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>
14 #include <uapi/linux/virtio_config.h>
16 static __printf(1,2) __cold void vringh_bad(const char *fmt, ...)
18 static DEFINE_RATELIMIT_STATE(vringh_rs,
19 DEFAULT_RATELIMIT_INTERVAL,
20 DEFAULT_RATELIMIT_BURST);
21 if (__ratelimit(&vringh_rs)) {
24 printk(KERN_NOTICE "vringh:");
30 /* Returns vring->num if empty, -ve on error. */
31 static inline int __vringh_get_head(const struct vringh *vrh,
32 int (*getu16)(const struct vringh *vrh,
33 u16 *val, const __virtio16 *p),
36 u16 avail_idx, i, head;
39 err = getu16(vrh, &avail_idx, &vrh->vring.avail->idx);
41 vringh_bad("Failed to access avail idx at %p",
42 &vrh->vring.avail->idx);
46 if (*last_avail_idx == avail_idx)
47 return vrh->vring.num;
49 /* Only get avail ring entries after they have been exposed by guest. */
50 virtio_rmb(vrh->weak_barriers);
52 i = *last_avail_idx & (vrh->vring.num - 1);
54 err = getu16(vrh, &head, &vrh->vring.avail->ring[i]);
56 vringh_bad("Failed to read head: idx %d address %p",
57 *last_avail_idx, &vrh->vring.avail->ring[i]);
61 if (head >= vrh->vring.num) {
62 vringh_bad("Guest says index %u > %u is available",
63 head, vrh->vring.num);
71 /* Copy some bytes to/from the iovec. Returns num copied. */
72 static inline ssize_t vringh_iov_xfer(struct vringh_kiov *iov,
73 void *ptr, size_t len,
74 int (*xfer)(void *addr, void *ptr,
79 while (len && iov->i < iov->used) {
82 partlen = min(iov->iov[iov->i].iov_len, len);
83 err = xfer(iov->iov[iov->i].iov_base, ptr, partlen);
89 iov->consumed += partlen;
90 iov->iov[iov->i].iov_len -= partlen;
91 iov->iov[iov->i].iov_base += partlen;
93 if (!iov->iov[iov->i].iov_len) {
94 /* Fix up old iov element then increment. */
95 iov->iov[iov->i].iov_len = iov->consumed;
96 iov->iov[iov->i].iov_base -= iov->consumed;
105 /* May reduce *len if range is shorter. */
106 static inline bool range_check(struct vringh *vrh, u64 addr, size_t *len,
107 struct vringh_range *range,
108 bool (*getrange)(struct vringh *,
109 u64, struct vringh_range *))
111 if (addr < range->start || addr > range->end_incl) {
112 if (!getrange(vrh, addr, range))
115 BUG_ON(addr < range->start || addr > range->end_incl);
117 /* To end of memory? */
118 if (unlikely(addr + *len == 0)) {
119 if (range->end_incl == -1ULL)
124 /* Otherwise, don't wrap. */
125 if (addr + *len < addr) {
126 vringh_bad("Wrapping descriptor %zu@0x%llx",
127 *len, (unsigned long long)addr);
131 if (unlikely(addr + *len - 1 > range->end_incl))
136 *len = range->end_incl + 1 - addr;
140 static inline bool no_range_check(struct vringh *vrh, u64 addr, size_t *len,
141 struct vringh_range *range,
142 bool (*getrange)(struct vringh *,
143 u64, struct vringh_range *))
148 /* No reason for this code to be inline. */
149 static int move_to_indirect(const struct vringh *vrh,
150 int *up_next, u16 *i, void *addr,
151 const struct vring_desc *desc,
152 struct vring_desc **descs, int *desc_max)
156 /* Indirect tables can't have indirect. */
157 if (*up_next != -1) {
158 vringh_bad("Multilevel indirect %u->%u", *up_next, *i);
162 len = vringh32_to_cpu(vrh, desc->len);
163 if (unlikely(len % sizeof(struct vring_desc))) {
164 vringh_bad("Strange indirect len %u", desc->len);
168 /* We will check this when we follow it! */
169 if (desc->flags & cpu_to_vringh16(vrh, VRING_DESC_F_NEXT))
170 *up_next = vringh16_to_cpu(vrh, desc->next);
174 *desc_max = len / sizeof(struct vring_desc);
176 /* Now, start at the first indirect. */
181 static int resize_iovec(struct vringh_kiov *iov, gfp_t gfp)
184 unsigned int flag, new_num = (iov->max_num & ~VRINGH_IOV_ALLOCATED) * 2;
189 flag = (iov->max_num & VRINGH_IOV_ALLOCATED);
191 new = krealloc(iov->iov, new_num * sizeof(struct iovec), gfp);
193 new = kmalloc(new_num * sizeof(struct iovec), gfp);
195 memcpy(new, iov->iov,
196 iov->max_num * sizeof(struct iovec));
197 flag = VRINGH_IOV_ALLOCATED;
203 iov->max_num = (new_num | flag);
207 static u16 __cold return_from_indirect(const struct vringh *vrh, int *up_next,
208 struct vring_desc **descs, int *desc_max)
213 *descs = vrh->vring.desc;
214 *desc_max = vrh->vring.num;
218 static int slow_copy(struct vringh *vrh, void *dst, const void *src,
219 bool (*rcheck)(struct vringh *vrh, u64 addr, size_t *len,
220 struct vringh_range *range,
221 bool (*getrange)(struct vringh *vrh,
223 struct vringh_range *)),
224 bool (*getrange)(struct vringh *vrh,
226 struct vringh_range *r),
227 struct vringh_range *range,
228 int (*copy)(void *dst, const void *src, size_t len))
230 size_t part, len = sizeof(struct vring_desc);
237 addr = (u64)(unsigned long)src - range->offset;
239 if (!rcheck(vrh, addr, &part, range, getrange))
242 err = copy(dst, src, part);
254 __vringh_iov(struct vringh *vrh, u16 i,
255 struct vringh_kiov *riov,
256 struct vringh_kiov *wiov,
257 bool (*rcheck)(struct vringh *vrh, u64 addr, size_t *len,
258 struct vringh_range *range,
259 bool (*getrange)(struct vringh *, u64,
260 struct vringh_range *)),
261 bool (*getrange)(struct vringh *, u64, struct vringh_range *),
263 int (*copy)(void *dst, const void *src, size_t len))
265 int err, count = 0, indirect_count = 0, up_next, desc_max;
266 struct vring_desc desc, *descs;
267 struct vringh_range range = { -1ULL, 0 }, slowrange;
270 /* We start traversing vring's descriptor table. */
271 descs = vrh->vring.desc;
272 desc_max = vrh->vring.num;
275 /* You must want something! */
276 if (WARN_ON(!riov && !wiov))
280 riov->i = riov->used = 0;
282 wiov->i = wiov->used = 0;
286 struct vringh_kiov *iov;
290 err = slow_copy(vrh, &desc, &descs[i], rcheck, getrange,
293 err = copy(&desc, &descs[i], sizeof(desc));
297 if (unlikely(desc.flags &
298 cpu_to_vringh16(vrh, VRING_DESC_F_INDIRECT))) {
299 u64 a = vringh64_to_cpu(vrh, desc.addr);
301 /* Make sure it's OK, and get offset. */
302 len = vringh32_to_cpu(vrh, desc.len);
303 if (!rcheck(vrh, a, &len, &range, getrange)) {
308 if (unlikely(len != vringh32_to_cpu(vrh, desc.len))) {
310 /* We need to save this range to use offset */
314 addr = (void *)(long)(a + range.offset);
315 err = move_to_indirect(vrh, &up_next, &i, addr, &desc,
327 if (count > vrh->vring.num || indirect_count > desc_max) {
328 vringh_bad("Descriptor loop in %p", descs);
333 if (desc.flags & cpu_to_vringh16(vrh, VRING_DESC_F_WRITE))
337 if (unlikely(wiov && wiov->used)) {
338 vringh_bad("Readable desc %p after writable",
346 vringh_bad("Unexpected %s desc",
347 !wiov ? "writable" : "readable");
353 /* Make sure it's OK, and get offset. */
354 len = vringh32_to_cpu(vrh, desc.len);
355 if (!rcheck(vrh, vringh64_to_cpu(vrh, desc.addr), &len, &range,
360 addr = (void *)(unsigned long)(vringh64_to_cpu(vrh, desc.addr) +
363 if (unlikely(iov->used == (iov->max_num & ~VRINGH_IOV_ALLOCATED))) {
364 err = resize_iovec(iov, gfp);
369 iov->iov[iov->used].iov_base = addr;
370 iov->iov[iov->used].iov_len = len;
373 if (unlikely(len != vringh32_to_cpu(vrh, desc.len))) {
374 desc.len = cpu_to_vringh32(vrh,
375 vringh32_to_cpu(vrh, desc.len) - len);
376 desc.addr = cpu_to_vringh64(vrh,
377 vringh64_to_cpu(vrh, desc.addr) + len);
381 if (desc.flags & cpu_to_vringh16(vrh, VRING_DESC_F_NEXT)) {
382 i = vringh16_to_cpu(vrh, desc.next);
384 /* Just in case we need to finish traversing above. */
385 if (unlikely(up_next > 0)) {
386 i = return_from_indirect(vrh, &up_next,
395 vringh_bad("Chained index %u > %u", i, desc_max);
407 static inline int __vringh_complete(struct vringh *vrh,
408 const struct vring_used_elem *used,
409 unsigned int num_used,
410 int (*putu16)(const struct vringh *vrh,
411 __virtio16 *p, u16 val),
412 int (*putused)(struct vring_used_elem *dst,
413 const struct vring_used_elem
416 struct vring_used *used_ring;
420 used_ring = vrh->vring.used;
421 used_idx = vrh->last_used_idx + vrh->completed;
423 off = used_idx % vrh->vring.num;
425 /* Compiler knows num_used == 1 sometimes, hence extra check */
426 if (num_used > 1 && unlikely(off + num_used >= vrh->vring.num)) {
427 u16 part = vrh->vring.num - off;
428 err = putused(&used_ring->ring[off], used, part);
430 err = putused(&used_ring->ring[0], used + part,
433 err = putused(&used_ring->ring[off], used, num_used);
436 vringh_bad("Failed to write %u used entries %u at %p",
437 num_used, off, &used_ring->ring[off]);
441 /* Make sure buffer is written before we update index. */
442 virtio_wmb(vrh->weak_barriers);
444 err = putu16(vrh, &vrh->vring.used->idx, used_idx + num_used);
446 vringh_bad("Failed to update used index at %p",
447 &vrh->vring.used->idx);
451 vrh->completed += num_used;
456 static inline int __vringh_need_notify(struct vringh *vrh,
457 int (*getu16)(const struct vringh *vrh,
459 const __virtio16 *p))
465 /* Flush out used index update. This is paired with the
466 * barrier that the Guest executes when enabling
468 virtio_mb(vrh->weak_barriers);
470 /* Old-style, without event indices. */
471 if (!vrh->event_indices) {
473 err = getu16(vrh, &flags, &vrh->vring.avail->flags);
475 vringh_bad("Failed to get flags at %p",
476 &vrh->vring.avail->flags);
479 return (!(flags & VRING_AVAIL_F_NO_INTERRUPT));
482 /* Modern: we know when other side wants to know. */
483 err = getu16(vrh, &used_event, &vring_used_event(&vrh->vring));
485 vringh_bad("Failed to get used event idx at %p",
486 &vring_used_event(&vrh->vring));
490 /* Just in case we added so many that we wrap. */
491 if (unlikely(vrh->completed > 0xffff))
494 notify = vring_need_event(used_event,
495 vrh->last_used_idx + vrh->completed,
498 vrh->last_used_idx += vrh->completed;
503 static inline bool __vringh_notify_enable(struct vringh *vrh,
504 int (*getu16)(const struct vringh *vrh,
505 u16 *val, const __virtio16 *p),
506 int (*putu16)(const struct vringh *vrh,
507 __virtio16 *p, u16 val))
511 if (!vrh->event_indices) {
512 /* Old-school; update flags. */
513 if (putu16(vrh, &vrh->vring.used->flags, 0) != 0) {
514 vringh_bad("Clearing used flags %p",
515 &vrh->vring.used->flags);
519 if (putu16(vrh, &vring_avail_event(&vrh->vring),
520 vrh->last_avail_idx) != 0) {
521 vringh_bad("Updating avail event index %p",
522 &vring_avail_event(&vrh->vring));
527 /* They could have slipped one in as we were doing that: make
528 * sure it's written, then check again. */
529 virtio_mb(vrh->weak_barriers);
531 if (getu16(vrh, &avail, &vrh->vring.avail->idx) != 0) {
532 vringh_bad("Failed to check avail idx at %p",
533 &vrh->vring.avail->idx);
537 /* This is unlikely, so we just leave notifications enabled
538 * (if we're using event_indices, we'll only get one
539 * notification anyway). */
540 return avail == vrh->last_avail_idx;
543 static inline void __vringh_notify_disable(struct vringh *vrh,
544 int (*putu16)(const struct vringh *vrh,
545 __virtio16 *p, u16 val))
547 if (!vrh->event_indices) {
548 /* Old-school; update flags. */
549 if (putu16(vrh, &vrh->vring.used->flags,
550 VRING_USED_F_NO_NOTIFY)) {
551 vringh_bad("Setting used flags %p",
552 &vrh->vring.used->flags);
557 /* Userspace access helpers: in this case, addresses are really userspace. */
558 static inline int getu16_user(const struct vringh *vrh, u16 *val, const __virtio16 *p)
561 int rc = get_user(v, (__force __virtio16 __user *)p);
562 *val = vringh16_to_cpu(vrh, v);
566 static inline int putu16_user(const struct vringh *vrh, __virtio16 *p, u16 val)
568 __virtio16 v = cpu_to_vringh16(vrh, val);
569 return put_user(v, (__force __virtio16 __user *)p);
572 static inline int copydesc_user(void *dst, const void *src, size_t len)
574 return copy_from_user(dst, (__force void __user *)src, len) ?
578 static inline int putused_user(struct vring_used_elem *dst,
579 const struct vring_used_elem *src,
582 return copy_to_user((__force void __user *)dst, src,
583 sizeof(*dst) * num) ? -EFAULT : 0;
586 static inline int xfer_from_user(void *src, void *dst, size_t len)
588 return copy_from_user(dst, (__force void __user *)src, len) ?
592 static inline int xfer_to_user(void *dst, void *src, size_t len)
594 return copy_to_user((__force void __user *)dst, src, len) ?
599 * vringh_init_user - initialize a vringh for a userspace vring.
600 * @vrh: the vringh to initialize.
601 * @features: the feature bits for this ring.
602 * @num: the number of elements.
603 * @weak_barriers: true if we only need memory barriers, not I/O.
604 * @desc: the userpace descriptor pointer.
605 * @avail: the userpace avail pointer.
606 * @used: the userpace used pointer.
608 * Returns an error if num is invalid: you should check pointers
611 int vringh_init_user(struct vringh *vrh, u64 features,
612 unsigned int num, bool weak_barriers,
613 struct vring_desc __user *desc,
614 struct vring_avail __user *avail,
615 struct vring_used __user *used)
617 /* Sane power of 2 please! */
618 if (!num || num > 0xffff || (num & (num - 1))) {
619 vringh_bad("Bad ring size %u", num);
623 vrh->little_endian = (features & (1ULL << VIRTIO_F_VERSION_1));
624 vrh->event_indices = (features & (1 << VIRTIO_RING_F_EVENT_IDX));
625 vrh->weak_barriers = weak_barriers;
627 vrh->last_avail_idx = 0;
628 vrh->last_used_idx = 0;
629 vrh->vring.num = num;
630 /* vring expects kernel addresses, but only used via accessors. */
631 vrh->vring.desc = (__force struct vring_desc *)desc;
632 vrh->vring.avail = (__force struct vring_avail *)avail;
633 vrh->vring.used = (__force struct vring_used *)used;
636 EXPORT_SYMBOL(vringh_init_user);
639 * vringh_getdesc_user - get next available descriptor from userspace ring.
640 * @vrh: the userspace vring.
641 * @riov: where to put the readable descriptors (or NULL)
642 * @wiov: where to put the writable descriptors (or NULL)
643 * @getrange: function to call to check ranges.
644 * @head: head index we received, for passing to vringh_complete_user().
646 * Returns 0 if there was no descriptor, 1 if there was, or -errno.
648 * Note that on error return, you can tell the difference between an
649 * invalid ring and a single invalid descriptor: in the former case,
650 * *head will be vrh->vring.num. You may be able to ignore an invalid
651 * descriptor, but there's not much you can do with an invalid ring.
653 * Note that you may need to clean up riov and wiov, even on error!
655 int vringh_getdesc_user(struct vringh *vrh,
656 struct vringh_iov *riov,
657 struct vringh_iov *wiov,
658 bool (*getrange)(struct vringh *vrh,
659 u64 addr, struct vringh_range *r),
664 *head = vrh->vring.num;
665 err = __vringh_get_head(vrh, getu16_user, &vrh->last_avail_idx);
670 if (err == vrh->vring.num)
673 /* We need the layouts to be the identical for this to work */
674 BUILD_BUG_ON(sizeof(struct vringh_kiov) != sizeof(struct vringh_iov));
675 BUILD_BUG_ON(offsetof(struct vringh_kiov, iov) !=
676 offsetof(struct vringh_iov, iov));
677 BUILD_BUG_ON(offsetof(struct vringh_kiov, i) !=
678 offsetof(struct vringh_iov, i));
679 BUILD_BUG_ON(offsetof(struct vringh_kiov, used) !=
680 offsetof(struct vringh_iov, used));
681 BUILD_BUG_ON(offsetof(struct vringh_kiov, max_num) !=
682 offsetof(struct vringh_iov, max_num));
683 BUILD_BUG_ON(sizeof(struct iovec) != sizeof(struct kvec));
684 BUILD_BUG_ON(offsetof(struct iovec, iov_base) !=
685 offsetof(struct kvec, iov_base));
686 BUILD_BUG_ON(offsetof(struct iovec, iov_len) !=
687 offsetof(struct kvec, iov_len));
688 BUILD_BUG_ON(sizeof(((struct iovec *)NULL)->iov_base)
689 != sizeof(((struct kvec *)NULL)->iov_base));
690 BUILD_BUG_ON(sizeof(((struct iovec *)NULL)->iov_len)
691 != sizeof(((struct kvec *)NULL)->iov_len));
694 err = __vringh_iov(vrh, *head, (struct vringh_kiov *)riov,
695 (struct vringh_kiov *)wiov,
696 range_check, getrange, GFP_KERNEL, copydesc_user);
702 EXPORT_SYMBOL(vringh_getdesc_user);
705 * vringh_iov_pull_user - copy bytes from vring_iov.
706 * @riov: the riov as passed to vringh_getdesc_user() (updated as we consume)
707 * @dst: the place to copy.
708 * @len: the maximum length to copy.
710 * Returns the bytes copied <= len or a negative errno.
712 ssize_t vringh_iov_pull_user(struct vringh_iov *riov, void *dst, size_t len)
714 return vringh_iov_xfer((struct vringh_kiov *)riov,
715 dst, len, xfer_from_user);
717 EXPORT_SYMBOL(vringh_iov_pull_user);
720 * vringh_iov_push_user - copy bytes into vring_iov.
721 * @wiov: the wiov as passed to vringh_getdesc_user() (updated as we consume)
722 * @dst: the place to copy.
723 * @len: the maximum length to copy.
725 * Returns the bytes copied <= len or a negative errno.
727 ssize_t vringh_iov_push_user(struct vringh_iov *wiov,
728 const void *src, size_t len)
730 return vringh_iov_xfer((struct vringh_kiov *)wiov,
731 (void *)src, len, xfer_to_user);
733 EXPORT_SYMBOL(vringh_iov_push_user);
736 * vringh_abandon_user - we've decided not to handle the descriptor(s).
738 * @num: the number of descriptors to put back (ie. num
739 * vringh_get_user() to undo).
741 * The next vringh_get_user() will return the old descriptor(s) again.
743 void vringh_abandon_user(struct vringh *vrh, unsigned int num)
745 /* We only update vring_avail_event(vr) when we want to be notified,
746 * so we haven't changed that yet. */
747 vrh->last_avail_idx -= num;
749 EXPORT_SYMBOL(vringh_abandon_user);
752 * vringh_complete_user - we've finished with descriptor, publish it.
754 * @head: the head as filled in by vringh_getdesc_user.
755 * @len: the length of data we have written.
757 * You should check vringh_need_notify_user() after one or more calls
760 int vringh_complete_user(struct vringh *vrh, u16 head, u32 len)
762 struct vring_used_elem used;
764 used.id = cpu_to_vringh32(vrh, head);
765 used.len = cpu_to_vringh32(vrh, len);
766 return __vringh_complete(vrh, &used, 1, putu16_user, putused_user);
768 EXPORT_SYMBOL(vringh_complete_user);
771 * vringh_complete_multi_user - we've finished with many descriptors.
773 * @used: the head, length pairs.
774 * @num_used: the number of used elements.
776 * You should check vringh_need_notify_user() after one or more calls
779 int vringh_complete_multi_user(struct vringh *vrh,
780 const struct vring_used_elem used[],
783 return __vringh_complete(vrh, used, num_used,
784 putu16_user, putused_user);
786 EXPORT_SYMBOL(vringh_complete_multi_user);
789 * vringh_notify_enable_user - we want to know if something changes.
792 * This always enables notifications, but returns false if there are
793 * now more buffers available in the vring.
795 bool vringh_notify_enable_user(struct vringh *vrh)
797 return __vringh_notify_enable(vrh, getu16_user, putu16_user);
799 EXPORT_SYMBOL(vringh_notify_enable_user);
802 * vringh_notify_disable_user - don't tell us if something changes.
805 * This is our normal running state: we disable and then only enable when
806 * we're going to sleep.
808 void vringh_notify_disable_user(struct vringh *vrh)
810 __vringh_notify_disable(vrh, putu16_user);
812 EXPORT_SYMBOL(vringh_notify_disable_user);
815 * vringh_need_notify_user - must we tell the other side about used buffers?
816 * @vrh: the vring we've called vringh_complete_user() on.
818 * Returns -errno or 0 if we don't need to tell the other side, 1 if we do.
820 int vringh_need_notify_user(struct vringh *vrh)
822 return __vringh_need_notify(vrh, getu16_user);
824 EXPORT_SYMBOL(vringh_need_notify_user);
826 /* Kernelspace access helpers. */
827 static inline int getu16_kern(const struct vringh *vrh,
828 u16 *val, const __virtio16 *p)
830 *val = vringh16_to_cpu(vrh, ACCESS_ONCE(*p));
834 static inline int putu16_kern(const struct vringh *vrh, __virtio16 *p, u16 val)
836 ACCESS_ONCE(*p) = cpu_to_vringh16(vrh, val);
840 static inline int copydesc_kern(void *dst, const void *src, size_t len)
842 memcpy(dst, src, len);
846 static inline int putused_kern(struct vring_used_elem *dst,
847 const struct vring_used_elem *src,
850 memcpy(dst, src, num * sizeof(*dst));
854 static inline int xfer_kern(void *src, void *dst, size_t len)
856 memcpy(dst, src, len);
861 * vringh_init_kern - initialize a vringh for a kernelspace vring.
862 * @vrh: the vringh to initialize.
863 * @features: the feature bits for this ring.
864 * @num: the number of elements.
865 * @weak_barriers: true if we only need memory barriers, not I/O.
866 * @desc: the userpace descriptor pointer.
867 * @avail: the userpace avail pointer.
868 * @used: the userpace used pointer.
870 * Returns an error if num is invalid.
872 int vringh_init_kern(struct vringh *vrh, u64 features,
873 unsigned int num, bool weak_barriers,
874 struct vring_desc *desc,
875 struct vring_avail *avail,
876 struct vring_used *used)
878 /* Sane power of 2 please! */
879 if (!num || num > 0xffff || (num & (num - 1))) {
880 vringh_bad("Bad ring size %u", num);
884 vrh->little_endian = (features & (1ULL << VIRTIO_F_VERSION_1));
885 vrh->event_indices = (features & (1 << VIRTIO_RING_F_EVENT_IDX));
886 vrh->weak_barriers = weak_barriers;
888 vrh->last_avail_idx = 0;
889 vrh->last_used_idx = 0;
890 vrh->vring.num = num;
891 vrh->vring.desc = desc;
892 vrh->vring.avail = avail;
893 vrh->vring.used = used;
896 EXPORT_SYMBOL(vringh_init_kern);
899 * vringh_getdesc_kern - get next available descriptor from kernelspace ring.
900 * @vrh: the kernelspace vring.
901 * @riov: where to put the readable descriptors (or NULL)
902 * @wiov: where to put the writable descriptors (or NULL)
903 * @head: head index we received, for passing to vringh_complete_kern().
904 * @gfp: flags for allocating larger riov/wiov.
906 * Returns 0 if there was no descriptor, 1 if there was, or -errno.
908 * Note that on error return, you can tell the difference between an
909 * invalid ring and a single invalid descriptor: in the former case,
910 * *head will be vrh->vring.num. You may be able to ignore an invalid
911 * descriptor, but there's not much you can do with an invalid ring.
913 * Note that you may need to clean up riov and wiov, even on error!
915 int vringh_getdesc_kern(struct vringh *vrh,
916 struct vringh_kiov *riov,
917 struct vringh_kiov *wiov,
923 err = __vringh_get_head(vrh, getu16_kern, &vrh->last_avail_idx);
928 if (err == vrh->vring.num)
932 err = __vringh_iov(vrh, *head, riov, wiov, no_range_check, NULL,
939 EXPORT_SYMBOL(vringh_getdesc_kern);
942 * vringh_iov_pull_kern - copy bytes from vring_iov.
943 * @riov: the riov as passed to vringh_getdesc_kern() (updated as we consume)
944 * @dst: the place to copy.
945 * @len: the maximum length to copy.
947 * Returns the bytes copied <= len or a negative errno.
949 ssize_t vringh_iov_pull_kern(struct vringh_kiov *riov, void *dst, size_t len)
951 return vringh_iov_xfer(riov, dst, len, xfer_kern);
953 EXPORT_SYMBOL(vringh_iov_pull_kern);
956 * vringh_iov_push_kern - copy bytes into vring_iov.
957 * @wiov: the wiov as passed to vringh_getdesc_kern() (updated as we consume)
958 * @dst: the place to copy.
959 * @len: the maximum length to copy.
961 * Returns the bytes copied <= len or a negative errno.
963 ssize_t vringh_iov_push_kern(struct vringh_kiov *wiov,
964 const void *src, size_t len)
966 return vringh_iov_xfer(wiov, (void *)src, len, xfer_kern);
968 EXPORT_SYMBOL(vringh_iov_push_kern);
971 * vringh_abandon_kern - we've decided not to handle the descriptor(s).
973 * @num: the number of descriptors to put back (ie. num
974 * vringh_get_kern() to undo).
976 * The next vringh_get_kern() will return the old descriptor(s) again.
978 void vringh_abandon_kern(struct vringh *vrh, unsigned int num)
980 /* We only update vring_avail_event(vr) when we want to be notified,
981 * so we haven't changed that yet. */
982 vrh->last_avail_idx -= num;
984 EXPORT_SYMBOL(vringh_abandon_kern);
987 * vringh_complete_kern - we've finished with descriptor, publish it.
989 * @head: the head as filled in by vringh_getdesc_kern.
990 * @len: the length of data we have written.
992 * You should check vringh_need_notify_kern() after one or more calls
995 int vringh_complete_kern(struct vringh *vrh, u16 head, u32 len)
997 struct vring_used_elem used;
999 used.id = cpu_to_vringh32(vrh, head);
1000 used.len = cpu_to_vringh32(vrh, len);
1002 return __vringh_complete(vrh, &used, 1, putu16_kern, putused_kern);
1004 EXPORT_SYMBOL(vringh_complete_kern);
1007 * vringh_notify_enable_kern - we want to know if something changes.
1010 * This always enables notifications, but returns false if there are
1011 * now more buffers available in the vring.
1013 bool vringh_notify_enable_kern(struct vringh *vrh)
1015 return __vringh_notify_enable(vrh, getu16_kern, putu16_kern);
1017 EXPORT_SYMBOL(vringh_notify_enable_kern);
1020 * vringh_notify_disable_kern - don't tell us if something changes.
1023 * This is our normal running state: we disable and then only enable when
1024 * we're going to sleep.
1026 void vringh_notify_disable_kern(struct vringh *vrh)
1028 __vringh_notify_disable(vrh, putu16_kern);
1030 EXPORT_SYMBOL(vringh_notify_disable_kern);
1033 * vringh_need_notify_kern - must we tell the other side about used buffers?
1034 * @vrh: the vring we've called vringh_complete_kern() on.
1036 * Returns -errno or 0 if we don't need to tell the other side, 1 if we do.
1038 int vringh_need_notify_kern(struct vringh *vrh)
1040 return __vringh_need_notify(vrh, getu16_kern);
1042 EXPORT_SYMBOL(vringh_need_notify_kern);
1044 MODULE_LICENSE("GPL");