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>
27 #include <linux/dma-mapping.h>
31 /* For development, we want to crash whenever the ring is screwed. */
32 #define BAD_RING(_vq, fmt, args...) \
34 dev_err(&(_vq)->vq.vdev->dev, \
35 "%s:"fmt, (_vq)->vq.name, ##args); \
38 /* Caller is supposed to guarantee no reentry. */
39 #define START_USE(_vq) \
42 panic("%s:in_use = %i\n", \
43 (_vq)->vq.name, (_vq)->in_use); \
44 (_vq)->in_use = __LINE__; \
46 #define END_USE(_vq) \
47 do { BUG_ON(!(_vq)->in_use); (_vq)->in_use = 0; } while(0)
49 #define BAD_RING(_vq, fmt, args...) \
51 dev_err(&_vq->vq.vdev->dev, \
52 "%s:"fmt, (_vq)->vq.name, ##args); \
53 (_vq)->broken = true; \
59 struct vring_desc_state {
60 void *data; /* Data for callback. */
61 struct vring_desc *indir_desc; /* Indirect descriptor, if any. */
64 struct vring_virtqueue {
67 /* Actual memory layout for this queue */
70 /* Can we use weak barriers? */
73 /* Other side has made a mess, don't try any more. */
76 /* Host supports indirect buffers */
79 /* Host publishes avail event idx */
82 /* Head of free buffer list. */
83 unsigned int free_head;
84 /* Number we've added since last sync. */
85 unsigned int num_added;
87 /* Last used index we've seen. */
90 /* Last written value to avail->flags */
91 u16 avail_flags_shadow;
93 /* Last written value to avail->idx in guest byte order */
96 /* How to notify other side. FIXME: commonalize hcalls! */
97 bool (*notify)(struct virtqueue *vq);
99 /* DMA, allocation, and size information */
101 size_t queue_size_in_bytes;
102 dma_addr_t queue_dma_addr;
105 /* They're supposed to lock for us. */
108 /* Figure out if their kicks are too delayed. */
109 bool last_add_time_valid;
110 ktime_t last_add_time;
113 /* Per-descriptor state. */
114 struct vring_desc_state desc_state[];
117 #define to_vvq(_vq) container_of(_vq, struct vring_virtqueue, vq)
120 * Modern virtio devices have feature bits to specify whether they need a
121 * quirk and bypass the IOMMU. If not there, just use the DMA API.
123 * If there, the interaction between virtio and DMA API is messy.
125 * On most systems with virtio, physical addresses match bus addresses,
126 * and it doesn't particularly matter whether we use the DMA API.
128 * On some systems, including Xen and any system with a physical device
129 * that speaks virtio behind a physical IOMMU, we must use the DMA API
130 * for virtio DMA to work at all.
132 * On other systems, including SPARC and PPC64, virtio-pci devices are
133 * enumerated as though they are behind an IOMMU, but the virtio host
134 * ignores the IOMMU, so we must either pretend that the IOMMU isn't
135 * there or somehow map everything as the identity.
137 * For the time being, we preserve historic behavior and bypass the DMA
140 * TODO: install a per-device DMA ops structure that does the right thing
141 * taking into account all the above quirks, and use the DMA API
142 * unconditionally on data path.
145 static bool vring_use_dma_api(struct virtio_device *vdev)
147 if (!virtio_has_iommu_quirk(vdev))
150 /* Otherwise, we are left to guess. */
152 * In theory, it's possible to have a buggy QEMU-supposed
153 * emulated Q35 IOMMU and Xen enabled at the same time. On
154 * such a configuration, virtio has never worked and will
155 * not work without an even larger kludge. Instead, enable
156 * the DMA API if we're a Xen guest, which at least allows
157 * all of the sensible Xen configurations to work correctly.
166 * The DMA ops on various arches are rather gnarly right now, and
167 * making all of the arch DMA ops work on the vring device itself
168 * is a mess. For now, we use the parent device for DMA ops.
170 struct device *vring_dma_dev(const struct vring_virtqueue *vq)
172 return vq->vq.vdev->dev.parent;
175 /* Map one sg entry. */
176 static dma_addr_t vring_map_one_sg(const struct vring_virtqueue *vq,
177 struct scatterlist *sg,
178 enum dma_data_direction direction)
180 if (!vring_use_dma_api(vq->vq.vdev))
181 return (dma_addr_t)sg_phys(sg);
184 * We can't use dma_map_sg, because we don't use scatterlists in
185 * the way it expects (we don't guarantee that the scatterlist
186 * will exist for the lifetime of the mapping).
188 return dma_map_page(vring_dma_dev(vq),
189 sg_page(sg), sg->offset, sg->length,
193 static dma_addr_t vring_map_single(const struct vring_virtqueue *vq,
194 void *cpu_addr, size_t size,
195 enum dma_data_direction direction)
197 if (!vring_use_dma_api(vq->vq.vdev))
198 return (dma_addr_t)virt_to_phys(cpu_addr);
200 return dma_map_single(vring_dma_dev(vq),
201 cpu_addr, size, direction);
204 static void vring_unmap_one(const struct vring_virtqueue *vq,
205 struct vring_desc *desc)
209 if (!vring_use_dma_api(vq->vq.vdev))
212 flags = virtio16_to_cpu(vq->vq.vdev, desc->flags);
214 if (flags & VRING_DESC_F_INDIRECT) {
215 dma_unmap_single(vring_dma_dev(vq),
216 virtio64_to_cpu(vq->vq.vdev, desc->addr),
217 virtio32_to_cpu(vq->vq.vdev, desc->len),
218 (flags & VRING_DESC_F_WRITE) ?
219 DMA_FROM_DEVICE : DMA_TO_DEVICE);
221 dma_unmap_page(vring_dma_dev(vq),
222 virtio64_to_cpu(vq->vq.vdev, desc->addr),
223 virtio32_to_cpu(vq->vq.vdev, desc->len),
224 (flags & VRING_DESC_F_WRITE) ?
225 DMA_FROM_DEVICE : DMA_TO_DEVICE);
229 static int vring_mapping_error(const struct vring_virtqueue *vq,
232 if (!vring_use_dma_api(vq->vq.vdev))
235 return dma_mapping_error(vring_dma_dev(vq), addr);
238 static struct vring_desc *alloc_indirect(struct virtqueue *_vq,
239 unsigned int total_sg, gfp_t gfp)
241 struct vring_desc *desc;
245 * We require lowmem mappings for the descriptors because
246 * otherwise virt_to_phys will give us bogus addresses in the
249 gfp &= ~__GFP_HIGHMEM;
251 desc = kmalloc(total_sg * sizeof(struct vring_desc), gfp);
255 for (i = 0; i < total_sg; i++)
256 desc[i].next = cpu_to_virtio16(_vq->vdev, i + 1);
260 static inline int virtqueue_add(struct virtqueue *_vq,
261 struct scatterlist *sgs[],
262 unsigned int total_sg,
263 unsigned int out_sgs,
268 struct vring_virtqueue *vq = to_vvq(_vq);
269 struct scatterlist *sg;
270 struct vring_desc *desc;
271 unsigned int i, n, avail, descs_used, uninitialized_var(prev), err_idx;
277 BUG_ON(data == NULL);
279 if (unlikely(vq->broken)) {
286 ktime_t now = ktime_get();
288 /* No kick or get, with .1 second between? Warn. */
289 if (vq->last_add_time_valid)
290 WARN_ON(ktime_to_ms(ktime_sub(now, vq->last_add_time))
292 vq->last_add_time = now;
293 vq->last_add_time_valid = true;
297 BUG_ON(total_sg > vq->vring.num);
298 BUG_ON(total_sg == 0);
300 head = vq->free_head;
302 /* If the host supports indirect descriptor tables, and we have multiple
303 * buffers, then go indirect. FIXME: tune this threshold */
304 if (vq->indirect && total_sg > 1 && vq->vq.num_free)
305 desc = alloc_indirect(_vq, total_sg, gfp);
310 /* Use a single buffer which doesn't continue */
312 /* Set up rest to use this indirect table. */
317 desc = vq->vring.desc;
319 descs_used = total_sg;
322 if (vq->vq.num_free < descs_used) {
323 pr_debug("Can't add buf len %i - avail = %i\n",
324 descs_used, vq->vq.num_free);
325 /* FIXME: for historical reasons, we force a notify here if
326 * there are outgoing parts to the buffer. Presumably the
327 * host should service the ring ASAP. */
336 for (n = 0; n < out_sgs; n++) {
337 for (sg = sgs[n]; sg; sg = sg_next(sg)) {
338 dma_addr_t addr = vring_map_one_sg(vq, sg, DMA_TO_DEVICE);
339 if (vring_mapping_error(vq, addr))
342 desc[i].flags = cpu_to_virtio16(_vq->vdev, VRING_DESC_F_NEXT);
343 desc[i].addr = cpu_to_virtio64(_vq->vdev, addr);
344 desc[i].len = cpu_to_virtio32(_vq->vdev, sg->length);
346 i = virtio16_to_cpu(_vq->vdev, desc[i].next);
349 for (; n < (out_sgs + in_sgs); n++) {
350 for (sg = sgs[n]; sg; sg = sg_next(sg)) {
351 dma_addr_t addr = vring_map_one_sg(vq, sg, DMA_FROM_DEVICE);
352 if (vring_mapping_error(vq, addr))
355 desc[i].flags = cpu_to_virtio16(_vq->vdev, VRING_DESC_F_NEXT | VRING_DESC_F_WRITE);
356 desc[i].addr = cpu_to_virtio64(_vq->vdev, addr);
357 desc[i].len = cpu_to_virtio32(_vq->vdev, sg->length);
359 i = virtio16_to_cpu(_vq->vdev, desc[i].next);
362 /* Last one doesn't continue. */
363 desc[prev].flags &= cpu_to_virtio16(_vq->vdev, ~VRING_DESC_F_NEXT);
366 /* Now that the indirect table is filled in, map it. */
367 dma_addr_t addr = vring_map_single(
368 vq, desc, total_sg * sizeof(struct vring_desc),
370 if (vring_mapping_error(vq, addr))
373 vq->vring.desc[head].flags = cpu_to_virtio16(_vq->vdev, VRING_DESC_F_INDIRECT);
374 vq->vring.desc[head].addr = cpu_to_virtio64(_vq->vdev, addr);
376 vq->vring.desc[head].len = cpu_to_virtio32(_vq->vdev, total_sg * sizeof(struct vring_desc));
379 /* We're using some buffers from the free list. */
380 vq->vq.num_free -= descs_used;
382 /* Update free pointer */
384 vq->free_head = virtio16_to_cpu(_vq->vdev, vq->vring.desc[head].next);
388 /* Store token and indirect buffer state. */
389 vq->desc_state[head].data = data;
391 vq->desc_state[head].indir_desc = desc;
393 /* Put entry in available array (but don't update avail->idx until they
395 avail = vq->avail_idx_shadow & (vq->vring.num - 1);
396 vq->vring.avail->ring[avail] = cpu_to_virtio16(_vq->vdev, head);
398 /* Descriptors and available array need to be set before we expose the
399 * new available array entries. */
400 virtio_wmb(vq->weak_barriers);
401 vq->avail_idx_shadow++;
402 vq->vring.avail->idx = cpu_to_virtio16(_vq->vdev, vq->avail_idx_shadow);
405 pr_debug("Added buffer head %i to %p\n", head, vq);
408 /* This is very unlikely, but theoretically possible. Kick
410 if (unlikely(vq->num_added == (1 << 16) - 1))
419 for (n = 0; n < total_sg; n++) {
422 vring_unmap_one(vq, &desc[i]);
423 i = vq->vring.desc[i].next;
426 vq->vq.num_free += total_sg;
435 * virtqueue_add_sgs - expose buffers to other end
436 * @vq: the struct virtqueue we're talking about.
437 * @sgs: array of terminated scatterlists.
438 * @out_num: the number of scatterlists readable by other side
439 * @in_num: the number of scatterlists which are writable (after readable ones)
440 * @data: the token identifying the buffer.
441 * @gfp: how to do memory allocations (if necessary).
443 * Caller must ensure we don't call this with other virtqueue operations
444 * at the same time (except where noted).
446 * Returns zero or a negative error (ie. ENOSPC, ENOMEM, EIO).
448 int virtqueue_add_sgs(struct virtqueue *_vq,
449 struct scatterlist *sgs[],
450 unsigned int out_sgs,
455 unsigned int i, total_sg = 0;
457 /* Count them first. */
458 for (i = 0; i < out_sgs + in_sgs; i++) {
459 struct scatterlist *sg;
460 for (sg = sgs[i]; sg; sg = sg_next(sg))
463 return virtqueue_add(_vq, sgs, total_sg, out_sgs, in_sgs, data, gfp);
465 EXPORT_SYMBOL_GPL(virtqueue_add_sgs);
468 * virtqueue_add_outbuf - expose output buffers to other end
469 * @vq: the struct virtqueue we're talking about.
470 * @sg: scatterlist (must be well-formed and terminated!)
471 * @num: the number of entries in @sg readable by other side
472 * @data: the token identifying the buffer.
473 * @gfp: how to do memory allocations (if necessary).
475 * Caller must ensure we don't call this with other virtqueue operations
476 * at the same time (except where noted).
478 * Returns zero or a negative error (ie. ENOSPC, ENOMEM, EIO).
480 int virtqueue_add_outbuf(struct virtqueue *vq,
481 struct scatterlist *sg, unsigned int num,
485 return virtqueue_add(vq, &sg, num, 1, 0, data, gfp);
487 EXPORT_SYMBOL_GPL(virtqueue_add_outbuf);
490 * virtqueue_add_inbuf - expose input buffers to other end
491 * @vq: the struct virtqueue we're talking about.
492 * @sg: scatterlist (must be well-formed and terminated!)
493 * @num: the number of entries in @sg writable by other side
494 * @data: the token identifying the buffer.
495 * @gfp: how to do memory allocations (if necessary).
497 * Caller must ensure we don't call this with other virtqueue operations
498 * at the same time (except where noted).
500 * Returns zero or a negative error (ie. ENOSPC, ENOMEM, EIO).
502 int virtqueue_add_inbuf(struct virtqueue *vq,
503 struct scatterlist *sg, unsigned int num,
507 return virtqueue_add(vq, &sg, num, 0, 1, data, gfp);
509 EXPORT_SYMBOL_GPL(virtqueue_add_inbuf);
512 * virtqueue_kick_prepare - first half of split virtqueue_kick call.
513 * @vq: the struct virtqueue
515 * Instead of virtqueue_kick(), you can do:
516 * if (virtqueue_kick_prepare(vq))
517 * virtqueue_notify(vq);
519 * This is sometimes useful because the virtqueue_kick_prepare() needs
520 * to be serialized, but the actual virtqueue_notify() call does not.
522 bool virtqueue_kick_prepare(struct virtqueue *_vq)
524 struct vring_virtqueue *vq = to_vvq(_vq);
529 /* We need to expose available array entries before checking avail
531 virtio_mb(vq->weak_barriers);
533 old = vq->avail_idx_shadow - vq->num_added;
534 new = vq->avail_idx_shadow;
538 if (vq->last_add_time_valid) {
539 WARN_ON(ktime_to_ms(ktime_sub(ktime_get(),
540 vq->last_add_time)) > 100);
542 vq->last_add_time_valid = false;
546 needs_kick = vring_need_event(virtio16_to_cpu(_vq->vdev, vring_avail_event(&vq->vring)),
549 needs_kick = !(vq->vring.used->flags & cpu_to_virtio16(_vq->vdev, VRING_USED_F_NO_NOTIFY));
554 EXPORT_SYMBOL_GPL(virtqueue_kick_prepare);
557 * virtqueue_notify - second half of split virtqueue_kick call.
558 * @vq: the struct virtqueue
560 * This does not need to be serialized.
562 * Returns false if host notify failed or queue is broken, otherwise true.
564 bool virtqueue_notify(struct virtqueue *_vq)
566 struct vring_virtqueue *vq = to_vvq(_vq);
568 if (unlikely(vq->broken))
571 /* Prod other side to tell it about changes. */
572 if (!vq->notify(_vq)) {
578 EXPORT_SYMBOL_GPL(virtqueue_notify);
581 * virtqueue_kick - update after add_buf
582 * @vq: the struct virtqueue
584 * After one or more virtqueue_add_* calls, invoke this to kick
587 * Caller must ensure we don't call this with other virtqueue
588 * operations at the same time (except where noted).
590 * Returns false if kick failed, otherwise true.
592 bool virtqueue_kick(struct virtqueue *vq)
594 if (virtqueue_kick_prepare(vq))
595 return virtqueue_notify(vq);
598 EXPORT_SYMBOL_GPL(virtqueue_kick);
600 static void detach_buf(struct vring_virtqueue *vq, unsigned int head)
603 u16 nextflag = cpu_to_virtio16(vq->vq.vdev, VRING_DESC_F_NEXT);
605 /* Clear data ptr. */
606 vq->desc_state[head].data = NULL;
608 /* Put back on free list: unmap first-level descriptors and find end */
611 while (vq->vring.desc[i].flags & nextflag) {
612 vring_unmap_one(vq, &vq->vring.desc[i]);
613 i = virtio16_to_cpu(vq->vq.vdev, vq->vring.desc[i].next);
617 vring_unmap_one(vq, &vq->vring.desc[i]);
618 vq->vring.desc[i].next = cpu_to_virtio16(vq->vq.vdev, vq->free_head);
619 vq->free_head = head;
621 /* Plus final descriptor */
624 /* Free the indirect table, if any, now that it's unmapped. */
625 if (vq->desc_state[head].indir_desc) {
626 struct vring_desc *indir_desc = vq->desc_state[head].indir_desc;
627 u32 len = virtio32_to_cpu(vq->vq.vdev, vq->vring.desc[head].len);
629 BUG_ON(!(vq->vring.desc[head].flags &
630 cpu_to_virtio16(vq->vq.vdev, VRING_DESC_F_INDIRECT)));
631 BUG_ON(len == 0 || len % sizeof(struct vring_desc));
633 for (j = 0; j < len / sizeof(struct vring_desc); j++)
634 vring_unmap_one(vq, &indir_desc[j]);
636 kfree(vq->desc_state[head].indir_desc);
637 vq->desc_state[head].indir_desc = NULL;
641 static inline bool more_used(const struct vring_virtqueue *vq)
643 return vq->last_used_idx != virtio16_to_cpu(vq->vq.vdev, vq->vring.used->idx);
647 * virtqueue_get_buf - get the next used buffer
648 * @vq: the struct virtqueue we're talking about.
649 * @len: the length written into the buffer
651 * If the driver wrote data into the buffer, @len will be set to the
652 * amount written. This means you don't need to clear the buffer
653 * beforehand to ensure there's no data leakage in the case of short
656 * Caller must ensure we don't call this with other virtqueue
657 * operations at the same time (except where noted).
659 * Returns NULL if there are no used buffers, or the "data" token
660 * handed to virtqueue_add_*().
662 void *virtqueue_get_buf(struct virtqueue *_vq, unsigned int *len)
664 struct vring_virtqueue *vq = to_vvq(_vq);
671 if (unlikely(vq->broken)) {
676 if (!more_used(vq)) {
677 pr_debug("No more buffers in queue\n");
682 /* Only get used array entries after they have been exposed by host. */
683 virtio_rmb(vq->weak_barriers);
685 last_used = (vq->last_used_idx & (vq->vring.num - 1));
686 i = virtio32_to_cpu(_vq->vdev, vq->vring.used->ring[last_used].id);
687 *len = virtio32_to_cpu(_vq->vdev, vq->vring.used->ring[last_used].len);
689 if (unlikely(i >= vq->vring.num)) {
690 BAD_RING(vq, "id %u out of range\n", i);
693 if (unlikely(!vq->desc_state[i].data)) {
694 BAD_RING(vq, "id %u is not a head!\n", i);
698 /* detach_buf clears data, so grab it now. */
699 ret = vq->desc_state[i].data;
702 /* If we expect an interrupt for the next entry, tell host
703 * by writing event index and flush out the write before
704 * the read in the next get_buf call. */
705 if (!(vq->avail_flags_shadow & VRING_AVAIL_F_NO_INTERRUPT))
706 virtio_store_mb(vq->weak_barriers,
707 &vring_used_event(&vq->vring),
708 cpu_to_virtio16(_vq->vdev, vq->last_used_idx));
711 vq->last_add_time_valid = false;
717 EXPORT_SYMBOL_GPL(virtqueue_get_buf);
720 * virtqueue_disable_cb - disable callbacks
721 * @vq: the struct virtqueue we're talking about.
723 * Note that this is not necessarily synchronous, hence unreliable and only
724 * useful as an optimization.
726 * Unlike other operations, this need not be serialized.
728 void virtqueue_disable_cb(struct virtqueue *_vq)
730 struct vring_virtqueue *vq = to_vvq(_vq);
732 if (!(vq->avail_flags_shadow & VRING_AVAIL_F_NO_INTERRUPT)) {
733 vq->avail_flags_shadow |= VRING_AVAIL_F_NO_INTERRUPT;
734 vq->vring.avail->flags = cpu_to_virtio16(_vq->vdev, vq->avail_flags_shadow);
738 EXPORT_SYMBOL_GPL(virtqueue_disable_cb);
741 * virtqueue_enable_cb_prepare - restart callbacks after disable_cb
742 * @vq: the struct virtqueue we're talking about.
744 * This re-enables callbacks; it returns current queue state
745 * in an opaque unsigned value. This value should be later tested by
746 * virtqueue_poll, to detect a possible race between the driver checking for
747 * more work, and enabling callbacks.
749 * Caller must ensure we don't call this with other virtqueue
750 * operations at the same time (except where noted).
752 unsigned virtqueue_enable_cb_prepare(struct virtqueue *_vq)
754 struct vring_virtqueue *vq = to_vvq(_vq);
759 /* We optimistically turn back on interrupts, then check if there was
761 /* Depending on the VIRTIO_RING_F_EVENT_IDX feature, we need to
762 * either clear the flags bit or point the event index at the next
763 * entry. Always do both to keep code simple. */
764 if (vq->avail_flags_shadow & VRING_AVAIL_F_NO_INTERRUPT) {
765 vq->avail_flags_shadow &= ~VRING_AVAIL_F_NO_INTERRUPT;
766 vq->vring.avail->flags = cpu_to_virtio16(_vq->vdev, vq->avail_flags_shadow);
768 vring_used_event(&vq->vring) = cpu_to_virtio16(_vq->vdev, last_used_idx = vq->last_used_idx);
770 return last_used_idx;
772 EXPORT_SYMBOL_GPL(virtqueue_enable_cb_prepare);
775 * virtqueue_poll - query pending used buffers
776 * @vq: the struct virtqueue we're talking about.
777 * @last_used_idx: virtqueue state (from call to virtqueue_enable_cb_prepare).
779 * Returns "true" if there are pending used buffers in the queue.
781 * This does not need to be serialized.
783 bool virtqueue_poll(struct virtqueue *_vq, unsigned last_used_idx)
785 struct vring_virtqueue *vq = to_vvq(_vq);
787 virtio_mb(vq->weak_barriers);
788 return (u16)last_used_idx != virtio16_to_cpu(_vq->vdev, vq->vring.used->idx);
790 EXPORT_SYMBOL_GPL(virtqueue_poll);
793 * virtqueue_enable_cb - restart callbacks after disable_cb.
794 * @vq: the struct virtqueue we're talking about.
796 * This re-enables callbacks; it returns "false" if there are pending
797 * buffers in the queue, to detect a possible race between the driver
798 * checking for more work, and enabling callbacks.
800 * Caller must ensure we don't call this with other virtqueue
801 * operations at the same time (except where noted).
803 bool virtqueue_enable_cb(struct virtqueue *_vq)
805 unsigned last_used_idx = virtqueue_enable_cb_prepare(_vq);
806 return !virtqueue_poll(_vq, last_used_idx);
808 EXPORT_SYMBOL_GPL(virtqueue_enable_cb);
811 * virtqueue_enable_cb_delayed - restart callbacks after disable_cb.
812 * @vq: the struct virtqueue we're talking about.
814 * This re-enables callbacks but hints to the other side to delay
815 * interrupts until most of the available buffers have been processed;
816 * it returns "false" if there are many pending buffers in the queue,
817 * to detect a possible race between the driver checking for more work,
818 * and enabling callbacks.
820 * Caller must ensure we don't call this with other virtqueue
821 * operations at the same time (except where noted).
823 bool virtqueue_enable_cb_delayed(struct virtqueue *_vq)
825 struct vring_virtqueue *vq = to_vvq(_vq);
830 /* We optimistically turn back on interrupts, then check if there was
832 /* Depending on the VIRTIO_RING_F_USED_EVENT_IDX feature, we need to
833 * either clear the flags bit or point the event index at the next
834 * entry. Always do both to keep code simple. */
835 if (vq->avail_flags_shadow & VRING_AVAIL_F_NO_INTERRUPT) {
836 vq->avail_flags_shadow &= ~VRING_AVAIL_F_NO_INTERRUPT;
837 vq->vring.avail->flags = cpu_to_virtio16(_vq->vdev, vq->avail_flags_shadow);
839 /* TODO: tune this threshold */
840 bufs = (u16)(vq->avail_idx_shadow - vq->last_used_idx) * 3 / 4;
842 virtio_store_mb(vq->weak_barriers,
843 &vring_used_event(&vq->vring),
844 cpu_to_virtio16(_vq->vdev, vq->last_used_idx + bufs));
846 if (unlikely((u16)(virtio16_to_cpu(_vq->vdev, vq->vring.used->idx) - vq->last_used_idx) > bufs)) {
854 EXPORT_SYMBOL_GPL(virtqueue_enable_cb_delayed);
857 * virtqueue_detach_unused_buf - detach first unused buffer
858 * @vq: the struct virtqueue we're talking about.
860 * Returns NULL or the "data" token handed to virtqueue_add_*().
861 * This is not valid on an active queue; it is useful only for device
864 void *virtqueue_detach_unused_buf(struct virtqueue *_vq)
866 struct vring_virtqueue *vq = to_vvq(_vq);
872 for (i = 0; i < vq->vring.num; i++) {
873 if (!vq->desc_state[i].data)
875 /* detach_buf clears data, so grab it now. */
876 buf = vq->desc_state[i].data;
878 vq->avail_idx_shadow--;
879 vq->vring.avail->idx = cpu_to_virtio16(_vq->vdev, vq->avail_idx_shadow);
883 /* That should have freed everything. */
884 BUG_ON(vq->vq.num_free != vq->vring.num);
889 EXPORT_SYMBOL_GPL(virtqueue_detach_unused_buf);
891 irqreturn_t vring_interrupt(int irq, void *_vq)
893 struct vring_virtqueue *vq = to_vvq(_vq);
895 if (!more_used(vq)) {
896 pr_debug("virtqueue interrupt with no work for %p\n", vq);
900 if (unlikely(vq->broken))
903 pr_debug("virtqueue callback for %p (%p)\n", vq, vq->vq.callback);
905 vq->vq.callback(&vq->vq);
909 EXPORT_SYMBOL_GPL(vring_interrupt);
911 struct virtqueue *__vring_new_virtqueue(unsigned int index,
913 struct virtio_device *vdev,
915 bool (*notify)(struct virtqueue *),
916 void (*callback)(struct virtqueue *),
920 struct vring_virtqueue *vq;
922 vq = kmalloc(sizeof(*vq) + vring.num * sizeof(struct vring_desc_state),
928 vq->vq.callback = callback;
931 vq->vq.num_free = vring.num;
932 vq->vq.index = index;
933 vq->we_own_ring = false;
934 vq->queue_dma_addr = 0;
935 vq->queue_size_in_bytes = 0;
937 vq->weak_barriers = weak_barriers;
939 vq->last_used_idx = 0;
940 vq->avail_flags_shadow = 0;
941 vq->avail_idx_shadow = 0;
943 list_add_tail(&vq->vq.list, &vdev->vqs);
946 vq->last_add_time_valid = false;
949 vq->indirect = virtio_has_feature(vdev, VIRTIO_RING_F_INDIRECT_DESC);
950 vq->event = virtio_has_feature(vdev, VIRTIO_RING_F_EVENT_IDX);
952 /* No callback? Tell other side not to bother us. */
954 vq->avail_flags_shadow |= VRING_AVAIL_F_NO_INTERRUPT;
955 vq->vring.avail->flags = cpu_to_virtio16(vdev, vq->avail_flags_shadow);
958 /* Put everything in free lists. */
960 for (i = 0; i < vring.num-1; i++)
961 vq->vring.desc[i].next = cpu_to_virtio16(vdev, i + 1);
962 memset(vq->desc_state, 0, vring.num * sizeof(struct vring_desc_state));
966 EXPORT_SYMBOL_GPL(__vring_new_virtqueue);
968 static void *vring_alloc_queue(struct virtio_device *vdev, size_t size,
969 dma_addr_t *dma_handle, gfp_t flag)
971 if (vring_use_dma_api(vdev)) {
972 return dma_alloc_coherent(vdev->dev.parent, size,
975 void *queue = alloc_pages_exact(PAGE_ALIGN(size), flag);
977 phys_addr_t phys_addr = virt_to_phys(queue);
978 *dma_handle = (dma_addr_t)phys_addr;
981 * Sanity check: make sure we dind't truncate
982 * the address. The only arches I can find that
983 * have 64-bit phys_addr_t but 32-bit dma_addr_t
984 * are certain non-highmem MIPS and x86
985 * configurations, but these configurations
986 * should never allocate physical pages above 32
987 * bits, so this is fine. Just in case, throw a
988 * warning and abort if we end up with an
989 * unrepresentable address.
991 if (WARN_ON_ONCE(*dma_handle != phys_addr)) {
992 free_pages_exact(queue, PAGE_ALIGN(size));
1000 static void vring_free_queue(struct virtio_device *vdev, size_t size,
1001 void *queue, dma_addr_t dma_handle)
1003 if (vring_use_dma_api(vdev)) {
1004 dma_free_coherent(vdev->dev.parent, size, queue, dma_handle);
1006 free_pages_exact(queue, PAGE_ALIGN(size));
1010 struct virtqueue *vring_create_virtqueue(
1013 unsigned int vring_align,
1014 struct virtio_device *vdev,
1016 bool may_reduce_num,
1017 bool (*notify)(struct virtqueue *),
1018 void (*callback)(struct virtqueue *),
1021 struct virtqueue *vq;
1023 dma_addr_t dma_addr;
1024 size_t queue_size_in_bytes;
1027 /* We assume num is a power of 2. */
1028 if (num & (num - 1)) {
1029 dev_warn(&vdev->dev, "Bad virtqueue length %u\n", num);
1033 /* TODO: allocate each queue chunk individually */
1034 for (; num && vring_size(num, vring_align) > PAGE_SIZE; num /= 2) {
1035 queue = vring_alloc_queue(vdev, vring_size(num, vring_align),
1037 GFP_KERNEL|__GFP_NOWARN|__GFP_ZERO);
1046 /* Try to get a single page. You are my only hope! */
1047 queue = vring_alloc_queue(vdev, vring_size(num, vring_align),
1048 &dma_addr, GFP_KERNEL|__GFP_ZERO);
1053 queue_size_in_bytes = vring_size(num, vring_align);
1054 vring_init(&vring, num, queue, vring_align);
1056 vq = __vring_new_virtqueue(index, vring, vdev, weak_barriers,
1057 notify, callback, name);
1059 vring_free_queue(vdev, queue_size_in_bytes, queue,
1064 to_vvq(vq)->queue_dma_addr = dma_addr;
1065 to_vvq(vq)->queue_size_in_bytes = queue_size_in_bytes;
1066 to_vvq(vq)->we_own_ring = true;
1070 EXPORT_SYMBOL_GPL(vring_create_virtqueue);
1072 struct virtqueue *vring_new_virtqueue(unsigned int index,
1074 unsigned int vring_align,
1075 struct virtio_device *vdev,
1078 bool (*notify)(struct virtqueue *vq),
1079 void (*callback)(struct virtqueue *vq),
1083 vring_init(&vring, num, pages, vring_align);
1084 return __vring_new_virtqueue(index, vring, vdev, weak_barriers,
1085 notify, callback, name);
1087 EXPORT_SYMBOL_GPL(vring_new_virtqueue);
1089 void vring_del_virtqueue(struct virtqueue *_vq)
1091 struct vring_virtqueue *vq = to_vvq(_vq);
1093 if (vq->we_own_ring) {
1094 vring_free_queue(vq->vq.vdev, vq->queue_size_in_bytes,
1095 vq->vring.desc, vq->queue_dma_addr);
1097 list_del(&_vq->list);
1100 EXPORT_SYMBOL_GPL(vring_del_virtqueue);
1102 /* Manipulates transport-specific feature bits. */
1103 void vring_transport_features(struct virtio_device *vdev)
1107 for (i = VIRTIO_TRANSPORT_F_START; i < VIRTIO_TRANSPORT_F_END; i++) {
1109 case VIRTIO_RING_F_INDIRECT_DESC:
1111 case VIRTIO_RING_F_EVENT_IDX:
1113 case VIRTIO_F_VERSION_1:
1115 case VIRTIO_F_IOMMU_PLATFORM:
1118 /* We don't understand this bit. */
1119 __virtio_clear_bit(vdev, i);
1123 EXPORT_SYMBOL_GPL(vring_transport_features);
1126 * virtqueue_get_vring_size - return the size of the virtqueue's vring
1127 * @vq: the struct virtqueue containing the vring of interest.
1129 * Returns the size of the vring. This is mainly used for boasting to
1130 * userspace. Unlike other operations, this need not be serialized.
1132 unsigned int virtqueue_get_vring_size(struct virtqueue *_vq)
1135 struct vring_virtqueue *vq = to_vvq(_vq);
1137 return vq->vring.num;
1139 EXPORT_SYMBOL_GPL(virtqueue_get_vring_size);
1141 bool virtqueue_is_broken(struct virtqueue *_vq)
1143 struct vring_virtqueue *vq = to_vvq(_vq);
1147 EXPORT_SYMBOL_GPL(virtqueue_is_broken);
1150 * This should prevent the device from being used, allowing drivers to
1151 * recover. You may need to grab appropriate locks to flush.
1153 void virtio_break_device(struct virtio_device *dev)
1155 struct virtqueue *_vq;
1157 list_for_each_entry(_vq, &dev->vqs, list) {
1158 struct vring_virtqueue *vq = to_vvq(_vq);
1162 EXPORT_SYMBOL_GPL(virtio_break_device);
1164 dma_addr_t virtqueue_get_desc_addr(struct virtqueue *_vq)
1166 struct vring_virtqueue *vq = to_vvq(_vq);
1168 BUG_ON(!vq->we_own_ring);
1170 return vq->queue_dma_addr;
1172 EXPORT_SYMBOL_GPL(virtqueue_get_desc_addr);
1174 dma_addr_t virtqueue_get_avail_addr(struct virtqueue *_vq)
1176 struct vring_virtqueue *vq = to_vvq(_vq);
1178 BUG_ON(!vq->we_own_ring);
1180 return vq->queue_dma_addr +
1181 ((char *)vq->vring.avail - (char *)vq->vring.desc);
1183 EXPORT_SYMBOL_GPL(virtqueue_get_avail_addr);
1185 dma_addr_t virtqueue_get_used_addr(struct virtqueue *_vq)
1187 struct vring_virtqueue *vq = to_vvq(_vq);
1189 BUG_ON(!vq->we_own_ring);
1191 return vq->queue_dma_addr +
1192 ((char *)vq->vring.used - (char *)vq->vring.desc);
1194 EXPORT_SYMBOL_GPL(virtqueue_get_used_addr);
1196 const struct vring *virtqueue_get_vring(struct virtqueue *vq)
1198 return &to_vvq(vq)->vring;
1200 EXPORT_SYMBOL_GPL(virtqueue_get_vring);
1202 MODULE_LICENSE("GPL");