blob: fbd2ecde93e409ea9287d068d3f2322297c910cc [file] [log] [blame]
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);
Rusty Russell3c1b27d2009-09-23 22:26:31 -0600211
212 /* If we're indirect, we can fit many (assuming not OOM). */
213 if (vq->indirect)
214 return vq->num_free ? vq->vring.num : 0;
215 return vq->num_free;
Rusty Russell0a8a69d2007-10-22 11:03:40 +1000216}
217
218static void vring_kick(struct virtqueue *_vq)
219{
220 struct vring_virtqueue *vq = to_vvq(_vq);
221 START_USE(vq);
222 /* Descriptors and available array need to be set before we expose the
223 * new available array entries. */
224 wmb();
225
226 vq->vring.avail->idx += vq->num_added;
227 vq->num_added = 0;
228
229 /* Need to update avail index before checking if we should notify */
230 mb();
231
232 if (!(vq->vring.used->flags & VRING_USED_F_NO_NOTIFY))
233 /* Prod other side to tell it about changes. */
234 vq->notify(&vq->vq);
235
236 END_USE(vq);
237}
238
239static void detach_buf(struct vring_virtqueue *vq, unsigned int head)
240{
241 unsigned int i;
242
243 /* Clear data ptr. */
244 vq->data[head] = NULL;
245
246 /* Put back on free list: find end */
247 i = head;
Mark McLoughlin9fa29b9d2009-05-11 18:11:45 +0100248
249 /* Free the indirect table */
250 if (vq->vring.desc[i].flags & VRING_DESC_F_INDIRECT)
251 kfree(phys_to_virt(vq->vring.desc[i].addr));
252
Rusty Russell0a8a69d2007-10-22 11:03:40 +1000253 while (vq->vring.desc[i].flags & VRING_DESC_F_NEXT) {
254 i = vq->vring.desc[i].next;
255 vq->num_free++;
256 }
257
258 vq->vring.desc[i].next = vq->free_head;
259 vq->free_head = head;
260 /* Plus final descriptor */
261 vq->num_free++;
262}
263
Rusty Russell0a8a69d2007-10-22 11:03:40 +1000264static inline bool more_used(const struct vring_virtqueue *vq)
265{
266 return vq->last_used_idx != vq->vring.used->idx;
267}
268
269static void *vring_get_buf(struct virtqueue *_vq, unsigned int *len)
270{
271 struct vring_virtqueue *vq = to_vvq(_vq);
272 void *ret;
273 unsigned int i;
274
275 START_USE(vq);
276
Rusty Russell5ef82752008-05-02 21:50:43 -0500277 if (unlikely(vq->broken)) {
278 END_USE(vq);
279 return NULL;
280 }
281
Rusty Russell0a8a69d2007-10-22 11:03:40 +1000282 if (!more_used(vq)) {
283 pr_debug("No more buffers in queue\n");
284 END_USE(vq);
285 return NULL;
286 }
287
Michael S. Tsirkin2d61ba92009-10-25 15:28:53 +0200288 /* Only get used array entries after they have been exposed by host. */
289 rmb();
290
Rusty Russell0a8a69d2007-10-22 11:03:40 +1000291 i = vq->vring.used->ring[vq->last_used_idx%vq->vring.num].id;
292 *len = vq->vring.used->ring[vq->last_used_idx%vq->vring.num].len;
293
294 if (unlikely(i >= vq->vring.num)) {
295 BAD_RING(vq, "id %u out of range\n", i);
296 return NULL;
297 }
298 if (unlikely(!vq->data[i])) {
299 BAD_RING(vq, "id %u is not a head!\n", i);
300 return NULL;
301 }
302
303 /* detach_buf clears data, so grab it now. */
304 ret = vq->data[i];
305 detach_buf(vq, i);
306 vq->last_used_idx++;
307 END_USE(vq);
308 return ret;
309}
310
Rusty Russell18445c42008-02-04 23:49:57 -0500311static void vring_disable_cb(struct virtqueue *_vq)
312{
313 struct vring_virtqueue *vq = to_vvq(_vq);
314
Rusty Russell18445c42008-02-04 23:49:57 -0500315 vq->vring.avail->flags |= VRING_AVAIL_F_NO_INTERRUPT;
Rusty Russell18445c42008-02-04 23:49:57 -0500316}
317
318static bool vring_enable_cb(struct virtqueue *_vq)
Rusty Russell0a8a69d2007-10-22 11:03:40 +1000319{
320 struct vring_virtqueue *vq = to_vvq(_vq);
321
322 START_USE(vq);
Rusty Russell0a8a69d2007-10-22 11:03:40 +1000323
324 /* We optimistically turn back on interrupts, then check if there was
325 * more to do. */
326 vq->vring.avail->flags &= ~VRING_AVAIL_F_NO_INTERRUPT;
327 mb();
328 if (unlikely(more_used(vq))) {
Rusty Russell0a8a69d2007-10-22 11:03:40 +1000329 END_USE(vq);
330 return false;
331 }
332
333 END_USE(vq);
334 return true;
335}
336
337irqreturn_t vring_interrupt(int irq, void *_vq)
338{
339 struct vring_virtqueue *vq = to_vvq(_vq);
340
341 if (!more_used(vq)) {
342 pr_debug("virtqueue interrupt with no work for %p\n", vq);
343 return IRQ_NONE;
344 }
345
346 if (unlikely(vq->broken))
347 return IRQ_HANDLED;
348
349 pr_debug("virtqueue callback for %p (%p)\n", vq, vq->vq.callback);
Rusty Russell18445c42008-02-04 23:49:57 -0500350 if (vq->vq.callback)
351 vq->vq.callback(&vq->vq);
Rusty Russell0a8a69d2007-10-22 11:03:40 +1000352
353 return IRQ_HANDLED;
354}
Rusty Russellc6fd4702008-02-04 23:50:05 -0500355EXPORT_SYMBOL_GPL(vring_interrupt);
Rusty Russell0a8a69d2007-10-22 11:03:40 +1000356
357static struct virtqueue_ops vring_vq_ops = {
358 .add_buf = vring_add_buf,
359 .get_buf = vring_get_buf,
360 .kick = vring_kick,
Rusty Russell18445c42008-02-04 23:49:57 -0500361 .disable_cb = vring_disable_cb,
362 .enable_cb = vring_enable_cb,
Rusty Russell0a8a69d2007-10-22 11:03:40 +1000363};
364
365struct virtqueue *vring_new_virtqueue(unsigned int num,
Rusty Russell87c7d572008-12-30 09:26:03 -0600366 unsigned int vring_align,
Rusty Russell0a8a69d2007-10-22 11:03:40 +1000367 struct virtio_device *vdev,
368 void *pages,
369 void (*notify)(struct virtqueue *),
Rusty Russell9499f5e2009-06-12 22:16:35 -0600370 void (*callback)(struct virtqueue *),
371 const char *name)
Rusty Russell0a8a69d2007-10-22 11:03:40 +1000372{
373 struct vring_virtqueue *vq;
374 unsigned int i;
375
Rusty Russell42b36cc2007-11-12 13:39:18 +1100376 /* We assume num is a power of 2. */
377 if (num & (num - 1)) {
378 dev_warn(&vdev->dev, "Bad virtqueue length %u\n", num);
379 return NULL;
380 }
381
Rusty Russell0a8a69d2007-10-22 11:03:40 +1000382 vq = kmalloc(sizeof(*vq) + sizeof(void *)*num, GFP_KERNEL);
383 if (!vq)
384 return NULL;
385
Rusty Russell87c7d572008-12-30 09:26:03 -0600386 vring_init(&vq->vring, num, pages, vring_align);
Rusty Russell0a8a69d2007-10-22 11:03:40 +1000387 vq->vq.callback = callback;
388 vq->vq.vdev = vdev;
389 vq->vq.vq_ops = &vring_vq_ops;
Rusty Russell9499f5e2009-06-12 22:16:35 -0600390 vq->vq.name = name;
Rusty Russell0a8a69d2007-10-22 11:03:40 +1000391 vq->notify = notify;
392 vq->broken = false;
393 vq->last_used_idx = 0;
394 vq->num_added = 0;
Rusty Russell9499f5e2009-06-12 22:16:35 -0600395 list_add_tail(&vq->vq.list, &vdev->vqs);
Rusty Russell0a8a69d2007-10-22 11:03:40 +1000396#ifdef DEBUG
397 vq->in_use = false;
398#endif
399
Mark McLoughlin9fa29b9d2009-05-11 18:11:45 +0100400 vq->indirect = virtio_has_feature(vdev, VIRTIO_RING_F_INDIRECT_DESC);
401
Rusty Russell0a8a69d2007-10-22 11:03:40 +1000402 /* No callback? Tell other side not to bother us. */
403 if (!callback)
404 vq->vring.avail->flags |= VRING_AVAIL_F_NO_INTERRUPT;
405
406 /* Put everything in free lists. */
407 vq->num_free = num;
408 vq->free_head = 0;
409 for (i = 0; i < num-1; i++)
410 vq->vring.desc[i].next = i+1;
411
412 return &vq->vq;
413}
Rusty Russellc6fd4702008-02-04 23:50:05 -0500414EXPORT_SYMBOL_GPL(vring_new_virtqueue);
Rusty Russell0a8a69d2007-10-22 11:03:40 +1000415
416void vring_del_virtqueue(struct virtqueue *vq)
417{
Rusty Russell9499f5e2009-06-12 22:16:35 -0600418 list_del(&vq->list);
Rusty Russell0a8a69d2007-10-22 11:03:40 +1000419 kfree(to_vvq(vq));
420}
Rusty Russellc6fd4702008-02-04 23:50:05 -0500421EXPORT_SYMBOL_GPL(vring_del_virtqueue);
Rusty Russell0a8a69d2007-10-22 11:03:40 +1000422
Rusty Russelle34f8722008-07-25 12:06:13 -0500423/* Manipulates transport-specific feature bits. */
424void vring_transport_features(struct virtio_device *vdev)
425{
426 unsigned int i;
427
428 for (i = VIRTIO_TRANSPORT_F_START; i < VIRTIO_TRANSPORT_F_END; i++) {
429 switch (i) {
Mark McLoughlin9fa29b9d2009-05-11 18:11:45 +0100430 case VIRTIO_RING_F_INDIRECT_DESC:
431 break;
Rusty Russelle34f8722008-07-25 12:06:13 -0500432 default:
433 /* We don't understand this bit. */
434 clear_bit(i, vdev->features);
435 }
436 }
437}
438EXPORT_SYMBOL_GPL(vring_transport_features);
439
Rusty Russellc6fd4702008-02-04 23:50:05 -0500440MODULE_LICENSE("GPL");