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Rusty Russell0a8a69d2007-10-22 11:03:40 +10001/* Virtio ring implementation.
2 *
3 * Copyright 2007 Rusty Russell IBM Corporation
4 *
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.
9 *
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.
14 *
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
18 */
19#include <linux/virtio.h>
20#include <linux/virtio_ring.h>
Rusty Russelle34f8722008-07-25 12:06:13 -050021#include <linux/virtio_config.h>
Rusty Russell0a8a69d2007-10-22 11:03:40 +100022#include <linux/device.h>
23
24#ifdef DEBUG
25/* For development, we want to crash whenever the ring is screwed. */
Rusty Russell9499f5e2009-06-12 22:16:35 -060026#define BAD_RING(_vq, fmt, args...) \
27 do { \
28 dev_err(&(_vq)->vq.vdev->dev, \
29 "%s:"fmt, (_vq)->vq.name, ##args); \
30 BUG(); \
31 } while (0)
Rusty Russellc5f841f2009-03-30 21:55:22 -060032/* Caller is supposed to guarantee no reentry. */
33#define START_USE(_vq) \
34 do { \
35 if ((_vq)->in_use) \
Rusty Russell9499f5e2009-06-12 22:16:35 -060036 panic("%s:in_use = %i\n", \
37 (_vq)->vq.name, (_vq)->in_use); \
Rusty Russellc5f841f2009-03-30 21:55:22 -060038 (_vq)->in_use = __LINE__; \
39 mb(); \
Rusty Russell9499f5e2009-06-12 22:16:35 -060040 } while (0)
Roel Kluin3a35ce72009-01-22 16:42:57 +010041#define END_USE(_vq) \
42 do { BUG_ON(!(_vq)->in_use); (_vq)->in_use = 0; mb(); } while(0)
Rusty Russell0a8a69d2007-10-22 11:03:40 +100043#else
Rusty Russell9499f5e2009-06-12 22:16:35 -060044#define BAD_RING(_vq, fmt, args...) \
45 do { \
46 dev_err(&_vq->vq.vdev->dev, \
47 "%s:"fmt, (_vq)->vq.name, ##args); \
48 (_vq)->broken = true; \
49 } while (0)
Rusty Russell0a8a69d2007-10-22 11:03:40 +100050#define START_USE(vq)
51#define END_USE(vq)
52#endif
53
54struct vring_virtqueue
55{
56 struct virtqueue vq;
57
58 /* Actual memory layout for this queue */
59 struct vring vring;
60
61 /* Other side has made a mess, don't try any more. */
62 bool broken;
63
Mark McLoughlin9fa29b9d2009-05-11 18:11:45 +010064 /* Host supports indirect buffers */
65 bool indirect;
66
Rusty Russell0a8a69d2007-10-22 11:03:40 +100067 /* Number of free buffers */
68 unsigned int num_free;
69 /* Head of free buffer list. */
70 unsigned int free_head;
71 /* Number we've added since last sync. */
72 unsigned int num_added;
73
74 /* Last used index we've seen. */
Anthony Liguori1bc49532007-11-07 15:49:24 -060075 u16 last_used_idx;
Rusty Russell0a8a69d2007-10-22 11:03:40 +100076
77 /* How to notify other side. FIXME: commonalize hcalls! */
78 void (*notify)(struct virtqueue *vq);
79
80#ifdef DEBUG
81 /* They're supposed to lock for us. */
82 unsigned int in_use;
83#endif
84
85 /* Tokens for callbacks. */
86 void *data[];
87};
88
89#define to_vvq(_vq) container_of(_vq, struct vring_virtqueue, vq)
90
Mark McLoughlin9fa29b9d2009-05-11 18:11:45 +010091/* Set up an indirect table of descriptors and add it to the queue. */
92static int vring_add_indirect(struct vring_virtqueue *vq,
93 struct scatterlist sg[],
94 unsigned int out,
95 unsigned int in)
96{
97 struct vring_desc *desc;
98 unsigned head;
99 int i;
100
101 desc = kmalloc((out + in) * sizeof(struct vring_desc), GFP_ATOMIC);
102 if (!desc)
103 return vq->vring.num;
104
105 /* Transfer entries from the sg list into the indirect page */
106 for (i = 0; i < out; i++) {
107 desc[i].flags = VRING_DESC_F_NEXT;
108 desc[i].addr = sg_phys(sg);
109 desc[i].len = sg->length;
110 desc[i].next = i+1;
111 sg++;
112 }
113 for (; i < (out + in); i++) {
114 desc[i].flags = VRING_DESC_F_NEXT|VRING_DESC_F_WRITE;
115 desc[i].addr = sg_phys(sg);
116 desc[i].len = sg->length;
117 desc[i].next = i+1;
118 sg++;
119 }
120
121 /* Last one doesn't continue. */
122 desc[i-1].flags &= ~VRING_DESC_F_NEXT;
123 desc[i-1].next = 0;
124
125 /* We're about to use a buffer */
126 vq->num_free--;
127
128 /* Use a single buffer which doesn't continue */
129 head = vq->free_head;
130 vq->vring.desc[head].flags = VRING_DESC_F_INDIRECT;
131 vq->vring.desc[head].addr = virt_to_phys(desc);
132 vq->vring.desc[head].len = i * sizeof(struct vring_desc);
133
134 /* Update free pointer */
135 vq->free_head = vq->vring.desc[head].next;
136
137 return head;
138}
139
Rusty Russell0a8a69d2007-10-22 11:03:40 +1000140static int vring_add_buf(struct virtqueue *_vq,
141 struct scatterlist sg[],
142 unsigned int out,
143 unsigned int in,
144 void *data)
145{
146 struct vring_virtqueue *vq = to_vvq(_vq);
147 unsigned int i, avail, head, uninitialized_var(prev);
148
Mark McLoughlin9fa29b9d2009-05-11 18:11:45 +0100149 START_USE(vq);
150
Rusty Russell0a8a69d2007-10-22 11:03:40 +1000151 BUG_ON(data == NULL);
Mark McLoughlin9fa29b9d2009-05-11 18:11:45 +0100152
153 /* If the host supports indirect descriptor tables, and we have multiple
154 * buffers, then go indirect. FIXME: tune this threshold */
155 if (vq->indirect && (out + in) > 1 && vq->num_free) {
156 head = vring_add_indirect(vq, sg, out, in);
157 if (head != vq->vring.num)
158 goto add_head;
159 }
160
Rusty Russell0a8a69d2007-10-22 11:03:40 +1000161 BUG_ON(out + in > vq->vring.num);
162 BUG_ON(out + in == 0);
163
Rusty Russell0a8a69d2007-10-22 11:03:40 +1000164 if (vq->num_free < out + in) {
165 pr_debug("Can't add buf len %i - avail = %i\n",
166 out + in, vq->num_free);
Rusty Russell44653ea2008-07-25 12:06:04 -0500167 /* FIXME: for historical reasons, we force a notify here if
168 * there are outgoing parts to the buffer. Presumably the
169 * host should service the ring ASAP. */
170 if (out)
171 vq->notify(&vq->vq);
Rusty Russell0a8a69d2007-10-22 11:03:40 +1000172 END_USE(vq);
173 return -ENOSPC;
174 }
175
176 /* We're about to use some buffers from the free list. */
177 vq->num_free -= out + in;
178
179 head = vq->free_head;
180 for (i = vq->free_head; out; i = vq->vring.desc[i].next, out--) {
181 vq->vring.desc[i].flags = VRING_DESC_F_NEXT;
Rusty Russell15f9c892008-02-04 23:50:05 -0500182 vq->vring.desc[i].addr = sg_phys(sg);
Rusty Russell0a8a69d2007-10-22 11:03:40 +1000183 vq->vring.desc[i].len = sg->length;
184 prev = i;
185 sg++;
186 }
187 for (; in; i = vq->vring.desc[i].next, in--) {
188 vq->vring.desc[i].flags = VRING_DESC_F_NEXT|VRING_DESC_F_WRITE;
Rusty Russell15f9c892008-02-04 23:50:05 -0500189 vq->vring.desc[i].addr = sg_phys(sg);
Rusty Russell0a8a69d2007-10-22 11:03:40 +1000190 vq->vring.desc[i].len = sg->length;
191 prev = i;
192 sg++;
193 }
194 /* Last one doesn't continue. */
195 vq->vring.desc[prev].flags &= ~VRING_DESC_F_NEXT;
196
197 /* Update free pointer */
198 vq->free_head = i;
199
Mark McLoughlin9fa29b9d2009-05-11 18:11:45 +0100200add_head:
Rusty Russell0a8a69d2007-10-22 11:03:40 +1000201 /* Set token. */
202 vq->data[head] = data;
203
204 /* Put entry in available array (but don't update avail->idx until they
205 * do sync). FIXME: avoid modulus here? */
206 avail = (vq->vring.avail->idx + vq->num_added++) % vq->vring.num;
207 vq->vring.avail->ring[avail] = head;
208
209 pr_debug("Added buffer head %i to %p\n", head, vq);
210 END_USE(vq);
211 return 0;
212}
213
214static void vring_kick(struct virtqueue *_vq)
215{
216 struct vring_virtqueue *vq = to_vvq(_vq);
217 START_USE(vq);
218 /* Descriptors and available array need to be set before we expose the
219 * new available array entries. */
220 wmb();
221
222 vq->vring.avail->idx += vq->num_added;
223 vq->num_added = 0;
224
225 /* Need to update avail index before checking if we should notify */
226 mb();
227
228 if (!(vq->vring.used->flags & VRING_USED_F_NO_NOTIFY))
229 /* Prod other side to tell it about changes. */
230 vq->notify(&vq->vq);
231
232 END_USE(vq);
233}
234
235static void detach_buf(struct vring_virtqueue *vq, unsigned int head)
236{
237 unsigned int i;
238
239 /* Clear data ptr. */
240 vq->data[head] = NULL;
241
242 /* Put back on free list: find end */
243 i = head;
Mark McLoughlin9fa29b9d2009-05-11 18:11:45 +0100244
245 /* Free the indirect table */
246 if (vq->vring.desc[i].flags & VRING_DESC_F_INDIRECT)
247 kfree(phys_to_virt(vq->vring.desc[i].addr));
248
Rusty Russell0a8a69d2007-10-22 11:03:40 +1000249 while (vq->vring.desc[i].flags & VRING_DESC_F_NEXT) {
250 i = vq->vring.desc[i].next;
251 vq->num_free++;
252 }
253
254 vq->vring.desc[i].next = vq->free_head;
255 vq->free_head = head;
256 /* Plus final descriptor */
257 vq->num_free++;
258}
259
Rusty Russell0a8a69d2007-10-22 11:03:40 +1000260static inline bool more_used(const struct vring_virtqueue *vq)
261{
262 return vq->last_used_idx != vq->vring.used->idx;
263}
264
265static void *vring_get_buf(struct virtqueue *_vq, unsigned int *len)
266{
267 struct vring_virtqueue *vq = to_vvq(_vq);
268 void *ret;
269 unsigned int i;
270
271 START_USE(vq);
272
Rusty Russell5ef82752008-05-02 21:50:43 -0500273 if (unlikely(vq->broken)) {
274 END_USE(vq);
275 return NULL;
276 }
277
Rusty Russell0a8a69d2007-10-22 11:03:40 +1000278 if (!more_used(vq)) {
279 pr_debug("No more buffers in queue\n");
280 END_USE(vq);
281 return NULL;
282 }
283
284 i = vq->vring.used->ring[vq->last_used_idx%vq->vring.num].id;
285 *len = vq->vring.used->ring[vq->last_used_idx%vq->vring.num].len;
286
287 if (unlikely(i >= vq->vring.num)) {
288 BAD_RING(vq, "id %u out of range\n", i);
289 return NULL;
290 }
291 if (unlikely(!vq->data[i])) {
292 BAD_RING(vq, "id %u is not a head!\n", i);
293 return NULL;
294 }
295
296 /* detach_buf clears data, so grab it now. */
297 ret = vq->data[i];
298 detach_buf(vq, i);
299 vq->last_used_idx++;
300 END_USE(vq);
301 return ret;
302}
303
Rusty Russell18445c42008-02-04 23:49:57 -0500304static void vring_disable_cb(struct virtqueue *_vq)
305{
306 struct vring_virtqueue *vq = to_vvq(_vq);
307
Rusty Russell18445c42008-02-04 23:49:57 -0500308 vq->vring.avail->flags |= VRING_AVAIL_F_NO_INTERRUPT;
Rusty Russell18445c42008-02-04 23:49:57 -0500309}
310
311static bool vring_enable_cb(struct virtqueue *_vq)
Rusty Russell0a8a69d2007-10-22 11:03:40 +1000312{
313 struct vring_virtqueue *vq = to_vvq(_vq);
314
315 START_USE(vq);
Rusty Russell0a8a69d2007-10-22 11:03:40 +1000316
317 /* We optimistically turn back on interrupts, then check if there was
318 * more to do. */
319 vq->vring.avail->flags &= ~VRING_AVAIL_F_NO_INTERRUPT;
320 mb();
321 if (unlikely(more_used(vq))) {
Rusty Russell0a8a69d2007-10-22 11:03:40 +1000322 END_USE(vq);
323 return false;
324 }
325
326 END_USE(vq);
327 return true;
328}
329
330irqreturn_t vring_interrupt(int irq, void *_vq)
331{
332 struct vring_virtqueue *vq = to_vvq(_vq);
333
334 if (!more_used(vq)) {
335 pr_debug("virtqueue interrupt with no work for %p\n", vq);
336 return IRQ_NONE;
337 }
338
339 if (unlikely(vq->broken))
340 return IRQ_HANDLED;
341
342 pr_debug("virtqueue callback for %p (%p)\n", vq, vq->vq.callback);
Rusty Russell18445c42008-02-04 23:49:57 -0500343 if (vq->vq.callback)
344 vq->vq.callback(&vq->vq);
Rusty Russell0a8a69d2007-10-22 11:03:40 +1000345
346 return IRQ_HANDLED;
347}
Rusty Russellc6fd4702008-02-04 23:50:05 -0500348EXPORT_SYMBOL_GPL(vring_interrupt);
Rusty Russell0a8a69d2007-10-22 11:03:40 +1000349
350static struct virtqueue_ops vring_vq_ops = {
351 .add_buf = vring_add_buf,
352 .get_buf = vring_get_buf,
353 .kick = vring_kick,
Rusty Russell18445c42008-02-04 23:49:57 -0500354 .disable_cb = vring_disable_cb,
355 .enable_cb = vring_enable_cb,
Rusty Russell0a8a69d2007-10-22 11:03:40 +1000356};
357
358struct virtqueue *vring_new_virtqueue(unsigned int num,
Rusty Russell87c7d572008-12-30 09:26:03 -0600359 unsigned int vring_align,
Rusty Russell0a8a69d2007-10-22 11:03:40 +1000360 struct virtio_device *vdev,
361 void *pages,
362 void (*notify)(struct virtqueue *),
Rusty Russell9499f5e2009-06-12 22:16:35 -0600363 void (*callback)(struct virtqueue *),
364 const char *name)
Rusty Russell0a8a69d2007-10-22 11:03:40 +1000365{
366 struct vring_virtqueue *vq;
367 unsigned int i;
368
Rusty Russell42b36cc2007-11-12 13:39:18 +1100369 /* We assume num is a power of 2. */
370 if (num & (num - 1)) {
371 dev_warn(&vdev->dev, "Bad virtqueue length %u\n", num);
372 return NULL;
373 }
374
Rusty Russell0a8a69d2007-10-22 11:03:40 +1000375 vq = kmalloc(sizeof(*vq) + sizeof(void *)*num, GFP_KERNEL);
376 if (!vq)
377 return NULL;
378
Rusty Russell87c7d572008-12-30 09:26:03 -0600379 vring_init(&vq->vring, num, pages, vring_align);
Rusty Russell0a8a69d2007-10-22 11:03:40 +1000380 vq->vq.callback = callback;
381 vq->vq.vdev = vdev;
382 vq->vq.vq_ops = &vring_vq_ops;
Rusty Russell9499f5e2009-06-12 22:16:35 -0600383 vq->vq.name = name;
Rusty Russell0a8a69d2007-10-22 11:03:40 +1000384 vq->notify = notify;
385 vq->broken = false;
386 vq->last_used_idx = 0;
387 vq->num_added = 0;
Rusty Russell9499f5e2009-06-12 22:16:35 -0600388 list_add_tail(&vq->vq.list, &vdev->vqs);
Rusty Russell0a8a69d2007-10-22 11:03:40 +1000389#ifdef DEBUG
390 vq->in_use = false;
391#endif
392
Mark McLoughlin9fa29b9d2009-05-11 18:11:45 +0100393 vq->indirect = virtio_has_feature(vdev, VIRTIO_RING_F_INDIRECT_DESC);
394
Rusty Russell0a8a69d2007-10-22 11:03:40 +1000395 /* No callback? Tell other side not to bother us. */
396 if (!callback)
397 vq->vring.avail->flags |= VRING_AVAIL_F_NO_INTERRUPT;
398
399 /* Put everything in free lists. */
400 vq->num_free = num;
401 vq->free_head = 0;
402 for (i = 0; i < num-1; i++)
403 vq->vring.desc[i].next = i+1;
404
405 return &vq->vq;
406}
Rusty Russellc6fd4702008-02-04 23:50:05 -0500407EXPORT_SYMBOL_GPL(vring_new_virtqueue);
Rusty Russell0a8a69d2007-10-22 11:03:40 +1000408
409void vring_del_virtqueue(struct virtqueue *vq)
410{
Rusty Russell9499f5e2009-06-12 22:16:35 -0600411 list_del(&vq->list);
Rusty Russell0a8a69d2007-10-22 11:03:40 +1000412 kfree(to_vvq(vq));
413}
Rusty Russellc6fd4702008-02-04 23:50:05 -0500414EXPORT_SYMBOL_GPL(vring_del_virtqueue);
Rusty Russell0a8a69d2007-10-22 11:03:40 +1000415
Rusty Russelle34f8722008-07-25 12:06:13 -0500416/* Manipulates transport-specific feature bits. */
417void vring_transport_features(struct virtio_device *vdev)
418{
419 unsigned int i;
420
421 for (i = VIRTIO_TRANSPORT_F_START; i < VIRTIO_TRANSPORT_F_END; i++) {
422 switch (i) {
Mark McLoughlin9fa29b9d2009-05-11 18:11:45 +0100423 case VIRTIO_RING_F_INDIRECT_DESC:
424 break;
Rusty Russelle34f8722008-07-25 12:06:13 -0500425 default:
426 /* We don't understand this bit. */
427 clear_bit(i, vdev->features);
428 }
429 }
430}
431EXPORT_SYMBOL_GPL(vring_transport_features);
432
Rusty Russellc6fd4702008-02-04 23:50:05 -0500433MODULE_LICENSE("GPL");