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/miscdevice.h>
19 #include <linux/mutex.h>
20 #include <linux/workqueue.h>
21 #include <linux/rcupdate.h>
22 #include <linux/poll.h>
23 #include <linux/file.h>
24 #include <linux/highmem.h>
26 #include <linux/net.h>
27 #include <linux/if_packet.h>
28 #include <linux/if_arp.h>
35 VHOST_MEMORY_MAX_NREGIONS = 64,
36 VHOST_MEMORY_F_LOG = 0x1,
39 static struct workqueue_struct *vhost_workqueue;
41 static void vhost_poll_func(struct file *file, wait_queue_head_t *wqh,
44 struct vhost_poll *poll;
45 poll = container_of(pt, struct vhost_poll, table);
48 add_wait_queue(wqh, &poll->wait);
51 static int vhost_poll_wakeup(wait_queue_t *wait, unsigned mode, int sync,
54 struct vhost_poll *poll;
55 poll = container_of(wait, struct vhost_poll, wait);
56 if (!((unsigned long)key & poll->mask))
59 queue_work(vhost_workqueue, &poll->work);
63 /* Init poll structure */
64 void vhost_poll_init(struct vhost_poll *poll, work_func_t func,
67 INIT_WORK(&poll->work, func);
68 init_waitqueue_func_entry(&poll->wait, vhost_poll_wakeup);
69 init_poll_funcptr(&poll->table, vhost_poll_func);
73 /* Start polling a file. We add ourselves to file's wait queue. The caller must
74 * keep a reference to a file until after vhost_poll_stop is called. */
75 void vhost_poll_start(struct vhost_poll *poll, struct file *file)
78 mask = file->f_op->poll(file, &poll->table);
80 vhost_poll_wakeup(&poll->wait, 0, 0, (void *)mask);
83 /* Stop polling a file. After this function returns, it becomes safe to drop the
84 * file reference. You must also flush afterwards. */
85 void vhost_poll_stop(struct vhost_poll *poll)
87 remove_wait_queue(poll->wqh, &poll->wait);
90 /* Flush any work that has been scheduled. When calling this, don't hold any
91 * locks that are also used by the callback. */
92 void vhost_poll_flush(struct vhost_poll *poll)
94 flush_work(&poll->work);
97 void vhost_poll_queue(struct vhost_poll *poll)
99 queue_work(vhost_workqueue, &poll->work);
102 static void vhost_vq_reset(struct vhost_dev *dev,
103 struct vhost_virtqueue *vq)
109 vq->last_avail_idx = 0;
111 vq->last_used_idx = 0;
114 vq->log_used = false;
115 vq->log_addr = -1ull;
117 vq->private_data = NULL;
119 vq->error_ctx = NULL;
127 long vhost_dev_init(struct vhost_dev *dev,
128 struct vhost_virtqueue *vqs, int nvqs)
133 mutex_init(&dev->mutex);
135 dev->log_file = NULL;
139 for (i = 0; i < dev->nvqs; ++i) {
140 dev->vqs[i].dev = dev;
141 mutex_init(&dev->vqs[i].mutex);
142 vhost_vq_reset(dev, dev->vqs + i);
143 if (dev->vqs[i].handle_kick)
144 vhost_poll_init(&dev->vqs[i].poll,
145 dev->vqs[i].handle_kick,
151 /* Caller should have device mutex */
152 long vhost_dev_check_owner(struct vhost_dev *dev)
154 /* Are you the owner? If not, I don't think you mean to do that */
155 return dev->mm == current->mm ? 0 : -EPERM;
158 /* Caller should have device mutex */
159 static long vhost_dev_set_owner(struct vhost_dev *dev)
161 /* Is there an owner already? */
164 /* No owner, become one */
165 dev->mm = get_task_mm(current);
169 /* Caller should have device mutex */
170 long vhost_dev_reset_owner(struct vhost_dev *dev)
172 struct vhost_memory *memory;
174 /* Restore memory to default empty mapping. */
175 memory = kmalloc(offsetof(struct vhost_memory, regions), GFP_KERNEL);
179 vhost_dev_cleanup(dev);
181 memory->nregions = 0;
182 dev->memory = memory;
186 /* Caller should have device mutex */
187 void vhost_dev_cleanup(struct vhost_dev *dev)
190 for (i = 0; i < dev->nvqs; ++i) {
191 if (dev->vqs[i].kick && dev->vqs[i].handle_kick) {
192 vhost_poll_stop(&dev->vqs[i].poll);
193 vhost_poll_flush(&dev->vqs[i].poll);
195 if (dev->vqs[i].error_ctx)
196 eventfd_ctx_put(dev->vqs[i].error_ctx);
197 if (dev->vqs[i].error)
198 fput(dev->vqs[i].error);
199 if (dev->vqs[i].kick)
200 fput(dev->vqs[i].kick);
201 if (dev->vqs[i].call_ctx)
202 eventfd_ctx_put(dev->vqs[i].call_ctx);
203 if (dev->vqs[i].call)
204 fput(dev->vqs[i].call);
205 vhost_vq_reset(dev, dev->vqs + i);
208 eventfd_ctx_put(dev->log_ctx);
212 dev->log_file = NULL;
213 /* No one will access memory at this point */
221 static int log_access_ok(void __user *log_base, u64 addr, unsigned long sz)
223 u64 a = addr / VHOST_PAGE_SIZE / 8;
224 /* Make sure 64 bit math will not overflow. */
225 if (a > ULONG_MAX - (unsigned long)log_base ||
226 a + (unsigned long)log_base > ULONG_MAX)
229 return access_ok(VERIFY_WRITE, log_base + a,
230 (sz + VHOST_PAGE_SIZE * 8 - 1) / VHOST_PAGE_SIZE / 8);
233 /* Caller should have vq mutex and device mutex. */
234 static int vq_memory_access_ok(void __user *log_base, struct vhost_memory *mem,
242 for (i = 0; i < mem->nregions; ++i) {
243 struct vhost_memory_region *m = mem->regions + i;
244 unsigned long a = m->userspace_addr;
245 if (m->memory_size > ULONG_MAX)
247 else if (!access_ok(VERIFY_WRITE, (void __user *)a,
250 else if (log_all && !log_access_ok(log_base,
258 /* Can we switch to this memory table? */
259 /* Caller should have device mutex but not vq mutex */
260 static int memory_access_ok(struct vhost_dev *d, struct vhost_memory *mem,
264 for (i = 0; i < d->nvqs; ++i) {
266 mutex_lock(&d->vqs[i].mutex);
267 /* If ring is inactive, will check when it's enabled. */
268 if (d->vqs[i].private_data)
269 ok = vq_memory_access_ok(d->vqs[i].log_base, mem,
273 mutex_unlock(&d->vqs[i].mutex);
280 static int vq_access_ok(unsigned int num,
281 struct vring_desc __user *desc,
282 struct vring_avail __user *avail,
283 struct vring_used __user *used)
285 return access_ok(VERIFY_READ, desc, num * sizeof *desc) &&
286 access_ok(VERIFY_READ, avail,
287 sizeof *avail + num * sizeof *avail->ring) &&
288 access_ok(VERIFY_WRITE, used,
289 sizeof *used + num * sizeof *used->ring);
292 /* Can we log writes? */
293 /* Caller should have device mutex but not vq mutex */
294 int vhost_log_access_ok(struct vhost_dev *dev)
296 return memory_access_ok(dev, dev->memory, 1);
299 /* Verify access for write logging. */
300 /* Caller should have vq mutex and device mutex */
301 static int vq_log_access_ok(struct vhost_virtqueue *vq, void __user *log_base)
303 return vq_memory_access_ok(log_base, vq->dev->memory,
304 vhost_has_feature(vq->dev, VHOST_F_LOG_ALL)) &&
305 (!vq->log_used || log_access_ok(log_base, vq->log_addr,
307 vq->num * sizeof *vq->used->ring));
310 /* Can we start vq? */
311 /* Caller should have vq mutex and device mutex */
312 int vhost_vq_access_ok(struct vhost_virtqueue *vq)
314 return vq_access_ok(vq->num, vq->desc, vq->avail, vq->used) &&
315 vq_log_access_ok(vq, vq->log_base);
318 static long vhost_set_memory(struct vhost_dev *d, struct vhost_memory __user *m)
320 struct vhost_memory mem, *newmem, *oldmem;
321 unsigned long size = offsetof(struct vhost_memory, regions);
323 r = copy_from_user(&mem, m, size);
328 if (mem.nregions > VHOST_MEMORY_MAX_NREGIONS)
330 newmem = kmalloc(size + mem.nregions * sizeof *m->regions, GFP_KERNEL);
334 memcpy(newmem, &mem, size);
335 r = copy_from_user(newmem->regions, m->regions,
336 mem.nregions * sizeof *m->regions);
342 if (!memory_access_ok(d, newmem, vhost_has_feature(d, VHOST_F_LOG_ALL)))
345 rcu_assign_pointer(d->memory, newmem);
351 static int init_used(struct vhost_virtqueue *vq,
352 struct vring_used __user *used)
354 int r = put_user(vq->used_flags, &used->flags);
357 return get_user(vq->last_used_idx, &used->idx);
360 static long vhost_set_vring(struct vhost_dev *d, int ioctl, void __user *argp)
362 struct file *eventfp, *filep = NULL,
363 *pollstart = NULL, *pollstop = NULL;
364 struct eventfd_ctx *ctx = NULL;
365 u32 __user *idxp = argp;
366 struct vhost_virtqueue *vq;
367 struct vhost_vring_state s;
368 struct vhost_vring_file f;
369 struct vhost_vring_addr a;
373 r = get_user(idx, idxp);
381 mutex_lock(&vq->mutex);
384 case VHOST_SET_VRING_NUM:
385 /* Resizing ring with an active backend?
386 * You don't want to do that. */
387 if (vq->private_data) {
391 r = copy_from_user(&s, argp, sizeof s);
394 if (!s.num || s.num > 0xffff || (s.num & (s.num - 1))) {
400 case VHOST_SET_VRING_BASE:
401 /* Moving base with an active backend?
402 * You don't want to do that. */
403 if (vq->private_data) {
407 r = copy_from_user(&s, argp, sizeof s);
410 if (s.num > 0xffff) {
414 vq->last_avail_idx = s.num;
415 /* Forget the cached index value. */
416 vq->avail_idx = vq->last_avail_idx;
418 case VHOST_GET_VRING_BASE:
420 s.num = vq->last_avail_idx;
421 r = copy_to_user(argp, &s, sizeof s);
423 case VHOST_SET_VRING_ADDR:
424 r = copy_from_user(&a, argp, sizeof a);
427 if (a.flags & ~(0x1 << VHOST_VRING_F_LOG)) {
431 /* For 32bit, verify that the top 32bits of the user
432 data are set to zero. */
433 if ((u64)(unsigned long)a.desc_user_addr != a.desc_user_addr ||
434 (u64)(unsigned long)a.used_user_addr != a.used_user_addr ||
435 (u64)(unsigned long)a.avail_user_addr != a.avail_user_addr) {
439 if ((a.avail_user_addr & (sizeof *vq->avail->ring - 1)) ||
440 (a.used_user_addr & (sizeof *vq->used->ring - 1)) ||
441 (a.log_guest_addr & (sizeof *vq->used->ring - 1))) {
446 /* We only verify access here if backend is configured.
447 * If it is not, we don't as size might not have been setup.
448 * We will verify when backend is configured. */
449 if (vq->private_data) {
450 if (!vq_access_ok(vq->num,
451 (void __user *)(unsigned long)a.desc_user_addr,
452 (void __user *)(unsigned long)a.avail_user_addr,
453 (void __user *)(unsigned long)a.used_user_addr)) {
458 /* Also validate log access for used ring if enabled. */
459 if ((a.flags & (0x1 << VHOST_VRING_F_LOG)) &&
460 !log_access_ok(vq->log_base, a.log_guest_addr,
462 vq->num * sizeof *vq->used->ring)) {
468 r = init_used(vq, (struct vring_used __user *)(unsigned long)
472 vq->log_used = !!(a.flags & (0x1 << VHOST_VRING_F_LOG));
473 vq->desc = (void __user *)(unsigned long)a.desc_user_addr;
474 vq->avail = (void __user *)(unsigned long)a.avail_user_addr;
475 vq->log_addr = a.log_guest_addr;
476 vq->used = (void __user *)(unsigned long)a.used_user_addr;
478 case VHOST_SET_VRING_KICK:
479 r = copy_from_user(&f, argp, sizeof f);
482 eventfp = f.fd == -1 ? NULL : eventfd_fget(f.fd);
483 if (IS_ERR(eventfp)) {
484 r = PTR_ERR(eventfp);
487 if (eventfp != vq->kick) {
488 pollstop = filep = vq->kick;
489 pollstart = vq->kick = eventfp;
493 case VHOST_SET_VRING_CALL:
494 r = copy_from_user(&f, argp, sizeof f);
497 eventfp = f.fd == -1 ? NULL : eventfd_fget(f.fd);
498 if (IS_ERR(eventfp)) {
499 r = PTR_ERR(eventfp);
502 if (eventfp != vq->call) {
506 vq->call_ctx = eventfp ?
507 eventfd_ctx_fileget(eventfp) : NULL;
511 case VHOST_SET_VRING_ERR:
512 r = copy_from_user(&f, argp, sizeof f);
515 eventfp = f.fd == -1 ? NULL : eventfd_fget(f.fd);
516 if (IS_ERR(eventfp)) {
517 r = PTR_ERR(eventfp);
520 if (eventfp != vq->error) {
524 vq->error_ctx = eventfp ?
525 eventfd_ctx_fileget(eventfp) : NULL;
533 if (pollstop && vq->handle_kick)
534 vhost_poll_stop(&vq->poll);
537 eventfd_ctx_put(ctx);
541 if (pollstart && vq->handle_kick)
542 vhost_poll_start(&vq->poll, vq->kick);
544 mutex_unlock(&vq->mutex);
546 if (pollstop && vq->handle_kick)
547 vhost_poll_flush(&vq->poll);
551 /* Caller must have device mutex */
552 long vhost_dev_ioctl(struct vhost_dev *d, unsigned int ioctl, unsigned long arg)
554 void __user *argp = (void __user *)arg;
555 struct file *eventfp, *filep = NULL;
556 struct eventfd_ctx *ctx = NULL;
561 /* If you are not the owner, you can become one */
562 if (ioctl == VHOST_SET_OWNER) {
563 r = vhost_dev_set_owner(d);
567 /* You must be the owner to do anything else */
568 r = vhost_dev_check_owner(d);
573 case VHOST_SET_MEM_TABLE:
574 r = vhost_set_memory(d, argp);
576 case VHOST_SET_LOG_BASE:
577 r = copy_from_user(&p, argp, sizeof p);
580 if ((u64)(unsigned long)p != p) {
584 for (i = 0; i < d->nvqs; ++i) {
585 struct vhost_virtqueue *vq;
586 void __user *base = (void __user *)(unsigned long)p;
588 mutex_lock(&vq->mutex);
589 /* If ring is inactive, will check when it's enabled. */
590 if (vq->private_data && !vq_log_access_ok(vq, base))
594 mutex_unlock(&vq->mutex);
597 case VHOST_SET_LOG_FD:
598 r = get_user(fd, (int __user *)argp);
601 eventfp = fd == -1 ? NULL : eventfd_fget(fd);
602 if (IS_ERR(eventfp)) {
603 r = PTR_ERR(eventfp);
606 if (eventfp != d->log_file) {
609 d->log_ctx = eventfp ?
610 eventfd_ctx_fileget(eventfp) : NULL;
613 for (i = 0; i < d->nvqs; ++i) {
614 mutex_lock(&d->vqs[i].mutex);
615 d->vqs[i].log_ctx = d->log_ctx;
616 mutex_unlock(&d->vqs[i].mutex);
619 eventfd_ctx_put(ctx);
624 r = vhost_set_vring(d, ioctl, argp);
631 static const struct vhost_memory_region *find_region(struct vhost_memory *mem,
632 __u64 addr, __u32 len)
634 struct vhost_memory_region *reg;
636 /* linear search is not brilliant, but we really have on the order of 6
637 * regions in practice */
638 for (i = 0; i < mem->nregions; ++i) {
639 reg = mem->regions + i;
640 if (reg->guest_phys_addr <= addr &&
641 reg->guest_phys_addr + reg->memory_size - 1 >= addr)
647 /* TODO: This is really inefficient. We need something like get_user()
648 * (instruction directly accesses the data, with an exception table entry
649 * returning -EFAULT). See Documentation/x86/exception-tables.txt.
651 static int set_bit_to_user(int nr, void __user *addr)
653 unsigned long log = (unsigned long)addr;
656 int bit = nr + (log % PAGE_SIZE) * 8;
658 r = get_user_pages_fast(log, 1, 1, &page);
662 base = kmap_atomic(page, KM_USER0);
664 kunmap_atomic(base, KM_USER0);
665 set_page_dirty_lock(page);
670 static int log_write(void __user *log_base,
671 u64 write_address, u64 write_length)
676 write_address /= VHOST_PAGE_SIZE;
678 u64 base = (u64)(unsigned long)log_base;
679 u64 log = base + write_address / 8;
680 int bit = write_address % 8;
681 if ((u64)(unsigned long)log != log)
683 r = set_bit_to_user(bit, (void __user *)(unsigned long)log);
686 if (write_length <= VHOST_PAGE_SIZE)
688 write_length -= VHOST_PAGE_SIZE;
689 write_address += VHOST_PAGE_SIZE;
694 int vhost_log_write(struct vhost_virtqueue *vq, struct vhost_log *log,
695 unsigned int log_num, u64 len)
699 /* Make sure data written is seen before log. */
701 for (i = 0; i < log_num; ++i) {
702 u64 l = min(log[i].len, len);
703 r = log_write(vq->log_base, log[i].addr, l);
711 eventfd_signal(vq->log_ctx, 1);
712 /* Length written exceeds what we have stored. This is a bug. */
717 static int translate_desc(struct vhost_dev *dev, u64 addr, u32 len,
718 struct iovec iov[], int iov_size)
720 const struct vhost_memory_region *reg;
721 struct vhost_memory *mem;
728 mem = rcu_dereference(dev->memory);
729 while ((u64)len > s) {
731 if (ret >= iov_size) {
735 reg = find_region(mem, addr, len);
741 size = reg->memory_size - addr + reg->guest_phys_addr;
742 _iov->iov_len = min((u64)len, size);
743 _iov->iov_base = (void __user *)(unsigned long)
744 (reg->userspace_addr + addr - reg->guest_phys_addr);
754 /* Each buffer in the virtqueues is actually a chain of descriptors. This
755 * function returns the next descriptor in the chain,
756 * or -1U if we're at the end. */
757 static unsigned next_desc(struct vring_desc *desc)
761 /* If this descriptor says it doesn't chain, we're done. */
762 if (!(desc->flags & VRING_DESC_F_NEXT))
765 /* Check they're not leading us off end of descriptors. */
767 /* Make sure compiler knows to grab that: we don't want it changing! */
768 /* We will use the result as an index in an array, so most
769 * architectures only need a compiler barrier here. */
770 read_barrier_depends();
775 static unsigned get_indirect(struct vhost_dev *dev, struct vhost_virtqueue *vq,
776 struct iovec iov[], unsigned int iov_size,
777 unsigned int *out_num, unsigned int *in_num,
778 struct vhost_log *log, unsigned int *log_num,
779 struct vring_desc *indirect)
781 struct vring_desc desc;
782 unsigned int i = 0, count, found = 0;
786 if (indirect->len % sizeof desc) {
787 vq_err(vq, "Invalid length in indirect descriptor: "
788 "len 0x%llx not multiple of 0x%zx\n",
789 (unsigned long long)indirect->len,
794 ret = translate_desc(dev, indirect->addr, indirect->len, vq->indirect,
795 ARRAY_SIZE(vq->indirect));
797 vq_err(vq, "Translation failure %d in indirect.\n", ret);
801 /* We will use the result as an address to read from, so most
802 * architectures only need a compiler barrier here. */
803 read_barrier_depends();
805 count = indirect->len / sizeof desc;
806 /* Buffers are chained via a 16 bit next field, so
807 * we can have at most 2^16 of these. */
808 if (count > USHORT_MAX + 1) {
809 vq_err(vq, "Indirect buffer length too big: %d\n",
815 unsigned iov_count = *in_num + *out_num;
816 if (++found > count) {
817 vq_err(vq, "Loop detected: last one at %u "
818 "indirect size %u\n",
822 if (memcpy_fromiovec((unsigned char *)&desc, vq->indirect,
824 vq_err(vq, "Failed indirect descriptor: idx %d, %zx\n",
825 i, (size_t)indirect->addr + i * sizeof desc);
828 if (desc.flags & VRING_DESC_F_INDIRECT) {
829 vq_err(vq, "Nested indirect descriptor: idx %d, %zx\n",
830 i, (size_t)indirect->addr + i * sizeof desc);
834 ret = translate_desc(dev, desc.addr, desc.len, iov + iov_count,
835 iov_size - iov_count);
837 vq_err(vq, "Translation failure %d indirect idx %d\n",
841 /* If this is an input descriptor, increment that count. */
842 if (desc.flags & VRING_DESC_F_WRITE) {
845 log[*log_num].addr = desc.addr;
846 log[*log_num].len = desc.len;
850 /* If it's an output descriptor, they're all supposed
851 * to come before any input descriptors. */
853 vq_err(vq, "Indirect descriptor "
854 "has out after in: idx %d\n", i);
859 } while ((i = next_desc(&desc)) != -1);
863 /* This looks in the virtqueue and for the first available buffer, and converts
864 * it to an iovec for convenient access. Since descriptors consist of some
865 * number of output then some number of input descriptors, it's actually two
866 * iovecs, but we pack them into one and note how many of each there were.
868 * This function returns the descriptor number found, or vq->num (which
869 * is never a valid descriptor number) if none was found. */
870 unsigned vhost_get_vq_desc(struct vhost_dev *dev, struct vhost_virtqueue *vq,
871 struct iovec iov[], unsigned int iov_size,
872 unsigned int *out_num, unsigned int *in_num,
873 struct vhost_log *log, unsigned int *log_num)
875 struct vring_desc desc;
876 unsigned int i, head, found = 0;
880 /* Check it isn't doing very strange things with descriptor numbers. */
881 last_avail_idx = vq->last_avail_idx;
882 if (get_user(vq->avail_idx, &vq->avail->idx)) {
883 vq_err(vq, "Failed to access avail idx at %p\n",
888 if ((u16)(vq->avail_idx - last_avail_idx) > vq->num) {
889 vq_err(vq, "Guest moved used index from %u to %u",
890 last_avail_idx, vq->avail_idx);
894 /* If there's nothing new since last we looked, return invalid. */
895 if (vq->avail_idx == last_avail_idx)
898 /* Only get avail ring entries after they have been exposed by guest. */
901 /* Grab the next descriptor number they're advertising, and increment
902 * the index we've seen. */
903 if (get_user(head, &vq->avail->ring[last_avail_idx % vq->num])) {
904 vq_err(vq, "Failed to read head: idx %d address %p\n",
906 &vq->avail->ring[last_avail_idx % vq->num]);
910 /* If their number is silly, that's an error. */
911 if (head >= vq->num) {
912 vq_err(vq, "Guest says index %u > %u is available",
917 /* When we start there are none of either input nor output. */
918 *out_num = *in_num = 0;
924 unsigned iov_count = *in_num + *out_num;
926 vq_err(vq, "Desc index is %u > %u, head = %u",
930 if (++found > vq->num) {
931 vq_err(vq, "Loop detected: last one at %u "
932 "vq size %u head %u\n",
936 ret = copy_from_user(&desc, vq->desc + i, sizeof desc);
938 vq_err(vq, "Failed to get descriptor: idx %d addr %p\n",
942 if (desc.flags & VRING_DESC_F_INDIRECT) {
943 ret = get_indirect(dev, vq, iov, iov_size,
945 log, log_num, &desc);
947 vq_err(vq, "Failure detected "
948 "in indirect descriptor at idx %d\n", i);
954 ret = translate_desc(dev, desc.addr, desc.len, iov + iov_count,
955 iov_size - iov_count);
957 vq_err(vq, "Translation failure %d descriptor idx %d\n",
961 if (desc.flags & VRING_DESC_F_WRITE) {
962 /* If this is an input descriptor,
963 * increment that count. */
966 log[*log_num].addr = desc.addr;
967 log[*log_num].len = desc.len;
971 /* If it's an output descriptor, they're all supposed
972 * to come before any input descriptors. */
974 vq_err(vq, "Descriptor has out after in: "
980 } while ((i = next_desc(&desc)) != -1);
982 /* On success, increment avail index. */
983 vq->last_avail_idx++;
987 /* Reverse the effect of vhost_get_vq_desc. Useful for error handling. */
988 void vhost_discard_vq_desc(struct vhost_virtqueue *vq)
990 vq->last_avail_idx--;
993 /* After we've used one of their buffers, we tell them about it. We'll then
994 * want to notify the guest, using eventfd. */
995 int vhost_add_used(struct vhost_virtqueue *vq, unsigned int head, int len)
997 struct vring_used_elem __user *used;
999 /* The virtqueue contains a ring of used buffers. Get a pointer to the
1000 * next entry in that used ring. */
1001 used = &vq->used->ring[vq->last_used_idx % vq->num];
1002 if (put_user(head, &used->id)) {
1003 vq_err(vq, "Failed to write used id");
1006 if (put_user(len, &used->len)) {
1007 vq_err(vq, "Failed to write used len");
1010 /* Make sure buffer is written before we update index. */
1012 if (put_user(vq->last_used_idx + 1, &vq->used->idx)) {
1013 vq_err(vq, "Failed to increment used idx");
1016 if (unlikely(vq->log_used)) {
1017 /* Make sure data is seen before log. */
1019 /* Log used ring entry write. */
1020 log_write(vq->log_base,
1022 ((void __user *)used - (void __user *)vq->used),
1024 /* Log used index update. */
1025 log_write(vq->log_base,
1026 vq->log_addr + offsetof(struct vring_used, idx),
1027 sizeof vq->used->idx);
1029 eventfd_signal(vq->log_ctx, 1);
1031 vq->last_used_idx++;
1035 /* This actually signals the guest, using eventfd. */
1036 void vhost_signal(struct vhost_dev *dev, struct vhost_virtqueue *vq)
1039 if (get_user(flags, &vq->avail->flags)) {
1040 vq_err(vq, "Failed to get flags");
1044 /* If they don't want an interrupt, don't signal, unless empty. */
1045 if ((flags & VRING_AVAIL_F_NO_INTERRUPT) &&
1046 (vq->avail_idx != vq->last_avail_idx ||
1047 !vhost_has_feature(dev, VIRTIO_F_NOTIFY_ON_EMPTY)))
1050 /* Signal the Guest tell them we used something up. */
1052 eventfd_signal(vq->call_ctx, 1);
1055 /* And here's the combo meal deal. Supersize me! */
1056 void vhost_add_used_and_signal(struct vhost_dev *dev,
1057 struct vhost_virtqueue *vq,
1058 unsigned int head, int len)
1060 vhost_add_used(vq, head, len);
1061 vhost_signal(dev, vq);
1064 /* OK, now we need to know about added descriptors. */
1065 bool vhost_enable_notify(struct vhost_virtqueue *vq)
1069 if (!(vq->used_flags & VRING_USED_F_NO_NOTIFY))
1071 vq->used_flags &= ~VRING_USED_F_NO_NOTIFY;
1072 r = put_user(vq->used_flags, &vq->used->flags);
1074 vq_err(vq, "Failed to enable notification at %p: %d\n",
1075 &vq->used->flags, r);
1078 /* They could have slipped one in as we were doing that: make
1079 * sure it's written, then check again. */
1081 r = get_user(avail_idx, &vq->avail->idx);
1083 vq_err(vq, "Failed to check avail idx at %p: %d\n",
1084 &vq->avail->idx, r);
1088 return avail_idx != vq->last_avail_idx;
1091 /* We don't need to be notified again. */
1092 void vhost_disable_notify(struct vhost_virtqueue *vq)
1095 if (vq->used_flags & VRING_USED_F_NO_NOTIFY)
1097 vq->used_flags |= VRING_USED_F_NO_NOTIFY;
1098 r = put_user(vq->used_flags, &vq->used->flags);
1100 vq_err(vq, "Failed to enable notification at %p: %d\n",
1101 &vq->used->flags, r);
1104 int vhost_init(void)
1106 vhost_workqueue = create_singlethread_workqueue("vhost");
1107 if (!vhost_workqueue)
1112 void vhost_cleanup(void)
1114 destroy_workqueue(vhost_workqueue);