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> 21 #include <linux/virtio_config.h> 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, args...) \ 27 do { \ 28 dev_err(&(_vq)->vq.vdev->dev, \ 29 "%s:"fmt, (_vq)->vq.name, ##args); \ 30 BUG(); \ 31 } while (0) 32 /* Caller is supposed to guarantee no reentry. */ 33 #define START_USE(_vq) \ 34 do { \ 35 if ((_vq)->in_use) \ 36 panic("%s:in_use = %i\n", \ 37 (_vq)->vq.name, (_vq)->in_use); \ 38 (_vq)->in_use = __LINE__; \ 39 mb(); \ 40 } while (0) 41 #define END_USE(_vq) \ 42 do { BUG_ON(!(_vq)->in_use); (_vq)->in_use = 0; mb(); } while(0) 43 #else 44 #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) 50 #define START_USE(vq) 51 #define END_USE(vq) 52 #endif 53 54 struct 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 64 /* Host supports indirect buffers */ 65 bool indirect; 66 67 /* 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. */ 75 u16 last_used_idx; 76 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 91 /* Set up an indirect table of descriptors and add it to the queue. */ 92 static 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 } 139 140 static 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); 148 149 START_USE(vq); 150 151 BUG_ON(data == NULL); 152 153 /* 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 } 160 161 BUG_ON(out + in > vq->vring.num); 162 BUG_ON(out + in == 0); 163 164 if (vq->num_free < out + in) { 165 pr_debug("Can't add buf len %i - avail = %i\n", 166 out + in, vq->num_free); 167 /* 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); 172 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; 182 vq->vring.desc[i].addr = sg_phys(sg); 183 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; 189 vq->vring.desc[i].addr = sg_phys(sg); 190 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; 199 200 add_head: 201 /* 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); 211 212 /* 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; 216 } 217 218 static 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 } 238 239 static 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; 248 249 /* 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)); 252 253 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 } 263 264 static inline bool more_used(const struct vring_virtqueue *vq) 265 { 266 return vq->last_used_idx != vq->vring.used->idx; 267 } 268 269 static 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); 276 277 if (unlikely(vq->broken)) { 278 END_USE(vq); 279 return NULL; 280 } 281 282 if (!more_used(vq)) { 283 pr_debug("No more buffers in queue\n"); 284 END_USE(vq); 285 return NULL; 286 } 287 288 i = vq->vring.used->ring[vq->last_used_idx%vq->vring.num].id; 289 *len = vq->vring.used->ring[vq->last_used_idx%vq->vring.num].len; 290 291 if (unlikely(i >= vq->vring.num)) { 292 BAD_RING(vq, "id %u out of range\n", i); 293 return NULL; 294 } 295 if (unlikely(!vq->data[i])) { 296 BAD_RING(vq, "id %u is not a head!\n", i); 297 return NULL; 298 } 299 300 /* detach_buf clears data, so grab it now. */ 301 ret = vq->data[i]; 302 detach_buf(vq, i); 303 vq->last_used_idx++; 304 END_USE(vq); 305 return ret; 306 } 307 308 static void vring_disable_cb(struct virtqueue *_vq) 309 { 310 struct vring_virtqueue *vq = to_vvq(_vq); 311 312 vq->vring.avail->flags |= VRING_AVAIL_F_NO_INTERRUPT; 313 } 314 315 static bool vring_enable_cb(struct virtqueue *_vq) 316 { 317 struct vring_virtqueue *vq = to_vvq(_vq); 318 319 START_USE(vq); 320 321 /* We optimistically turn back on interrupts, then check if there was 322 * more to do. */ 323 vq->vring.avail->flags &= ~VRING_AVAIL_F_NO_INTERRUPT; 324 mb(); 325 if (unlikely(more_used(vq))) { 326 END_USE(vq); 327 return false; 328 } 329 330 END_USE(vq); 331 return true; 332 } 333 334 irqreturn_t vring_interrupt(int irq, void *_vq) 335 { 336 struct vring_virtqueue *vq = to_vvq(_vq); 337 338 if (!more_used(vq)) { 339 pr_debug("virtqueue interrupt with no work for %p\n", vq); 340 return IRQ_NONE; 341 } 342 343 if (unlikely(vq->broken)) 344 return IRQ_HANDLED; 345 346 pr_debug("virtqueue callback for %p (%p)\n", vq, vq->vq.callback); 347 if (vq->vq.callback) 348 vq->vq.callback(&vq->vq); 349 350 return IRQ_HANDLED; 351 } 352 EXPORT_SYMBOL_GPL(vring_interrupt); 353 354 static struct virtqueue_ops vring_vq_ops = { 355 .add_buf = vring_add_buf, 356 .get_buf = vring_get_buf, 357 .kick = vring_kick, 358 .disable_cb = vring_disable_cb, 359 .enable_cb = vring_enable_cb, 360 }; 361 362 struct virtqueue *vring_new_virtqueue(unsigned int num, 363 unsigned int vring_align, 364 struct virtio_device *vdev, 365 void *pages, 366 void (*notify)(struct virtqueue *), 367 void (*callback)(struct virtqueue *), 368 const char *name) 369 { 370 struct vring_virtqueue *vq; 371 unsigned int i; 372 373 /* We assume num is a power of 2. */ 374 if (num & (num - 1)) { 375 dev_warn(&vdev->dev, "Bad virtqueue length %u\n", num); 376 return NULL; 377 } 378 379 vq = kmalloc(sizeof(*vq) + sizeof(void *)*num, GFP_KERNEL); 380 if (!vq) 381 return NULL; 382 383 vring_init(&vq->vring, num, pages, vring_align); 384 vq->vq.callback = callback; 385 vq->vq.vdev = vdev; 386 vq->vq.vq_ops = &vring_vq_ops; 387 vq->vq.name = name; 388 vq->notify = notify; 389 vq->broken = false; 390 vq->last_used_idx = 0; 391 vq->num_added = 0; 392 list_add_tail(&vq->vq.list, &vdev->vqs); 393 #ifdef DEBUG 394 vq->in_use = false; 395 #endif 396 397 vq->indirect = virtio_has_feature(vdev, VIRTIO_RING_F_INDIRECT_DESC); 398 399 /* No callback? Tell other side not to bother us. */ 400 if (!callback) 401 vq->vring.avail->flags |= VRING_AVAIL_F_NO_INTERRUPT; 402 403 /* Put everything in free lists. */ 404 vq->num_free = num; 405 vq->free_head = 0; 406 for (i = 0; i < num-1; i++) 407 vq->vring.desc[i].next = i+1; 408 409 return &vq->vq; 410 } 411 EXPORT_SYMBOL_GPL(vring_new_virtqueue); 412 413 void vring_del_virtqueue(struct virtqueue *vq) 414 { 415 list_del(&vq->list); 416 kfree(to_vvq(vq)); 417 } 418 EXPORT_SYMBOL_GPL(vring_del_virtqueue); 419 420 /* Manipulates transport-specific feature bits. */ 421 void vring_transport_features(struct virtio_device *vdev) 422 { 423 unsigned int i; 424 425 for (i = VIRTIO_TRANSPORT_F_START; i < VIRTIO_TRANSPORT_F_END; i++) { 426 switch (i) { 427 case VIRTIO_RING_F_INDIRECT_DESC: 428 break; 429 default: 430 /* We don't understand this bit. */ 431 clear_bit(i, vdev->features); 432 } 433 } 434 } 435 EXPORT_SYMBOL_GPL(vring_transport_features); 436 437 MODULE_LICENSE("GPL"); 438