1 /* Virtio ring implementation.
3 * Copyright 2007 Rusty Russell IBM Corporation
5 * This program is free software; you can redistribute it and/or modify
6 * it under the terms of the GNU General Public License as published by
7 * the Free Software Foundation; either version 2 of the License, or
8 * (at your option) any later version.
10 * This program is distributed in the hope that it will be useful,
11 * but WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 * GNU General Public License for more details.
15 * You should have received a copy of the GNU General Public License
16 * along with this program; if not, write to the Free Software
17 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
19 #include <linux/virtio.h>
20 #include <linux/virtio_ring.h>
21 #include <linux/virtio_config.h>
22 #include <linux/device.h>
23 #include <linux/slab.h>
24 #include <linux/module.h>
25 #include <linux/hrtimer.h>
26 #include <linux/kmemleak.h>
29 /* For development, we want to crash whenever the ring is screwed. */
30 #define BAD_RING(_vq, fmt, args...) \
32 dev_err(&(_vq)->vq.vdev->dev, \
33 "%s:"fmt, (_vq)->vq.name, ##args); \
36 /* Caller is supposed to guarantee no reentry. */
37 #define START_USE(_vq) \
40 panic("%s:in_use = %i\n", \
41 (_vq)->vq.name, (_vq)->in_use); \
42 (_vq)->in_use = __LINE__; \
44 #define END_USE(_vq) \
45 do { BUG_ON(!(_vq)->in_use); (_vq)->in_use = 0; } while(0)
47 #define BAD_RING(_vq, fmt, args...) \
49 dev_err(&_vq->vq.vdev->dev, \
50 "%s:"fmt, (_vq)->vq.name, ##args); \
51 (_vq)->broken = true; \
57 struct vring_virtqueue {
60 /* Actual memory layout for this queue */
63 /* Can we use weak barriers? */
66 /* Other side has made a mess, don't try any more. */
69 /* Host supports indirect buffers */
72 /* Host publishes avail event idx */
75 /* Head of free buffer list. */
76 unsigned int free_head;
77 /* Number we've added since last sync. */
78 unsigned int num_added;
80 /* Last used index we've seen. */
83 /* Last written value to avail->flags */
84 u16 avail_flags_shadow;
86 /* Last written value to avail->idx in guest byte order */
89 /* How to notify other side. FIXME: commonalize hcalls! */
90 bool (*notify)(struct virtqueue *vq);
93 /* They're supposed to lock for us. */
96 /* Figure out if their kicks are too delayed. */
97 bool last_add_time_valid;
98 ktime_t last_add_time;
101 /* Tokens for callbacks. */
105 #define to_vvq(_vq) container_of(_vq, struct vring_virtqueue, vq)
107 static struct vring_desc *alloc_indirect(struct virtqueue *_vq,
108 unsigned int total_sg, gfp_t gfp)
110 struct vring_desc *desc;
114 * We require lowmem mappings for the descriptors because
115 * otherwise virt_to_phys will give us bogus addresses in the
118 gfp &= ~__GFP_HIGHMEM;
120 desc = kmalloc(total_sg * sizeof(struct vring_desc), gfp);
124 for (i = 0; i < total_sg; i++)
125 desc[i].next = cpu_to_virtio16(_vq->vdev, i + 1);
129 static inline int virtqueue_add(struct virtqueue *_vq,
130 struct scatterlist *sgs[],
131 unsigned int total_sg,
132 unsigned int out_sgs,
137 struct vring_virtqueue *vq = to_vvq(_vq);
138 struct scatterlist *sg;
139 struct vring_desc *desc;
140 unsigned int i, n, avail, descs_used, uninitialized_var(prev);
146 BUG_ON(data == NULL);
148 if (unlikely(vq->broken)) {
155 ktime_t now = ktime_get();
157 /* No kick or get, with .1 second between? Warn. */
158 if (vq->last_add_time_valid)
159 WARN_ON(ktime_to_ms(ktime_sub(now, vq->last_add_time))
161 vq->last_add_time = now;
162 vq->last_add_time_valid = true;
166 BUG_ON(total_sg > vq->vring.num);
167 BUG_ON(total_sg == 0);
169 head = vq->free_head;
171 /* If the host supports indirect descriptor tables, and we have multiple
172 * buffers, then go indirect. FIXME: tune this threshold */
173 if (vq->indirect && total_sg > 1 && vq->vq.num_free)
174 desc = alloc_indirect(_vq, total_sg, gfp);
179 /* Use a single buffer which doesn't continue */
180 vq->vring.desc[head].flags = cpu_to_virtio16(_vq->vdev, VRING_DESC_F_INDIRECT);
181 vq->vring.desc[head].addr = cpu_to_virtio64(_vq->vdev, virt_to_phys(desc));
182 /* avoid kmemleak false positive (hidden by virt_to_phys) */
183 kmemleak_ignore(desc);
184 vq->vring.desc[head].len = cpu_to_virtio32(_vq->vdev, total_sg * sizeof(struct vring_desc));
186 /* Set up rest to use this indirect table. */
191 desc = vq->vring.desc;
193 descs_used = total_sg;
197 if (vq->vq.num_free < descs_used) {
198 pr_debug("Can't add buf len %i - avail = %i\n",
199 descs_used, vq->vq.num_free);
200 /* FIXME: for historical reasons, we force a notify here if
201 * there are outgoing parts to the buffer. Presumably the
202 * host should service the ring ASAP. */
211 /* We're about to use some buffers from the free list. */
212 vq->vq.num_free -= descs_used;
214 for (n = 0; n < out_sgs; n++) {
215 for (sg = sgs[n]; sg; sg = sg_next(sg)) {
216 desc[i].flags = cpu_to_virtio16(_vq->vdev, VRING_DESC_F_NEXT);
217 desc[i].addr = cpu_to_virtio64(_vq->vdev, sg_phys(sg));
218 desc[i].len = cpu_to_virtio32(_vq->vdev, sg->length);
220 i = virtio16_to_cpu(_vq->vdev, desc[i].next);
223 for (; n < (out_sgs + in_sgs); n++) {
224 for (sg = sgs[n]; sg; sg = sg_next(sg)) {
225 desc[i].flags = cpu_to_virtio16(_vq->vdev, VRING_DESC_F_NEXT | VRING_DESC_F_WRITE);
226 desc[i].addr = cpu_to_virtio64(_vq->vdev, sg_phys(sg));
227 desc[i].len = cpu_to_virtio32(_vq->vdev, sg->length);
229 i = virtio16_to_cpu(_vq->vdev, desc[i].next);
232 /* Last one doesn't continue. */
233 desc[prev].flags &= cpu_to_virtio16(_vq->vdev, ~VRING_DESC_F_NEXT);
235 /* Update free pointer */
237 vq->free_head = virtio16_to_cpu(_vq->vdev, vq->vring.desc[head].next);
242 vq->data[head] = data;
244 /* Put entry in available array (but don't update avail->idx until they
246 avail = vq->avail_idx_shadow & (vq->vring.num - 1);
247 vq->vring.avail->ring[avail] = cpu_to_virtio16(_vq->vdev, head);
249 /* Descriptors and available array need to be set before we expose the
250 * new available array entries. */
251 virtio_wmb(vq->weak_barriers);
252 vq->avail_idx_shadow++;
253 vq->vring.avail->idx = cpu_to_virtio16(_vq->vdev, vq->avail_idx_shadow);
256 pr_debug("Added buffer head %i to %p\n", head, vq);
259 /* This is very unlikely, but theoretically possible. Kick
261 if (unlikely(vq->num_added == (1 << 16) - 1))
268 * virtqueue_add_sgs - expose buffers to other end
269 * @vq: the struct virtqueue we're talking about.
270 * @sgs: array of terminated scatterlists.
271 * @out_num: the number of scatterlists readable by other side
272 * @in_num: the number of scatterlists which are writable (after readable ones)
273 * @data: the token identifying the buffer.
274 * @gfp: how to do memory allocations (if necessary).
276 * Caller must ensure we don't call this with other virtqueue operations
277 * at the same time (except where noted).
279 * Returns zero or a negative error (ie. ENOSPC, ENOMEM, EIO).
281 int virtqueue_add_sgs(struct virtqueue *_vq,
282 struct scatterlist *sgs[],
283 unsigned int out_sgs,
288 unsigned int i, total_sg = 0;
290 /* Count them first. */
291 for (i = 0; i < out_sgs + in_sgs; i++) {
292 struct scatterlist *sg;
293 for (sg = sgs[i]; sg; sg = sg_next(sg))
296 return virtqueue_add(_vq, sgs, total_sg, out_sgs, in_sgs, data, gfp);
298 EXPORT_SYMBOL_GPL(virtqueue_add_sgs);
301 * virtqueue_add_outbuf - expose output buffers to other end
302 * @vq: the struct virtqueue we're talking about.
303 * @sg: scatterlist (must be well-formed and terminated!)
304 * @num: the number of entries in @sg readable by other side
305 * @data: the token identifying the buffer.
306 * @gfp: how to do memory allocations (if necessary).
308 * Caller must ensure we don't call this with other virtqueue operations
309 * at the same time (except where noted).
311 * Returns zero or a negative error (ie. ENOSPC, ENOMEM, EIO).
313 int virtqueue_add_outbuf(struct virtqueue *vq,
314 struct scatterlist *sg, unsigned int num,
318 return virtqueue_add(vq, &sg, num, 1, 0, data, gfp);
320 EXPORT_SYMBOL_GPL(virtqueue_add_outbuf);
323 * virtqueue_add_inbuf - expose input buffers to other end
324 * @vq: the struct virtqueue we're talking about.
325 * @sg: scatterlist (must be well-formed and terminated!)
326 * @num: the number of entries in @sg writable by other side
327 * @data: the token identifying the buffer.
328 * @gfp: how to do memory allocations (if necessary).
330 * Caller must ensure we don't call this with other virtqueue operations
331 * at the same time (except where noted).
333 * Returns zero or a negative error (ie. ENOSPC, ENOMEM, EIO).
335 int virtqueue_add_inbuf(struct virtqueue *vq,
336 struct scatterlist *sg, unsigned int num,
340 return virtqueue_add(vq, &sg, num, 0, 1, data, gfp);
342 EXPORT_SYMBOL_GPL(virtqueue_add_inbuf);
345 * virtqueue_kick_prepare - first half of split virtqueue_kick call.
346 * @vq: the struct virtqueue
348 * Instead of virtqueue_kick(), you can do:
349 * if (virtqueue_kick_prepare(vq))
350 * virtqueue_notify(vq);
352 * This is sometimes useful because the virtqueue_kick_prepare() needs
353 * to be serialized, but the actual virtqueue_notify() call does not.
355 bool virtqueue_kick_prepare(struct virtqueue *_vq)
357 struct vring_virtqueue *vq = to_vvq(_vq);
362 /* We need to expose available array entries before checking avail
364 virtio_mb(vq->weak_barriers);
366 old = vq->avail_idx_shadow - vq->num_added;
367 new = vq->avail_idx_shadow;
371 if (vq->last_add_time_valid) {
372 WARN_ON(ktime_to_ms(ktime_sub(ktime_get(),
373 vq->last_add_time)) > 100);
375 vq->last_add_time_valid = false;
379 needs_kick = vring_need_event(virtio16_to_cpu(_vq->vdev, vring_avail_event(&vq->vring)),
382 needs_kick = !(vq->vring.used->flags & cpu_to_virtio16(_vq->vdev, VRING_USED_F_NO_NOTIFY));
387 EXPORT_SYMBOL_GPL(virtqueue_kick_prepare);
390 * virtqueue_notify - second half of split virtqueue_kick call.
391 * @vq: the struct virtqueue
393 * This does not need to be serialized.
395 * Returns false if host notify failed or queue is broken, otherwise true.
397 bool virtqueue_notify(struct virtqueue *_vq)
399 struct vring_virtqueue *vq = to_vvq(_vq);
401 if (unlikely(vq->broken))
404 /* Prod other side to tell it about changes. */
405 if (!vq->notify(_vq)) {
411 EXPORT_SYMBOL_GPL(virtqueue_notify);
414 * virtqueue_kick - update after add_buf
415 * @vq: the struct virtqueue
417 * After one or more virtqueue_add_* calls, invoke this to kick
420 * Caller must ensure we don't call this with other virtqueue
421 * operations at the same time (except where noted).
423 * Returns false if kick failed, otherwise true.
425 bool virtqueue_kick(struct virtqueue *vq)
427 if (virtqueue_kick_prepare(vq))
428 return virtqueue_notify(vq);
431 EXPORT_SYMBOL_GPL(virtqueue_kick);
433 static void detach_buf(struct vring_virtqueue *vq, unsigned int head)
437 /* Clear data ptr. */
438 vq->data[head] = NULL;
440 /* Put back on free list: find end */
443 /* Free the indirect table */
444 if (vq->vring.desc[i].flags & cpu_to_virtio16(vq->vq.vdev, VRING_DESC_F_INDIRECT))
445 kfree(phys_to_virt(virtio64_to_cpu(vq->vq.vdev, vq->vring.desc[i].addr)));
447 while (vq->vring.desc[i].flags & cpu_to_virtio16(vq->vq.vdev, VRING_DESC_F_NEXT)) {
448 i = virtio16_to_cpu(vq->vq.vdev, vq->vring.desc[i].next);
452 vq->vring.desc[i].next = cpu_to_virtio16(vq->vq.vdev, vq->free_head);
453 vq->free_head = head;
454 /* Plus final descriptor */
458 static inline bool more_used(const struct vring_virtqueue *vq)
460 return vq->last_used_idx != virtio16_to_cpu(vq->vq.vdev, vq->vring.used->idx);
464 * virtqueue_get_buf - get the next used buffer
465 * @vq: the struct virtqueue we're talking about.
466 * @len: the length written into the buffer
468 * If the driver wrote data into the buffer, @len will be set to the
469 * amount written. This means you don't need to clear the buffer
470 * beforehand to ensure there's no data leakage in the case of short
473 * Caller must ensure we don't call this with other virtqueue
474 * operations at the same time (except where noted).
476 * Returns NULL if there are no used buffers, or the "data" token
477 * handed to virtqueue_add_*().
479 void *virtqueue_get_buf(struct virtqueue *_vq, unsigned int *len)
481 struct vring_virtqueue *vq = to_vvq(_vq);
488 if (unlikely(vq->broken)) {
493 if (!more_used(vq)) {
494 pr_debug("No more buffers in queue\n");
499 /* Only get used array entries after they have been exposed by host. */
500 virtio_rmb(vq->weak_barriers);
502 last_used = (vq->last_used_idx & (vq->vring.num - 1));
503 i = virtio32_to_cpu(_vq->vdev, vq->vring.used->ring[last_used].id);
504 *len = virtio32_to_cpu(_vq->vdev, vq->vring.used->ring[last_used].len);
506 if (unlikely(i >= vq->vring.num)) {
507 BAD_RING(vq, "id %u out of range\n", i);
510 if (unlikely(!vq->data[i])) {
511 BAD_RING(vq, "id %u is not a head!\n", i);
515 /* detach_buf clears data, so grab it now. */
519 /* If we expect an interrupt for the next entry, tell host
520 * by writing event index and flush out the write before
521 * the read in the next get_buf call. */
522 if (!(vq->avail_flags_shadow & VRING_AVAIL_F_NO_INTERRUPT)) {
523 vring_used_event(&vq->vring) = cpu_to_virtio16(_vq->vdev, vq->last_used_idx);
524 virtio_mb(vq->weak_barriers);
528 vq->last_add_time_valid = false;
534 EXPORT_SYMBOL_GPL(virtqueue_get_buf);
537 * virtqueue_disable_cb - disable callbacks
538 * @vq: the struct virtqueue we're talking about.
540 * Note that this is not necessarily synchronous, hence unreliable and only
541 * useful as an optimization.
543 * Unlike other operations, this need not be serialized.
545 void virtqueue_disable_cb(struct virtqueue *_vq)
547 struct vring_virtqueue *vq = to_vvq(_vq);
549 if (!(vq->avail_flags_shadow & VRING_AVAIL_F_NO_INTERRUPT)) {
550 vq->avail_flags_shadow |= VRING_AVAIL_F_NO_INTERRUPT;
551 vq->vring.avail->flags = cpu_to_virtio16(_vq->vdev, vq->avail_flags_shadow);
555 EXPORT_SYMBOL_GPL(virtqueue_disable_cb);
558 * virtqueue_enable_cb_prepare - restart callbacks after disable_cb
559 * @vq: the struct virtqueue we're talking about.
561 * This re-enables callbacks; it returns current queue state
562 * in an opaque unsigned value. This value should be later tested by
563 * virtqueue_poll, to detect a possible race between the driver checking for
564 * more work, and enabling callbacks.
566 * Caller must ensure we don't call this with other virtqueue
567 * operations at the same time (except where noted).
569 unsigned virtqueue_enable_cb_prepare(struct virtqueue *_vq)
571 struct vring_virtqueue *vq = to_vvq(_vq);
576 /* We optimistically turn back on interrupts, then check if there was
578 /* Depending on the VIRTIO_RING_F_EVENT_IDX feature, we need to
579 * either clear the flags bit or point the event index at the next
580 * entry. Always do both to keep code simple. */
581 if (vq->avail_flags_shadow & VRING_AVAIL_F_NO_INTERRUPT) {
582 vq->avail_flags_shadow &= ~VRING_AVAIL_F_NO_INTERRUPT;
583 vq->vring.avail->flags = cpu_to_virtio16(_vq->vdev, vq->avail_flags_shadow);
585 vring_used_event(&vq->vring) = cpu_to_virtio16(_vq->vdev, last_used_idx = vq->last_used_idx);
587 return last_used_idx;
589 EXPORT_SYMBOL_GPL(virtqueue_enable_cb_prepare);
592 * virtqueue_poll - query pending used buffers
593 * @vq: the struct virtqueue we're talking about.
594 * @last_used_idx: virtqueue state (from call to virtqueue_enable_cb_prepare).
596 * Returns "true" if there are pending used buffers in the queue.
598 * This does not need to be serialized.
600 bool virtqueue_poll(struct virtqueue *_vq, unsigned last_used_idx)
602 struct vring_virtqueue *vq = to_vvq(_vq);
604 virtio_mb(vq->weak_barriers);
605 return (u16)last_used_idx != virtio16_to_cpu(_vq->vdev, vq->vring.used->idx);
607 EXPORT_SYMBOL_GPL(virtqueue_poll);
610 * virtqueue_enable_cb - restart callbacks after disable_cb.
611 * @vq: the struct virtqueue we're talking about.
613 * This re-enables callbacks; it returns "false" if there are pending
614 * buffers in the queue, to detect a possible race between the driver
615 * checking for more work, and enabling callbacks.
617 * Caller must ensure we don't call this with other virtqueue
618 * operations at the same time (except where noted).
620 bool virtqueue_enable_cb(struct virtqueue *_vq)
622 unsigned last_used_idx = virtqueue_enable_cb_prepare(_vq);
623 return !virtqueue_poll(_vq, last_used_idx);
625 EXPORT_SYMBOL_GPL(virtqueue_enable_cb);
628 * virtqueue_enable_cb_delayed - restart callbacks after disable_cb.
629 * @vq: the struct virtqueue we're talking about.
631 * This re-enables callbacks but hints to the other side to delay
632 * interrupts until most of the available buffers have been processed;
633 * it returns "false" if there are many pending buffers in the queue,
634 * to detect a possible race between the driver checking for more work,
635 * and enabling callbacks.
637 * Caller must ensure we don't call this with other virtqueue
638 * operations at the same time (except where noted).
640 bool virtqueue_enable_cb_delayed(struct virtqueue *_vq)
642 struct vring_virtqueue *vq = to_vvq(_vq);
647 /* We optimistically turn back on interrupts, then check if there was
649 /* Depending on the VIRTIO_RING_F_USED_EVENT_IDX feature, we need to
650 * either clear the flags bit or point the event index at the next
651 * entry. Always do both to keep code simple. */
652 if (vq->avail_flags_shadow & VRING_AVAIL_F_NO_INTERRUPT) {
653 vq->avail_flags_shadow &= ~VRING_AVAIL_F_NO_INTERRUPT;
654 vq->vring.avail->flags = cpu_to_virtio16(_vq->vdev, vq->avail_flags_shadow);
656 /* TODO: tune this threshold */
657 bufs = (u16)(vq->avail_idx_shadow - vq->last_used_idx) * 3 / 4;
658 vring_used_event(&vq->vring) = cpu_to_virtio16(_vq->vdev, vq->last_used_idx + bufs);
659 virtio_mb(vq->weak_barriers);
660 if (unlikely((u16)(virtio16_to_cpu(_vq->vdev, vq->vring.used->idx) - vq->last_used_idx) > bufs)) {
668 EXPORT_SYMBOL_GPL(virtqueue_enable_cb_delayed);
671 * virtqueue_detach_unused_buf - detach first unused buffer
672 * @vq: the struct virtqueue we're talking about.
674 * Returns NULL or the "data" token handed to virtqueue_add_*().
675 * This is not valid on an active queue; it is useful only for device
678 void *virtqueue_detach_unused_buf(struct virtqueue *_vq)
680 struct vring_virtqueue *vq = to_vvq(_vq);
686 for (i = 0; i < vq->vring.num; i++) {
689 /* detach_buf clears data, so grab it now. */
692 vq->avail_idx_shadow--;
693 vq->vring.avail->idx = cpu_to_virtio16(_vq->vdev, vq->avail_idx_shadow);
697 /* That should have freed everything. */
698 BUG_ON(vq->vq.num_free != vq->vring.num);
703 EXPORT_SYMBOL_GPL(virtqueue_detach_unused_buf);
705 irqreturn_t vring_interrupt(int irq, void *_vq)
707 struct vring_virtqueue *vq = to_vvq(_vq);
709 if (!more_used(vq)) {
710 pr_debug("virtqueue interrupt with no work for %p\n", vq);
714 if (unlikely(vq->broken))
717 pr_debug("virtqueue callback for %p (%p)\n", vq, vq->vq.callback);
719 vq->vq.callback(&vq->vq);
723 EXPORT_SYMBOL_GPL(vring_interrupt);
725 struct virtqueue *vring_new_virtqueue(unsigned int index,
727 unsigned int vring_align,
728 struct virtio_device *vdev,
731 bool (*notify)(struct virtqueue *),
732 void (*callback)(struct virtqueue *),
735 struct vring_virtqueue *vq;
738 /* We assume num is a power of 2. */
739 if (num & (num - 1)) {
740 dev_warn(&vdev->dev, "Bad virtqueue length %u\n", num);
744 vq = kmalloc(sizeof(*vq) + sizeof(void *)*num, GFP_KERNEL);
748 vring_init(&vq->vring, num, pages, vring_align);
749 vq->vq.callback = callback;
752 vq->vq.num_free = num;
753 vq->vq.index = index;
755 vq->weak_barriers = weak_barriers;
757 vq->last_used_idx = 0;
758 vq->avail_flags_shadow = 0;
759 vq->avail_idx_shadow = 0;
761 list_add_tail(&vq->vq.list, &vdev->vqs);
764 vq->last_add_time_valid = false;
767 vq->indirect = virtio_has_feature(vdev, VIRTIO_RING_F_INDIRECT_DESC);
768 vq->event = virtio_has_feature(vdev, VIRTIO_RING_F_EVENT_IDX);
770 /* No callback? Tell other side not to bother us. */
772 vq->avail_flags_shadow |= VRING_AVAIL_F_NO_INTERRUPT;
773 vq->vring.avail->flags = cpu_to_virtio16(vdev, vq->avail_flags_shadow);
776 /* Put everything in free lists. */
778 for (i = 0; i < num-1; i++) {
779 vq->vring.desc[i].next = cpu_to_virtio16(vdev, i + 1);
786 EXPORT_SYMBOL_GPL(vring_new_virtqueue);
788 void vring_del_virtqueue(struct virtqueue *vq)
793 EXPORT_SYMBOL_GPL(vring_del_virtqueue);
795 /* Manipulates transport-specific feature bits. */
796 void vring_transport_features(struct virtio_device *vdev)
800 for (i = VIRTIO_TRANSPORT_F_START; i < VIRTIO_TRANSPORT_F_END; i++) {
802 case VIRTIO_RING_F_INDIRECT_DESC:
804 case VIRTIO_RING_F_EVENT_IDX:
806 case VIRTIO_F_VERSION_1:
809 /* We don't understand this bit. */
810 __virtio_clear_bit(vdev, i);
814 EXPORT_SYMBOL_GPL(vring_transport_features);
817 * virtqueue_get_vring_size - return the size of the virtqueue's vring
818 * @vq: the struct virtqueue containing the vring of interest.
820 * Returns the size of the vring. This is mainly used for boasting to
821 * userspace. Unlike other operations, this need not be serialized.
823 unsigned int virtqueue_get_vring_size(struct virtqueue *_vq)
826 struct vring_virtqueue *vq = to_vvq(_vq);
828 return vq->vring.num;
830 EXPORT_SYMBOL_GPL(virtqueue_get_vring_size);
832 bool virtqueue_is_broken(struct virtqueue *_vq)
834 struct vring_virtqueue *vq = to_vvq(_vq);
838 EXPORT_SYMBOL_GPL(virtqueue_is_broken);
841 * This should prevent the device from being used, allowing drivers to
842 * recover. You may need to grab appropriate locks to flush.
844 void virtio_break_device(struct virtio_device *dev)
846 struct virtqueue *_vq;
848 list_for_each_entry(_vq, &dev->vqs, list) {
849 struct vring_virtqueue *vq = to_vvq(_vq);
853 EXPORT_SYMBOL_GPL(virtio_break_device);
855 void *virtqueue_get_avail(struct virtqueue *_vq)
857 struct vring_virtqueue *vq = to_vvq(_vq);
859 return vq->vring.avail;
861 EXPORT_SYMBOL_GPL(virtqueue_get_avail);
863 void *virtqueue_get_used(struct virtqueue *_vq)
865 struct vring_virtqueue *vq = to_vvq(_vq);
867 return vq->vring.used;
869 EXPORT_SYMBOL_GPL(virtqueue_get_used);
871 MODULE_LICENSE("GPL");