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>
26
/* virtio guest is communicating with a virtual "device" that actually runs on
27
* a host processor. Memory barriers are used to control SMP effects. */
29
/* Where possible, use SMP barriers which are more lightweight than mandatory
30
* barriers, because mandatory barriers control MMIO effects on accesses
31
* through relaxed memory I/O windows (which virtio does not use). */
32
#define virtio_mb() smp_mb()
33
#define virtio_rmb() smp_rmb()
34
#define virtio_wmb() smp_wmb()
36
/* We must force memory ordering even if guest is UP since host could be
37
* running on another CPU, but SMP barriers are defined to barrier() in that
38
* configuration. So fall back to mandatory barriers instead. */
39
#define virtio_mb() mb()
40
#define virtio_rmb() rmb()
41
#define virtio_wmb() wmb()
45
/* For development, we want to crash whenever the ring is screwed. */
46
#define BAD_RING(_vq, fmt, args...) \
48
dev_err(&(_vq)->vq.vdev->dev, \
49
"%s:"fmt, (_vq)->vq.name, ##args); \
52
/* Caller is supposed to guarantee no reentry. */
53
#define START_USE(_vq) \
56
panic("%s:in_use = %i\n", \
57
(_vq)->vq.name, (_vq)->in_use); \
58
(_vq)->in_use = __LINE__; \
60
#define END_USE(_vq) \
61
do { BUG_ON(!(_vq)->in_use); (_vq)->in_use = 0; } while(0)
63
#define BAD_RING(_vq, fmt, args...) \
65
dev_err(&_vq->vq.vdev->dev, \
66
"%s:"fmt, (_vq)->vq.name, ##args); \
67
(_vq)->broken = true; \
73
struct vring_virtqueue
77
/* Actual memory layout for this queue */
80
/* Other side has made a mess, don't try any more. */
83
/* Host supports indirect buffers */
86
/* Host publishes avail event idx */
89
/* Number of free buffers */
90
unsigned int num_free;
91
/* Head of free buffer list. */
92
unsigned int free_head;
93
/* Number we've added since last sync. */
94
unsigned int num_added;
96
/* Last used index we've seen. */
99
/* How to notify other side. FIXME: commonalize hcalls! */
100
void (*notify)(struct virtqueue *vq);
103
/* They're supposed to lock for us. */
107
/* Tokens for callbacks. */
111
#define to_vvq(_vq) container_of(_vq, struct vring_virtqueue, vq)
113
/* Set up an indirect table of descriptors and add it to the queue. */
114
static int vring_add_indirect(struct vring_virtqueue *vq,
115
struct scatterlist sg[],
120
struct vring_desc *desc;
124
desc = kmalloc((out + in) * sizeof(struct vring_desc), gfp);
128
/* Transfer entries from the sg list into the indirect page */
129
for (i = 0; i < out; i++) {
130
desc[i].flags = VRING_DESC_F_NEXT;
131
desc[i].addr = sg_phys(sg);
132
desc[i].len = sg->length;
136
for (; i < (out + in); i++) {
137
desc[i].flags = VRING_DESC_F_NEXT|VRING_DESC_F_WRITE;
138
desc[i].addr = sg_phys(sg);
139
desc[i].len = sg->length;
144
/* Last one doesn't continue. */
145
desc[i-1].flags &= ~VRING_DESC_F_NEXT;
148
/* We're about to use a buffer */
151
/* Use a single buffer which doesn't continue */
152
head = vq->free_head;
153
vq->vring.desc[head].flags = VRING_DESC_F_INDIRECT;
154
vq->vring.desc[head].addr = virt_to_phys(desc);
155
vq->vring.desc[head].len = i * sizeof(struct vring_desc);
157
/* Update free pointer */
158
vq->free_head = vq->vring.desc[head].next;
163
int virtqueue_add_buf_gfp(struct virtqueue *_vq,
164
struct scatterlist sg[],
170
struct vring_virtqueue *vq = to_vvq(_vq);
171
unsigned int i, avail, uninitialized_var(prev);
176
BUG_ON(data == NULL);
178
/* If the host supports indirect descriptor tables, and we have multiple
179
* buffers, then go indirect. FIXME: tune this threshold */
180
if (vq->indirect && (out + in) > 1 && vq->num_free) {
181
head = vring_add_indirect(vq, sg, out, in, gfp);
182
if (likely(head >= 0))
186
BUG_ON(out + in > vq->vring.num);
187
BUG_ON(out + in == 0);
189
if (vq->num_free < out + in) {
190
pr_debug("Can't add buf len %i - avail = %i\n",
191
out + in, vq->num_free);
192
/* FIXME: for historical reasons, we force a notify here if
193
* there are outgoing parts to the buffer. Presumably the
194
* host should service the ring ASAP. */
201
/* We're about to use some buffers from the free list. */
202
vq->num_free -= out + in;
204
head = vq->free_head;
205
for (i = vq->free_head; out; i = vq->vring.desc[i].next, out--) {
206
vq->vring.desc[i].flags = VRING_DESC_F_NEXT;
207
vq->vring.desc[i].addr = sg_phys(sg);
208
vq->vring.desc[i].len = sg->length;
212
for (; in; i = vq->vring.desc[i].next, in--) {
213
vq->vring.desc[i].flags = VRING_DESC_F_NEXT|VRING_DESC_F_WRITE;
214
vq->vring.desc[i].addr = sg_phys(sg);
215
vq->vring.desc[i].len = sg->length;
219
/* Last one doesn't continue. */
220
vq->vring.desc[prev].flags &= ~VRING_DESC_F_NEXT;
222
/* Update free pointer */
227
vq->data[head] = data;
229
/* Put entry in available array (but don't update avail->idx until they
230
* do sync). FIXME: avoid modulus here? */
231
avail = (vq->vring.avail->idx + vq->num_added++) % vq->vring.num;
232
vq->vring.avail->ring[avail] = head;
234
pr_debug("Added buffer head %i to %p\n", head, vq);
239
EXPORT_SYMBOL_GPL(virtqueue_add_buf_gfp);
241
void virtqueue_kick(struct virtqueue *_vq)
243
struct vring_virtqueue *vq = to_vvq(_vq);
246
/* Descriptors and available array need to be set before we expose the
247
* new available array entries. */
250
old = vq->vring.avail->idx;
251
new = vq->vring.avail->idx = old + vq->num_added;
254
/* Need to update avail index before checking if we should notify */
258
vring_need_event(vring_avail_event(&vq->vring), new, old) :
259
!(vq->vring.used->flags & VRING_USED_F_NO_NOTIFY))
260
/* Prod other side to tell it about changes. */
265
EXPORT_SYMBOL_GPL(virtqueue_kick);
267
static void detach_buf(struct vring_virtqueue *vq, unsigned int head)
271
/* Clear data ptr. */
272
vq->data[head] = NULL;
274
/* Put back on free list: find end */
277
/* Free the indirect table */
278
if (vq->vring.desc[i].flags & VRING_DESC_F_INDIRECT)
279
kfree(phys_to_virt(vq->vring.desc[i].addr));
281
while (vq->vring.desc[i].flags & VRING_DESC_F_NEXT) {
282
i = vq->vring.desc[i].next;
286
vq->vring.desc[i].next = vq->free_head;
287
vq->free_head = head;
288
/* Plus final descriptor */
292
static inline bool more_used(const struct vring_virtqueue *vq)
294
return vq->last_used_idx != vq->vring.used->idx;
297
void *virtqueue_get_buf(struct virtqueue *_vq, unsigned int *len)
299
struct vring_virtqueue *vq = to_vvq(_vq);
305
if (unlikely(vq->broken)) {
310
if (!more_used(vq)) {
311
pr_debug("No more buffers in queue\n");
316
/* Only get used array entries after they have been exposed by host. */
319
i = vq->vring.used->ring[vq->last_used_idx%vq->vring.num].id;
320
*len = vq->vring.used->ring[vq->last_used_idx%vq->vring.num].len;
322
if (unlikely(i >= vq->vring.num)) {
323
BAD_RING(vq, "id %u out of range\n", i);
326
if (unlikely(!vq->data[i])) {
327
BAD_RING(vq, "id %u is not a head!\n", i);
331
/* detach_buf clears data, so grab it now. */
335
/* If we expect an interrupt for the next entry, tell host
336
* by writing event index and flush out the write before
337
* the read in the next get_buf call. */
338
if (!(vq->vring.avail->flags & VRING_AVAIL_F_NO_INTERRUPT)) {
339
vring_used_event(&vq->vring) = vq->last_used_idx;
346
EXPORT_SYMBOL_GPL(virtqueue_get_buf);
348
void virtqueue_disable_cb(struct virtqueue *_vq)
350
struct vring_virtqueue *vq = to_vvq(_vq);
352
vq->vring.avail->flags |= VRING_AVAIL_F_NO_INTERRUPT;
354
EXPORT_SYMBOL_GPL(virtqueue_disable_cb);
356
bool virtqueue_enable_cb(struct virtqueue *_vq)
358
struct vring_virtqueue *vq = to_vvq(_vq);
362
/* We optimistically turn back on interrupts, then check if there was
364
/* Depending on the VIRTIO_RING_F_EVENT_IDX feature, we need to
365
* either clear the flags bit or point the event index at the next
366
* entry. Always do both to keep code simple. */
367
vq->vring.avail->flags &= ~VRING_AVAIL_F_NO_INTERRUPT;
368
vring_used_event(&vq->vring) = vq->last_used_idx;
370
if (unlikely(more_used(vq))) {
378
EXPORT_SYMBOL_GPL(virtqueue_enable_cb);
380
bool virtqueue_enable_cb_delayed(struct virtqueue *_vq)
382
struct vring_virtqueue *vq = to_vvq(_vq);
387
/* We optimistically turn back on interrupts, then check if there was
389
/* Depending on the VIRTIO_RING_F_USED_EVENT_IDX feature, we need to
390
* either clear the flags bit or point the event index at the next
391
* entry. Always do both to keep code simple. */
392
vq->vring.avail->flags &= ~VRING_AVAIL_F_NO_INTERRUPT;
393
/* TODO: tune this threshold */
394
bufs = (u16)(vq->vring.avail->idx - vq->last_used_idx) * 3 / 4;
395
vring_used_event(&vq->vring) = vq->last_used_idx + bufs;
397
if (unlikely((u16)(vq->vring.used->idx - vq->last_used_idx) > bufs)) {
405
EXPORT_SYMBOL_GPL(virtqueue_enable_cb_delayed);
407
void *virtqueue_detach_unused_buf(struct virtqueue *_vq)
409
struct vring_virtqueue *vq = to_vvq(_vq);
415
for (i = 0; i < vq->vring.num; i++) {
418
/* detach_buf clears data, so grab it now. */
421
vq->vring.avail->idx--;
425
/* That should have freed everything. */
426
BUG_ON(vq->num_free != vq->vring.num);
431
EXPORT_SYMBOL_GPL(virtqueue_detach_unused_buf);
433
irqreturn_t vring_interrupt(int irq, void *_vq)
435
struct vring_virtqueue *vq = to_vvq(_vq);
437
if (!more_used(vq)) {
438
pr_debug("virtqueue interrupt with no work for %p\n", vq);
442
if (unlikely(vq->broken))
445
pr_debug("virtqueue callback for %p (%p)\n", vq, vq->vq.callback);
447
vq->vq.callback(&vq->vq);
451
EXPORT_SYMBOL_GPL(vring_interrupt);
453
struct virtqueue *vring_new_virtqueue(unsigned int num,
454
unsigned int vring_align,
455
struct virtio_device *vdev,
457
void (*notify)(struct virtqueue *),
458
void (*callback)(struct virtqueue *),
461
struct vring_virtqueue *vq;
464
/* We assume num is a power of 2. */
465
if (num & (num - 1)) {
466
dev_warn(&vdev->dev, "Bad virtqueue length %u\n", num);
470
vq = kmalloc(sizeof(*vq) + sizeof(void *)*num, GFP_KERNEL);
474
vring_init(&vq->vring, num, pages, vring_align);
475
vq->vq.callback = callback;
480
vq->last_used_idx = 0;
482
list_add_tail(&vq->vq.list, &vdev->vqs);
487
vq->indirect = virtio_has_feature(vdev, VIRTIO_RING_F_INDIRECT_DESC);
488
vq->event = virtio_has_feature(vdev, VIRTIO_RING_F_EVENT_IDX);
490
/* No callback? Tell other side not to bother us. */
492
vq->vring.avail->flags |= VRING_AVAIL_F_NO_INTERRUPT;
494
/* Put everything in free lists. */
497
for (i = 0; i < num-1; i++) {
498
vq->vring.desc[i].next = i+1;
505
EXPORT_SYMBOL_GPL(vring_new_virtqueue);
507
void vring_del_virtqueue(struct virtqueue *vq)
512
EXPORT_SYMBOL_GPL(vring_del_virtqueue);
514
/* Manipulates transport-specific feature bits. */
515
void vring_transport_features(struct virtio_device *vdev)
519
for (i = VIRTIO_TRANSPORT_F_START; i < VIRTIO_TRANSPORT_F_END; i++) {
521
case VIRTIO_RING_F_INDIRECT_DESC:
523
case VIRTIO_RING_F_EVENT_IDX:
526
/* We don't understand this bit. */
527
clear_bit(i, vdev->features);
531
EXPORT_SYMBOL_GPL(vring_transport_features);
533
/* return the size of the vring within the virtqueue */
534
unsigned int virtqueue_get_vring_size(struct virtqueue *_vq)
537
struct vring_virtqueue *vq = to_vvq(_vq);
539
return vq->vring.num;
541
EXPORT_SYMBOL_GPL(virtqueue_get_vring_size);
543
MODULE_LICENSE("GPL");