Commit | Line | Data |
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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, | |
bbd603ef MT |
113 | unsigned int in, |
114 | gfp_t gfp) | |
9fa29b9d MM |
115 | { |
116 | struct vring_desc *desc; | |
117 | unsigned head; | |
118 | int i; | |
119 | ||
bbd603ef | 120 | desc = kmalloc((out + in) * sizeof(struct vring_desc), gfp); |
9fa29b9d MM |
121 | if (!desc) |
122 | return vq->vring.num; | |
123 | ||
124 | /* Transfer entries from the sg list into the indirect page */ | |
125 | for (i = 0; i < out; i++) { | |
126 | desc[i].flags = VRING_DESC_F_NEXT; | |
127 | desc[i].addr = sg_phys(sg); | |
128 | desc[i].len = sg->length; | |
129 | desc[i].next = i+1; | |
130 | sg++; | |
131 | } | |
132 | for (; i < (out + in); i++) { | |
133 | desc[i].flags = VRING_DESC_F_NEXT|VRING_DESC_F_WRITE; | |
134 | desc[i].addr = sg_phys(sg); | |
135 | desc[i].len = sg->length; | |
136 | desc[i].next = i+1; | |
137 | sg++; | |
138 | } | |
139 | ||
140 | /* Last one doesn't continue. */ | |
141 | desc[i-1].flags &= ~VRING_DESC_F_NEXT; | |
142 | desc[i-1].next = 0; | |
143 | ||
144 | /* We're about to use a buffer */ | |
145 | vq->num_free--; | |
146 | ||
147 | /* Use a single buffer which doesn't continue */ | |
148 | head = vq->free_head; | |
149 | vq->vring.desc[head].flags = VRING_DESC_F_INDIRECT; | |
150 | vq->vring.desc[head].addr = virt_to_phys(desc); | |
151 | vq->vring.desc[head].len = i * sizeof(struct vring_desc); | |
152 | ||
153 | /* Update free pointer */ | |
154 | vq->free_head = vq->vring.desc[head].next; | |
155 | ||
156 | return head; | |
157 | } | |
158 | ||
bbd603ef MT |
159 | int virtqueue_add_buf_gfp(struct virtqueue *_vq, |
160 | struct scatterlist sg[], | |
161 | unsigned int out, | |
162 | unsigned int in, | |
163 | void *data, | |
164 | gfp_t gfp) | |
0a8a69dd RR |
165 | { |
166 | struct vring_virtqueue *vq = to_vvq(_vq); | |
167 | unsigned int i, avail, head, uninitialized_var(prev); | |
168 | ||
9fa29b9d MM |
169 | START_USE(vq); |
170 | ||
0a8a69dd | 171 | BUG_ON(data == NULL); |
9fa29b9d MM |
172 | |
173 | /* If the host supports indirect descriptor tables, and we have multiple | |
174 | * buffers, then go indirect. FIXME: tune this threshold */ | |
175 | if (vq->indirect && (out + in) > 1 && vq->num_free) { | |
bbd603ef | 176 | head = vring_add_indirect(vq, sg, out, in, gfp); |
9fa29b9d MM |
177 | if (head != vq->vring.num) |
178 | goto add_head; | |
179 | } | |
180 | ||
0a8a69dd RR |
181 | BUG_ON(out + in > vq->vring.num); |
182 | BUG_ON(out + in == 0); | |
183 | ||
0a8a69dd RR |
184 | if (vq->num_free < out + in) { |
185 | pr_debug("Can't add buf len %i - avail = %i\n", | |
186 | out + in, vq->num_free); | |
44653eae RR |
187 | /* FIXME: for historical reasons, we force a notify here if |
188 | * there are outgoing parts to the buffer. Presumably the | |
189 | * host should service the ring ASAP. */ | |
190 | if (out) | |
191 | vq->notify(&vq->vq); | |
0a8a69dd RR |
192 | END_USE(vq); |
193 | return -ENOSPC; | |
194 | } | |
195 | ||
196 | /* We're about to use some buffers from the free list. */ | |
197 | vq->num_free -= out + in; | |
198 | ||
199 | head = vq->free_head; | |
200 | for (i = vq->free_head; out; i = vq->vring.desc[i].next, out--) { | |
201 | vq->vring.desc[i].flags = VRING_DESC_F_NEXT; | |
15f9c890 | 202 | vq->vring.desc[i].addr = sg_phys(sg); |
0a8a69dd RR |
203 | vq->vring.desc[i].len = sg->length; |
204 | prev = i; | |
205 | sg++; | |
206 | } | |
207 | for (; in; i = vq->vring.desc[i].next, in--) { | |
208 | vq->vring.desc[i].flags = VRING_DESC_F_NEXT|VRING_DESC_F_WRITE; | |
15f9c890 | 209 | vq->vring.desc[i].addr = sg_phys(sg); |
0a8a69dd RR |
210 | vq->vring.desc[i].len = sg->length; |
211 | prev = i; | |
212 | sg++; | |
213 | } | |
214 | /* Last one doesn't continue. */ | |
215 | vq->vring.desc[prev].flags &= ~VRING_DESC_F_NEXT; | |
216 | ||
217 | /* Update free pointer */ | |
218 | vq->free_head = i; | |
219 | ||
9fa29b9d | 220 | add_head: |
0a8a69dd RR |
221 | /* Set token. */ |
222 | vq->data[head] = data; | |
223 | ||
224 | /* Put entry in available array (but don't update avail->idx until they | |
225 | * do sync). FIXME: avoid modulus here? */ | |
226 | avail = (vq->vring.avail->idx + vq->num_added++) % vq->vring.num; | |
227 | vq->vring.avail->ring[avail] = head; | |
228 | ||
229 | pr_debug("Added buffer head %i to %p\n", head, vq); | |
230 | END_USE(vq); | |
3c1b27d5 RR |
231 | |
232 | /* If we're indirect, we can fit many (assuming not OOM). */ | |
233 | if (vq->indirect) | |
234 | return vq->num_free ? vq->vring.num : 0; | |
235 | return vq->num_free; | |
0a8a69dd | 236 | } |
bbd603ef | 237 | EXPORT_SYMBOL_GPL(virtqueue_add_buf_gfp); |
0a8a69dd | 238 | |
7c5e9ed0 | 239 | void virtqueue_kick(struct virtqueue *_vq) |
0a8a69dd RR |
240 | { |
241 | struct vring_virtqueue *vq = to_vvq(_vq); | |
242 | START_USE(vq); | |
243 | /* Descriptors and available array need to be set before we expose the | |
244 | * new available array entries. */ | |
d57ed95d | 245 | virtio_wmb(); |
0a8a69dd RR |
246 | |
247 | vq->vring.avail->idx += vq->num_added; | |
248 | vq->num_added = 0; | |
249 | ||
250 | /* Need to update avail index before checking if we should notify */ | |
d57ed95d | 251 | virtio_mb(); |
0a8a69dd RR |
252 | |
253 | if (!(vq->vring.used->flags & VRING_USED_F_NO_NOTIFY)) | |
254 | /* Prod other side to tell it about changes. */ | |
255 | vq->notify(&vq->vq); | |
256 | ||
257 | END_USE(vq); | |
258 | } | |
7c5e9ed0 | 259 | EXPORT_SYMBOL_GPL(virtqueue_kick); |
0a8a69dd RR |
260 | |
261 | static void detach_buf(struct vring_virtqueue *vq, unsigned int head) | |
262 | { | |
263 | unsigned int i; | |
264 | ||
265 | /* Clear data ptr. */ | |
266 | vq->data[head] = NULL; | |
267 | ||
268 | /* Put back on free list: find end */ | |
269 | i = head; | |
9fa29b9d MM |
270 | |
271 | /* Free the indirect table */ | |
272 | if (vq->vring.desc[i].flags & VRING_DESC_F_INDIRECT) | |
273 | kfree(phys_to_virt(vq->vring.desc[i].addr)); | |
274 | ||
0a8a69dd RR |
275 | while (vq->vring.desc[i].flags & VRING_DESC_F_NEXT) { |
276 | i = vq->vring.desc[i].next; | |
277 | vq->num_free++; | |
278 | } | |
279 | ||
280 | vq->vring.desc[i].next = vq->free_head; | |
281 | vq->free_head = head; | |
282 | /* Plus final descriptor */ | |
283 | vq->num_free++; | |
284 | } | |
285 | ||
0a8a69dd RR |
286 | static inline bool more_used(const struct vring_virtqueue *vq) |
287 | { | |
288 | return vq->last_used_idx != vq->vring.used->idx; | |
289 | } | |
290 | ||
7c5e9ed0 | 291 | void *virtqueue_get_buf(struct virtqueue *_vq, unsigned int *len) |
0a8a69dd RR |
292 | { |
293 | struct vring_virtqueue *vq = to_vvq(_vq); | |
294 | void *ret; | |
295 | unsigned int i; | |
296 | ||
297 | START_USE(vq); | |
298 | ||
5ef82752 RR |
299 | if (unlikely(vq->broken)) { |
300 | END_USE(vq); | |
301 | return NULL; | |
302 | } | |
303 | ||
0a8a69dd RR |
304 | if (!more_used(vq)) { |
305 | pr_debug("No more buffers in queue\n"); | |
306 | END_USE(vq); | |
307 | return NULL; | |
308 | } | |
309 | ||
2d61ba95 | 310 | /* Only get used array entries after they have been exposed by host. */ |
d57ed95d | 311 | virtio_rmb(); |
2d61ba95 | 312 | |
0a8a69dd RR |
313 | i = vq->vring.used->ring[vq->last_used_idx%vq->vring.num].id; |
314 | *len = vq->vring.used->ring[vq->last_used_idx%vq->vring.num].len; | |
315 | ||
316 | if (unlikely(i >= vq->vring.num)) { | |
317 | BAD_RING(vq, "id %u out of range\n", i); | |
318 | return NULL; | |
319 | } | |
320 | if (unlikely(!vq->data[i])) { | |
321 | BAD_RING(vq, "id %u is not a head!\n", i); | |
322 | return NULL; | |
323 | } | |
324 | ||
325 | /* detach_buf clears data, so grab it now. */ | |
326 | ret = vq->data[i]; | |
327 | detach_buf(vq, i); | |
328 | vq->last_used_idx++; | |
329 | END_USE(vq); | |
330 | return ret; | |
331 | } | |
7c5e9ed0 | 332 | EXPORT_SYMBOL_GPL(virtqueue_get_buf); |
0a8a69dd | 333 | |
7c5e9ed0 | 334 | void virtqueue_disable_cb(struct virtqueue *_vq) |
18445c4d RR |
335 | { |
336 | struct vring_virtqueue *vq = to_vvq(_vq); | |
337 | ||
18445c4d | 338 | vq->vring.avail->flags |= VRING_AVAIL_F_NO_INTERRUPT; |
18445c4d | 339 | } |
7c5e9ed0 | 340 | EXPORT_SYMBOL_GPL(virtqueue_disable_cb); |
18445c4d | 341 | |
7c5e9ed0 | 342 | bool virtqueue_enable_cb(struct virtqueue *_vq) |
0a8a69dd RR |
343 | { |
344 | struct vring_virtqueue *vq = to_vvq(_vq); | |
345 | ||
346 | START_USE(vq); | |
0a8a69dd RR |
347 | |
348 | /* We optimistically turn back on interrupts, then check if there was | |
349 | * more to do. */ | |
350 | vq->vring.avail->flags &= ~VRING_AVAIL_F_NO_INTERRUPT; | |
d57ed95d | 351 | virtio_mb(); |
0a8a69dd | 352 | if (unlikely(more_used(vq))) { |
0a8a69dd RR |
353 | END_USE(vq); |
354 | return false; | |
355 | } | |
356 | ||
357 | END_USE(vq); | |
358 | return true; | |
359 | } | |
7c5e9ed0 | 360 | EXPORT_SYMBOL_GPL(virtqueue_enable_cb); |
0a8a69dd | 361 | |
7c5e9ed0 | 362 | void *virtqueue_detach_unused_buf(struct virtqueue *_vq) |
c021eac4 SM |
363 | { |
364 | struct vring_virtqueue *vq = to_vvq(_vq); | |
365 | unsigned int i; | |
366 | void *buf; | |
367 | ||
368 | START_USE(vq); | |
369 | ||
370 | for (i = 0; i < vq->vring.num; i++) { | |
371 | if (!vq->data[i]) | |
372 | continue; | |
373 | /* detach_buf clears data, so grab it now. */ | |
374 | buf = vq->data[i]; | |
375 | detach_buf(vq, i); | |
376 | END_USE(vq); | |
377 | return buf; | |
378 | } | |
379 | /* That should have freed everything. */ | |
380 | BUG_ON(vq->num_free != vq->vring.num); | |
381 | ||
382 | END_USE(vq); | |
383 | return NULL; | |
384 | } | |
7c5e9ed0 | 385 | EXPORT_SYMBOL_GPL(virtqueue_detach_unused_buf); |
c021eac4 | 386 | |
0a8a69dd RR |
387 | irqreturn_t vring_interrupt(int irq, void *_vq) |
388 | { | |
389 | struct vring_virtqueue *vq = to_vvq(_vq); | |
390 | ||
391 | if (!more_used(vq)) { | |
392 | pr_debug("virtqueue interrupt with no work for %p\n", vq); | |
393 | return IRQ_NONE; | |
394 | } | |
395 | ||
396 | if (unlikely(vq->broken)) | |
397 | return IRQ_HANDLED; | |
398 | ||
399 | pr_debug("virtqueue callback for %p (%p)\n", vq, vq->vq.callback); | |
18445c4d RR |
400 | if (vq->vq.callback) |
401 | vq->vq.callback(&vq->vq); | |
0a8a69dd RR |
402 | |
403 | return IRQ_HANDLED; | |
404 | } | |
c6fd4701 | 405 | EXPORT_SYMBOL_GPL(vring_interrupt); |
0a8a69dd | 406 | |
0a8a69dd | 407 | struct virtqueue *vring_new_virtqueue(unsigned int num, |
87c7d57c | 408 | unsigned int vring_align, |
0a8a69dd RR |
409 | struct virtio_device *vdev, |
410 | void *pages, | |
411 | void (*notify)(struct virtqueue *), | |
9499f5e7 RR |
412 | void (*callback)(struct virtqueue *), |
413 | const char *name) | |
0a8a69dd RR |
414 | { |
415 | struct vring_virtqueue *vq; | |
416 | unsigned int i; | |
417 | ||
42b36cc0 RR |
418 | /* We assume num is a power of 2. */ |
419 | if (num & (num - 1)) { | |
420 | dev_warn(&vdev->dev, "Bad virtqueue length %u\n", num); | |
421 | return NULL; | |
422 | } | |
423 | ||
0a8a69dd RR |
424 | vq = kmalloc(sizeof(*vq) + sizeof(void *)*num, GFP_KERNEL); |
425 | if (!vq) | |
426 | return NULL; | |
427 | ||
87c7d57c | 428 | vring_init(&vq->vring, num, pages, vring_align); |
0a8a69dd RR |
429 | vq->vq.callback = callback; |
430 | vq->vq.vdev = vdev; | |
9499f5e7 | 431 | vq->vq.name = name; |
0a8a69dd RR |
432 | vq->notify = notify; |
433 | vq->broken = false; | |
434 | vq->last_used_idx = 0; | |
435 | vq->num_added = 0; | |
9499f5e7 | 436 | list_add_tail(&vq->vq.list, &vdev->vqs); |
0a8a69dd RR |
437 | #ifdef DEBUG |
438 | vq->in_use = false; | |
439 | #endif | |
440 | ||
9fa29b9d MM |
441 | vq->indirect = virtio_has_feature(vdev, VIRTIO_RING_F_INDIRECT_DESC); |
442 | ||
0a8a69dd RR |
443 | /* No callback? Tell other side not to bother us. */ |
444 | if (!callback) | |
445 | vq->vring.avail->flags |= VRING_AVAIL_F_NO_INTERRUPT; | |
446 | ||
447 | /* Put everything in free lists. */ | |
448 | vq->num_free = num; | |
449 | vq->free_head = 0; | |
3b870624 | 450 | for (i = 0; i < num-1; i++) { |
0a8a69dd | 451 | vq->vring.desc[i].next = i+1; |
3b870624 AS |
452 | vq->data[i] = NULL; |
453 | } | |
454 | vq->data[i] = NULL; | |
0a8a69dd RR |
455 | |
456 | return &vq->vq; | |
457 | } | |
c6fd4701 | 458 | EXPORT_SYMBOL_GPL(vring_new_virtqueue); |
0a8a69dd RR |
459 | |
460 | void vring_del_virtqueue(struct virtqueue *vq) | |
461 | { | |
9499f5e7 | 462 | list_del(&vq->list); |
0a8a69dd RR |
463 | kfree(to_vvq(vq)); |
464 | } | |
c6fd4701 | 465 | EXPORT_SYMBOL_GPL(vring_del_virtqueue); |
0a8a69dd | 466 | |
e34f8725 RR |
467 | /* Manipulates transport-specific feature bits. */ |
468 | void vring_transport_features(struct virtio_device *vdev) | |
469 | { | |
470 | unsigned int i; | |
471 | ||
472 | for (i = VIRTIO_TRANSPORT_F_START; i < VIRTIO_TRANSPORT_F_END; i++) { | |
473 | switch (i) { | |
9fa29b9d MM |
474 | case VIRTIO_RING_F_INDIRECT_DESC: |
475 | break; | |
e34f8725 RR |
476 | default: |
477 | /* We don't understand this bit. */ | |
478 | clear_bit(i, vdev->features); | |
479 | } | |
480 | } | |
481 | } | |
482 | EXPORT_SYMBOL_GPL(vring_transport_features); | |
483 | ||
c6fd4701 | 484 | MODULE_LICENSE("GPL"); |