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0a8a69dd RR |
1 | /* 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> | |
e34f8725 | 21 | #include <linux/virtio_config.h> |
0a8a69dd | 22 | #include <linux/device.h> |
5a0e3ad6 | 23 | #include <linux/slab.h> |
0a8a69dd | 24 | |
d57ed95d MT |
25 | /* virtio guest is communicating with a virtual "device" that actually runs on |
26 | * a host processor. Memory barriers are used to control SMP effects. */ | |
27 | #ifdef CONFIG_SMP | |
28 | /* Where possible, use SMP barriers which are more lightweight than mandatory | |
29 | * barriers, because mandatory barriers control MMIO effects on accesses | |
30 | * through relaxed memory I/O windows (which virtio does not use). */ | |
31 | #define virtio_mb() smp_mb() | |
32 | #define virtio_rmb() smp_rmb() | |
33 | #define virtio_wmb() smp_wmb() | |
34 | #else | |
35 | /* We must force memory ordering even if guest is UP since host could be | |
36 | * running on another CPU, but SMP barriers are defined to barrier() in that | |
37 | * configuration. So fall back to mandatory barriers instead. */ | |
38 | #define virtio_mb() mb() | |
39 | #define virtio_rmb() rmb() | |
40 | #define virtio_wmb() wmb() | |
41 | #endif | |
42 | ||
0a8a69dd RR |
43 | #ifdef DEBUG |
44 | /* For development, we want to crash whenever the ring is screwed. */ | |
9499f5e7 RR |
45 | #define BAD_RING(_vq, fmt, args...) \ |
46 | do { \ | |
47 | dev_err(&(_vq)->vq.vdev->dev, \ | |
48 | "%s:"fmt, (_vq)->vq.name, ##args); \ | |
49 | BUG(); \ | |
50 | } while (0) | |
c5f841f1 RR |
51 | /* Caller is supposed to guarantee no reentry. */ |
52 | #define START_USE(_vq) \ | |
53 | do { \ | |
54 | if ((_vq)->in_use) \ | |
9499f5e7 RR |
55 | panic("%s:in_use = %i\n", \ |
56 | (_vq)->vq.name, (_vq)->in_use); \ | |
c5f841f1 | 57 | (_vq)->in_use = __LINE__; \ |
9499f5e7 | 58 | } while (0) |
3a35ce7d | 59 | #define END_USE(_vq) \ |
97a545ab | 60 | do { BUG_ON(!(_vq)->in_use); (_vq)->in_use = 0; } while(0) |
0a8a69dd | 61 | #else |
9499f5e7 RR |
62 | #define BAD_RING(_vq, fmt, args...) \ |
63 | do { \ | |
64 | dev_err(&_vq->vq.vdev->dev, \ | |
65 | "%s:"fmt, (_vq)->vq.name, ##args); \ | |
66 | (_vq)->broken = true; \ | |
67 | } while (0) | |
0a8a69dd RR |
68 | #define START_USE(vq) |
69 | #define END_USE(vq) | |
70 | #endif | |
71 | ||
72 | struct vring_virtqueue | |
73 | { | |
74 | struct virtqueue vq; | |
75 | ||
76 | /* Actual memory layout for this queue */ | |
77 | struct vring vring; | |
78 | ||
79 | /* Other side has made a mess, don't try any more. */ | |
80 | bool broken; | |
81 | ||
9fa29b9d MM |
82 | /* Host supports indirect buffers */ |
83 | bool indirect; | |
84 | ||
0a8a69dd RR |
85 | /* Number of free buffers */ |
86 | unsigned int num_free; | |
87 | /* Head of free buffer list. */ | |
88 | unsigned int free_head; | |
89 | /* Number we've added since last sync. */ | |
90 | unsigned int num_added; | |
91 | ||
92 | /* Last used index we've seen. */ | |
1bc4953e | 93 | u16 last_used_idx; |
0a8a69dd RR |
94 | |
95 | /* How to notify other side. FIXME: commonalize hcalls! */ | |
96 | void (*notify)(struct virtqueue *vq); | |
97 | ||
98 | #ifdef DEBUG | |
99 | /* They're supposed to lock for us. */ | |
100 | unsigned int in_use; | |
101 | #endif | |
102 | ||
103 | /* Tokens for callbacks. */ | |
104 | void *data[]; | |
105 | }; | |
106 | ||
107 | #define to_vvq(_vq) container_of(_vq, struct vring_virtqueue, vq) | |
108 | ||
9fa29b9d MM |
109 | /* Set up an indirect table of descriptors and add it to the queue. */ |
110 | static int vring_add_indirect(struct vring_virtqueue *vq, | |
111 | struct scatterlist sg[], | |
112 | unsigned int out, | |
113 | unsigned int in) | |
114 | { | |
115 | struct vring_desc *desc; | |
116 | unsigned head; | |
117 | int i; | |
118 | ||
119 | desc = kmalloc((out + in) * sizeof(struct vring_desc), GFP_ATOMIC); | |
120 | if (!desc) | |
121 | return vq->vring.num; | |
122 | ||
123 | /* Transfer entries from the sg list into the indirect page */ | |
124 | for (i = 0; i < out; i++) { | |
125 | desc[i].flags = VRING_DESC_F_NEXT; | |
126 | desc[i].addr = sg_phys(sg); | |
127 | desc[i].len = sg->length; | |
128 | desc[i].next = i+1; | |
129 | sg++; | |
130 | } | |
131 | for (; i < (out + in); i++) { | |
132 | desc[i].flags = VRING_DESC_F_NEXT|VRING_DESC_F_WRITE; | |
133 | desc[i].addr = sg_phys(sg); | |
134 | desc[i].len = sg->length; | |
135 | desc[i].next = i+1; | |
136 | sg++; | |
137 | } | |
138 | ||
139 | /* Last one doesn't continue. */ | |
140 | desc[i-1].flags &= ~VRING_DESC_F_NEXT; | |
141 | desc[i-1].next = 0; | |
142 | ||
143 | /* We're about to use a buffer */ | |
144 | vq->num_free--; | |
145 | ||
146 | /* Use a single buffer which doesn't continue */ | |
147 | head = vq->free_head; | |
148 | vq->vring.desc[head].flags = VRING_DESC_F_INDIRECT; | |
149 | vq->vring.desc[head].addr = virt_to_phys(desc); | |
150 | vq->vring.desc[head].len = i * sizeof(struct vring_desc); | |
151 | ||
152 | /* Update free pointer */ | |
153 | vq->free_head = vq->vring.desc[head].next; | |
154 | ||
155 | return head; | |
156 | } | |
157 | ||
0a8a69dd RR |
158 | static int vring_add_buf(struct virtqueue *_vq, |
159 | struct scatterlist sg[], | |
160 | unsigned int out, | |
161 | unsigned int in, | |
162 | void *data) | |
163 | { | |
164 | struct vring_virtqueue *vq = to_vvq(_vq); | |
165 | unsigned int i, avail, head, uninitialized_var(prev); | |
166 | ||
9fa29b9d MM |
167 | START_USE(vq); |
168 | ||
0a8a69dd | 169 | BUG_ON(data == NULL); |
9fa29b9d MM |
170 | |
171 | /* If the host supports indirect descriptor tables, and we have multiple | |
172 | * buffers, then go indirect. FIXME: tune this threshold */ | |
173 | if (vq->indirect && (out + in) > 1 && vq->num_free) { | |
174 | head = vring_add_indirect(vq, sg, out, in); | |
175 | if (head != vq->vring.num) | |
176 | goto add_head; | |
177 | } | |
178 | ||
0a8a69dd RR |
179 | BUG_ON(out + in > vq->vring.num); |
180 | BUG_ON(out + in == 0); | |
181 | ||
0a8a69dd RR |
182 | if (vq->num_free < out + in) { |
183 | pr_debug("Can't add buf len %i - avail = %i\n", | |
184 | out + in, vq->num_free); | |
44653eae RR |
185 | /* FIXME: for historical reasons, we force a notify here if |
186 | * there are outgoing parts to the buffer. Presumably the | |
187 | * host should service the ring ASAP. */ | |
188 | if (out) | |
189 | vq->notify(&vq->vq); | |
0a8a69dd RR |
190 | END_USE(vq); |
191 | return -ENOSPC; | |
192 | } | |
193 | ||
194 | /* We're about to use some buffers from the free list. */ | |
195 | vq->num_free -= out + in; | |
196 | ||
197 | head = vq->free_head; | |
198 | for (i = vq->free_head; out; i = vq->vring.desc[i].next, out--) { | |
199 | vq->vring.desc[i].flags = VRING_DESC_F_NEXT; | |
15f9c890 | 200 | vq->vring.desc[i].addr = sg_phys(sg); |
0a8a69dd RR |
201 | vq->vring.desc[i].len = sg->length; |
202 | prev = i; | |
203 | sg++; | |
204 | } | |
205 | for (; in; i = vq->vring.desc[i].next, in--) { | |
206 | vq->vring.desc[i].flags = VRING_DESC_F_NEXT|VRING_DESC_F_WRITE; | |
15f9c890 | 207 | vq->vring.desc[i].addr = sg_phys(sg); |
0a8a69dd RR |
208 | vq->vring.desc[i].len = sg->length; |
209 | prev = i; | |
210 | sg++; | |
211 | } | |
212 | /* Last one doesn't continue. */ | |
213 | vq->vring.desc[prev].flags &= ~VRING_DESC_F_NEXT; | |
214 | ||
215 | /* Update free pointer */ | |
216 | vq->free_head = i; | |
217 | ||
9fa29b9d | 218 | add_head: |
0a8a69dd RR |
219 | /* Set token. */ |
220 | vq->data[head] = data; | |
221 | ||
222 | /* Put entry in available array (but don't update avail->idx until they | |
223 | * do sync). FIXME: avoid modulus here? */ | |
224 | avail = (vq->vring.avail->idx + vq->num_added++) % vq->vring.num; | |
225 | vq->vring.avail->ring[avail] = head; | |
226 | ||
227 | pr_debug("Added buffer head %i to %p\n", head, vq); | |
228 | END_USE(vq); | |
3c1b27d5 RR |
229 | |
230 | /* If we're indirect, we can fit many (assuming not OOM). */ | |
231 | if (vq->indirect) | |
232 | return vq->num_free ? vq->vring.num : 0; | |
233 | return vq->num_free; | |
0a8a69dd RR |
234 | } |
235 | ||
236 | static void vring_kick(struct virtqueue *_vq) | |
237 | { | |
238 | struct vring_virtqueue *vq = to_vvq(_vq); | |
239 | START_USE(vq); | |
240 | /* Descriptors and available array need to be set before we expose the | |
241 | * new available array entries. */ | |
d57ed95d | 242 | virtio_wmb(); |
0a8a69dd RR |
243 | |
244 | vq->vring.avail->idx += vq->num_added; | |
245 | vq->num_added = 0; | |
246 | ||
247 | /* Need to update avail index before checking if we should notify */ | |
d57ed95d | 248 | virtio_mb(); |
0a8a69dd RR |
249 | |
250 | if (!(vq->vring.used->flags & VRING_USED_F_NO_NOTIFY)) | |
251 | /* Prod other side to tell it about changes. */ | |
252 | vq->notify(&vq->vq); | |
253 | ||
254 | END_USE(vq); | |
255 | } | |
256 | ||
257 | static void detach_buf(struct vring_virtqueue *vq, unsigned int head) | |
258 | { | |
259 | unsigned int i; | |
260 | ||
261 | /* Clear data ptr. */ | |
262 | vq->data[head] = NULL; | |
263 | ||
264 | /* Put back on free list: find end */ | |
265 | i = head; | |
9fa29b9d MM |
266 | |
267 | /* Free the indirect table */ | |
268 | if (vq->vring.desc[i].flags & VRING_DESC_F_INDIRECT) | |
269 | kfree(phys_to_virt(vq->vring.desc[i].addr)); | |
270 | ||
0a8a69dd RR |
271 | while (vq->vring.desc[i].flags & VRING_DESC_F_NEXT) { |
272 | i = vq->vring.desc[i].next; | |
273 | vq->num_free++; | |
274 | } | |
275 | ||
276 | vq->vring.desc[i].next = vq->free_head; | |
277 | vq->free_head = head; | |
278 | /* Plus final descriptor */ | |
279 | vq->num_free++; | |
280 | } | |
281 | ||
0a8a69dd RR |
282 | static inline bool more_used(const struct vring_virtqueue *vq) |
283 | { | |
284 | return vq->last_used_idx != vq->vring.used->idx; | |
285 | } | |
286 | ||
287 | static void *vring_get_buf(struct virtqueue *_vq, unsigned int *len) | |
288 | { | |
289 | struct vring_virtqueue *vq = to_vvq(_vq); | |
290 | void *ret; | |
291 | unsigned int i; | |
292 | ||
293 | START_USE(vq); | |
294 | ||
5ef82752 RR |
295 | if (unlikely(vq->broken)) { |
296 | END_USE(vq); | |
297 | return NULL; | |
298 | } | |
299 | ||
0a8a69dd RR |
300 | if (!more_used(vq)) { |
301 | pr_debug("No more buffers in queue\n"); | |
302 | END_USE(vq); | |
303 | return NULL; | |
304 | } | |
305 | ||
2d61ba95 | 306 | /* Only get used array entries after they have been exposed by host. */ |
d57ed95d | 307 | virtio_rmb(); |
2d61ba95 | 308 | |
0a8a69dd RR |
309 | i = vq->vring.used->ring[vq->last_used_idx%vq->vring.num].id; |
310 | *len = vq->vring.used->ring[vq->last_used_idx%vq->vring.num].len; | |
311 | ||
312 | if (unlikely(i >= vq->vring.num)) { | |
313 | BAD_RING(vq, "id %u out of range\n", i); | |
314 | return NULL; | |
315 | } | |
316 | if (unlikely(!vq->data[i])) { | |
317 | BAD_RING(vq, "id %u is not a head!\n", i); | |
318 | return NULL; | |
319 | } | |
320 | ||
321 | /* detach_buf clears data, so grab it now. */ | |
322 | ret = vq->data[i]; | |
323 | detach_buf(vq, i); | |
324 | vq->last_used_idx++; | |
325 | END_USE(vq); | |
326 | return ret; | |
327 | } | |
328 | ||
18445c4d RR |
329 | static void vring_disable_cb(struct virtqueue *_vq) |
330 | { | |
331 | struct vring_virtqueue *vq = to_vvq(_vq); | |
332 | ||
18445c4d | 333 | vq->vring.avail->flags |= VRING_AVAIL_F_NO_INTERRUPT; |
18445c4d RR |
334 | } |
335 | ||
336 | static bool vring_enable_cb(struct virtqueue *_vq) | |
0a8a69dd RR |
337 | { |
338 | struct vring_virtqueue *vq = to_vvq(_vq); | |
339 | ||
340 | START_USE(vq); | |
0a8a69dd RR |
341 | |
342 | /* We optimistically turn back on interrupts, then check if there was | |
343 | * more to do. */ | |
344 | vq->vring.avail->flags &= ~VRING_AVAIL_F_NO_INTERRUPT; | |
d57ed95d | 345 | virtio_mb(); |
0a8a69dd | 346 | if (unlikely(more_used(vq))) { |
0a8a69dd RR |
347 | END_USE(vq); |
348 | return false; | |
349 | } | |
350 | ||
351 | END_USE(vq); | |
352 | return true; | |
353 | } | |
354 | ||
c021eac4 SM |
355 | static void *vring_detach_unused_buf(struct virtqueue *_vq) |
356 | { | |
357 | struct vring_virtqueue *vq = to_vvq(_vq); | |
358 | unsigned int i; | |
359 | void *buf; | |
360 | ||
361 | START_USE(vq); | |
362 | ||
363 | for (i = 0; i < vq->vring.num; i++) { | |
364 | if (!vq->data[i]) | |
365 | continue; | |
366 | /* detach_buf clears data, so grab it now. */ | |
367 | buf = vq->data[i]; | |
368 | detach_buf(vq, i); | |
369 | END_USE(vq); | |
370 | return buf; | |
371 | } | |
372 | /* That should have freed everything. */ | |
373 | BUG_ON(vq->num_free != vq->vring.num); | |
374 | ||
375 | END_USE(vq); | |
376 | return NULL; | |
377 | } | |
378 | ||
0a8a69dd RR |
379 | irqreturn_t vring_interrupt(int irq, void *_vq) |
380 | { | |
381 | struct vring_virtqueue *vq = to_vvq(_vq); | |
382 | ||
383 | if (!more_used(vq)) { | |
384 | pr_debug("virtqueue interrupt with no work for %p\n", vq); | |
385 | return IRQ_NONE; | |
386 | } | |
387 | ||
388 | if (unlikely(vq->broken)) | |
389 | return IRQ_HANDLED; | |
390 | ||
391 | pr_debug("virtqueue callback for %p (%p)\n", vq, vq->vq.callback); | |
18445c4d RR |
392 | if (vq->vq.callback) |
393 | vq->vq.callback(&vq->vq); | |
0a8a69dd RR |
394 | |
395 | return IRQ_HANDLED; | |
396 | } | |
c6fd4701 | 397 | EXPORT_SYMBOL_GPL(vring_interrupt); |
0a8a69dd RR |
398 | |
399 | static struct virtqueue_ops vring_vq_ops = { | |
400 | .add_buf = vring_add_buf, | |
401 | .get_buf = vring_get_buf, | |
402 | .kick = vring_kick, | |
18445c4d RR |
403 | .disable_cb = vring_disable_cb, |
404 | .enable_cb = vring_enable_cb, | |
c021eac4 | 405 | .detach_unused_buf = vring_detach_unused_buf, |
0a8a69dd RR |
406 | }; |
407 | ||
408 | struct virtqueue *vring_new_virtqueue(unsigned int num, | |
87c7d57c | 409 | unsigned int vring_align, |
0a8a69dd RR |
410 | struct virtio_device *vdev, |
411 | void *pages, | |
412 | void (*notify)(struct virtqueue *), | |
9499f5e7 RR |
413 | void (*callback)(struct virtqueue *), |
414 | const char *name) | |
0a8a69dd RR |
415 | { |
416 | struct vring_virtqueue *vq; | |
417 | unsigned int i; | |
418 | ||
42b36cc0 RR |
419 | /* We assume num is a power of 2. */ |
420 | if (num & (num - 1)) { | |
421 | dev_warn(&vdev->dev, "Bad virtqueue length %u\n", num); | |
422 | return NULL; | |
423 | } | |
424 | ||
0a8a69dd RR |
425 | vq = kmalloc(sizeof(*vq) + sizeof(void *)*num, GFP_KERNEL); |
426 | if (!vq) | |
427 | return NULL; | |
428 | ||
87c7d57c | 429 | vring_init(&vq->vring, num, pages, vring_align); |
0a8a69dd RR |
430 | vq->vq.callback = callback; |
431 | vq->vq.vdev = vdev; | |
432 | vq->vq.vq_ops = &vring_vq_ops; | |
9499f5e7 | 433 | vq->vq.name = name; |
0a8a69dd RR |
434 | vq->notify = notify; |
435 | vq->broken = false; | |
436 | vq->last_used_idx = 0; | |
437 | vq->num_added = 0; | |
9499f5e7 | 438 | list_add_tail(&vq->vq.list, &vdev->vqs); |
0a8a69dd RR |
439 | #ifdef DEBUG |
440 | vq->in_use = false; | |
441 | #endif | |
442 | ||
9fa29b9d MM |
443 | vq->indirect = virtio_has_feature(vdev, VIRTIO_RING_F_INDIRECT_DESC); |
444 | ||
0a8a69dd RR |
445 | /* No callback? Tell other side not to bother us. */ |
446 | if (!callback) | |
447 | vq->vring.avail->flags |= VRING_AVAIL_F_NO_INTERRUPT; | |
448 | ||
449 | /* Put everything in free lists. */ | |
450 | vq->num_free = num; | |
451 | vq->free_head = 0; | |
3b870624 | 452 | for (i = 0; i < num-1; i++) { |
0a8a69dd | 453 | vq->vring.desc[i].next = i+1; |
3b870624 AS |
454 | vq->data[i] = NULL; |
455 | } | |
456 | vq->data[i] = NULL; | |
0a8a69dd RR |
457 | |
458 | return &vq->vq; | |
459 | } | |
c6fd4701 | 460 | EXPORT_SYMBOL_GPL(vring_new_virtqueue); |
0a8a69dd RR |
461 | |
462 | void vring_del_virtqueue(struct virtqueue *vq) | |
463 | { | |
9499f5e7 | 464 | list_del(&vq->list); |
0a8a69dd RR |
465 | kfree(to_vvq(vq)); |
466 | } | |
c6fd4701 | 467 | EXPORT_SYMBOL_GPL(vring_del_virtqueue); |
0a8a69dd | 468 | |
e34f8725 RR |
469 | /* Manipulates transport-specific feature bits. */ |
470 | void vring_transport_features(struct virtio_device *vdev) | |
471 | { | |
472 | unsigned int i; | |
473 | ||
474 | for (i = VIRTIO_TRANSPORT_F_START; i < VIRTIO_TRANSPORT_F_END; i++) { | |
475 | switch (i) { | |
9fa29b9d MM |
476 | case VIRTIO_RING_F_INDIRECT_DESC: |
477 | break; | |
e34f8725 RR |
478 | default: |
479 | /* We don't understand this bit. */ | |
480 | clear_bit(i, vdev->features); | |
481 | } | |
482 | } | |
483 | } | |
484 | EXPORT_SYMBOL_GPL(vring_transport_features); | |
485 | ||
c6fd4701 | 486 | MODULE_LICENSE("GPL"); |