2 * Helpers for the host side of a virtio ring.
4 * Since these may be in userspace, we use (inline) accessors.
6 #include <linux/module.h>
7 #include <linux/vringh.h>
8 #include <linux/virtio_ring.h>
9 #include <linux/kernel.h>
10 #include <linux/ratelimit.h>
11 #include <linux/uaccess.h>
12 #include <linux/slab.h>
13 #include <linux/export.h>
15 static __printf(1,2) __cold void vringh_bad(const char *fmt, ...)
17 static DEFINE_RATELIMIT_STATE(vringh_rs,
18 DEFAULT_RATELIMIT_INTERVAL,
19 DEFAULT_RATELIMIT_BURST);
20 if (__ratelimit(&vringh_rs)) {
23 printk(KERN_NOTICE "vringh:");
29 /* Returns vring->num if empty, -ve on error. */
30 static inline int __vringh_get_head(const struct vringh *vrh,
31 int (*getu16)(u16 *val, const u16 *p),
34 u16 avail_idx, i, head;
37 err = getu16(&avail_idx, &vrh->vring.avail->idx);
39 vringh_bad("Failed to access avail idx at %p",
40 &vrh->vring.avail->idx);
44 if (*last_avail_idx == avail_idx)
45 return vrh->vring.num;
47 /* Only get avail ring entries after they have been exposed by guest. */
48 virtio_rmb(vrh->weak_barriers);
50 i = *last_avail_idx & (vrh->vring.num - 1);
52 err = getu16(&head, &vrh->vring.avail->ring[i]);
54 vringh_bad("Failed to read head: idx %d address %p",
55 *last_avail_idx, &vrh->vring.avail->ring[i]);
59 if (head >= vrh->vring.num) {
60 vringh_bad("Guest says index %u > %u is available",
61 head, vrh->vring.num);
69 /* Copy some bytes to/from the iovec. Returns num copied. */
70 static inline ssize_t vringh_iov_xfer(struct vringh_kiov *iov,
71 void *ptr, size_t len,
72 int (*xfer)(void *addr, void *ptr,
77 while (len && iov->i < iov->used) {
80 partlen = min(iov->iov[iov->i].iov_len, len);
81 err = xfer(iov->iov[iov->i].iov_base, ptr, partlen);
87 iov->consumed += partlen;
88 iov->iov[iov->i].iov_len -= partlen;
89 iov->iov[iov->i].iov_base += partlen;
91 if (!iov->iov[iov->i].iov_len) {
92 /* Fix up old iov element then increment. */
93 iov->iov[iov->i].iov_len = iov->consumed;
94 iov->iov[iov->i].iov_base -= iov->consumed;
103 /* May reduce *len if range is shorter. */
104 static inline bool range_check(struct vringh *vrh, u64 addr, size_t *len,
105 struct vringh_range *range,
106 bool (*getrange)(struct vringh *,
107 u64, struct vringh_range *))
109 if (addr < range->start || addr > range->end_incl) {
110 if (!getrange(vrh, addr, range))
113 BUG_ON(addr < range->start || addr > range->end_incl);
115 /* To end of memory? */
116 if (unlikely(addr + *len == 0)) {
117 if (range->end_incl == -1ULL)
122 /* Otherwise, don't wrap. */
123 if (addr + *len < addr) {
124 vringh_bad("Wrapping descriptor %zu@0x%llx",
125 *len, (unsigned long long)addr);
129 if (unlikely(addr + *len - 1 > range->end_incl))
134 *len = range->end_incl + 1 - addr;
138 static inline bool no_range_check(struct vringh *vrh, u64 addr, size_t *len,
139 struct vringh_range *range,
140 bool (*getrange)(struct vringh *,
141 u64, struct vringh_range *))
146 /* No reason for this code to be inline. */
147 static int move_to_indirect(int *up_next, u16 *i, void *addr,
148 const struct vring_desc *desc,
149 struct vring_desc **descs, int *desc_max)
151 /* Indirect tables can't have indirect. */
152 if (*up_next != -1) {
153 vringh_bad("Multilevel indirect %u->%u", *up_next, *i);
157 if (unlikely(desc->len % sizeof(struct vring_desc))) {
158 vringh_bad("Strange indirect len %u", desc->len);
162 /* We will check this when we follow it! */
163 if (desc->flags & VRING_DESC_F_NEXT)
164 *up_next = desc->next;
168 *desc_max = desc->len / sizeof(struct vring_desc);
170 /* Now, start at the first indirect. */
175 static int resize_iovec(struct vringh_kiov *iov, gfp_t gfp)
178 unsigned int flag, new_num = (iov->max_num & ~VRINGH_IOV_ALLOCATED) * 2;
183 flag = (iov->max_num & VRINGH_IOV_ALLOCATED);
185 new = krealloc(iov->iov, new_num * sizeof(struct iovec), gfp);
187 new = kmalloc(new_num * sizeof(struct iovec), gfp);
189 memcpy(new, iov->iov,
190 iov->max_num * sizeof(struct iovec));
191 flag = VRINGH_IOV_ALLOCATED;
197 iov->max_num = (new_num | flag);
201 static u16 __cold return_from_indirect(const struct vringh *vrh, int *up_next,
202 struct vring_desc **descs, int *desc_max)
207 *descs = vrh->vring.desc;
208 *desc_max = vrh->vring.num;
212 static int slow_copy(struct vringh *vrh, void *dst, const void *src,
213 bool (*rcheck)(struct vringh *vrh, u64 addr, size_t *len,
214 struct vringh_range *range,
215 bool (*getrange)(struct vringh *vrh,
217 struct vringh_range *)),
218 bool (*getrange)(struct vringh *vrh,
220 struct vringh_range *r),
221 struct vringh_range *range,
222 int (*copy)(void *dst, const void *src, size_t len))
224 size_t part, len = sizeof(struct vring_desc);
231 addr = (u64)(unsigned long)src - range->offset;
233 if (!rcheck(vrh, addr, &part, range, getrange))
236 err = copy(dst, src, part);
248 __vringh_iov(struct vringh *vrh, u16 i,
249 struct vringh_kiov *riov,
250 struct vringh_kiov *wiov,
251 bool (*rcheck)(struct vringh *vrh, u64 addr, size_t *len,
252 struct vringh_range *range,
253 bool (*getrange)(struct vringh *, u64,
254 struct vringh_range *)),
255 bool (*getrange)(struct vringh *, u64, struct vringh_range *),
257 int (*copy)(void *dst, const void *src, size_t len))
259 int err, count = 0, up_next, desc_max;
260 struct vring_desc desc, *descs;
261 struct vringh_range range = { -1ULL, 0 }, slowrange;
264 /* We start traversing vring's descriptor table. */
265 descs = vrh->vring.desc;
266 desc_max = vrh->vring.num;
270 riov->i = riov->used = 0;
272 wiov->i = wiov->used = 0;
274 /* You must want something! */
279 struct vringh_kiov *iov;
283 err = slow_copy(vrh, &desc, &descs[i], rcheck, getrange,
286 err = copy(&desc, &descs[i], sizeof(desc));
290 if (unlikely(desc.flags & VRING_DESC_F_INDIRECT)) {
291 /* Make sure it's OK, and get offset. */
293 if (!rcheck(vrh, desc.addr, &len, &range, getrange)) {
298 if (unlikely(len != desc.len)) {
300 /* We need to save this range to use offset */
304 addr = (void *)(long)(desc.addr + range.offset);
305 err = move_to_indirect(&up_next, &i, addr, &desc,
312 if (count++ == vrh->vring.num) {
313 vringh_bad("Descriptor loop in %p", descs);
318 if (desc.flags & VRING_DESC_F_WRITE)
322 if (unlikely(wiov && wiov->i)) {
323 vringh_bad("Readable desc %p after writable",
331 vringh_bad("Unexpected %s desc",
332 !wiov ? "writable" : "readable");
338 /* Make sure it's OK, and get offset. */
340 if (!rcheck(vrh, desc.addr, &len, &range, getrange)) {
344 addr = (void *)(unsigned long)(desc.addr + range.offset);
346 if (unlikely(iov->used == (iov->max_num & ~VRINGH_IOV_ALLOCATED))) {
347 err = resize_iovec(iov, gfp);
352 iov->iov[iov->used].iov_base = addr;
353 iov->iov[iov->used].iov_len = len;
356 if (unlikely(len != desc.len)) {
362 if (desc.flags & VRING_DESC_F_NEXT) {
365 /* Just in case we need to finish traversing above. */
366 if (unlikely(up_next > 0)) {
367 i = return_from_indirect(vrh, &up_next,
375 vringh_bad("Chained index %u > %u", i, desc_max);
387 static inline int __vringh_complete(struct vringh *vrh,
388 const struct vring_used_elem *used,
389 unsigned int num_used,
390 int (*putu16)(u16 *p, u16 val),
391 int (*putused)(struct vring_used_elem *dst,
392 const struct vring_used_elem
395 struct vring_used *used_ring;
399 used_ring = vrh->vring.used;
400 used_idx = vrh->last_used_idx + vrh->completed;
402 off = used_idx % vrh->vring.num;
404 /* Compiler knows num_used == 1 sometimes, hence extra check */
405 if (num_used > 1 && unlikely(off + num_used >= vrh->vring.num)) {
406 u16 part = vrh->vring.num - off;
407 err = putused(&used_ring->ring[off], used, part);
409 err = putused(&used_ring->ring[0], used + part,
412 err = putused(&used_ring->ring[off], used, num_used);
415 vringh_bad("Failed to write %u used entries %u at %p",
416 num_used, off, &used_ring->ring[off]);
420 /* Make sure buffer is written before we update index. */
421 virtio_wmb(vrh->weak_barriers);
423 err = putu16(&vrh->vring.used->idx, used_idx + num_used);
425 vringh_bad("Failed to update used index at %p",
426 &vrh->vring.used->idx);
430 vrh->completed += num_used;
435 static inline int __vringh_need_notify(struct vringh *vrh,
436 int (*getu16)(u16 *val, const u16 *p))
442 /* Flush out used index update. This is paired with the
443 * barrier that the Guest executes when enabling
445 virtio_mb(vrh->weak_barriers);
447 /* Old-style, without event indices. */
448 if (!vrh->event_indices) {
450 err = getu16(&flags, &vrh->vring.avail->flags);
452 vringh_bad("Failed to get flags at %p",
453 &vrh->vring.avail->flags);
456 return (!(flags & VRING_AVAIL_F_NO_INTERRUPT));
459 /* Modern: we know when other side wants to know. */
460 err = getu16(&used_event, &vring_used_event(&vrh->vring));
462 vringh_bad("Failed to get used event idx at %p",
463 &vring_used_event(&vrh->vring));
467 /* Just in case we added so many that we wrap. */
468 if (unlikely(vrh->completed > 0xffff))
471 notify = vring_need_event(used_event,
472 vrh->last_used_idx + vrh->completed,
475 vrh->last_used_idx += vrh->completed;
480 static inline bool __vringh_notify_enable(struct vringh *vrh,
481 int (*getu16)(u16 *val, const u16 *p),
482 int (*putu16)(u16 *p, u16 val))
486 if (!vrh->event_indices) {
487 /* Old-school; update flags. */
488 if (putu16(&vrh->vring.used->flags, 0) != 0) {
489 vringh_bad("Clearing used flags %p",
490 &vrh->vring.used->flags);
494 if (putu16(&vring_avail_event(&vrh->vring),
495 vrh->last_avail_idx) != 0) {
496 vringh_bad("Updating avail event index %p",
497 &vring_avail_event(&vrh->vring));
502 /* They could have slipped one in as we were doing that: make
503 * sure it's written, then check again. */
504 virtio_mb(vrh->weak_barriers);
506 if (getu16(&avail, &vrh->vring.avail->idx) != 0) {
507 vringh_bad("Failed to check avail idx at %p",
508 &vrh->vring.avail->idx);
512 /* This is unlikely, so we just leave notifications enabled
513 * (if we're using event_indices, we'll only get one
514 * notification anyway). */
515 return avail == vrh->last_avail_idx;
518 static inline void __vringh_notify_disable(struct vringh *vrh,
519 int (*putu16)(u16 *p, u16 val))
521 if (!vrh->event_indices) {
522 /* Old-school; update flags. */
523 if (putu16(&vrh->vring.used->flags, VRING_USED_F_NO_NOTIFY)) {
524 vringh_bad("Setting used flags %p",
525 &vrh->vring.used->flags);
530 /* Userspace access helpers: in this case, addresses are really userspace. */
531 static inline int getu16_user(u16 *val, const u16 *p)
533 return get_user(*val, (__force u16 __user *)p);
536 static inline int putu16_user(u16 *p, u16 val)
538 return put_user(val, (__force u16 __user *)p);
541 static inline int copydesc_user(void *dst, const void *src, size_t len)
543 return copy_from_user(dst, (__force void __user *)src, len) ?
547 static inline int putused_user(struct vring_used_elem *dst,
548 const struct vring_used_elem *src,
551 return copy_to_user((__force void __user *)dst, src,
552 sizeof(*dst) * num) ? -EFAULT : 0;
555 static inline int xfer_from_user(void *src, void *dst, size_t len)
557 return copy_from_user(dst, (__force void __user *)src, len) ?
561 static inline int xfer_to_user(void *dst, void *src, size_t len)
563 return copy_to_user((__force void __user *)dst, src, len) ?
568 * vringh_init_user - initialize a vringh for a userspace vring.
569 * @vrh: the vringh to initialize.
570 * @features: the feature bits for this ring.
571 * @num: the number of elements.
572 * @weak_barriers: true if we only need memory barriers, not I/O.
573 * @desc: the userpace descriptor pointer.
574 * @avail: the userpace avail pointer.
575 * @used: the userpace used pointer.
577 * Returns an error if num is invalid: you should check pointers
580 int vringh_init_user(struct vringh *vrh, u32 features,
581 unsigned int num, bool weak_barriers,
582 struct vring_desc __user *desc,
583 struct vring_avail __user *avail,
584 struct vring_used __user *used)
586 /* Sane power of 2 please! */
587 if (!num || num > 0xffff || (num & (num - 1))) {
588 vringh_bad("Bad ring size %u", num);
592 vrh->event_indices = (features & (1 << VIRTIO_RING_F_EVENT_IDX));
593 vrh->weak_barriers = weak_barriers;
595 vrh->last_avail_idx = 0;
596 vrh->last_used_idx = 0;
597 vrh->vring.num = num;
598 /* vring expects kernel addresses, but only used via accessors. */
599 vrh->vring.desc = (__force struct vring_desc *)desc;
600 vrh->vring.avail = (__force struct vring_avail *)avail;
601 vrh->vring.used = (__force struct vring_used *)used;
604 EXPORT_SYMBOL(vringh_init_user);
607 * vringh_getdesc_user - get next available descriptor from userspace ring.
608 * @vrh: the userspace vring.
609 * @riov: where to put the readable descriptors (or NULL)
610 * @wiov: where to put the writable descriptors (or NULL)
611 * @getrange: function to call to check ranges.
612 * @head: head index we received, for passing to vringh_complete_user().
614 * Returns 0 if there was no descriptor, 1 if there was, or -errno.
616 * Note that on error return, you can tell the difference between an
617 * invalid ring and a single invalid descriptor: in the former case,
618 * *head will be vrh->vring.num. You may be able to ignore an invalid
619 * descriptor, but there's not much you can do with an invalid ring.
621 * Note that you may need to clean up riov and wiov, even on error!
623 int vringh_getdesc_user(struct vringh *vrh,
624 struct vringh_iov *riov,
625 struct vringh_iov *wiov,
626 bool (*getrange)(struct vringh *vrh,
627 u64 addr, struct vringh_range *r),
632 *head = vrh->vring.num;
633 err = __vringh_get_head(vrh, getu16_user, &vrh->last_avail_idx);
638 if (err == vrh->vring.num)
641 /* We need the layouts to be the identical for this to work */
642 BUILD_BUG_ON(sizeof(struct vringh_kiov) != sizeof(struct vringh_iov));
643 BUILD_BUG_ON(offsetof(struct vringh_kiov, iov) !=
644 offsetof(struct vringh_iov, iov));
645 BUILD_BUG_ON(offsetof(struct vringh_kiov, i) !=
646 offsetof(struct vringh_iov, i));
647 BUILD_BUG_ON(offsetof(struct vringh_kiov, used) !=
648 offsetof(struct vringh_iov, used));
649 BUILD_BUG_ON(offsetof(struct vringh_kiov, max_num) !=
650 offsetof(struct vringh_iov, max_num));
651 BUILD_BUG_ON(sizeof(struct iovec) != sizeof(struct kvec));
652 BUILD_BUG_ON(offsetof(struct iovec, iov_base) !=
653 offsetof(struct kvec, iov_base));
654 BUILD_BUG_ON(offsetof(struct iovec, iov_len) !=
655 offsetof(struct kvec, iov_len));
656 BUILD_BUG_ON(sizeof(((struct iovec *)NULL)->iov_base)
657 != sizeof(((struct kvec *)NULL)->iov_base));
658 BUILD_BUG_ON(sizeof(((struct iovec *)NULL)->iov_len)
659 != sizeof(((struct kvec *)NULL)->iov_len));
662 err = __vringh_iov(vrh, *head, (struct vringh_kiov *)riov,
663 (struct vringh_kiov *)wiov,
664 range_check, getrange, GFP_KERNEL, copydesc_user);
670 EXPORT_SYMBOL(vringh_getdesc_user);
673 * vringh_iov_pull_user - copy bytes from vring_iov.
674 * @riov: the riov as passed to vringh_getdesc_user() (updated as we consume)
675 * @dst: the place to copy.
676 * @len: the maximum length to copy.
678 * Returns the bytes copied <= len or a negative errno.
680 ssize_t vringh_iov_pull_user(struct vringh_iov *riov, void *dst, size_t len)
682 return vringh_iov_xfer((struct vringh_kiov *)riov,
683 dst, len, xfer_from_user);
685 EXPORT_SYMBOL(vringh_iov_pull_user);
688 * vringh_iov_push_user - copy bytes into vring_iov.
689 * @wiov: the wiov as passed to vringh_getdesc_user() (updated as we consume)
690 * @dst: the place to copy.
691 * @len: the maximum length to copy.
693 * Returns the bytes copied <= len or a negative errno.
695 ssize_t vringh_iov_push_user(struct vringh_iov *wiov,
696 const void *src, size_t len)
698 return vringh_iov_xfer((struct vringh_kiov *)wiov,
699 (void *)src, len, xfer_to_user);
701 EXPORT_SYMBOL(vringh_iov_push_user);
704 * vringh_abandon_user - we've decided not to handle the descriptor(s).
706 * @num: the number of descriptors to put back (ie. num
707 * vringh_get_user() to undo).
709 * The next vringh_get_user() will return the old descriptor(s) again.
711 void vringh_abandon_user(struct vringh *vrh, unsigned int num)
713 /* We only update vring_avail_event(vr) when we want to be notified,
714 * so we haven't changed that yet. */
715 vrh->last_avail_idx -= num;
717 EXPORT_SYMBOL(vringh_abandon_user);
720 * vringh_complete_user - we've finished with descriptor, publish it.
722 * @head: the head as filled in by vringh_getdesc_user.
723 * @len: the length of data we have written.
725 * You should check vringh_need_notify_user() after one or more calls
728 int vringh_complete_user(struct vringh *vrh, u16 head, u32 len)
730 struct vring_used_elem used;
734 return __vringh_complete(vrh, &used, 1, putu16_user, putused_user);
736 EXPORT_SYMBOL(vringh_complete_user);
739 * vringh_complete_multi_user - we've finished with many descriptors.
741 * @used: the head, length pairs.
742 * @num_used: the number of used elements.
744 * You should check vringh_need_notify_user() after one or more calls
747 int vringh_complete_multi_user(struct vringh *vrh,
748 const struct vring_used_elem used[],
751 return __vringh_complete(vrh, used, num_used,
752 putu16_user, putused_user);
754 EXPORT_SYMBOL(vringh_complete_multi_user);
757 * vringh_notify_enable_user - we want to know if something changes.
760 * This always enables notifications, but returns false if there are
761 * now more buffers available in the vring.
763 bool vringh_notify_enable_user(struct vringh *vrh)
765 return __vringh_notify_enable(vrh, getu16_user, putu16_user);
767 EXPORT_SYMBOL(vringh_notify_enable_user);
770 * vringh_notify_disable_user - don't tell us if something changes.
773 * This is our normal running state: we disable and then only enable when
774 * we're going to sleep.
776 void vringh_notify_disable_user(struct vringh *vrh)
778 __vringh_notify_disable(vrh, putu16_user);
780 EXPORT_SYMBOL(vringh_notify_disable_user);
783 * vringh_need_notify_user - must we tell the other side about used buffers?
784 * @vrh: the vring we've called vringh_complete_user() on.
786 * Returns -errno or 0 if we don't need to tell the other side, 1 if we do.
788 int vringh_need_notify_user(struct vringh *vrh)
790 return __vringh_need_notify(vrh, getu16_user);
792 EXPORT_SYMBOL(vringh_need_notify_user);
794 /* Kernelspace access helpers. */
795 static inline int getu16_kern(u16 *val, const u16 *p)
797 *val = ACCESS_ONCE(*p);
801 static inline int putu16_kern(u16 *p, u16 val)
803 ACCESS_ONCE(*p) = val;
807 static inline int copydesc_kern(void *dst, const void *src, size_t len)
809 memcpy(dst, src, len);
813 static inline int putused_kern(struct vring_used_elem *dst,
814 const struct vring_used_elem *src,
817 memcpy(dst, src, num * sizeof(*dst));
821 static inline int xfer_kern(void *src, void *dst, size_t len)
823 memcpy(dst, src, len);
828 * vringh_init_kern - initialize a vringh for a kernelspace vring.
829 * @vrh: the vringh to initialize.
830 * @features: the feature bits for this ring.
831 * @num: the number of elements.
832 * @weak_barriers: true if we only need memory barriers, not I/O.
833 * @desc: the userpace descriptor pointer.
834 * @avail: the userpace avail pointer.
835 * @used: the userpace used pointer.
837 * Returns an error if num is invalid.
839 int vringh_init_kern(struct vringh *vrh, u32 features,
840 unsigned int num, bool weak_barriers,
841 struct vring_desc *desc,
842 struct vring_avail *avail,
843 struct vring_used *used)
845 /* Sane power of 2 please! */
846 if (!num || num > 0xffff || (num & (num - 1))) {
847 vringh_bad("Bad ring size %u", num);
851 vrh->event_indices = (features & (1 << VIRTIO_RING_F_EVENT_IDX));
852 vrh->weak_barriers = weak_barriers;
854 vrh->last_avail_idx = 0;
855 vrh->last_used_idx = 0;
856 vrh->vring.num = num;
857 vrh->vring.desc = desc;
858 vrh->vring.avail = avail;
859 vrh->vring.used = used;
862 EXPORT_SYMBOL(vringh_init_kern);
865 * vringh_getdesc_kern - get next available descriptor from kernelspace ring.
866 * @vrh: the kernelspace vring.
867 * @riov: where to put the readable descriptors (or NULL)
868 * @wiov: where to put the writable descriptors (or NULL)
869 * @head: head index we received, for passing to vringh_complete_kern().
870 * @gfp: flags for allocating larger riov/wiov.
872 * Returns 0 if there was no descriptor, 1 if there was, or -errno.
874 * Note that on error return, you can tell the difference between an
875 * invalid ring and a single invalid descriptor: in the former case,
876 * *head will be vrh->vring.num. You may be able to ignore an invalid
877 * descriptor, but there's not much you can do with an invalid ring.
879 * Note that you may need to clean up riov and wiov, even on error!
881 int vringh_getdesc_kern(struct vringh *vrh,
882 struct vringh_kiov *riov,
883 struct vringh_kiov *wiov,
889 err = __vringh_get_head(vrh, getu16_kern, &vrh->last_avail_idx);
894 if (err == vrh->vring.num)
898 err = __vringh_iov(vrh, *head, riov, wiov, no_range_check, NULL,
905 EXPORT_SYMBOL(vringh_getdesc_kern);
908 * vringh_iov_pull_kern - copy bytes from vring_iov.
909 * @riov: the riov as passed to vringh_getdesc_kern() (updated as we consume)
910 * @dst: the place to copy.
911 * @len: the maximum length to copy.
913 * Returns the bytes copied <= len or a negative errno.
915 ssize_t vringh_iov_pull_kern(struct vringh_kiov *riov, void *dst, size_t len)
917 return vringh_iov_xfer(riov, dst, len, xfer_kern);
919 EXPORT_SYMBOL(vringh_iov_pull_kern);
922 * vringh_iov_push_kern - copy bytes into vring_iov.
923 * @wiov: the wiov as passed to vringh_getdesc_kern() (updated as we consume)
924 * @dst: the place to copy.
925 * @len: the maximum length to copy.
927 * Returns the bytes copied <= len or a negative errno.
929 ssize_t vringh_iov_push_kern(struct vringh_kiov *wiov,
930 const void *src, size_t len)
932 return vringh_iov_xfer(wiov, (void *)src, len, xfer_kern);
934 EXPORT_SYMBOL(vringh_iov_push_kern);
937 * vringh_abandon_kern - we've decided not to handle the descriptor(s).
939 * @num: the number of descriptors to put back (ie. num
940 * vringh_get_kern() to undo).
942 * The next vringh_get_kern() will return the old descriptor(s) again.
944 void vringh_abandon_kern(struct vringh *vrh, unsigned int num)
946 /* We only update vring_avail_event(vr) when we want to be notified,
947 * so we haven't changed that yet. */
948 vrh->last_avail_idx -= num;
950 EXPORT_SYMBOL(vringh_abandon_kern);
953 * vringh_complete_kern - we've finished with descriptor, publish it.
955 * @head: the head as filled in by vringh_getdesc_kern.
956 * @len: the length of data we have written.
958 * You should check vringh_need_notify_kern() after one or more calls
961 int vringh_complete_kern(struct vringh *vrh, u16 head, u32 len)
963 struct vring_used_elem used;
968 return __vringh_complete(vrh, &used, 1, putu16_kern, putused_kern);
970 EXPORT_SYMBOL(vringh_complete_kern);
973 * vringh_notify_enable_kern - we want to know if something changes.
976 * This always enables notifications, but returns false if there are
977 * now more buffers available in the vring.
979 bool vringh_notify_enable_kern(struct vringh *vrh)
981 return __vringh_notify_enable(vrh, getu16_kern, putu16_kern);
983 EXPORT_SYMBOL(vringh_notify_enable_kern);
986 * vringh_notify_disable_kern - don't tell us if something changes.
989 * This is our normal running state: we disable and then only enable when
990 * we're going to sleep.
992 void vringh_notify_disable_kern(struct vringh *vrh)
994 __vringh_notify_disable(vrh, putu16_kern);
996 EXPORT_SYMBOL(vringh_notify_disable_kern);
999 * vringh_need_notify_kern - must we tell the other side about used buffers?
1000 * @vrh: the vring we've called vringh_complete_kern() on.
1002 * Returns -errno or 0 if we don't need to tell the other side, 1 if we do.
1004 int vringh_need_notify_kern(struct vringh *vrh)
1006 return __vringh_need_notify(vrh, getu16_kern);
1008 EXPORT_SYMBOL(vringh_need_notify_kern);
1010 MODULE_LICENSE("GPL");