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