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>
28 /* For development, we want to crash whenever the ring is screwed. */
29 #define BAD_RING(_vq, fmt, args...) \
31 dev_err(&(_vq)->vq.vdev->dev, \
32 "%s:"fmt, (_vq)->vq.name, ##args); \
35 /* Caller is supposed to guarantee no reentry. */
36 #define START_USE(_vq) \
39 panic("%s:in_use = %i\n", \
40 (_vq)->vq.name, (_vq)->in_use); \
41 (_vq)->in_use = __LINE__; \
43 #define END_USE(_vq) \
44 do { BUG_ON(!(_vq)->in_use); (_vq)->in_use = 0; } while(0)
46 #define BAD_RING(_vq, fmt, args...) \
48 dev_err(&_vq->vq.vdev->dev, \
49 "%s:"fmt, (_vq)->vq.name, ##args); \
50 (_vq)->broken = true; \
56 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 /* How to notify other side. FIXME: commonalize hcalls! */
84 void (*notify)(struct virtqueue *vq);
87 /* They're supposed to lock for us. */
90 /* Figure out if their kicks are too delayed. */
91 bool last_add_time_valid;
92 ktime_t last_add_time;
95 /* Tokens for callbacks. */
99 #define to_vvq(_vq) container_of(_vq, struct vring_virtqueue, vq)
101 static inline struct scatterlist *sg_next_chained(struct scatterlist *sg,
107 static inline struct scatterlist *sg_next_arr(struct scatterlist *sg,
115 /* Set up an indirect table of descriptors and add it to the queue. */
116 static inline int vring_add_indirect(struct vring_virtqueue *vq,
117 struct scatterlist *sgs[],
118 struct scatterlist *(*next)
119 (struct scatterlist *, unsigned int *),
120 unsigned int total_sg,
121 unsigned int total_out,
122 unsigned int total_in,
123 unsigned int out_sgs,
127 struct vring_desc *desc;
129 struct scatterlist *sg;
133 * We require lowmem mappings for the descriptors because
134 * otherwise virt_to_phys will give us bogus addresses in the
137 gfp &= ~(__GFP_HIGHMEM | __GFP_HIGH);
139 desc = kmalloc(total_sg * sizeof(struct vring_desc), gfp);
143 /* Transfer entries from the sg lists into the indirect page */
145 for (n = 0; n < out_sgs; n++) {
146 for (sg = sgs[n]; sg; sg = next(sg, &total_out)) {
147 desc[i].flags = VRING_DESC_F_NEXT;
148 desc[i].addr = sg_phys(sg);
149 desc[i].len = sg->length;
154 for (; n < (out_sgs + in_sgs); n++) {
155 for (sg = sgs[n]; sg; sg = next(sg, &total_in)) {
156 desc[i].flags = VRING_DESC_F_NEXT|VRING_DESC_F_WRITE;
157 desc[i].addr = sg_phys(sg);
158 desc[i].len = sg->length;
163 BUG_ON(i != total_sg);
165 /* Last one doesn't continue. */
166 desc[i-1].flags &= ~VRING_DESC_F_NEXT;
169 /* We're about to use a buffer */
172 /* Use a single buffer which doesn't continue */
173 head = vq->free_head;
174 vq->vring.desc[head].flags = VRING_DESC_F_INDIRECT;
175 vq->vring.desc[head].addr = virt_to_phys(desc);
176 vq->vring.desc[head].len = i * sizeof(struct vring_desc);
178 /* Update free pointer */
179 vq->free_head = vq->vring.desc[head].next;
184 static inline int virtqueue_add(struct virtqueue *_vq,
185 struct scatterlist *sgs[],
186 struct scatterlist *(*next)
187 (struct scatterlist *, unsigned int *),
188 unsigned int total_out,
189 unsigned int total_in,
190 unsigned int out_sgs,
195 struct vring_virtqueue *vq = to_vvq(_vq);
196 struct scatterlist *sg;
197 unsigned int i, n, avail, uninitialized_var(prev), total_sg;
202 BUG_ON(data == NULL);
206 ktime_t now = ktime_get();
208 /* No kick or get, with .1 second between? Warn. */
209 if (vq->last_add_time_valid)
210 WARN_ON(ktime_to_ms(ktime_sub(now, vq->last_add_time))
212 vq->last_add_time = now;
213 vq->last_add_time_valid = true;
217 total_sg = total_in + total_out;
219 /* If the host supports indirect descriptor tables, and we have multiple
220 * buffers, then go indirect. FIXME: tune this threshold */
221 if (vq->indirect && total_sg > 1 && vq->vq.num_free) {
222 head = vring_add_indirect(vq, sgs, next, total_sg, total_out,
224 out_sgs, in_sgs, gfp);
225 if (likely(head >= 0))
229 BUG_ON(total_sg > vq->vring.num);
230 BUG_ON(total_sg == 0);
232 if (vq->vq.num_free < total_sg) {
233 pr_debug("Can't add buf len %i - avail = %i\n",
234 total_sg, vq->vq.num_free);
235 /* FIXME: for historical reasons, we force a notify here if
236 * there are outgoing parts to the buffer. Presumably the
237 * host should service the ring ASAP. */
244 /* We're about to use some buffers from the free list. */
245 vq->vq.num_free -= total_sg;
247 head = i = vq->free_head;
248 for (n = 0; n < out_sgs; n++) {
249 for (sg = sgs[n]; sg; sg = next(sg, &total_out)) {
250 vq->vring.desc[i].flags = VRING_DESC_F_NEXT;
251 vq->vring.desc[i].addr = sg_phys(sg);
252 vq->vring.desc[i].len = sg->length;
254 i = vq->vring.desc[i].next;
257 for (; n < (out_sgs + in_sgs); n++) {
258 for (sg = sgs[n]; sg; sg = next(sg, &total_in)) {
259 vq->vring.desc[i].flags = VRING_DESC_F_NEXT|VRING_DESC_F_WRITE;
260 vq->vring.desc[i].addr = sg_phys(sg);
261 vq->vring.desc[i].len = sg->length;
263 i = vq->vring.desc[i].next;
266 /* Last one doesn't continue. */
267 vq->vring.desc[prev].flags &= ~VRING_DESC_F_NEXT;
269 /* Update free pointer */
274 vq->data[head] = data;
276 /* Put entry in available array (but don't update avail->idx until they
278 avail = (vq->vring.avail->idx & (vq->vring.num-1));
279 vq->vring.avail->ring[avail] = head;
281 /* Descriptors and available array need to be set before we expose the
282 * new available array entries. */
283 virtio_wmb(vq->weak_barriers);
284 vq->vring.avail->idx++;
287 /* This is very unlikely, but theoretically possible. Kick
289 if (unlikely(vq->num_added == (1 << 16) - 1))
292 pr_debug("Added buffer head %i to %p\n", head, vq);
299 * virtqueue_add_sgs - expose buffers to other end
300 * @vq: the struct virtqueue we're talking about.
301 * @sgs: array of terminated scatterlists.
302 * @out_num: the number of scatterlists readable by other side
303 * @in_num: the number of scatterlists which are writable (after readable ones)
304 * @data: the token identifying the buffer.
305 * @gfp: how to do memory allocations (if necessary).
307 * Caller must ensure we don't call this with other virtqueue operations
308 * at the same time (except where noted).
310 * Returns zero or a negative error (ie. ENOSPC, ENOMEM).
312 int virtqueue_add_sgs(struct virtqueue *_vq,
313 struct scatterlist *sgs[],
314 unsigned int out_sgs,
319 unsigned int i, total_out, total_in;
321 /* Count them first. */
322 for (i = total_out = total_in = 0; i < out_sgs; i++) {
323 struct scatterlist *sg;
324 for (sg = sgs[i]; sg; sg = sg_next(sg))
327 for (; i < out_sgs + in_sgs; i++) {
328 struct scatterlist *sg;
329 for (sg = sgs[i]; sg; sg = sg_next(sg))
332 return virtqueue_add(_vq, sgs, sg_next_chained,
333 total_out, total_in, out_sgs, in_sgs, data, gfp);
335 EXPORT_SYMBOL_GPL(virtqueue_add_sgs);
338 * virtqueue_add_outbuf - expose output buffers to other end
339 * @vq: the struct virtqueue we're talking about.
340 * @sgs: array of scatterlists (need not be terminated!)
341 * @num: the number of scatterlists readable by other side
342 * @data: the token identifying the buffer.
343 * @gfp: how to do memory allocations (if necessary).
345 * Caller must ensure we don't call this with other virtqueue operations
346 * at the same time (except where noted).
348 * Returns zero or a negative error (ie. ENOSPC, ENOMEM).
350 int virtqueue_add_outbuf(struct virtqueue *vq,
351 struct scatterlist sg[], unsigned int num,
355 return virtqueue_add(vq, &sg, sg_next_arr, num, 0, 1, 0, data, gfp);
357 EXPORT_SYMBOL_GPL(virtqueue_add_outbuf);
360 * virtqueue_add_inbuf - expose input buffers to other end
361 * @vq: the struct virtqueue we're talking about.
362 * @sgs: array of scatterlists (need not be terminated!)
363 * @num: the number of scatterlists writable by other side
364 * @data: the token identifying the buffer.
365 * @gfp: how to do memory allocations (if necessary).
367 * Caller must ensure we don't call this with other virtqueue operations
368 * at the same time (except where noted).
370 * Returns zero or a negative error (ie. ENOSPC, ENOMEM).
372 int virtqueue_add_inbuf(struct virtqueue *vq,
373 struct scatterlist sg[], unsigned int num,
377 return virtqueue_add(vq, &sg, sg_next_arr, 0, num, 0, 1, data, gfp);
379 EXPORT_SYMBOL_GPL(virtqueue_add_inbuf);
382 * virtqueue_kick_prepare - first half of split virtqueue_kick call.
383 * @vq: the struct virtqueue
385 * Instead of virtqueue_kick(), you can do:
386 * if (virtqueue_kick_prepare(vq))
387 * virtqueue_notify(vq);
389 * This is sometimes useful because the virtqueue_kick_prepare() needs
390 * to be serialized, but the actual virtqueue_notify() call does not.
392 bool virtqueue_kick_prepare(struct virtqueue *_vq)
394 struct vring_virtqueue *vq = to_vvq(_vq);
399 /* We need to expose available array entries before checking avail
401 virtio_mb(vq->weak_barriers);
403 old = vq->vring.avail->idx - vq->num_added;
404 new = vq->vring.avail->idx;
408 if (vq->last_add_time_valid) {
409 WARN_ON(ktime_to_ms(ktime_sub(ktime_get(),
410 vq->last_add_time)) > 100);
412 vq->last_add_time_valid = false;
416 needs_kick = vring_need_event(vring_avail_event(&vq->vring),
419 needs_kick = !(vq->vring.used->flags & VRING_USED_F_NO_NOTIFY);
424 EXPORT_SYMBOL_GPL(virtqueue_kick_prepare);
427 * virtqueue_notify - second half of split virtqueue_kick call.
428 * @vq: the struct virtqueue
430 * This does not need to be serialized.
432 void virtqueue_notify(struct virtqueue *_vq)
434 struct vring_virtqueue *vq = to_vvq(_vq);
436 /* Prod other side to tell it about changes. */
439 EXPORT_SYMBOL_GPL(virtqueue_notify);
442 * virtqueue_kick - update after add_buf
443 * @vq: the struct virtqueue
445 * After one or more virtqueue_add_* calls, invoke this to kick
448 * Caller must ensure we don't call this with other virtqueue
449 * operations at the same time (except where noted).
451 void virtqueue_kick(struct virtqueue *vq)
453 if (virtqueue_kick_prepare(vq))
454 virtqueue_notify(vq);
456 EXPORT_SYMBOL_GPL(virtqueue_kick);
458 static void detach_buf(struct vring_virtqueue *vq, unsigned int head)
462 /* Clear data ptr. */
463 vq->data[head] = NULL;
465 /* Put back on free list: find end */
468 /* Free the indirect table */
469 if (vq->vring.desc[i].flags & VRING_DESC_F_INDIRECT)
470 kfree(phys_to_virt(vq->vring.desc[i].addr));
472 while (vq->vring.desc[i].flags & VRING_DESC_F_NEXT) {
473 i = vq->vring.desc[i].next;
477 vq->vring.desc[i].next = vq->free_head;
478 vq->free_head = head;
479 /* Plus final descriptor */
483 static inline bool more_used(const struct vring_virtqueue *vq)
485 return vq->last_used_idx != vq->vring.used->idx;
489 * virtqueue_get_buf - get the next used buffer
490 * @vq: the struct virtqueue we're talking about.
491 * @len: the length written into the buffer
493 * If the driver wrote data into the buffer, @len will be set to the
494 * amount written. This means you don't need to clear the buffer
495 * beforehand to ensure there's no data leakage in the case of short
498 * Caller must ensure we don't call this with other virtqueue
499 * operations at the same time (except where noted).
501 * Returns NULL if there are no used buffers, or the "data" token
502 * handed to virtqueue_add_*().
504 void *virtqueue_get_buf(struct virtqueue *_vq, unsigned int *len)
506 struct vring_virtqueue *vq = to_vvq(_vq);
513 if (unlikely(vq->broken)) {
518 if (!more_used(vq)) {
519 pr_debug("No more buffers in queue\n");
524 /* Only get used array entries after they have been exposed by host. */
525 virtio_rmb(vq->weak_barriers);
527 last_used = (vq->last_used_idx & (vq->vring.num - 1));
528 i = vq->vring.used->ring[last_used].id;
529 *len = vq->vring.used->ring[last_used].len;
531 if (unlikely(i >= vq->vring.num)) {
532 BAD_RING(vq, "id %u out of range\n", i);
535 if (unlikely(!vq->data[i])) {
536 BAD_RING(vq, "id %u is not a head!\n", i);
540 /* detach_buf clears data, so grab it now. */
544 /* If we expect an interrupt for the next entry, tell host
545 * by writing event index and flush out the write before
546 * the read in the next get_buf call. */
547 if (!(vq->vring.avail->flags & VRING_AVAIL_F_NO_INTERRUPT)) {
548 vring_used_event(&vq->vring) = vq->last_used_idx;
549 virtio_mb(vq->weak_barriers);
553 vq->last_add_time_valid = false;
559 EXPORT_SYMBOL_GPL(virtqueue_get_buf);
562 * virtqueue_disable_cb - disable callbacks
563 * @vq: the struct virtqueue we're talking about.
565 * Note that this is not necessarily synchronous, hence unreliable and only
566 * useful as an optimization.
568 * Unlike other operations, this need not be serialized.
570 void virtqueue_disable_cb(struct virtqueue *_vq)
572 struct vring_virtqueue *vq = to_vvq(_vq);
574 vq->vring.avail->flags |= VRING_AVAIL_F_NO_INTERRUPT;
576 EXPORT_SYMBOL_GPL(virtqueue_disable_cb);
579 * virtqueue_enable_cb_prepare - restart callbacks after disable_cb
580 * @vq: the struct virtqueue we're talking about.
582 * This re-enables callbacks; it returns current queue state
583 * in an opaque unsigned value. This value should be later tested by
584 * virtqueue_poll, to detect a possible race between the driver checking for
585 * more work, and enabling callbacks.
587 * Caller must ensure we don't call this with other virtqueue
588 * operations at the same time (except where noted).
590 unsigned virtqueue_enable_cb_prepare(struct virtqueue *_vq)
592 struct vring_virtqueue *vq = to_vvq(_vq);
597 /* We optimistically turn back on interrupts, then check if there was
599 /* Depending on the VIRTIO_RING_F_EVENT_IDX feature, we need to
600 * either clear the flags bit or point the event index at the next
601 * entry. Always do both to keep code simple. */
602 vq->vring.avail->flags &= ~VRING_AVAIL_F_NO_INTERRUPT;
603 vring_used_event(&vq->vring) = last_used_idx = vq->last_used_idx;
605 return last_used_idx;
607 EXPORT_SYMBOL_GPL(virtqueue_enable_cb_prepare);
610 * virtqueue_poll - query pending used buffers
611 * @vq: the struct virtqueue we're talking about.
612 * @last_used_idx: virtqueue state (from call to virtqueue_enable_cb_prepare).
614 * Returns "true" if there are pending used buffers in the queue.
616 * This does not need to be serialized.
618 bool virtqueue_poll(struct virtqueue *_vq, unsigned last_used_idx)
620 struct vring_virtqueue *vq = to_vvq(_vq);
622 virtio_mb(vq->weak_barriers);
623 return (u16)last_used_idx != vq->vring.used->idx;
625 EXPORT_SYMBOL_GPL(virtqueue_poll);
628 * virtqueue_enable_cb - restart callbacks after disable_cb.
629 * @vq: the struct virtqueue we're talking about.
631 * This re-enables callbacks; it returns "false" if there are pending
632 * buffers in the queue, to detect a possible race between the driver
633 * checking for more work, and enabling callbacks.
635 * Caller must ensure we don't call this with other virtqueue
636 * operations at the same time (except where noted).
638 bool virtqueue_enable_cb(struct virtqueue *_vq)
640 unsigned last_used_idx = virtqueue_enable_cb_prepare(_vq);
641 return !virtqueue_poll(_vq, last_used_idx);
643 EXPORT_SYMBOL_GPL(virtqueue_enable_cb);
646 * virtqueue_enable_cb_delayed - restart callbacks after disable_cb.
647 * @vq: the struct virtqueue we're talking about.
649 * This re-enables callbacks but hints to the other side to delay
650 * interrupts until most of the available buffers have been processed;
651 * it returns "false" if there are many pending buffers in the queue,
652 * to detect a possible race between the driver checking for more work,
653 * and enabling callbacks.
655 * Caller must ensure we don't call this with other virtqueue
656 * operations at the same time (except where noted).
658 bool virtqueue_enable_cb_delayed(struct virtqueue *_vq)
660 struct vring_virtqueue *vq = to_vvq(_vq);
665 /* We optimistically turn back on interrupts, then check if there was
667 /* Depending on the VIRTIO_RING_F_USED_EVENT_IDX feature, we need to
668 * either clear the flags bit or point the event index at the next
669 * entry. Always do both to keep code simple. */
670 vq->vring.avail->flags &= ~VRING_AVAIL_F_NO_INTERRUPT;
671 /* TODO: tune this threshold */
672 bufs = (u16)(vq->vring.avail->idx - vq->last_used_idx) * 3 / 4;
673 vring_used_event(&vq->vring) = vq->last_used_idx + bufs;
674 virtio_mb(vq->weak_barriers);
675 if (unlikely((u16)(vq->vring.used->idx - vq->last_used_idx) > bufs)) {
683 EXPORT_SYMBOL_GPL(virtqueue_enable_cb_delayed);
686 * virtqueue_detach_unused_buf - detach first unused buffer
687 * @vq: the struct virtqueue we're talking about.
689 * Returns NULL or the "data" token handed to virtqueue_add_*().
690 * This is not valid on an active queue; it is useful only for device
693 void *virtqueue_detach_unused_buf(struct virtqueue *_vq)
695 struct vring_virtqueue *vq = to_vvq(_vq);
701 for (i = 0; i < vq->vring.num; i++) {
704 /* detach_buf clears data, so grab it now. */
707 vq->vring.avail->idx--;
711 /* That should have freed everything. */
712 BUG_ON(vq->vq.num_free != vq->vring.num);
717 EXPORT_SYMBOL_GPL(virtqueue_detach_unused_buf);
719 irqreturn_t vring_interrupt(int irq, void *_vq)
721 struct vring_virtqueue *vq = to_vvq(_vq);
723 if (!more_used(vq)) {
724 pr_debug("virtqueue interrupt with no work for %p\n", vq);
728 if (unlikely(vq->broken))
731 pr_debug("virtqueue callback for %p (%p)\n", vq, vq->vq.callback);
733 vq->vq.callback(&vq->vq);
737 EXPORT_SYMBOL_GPL(vring_interrupt);
739 struct virtqueue *vring_new_virtqueue(unsigned int index,
741 unsigned int vring_align,
742 struct virtio_device *vdev,
745 void (*notify)(struct virtqueue *),
746 void (*callback)(struct virtqueue *),
749 struct vring_virtqueue *vq;
752 /* We assume num is a power of 2. */
753 if (num & (num - 1)) {
754 dev_warn(&vdev->dev, "Bad virtqueue length %u\n", num);
758 vq = kmalloc(sizeof(*vq) + sizeof(void *)*num, GFP_KERNEL);
762 vring_init(&vq->vring, num, pages, vring_align);
763 vq->vq.callback = callback;
766 vq->vq.num_free = num;
767 vq->vq.index = index;
769 vq->weak_barriers = weak_barriers;
771 vq->last_used_idx = 0;
773 list_add_tail(&vq->vq.list, &vdev->vqs);
776 vq->last_add_time_valid = false;
779 vq->indirect = virtio_has_feature(vdev, VIRTIO_RING_F_INDIRECT_DESC);
780 vq->event = virtio_has_feature(vdev, VIRTIO_RING_F_EVENT_IDX);
782 /* No callback? Tell other side not to bother us. */
784 vq->vring.avail->flags |= VRING_AVAIL_F_NO_INTERRUPT;
786 /* Put everything in free lists. */
788 for (i = 0; i < num-1; i++) {
789 vq->vring.desc[i].next = i+1;
796 EXPORT_SYMBOL_GPL(vring_new_virtqueue);
798 void vring_del_virtqueue(struct virtqueue *vq)
803 EXPORT_SYMBOL_GPL(vring_del_virtqueue);
805 /* Manipulates transport-specific feature bits. */
806 void vring_transport_features(struct virtio_device *vdev)
810 for (i = VIRTIO_TRANSPORT_F_START; i < VIRTIO_TRANSPORT_F_END; i++) {
812 case VIRTIO_RING_F_INDIRECT_DESC:
814 case VIRTIO_RING_F_EVENT_IDX:
817 /* We don't understand this bit. */
818 clear_bit(i, vdev->features);
822 EXPORT_SYMBOL_GPL(vring_transport_features);
825 * virtqueue_get_vring_size - return the size of the virtqueue's vring
826 * @vq: the struct virtqueue containing the vring of interest.
828 * Returns the size of the vring. This is mainly used for boasting to
829 * userspace. Unlike other operations, this need not be serialized.
831 unsigned int virtqueue_get_vring_size(struct virtqueue *_vq)
834 struct vring_virtqueue *vq = to_vvq(_vq);
836 return vq->vring.num;
838 EXPORT_SYMBOL_GPL(virtqueue_get_vring_size);
840 MODULE_LICENSE("GPL");