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. */
334 for (n = 0; n < out_sgs; n++) {
335 for (sg = sgs[n]; sg; sg = sg_next(sg)) {
336 dma_addr_t addr = vring_map_one_sg(vq, sg, DMA_TO_DEVICE);
337 if (vring_mapping_error(vq, addr))
340 desc[i].flags = cpu_to_virtio16(_vq->vdev, VRING_DESC_F_NEXT);
341 desc[i].addr = cpu_to_virtio64(_vq->vdev, addr);
342 desc[i].len = cpu_to_virtio32(_vq->vdev, sg->length);
344 i = virtio16_to_cpu(_vq->vdev, desc[i].next);
347 for (; n < (out_sgs + in_sgs); n++) {
348 for (sg = sgs[n]; sg; sg = sg_next(sg)) {
349 dma_addr_t addr = vring_map_one_sg(vq, sg, DMA_FROM_DEVICE);
350 if (vring_mapping_error(vq, addr))
353 desc[i].flags = cpu_to_virtio16(_vq->vdev, VRING_DESC_F_NEXT | VRING_DESC_F_WRITE);
354 desc[i].addr = cpu_to_virtio64(_vq->vdev, addr);
355 desc[i].len = cpu_to_virtio32(_vq->vdev, sg->length);
357 i = virtio16_to_cpu(_vq->vdev, desc[i].next);
360 /* Last one doesn't continue. */
361 desc[prev].flags &= cpu_to_virtio16(_vq->vdev, ~VRING_DESC_F_NEXT);
364 /* Now that the indirect table is filled in, map it. */
365 dma_addr_t addr = vring_map_single(
366 vq, desc, total_sg * sizeof(struct vring_desc),
368 if (vring_mapping_error(vq, addr))
371 vq->vring.desc[head].flags = cpu_to_virtio16(_vq->vdev, VRING_DESC_F_INDIRECT);
372 vq->vring.desc[head].addr = cpu_to_virtio64(_vq->vdev, addr);
374 vq->vring.desc[head].len = cpu_to_virtio32(_vq->vdev, total_sg * sizeof(struct vring_desc));
377 /* We're using some buffers from the free list. */
378 vq->vq.num_free -= descs_used;
380 /* Update free pointer */
382 vq->free_head = virtio16_to_cpu(_vq->vdev, vq->vring.desc[head].next);
386 /* Store token and indirect buffer state. */
387 vq->desc_state[head].data = data;
389 vq->desc_state[head].indir_desc = desc;
391 /* Put entry in available array (but don't update avail->idx until they
393 avail = vq->avail_idx_shadow & (vq->vring.num - 1);
394 vq->vring.avail->ring[avail] = cpu_to_virtio16(_vq->vdev, head);
396 /* Descriptors and available array need to be set before we expose the
397 * new available array entries. */
398 virtio_wmb(vq->weak_barriers);
399 vq->avail_idx_shadow++;
400 vq->vring.avail->idx = cpu_to_virtio16(_vq->vdev, vq->avail_idx_shadow);
403 pr_debug("Added buffer head %i to %p\n", head, vq);
406 /* This is very unlikely, but theoretically possible. Kick
408 if (unlikely(vq->num_added == (1 << 16) - 1))
417 for (n = 0; n < total_sg; n++) {
420 vring_unmap_one(vq, &desc[i]);
421 i = vq->vring.desc[i].next;
424 vq->vq.num_free += total_sg;
433 * virtqueue_add_sgs - expose buffers to other end
434 * @vq: the struct virtqueue we're talking about.
435 * @sgs: array of terminated scatterlists.
436 * @out_num: the number of scatterlists readable by other side
437 * @in_num: the number of scatterlists which are writable (after readable ones)
438 * @data: the token identifying the buffer.
439 * @gfp: how to do memory allocations (if necessary).
441 * Caller must ensure we don't call this with other virtqueue operations
442 * at the same time (except where noted).
444 * Returns zero or a negative error (ie. ENOSPC, ENOMEM, EIO).
446 int virtqueue_add_sgs(struct virtqueue *_vq,
447 struct scatterlist *sgs[],
448 unsigned int out_sgs,
453 unsigned int i, total_sg = 0;
455 /* Count them first. */
456 for (i = 0; i < out_sgs + in_sgs; i++) {
457 struct scatterlist *sg;
458 for (sg = sgs[i]; sg; sg = sg_next(sg))
461 return virtqueue_add(_vq, sgs, total_sg, out_sgs, in_sgs, data, gfp);
463 EXPORT_SYMBOL_GPL(virtqueue_add_sgs);
466 * virtqueue_add_outbuf - expose output buffers to other end
467 * @vq: the struct virtqueue we're talking about.
468 * @sg: scatterlist (must be well-formed and terminated!)
469 * @num: the number of entries in @sg readable by other side
470 * @data: the token identifying the buffer.
471 * @gfp: how to do memory allocations (if necessary).
473 * Caller must ensure we don't call this with other virtqueue operations
474 * at the same time (except where noted).
476 * Returns zero or a negative error (ie. ENOSPC, ENOMEM, EIO).
478 int virtqueue_add_outbuf(struct virtqueue *vq,
479 struct scatterlist *sg, unsigned int num,
483 return virtqueue_add(vq, &sg, num, 1, 0, data, gfp);
485 EXPORT_SYMBOL_GPL(virtqueue_add_outbuf);
488 * virtqueue_add_inbuf - expose input buffers to other end
489 * @vq: the struct virtqueue we're talking about.
490 * @sg: scatterlist (must be well-formed and terminated!)
491 * @num: the number of entries in @sg writable by other side
492 * @data: the token identifying the buffer.
493 * @gfp: how to do memory allocations (if necessary).
495 * Caller must ensure we don't call this with other virtqueue operations
496 * at the same time (except where noted).
498 * Returns zero or a negative error (ie. ENOSPC, ENOMEM, EIO).
500 int virtqueue_add_inbuf(struct virtqueue *vq,
501 struct scatterlist *sg, unsigned int num,
505 return virtqueue_add(vq, &sg, num, 0, 1, data, gfp);
507 EXPORT_SYMBOL_GPL(virtqueue_add_inbuf);
510 * virtqueue_kick_prepare - first half of split virtqueue_kick call.
511 * @vq: the struct virtqueue
513 * Instead of virtqueue_kick(), you can do:
514 * if (virtqueue_kick_prepare(vq))
515 * virtqueue_notify(vq);
517 * This is sometimes useful because the virtqueue_kick_prepare() needs
518 * to be serialized, but the actual virtqueue_notify() call does not.
520 bool virtqueue_kick_prepare(struct virtqueue *_vq)
522 struct vring_virtqueue *vq = to_vvq(_vq);
527 /* We need to expose available array entries before checking avail
529 virtio_mb(vq->weak_barriers);
531 old = vq->avail_idx_shadow - vq->num_added;
532 new = vq->avail_idx_shadow;
536 if (vq->last_add_time_valid) {
537 WARN_ON(ktime_to_ms(ktime_sub(ktime_get(),
538 vq->last_add_time)) > 100);
540 vq->last_add_time_valid = false;
544 needs_kick = vring_need_event(virtio16_to_cpu(_vq->vdev, vring_avail_event(&vq->vring)),
547 needs_kick = !(vq->vring.used->flags & cpu_to_virtio16(_vq->vdev, VRING_USED_F_NO_NOTIFY));
552 EXPORT_SYMBOL_GPL(virtqueue_kick_prepare);
555 * virtqueue_notify - second half of split virtqueue_kick call.
556 * @vq: the struct virtqueue
558 * This does not need to be serialized.
560 * Returns false if host notify failed or queue is broken, otherwise true.
562 bool virtqueue_notify(struct virtqueue *_vq)
564 struct vring_virtqueue *vq = to_vvq(_vq);
566 if (unlikely(vq->broken))
569 /* Prod other side to tell it about changes. */
570 if (!vq->notify(_vq)) {
576 EXPORT_SYMBOL_GPL(virtqueue_notify);
579 * virtqueue_kick - update after add_buf
580 * @vq: the struct virtqueue
582 * After one or more virtqueue_add_* calls, invoke this to kick
585 * Caller must ensure we don't call this with other virtqueue
586 * operations at the same time (except where noted).
588 * Returns false if kick failed, otherwise true.
590 bool virtqueue_kick(struct virtqueue *vq)
592 if (virtqueue_kick_prepare(vq))
593 return virtqueue_notify(vq);
596 EXPORT_SYMBOL_GPL(virtqueue_kick);
598 static void detach_buf(struct vring_virtqueue *vq, unsigned int head)
601 u16 nextflag = cpu_to_virtio16(vq->vq.vdev, VRING_DESC_F_NEXT);
603 /* Clear data ptr. */
604 vq->desc_state[head].data = NULL;
606 /* Put back on free list: unmap first-level descriptors and find end */
609 while (vq->vring.desc[i].flags & nextflag) {
610 vring_unmap_one(vq, &vq->vring.desc[i]);
611 i = virtio16_to_cpu(vq->vq.vdev, vq->vring.desc[i].next);
615 vring_unmap_one(vq, &vq->vring.desc[i]);
616 vq->vring.desc[i].next = cpu_to_virtio16(vq->vq.vdev, vq->free_head);
617 vq->free_head = head;
619 /* Plus final descriptor */
622 /* Free the indirect table, if any, now that it's unmapped. */
623 if (vq->desc_state[head].indir_desc) {
624 struct vring_desc *indir_desc = vq->desc_state[head].indir_desc;
625 u32 len = virtio32_to_cpu(vq->vq.vdev, vq->vring.desc[head].len);
627 BUG_ON(!(vq->vring.desc[head].flags &
628 cpu_to_virtio16(vq->vq.vdev, VRING_DESC_F_INDIRECT)));
629 BUG_ON(len == 0 || len % sizeof(struct vring_desc));
631 for (j = 0; j < len / sizeof(struct vring_desc); j++)
632 vring_unmap_one(vq, &indir_desc[j]);
634 kfree(vq->desc_state[head].indir_desc);
635 vq->desc_state[head].indir_desc = NULL;
639 static inline bool more_used(const struct vring_virtqueue *vq)
641 return vq->last_used_idx != virtio16_to_cpu(vq->vq.vdev, vq->vring.used->idx);
645 * virtqueue_get_buf - get the next used buffer
646 * @vq: the struct virtqueue we're talking about.
647 * @len: the length written into the buffer
649 * If the driver wrote data into the buffer, @len will be set to the
650 * amount written. This means you don't need to clear the buffer
651 * beforehand to ensure there's no data leakage in the case of short
654 * Caller must ensure we don't call this with other virtqueue
655 * operations at the same time (except where noted).
657 * Returns NULL if there are no used buffers, or the "data" token
658 * handed to virtqueue_add_*().
660 void *virtqueue_get_buf(struct virtqueue *_vq, unsigned int *len)
662 struct vring_virtqueue *vq = to_vvq(_vq);
669 if (unlikely(vq->broken)) {
674 if (!more_used(vq)) {
675 pr_debug("No more buffers in queue\n");
680 /* Only get used array entries after they have been exposed by host. */
681 virtio_rmb(vq->weak_barriers);
683 last_used = (vq->last_used_idx & (vq->vring.num - 1));
684 i = virtio32_to_cpu(_vq->vdev, vq->vring.used->ring[last_used].id);
685 *len = virtio32_to_cpu(_vq->vdev, vq->vring.used->ring[last_used].len);
687 if (unlikely(i >= vq->vring.num)) {
688 BAD_RING(vq, "id %u out of range\n", i);
691 if (unlikely(!vq->desc_state[i].data)) {
692 BAD_RING(vq, "id %u is not a head!\n", i);
696 /* detach_buf clears data, so grab it now. */
697 ret = vq->desc_state[i].data;
700 /* If we expect an interrupt for the next entry, tell host
701 * by writing event index and flush out the write before
702 * the read in the next get_buf call. */
703 if (!(vq->avail_flags_shadow & VRING_AVAIL_F_NO_INTERRUPT))
704 virtio_store_mb(vq->weak_barriers,
705 &vring_used_event(&vq->vring),
706 cpu_to_virtio16(_vq->vdev, vq->last_used_idx));
709 vq->last_add_time_valid = false;
715 EXPORT_SYMBOL_GPL(virtqueue_get_buf);
718 * virtqueue_disable_cb - disable callbacks
719 * @vq: the struct virtqueue we're talking about.
721 * Note that this is not necessarily synchronous, hence unreliable and only
722 * useful as an optimization.
724 * Unlike other operations, this need not be serialized.
726 void virtqueue_disable_cb(struct virtqueue *_vq)
728 struct vring_virtqueue *vq = to_vvq(_vq);
730 if (!(vq->avail_flags_shadow & VRING_AVAIL_F_NO_INTERRUPT)) {
731 vq->avail_flags_shadow |= VRING_AVAIL_F_NO_INTERRUPT;
732 vq->vring.avail->flags = cpu_to_virtio16(_vq->vdev, vq->avail_flags_shadow);
736 EXPORT_SYMBOL_GPL(virtqueue_disable_cb);
739 * virtqueue_enable_cb_prepare - restart callbacks after disable_cb
740 * @vq: the struct virtqueue we're talking about.
742 * This re-enables callbacks; it returns current queue state
743 * in an opaque unsigned value. This value should be later tested by
744 * virtqueue_poll, to detect a possible race between the driver checking for
745 * more work, and enabling callbacks.
747 * Caller must ensure we don't call this with other virtqueue
748 * operations at the same time (except where noted).
750 unsigned virtqueue_enable_cb_prepare(struct virtqueue *_vq)
752 struct vring_virtqueue *vq = to_vvq(_vq);
757 /* We optimistically turn back on interrupts, then check if there was
759 /* Depending on the VIRTIO_RING_F_EVENT_IDX feature, we need to
760 * either clear the flags bit or point the event index at the next
761 * entry. Always do both to keep code simple. */
762 if (vq->avail_flags_shadow & VRING_AVAIL_F_NO_INTERRUPT) {
763 vq->avail_flags_shadow &= ~VRING_AVAIL_F_NO_INTERRUPT;
764 vq->vring.avail->flags = cpu_to_virtio16(_vq->vdev, vq->avail_flags_shadow);
766 vring_used_event(&vq->vring) = cpu_to_virtio16(_vq->vdev, last_used_idx = vq->last_used_idx);
768 return last_used_idx;
770 EXPORT_SYMBOL_GPL(virtqueue_enable_cb_prepare);
773 * virtqueue_poll - query pending used buffers
774 * @vq: the struct virtqueue we're talking about.
775 * @last_used_idx: virtqueue state (from call to virtqueue_enable_cb_prepare).
777 * Returns "true" if there are pending used buffers in the queue.
779 * This does not need to be serialized.
781 bool virtqueue_poll(struct virtqueue *_vq, unsigned last_used_idx)
783 struct vring_virtqueue *vq = to_vvq(_vq);
785 virtio_mb(vq->weak_barriers);
786 return (u16)last_used_idx != virtio16_to_cpu(_vq->vdev, vq->vring.used->idx);
788 EXPORT_SYMBOL_GPL(virtqueue_poll);
791 * virtqueue_enable_cb - restart callbacks after disable_cb.
792 * @vq: the struct virtqueue we're talking about.
794 * This re-enables callbacks; it returns "false" if there are pending
795 * buffers in the queue, to detect a possible race between the driver
796 * checking for more work, and enabling callbacks.
798 * Caller must ensure we don't call this with other virtqueue
799 * operations at the same time (except where noted).
801 bool virtqueue_enable_cb(struct virtqueue *_vq)
803 unsigned last_used_idx = virtqueue_enable_cb_prepare(_vq);
804 return !virtqueue_poll(_vq, last_used_idx);
806 EXPORT_SYMBOL_GPL(virtqueue_enable_cb);
809 * virtqueue_enable_cb_delayed - restart callbacks after disable_cb.
810 * @vq: the struct virtqueue we're talking about.
812 * This re-enables callbacks but hints to the other side to delay
813 * interrupts until most of the available buffers have been processed;
814 * it returns "false" if there are many pending buffers in the queue,
815 * to detect a possible race between the driver checking for more work,
816 * and enabling callbacks.
818 * Caller must ensure we don't call this with other virtqueue
819 * operations at the same time (except where noted).
821 bool virtqueue_enable_cb_delayed(struct virtqueue *_vq)
823 struct vring_virtqueue *vq = to_vvq(_vq);
828 /* We optimistically turn back on interrupts, then check if there was
830 /* Depending on the VIRTIO_RING_F_USED_EVENT_IDX feature, we need to
831 * either clear the flags bit or point the event index at the next
832 * entry. Always do both to keep code simple. */
833 if (vq->avail_flags_shadow & VRING_AVAIL_F_NO_INTERRUPT) {
834 vq->avail_flags_shadow &= ~VRING_AVAIL_F_NO_INTERRUPT;
835 vq->vring.avail->flags = cpu_to_virtio16(_vq->vdev, vq->avail_flags_shadow);
837 /* TODO: tune this threshold */
838 bufs = (u16)(vq->avail_idx_shadow - vq->last_used_idx) * 3 / 4;
840 virtio_store_mb(vq->weak_barriers,
841 &vring_used_event(&vq->vring),
842 cpu_to_virtio16(_vq->vdev, vq->last_used_idx + bufs));
844 if (unlikely((u16)(virtio16_to_cpu(_vq->vdev, vq->vring.used->idx) - vq->last_used_idx) > bufs)) {
852 EXPORT_SYMBOL_GPL(virtqueue_enable_cb_delayed);
855 * virtqueue_detach_unused_buf - detach first unused buffer
856 * @vq: the struct virtqueue we're talking about.
858 * Returns NULL or the "data" token handed to virtqueue_add_*().
859 * This is not valid on an active queue; it is useful only for device
862 void *virtqueue_detach_unused_buf(struct virtqueue *_vq)
864 struct vring_virtqueue *vq = to_vvq(_vq);
870 for (i = 0; i < vq->vring.num; i++) {
871 if (!vq->desc_state[i].data)
873 /* detach_buf clears data, so grab it now. */
874 buf = vq->desc_state[i].data;
876 vq->avail_idx_shadow--;
877 vq->vring.avail->idx = cpu_to_virtio16(_vq->vdev, vq->avail_idx_shadow);
881 /* That should have freed everything. */
882 BUG_ON(vq->vq.num_free != vq->vring.num);
887 EXPORT_SYMBOL_GPL(virtqueue_detach_unused_buf);
889 irqreturn_t vring_interrupt(int irq, void *_vq)
891 struct vring_virtqueue *vq = to_vvq(_vq);
893 if (!more_used(vq)) {
894 pr_debug("virtqueue interrupt with no work for %p\n", vq);
898 if (unlikely(vq->broken))
901 pr_debug("virtqueue callback for %p (%p)\n", vq, vq->vq.callback);
903 vq->vq.callback(&vq->vq);
907 EXPORT_SYMBOL_GPL(vring_interrupt);
909 struct virtqueue *__vring_new_virtqueue(unsigned int index,
911 struct virtio_device *vdev,
913 bool (*notify)(struct virtqueue *),
914 void (*callback)(struct virtqueue *),
918 struct vring_virtqueue *vq;
920 vq = kmalloc(sizeof(*vq) + vring.num * sizeof(struct vring_desc_state),
926 vq->vq.callback = callback;
929 vq->vq.num_free = vring.num;
930 vq->vq.index = index;
931 vq->we_own_ring = false;
932 vq->queue_dma_addr = 0;
933 vq->queue_size_in_bytes = 0;
935 vq->weak_barriers = weak_barriers;
937 vq->last_used_idx = 0;
938 vq->avail_flags_shadow = 0;
939 vq->avail_idx_shadow = 0;
941 list_add_tail(&vq->vq.list, &vdev->vqs);
944 vq->last_add_time_valid = false;
947 vq->indirect = virtio_has_feature(vdev, VIRTIO_RING_F_INDIRECT_DESC);
948 vq->event = virtio_has_feature(vdev, VIRTIO_RING_F_EVENT_IDX);
950 /* No callback? Tell other side not to bother us. */
952 vq->avail_flags_shadow |= VRING_AVAIL_F_NO_INTERRUPT;
953 vq->vring.avail->flags = cpu_to_virtio16(vdev, vq->avail_flags_shadow);
956 /* Put everything in free lists. */
958 for (i = 0; i < vring.num-1; i++)
959 vq->vring.desc[i].next = cpu_to_virtio16(vdev, i + 1);
960 memset(vq->desc_state, 0, vring.num * sizeof(struct vring_desc_state));
964 EXPORT_SYMBOL_GPL(__vring_new_virtqueue);
966 static void *vring_alloc_queue(struct virtio_device *vdev, size_t size,
967 dma_addr_t *dma_handle, gfp_t flag)
969 if (vring_use_dma_api(vdev)) {
970 return dma_alloc_coherent(vdev->dev.parent, size,
973 void *queue = alloc_pages_exact(PAGE_ALIGN(size), flag);
975 phys_addr_t phys_addr = virt_to_phys(queue);
976 *dma_handle = (dma_addr_t)phys_addr;
979 * Sanity check: make sure we dind't truncate
980 * the address. The only arches I can find that
981 * have 64-bit phys_addr_t but 32-bit dma_addr_t
982 * are certain non-highmem MIPS and x86
983 * configurations, but these configurations
984 * should never allocate physical pages above 32
985 * bits, so this is fine. Just in case, throw a
986 * warning and abort if we end up with an
987 * unrepresentable address.
989 if (WARN_ON_ONCE(*dma_handle != phys_addr)) {
990 free_pages_exact(queue, PAGE_ALIGN(size));
998 static void vring_free_queue(struct virtio_device *vdev, size_t size,
999 void *queue, dma_addr_t dma_handle)
1001 if (vring_use_dma_api(vdev)) {
1002 dma_free_coherent(vdev->dev.parent, size, queue, dma_handle);
1004 free_pages_exact(queue, PAGE_ALIGN(size));
1008 struct virtqueue *vring_create_virtqueue(
1011 unsigned int vring_align,
1012 struct virtio_device *vdev,
1014 bool may_reduce_num,
1015 bool (*notify)(struct virtqueue *),
1016 void (*callback)(struct virtqueue *),
1019 struct virtqueue *vq;
1021 dma_addr_t dma_addr;
1022 size_t queue_size_in_bytes;
1025 /* We assume num is a power of 2. */
1026 if (num & (num - 1)) {
1027 dev_warn(&vdev->dev, "Bad virtqueue length %u\n", num);
1031 /* TODO: allocate each queue chunk individually */
1032 for (; num && vring_size(num, vring_align) > PAGE_SIZE; num /= 2) {
1033 queue = vring_alloc_queue(vdev, vring_size(num, vring_align),
1035 GFP_KERNEL|__GFP_NOWARN|__GFP_ZERO);
1044 /* Try to get a single page. You are my only hope! */
1045 queue = vring_alloc_queue(vdev, vring_size(num, vring_align),
1046 &dma_addr, GFP_KERNEL|__GFP_ZERO);
1051 queue_size_in_bytes = vring_size(num, vring_align);
1052 vring_init(&vring, num, queue, vring_align);
1054 vq = __vring_new_virtqueue(index, vring, vdev, weak_barriers,
1055 notify, callback, name);
1057 vring_free_queue(vdev, queue_size_in_bytes, queue,
1062 to_vvq(vq)->queue_dma_addr = dma_addr;
1063 to_vvq(vq)->queue_size_in_bytes = queue_size_in_bytes;
1064 to_vvq(vq)->we_own_ring = true;
1068 EXPORT_SYMBOL_GPL(vring_create_virtqueue);
1070 struct virtqueue *vring_new_virtqueue(unsigned int index,
1072 unsigned int vring_align,
1073 struct virtio_device *vdev,
1076 bool (*notify)(struct virtqueue *vq),
1077 void (*callback)(struct virtqueue *vq),
1081 vring_init(&vring, num, pages, vring_align);
1082 return __vring_new_virtqueue(index, vring, vdev, weak_barriers,
1083 notify, callback, name);
1085 EXPORT_SYMBOL_GPL(vring_new_virtqueue);
1087 void vring_del_virtqueue(struct virtqueue *_vq)
1089 struct vring_virtqueue *vq = to_vvq(_vq);
1091 if (vq->we_own_ring) {
1092 vring_free_queue(vq->vq.vdev, vq->queue_size_in_bytes,
1093 vq->vring.desc, vq->queue_dma_addr);
1095 list_del(&_vq->list);
1098 EXPORT_SYMBOL_GPL(vring_del_virtqueue);
1100 /* Manipulates transport-specific feature bits. */
1101 void vring_transport_features(struct virtio_device *vdev)
1105 for (i = VIRTIO_TRANSPORT_F_START; i < VIRTIO_TRANSPORT_F_END; i++) {
1107 case VIRTIO_RING_F_INDIRECT_DESC:
1109 case VIRTIO_RING_F_EVENT_IDX:
1111 case VIRTIO_F_VERSION_1:
1113 case VIRTIO_F_IOMMU_PLATFORM:
1116 /* We don't understand this bit. */
1117 __virtio_clear_bit(vdev, i);
1121 EXPORT_SYMBOL_GPL(vring_transport_features);
1124 * virtqueue_get_vring_size - return the size of the virtqueue's vring
1125 * @vq: the struct virtqueue containing the vring of interest.
1127 * Returns the size of the vring. This is mainly used for boasting to
1128 * userspace. Unlike other operations, this need not be serialized.
1130 unsigned int virtqueue_get_vring_size(struct virtqueue *_vq)
1133 struct vring_virtqueue *vq = to_vvq(_vq);
1135 return vq->vring.num;
1137 EXPORT_SYMBOL_GPL(virtqueue_get_vring_size);
1139 bool virtqueue_is_broken(struct virtqueue *_vq)
1141 struct vring_virtqueue *vq = to_vvq(_vq);
1145 EXPORT_SYMBOL_GPL(virtqueue_is_broken);
1148 * This should prevent the device from being used, allowing drivers to
1149 * recover. You may need to grab appropriate locks to flush.
1151 void virtio_break_device(struct virtio_device *dev)
1153 struct virtqueue *_vq;
1155 list_for_each_entry(_vq, &dev->vqs, list) {
1156 struct vring_virtqueue *vq = to_vvq(_vq);
1160 EXPORT_SYMBOL_GPL(virtio_break_device);
1162 dma_addr_t virtqueue_get_desc_addr(struct virtqueue *_vq)
1164 struct vring_virtqueue *vq = to_vvq(_vq);
1166 BUG_ON(!vq->we_own_ring);
1168 return vq->queue_dma_addr;
1170 EXPORT_SYMBOL_GPL(virtqueue_get_desc_addr);
1172 dma_addr_t virtqueue_get_avail_addr(struct virtqueue *_vq)
1174 struct vring_virtqueue *vq = to_vvq(_vq);
1176 BUG_ON(!vq->we_own_ring);
1178 return vq->queue_dma_addr +
1179 ((char *)vq->vring.avail - (char *)vq->vring.desc);
1181 EXPORT_SYMBOL_GPL(virtqueue_get_avail_addr);
1183 dma_addr_t virtqueue_get_used_addr(struct virtqueue *_vq)
1185 struct vring_virtqueue *vq = to_vvq(_vq);
1187 BUG_ON(!vq->we_own_ring);
1189 return vq->queue_dma_addr +
1190 ((char *)vq->vring.used - (char *)vq->vring.desc);
1192 EXPORT_SYMBOL_GPL(virtqueue_get_used_addr);
1194 const struct vring *virtqueue_get_vring(struct virtqueue *vq)
1196 return &to_vvq(vq)->vring;
1198 EXPORT_SYMBOL_GPL(virtqueue_get_vring);
1200 MODULE_LICENSE("GPL");