ring.h revision 1.1
1 /****************************************************************************** 2 * ring.h 3 * 4 * Shared producer-consumer ring macros. 5 * 6 * Permission is hereby granted, free of charge, to any person obtaining a copy 7 * of this software and associated documentation files (the "Software"), to 8 * deal in the Software without restriction, including without limitation the 9 * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or 10 * sell copies of the Software, and to permit persons to whom the Software is 11 * furnished to do so, subject to the following conditions: 12 * 13 * The above copyright notice and this permission notice shall be included in 14 * all copies or substantial portions of the Software. 15 * 16 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR 17 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 18 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE 19 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER 20 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING 21 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER 22 * DEALINGS IN THE SOFTWARE. 23 * 24 * Tim Deegan and Andrew Warfield November 2004. 25 */ 26 27 #ifndef __XEN_PUBLIC_IO_RING_H__ 28 #define __XEN_PUBLIC_IO_RING_H__ 29 30 /* 31 * When #include'ing this header, you need to provide the following 32 * declaration upfront: 33 * - standard integers types (uint8_t, uint16_t, etc) 34 * They are provided by stdint.h of the standard headers. 35 * 36 * In addition, if you intend to use the FLEX macros, you also need to 37 * provide the following, before invoking the FLEX macros: 38 * - size_t 39 * - memcpy 40 * - grant_ref_t 41 * These declarations are provided by string.h of the standard headers, 42 * and grant_table.h from the Xen public headers. 43 */ 44 45 #include "../xen-compat.h" 46 47 #if __XEN_INTERFACE_VERSION__ < 0x00030208 48 #define xen_mb() mb() 49 #define xen_rmb() rmb() 50 #define xen_wmb() wmb() 51 #endif 52 53 typedef unsigned int RING_IDX; 54 55 /* Round a 32-bit unsigned constant down to the nearest power of two. */ 56 #define __RD2(_x) (((_x) & 0x00000002) ? 0x2 : ((_x) & 0x1)) 57 #define __RD4(_x) (((_x) & 0x0000000c) ? __RD2((_x)>>2)<<2 : __RD2(_x)) 58 #define __RD8(_x) (((_x) & 0x000000f0) ? __RD4((_x)>>4)<<4 : __RD4(_x)) 59 #define __RD16(_x) (((_x) & 0x0000ff00) ? __RD8((_x)>>8)<<8 : __RD8(_x)) 60 #define __RD32(_x) (((_x) & 0xffff0000) ? __RD16((_x)>>16)<<16 : __RD16(_x)) 61 62 /* 63 * Calculate size of a shared ring, given the total available space for the 64 * ring and indexes (_sz), and the name tag of the request/response structure. 65 * A ring contains as many entries as will fit, rounded down to the nearest 66 * power of two (so we can mask with (size-1) to loop around). 67 */ 68 #define __CONST_RING_SIZE(_s, _sz) \ 69 (__RD32(((_sz) - offsetof(struct _s##_sring, ring)) / \ 70 sizeof(((struct _s##_sring *)0)->ring[0]))) 71 /* 72 * The same for passing in an actual pointer instead of a name tag. 73 */ 74 #define __RING_SIZE(_s, _sz) \ 75 (__RD32(((_sz) - (long)(_s)->ring + (long)(_s)) / sizeof((_s)->ring[0]))) 76 77 /* 78 * Macros to make the correct C datatypes for a new kind of ring. 79 * 80 * To make a new ring datatype, you need to have two message structures, 81 * let's say request_t, and response_t already defined. 82 * 83 * In a header where you want the ring datatype declared, you then do: 84 * 85 * DEFINE_RING_TYPES(mytag, request_t, response_t); 86 * 87 * These expand out to give you a set of types, as you can see below. 88 * The most important of these are: 89 * 90 * mytag_sring_t - The shared ring. 91 * mytag_front_ring_t - The 'front' half of the ring. 92 * mytag_back_ring_t - The 'back' half of the ring. 93 * 94 * To initialize a ring in your code you need to know the location and size 95 * of the shared memory area (PAGE_SIZE, for instance). To initialise 96 * the front half: 97 * 98 * mytag_front_ring_t front_ring; 99 * SHARED_RING_INIT((mytag_sring_t *)shared_page); 100 * FRONT_RING_INIT(&front_ring, (mytag_sring_t *)shared_page, PAGE_SIZE); 101 * 102 * Initializing the back follows similarly (note that only the front 103 * initializes the shared ring): 104 * 105 * mytag_back_ring_t back_ring; 106 * BACK_RING_INIT(&back_ring, (mytag_sring_t *)shared_page, PAGE_SIZE); 107 */ 108 109 #define DEFINE_RING_TYPES(__name, __req_t, __rsp_t) \ 110 \ 111 /* Shared ring entry */ \ 112 union __name##_sring_entry { \ 113 __req_t req; \ 114 __rsp_t rsp; \ 115 }; \ 116 \ 117 /* Shared ring page */ \ 118 struct __name##_sring { \ 119 RING_IDX req_prod, req_event; \ 120 RING_IDX rsp_prod, rsp_event; \ 121 union { \ 122 struct { \ 123 uint8_t smartpoll_active; \ 124 } netif; \ 125 struct { \ 126 uint8_t msg; \ 127 } tapif_user; \ 128 uint8_t pvt_pad[4]; \ 129 } pvt; \ 130 uint8_t __pad[44]; \ 131 union __name##_sring_entry ring[1]; /* variable-length */ \ 132 }; \ 133 \ 134 /* "Front" end's private variables */ \ 135 struct __name##_front_ring { \ 136 RING_IDX req_prod_pvt; \ 137 RING_IDX rsp_cons; \ 138 unsigned int nr_ents; \ 139 struct __name##_sring *sring; \ 140 }; \ 141 \ 142 /* "Back" end's private variables */ \ 143 struct __name##_back_ring { \ 144 RING_IDX rsp_prod_pvt; \ 145 RING_IDX req_cons; \ 146 unsigned int nr_ents; \ 147 struct __name##_sring *sring; \ 148 }; \ 149 \ 150 /* Syntactic sugar */ \ 151 typedef struct __name##_sring __name##_sring_t; \ 152 typedef struct __name##_front_ring __name##_front_ring_t; \ 153 typedef struct __name##_back_ring __name##_back_ring_t 154 155 /* 156 * Macros for manipulating rings. 157 * 158 * FRONT_RING_whatever works on the "front end" of a ring: here 159 * requests are pushed on to the ring and responses taken off it. 160 * 161 * BACK_RING_whatever works on the "back end" of a ring: here 162 * requests are taken off the ring and responses put on. 163 * 164 * N.B. these macros do NO INTERLOCKS OR FLOW CONTROL. 165 * This is OK in 1-for-1 request-response situations where the 166 * requestor (front end) never has more than RING_SIZE()-1 167 * outstanding requests. 168 */ 169 170 /* Initialising empty rings */ 171 #define SHARED_RING_INIT(_s) do { \ 172 (_s)->req_prod = (_s)->rsp_prod = 0; \ 173 (_s)->req_event = (_s)->rsp_event = 1; \ 174 (void)memset((_s)->pvt.pvt_pad, 0, sizeof((_s)->pvt.pvt_pad)); \ 175 (void)memset((_s)->__pad, 0, sizeof((_s)->__pad)); \ 176 } while(0) 177 178 #define FRONT_RING_INIT(_r, _s, __size) do { \ 179 (_r)->req_prod_pvt = 0; \ 180 (_r)->rsp_cons = 0; \ 181 (_r)->nr_ents = __RING_SIZE(_s, __size); \ 182 (_r)->sring = (_s); \ 183 } while (0) 184 185 #define BACK_RING_INIT(_r, _s, __size) do { \ 186 (_r)->rsp_prod_pvt = 0; \ 187 (_r)->req_cons = 0; \ 188 (_r)->nr_ents = __RING_SIZE(_s, __size); \ 189 (_r)->sring = (_s); \ 190 } while (0) 191 192 /* How big is this ring? */ 193 #define RING_SIZE(_r) \ 194 ((_r)->nr_ents) 195 196 /* Number of free requests (for use on front side only). */ 197 #define RING_FREE_REQUESTS(_r) \ 198 (RING_SIZE(_r) - ((_r)->req_prod_pvt - (_r)->rsp_cons)) 199 200 /* Test if there is an empty slot available on the front ring. 201 * (This is only meaningful from the front. ) 202 */ 203 #define RING_FULL(_r) \ 204 (RING_FREE_REQUESTS(_r) == 0) 205 206 /* Test if there are outstanding messages to be processed on a ring. */ 207 #define RING_HAS_UNCONSUMED_RESPONSES(_r) \ 208 ((_r)->sring->rsp_prod - (_r)->rsp_cons) 209 210 #ifdef __GNUC__ 211 #define RING_HAS_UNCONSUMED_REQUESTS(_r) ({ \ 212 unsigned int req = (_r)->sring->req_prod - (_r)->req_cons; \ 213 unsigned int rsp = RING_SIZE(_r) - \ 214 ((_r)->req_cons - (_r)->rsp_prod_pvt); \ 215 req < rsp ? req : rsp; \ 216 }) 217 #else 218 /* Same as above, but without the nice GCC ({ ... }) syntax. */ 219 #define RING_HAS_UNCONSUMED_REQUESTS(_r) \ 220 ((((_r)->sring->req_prod - (_r)->req_cons) < \ 221 (RING_SIZE(_r) - ((_r)->req_cons - (_r)->rsp_prod_pvt))) ? \ 222 ((_r)->sring->req_prod - (_r)->req_cons) : \ 223 (RING_SIZE(_r) - ((_r)->req_cons - (_r)->rsp_prod_pvt))) 224 #endif 225 226 /* Direct access to individual ring elements, by index. */ 227 #define RING_GET_REQUEST(_r, _idx) \ 228 (&((_r)->sring->ring[((_idx) & (RING_SIZE(_r) - 1))].req)) 229 230 /* 231 * Get a local copy of a request. 232 * 233 * Use this in preference to RING_GET_REQUEST() so all processing is 234 * done on a local copy that cannot be modified by the other end. 235 * 236 * Note that https://gcc.gnu.org/bugzilla/show_bug.cgi?id=58145 may cause this 237 * to be ineffective where _req is a struct which consists of only bitfields. 238 */ 239 #define RING_COPY_REQUEST(_r, _idx, _req) do { \ 240 /* Use volatile to force the copy into _req. */ \ 241 *(_req) = *(volatile typeof(_req))RING_GET_REQUEST(_r, _idx); \ 242 } while (0) 243 244 #define RING_GET_RESPONSE(_r, _idx) \ 245 (&((_r)->sring->ring[((_idx) & (RING_SIZE(_r) - 1))].rsp)) 246 247 /* Loop termination condition: Would the specified index overflow the ring? */ 248 #define RING_REQUEST_CONS_OVERFLOW(_r, _cons) \ 249 (((_cons) - (_r)->rsp_prod_pvt) >= RING_SIZE(_r)) 250 251 /* Ill-behaved frontend determination: Can there be this many requests? */ 252 #define RING_REQUEST_PROD_OVERFLOW(_r, _prod) \ 253 (((_prod) - (_r)->rsp_prod_pvt) > RING_SIZE(_r)) 254 255 #define RING_PUSH_REQUESTS(_r) do { \ 256 xen_wmb(); /* back sees requests /before/ updated producer index */ \ 257 (_r)->sring->req_prod = (_r)->req_prod_pvt; \ 258 } while (0) 259 260 #define RING_PUSH_RESPONSES(_r) do { \ 261 xen_wmb(); /* front sees resps /before/ updated producer index */ \ 262 (_r)->sring->rsp_prod = (_r)->rsp_prod_pvt; \ 263 } while (0) 264 265 /* 266 * Notification hold-off (req_event and rsp_event): 267 * 268 * When queueing requests or responses on a shared ring, it may not always be 269 * necessary to notify the remote end. For example, if requests are in flight 270 * in a backend, the front may be able to queue further requests without 271 * notifying the back (if the back checks for new requests when it queues 272 * responses). 273 * 274 * When enqueuing requests or responses: 275 * 276 * Use RING_PUSH_{REQUESTS,RESPONSES}_AND_CHECK_NOTIFY(). The second argument 277 * is a boolean return value. True indicates that the receiver requires an 278 * asynchronous notification. 279 * 280 * After dequeuing requests or responses (before sleeping the connection): 281 * 282 * Use RING_FINAL_CHECK_FOR_REQUESTS() or RING_FINAL_CHECK_FOR_RESPONSES(). 283 * The second argument is a boolean return value. True indicates that there 284 * are pending messages on the ring (i.e., the connection should not be put 285 * to sleep). 286 * 287 * These macros will set the req_event/rsp_event field to trigger a 288 * notification on the very next message that is enqueued. If you want to 289 * create batches of work (i.e., only receive a notification after several 290 * messages have been enqueued) then you will need to create a customised 291 * version of the FINAL_CHECK macro in your own code, which sets the event 292 * field appropriately. 293 */ 294 295 #define RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(_r, _notify) do { \ 296 RING_IDX __old = (_r)->sring->req_prod; \ 297 RING_IDX __new = (_r)->req_prod_pvt; \ 298 xen_wmb(); /* back sees requests /before/ updated producer index */ \ 299 (_r)->sring->req_prod = __new; \ 300 xen_mb(); /* back sees new requests /before/ we check req_event */ \ 301 (_notify) = ((RING_IDX)(__new - (_r)->sring->req_event) < \ 302 (RING_IDX)(__new - __old)); \ 303 } while (0) 304 305 #define RING_PUSH_RESPONSES_AND_CHECK_NOTIFY(_r, _notify) do { \ 306 RING_IDX __old = (_r)->sring->rsp_prod; \ 307 RING_IDX __new = (_r)->rsp_prod_pvt; \ 308 xen_wmb(); /* front sees resps /before/ updated producer index */ \ 309 (_r)->sring->rsp_prod = __new; \ 310 xen_mb(); /* front sees new resps /before/ we check rsp_event */ \ 311 (_notify) = ((RING_IDX)(__new - (_r)->sring->rsp_event) < \ 312 (RING_IDX)(__new - __old)); \ 313 } while (0) 314 315 #define RING_FINAL_CHECK_FOR_REQUESTS(_r, _work_to_do) do { \ 316 (_work_to_do) = RING_HAS_UNCONSUMED_REQUESTS(_r); \ 317 if (_work_to_do) break; \ 318 (_r)->sring->req_event = (_r)->req_cons + 1; \ 319 xen_mb(); \ 320 (_work_to_do) = RING_HAS_UNCONSUMED_REQUESTS(_r); \ 321 } while (0) 322 323 #define RING_FINAL_CHECK_FOR_RESPONSES(_r, _work_to_do) do { \ 324 (_work_to_do) = RING_HAS_UNCONSUMED_RESPONSES(_r); \ 325 if (_work_to_do) break; \ 326 (_r)->sring->rsp_event = (_r)->rsp_cons + 1; \ 327 xen_mb(); \ 328 (_work_to_do) = RING_HAS_UNCONSUMED_RESPONSES(_r); \ 329 } while (0) 330 331 332 /* 333 * DEFINE_XEN_FLEX_RING_AND_INTF defines two monodirectional rings and 334 * functions to check if there is data on the ring, and to read and 335 * write to them. 336 * 337 * DEFINE_XEN_FLEX_RING is similar to DEFINE_XEN_FLEX_RING_AND_INTF, but 338 * does not define the indexes page. As different protocols can have 339 * extensions to the basic format, this macro allow them to define their 340 * own struct. 341 * 342 * XEN_FLEX_RING_SIZE 343 * Convenience macro to calculate the size of one of the two rings 344 * from the overall order. 345 * 346 * $NAME_mask 347 * Function to apply the size mask to an index, to reduce the index 348 * within the range [0-size]. 349 * 350 * $NAME_read_packet 351 * Function to read data from the ring. The amount of data to read is 352 * specified by the "size" argument. 353 * 354 * $NAME_write_packet 355 * Function to write data to the ring. The amount of data to write is 356 * specified by the "size" argument. 357 * 358 * $NAME_get_ring_ptr 359 * Convenience function that returns a pointer to read/write to the 360 * ring at the right location. 361 * 362 * $NAME_data_intf 363 * Indexes page, shared between frontend and backend. It also 364 * contains the array of grant refs. 365 * 366 * $NAME_queued 367 * Function to calculate how many bytes are currently on the ring, 368 * ready to be read. It can also be used to calculate how much free 369 * space is currently on the ring (XEN_FLEX_RING_SIZE() - 370 * $NAME_queued()). 371 */ 372 373 #ifndef XEN_PAGE_SHIFT 374 /* The PAGE_SIZE for ring protocols and hypercall interfaces is always 375 * 4K, regardless of the architecture, and page granularity chosen by 376 * operating systems. 377 */ 378 #define XEN_PAGE_SHIFT 12 379 #endif 380 #define XEN_FLEX_RING_SIZE(order) \ 381 (1UL << ((order) + XEN_PAGE_SHIFT - 1)) 382 383 #define DEFINE_XEN_FLEX_RING(name) \ 384 static inline RING_IDX name##_mask(RING_IDX idx, RING_IDX ring_size) \ 385 { \ 386 return idx & (ring_size - 1); \ 387 } \ 388 \ 389 static inline unsigned char *name##_get_ring_ptr(unsigned char *buf, \ 390 RING_IDX idx, \ 391 RING_IDX ring_size) \ 392 { \ 393 return buf + name##_mask(idx, ring_size); \ 394 } \ 395 \ 396 static inline void name##_read_packet(void *opaque, \ 397 const unsigned char *buf, \ 398 size_t size, \ 399 RING_IDX masked_prod, \ 400 RING_IDX *masked_cons, \ 401 RING_IDX ring_size) \ 402 { \ 403 if (*masked_cons < masked_prod || \ 404 size <= ring_size - *masked_cons) { \ 405 memcpy(opaque, buf + *masked_cons, size); \ 406 } else { \ 407 memcpy(opaque, buf + *masked_cons, ring_size - *masked_cons); \ 408 memcpy((unsigned char *)opaque + ring_size - *masked_cons, buf, \ 409 size - (ring_size - *masked_cons)); \ 410 } \ 411 *masked_cons = name##_mask(*masked_cons + size, ring_size); \ 412 } \ 413 \ 414 static inline void name##_write_packet(unsigned char *buf, \ 415 const void *opaque, \ 416 size_t size, \ 417 RING_IDX *masked_prod, \ 418 RING_IDX masked_cons, \ 419 RING_IDX ring_size) \ 420 { \ 421 if (*masked_prod < masked_cons || \ 422 size <= ring_size - *masked_prod) { \ 423 memcpy(buf + *masked_prod, opaque, size); \ 424 } else { \ 425 memcpy(buf + *masked_prod, opaque, ring_size - *masked_prod); \ 426 memcpy(buf, (unsigned char *)opaque + (ring_size - *masked_prod), \ 427 size - (ring_size - *masked_prod)); \ 428 } \ 429 *masked_prod = name##_mask(*masked_prod + size, ring_size); \ 430 } \ 431 \ 432 static inline RING_IDX name##_queued(RING_IDX prod, \ 433 RING_IDX cons, \ 434 RING_IDX ring_size) \ 435 { \ 436 RING_IDX size; \ 437 \ 438 if (prod == cons) \ 439 return 0; \ 440 \ 441 prod = name##_mask(prod, ring_size); \ 442 cons = name##_mask(cons, ring_size); \ 443 \ 444 if (prod == cons) \ 445 return ring_size; \ 446 \ 447 if (prod > cons) \ 448 size = prod - cons; \ 449 else \ 450 size = ring_size - (cons - prod); \ 451 return size; \ 452 } \ 453 \ 454 struct name##_data { \ 455 unsigned char *in; /* half of the allocation */ \ 456 unsigned char *out; /* half of the allocation */ \ 457 } 458 459 #define DEFINE_XEN_FLEX_RING_AND_INTF(name) \ 460 struct name##_data_intf { \ 461 RING_IDX in_cons, in_prod; \ 462 \ 463 uint8_t pad1[56]; \ 464 \ 465 RING_IDX out_cons, out_prod; \ 466 \ 467 uint8_t pad2[56]; \ 468 \ 469 RING_IDX ring_order; \ 470 grant_ref_t ref[]; \ 471 }; \ 472 DEFINE_XEN_FLEX_RING(name) 473 474 #endif /* __XEN_PUBLIC_IO_RING_H__ */ 475 476 /* 477 * Local variables: 478 * mode: C 479 * c-file-style: "BSD" 480 * c-basic-offset: 4 481 * tab-width: 4 482 * indent-tabs-mode: nil 483 * End: 484 */ 485
Indexes created Sun Oct 12 09:09:55 GMT 2025