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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 RR |
22 | #include <linux/device.h> |
23 | ||
24 | #ifdef DEBUG | |
25 | /* For development, we want to crash whenever the ring is screwed. */ | |
26 | #define BAD_RING(vq, fmt...) \ | |
27 | do { dev_err(&vq->vq.vdev->dev, fmt); BUG(); } while(0) | |
28 | #define START_USE(vq) \ | |
29 | do { if ((vq)->in_use) panic("in_use = %i\n", (vq)->in_use); (vq)->in_use = __LINE__; mb(); } while(0) | |
30 | #define END_USE(vq) \ | |
31 | do { BUG_ON(!(vq)->in_use); (vq)->in_use = 0; mb(); } while(0) | |
32 | #else | |
33 | #define BAD_RING(vq, fmt...) \ | |
34 | do { dev_err(&vq->vq.vdev->dev, fmt); (vq)->broken = true; } while(0) | |
35 | #define START_USE(vq) | |
36 | #define END_USE(vq) | |
37 | #endif | |
38 | ||
39 | struct vring_virtqueue | |
40 | { | |
41 | struct virtqueue vq; | |
42 | ||
43 | /* Actual memory layout for this queue */ | |
44 | struct vring vring; | |
45 | ||
46 | /* Other side has made a mess, don't try any more. */ | |
47 | bool broken; | |
48 | ||
49 | /* Number of free buffers */ | |
50 | unsigned int num_free; | |
51 | /* Head of free buffer list. */ | |
52 | unsigned int free_head; | |
53 | /* Number we've added since last sync. */ | |
54 | unsigned int num_added; | |
55 | ||
56 | /* Last used index we've seen. */ | |
1bc4953e | 57 | u16 last_used_idx; |
0a8a69dd RR |
58 | |
59 | /* How to notify other side. FIXME: commonalize hcalls! */ | |
60 | void (*notify)(struct virtqueue *vq); | |
61 | ||
62 | #ifdef DEBUG | |
63 | /* They're supposed to lock for us. */ | |
64 | unsigned int in_use; | |
65 | #endif | |
66 | ||
67 | /* Tokens for callbacks. */ | |
68 | void *data[]; | |
69 | }; | |
70 | ||
71 | #define to_vvq(_vq) container_of(_vq, struct vring_virtqueue, vq) | |
72 | ||
73 | static int vring_add_buf(struct virtqueue *_vq, | |
74 | struct scatterlist sg[], | |
75 | unsigned int out, | |
76 | unsigned int in, | |
77 | void *data) | |
78 | { | |
79 | struct vring_virtqueue *vq = to_vvq(_vq); | |
80 | unsigned int i, avail, head, uninitialized_var(prev); | |
81 | ||
82 | BUG_ON(data == NULL); | |
83 | BUG_ON(out + in > vq->vring.num); | |
84 | BUG_ON(out + in == 0); | |
85 | ||
86 | START_USE(vq); | |
87 | ||
88 | if (vq->num_free < out + in) { | |
89 | pr_debug("Can't add buf len %i - avail = %i\n", | |
90 | out + in, vq->num_free); | |
44653eae RR |
91 | /* FIXME: for historical reasons, we force a notify here if |
92 | * there are outgoing parts to the buffer. Presumably the | |
93 | * host should service the ring ASAP. */ | |
94 | if (out) | |
95 | vq->notify(&vq->vq); | |
0a8a69dd RR |
96 | END_USE(vq); |
97 | return -ENOSPC; | |
98 | } | |
99 | ||
100 | /* We're about to use some buffers from the free list. */ | |
101 | vq->num_free -= out + in; | |
102 | ||
103 | head = vq->free_head; | |
104 | for (i = vq->free_head; out; i = vq->vring.desc[i].next, out--) { | |
105 | vq->vring.desc[i].flags = VRING_DESC_F_NEXT; | |
15f9c890 | 106 | vq->vring.desc[i].addr = sg_phys(sg); |
0a8a69dd RR |
107 | vq->vring.desc[i].len = sg->length; |
108 | prev = i; | |
109 | sg++; | |
110 | } | |
111 | for (; in; i = vq->vring.desc[i].next, in--) { | |
112 | vq->vring.desc[i].flags = VRING_DESC_F_NEXT|VRING_DESC_F_WRITE; | |
15f9c890 | 113 | vq->vring.desc[i].addr = sg_phys(sg); |
0a8a69dd RR |
114 | vq->vring.desc[i].len = sg->length; |
115 | prev = i; | |
116 | sg++; | |
117 | } | |
118 | /* Last one doesn't continue. */ | |
119 | vq->vring.desc[prev].flags &= ~VRING_DESC_F_NEXT; | |
120 | ||
121 | /* Update free pointer */ | |
122 | vq->free_head = i; | |
123 | ||
124 | /* Set token. */ | |
125 | vq->data[head] = data; | |
126 | ||
127 | /* Put entry in available array (but don't update avail->idx until they | |
128 | * do sync). FIXME: avoid modulus here? */ | |
129 | avail = (vq->vring.avail->idx + vq->num_added++) % vq->vring.num; | |
130 | vq->vring.avail->ring[avail] = head; | |
131 | ||
132 | pr_debug("Added buffer head %i to %p\n", head, vq); | |
133 | END_USE(vq); | |
134 | return 0; | |
135 | } | |
136 | ||
137 | static void vring_kick(struct virtqueue *_vq) | |
138 | { | |
139 | struct vring_virtqueue *vq = to_vvq(_vq); | |
140 | START_USE(vq); | |
141 | /* Descriptors and available array need to be set before we expose the | |
142 | * new available array entries. */ | |
143 | wmb(); | |
144 | ||
145 | vq->vring.avail->idx += vq->num_added; | |
146 | vq->num_added = 0; | |
147 | ||
148 | /* Need to update avail index before checking if we should notify */ | |
149 | mb(); | |
150 | ||
151 | if (!(vq->vring.used->flags & VRING_USED_F_NO_NOTIFY)) | |
152 | /* Prod other side to tell it about changes. */ | |
153 | vq->notify(&vq->vq); | |
154 | ||
155 | END_USE(vq); | |
156 | } | |
157 | ||
158 | static void detach_buf(struct vring_virtqueue *vq, unsigned int head) | |
159 | { | |
160 | unsigned int i; | |
161 | ||
162 | /* Clear data ptr. */ | |
163 | vq->data[head] = NULL; | |
164 | ||
165 | /* Put back on free list: find end */ | |
166 | i = head; | |
167 | while (vq->vring.desc[i].flags & VRING_DESC_F_NEXT) { | |
168 | i = vq->vring.desc[i].next; | |
169 | vq->num_free++; | |
170 | } | |
171 | ||
172 | vq->vring.desc[i].next = vq->free_head; | |
173 | vq->free_head = head; | |
174 | /* Plus final descriptor */ | |
175 | vq->num_free++; | |
176 | } | |
177 | ||
0a8a69dd RR |
178 | static inline bool more_used(const struct vring_virtqueue *vq) |
179 | { | |
180 | return vq->last_used_idx != vq->vring.used->idx; | |
181 | } | |
182 | ||
183 | static void *vring_get_buf(struct virtqueue *_vq, unsigned int *len) | |
184 | { | |
185 | struct vring_virtqueue *vq = to_vvq(_vq); | |
186 | void *ret; | |
187 | unsigned int i; | |
188 | ||
189 | START_USE(vq); | |
190 | ||
5ef82752 RR |
191 | if (unlikely(vq->broken)) { |
192 | END_USE(vq); | |
193 | return NULL; | |
194 | } | |
195 | ||
0a8a69dd RR |
196 | if (!more_used(vq)) { |
197 | pr_debug("No more buffers in queue\n"); | |
198 | END_USE(vq); | |
199 | return NULL; | |
200 | } | |
201 | ||
202 | i = vq->vring.used->ring[vq->last_used_idx%vq->vring.num].id; | |
203 | *len = vq->vring.used->ring[vq->last_used_idx%vq->vring.num].len; | |
204 | ||
205 | if (unlikely(i >= vq->vring.num)) { | |
206 | BAD_RING(vq, "id %u out of range\n", i); | |
207 | return NULL; | |
208 | } | |
209 | if (unlikely(!vq->data[i])) { | |
210 | BAD_RING(vq, "id %u is not a head!\n", i); | |
211 | return NULL; | |
212 | } | |
213 | ||
214 | /* detach_buf clears data, so grab it now. */ | |
215 | ret = vq->data[i]; | |
216 | detach_buf(vq, i); | |
217 | vq->last_used_idx++; | |
218 | END_USE(vq); | |
219 | return ret; | |
220 | } | |
221 | ||
18445c4d RR |
222 | static void vring_disable_cb(struct virtqueue *_vq) |
223 | { | |
224 | struct vring_virtqueue *vq = to_vvq(_vq); | |
225 | ||
18445c4d | 226 | vq->vring.avail->flags |= VRING_AVAIL_F_NO_INTERRUPT; |
18445c4d RR |
227 | } |
228 | ||
229 | static bool vring_enable_cb(struct virtqueue *_vq) | |
0a8a69dd RR |
230 | { |
231 | struct vring_virtqueue *vq = to_vvq(_vq); | |
232 | ||
233 | START_USE(vq); | |
0a8a69dd RR |
234 | |
235 | /* We optimistically turn back on interrupts, then check if there was | |
236 | * more to do. */ | |
237 | vq->vring.avail->flags &= ~VRING_AVAIL_F_NO_INTERRUPT; | |
238 | mb(); | |
239 | if (unlikely(more_used(vq))) { | |
0a8a69dd RR |
240 | END_USE(vq); |
241 | return false; | |
242 | } | |
243 | ||
244 | END_USE(vq); | |
245 | return true; | |
246 | } | |
247 | ||
248 | irqreturn_t vring_interrupt(int irq, void *_vq) | |
249 | { | |
250 | struct vring_virtqueue *vq = to_vvq(_vq); | |
251 | ||
252 | if (!more_used(vq)) { | |
253 | pr_debug("virtqueue interrupt with no work for %p\n", vq); | |
254 | return IRQ_NONE; | |
255 | } | |
256 | ||
257 | if (unlikely(vq->broken)) | |
258 | return IRQ_HANDLED; | |
259 | ||
260 | pr_debug("virtqueue callback for %p (%p)\n", vq, vq->vq.callback); | |
18445c4d RR |
261 | if (vq->vq.callback) |
262 | vq->vq.callback(&vq->vq); | |
0a8a69dd RR |
263 | |
264 | return IRQ_HANDLED; | |
265 | } | |
c6fd4701 | 266 | EXPORT_SYMBOL_GPL(vring_interrupt); |
0a8a69dd RR |
267 | |
268 | static struct virtqueue_ops vring_vq_ops = { | |
269 | .add_buf = vring_add_buf, | |
270 | .get_buf = vring_get_buf, | |
271 | .kick = vring_kick, | |
18445c4d RR |
272 | .disable_cb = vring_disable_cb, |
273 | .enable_cb = vring_enable_cb, | |
0a8a69dd RR |
274 | }; |
275 | ||
276 | struct virtqueue *vring_new_virtqueue(unsigned int num, | |
87c7d57c | 277 | unsigned int vring_align, |
0a8a69dd RR |
278 | struct virtio_device *vdev, |
279 | void *pages, | |
280 | void (*notify)(struct virtqueue *), | |
18445c4d | 281 | void (*callback)(struct virtqueue *)) |
0a8a69dd RR |
282 | { |
283 | struct vring_virtqueue *vq; | |
284 | unsigned int i; | |
285 | ||
42b36cc0 RR |
286 | /* We assume num is a power of 2. */ |
287 | if (num & (num - 1)) { | |
288 | dev_warn(&vdev->dev, "Bad virtqueue length %u\n", num); | |
289 | return NULL; | |
290 | } | |
291 | ||
0a8a69dd RR |
292 | vq = kmalloc(sizeof(*vq) + sizeof(void *)*num, GFP_KERNEL); |
293 | if (!vq) | |
294 | return NULL; | |
295 | ||
87c7d57c | 296 | vring_init(&vq->vring, num, pages, vring_align); |
0a8a69dd RR |
297 | vq->vq.callback = callback; |
298 | vq->vq.vdev = vdev; | |
299 | vq->vq.vq_ops = &vring_vq_ops; | |
300 | vq->notify = notify; | |
301 | vq->broken = false; | |
302 | vq->last_used_idx = 0; | |
303 | vq->num_added = 0; | |
304 | #ifdef DEBUG | |
305 | vq->in_use = false; | |
306 | #endif | |
307 | ||
308 | /* No callback? Tell other side not to bother us. */ | |
309 | if (!callback) | |
310 | vq->vring.avail->flags |= VRING_AVAIL_F_NO_INTERRUPT; | |
311 | ||
312 | /* Put everything in free lists. */ | |
313 | vq->num_free = num; | |
314 | vq->free_head = 0; | |
315 | for (i = 0; i < num-1; i++) | |
316 | vq->vring.desc[i].next = i+1; | |
317 | ||
318 | return &vq->vq; | |
319 | } | |
c6fd4701 | 320 | EXPORT_SYMBOL_GPL(vring_new_virtqueue); |
0a8a69dd RR |
321 | |
322 | void vring_del_virtqueue(struct virtqueue *vq) | |
323 | { | |
324 | kfree(to_vvq(vq)); | |
325 | } | |
c6fd4701 | 326 | EXPORT_SYMBOL_GPL(vring_del_virtqueue); |
0a8a69dd | 327 | |
e34f8725 RR |
328 | /* Manipulates transport-specific feature bits. */ |
329 | void vring_transport_features(struct virtio_device *vdev) | |
330 | { | |
331 | unsigned int i; | |
332 | ||
333 | for (i = VIRTIO_TRANSPORT_F_START; i < VIRTIO_TRANSPORT_F_END; i++) { | |
334 | switch (i) { | |
335 | default: | |
336 | /* We don't understand this bit. */ | |
337 | clear_bit(i, vdev->features); | |
338 | } | |
339 | } | |
340 | } | |
341 | EXPORT_SYMBOL_GPL(vring_transport_features); | |
342 | ||
c6fd4701 | 343 | MODULE_LICENSE("GPL"); |