num * sizeof *vq->used->ring)) {
719 vq->log_used = !!(a.flags & (0x1 << VHOST_VRING_F_LOG));
720 vq->desc = (void __user *)(unsigned long)a.desc_user_addr;
721 vq->avail = (void __user *)(unsigned long)a.avail_user_addr;
722 vq->log_addr = a.log_guest_addr;
723 vq->used = (void __user *)(unsigned long)a.used_user_addr;
725 case VHOST_SET_VRING_KICK:
726 if (copy_from_user(&f, argp, sizeof f)) {
730 eventfp = f.fd == -1 ? NULL : eventfd_fget(f.fd);
731 if (IS_ERR(eventfp)) {
732 r = PTR_ERR(eventfp);
735 if (eventfp != vq->kick) {
736 pollstop = (filep = vq->kick) != NULL;
737 pollstart = (vq->kick = eventfp) != NULL;
741 case VHOST_SET_VRING_CALL:
742 if (copy_from_user(&f, argp, sizeof f)) {
746 eventfp = f.fd == -1 ? NULL : eventfd_fget(f.fd);
747 if (IS_ERR(eventfp)) {
748 r = PTR_ERR(eventfp);
751 if (eventfp != vq->call) {
755 vq->call_ctx = eventfp ?
756 eventfd_ctx_fileget(eventfp) : NULL;
760 case VHOST_SET_VRING_ERR:
761 if (copy_from_user(&f, argp, sizeof f)) {
765 eventfp = f.fd == -1 ? NULL : eventfd_fget(f.fd);
766 if (IS_ERR(eventfp)) {
767 r = PTR_ERR(eventfp);
770 if (eventfp != vq->error) {
774 vq->error_ctx = eventfp ?
775 eventfd_ctx_fileget(eventfp) : NULL;
783 if (pollstop && vq->handle_kick)
784 vhost_poll_stop(&vq->poll);
787 eventfd_ctx_put(ctx);
791 if (pollstart && vq->handle_kick)
792 r = vhost_poll_start(&vq->poll, vq->kick);
794 mutex_unlock(&vq->mutex);
796 if (pollstop && vq->handle_kick)
797 vhost_poll_flush(&vq->poll);
801 /* Caller must have device mutex */
802 long vhost_dev_ioctl(struct vhost_dev *d, unsigned int ioctl, void __user *argp)
804 struct file *eventfp, *filep = NULL;
805 struct eventfd_ctx *ctx = NULL;
810 /* If you are not the owner, you can become one */
811 if (ioctl == VHOST_SET_OWNER) {
812 r = vhost_dev_set_owner(d);
816 /* You must be the owner to do anything else */
817 r = vhost_dev_check_owner(d);
822 case VHOST_SET_MEM_TABLE:
823 r = vhost_set_memory(d, argp);
825 case VHOST_SET_LOG_BASE:
826 if (copy_from_user(&p, argp, sizeof p)) {
830 if ((u64)(unsigned long)p != p) {
834 for (i = 0; i < d->nvqs; ++i) {
835 struct vhost_virtqueue *vq;
836 void __user *base = (void __user *)(unsigned long)p;
838 mutex_lock(&vq->mutex);
839 /* If ring is inactive, will check when it's enabled. */
840 if (vq->private_data && !vq_log_access_ok(d, vq, base))
844 mutex_unlock(&vq->mutex);
847 case VHOST_SET_LOG_FD:
848 r = get_user(fd, (int __user *)argp);
851 eventfp = fd == -1 ? NULL : eventfd_fget(fd);
852 if (IS_ERR(eventfp)) {
853 r = PTR_ERR(eventfp);
856 if (eventfp != d->log_file) {
859 d->log_ctx = eventfp ?
860 eventfd_ctx_fileget(eventfp) : NULL;
863 for (i = 0; i < d->nvqs; ++i) {
864 mutex_lock(&d->vqs[i]->mutex);
865 d->vqs[i]->log_ctx = d->log_ctx;
866 mutex_unlock(&d->vqs[i]->mutex);
869 eventfd_ctx_put(ctx);
881 static const struct vhost_memory_region *find_region(struct vhost_memory *mem,
882 __u64 addr, __u32 len)
884 struct vhost_memory_region *reg;
887 /* linear search is not brilliant, but we really have on the order of 6
888 * regions in practice */
889 for (i = 0; i < mem->nregions; ++i) {
890 reg = mem->regions + i;
891 if (reg->guest_phys_addr <= addr &&
892 reg->guest_phys_addr + reg->memory_size - 1 >= addr)
898 /* TODO: This is really inefficient. We need something like get_user()
899 * (instruction directly accesses the data, with an exception table entry
900 * returning -EFAULT). See Documentation/x86/exception-tables.txt.
902 static int set_bit_to_user(int nr, void __user *addr)
904 unsigned long log = (unsigned long)addr;
907 int bit = nr + (log % PAGE_SIZE) * 8;
910 r = get_user_pages_fast(log, 1, 1, &page);
914 base = kmap_atomic(page);
917 set_page_dirty_lock(page);
922 static int log_write(void __user *log_base,
923 u64 write_address, u64 write_length)
925 u64 write_page = write_address / VHOST_PAGE_SIZE;
930 write_length += write_address % VHOST_PAGE_SIZE;
932 u64 base = (u64)(unsigned long)log_base;
933 u64 log = base + write_page / 8;
934 int bit = write_page % 8;
935 if ((u64)(unsigned long)log != log)
937 r = set_bit_to_user(bit, (void __user *)(unsigned long)log);
940 if (write_length <= VHOST_PAGE_SIZE)
942 write_length -= VHOST_PAGE_SIZE;
948 int vhost_log_write(struct vhost_virtqueue *vq, struct vhost_log *log,
949 unsigned int log_num, u64 len)
953 /* Make sure data written is seen before log. */
955 for (i = 0; i < log_num; ++i) {
956 u64 l = min(log[i].len, len);
957 r = log_write(vq->log_base, log[i].addr, l);
963 eventfd_signal(vq->log_ctx, 1);
967 /* Length written exceeds what we have stored. This is a bug. */
972 static int vhost_update_used_flags(struct vhost_virtqueue *vq)
975 if (__put_user(vq->used_flags, &vq->used->flags) < 0)
977 if (unlikely(vq->log_used)) {
978 /* Make sure the flag is seen before log. */
980 /* Log used flag write. */
981 used = &vq->used->flags;
982 log_write(vq->log_base, vq->log_addr +
983 (used - (void __user *)vq->used),
984 sizeof vq->used->flags);
986 eventfd_signal(vq->log_ctx, 1);
991 static int vhost_update_avail_event(struct vhost_virtqueue *vq, u16 avail_event)
993 if (__put_user(vq->avail_idx, vhost_avail_event(vq)))
995 if (unlikely(vq->log_used)) {
997 /* Make sure the event is seen before log. */
999 /* Log avail event write */
1000 used = vhost_avail_event(vq);
1001 log_write(vq->log_base, vq->log_addr +
1002 (used - (void __user *)vq->used),
1003 sizeof *vhost_avail_event(vq));
1005 eventfd_signal(vq->log_ctx, 1);
1010 int vhost_init_used(struct vhost_virtqueue *vq)
1013 if (!vq->private_data)
1016 r = vhost_update_used_flags(vq);
1019 vq->signalled_used_valid = false;
1020 return get_user(vq->last_used_idx, &vq->used->idx);
1023 static int translate_desc(struct vhost_dev *dev, u64 addr, u32 len,
1024 struct iovec iov[], int iov_size)
1026 const struct vhost_memory_region *reg;
1027 struct vhost_memory *mem;
1034 mem = rcu_dereference(dev->memory);
1035 while ((u64)len > s) {
1037 if (unlikely(ret >= iov_size)) {
1041 reg = find_region(mem, addr, len);
1042 if (unlikely(!reg)) {
1047 size = reg->memory_size - addr + reg->guest_phys_addr;
1048 _iov->iov_len = min((u64)len - s, size);
1049 _iov->iov_base = (void __user *)(unsigned long)
1050 (reg->userspace_addr + addr - reg->guest_phys_addr);
1060 /* Each buffer in the virtqueues is actually a chain of descriptors. This
1061 * function returns the next descriptor in the chain,
1062 * or -1U if we're at the end. */
1063 static unsigned next_desc(struct vring_desc *desc)
1067 /* If this descriptor says it doesn't chain, we're done. */
1068 if (!(desc->flags & VRING_DESC_F_NEXT))
1071 /* Check they're not leading us off end of descriptors. */
1073 /* Make sure compiler knows to grab that: we don't want it changing! */
1074 /* We will use the result as an index in an array, so most
1075 * architectures only need a compiler barrier here. */
1076 read_barrier_depends();
1081 static int get_indirect(struct vhost_dev *dev, struct vhost_virtqueue *vq,
1082 struct iovec iov[], unsigned int iov_size,
1083 unsigned int *out_num, unsigned int *in_num,
1084 struct vhost_log *log, unsigned int *log_num,
1085 struct vring_desc *indirect)
1087 struct vring_desc desc;
1088 unsigned int i = 0, count, found = 0;
1092 if (unlikely(indirect->len % sizeof desc)) {
1093 vq_err(vq, "Invalid length in indirect descriptor: "
1094 "len 0x%llx not multiple of 0x%zx\n",
1095 (unsigned long long)indirect->len,
1100 ret = translate_desc(dev, indirect->addr, indirect->len, vq->indirect,
1102 if (unlikely(ret < 0)) {
1103 vq_err(vq, "Translation failure %d in indirect.\n", ret);
1107 /* We will use the result as an address to read from, so most
1108 * architectures only need a compiler barrier here. */
1109 read_barrier_depends();
1111 count = indirect->len / sizeof desc;
1112 /* Buffers are chained via a 16 bit next field, so
1113 * we can have at most 2^16 of these. */
1114 if (unlikely(count > USHRT_MAX + 1)) {
1115 vq_err(vq, "Indirect buffer length too big: %d\n",
1121 unsigned iov_count = *in_num + *out_num;
1122 if (unlikely(++found > count)) {
1123 vq_err(vq, "Loop detected: last one at %u "
1124 "indirect size %u\n",
1128 if (unlikely(memcpy_fromiovec((unsigned char *)&desc,
1129 vq->indirect, sizeof desc))) {
1130 vq_err(vq, "Failed indirect descriptor: idx %d, %zx\n",
1131 i, (size_t)indirect->addr + i * sizeof desc);
1134 if (unlikely(desc.flags & VRING_DESC_F_INDIRECT)) {
1135 vq_err(vq, "Nested indirect descriptor: idx %d, %zx\n",
1136 i, (size_t)indirect->addr + i * sizeof desc);
1140 ret = translate_desc(dev, desc.addr, desc.len, iov + iov_count,
1141 iov_size - iov_count);
1142 if (unlikely(ret < 0)) {
1143 vq_err(vq, "Translation failure %d indirect idx %d\n",
1147 /* If this is an input descriptor, increment that count. */
1148 if (desc.flags & VRING_DESC_F_WRITE) {
1150 if (unlikely(log)) {
1151 log[*log_num].addr = desc.addr;
1152 log[*log_num].len = desc.len;
1156 /* If it's an output descriptor, they're all supposed
1157 * to come before any input descriptors. */
1158 if (unlikely(*in_num)) {
1159 vq_err(vq, "Indirect descriptor "
1160 "has out after in: idx %d\n", i);
1165 } while ((i = next_desc(&desc)) != -1);
1169 /* This looks in the virtqueue and for the first available buffer, and converts
1170 * it to an iovec for convenient access. Since descriptors consist of some
1171 * number of output then some number of input descriptors, it's actually two
1172 * iovecs, but we pack them into one and note how many of each there were.
1174 * This function returns the descriptor number found, or vq->num (which is
1175 * never a valid descriptor number) if none was found. A negative code is
1176 * returned on error. */
1177 int vhost_get_vq_desc(struct vhost_dev *dev, struct vhost_virtqueue *vq,
1178 struct iovec iov[], unsigned int iov_size,
1179 unsigned int *out_num, unsigned int *in_num,
1180 struct vhost_log *log, unsigned int *log_num)
1182 struct vring_desc desc;
1183 unsigned int i, head, found = 0;
1187 /* Check it isn't doing very strange things with descriptor numbers. */
1188 last_avail_idx = vq->last_avail_idx;
1189 if (unlikely(__get_user(vq->avail_idx, &vq->avail->idx))) {
1190 vq_err(vq, "Failed to access avail idx at %p\n",
1195 if (unlikely((u16)(vq->avail_idx - last_avail_idx) > vq->num)) {
1196 vq_err(vq, "Guest moved used index from %u to %u",
1197 last_avail_idx, vq->avail_idx);
1201 /* If there's nothing new since last we looked, return invalid. */
1202 if (vq->avail_idx == last_avail_idx)
1205 /* Only get avail ring entries after they have been exposed by guest. */
1208 /* Grab the next descriptor number they're advertising, and increment
1209 * the index we've seen. */
1210 if (unlikely(__get_user(head,
1211 &vq->avail->ring[last_avail_idx % vq->num]))) {
1212 vq_err(vq, "Failed to read head: idx %d address %p\n",
1214 &vq->avail->ring[last_avail_idx % vq->num]);
1218 /* If their number is silly, that's an error. */
1219 if (unlikely(head >= vq->num)) {
1220 vq_err(vq, "Guest says index %u > %u is available",
1225 /* When we start there are none of either input nor output. */
1226 *out_num = *in_num = 0;
1232 unsigned iov_count = *in_num + *out_num;
1233 if (unlikely(i >= vq->num)) {
1234 vq_err(vq, "Desc index is %u > %u, head = %u",
1238 if (unlikely(++found > vq->num)) {
1239 vq_err(vq, "Loop detected: last one at %u "
1240 "vq size %u head %u\n",
1244 ret = __copy_from_user(&desc, vq->desc + i, sizeof desc);
1245 if (unlikely(ret)) {
1246 vq_err(vq, "Failed to get descriptor: idx %d addr %p\n",
1250 if (desc.flags & VRING_DESC_F_INDIRECT) {
1251 ret = get_indirect(dev, vq, iov, iov_size,
1253 log, log_num, &desc);
1254 if (unlikely(ret < 0)) {
1255 vq_err(vq, "Failure detected "
1256 "in indirect descriptor at idx %d\n", i);
1262 ret = translate_desc(dev, desc.addr, desc.len, iov + iov_count,
1263 iov_size - iov_count);
1264 if (unlikely(ret < 0)) {
1265 vq_err(vq, "Translation failure %d descriptor idx %d\n",
1269 if (desc.flags & VRING_DESC_F_WRITE) {
1270 /* If this is an input descriptor,
1271 * increment that count. */
1273 if (unlikely(log)) {
1274 log[*log_num].addr = desc.addr;
1275 log[*log_num].len = desc.len;
1279 /* If it's an output descriptor, they're all supposed
1280 * to come before any input descriptors. */
1281 if (unlikely(*in_num)) {
1282 vq_err(vq, "Descriptor has out after in: "
1288 } while ((i = next_desc(&desc)) != -1);
1290 /* On success, increment avail index. */
1291 vq->last_avail_idx++;
1293 /* Assume notifications from guest are disabled at this point,
1294 * if they aren't we would need to update avail_event index. */
1295 BUG_ON(!(vq->used_flags & VRING_USED_F_NO_NOTIFY));
1299 /* Reverse the effect of vhost_get_vq_desc. Useful for error handling. */
1300 void vhost_discard_vq_desc(struct vhost_virtqueue *vq, int n)
1302 vq->last_avail_idx -= n;
1305 /* After we've used one of their buffers, we tell them about it. We'll then
1306 * want to notify the guest, using eventfd. */
1307 int vhost_add_used(struct vhost_virtqueue *vq, unsigned int head, int len)
1309 struct vring_used_elem __user *used;
1311 /* The virtqueue contains a ring of used buffers. Get a pointer to the
1312 * next entry in that used ring. */
1313 used = &vq->used->ring[vq->last_used_idx % vq->num];
1314 if (__put_user(head, &used->id)) {
1315 vq_err(vq, "Failed to write used id");
1318 if (__put_user(len, &used->len)) {
1319 vq_err(vq, "Failed to write used len");
1322 /* Make sure buffer is written before we update index. */
1324 if (__put_user(vq->last_used_idx + 1, &vq->used->idx)) {
1325 vq_err(vq, "Failed to increment used idx");
1328 if (unlikely(vq->log_used)) {
1329 /* Make sure data is seen before log. */
1331 /* Log used ring entry write. */
1332 log_write(vq->log_base,
1334 ((void __user *)used - (void __user *)vq->used),
1336 /* Log used index update. */
1337 log_write(vq->log_base,
1338 vq->log_addr + offsetof(struct vring_used, idx),
1339 sizeof vq->used->idx);
1341 eventfd_signal(vq->log_ctx, 1);
1343 vq->last_used_idx++;
1344 /* If the driver never bothers to signal in a very long while,
1345 * used index might wrap around. If that happens, invalidate
1346 * signalled_used index we stored. TODO: make sure driver
1347 * signals at least once in 2^16 and remove this. */
1348 if (unlikely(vq->last_used_idx == vq->signalled_used))
1349 vq->signalled_used_valid = false;
1353 static int __vhost_add_used_n(struct vhost_virtqueue *vq,
1354 struct vring_used_elem *heads,
1357 struct vring_used_elem __user *used;
1361 start = vq->last_used_idx % vq->num;
1362 used = vq->used->ring + start;
1363 if (__copy_to_user(used, heads, count * sizeof *used)) {
1364 vq_err(vq, "Failed to write used");
1367 if (unlikely(vq->log_used)) {
1368 /* Make sure data is seen before log. */
1370 /* Log used ring entry write. */
1371 log_write(vq->log_base,
1373 ((void __user *)used - (void __user *)vq->used),
1374 count * sizeof *used);
1376 old = vq->last_used_idx;
1377 new = (vq->last_used_idx += count);
1378 /* If the driver never bothers to signal in a very long while,
1379 * used index might wrap around. If that happens, invalidate
1380 * signalled_used index we stored. TODO: make sure driver
1381 * signals at least once in 2^16 and remove this. */
1382 if (unlikely((u16)(new - vq->signalled_used) < (u16)(new - old)))
1383 vq->signalled_used_valid = false;
1387 /* After we've used one of their buffers, we tell them about it. We'll then
1388 * want to notify the guest, using eventfd. */
1389 int vhost_add_used_n(struct vhost_virtqueue *vq, struct vring_used_elem *heads,
1394 start = vq->last_used_idx % vq->num;
1395 n = vq->num - start;
1397 r = __vhost_add_used_n(vq, heads, n);
1403 r = __vhost_add_used_n(vq, heads, count);
1405 /* Make sure buffer is written before we update index. */
1407 if (put_user(vq->last_used_idx, &vq->used->idx)) {
1408 vq_err(vq, "Failed to increment used idx");
1411 if (unlikely(vq->log_used)) {
1412 /* Log used index update. */
1413 log_write(vq->log_base,
1414 vq->log_addr + offsetof(struct vring_used, idx),
1415 sizeof vq->used->idx);
1417 eventfd_signal(vq->log_ctx, 1);
1422 static bool vhost_notify(struct vhost_dev *dev, struct vhost_virtqueue *vq)
1424 __u16 old, new, event;
1426 /* Flush out used index updates. This is paired
1427 * with the barrier that the Guest executes when enabling
1431 if (vhost_has_feature(dev, VIRTIO_F_NOTIFY_ON_EMPTY) &&
1432 unlikely(vq->avail_idx == vq->last_avail_idx))
1435 if (!vhost_has_feature(dev, VIRTIO_RING_F_EVENT_IDX)) {
1437 if (__get_user(flags, &vq->avail->flags)) {
1438 vq_err(vq, "Failed to get flags");
1441 return !(flags & VRING_AVAIL_F_NO_INTERRUPT);
1443 old = vq->signalled_used;
1444 v = vq->signalled_used_valid;
1445 new = vq->signalled_used = vq->last_used_idx;
1446 vq->signalled_used_valid = true;
1451 if (get_user(event, vhost_used_event(vq))) {
1452 vq_err(vq, "Failed to get used event idx");
1455 return vring_need_event(event, new, old);
1458 /* This actually signals the guest, using eventfd. */
1459 void vhost_signal(struct vhost_dev *dev, struct vhost_virtqueue *vq)
1461 /* Signal the Guest tell them we used something up. */
1462 if (vq->call_ctx && vhost_notify(dev, vq))
1463 eventfd_signal(vq->call_ctx, 1);
1466 /* And here's the combo meal deal. Supersize me! */
1467 void vhost_add_used_and_signal(struct vhost_dev *dev,
1468 struct vhost_virtqueue *vq,
1469 unsigned int head, int len)
1471 vhost_add_used(vq, head, len);
1472 vhost_signal(dev, vq);
1475 /* multi-buffer version of vhost_add_used_and_signal */
1476 void vhost_add_used_and_signal_n(struct vhost_dev *dev,
1477 struct vhost_virtqueue *vq,
1478 struct vring_used_elem *heads, unsigned count)
1480 vhost_add_used_n(vq, heads, count);
1481 vhost_signal(dev, vq);
1484 /* OK, now we need to know about added descriptors. */
1485 bool vhost_enable_notify(struct vhost_dev *dev, struct vhost_virtqueue *vq)
1490 if (!(vq->used_flags & VRING_USED_F_NO_NOTIFY))
1492 vq->used_flags &= ~VRING_USED_F_NO_NOTIFY;
1493 if (!vhost_has_feature(dev, VIRTIO_RING_F_EVENT_IDX)) {
1494 r = vhost_update_used_flags(vq);
1496 vq_err(vq, "Failed to enable notification at %p: %d\n",
1497 &vq->used->flags, r);
1501 r = vhost_update_avail_event(vq, vq->avail_idx);
1503 vq_err(vq, "Failed to update avail event index at %p: %d\n",
1504 vhost_avail_event(vq), r);
1508 /* They could have slipped one in as we were doing that: make
1509 * sure it's written, then check again. */
1511 r = __get_user(avail_idx, &vq->avail->idx);
1513 vq_err(vq, "Failed to check avail idx at %p: %d\n",
1514 &vq->avail->idx, r);
1518 return avail_idx != vq->avail_idx;
1521 /* We don't need to be notified again. */
1522 void vhost_disable_notify(struct vhost_dev *dev, struct vhost_virtqueue *vq)
1526 if (vq->used_flags & VRING_USED_F_NO_NOTIFY)
1528 vq->used_flags |= VRING_USED_F_NO_NOTIFY;
1529 if (!vhost_has_feature(dev, VIRTIO_RING_F_EVENT_IDX)) {
1530 r = vhost_update_used_flags(vq);
1532 vq_err(vq, "Failed to enable notification at %p: %d\n",
1533 &vq->used->flags, r);