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