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/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/virtio_net.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>
29 #include <linux/net.h>
30 #include <linux/if_packet.h>
31 #include <linux/if_arp.h>
36 VHOST_MEMORY_MAX_NREGIONS = 64,
37 VHOST_MEMORY_F_LOG = 0x1,
40 static void vhost_poll_func(struct file *file, wait_queue_head_t *wqh,
43 struct vhost_poll *poll;
44 poll = container_of(pt, struct vhost_poll, table);
47 add_wait_queue(wqh, &poll->wait);
50 static int vhost_poll_wakeup(wait_queue_t *wait, unsigned mode, int sync,
53 struct vhost_poll *poll = container_of(wait, struct vhost_poll, wait);
55 if (!((unsigned long)key & poll->mask))
58 vhost_poll_queue(poll);
62 static void vhost_work_init(struct vhost_work *work, vhost_work_fn_t fn)
64 INIT_LIST_HEAD(&work->node);
66 init_waitqueue_head(&work->done);
68 work->queue_seq = work->done_seq = 0;
71 /* Init poll structure */
72 void vhost_poll_init(struct vhost_poll *poll, vhost_work_fn_t fn,
73 unsigned long mask, struct vhost_dev *dev)
75 init_waitqueue_func_entry(&poll->wait, vhost_poll_wakeup);
76 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 void vhost_poll_start(struct vhost_poll *poll, struct file *file)
88 mask = file->f_op->poll(file, &poll->table);
90 vhost_poll_wakeup(&poll->wait, 0, 0, (void *)mask);
93 /* Stop polling a file. After this function returns, it becomes safe to drop the
94 * file reference. You must also flush afterwards. */
95 void vhost_poll_stop(struct vhost_poll *poll)
97 remove_wait_queue(poll->wqh, &poll->wait);
100 static void vhost_work_flush(struct vhost_dev *dev, struct vhost_work *work)
106 spin_lock_irq(&dev->work_lock);
107 seq = work->queue_seq;
109 spin_unlock_irq(&dev->work_lock);
110 wait_event(work->done, ({
111 spin_lock_irq(&dev->work_lock);
112 left = seq - work->done_seq <= 0;
113 spin_unlock_irq(&dev->work_lock);
116 spin_lock_irq(&dev->work_lock);
117 flushing = --work->flushing;
118 spin_unlock_irq(&dev->work_lock);
119 BUG_ON(flushing < 0);
122 /* Flush any work that has been scheduled. When calling this, don't hold any
123 * locks that are also used by the callback. */
124 void vhost_poll_flush(struct vhost_poll *poll)
126 vhost_work_flush(poll->dev, &poll->work);
129 static inline void vhost_work_queue(struct vhost_dev *dev,
130 struct vhost_work *work)
134 spin_lock_irqsave(&dev->work_lock, flags);
135 if (list_empty(&work->node)) {
136 list_add_tail(&work->node, &dev->work_list);
138 wake_up_process(dev->worker);
140 spin_unlock_irqrestore(&dev->work_lock, flags);
143 void vhost_poll_queue(struct vhost_poll *poll)
145 vhost_work_queue(poll->dev, &poll->work);
148 static void vhost_vq_reset(struct vhost_dev *dev,
149 struct vhost_virtqueue *vq)
155 vq->last_avail_idx = 0;
157 vq->last_used_idx = 0;
159 vq->log_used = false;
160 vq->log_addr = -1ull;
163 vq->private_data = NULL;
165 vq->error_ctx = NULL;
173 static int vhost_worker(void *data)
175 struct vhost_dev *dev = data;
176 struct vhost_work *work = NULL;
177 unsigned uninitialized_var(seq);
182 /* mb paired w/ kthread_stop */
183 set_current_state(TASK_INTERRUPTIBLE);
185 spin_lock_irq(&dev->work_lock);
187 work->done_seq = seq;
189 wake_up_all(&work->done);
192 if (kthread_should_stop()) {
193 spin_unlock_irq(&dev->work_lock);
194 __set_current_state(TASK_RUNNING);
197 if (!list_empty(&dev->work_list)) {
198 work = list_first_entry(&dev->work_list,
199 struct vhost_work, node);
200 list_del_init(&work->node);
201 seq = work->queue_seq;
204 spin_unlock_irq(&dev->work_lock);
207 __set_current_state(TASK_RUNNING);
217 /* Helper to allocate iovec buffers for all vqs. */
218 static long vhost_dev_alloc_iovecs(struct vhost_dev *dev)
221 for (i = 0; i < dev->nvqs; ++i) {
222 dev->vqs[i].indirect = kmalloc(sizeof *dev->vqs[i].indirect *
223 UIO_MAXIOV, GFP_KERNEL);
224 dev->vqs[i].log = kmalloc(sizeof *dev->vqs[i].log * UIO_MAXIOV,
226 dev->vqs[i].heads = kmalloc(sizeof *dev->vqs[i].heads *
227 UIO_MAXIOV, GFP_KERNEL);
229 if (!dev->vqs[i].indirect || !dev->vqs[i].log ||
235 for (; i >= 0; --i) {
236 kfree(dev->vqs[i].indirect);
237 kfree(dev->vqs[i].log);
238 kfree(dev->vqs[i].heads);
243 static void vhost_dev_free_iovecs(struct vhost_dev *dev)
246 for (i = 0; i < dev->nvqs; ++i) {
247 kfree(dev->vqs[i].indirect);
248 dev->vqs[i].indirect = NULL;
249 kfree(dev->vqs[i].log);
250 dev->vqs[i].log = NULL;
251 kfree(dev->vqs[i].heads);
252 dev->vqs[i].heads = NULL;
256 long vhost_dev_init(struct vhost_dev *dev,
257 struct vhost_virtqueue *vqs, int nvqs)
263 mutex_init(&dev->mutex);
265 dev->log_file = NULL;
268 spin_lock_init(&dev->work_lock);
269 INIT_LIST_HEAD(&dev->work_list);
272 for (i = 0; i < dev->nvqs; ++i) {
273 dev->vqs[i].log = NULL;
274 dev->vqs[i].indirect = NULL;
275 dev->vqs[i].heads = NULL;
276 dev->vqs[i].dev = dev;
277 mutex_init(&dev->vqs[i].mutex);
278 vhost_vq_reset(dev, dev->vqs + i);
279 if (dev->vqs[i].handle_kick)
280 vhost_poll_init(&dev->vqs[i].poll,
281 dev->vqs[i].handle_kick, POLLIN, dev);
287 /* Caller should have device mutex */
288 long vhost_dev_check_owner(struct vhost_dev *dev)
290 /* Are you the owner? If not, I don't think you mean to do that */
291 return dev->mm == current->mm ? 0 : -EPERM;
294 struct vhost_attach_cgroups_struct {
295 struct vhost_work work;
296 struct task_struct *owner;
300 static void vhost_attach_cgroups_work(struct vhost_work *work)
302 struct vhost_attach_cgroups_struct *s;
303 s = container_of(work, struct vhost_attach_cgroups_struct, work);
304 s->ret = cgroup_attach_task_all(s->owner, current);
307 static int vhost_attach_cgroups(struct vhost_dev *dev)
309 struct vhost_attach_cgroups_struct attach;
310 attach.owner = current;
311 vhost_work_init(&attach.work, vhost_attach_cgroups_work);
312 vhost_work_queue(dev, &attach.work);
313 vhost_work_flush(dev, &attach.work);
317 /* Caller should have device mutex */
318 static long vhost_dev_set_owner(struct vhost_dev *dev)
320 struct task_struct *worker;
322 /* Is there an owner already? */
327 /* No owner, become one */
328 dev->mm = get_task_mm(current);
329 worker = kthread_create(vhost_worker, dev, "vhost-%d", current->pid);
330 if (IS_ERR(worker)) {
331 err = PTR_ERR(worker);
335 dev->worker = worker;
336 wake_up_process(worker); /* avoid contributing to loadavg */
338 err = vhost_attach_cgroups(dev);
342 err = vhost_dev_alloc_iovecs(dev);
348 kthread_stop(worker);
358 /* Caller should have device mutex */
359 long vhost_dev_reset_owner(struct vhost_dev *dev)
361 struct vhost_memory *memory;
363 /* Restore memory to default empty mapping. */
364 memory = kmalloc(offsetof(struct vhost_memory, regions), GFP_KERNEL);
368 vhost_dev_cleanup(dev);
370 memory->nregions = 0;
371 RCU_INIT_POINTER(dev->memory, memory);
375 /* Caller should have device mutex */
376 void vhost_dev_cleanup(struct vhost_dev *dev)
379 for (i = 0; i < dev->nvqs; ++i) {
380 if (dev->vqs[i].kick && dev->vqs[i].handle_kick) {
381 vhost_poll_stop(&dev->vqs[i].poll);
382 vhost_poll_flush(&dev->vqs[i].poll);
384 if (dev->vqs[i].error_ctx)
385 eventfd_ctx_put(dev->vqs[i].error_ctx);
386 if (dev->vqs[i].error)
387 fput(dev->vqs[i].error);
388 if (dev->vqs[i].kick)
389 fput(dev->vqs[i].kick);
390 if (dev->vqs[i].call_ctx)
391 eventfd_ctx_put(dev->vqs[i].call_ctx);
392 if (dev->vqs[i].call)
393 fput(dev->vqs[i].call);
394 vhost_vq_reset(dev, dev->vqs + i);
396 vhost_dev_free_iovecs(dev);
398 eventfd_ctx_put(dev->log_ctx);
402 dev->log_file = NULL;
403 /* No one will access memory at this point */
404 kfree(rcu_dereference_protected(dev->memory,
405 lockdep_is_held(&dev->mutex)));
406 RCU_INIT_POINTER(dev->memory, NULL);
407 WARN_ON(!list_empty(&dev->work_list));
409 kthread_stop(dev->worker);
417 static int log_access_ok(void __user *log_base, u64 addr, unsigned long sz)
419 u64 a = addr / VHOST_PAGE_SIZE / 8;
420 /* Make sure 64 bit math will not overflow. */
421 if (a > ULONG_MAX - (unsigned long)log_base ||
422 a + (unsigned long)log_base > ULONG_MAX)
425 return access_ok(VERIFY_WRITE, log_base + a,
426 (sz + VHOST_PAGE_SIZE * 8 - 1) / VHOST_PAGE_SIZE / 8);
429 /* Caller should have vq mutex and device mutex. */
430 static int vq_memory_access_ok(void __user *log_base, struct vhost_memory *mem,
438 for (i = 0; i < mem->nregions; ++i) {
439 struct vhost_memory_region *m = mem->regions + i;
440 unsigned long a = m->userspace_addr;
441 if (m->memory_size > ULONG_MAX)
443 else if (!access_ok(VERIFY_WRITE, (void __user *)a,
446 else if (log_all && !log_access_ok(log_base,
454 /* Can we switch to this memory table? */
455 /* Caller should have device mutex but not vq mutex */
456 static int memory_access_ok(struct vhost_dev *d, struct vhost_memory *mem,
460 for (i = 0; i < d->nvqs; ++i) {
462 mutex_lock(&d->vqs[i].mutex);
463 /* If ring is inactive, will check when it's enabled. */
464 if (d->vqs[i].private_data)
465 ok = vq_memory_access_ok(d->vqs[i].log_base, mem,
469 mutex_unlock(&d->vqs[i].mutex);
476 static int vq_access_ok(unsigned int num,
477 struct vring_desc __user *desc,
478 struct vring_avail __user *avail,
479 struct vring_used __user *used)
481 return access_ok(VERIFY_READ, desc, num * sizeof *desc) &&
482 access_ok(VERIFY_READ, avail,
483 sizeof *avail + num * sizeof *avail->ring) &&
484 access_ok(VERIFY_WRITE, used,
485 sizeof *used + num * sizeof *used->ring);
488 /* Can we log writes? */
489 /* Caller should have device mutex but not vq mutex */
490 int vhost_log_access_ok(struct vhost_dev *dev)
492 struct vhost_memory *mp;
494 mp = rcu_dereference_protected(dev->memory,
495 lockdep_is_held(&dev->mutex));
496 return memory_access_ok(dev, mp, 1);
499 /* Verify access for write logging. */
500 /* Caller should have vq mutex and device mutex */
501 static int vq_log_access_ok(struct vhost_virtqueue *vq, void __user *log_base)
503 struct vhost_memory *mp;
505 mp = rcu_dereference_protected(vq->dev->memory,
506 lockdep_is_held(&vq->mutex));
507 return vq_memory_access_ok(log_base, mp,
508 vhost_has_feature(vq->dev, VHOST_F_LOG_ALL)) &&
509 (!vq->log_used || log_access_ok(log_base, vq->log_addr,
511 vq->num * sizeof *vq->used->ring));
514 /* Can we start vq? */
515 /* Caller should have vq mutex and device mutex */
516 int vhost_vq_access_ok(struct vhost_virtqueue *vq)
518 return vq_access_ok(vq->num, vq->desc, vq->avail, vq->used) &&
519 vq_log_access_ok(vq, vq->log_base);
522 static long vhost_set_memory(struct vhost_dev *d, struct vhost_memory __user *m)
524 struct vhost_memory mem, *newmem, *oldmem;
525 unsigned long size = offsetof(struct vhost_memory, regions);
526 if (copy_from_user(&mem, m, size))
530 if (mem.nregions > VHOST_MEMORY_MAX_NREGIONS)
532 newmem = kmalloc(size + mem.nregions * sizeof *m->regions, GFP_KERNEL);
536 memcpy(newmem, &mem, size);
537 if (copy_from_user(newmem->regions, m->regions,
538 mem.nregions * sizeof *m->regions)) {
543 if (!memory_access_ok(d, newmem, vhost_has_feature(d, VHOST_F_LOG_ALL))) {
547 oldmem = rcu_dereference_protected(d->memory,
548 lockdep_is_held(&d->mutex));
549 rcu_assign_pointer(d->memory, newmem);
555 static int init_used(struct vhost_virtqueue *vq,
556 struct vring_used __user *used)
558 int r = put_user(vq->used_flags, &used->flags);
561 return get_user(vq->last_used_idx, &used->idx);
564 static long vhost_set_vring(struct vhost_dev *d, int ioctl, void __user *argp)
566 struct file *eventfp, *filep = NULL,
567 *pollstart = NULL, *pollstop = NULL;
568 struct eventfd_ctx *ctx = NULL;
569 u32 __user *idxp = argp;
570 struct vhost_virtqueue *vq;
571 struct vhost_vring_state s;
572 struct vhost_vring_file f;
573 struct vhost_vring_addr a;
577 r = get_user(idx, idxp);
585 mutex_lock(&vq->mutex);
588 case VHOST_SET_VRING_NUM:
589 /* Resizing ring with an active backend?
590 * You don't want to do that. */
591 if (vq->private_data) {
595 if (copy_from_user(&s, argp, sizeof s)) {
599 if (!s.num || s.num > 0xffff || (s.num & (s.num - 1))) {
605 case VHOST_SET_VRING_BASE:
606 /* Moving base with an active backend?
607 * You don't want to do that. */
608 if (vq->private_data) {
612 if (copy_from_user(&s, argp, sizeof s)) {
616 if (s.num > 0xffff) {
620 vq->last_avail_idx = s.num;
621 /* Forget the cached index value. */
622 vq->avail_idx = vq->last_avail_idx;
624 case VHOST_GET_VRING_BASE:
626 s.num = vq->last_avail_idx;
627 if (copy_to_user(argp, &s, sizeof s))
630 case VHOST_SET_VRING_ADDR:
631 if (copy_from_user(&a, argp, sizeof a)) {
635 if (a.flags & ~(0x1 << VHOST_VRING_F_LOG)) {
639 /* For 32bit, verify that the top 32bits of the user
640 data are set to zero. */
641 if ((u64)(unsigned long)a.desc_user_addr != a.desc_user_addr ||
642 (u64)(unsigned long)a.used_user_addr != a.used_user_addr ||
643 (u64)(unsigned long)a.avail_user_addr != a.avail_user_addr) {
647 if ((a.avail_user_addr & (sizeof *vq->avail->ring - 1)) ||
648 (a.used_user_addr & (sizeof *vq->used->ring - 1)) ||
649 (a.log_guest_addr & (sizeof *vq->used->ring - 1))) {
654 /* We only verify access here if backend is configured.
655 * If it is not, we don't as size might not have been setup.
656 * We will verify when backend is configured. */
657 if (vq->private_data) {
658 if (!vq_access_ok(vq->num,
659 (void __user *)(unsigned long)a.desc_user_addr,
660 (void __user *)(unsigned long)a.avail_user_addr,
661 (void __user *)(unsigned long)a.used_user_addr)) {
666 /* Also validate log access for used ring if enabled. */
667 if ((a.flags & (0x1 << VHOST_VRING_F_LOG)) &&
668 !log_access_ok(vq->log_base, a.log_guest_addr,
670 vq->num * sizeof *vq->used->ring)) {
676 r = init_used(vq, (struct vring_used __user *)(unsigned long)
680 vq->log_used = !!(a.flags & (0x1 << VHOST_VRING_F_LOG));
681 vq->desc = (void __user *)(unsigned long)a.desc_user_addr;
682 vq->avail = (void __user *)(unsigned long)a.avail_user_addr;
683 vq->log_addr = a.log_guest_addr;
684 vq->used = (void __user *)(unsigned long)a.used_user_addr;
686 case VHOST_SET_VRING_KICK:
687 if (copy_from_user(&f, argp, sizeof f)) {
691 eventfp = f.fd == -1 ? NULL : eventfd_fget(f.fd);
692 if (IS_ERR(eventfp)) {
693 r = PTR_ERR(eventfp);
696 if (eventfp != vq->kick) {
697 pollstop = filep = vq->kick;
698 pollstart = vq->kick = eventfp;
702 case VHOST_SET_VRING_CALL:
703 if (copy_from_user(&f, argp, sizeof f)) {
707 eventfp = f.fd == -1 ? NULL : eventfd_fget(f.fd);
708 if (IS_ERR(eventfp)) {
709 r = PTR_ERR(eventfp);
712 if (eventfp != vq->call) {
716 vq->call_ctx = eventfp ?
717 eventfd_ctx_fileget(eventfp) : NULL;
721 case VHOST_SET_VRING_ERR:
722 if (copy_from_user(&f, argp, sizeof f)) {
726 eventfp = f.fd == -1 ? NULL : eventfd_fget(f.fd);
727 if (IS_ERR(eventfp)) {
728 r = PTR_ERR(eventfp);
731 if (eventfp != vq->error) {
735 vq->error_ctx = eventfp ?
736 eventfd_ctx_fileget(eventfp) : NULL;
744 if (pollstop && vq->handle_kick)
745 vhost_poll_stop(&vq->poll);
748 eventfd_ctx_put(ctx);
752 if (pollstart && vq->handle_kick)
753 vhost_poll_start(&vq->poll, vq->kick);
755 mutex_unlock(&vq->mutex);
757 if (pollstop && vq->handle_kick)
758 vhost_poll_flush(&vq->poll);
762 /* Caller must have device mutex */
763 long vhost_dev_ioctl(struct vhost_dev *d, unsigned int ioctl, unsigned long arg)
765 void __user *argp = (void __user *)arg;
766 struct file *eventfp, *filep = NULL;
767 struct eventfd_ctx *ctx = NULL;
772 /* If you are not the owner, you can become one */
773 if (ioctl == VHOST_SET_OWNER) {
774 r = vhost_dev_set_owner(d);
778 /* You must be the owner to do anything else */
779 r = vhost_dev_check_owner(d);
784 case VHOST_SET_MEM_TABLE:
785 r = vhost_set_memory(d, argp);
787 case VHOST_SET_LOG_BASE:
788 if (copy_from_user(&p, argp, sizeof p)) {
792 if ((u64)(unsigned long)p != p) {
796 for (i = 0; i < d->nvqs; ++i) {
797 struct vhost_virtqueue *vq;
798 void __user *base = (void __user *)(unsigned long)p;
800 mutex_lock(&vq->mutex);
801 /* If ring is inactive, will check when it's enabled. */
802 if (vq->private_data && !vq_log_access_ok(vq, base))
806 mutex_unlock(&vq->mutex);
809 case VHOST_SET_LOG_FD:
810 r = get_user(fd, (int __user *)argp);
813 eventfp = fd == -1 ? NULL : eventfd_fget(fd);
814 if (IS_ERR(eventfp)) {
815 r = PTR_ERR(eventfp);
818 if (eventfp != d->log_file) {
821 d->log_ctx = eventfp ?
822 eventfd_ctx_fileget(eventfp) : NULL;
825 for (i = 0; i < d->nvqs; ++i) {
826 mutex_lock(&d->vqs[i].mutex);
827 d->vqs[i].log_ctx = d->log_ctx;
828 mutex_unlock(&d->vqs[i].mutex);
831 eventfd_ctx_put(ctx);
836 r = vhost_set_vring(d, ioctl, argp);
843 static const struct vhost_memory_region *find_region(struct vhost_memory *mem,
844 __u64 addr, __u32 len)
846 struct vhost_memory_region *reg;
848 /* linear search is not brilliant, but we really have on the order of 6
849 * regions in practice */
850 for (i = 0; i < mem->nregions; ++i) {
851 reg = mem->regions + i;
852 if (reg->guest_phys_addr <= addr &&
853 reg->guest_phys_addr + reg->memory_size - 1 >= addr)
859 /* TODO: This is really inefficient. We need something like get_user()
860 * (instruction directly accesses the data, with an exception table entry
861 * returning -EFAULT). See Documentation/x86/exception-tables.txt.
863 static int set_bit_to_user(int nr, void __user *addr)
865 unsigned long log = (unsigned long)addr;
868 int bit = nr + (log % PAGE_SIZE) * 8;
870 r = get_user_pages_fast(log, 1, 1, &page);
874 base = kmap_atomic(page, KM_USER0);
876 kunmap_atomic(base, KM_USER0);
877 set_page_dirty_lock(page);
882 static int log_write(void __user *log_base,
883 u64 write_address, u64 write_length)
885 u64 write_page = write_address / VHOST_PAGE_SIZE;
889 write_length += write_address % VHOST_PAGE_SIZE;
891 u64 base = (u64)(unsigned long)log_base;
892 u64 log = base + write_page / 8;
893 int bit = write_page % 8;
894 if ((u64)(unsigned long)log != log)
896 r = set_bit_to_user(bit, (void __user *)(unsigned long)log);
899 if (write_length <= VHOST_PAGE_SIZE)
901 write_length -= VHOST_PAGE_SIZE;
907 int vhost_log_write(struct vhost_virtqueue *vq, struct vhost_log *log,
908 unsigned int log_num, u64 len)
912 /* Make sure data written is seen before log. */
914 for (i = 0; i < log_num; ++i) {
915 u64 l = min(log[i].len, len);
916 r = log_write(vq->log_base, log[i].addr, l);
922 eventfd_signal(vq->log_ctx, 1);
926 /* Length written exceeds what we have stored. This is a bug. */
931 static int translate_desc(struct vhost_dev *dev, u64 addr, u32 len,
932 struct iovec iov[], int iov_size)
934 const struct vhost_memory_region *reg;
935 struct vhost_memory *mem;
942 mem = rcu_dereference(dev->memory);
943 while ((u64)len > s) {
945 if (unlikely(ret >= iov_size)) {
949 reg = find_region(mem, addr, len);
950 if (unlikely(!reg)) {
955 size = reg->memory_size - addr + reg->guest_phys_addr;
956 _iov->iov_len = min((u64)len, size);
957 _iov->iov_base = (void __user *)(unsigned long)
958 (reg->userspace_addr + addr - reg->guest_phys_addr);
968 /* Each buffer in the virtqueues is actually a chain of descriptors. This
969 * function returns the next descriptor in the chain,
970 * or -1U if we're at the end. */
971 static unsigned next_desc(struct vring_desc *desc)
975 /* If this descriptor says it doesn't chain, we're done. */
976 if (!(desc->flags & VRING_DESC_F_NEXT))
979 /* Check they're not leading us off end of descriptors. */
981 /* Make sure compiler knows to grab that: we don't want it changing! */
982 /* We will use the result as an index in an array, so most
983 * architectures only need a compiler barrier here. */
984 read_barrier_depends();
989 static int get_indirect(struct vhost_dev *dev, struct vhost_virtqueue *vq,
990 struct iovec iov[], unsigned int iov_size,
991 unsigned int *out_num, unsigned int *in_num,
992 struct vhost_log *log, unsigned int *log_num,
993 struct vring_desc *indirect)
995 struct vring_desc desc;
996 unsigned int i = 0, count, found = 0;
1000 if (unlikely(indirect->len % sizeof desc)) {
1001 vq_err(vq, "Invalid length in indirect descriptor: "
1002 "len 0x%llx not multiple of 0x%zx\n",
1003 (unsigned long long)indirect->len,
1008 ret = translate_desc(dev, indirect->addr, indirect->len, vq->indirect,
1010 if (unlikely(ret < 0)) {
1011 vq_err(vq, "Translation failure %d in indirect.\n", ret);
1015 /* We will use the result as an address to read from, so most
1016 * architectures only need a compiler barrier here. */
1017 read_barrier_depends();
1019 count = indirect->len / sizeof desc;
1020 /* Buffers are chained via a 16 bit next field, so
1021 * we can have at most 2^16 of these. */
1022 if (unlikely(count > USHRT_MAX + 1)) {
1023 vq_err(vq, "Indirect buffer length too big: %d\n",
1029 unsigned iov_count = *in_num + *out_num;
1030 if (unlikely(++found > count)) {
1031 vq_err(vq, "Loop detected: last one at %u "
1032 "indirect size %u\n",
1036 if (unlikely(memcpy_fromiovec((unsigned char *)&desc, vq->indirect,
1038 vq_err(vq, "Failed indirect descriptor: idx %d, %zx\n",
1039 i, (size_t)indirect->addr + i * sizeof desc);
1042 if (unlikely(desc.flags & VRING_DESC_F_INDIRECT)) {
1043 vq_err(vq, "Nested indirect descriptor: idx %d, %zx\n",
1044 i, (size_t)indirect->addr + i * sizeof desc);
1048 ret = translate_desc(dev, desc.addr, desc.len, iov + iov_count,
1049 iov_size - iov_count);
1050 if (unlikely(ret < 0)) {
1051 vq_err(vq, "Translation failure %d indirect idx %d\n",
1055 /* If this is an input descriptor, increment that count. */
1056 if (desc.flags & VRING_DESC_F_WRITE) {
1058 if (unlikely(log)) {
1059 log[*log_num].addr = desc.addr;
1060 log[*log_num].len = desc.len;
1064 /* If it's an output descriptor, they're all supposed
1065 * to come before any input descriptors. */
1066 if (unlikely(*in_num)) {
1067 vq_err(vq, "Indirect descriptor "
1068 "has out after in: idx %d\n", i);
1073 } while ((i = next_desc(&desc)) != -1);
1077 /* This looks in the virtqueue and for the first available buffer, and converts
1078 * it to an iovec for convenient access. Since descriptors consist of some
1079 * number of output then some number of input descriptors, it's actually two
1080 * iovecs, but we pack them into one and note how many of each there were.
1082 * This function returns the descriptor number found, or vq->num (which is
1083 * never a valid descriptor number) if none was found. A negative code is
1084 * returned on error. */
1085 int vhost_get_vq_desc(struct vhost_dev *dev, struct vhost_virtqueue *vq,
1086 struct iovec iov[], unsigned int iov_size,
1087 unsigned int *out_num, unsigned int *in_num,
1088 struct vhost_log *log, unsigned int *log_num)
1090 struct vring_desc desc;
1091 unsigned int i, head, found = 0;
1095 /* Check it isn't doing very strange things with descriptor numbers. */
1096 last_avail_idx = vq->last_avail_idx;
1097 if (unlikely(__get_user(vq->avail_idx, &vq->avail->idx))) {
1098 vq_err(vq, "Failed to access avail idx at %p\n",
1103 if (unlikely((u16)(vq->avail_idx - last_avail_idx) > vq->num)) {
1104 vq_err(vq, "Guest moved used index from %u to %u",
1105 last_avail_idx, vq->avail_idx);
1109 /* If there's nothing new since last we looked, return invalid. */
1110 if (vq->avail_idx == last_avail_idx)
1113 /* Only get avail ring entries after they have been exposed by guest. */
1116 /* Grab the next descriptor number they're advertising, and increment
1117 * the index we've seen. */
1118 if (unlikely(__get_user(head,
1119 &vq->avail->ring[last_avail_idx % vq->num]))) {
1120 vq_err(vq, "Failed to read head: idx %d address %p\n",
1122 &vq->avail->ring[last_avail_idx % vq->num]);
1126 /* If their number is silly, that's an error. */
1127 if (unlikely(head >= vq->num)) {
1128 vq_err(vq, "Guest says index %u > %u is available",
1133 /* When we start there are none of either input nor output. */
1134 *out_num = *in_num = 0;
1140 unsigned iov_count = *in_num + *out_num;
1141 if (unlikely(i >= vq->num)) {
1142 vq_err(vq, "Desc index is %u > %u, head = %u",
1146 if (unlikely(++found > vq->num)) {
1147 vq_err(vq, "Loop detected: last one at %u "
1148 "vq size %u head %u\n",
1152 ret = copy_from_user(&desc, vq->desc + i, sizeof desc);
1153 if (unlikely(ret)) {
1154 vq_err(vq, "Failed to get descriptor: idx %d addr %p\n",
1158 if (desc.flags & VRING_DESC_F_INDIRECT) {
1159 ret = get_indirect(dev, vq, iov, iov_size,
1161 log, log_num, &desc);
1162 if (unlikely(ret < 0)) {
1163 vq_err(vq, "Failure detected "
1164 "in indirect descriptor at idx %d\n", i);
1170 ret = translate_desc(dev, desc.addr, desc.len, iov + iov_count,
1171 iov_size - iov_count);
1172 if (unlikely(ret < 0)) {
1173 vq_err(vq, "Translation failure %d descriptor idx %d\n",
1177 if (desc.flags & VRING_DESC_F_WRITE) {
1178 /* If this is an input descriptor,
1179 * increment that count. */
1181 if (unlikely(log)) {
1182 log[*log_num].addr = desc.addr;
1183 log[*log_num].len = desc.len;
1187 /* If it's an output descriptor, they're all supposed
1188 * to come before any input descriptors. */
1189 if (unlikely(*in_num)) {
1190 vq_err(vq, "Descriptor has out after in: "
1196 } while ((i = next_desc(&desc)) != -1);
1198 /* On success, increment avail index. */
1199 vq->last_avail_idx++;
1203 /* Reverse the effect of vhost_get_vq_desc. Useful for error handling. */
1204 void vhost_discard_vq_desc(struct vhost_virtqueue *vq, int n)
1206 vq->last_avail_idx -= n;
1209 /* After we've used one of their buffers, we tell them about it. We'll then
1210 * want to notify the guest, using eventfd. */
1211 int vhost_add_used(struct vhost_virtqueue *vq, unsigned int head, int len)
1213 struct vring_used_elem __user *used;
1215 /* The virtqueue contains a ring of used buffers. Get a pointer to the
1216 * next entry in that used ring. */
1217 used = &vq->used->ring[vq->last_used_idx % vq->num];
1218 if (__put_user(head, &used->id)) {
1219 vq_err(vq, "Failed to write used id");
1222 if (__put_user(len, &used->len)) {
1223 vq_err(vq, "Failed to write used len");
1226 /* Make sure buffer is written before we update index. */
1228 if (__put_user(vq->last_used_idx + 1, &vq->used->idx)) {
1229 vq_err(vq, "Failed to increment used idx");
1232 if (unlikely(vq->log_used)) {
1233 /* Make sure data is seen before log. */
1235 /* Log used ring entry write. */
1236 log_write(vq->log_base,
1238 ((void __user *)used - (void __user *)vq->used),
1240 /* Log used index update. */
1241 log_write(vq->log_base,
1242 vq->log_addr + offsetof(struct vring_used, idx),
1243 sizeof vq->used->idx);
1245 eventfd_signal(vq->log_ctx, 1);
1247 vq->last_used_idx++;
1251 static int __vhost_add_used_n(struct vhost_virtqueue *vq,
1252 struct vring_used_elem *heads,
1255 struct vring_used_elem __user *used;
1258 start = vq->last_used_idx % vq->num;
1259 used = vq->used->ring + start;
1260 if (__copy_to_user(used, heads, count * sizeof *used)) {
1261 vq_err(vq, "Failed to write used");
1264 if (unlikely(vq->log_used)) {
1265 /* Make sure data is seen before log. */
1267 /* Log used ring entry write. */
1268 log_write(vq->log_base,
1270 ((void __user *)used - (void __user *)vq->used),
1271 count * sizeof *used);
1273 vq->last_used_idx += count;
1277 /* After we've used one of their buffers, we tell them about it. We'll then
1278 * want to notify the guest, using eventfd. */
1279 int vhost_add_used_n(struct vhost_virtqueue *vq, struct vring_used_elem *heads,
1284 start = vq->last_used_idx % vq->num;
1285 n = vq->num - start;
1287 r = __vhost_add_used_n(vq, heads, n);
1293 r = __vhost_add_used_n(vq, heads, count);
1295 /* Make sure buffer is written before we update index. */
1297 if (put_user(vq->last_used_idx, &vq->used->idx)) {
1298 vq_err(vq, "Failed to increment used idx");
1301 if (unlikely(vq->log_used)) {
1302 /* Log used index update. */
1303 log_write(vq->log_base,
1304 vq->log_addr + offsetof(struct vring_used, idx),
1305 sizeof vq->used->idx);
1307 eventfd_signal(vq->log_ctx, 1);
1312 /* This actually signals the guest, using eventfd. */
1313 void vhost_signal(struct vhost_dev *dev, struct vhost_virtqueue *vq)
1316 /* Flush out used index updates. This is paired
1317 * with the barrier that the Guest executes when enabling
1321 if (__get_user(flags, &vq->avail->flags)) {
1322 vq_err(vq, "Failed to get flags");
1326 /* If they don't want an interrupt, don't signal, unless empty. */
1327 if ((flags & VRING_AVAIL_F_NO_INTERRUPT) &&
1328 (vq->avail_idx != vq->last_avail_idx ||
1329 !vhost_has_feature(dev, VIRTIO_F_NOTIFY_ON_EMPTY)))
1332 /* Signal the Guest tell them we used something up. */
1334 eventfd_signal(vq->call_ctx, 1);
1337 /* And here's the combo meal deal. Supersize me! */
1338 void vhost_add_used_and_signal(struct vhost_dev *dev,
1339 struct vhost_virtqueue *vq,
1340 unsigned int head, int len)
1342 vhost_add_used(vq, head, len);
1343 vhost_signal(dev, vq);
1346 /* multi-buffer version of vhost_add_used_and_signal */
1347 void vhost_add_used_and_signal_n(struct vhost_dev *dev,
1348 struct vhost_virtqueue *vq,
1349 struct vring_used_elem *heads, unsigned count)
1351 vhost_add_used_n(vq, heads, count);
1352 vhost_signal(dev, vq);
1355 /* OK, now we need to know about added descriptors. */
1356 bool vhost_enable_notify(struct vhost_virtqueue *vq)
1360 if (!(vq->used_flags & VRING_USED_F_NO_NOTIFY))
1362 vq->used_flags &= ~VRING_USED_F_NO_NOTIFY;
1363 r = put_user(vq->used_flags, &vq->used->flags);
1365 vq_err(vq, "Failed to enable notification at %p: %d\n",
1366 &vq->used->flags, r);
1369 /* They could have slipped one in as we were doing that: make
1370 * sure it's written, then check again. */
1372 r = __get_user(avail_idx, &vq->avail->idx);
1374 vq_err(vq, "Failed to check avail idx at %p: %d\n",
1375 &vq->avail->idx, r);
1379 return avail_idx != vq->avail_idx;
1382 /* We don't need to be notified again. */
1383 void vhost_disable_notify(struct vhost_virtqueue *vq)
1386 if (vq->used_flags & VRING_USED_F_NO_NOTIFY)
1388 vq->used_flags |= VRING_USED_F_NO_NOTIFY;
1389 r = put_user(vq->used_flags, &vq->used->flags);
1391 vq_err(vq, "Failed to enable notification at %p: %d\n",
1392 &vq->used->flags, r);