2 * Helpers for the host side of a virtio ring.
4 * Since these may be in userspace, we use (inline) accessors.
6 #include <linux/vringh.h>
7 #include <linux/virtio_ring.h>
8 #include <linux/kernel.h>
9 #include <linux/ratelimit.h>
10 #include <linux/uaccess.h>
11 #include <linux/slab.h>
12 #include <linux/export.h>
14 static __printf(1,2) __cold void vringh_bad(const char *fmt, ...)
16 static DEFINE_RATELIMIT_STATE(vringh_rs,
17 DEFAULT_RATELIMIT_INTERVAL,
18 DEFAULT_RATELIMIT_BURST);
19 if (__ratelimit(&vringh_rs)) {
22 printk(KERN_NOTICE "vringh:");
28 /* Returns vring->num if empty, -ve on error. */
29 static inline int __vringh_get_head(const struct vringh *vrh,
30 int (*getu16)(u16 *val, const u16 *p),
33 u16 avail_idx, i, head;
36 err = getu16(&avail_idx, &vrh->vring.avail->idx);
38 vringh_bad("Failed to access avail idx at %p",
39 &vrh->vring.avail->idx);
43 if (*last_avail_idx == avail_idx)
44 return vrh->vring.num;
46 /* Only get avail ring entries after they have been exposed by guest. */
47 virtio_rmb(vrh->weak_barriers);
49 i = *last_avail_idx & (vrh->vring.num - 1);
51 err = getu16(&head, &vrh->vring.avail->ring[i]);
53 vringh_bad("Failed to read head: idx %d address %p",
54 *last_avail_idx, &vrh->vring.avail->ring[i]);
58 if (head >= vrh->vring.num) {
59 vringh_bad("Guest says index %u > %u is available",
60 head, vrh->vring.num);
68 /* Copy some bytes to/from the iovec. Returns num copied. */
69 static inline ssize_t vringh_iov_xfer(struct vringh_kiov *iov,
70 void *ptr, size_t len,
71 int (*xfer)(void *addr, void *ptr,
76 while (len && iov->i < iov->used) {
79 partlen = min(iov->iov[iov->i].iov_len, len);
80 err = xfer(iov->iov[iov->i].iov_base, ptr, partlen);
86 iov->consumed += partlen;
87 iov->iov[iov->i].iov_len -= partlen;
88 iov->iov[iov->i].iov_base += partlen;
90 if (!iov->iov[iov->i].iov_len) {
91 /* Fix up old iov element then increment. */
92 iov->iov[iov->i].iov_len = iov->consumed;
93 iov->iov[iov->i].iov_base -= iov->consumed;
102 /* May reduce *len if range is shorter. */
103 static inline bool range_check(struct vringh *vrh, u64 addr, size_t *len,
104 struct vringh_range *range,
105 bool (*getrange)(struct vringh *,
106 u64, struct vringh_range *))
108 if (addr < range->start || addr > range->end_incl) {
109 if (!getrange(vrh, addr, range))
112 BUG_ON(addr < range->start || addr > range->end_incl);
114 /* To end of memory? */
115 if (unlikely(addr + *len == 0)) {
116 if (range->end_incl == -1ULL)
121 /* Otherwise, don't wrap. */
122 if (addr + *len < addr) {
123 vringh_bad("Wrapping descriptor %zu@0x%llx",
124 *len, (unsigned long long)addr);
128 if (unlikely(addr + *len - 1 > range->end_incl))
133 *len = range->end_incl + 1 - addr;
137 static inline bool no_range_check(struct vringh *vrh, u64 addr, size_t *len,
138 struct vringh_range *range,
139 bool (*getrange)(struct vringh *,
140 u64, struct vringh_range *))
145 /* No reason for this code to be inline. */
146 static int move_to_indirect(int *up_next, u16 *i, void *addr,
147 const struct vring_desc *desc,
148 struct vring_desc **descs, int *desc_max)
150 /* Indirect tables can't have indirect. */
151 if (*up_next != -1) {
152 vringh_bad("Multilevel indirect %u->%u", *up_next, *i);
156 if (unlikely(desc->len % sizeof(struct vring_desc))) {
157 vringh_bad("Strange indirect len %u", desc->len);
161 /* We will check this when we follow it! */
162 if (desc->flags & VRING_DESC_F_NEXT)
163 *up_next = desc->next;
167 *desc_max = desc->len / sizeof(struct vring_desc);
169 /* Now, start at the first indirect. */
174 static int resize_iovec(struct vringh_kiov *iov, gfp_t gfp)
177 unsigned int flag, new_num = (iov->max_num & ~VRINGH_IOV_ALLOCATED) * 2;
182 flag = (iov->max_num & VRINGH_IOV_ALLOCATED);
184 new = krealloc(iov->iov, new_num * sizeof(struct iovec), gfp);
186 new = kmalloc(new_num * sizeof(struct iovec), gfp);
188 memcpy(new, iov->iov,
189 iov->max_num * sizeof(struct iovec));
190 flag = VRINGH_IOV_ALLOCATED;
196 iov->max_num = (new_num | flag);
200 static u16 __cold return_from_indirect(const struct vringh *vrh, int *up_next,
201 struct vring_desc **descs, int *desc_max)
206 *descs = vrh->vring.desc;
207 *desc_max = vrh->vring.num;
211 static int slow_copy(struct vringh *vrh, void *dst, const void *src,
212 bool (*rcheck)(struct vringh *vrh, u64 addr, size_t *len,
213 struct vringh_range *range,
214 bool (*getrange)(struct vringh *vrh,
216 struct vringh_range *)),
217 bool (*getrange)(struct vringh *vrh,
219 struct vringh_range *r),
220 struct vringh_range *range,
221 int (*copy)(void *dst, const void *src, size_t len))
223 size_t part, len = sizeof(struct vring_desc);
230 addr = (u64)(unsigned long)src - range->offset;
232 if (!rcheck(vrh, addr, &part, range, getrange))
235 err = copy(dst, src, part);
247 __vringh_iov(struct vringh *vrh, u16 i,
248 struct vringh_kiov *riov,
249 struct vringh_kiov *wiov,
250 bool (*rcheck)(struct vringh *vrh, u64 addr, size_t *len,
251 struct vringh_range *range,
252 bool (*getrange)(struct vringh *, u64,
253 struct vringh_range *)),
254 bool (*getrange)(struct vringh *, u64, struct vringh_range *),
256 int (*copy)(void *dst, const void *src, size_t len))
258 int err, count = 0, up_next, desc_max;
259 struct vring_desc desc, *descs;
260 struct vringh_range range = { -1ULL, 0 }, slowrange;
263 /* We start traversing vring's descriptor table. */
264 descs = vrh->vring.desc;
265 desc_max = vrh->vring.num;
269 riov->i = riov->used = 0;
271 wiov->i = wiov->used = 0;
273 /* You must want something! */
278 struct vringh_kiov *iov;
282 err = slow_copy(vrh, &desc, &descs[i], rcheck, getrange,
285 err = copy(&desc, &descs[i], sizeof(desc));
289 if (unlikely(desc.flags & VRING_DESC_F_INDIRECT)) {
290 /* Make sure it's OK, and get offset. */
292 if (!rcheck(vrh, desc.addr, &len, &range, getrange)) {
297 if (unlikely(len != desc.len)) {
299 /* We need to save this range to use offset */
303 addr = (void *)(long)(desc.addr + range.offset);
304 err = move_to_indirect(&up_next, &i, addr, &desc,
311 if (count++ == vrh->vring.num) {
312 vringh_bad("Descriptor loop in %p", descs);
317 if (desc.flags & VRING_DESC_F_WRITE)
321 if (unlikely(wiov && wiov->i)) {
322 vringh_bad("Readable desc %p after writable",
330 vringh_bad("Unexpected %s desc",
331 !wiov ? "writable" : "readable");
337 /* Make sure it's OK, and get offset. */
339 if (!rcheck(vrh, desc.addr, &len, &range, getrange)) {
343 addr = (void *)(unsigned long)(desc.addr + range.offset);
345 if (unlikely(iov->used == (iov->max_num & ~VRINGH_IOV_ALLOCATED))) {
346 err = resize_iovec(iov, gfp);
351 iov->iov[iov->used].iov_base = addr;
352 iov->iov[iov->used].iov_len = len;
355 if (unlikely(len != desc.len)) {
361 if (desc.flags & VRING_DESC_F_NEXT) {
364 /* Just in case we need to finish traversing above. */
365 if (unlikely(up_next > 0)) {
366 i = return_from_indirect(vrh, &up_next,
374 vringh_bad("Chained index %u > %u", i, desc_max);
386 static inline int __vringh_complete(struct vringh *vrh,
387 const struct vring_used_elem *used,
388 unsigned int num_used,
389 int (*putu16)(u16 *p, u16 val),
390 int (*putused)(struct vring_used_elem *dst,
391 const struct vring_used_elem
394 struct vring_used *used_ring;
398 used_ring = vrh->vring.used;
399 used_idx = vrh->last_used_idx + vrh->completed;
401 off = used_idx % vrh->vring.num;
403 /* Compiler knows num_used == 1 sometimes, hence extra check */
404 if (num_used > 1 && unlikely(off + num_used >= vrh->vring.num)) {
405 u16 part = vrh->vring.num - off;
406 err = putused(&used_ring->ring[off], used, part);
408 err = putused(&used_ring->ring[0], used + part,
411 err = putused(&used_ring->ring[off], used, num_used);
414 vringh_bad("Failed to write %u used entries %u at %p",
415 num_used, off, &used_ring->ring[off]);
419 /* Make sure buffer is written before we update index. */
420 virtio_wmb(vrh->weak_barriers);
422 err = putu16(&vrh->vring.used->idx, used_idx + num_used);
424 vringh_bad("Failed to update used index at %p",
425 &vrh->vring.used->idx);
429 vrh->completed += num_used;
434 static inline int __vringh_need_notify(struct vringh *vrh,
435 int (*getu16)(u16 *val, const u16 *p))
441 /* Flush out used index update. This is paired with the
442 * barrier that the Guest executes when enabling
444 virtio_mb(vrh->weak_barriers);
446 /* Old-style, without event indices. */
447 if (!vrh->event_indices) {
449 err = getu16(&flags, &vrh->vring.avail->flags);
451 vringh_bad("Failed to get flags at %p",
452 &vrh->vring.avail->flags);
455 return (!(flags & VRING_AVAIL_F_NO_INTERRUPT));
458 /* Modern: we know when other side wants to know. */
459 err = getu16(&used_event, &vring_used_event(&vrh->vring));
461 vringh_bad("Failed to get used event idx at %p",
462 &vring_used_event(&vrh->vring));
466 /* Just in case we added so many that we wrap. */
467 if (unlikely(vrh->completed > 0xffff))
470 notify = vring_need_event(used_event,
471 vrh->last_used_idx + vrh->completed,
474 vrh->last_used_idx += vrh->completed;
479 static inline bool __vringh_notify_enable(struct vringh *vrh,
480 int (*getu16)(u16 *val, const u16 *p),
481 int (*putu16)(u16 *p, u16 val))
485 if (!vrh->event_indices) {
486 /* Old-school; update flags. */
487 if (putu16(&vrh->vring.used->flags, 0) != 0) {
488 vringh_bad("Clearing used flags %p",
489 &vrh->vring.used->flags);
493 if (putu16(&vring_avail_event(&vrh->vring),
494 vrh->last_avail_idx) != 0) {
495 vringh_bad("Updating avail event index %p",
496 &vring_avail_event(&vrh->vring));
501 /* They could have slipped one in as we were doing that: make
502 * sure it's written, then check again. */
503 virtio_mb(vrh->weak_barriers);
505 if (getu16(&avail, &vrh->vring.avail->idx) != 0) {
506 vringh_bad("Failed to check avail idx at %p",
507 &vrh->vring.avail->idx);
511 /* This is unlikely, so we just leave notifications enabled
512 * (if we're using event_indices, we'll only get one
513 * notification anyway). */
514 return avail == vrh->last_avail_idx;
517 static inline void __vringh_notify_disable(struct vringh *vrh,
518 int (*putu16)(u16 *p, u16 val))
520 if (!vrh->event_indices) {
521 /* Old-school; update flags. */
522 if (putu16(&vrh->vring.used->flags, VRING_USED_F_NO_NOTIFY)) {
523 vringh_bad("Setting used flags %p",
524 &vrh->vring.used->flags);
529 /* Userspace access helpers: in this case, addresses are really userspace. */
530 static inline int getu16_user(u16 *val, const u16 *p)
532 return get_user(*val, (__force u16 __user *)p);
535 static inline int putu16_user(u16 *p, u16 val)
537 return put_user(val, (__force u16 __user *)p);
540 static inline int copydesc_user(void *dst, const void *src, size_t len)
542 return copy_from_user(dst, (__force void __user *)src, len) ?
546 static inline int putused_user(struct vring_used_elem *dst,
547 const struct vring_used_elem *src,
550 return copy_to_user((__force void __user *)dst, src,
551 sizeof(*dst) * num) ? -EFAULT : 0;
554 static inline int xfer_from_user(void *src, void *dst, size_t len)
556 return copy_from_user(dst, (__force void __user *)src, len) ?
560 static inline int xfer_to_user(void *dst, void *src, size_t len)
562 return copy_to_user((__force void __user *)dst, src, len) ?
567 * vringh_init_user - initialize a vringh for a userspace vring.
568 * @vrh: the vringh to initialize.
569 * @features: the feature bits for this ring.
570 * @num: the number of elements.
571 * @weak_barriers: true if we only need memory barriers, not I/O.
572 * @desc: the userpace descriptor pointer.
573 * @avail: the userpace avail pointer.
574 * @used: the userpace used pointer.
576 * Returns an error if num is invalid: you should check pointers
579 int vringh_init_user(struct vringh *vrh, u32 features,
580 unsigned int num, bool weak_barriers,
581 struct vring_desc __user *desc,
582 struct vring_avail __user *avail,
583 struct vring_used __user *used)
585 /* Sane power of 2 please! */
586 if (!num || num > 0xffff || (num & (num - 1))) {
587 vringh_bad("Bad ring size %u", num);
591 vrh->event_indices = (features & (1 << VIRTIO_RING_F_EVENT_IDX));
592 vrh->weak_barriers = weak_barriers;
594 vrh->last_avail_idx = 0;
595 vrh->last_used_idx = 0;
596 vrh->vring.num = num;
597 /* vring expects kernel addresses, but only used via accessors. */
598 vrh->vring.desc = (__force struct vring_desc *)desc;
599 vrh->vring.avail = (__force struct vring_avail *)avail;
600 vrh->vring.used = (__force struct vring_used *)used;
603 EXPORT_SYMBOL(vringh_init_user);
606 * vringh_getdesc_user - get next available descriptor from userspace ring.
607 * @vrh: the userspace vring.
608 * @riov: where to put the readable descriptors (or NULL)
609 * @wiov: where to put the writable descriptors (or NULL)
610 * @getrange: function to call to check ranges.
611 * @head: head index we received, for passing to vringh_complete_user().
613 * Returns 0 if there was no descriptor, 1 if there was, or -errno.
615 * Note that on error return, you can tell the difference between an
616 * invalid ring and a single invalid descriptor: in the former case,
617 * *head will be vrh->vring.num. You may be able to ignore an invalid
618 * descriptor, but there's not much you can do with an invalid ring.
620 * Note that you may need to clean up riov and wiov, even on error!
622 int vringh_getdesc_user(struct vringh *vrh,
623 struct vringh_iov *riov,
624 struct vringh_iov *wiov,
625 bool (*getrange)(struct vringh *vrh,
626 u64 addr, struct vringh_range *r),
631 *head = vrh->vring.num;
632 err = __vringh_get_head(vrh, getu16_user, &vrh->last_avail_idx);
637 if (err == vrh->vring.num)
640 /* We need the layouts to be the identical for this to work */
641 BUILD_BUG_ON(sizeof(struct vringh_kiov) != sizeof(struct vringh_iov));
642 BUILD_BUG_ON(offsetof(struct vringh_kiov, iov) !=
643 offsetof(struct vringh_iov, iov));
644 BUILD_BUG_ON(offsetof(struct vringh_kiov, i) !=
645 offsetof(struct vringh_iov, i));
646 BUILD_BUG_ON(offsetof(struct vringh_kiov, used) !=
647 offsetof(struct vringh_iov, used));
648 BUILD_BUG_ON(offsetof(struct vringh_kiov, max_num) !=
649 offsetof(struct vringh_iov, max_num));
650 BUILD_BUG_ON(sizeof(struct iovec) != sizeof(struct kvec));
651 BUILD_BUG_ON(offsetof(struct iovec, iov_base) !=
652 offsetof(struct kvec, iov_base));
653 BUILD_BUG_ON(offsetof(struct iovec, iov_len) !=
654 offsetof(struct kvec, iov_len));
655 BUILD_BUG_ON(sizeof(((struct iovec *)NULL)->iov_base)
656 != sizeof(((struct kvec *)NULL)->iov_base));
657 BUILD_BUG_ON(sizeof(((struct iovec *)NULL)->iov_len)
658 != sizeof(((struct kvec *)NULL)->iov_len));
661 err = __vringh_iov(vrh, *head, (struct vringh_kiov *)riov,
662 (struct vringh_kiov *)wiov,
663 range_check, getrange, GFP_KERNEL, copydesc_user);
669 EXPORT_SYMBOL(vringh_getdesc_user);
672 * vringh_iov_pull_user - copy bytes from vring_iov.
673 * @riov: the riov as passed to vringh_getdesc_user() (updated as we consume)
674 * @dst: the place to copy.
675 * @len: the maximum length to copy.
677 * Returns the bytes copied <= len or a negative errno.
679 ssize_t vringh_iov_pull_user(struct vringh_iov *riov, void *dst, size_t len)
681 return vringh_iov_xfer((struct vringh_kiov *)riov,
682 dst, len, xfer_from_user);
684 EXPORT_SYMBOL(vringh_iov_pull_user);
687 * vringh_iov_push_user - copy bytes into vring_iov.
688 * @wiov: the wiov as passed to vringh_getdesc_user() (updated as we consume)
689 * @dst: the place to copy.
690 * @len: the maximum length to copy.
692 * Returns the bytes copied <= len or a negative errno.
694 ssize_t vringh_iov_push_user(struct vringh_iov *wiov,
695 const void *src, size_t len)
697 return vringh_iov_xfer((struct vringh_kiov *)wiov,
698 (void *)src, len, xfer_to_user);
700 EXPORT_SYMBOL(vringh_iov_push_user);
703 * vringh_abandon_user - we've decided not to handle the descriptor(s).
705 * @num: the number of descriptors to put back (ie. num
706 * vringh_get_user() to undo).
708 * The next vringh_get_user() will return the old descriptor(s) again.
710 void vringh_abandon_user(struct vringh *vrh, unsigned int num)
712 /* We only update vring_avail_event(vr) when we want to be notified,
713 * so we haven't changed that yet. */
714 vrh->last_avail_idx -= num;
716 EXPORT_SYMBOL(vringh_abandon_user);
719 * vringh_complete_user - we've finished with descriptor, publish it.
721 * @head: the head as filled in by vringh_getdesc_user.
722 * @len: the length of data we have written.
724 * You should check vringh_need_notify_user() after one or more calls
727 int vringh_complete_user(struct vringh *vrh, u16 head, u32 len)
729 struct vring_used_elem used;
733 return __vringh_complete(vrh, &used, 1, putu16_user, putused_user);
735 EXPORT_SYMBOL(vringh_complete_user);
738 * vringh_complete_multi_user - we've finished with many descriptors.
740 * @used: the head, length pairs.
741 * @num_used: the number of used elements.
743 * You should check vringh_need_notify_user() after one or more calls
746 int vringh_complete_multi_user(struct vringh *vrh,
747 const struct vring_used_elem used[],
750 return __vringh_complete(vrh, used, num_used,
751 putu16_user, putused_user);
753 EXPORT_SYMBOL(vringh_complete_multi_user);
756 * vringh_notify_enable_user - we want to know if something changes.
759 * This always enables notifications, but returns false if there are
760 * now more buffers available in the vring.
762 bool vringh_notify_enable_user(struct vringh *vrh)
764 return __vringh_notify_enable(vrh, getu16_user, putu16_user);
766 EXPORT_SYMBOL(vringh_notify_enable_user);
769 * vringh_notify_disable_user - don't tell us if something changes.
772 * This is our normal running state: we disable and then only enable when
773 * we're going to sleep.
775 void vringh_notify_disable_user(struct vringh *vrh)
777 __vringh_notify_disable(vrh, putu16_user);
779 EXPORT_SYMBOL(vringh_notify_disable_user);
782 * vringh_need_notify_user - must we tell the other side about used buffers?
783 * @vrh: the vring we've called vringh_complete_user() on.
785 * Returns -errno or 0 if we don't need to tell the other side, 1 if we do.
787 int vringh_need_notify_user(struct vringh *vrh)
789 return __vringh_need_notify(vrh, getu16_user);
791 EXPORT_SYMBOL(vringh_need_notify_user);
793 /* Kernelspace access helpers. */
794 static inline int getu16_kern(u16 *val, const u16 *p)
796 *val = ACCESS_ONCE(*p);
800 static inline int putu16_kern(u16 *p, u16 val)
802 ACCESS_ONCE(*p) = val;
806 static inline int copydesc_kern(void *dst, const void *src, size_t len)
808 memcpy(dst, src, len);
812 static inline int putused_kern(struct vring_used_elem *dst,
813 const struct vring_used_elem *src,
816 memcpy(dst, src, num * sizeof(*dst));
820 static inline int xfer_kern(void *src, void *dst, size_t len)
822 memcpy(dst, src, len);
827 * vringh_init_kern - initialize a vringh for a kernelspace vring.
828 * @vrh: the vringh to initialize.
829 * @features: the feature bits for this ring.
830 * @num: the number of elements.
831 * @weak_barriers: true if we only need memory barriers, not I/O.
832 * @desc: the userpace descriptor pointer.
833 * @avail: the userpace avail pointer.
834 * @used: the userpace used pointer.
836 * Returns an error if num is invalid.
838 int vringh_init_kern(struct vringh *vrh, u32 features,
839 unsigned int num, bool weak_barriers,
840 struct vring_desc *desc,
841 struct vring_avail *avail,
842 struct vring_used *used)
844 /* Sane power of 2 please! */
845 if (!num || num > 0xffff || (num & (num - 1))) {
846 vringh_bad("Bad ring size %u", num);
850 vrh->event_indices = (features & (1 << VIRTIO_RING_F_EVENT_IDX));
851 vrh->weak_barriers = weak_barriers;
853 vrh->last_avail_idx = 0;
854 vrh->last_used_idx = 0;
855 vrh->vring.num = num;
856 vrh->vring.desc = desc;
857 vrh->vring.avail = avail;
858 vrh->vring.used = used;
861 EXPORT_SYMBOL(vringh_init_kern);
864 * vringh_getdesc_kern - get next available descriptor from kernelspace ring.
865 * @vrh: the kernelspace vring.
866 * @riov: where to put the readable descriptors (or NULL)
867 * @wiov: where to put the writable descriptors (or NULL)
868 * @head: head index we received, for passing to vringh_complete_kern().
869 * @gfp: flags for allocating larger riov/wiov.
871 * Returns 0 if there was no descriptor, 1 if there was, or -errno.
873 * Note that on error return, you can tell the difference between an
874 * invalid ring and a single invalid descriptor: in the former case,
875 * *head will be vrh->vring.num. You may be able to ignore an invalid
876 * descriptor, but there's not much you can do with an invalid ring.
878 * Note that you may need to clean up riov and wiov, even on error!
880 int vringh_getdesc_kern(struct vringh *vrh,
881 struct vringh_kiov *riov,
882 struct vringh_kiov *wiov,
888 err = __vringh_get_head(vrh, getu16_kern, &vrh->last_avail_idx);
893 if (err == vrh->vring.num)
897 err = __vringh_iov(vrh, *head, riov, wiov, no_range_check, NULL,
904 EXPORT_SYMBOL(vringh_getdesc_kern);
907 * vringh_iov_pull_kern - copy bytes from vring_iov.
908 * @riov: the riov as passed to vringh_getdesc_kern() (updated as we consume)
909 * @dst: the place to copy.
910 * @len: the maximum length to copy.
912 * Returns the bytes copied <= len or a negative errno.
914 ssize_t vringh_iov_pull_kern(struct vringh_kiov *riov, void *dst, size_t len)
916 return vringh_iov_xfer(riov, dst, len, xfer_kern);
918 EXPORT_SYMBOL(vringh_iov_pull_kern);
921 * vringh_iov_push_kern - copy bytes into vring_iov.
922 * @wiov: the wiov as passed to vringh_getdesc_kern() (updated as we consume)
923 * @dst: the place to copy.
924 * @len: the maximum length to copy.
926 * Returns the bytes copied <= len or a negative errno.
928 ssize_t vringh_iov_push_kern(struct vringh_kiov *wiov,
929 const void *src, size_t len)
931 return vringh_iov_xfer(wiov, (void *)src, len, xfer_kern);
933 EXPORT_SYMBOL(vringh_iov_push_kern);
936 * vringh_abandon_kern - we've decided not to handle the descriptor(s).
938 * @num: the number of descriptors to put back (ie. num
939 * vringh_get_kern() to undo).
941 * The next vringh_get_kern() will return the old descriptor(s) again.
943 void vringh_abandon_kern(struct vringh *vrh, unsigned int num)
945 /* We only update vring_avail_event(vr) when we want to be notified,
946 * so we haven't changed that yet. */
947 vrh->last_avail_idx -= num;
949 EXPORT_SYMBOL(vringh_abandon_kern);
952 * vringh_complete_kern - we've finished with descriptor, publish it.
954 * @head: the head as filled in by vringh_getdesc_kern.
955 * @len: the length of data we have written.
957 * You should check vringh_need_notify_kern() after one or more calls
960 int vringh_complete_kern(struct vringh *vrh, u16 head, u32 len)
962 struct vring_used_elem used;
967 return __vringh_complete(vrh, &used, 1, putu16_kern, putused_kern);
969 EXPORT_SYMBOL(vringh_complete_kern);
972 * vringh_notify_enable_kern - we want to know if something changes.
975 * This always enables notifications, but returns false if there are
976 * now more buffers available in the vring.
978 bool vringh_notify_enable_kern(struct vringh *vrh)
980 return __vringh_notify_enable(vrh, getu16_kern, putu16_kern);
982 EXPORT_SYMBOL(vringh_notify_enable_kern);
985 * vringh_notify_disable_kern - don't tell us if something changes.
988 * This is our normal running state: we disable and then only enable when
989 * we're going to sleep.
991 void vringh_notify_disable_kern(struct vringh *vrh)
993 __vringh_notify_disable(vrh, putu16_kern);
995 EXPORT_SYMBOL(vringh_notify_disable_kern);
998 * vringh_need_notify_kern - must we tell the other side about used buffers?
999 * @vrh: the vring we've called vringh_complete_kern() on.
1001 * Returns -errno or 0 if we don't need to tell the other side, 1 if we do.
1003 int vringh_need_notify_kern(struct vringh *vrh)
1005 return __vringh_need_notify(vrh, getu16_kern);
1007 EXPORT_SYMBOL(vringh_need_notify_kern);