1 /* SPDX-License-Identifier: GPL-2.0 */ 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 #include <xen/interface/grant_table.h> 14 15 typedef unsigned int RING_IDX; 16 17 /* Round a 32-bit unsigned constant down to the nearest power of two. */ 18 #define __RD2(_x) (((_x) & 0x00000002) ? 0x2 : ((_x) & 0x1)) 19 #define __RD4(_x) (((_x) & 0x0000000c) ? __RD2((_x)>>2)<<2 : __RD2(_x)) 20 #define __RD8(_x) (((_x) & 0x000000f0) ? __RD4((_x)>>4)<<4 : __RD4(_x)) 21 #define __RD16(_x) (((_x) & 0x0000ff00) ? __RD8((_x)>>8)<<8 : __RD8(_x)) 22 #define __RD32(_x) (((_x) & 0xffff0000) ? __RD16((_x)>>16)<<16 : __RD16(_x)) 23 24 /* 25 * Calculate size of a shared ring, given the total available space for the 26 * ring and indexes (_sz), and the name tag of the request/response structure. 27 * A ring contains as many entries as will fit, rounded down to the nearest 28 * power of two (so we can mask with (size-1) to loop around). 29 */ 30 #define __CONST_RING_SIZE(_s, _sz) \ 31 (__RD32(((_sz) - offsetof(struct _s##_sring, ring)) / \ 32 sizeof(((struct _s##_sring *)0)->ring[0]))) 33 34 /* 35 * The same for passing in an actual pointer instead of a name tag. 36 */ 37 #define __RING_SIZE(_s, _sz) \ 38 (__RD32(((_sz) - (long)&(_s)->ring + (long)(_s)) / sizeof((_s)->ring[0]))) 39 40 /* 41 * Macros to make the correct C datatypes for a new kind of ring. 42 * 43 * To make a new ring datatype, you need to have two message structures, 44 * let's say struct request, and struct response already defined. 45 * 46 * In a header where you want the ring datatype declared, you then do: 47 * 48 * DEFINE_RING_TYPES(mytag, struct request, struct response); 49 * 50 * These expand out to give you a set of types, as you can see below. 51 * The most important of these are: 52 * 53 * struct mytag_sring - The shared ring. 54 * struct mytag_front_ring - The 'front' half of the ring. 55 * struct mytag_back_ring - The 'back' half of the ring. 56 * 57 * To initialize a ring in your code you need to know the location and size 58 * of the shared memory area (PAGE_SIZE, for instance). To initialise 59 * the front half: 60 * 61 * struct mytag_front_ring front_ring; 62 * SHARED_RING_INIT((struct mytag_sring *)shared_page); 63 * FRONT_RING_INIT(&front_ring, (struct mytag_sring *)shared_page, 64 * PAGE_SIZE); 65 * 66 * Initializing the back follows similarly (note that only the front 67 * initializes the shared ring): 68 * 69 * struct mytag_back_ring back_ring; 70 * BACK_RING_INIT(&back_ring, (struct mytag_sring *)shared_page, 71 * PAGE_SIZE); 72 */ 73 74 #define DEFINE_RING_TYPES(__name, __req_t, __rsp_t) \ 75 \ 76 /* Shared ring entry */ \ 77 union __name##_sring_entry { \ 78 __req_t req; \ 79 __rsp_t rsp; \ 80 }; \ 81 \ 82 /* Shared ring page */ \ 83 struct __name##_sring { \ 84 RING_IDX req_prod, req_event; \ 85 RING_IDX rsp_prod, rsp_event; \ 86 uint8_t pad[48]; \ 87 union __name##_sring_entry ring[1]; /* variable-length */ \ 88 }; \ 89 \ 90 /* "Front" end's private variables */ \ 91 struct __name##_front_ring { \ 92 RING_IDX req_prod_pvt; \ 93 RING_IDX rsp_cons; \ 94 unsigned int nr_ents; \ 95 struct __name##_sring *sring; \ 96 }; \ 97 \ 98 /* "Back" end's private variables */ \ 99 struct __name##_back_ring { \ 100 RING_IDX rsp_prod_pvt; \ 101 RING_IDX req_cons; \ 102 unsigned int nr_ents; \ 103 struct __name##_sring *sring; \ 104 }; 105 106 /* 107 * Macros for manipulating rings. 108 * 109 * FRONT_RING_whatever works on the "front end" of a ring: here 110 * requests are pushed on to the ring and responses taken off it. 111 * 112 * BACK_RING_whatever works on the "back end" of a ring: here 113 * requests are taken off the ring and responses put on. 114 * 115 * N.B. these macros do NO INTERLOCKS OR FLOW CONTROL. 116 * This is OK in 1-for-1 request-response situations where the 117 * requestor (front end) never has more than RING_SIZE()-1 118 * outstanding requests. 119 */ 120 121 /* Initialising empty rings */ 122 #define SHARED_RING_INIT(_s) do { \ 123 (_s)->req_prod = (_s)->rsp_prod = 0; \ 124 (_s)->req_event = (_s)->rsp_event = 1; \ 125 memset((_s)->pad, 0, sizeof((_s)->pad)); \ 126 } while(0) 127 128 #define FRONT_RING_INIT(_r, _s, __size) do { \ 129 (_r)->req_prod_pvt = 0; \ 130 (_r)->rsp_cons = 0; \ 131 (_r)->nr_ents = __RING_SIZE(_s, __size); \ 132 (_r)->sring = (_s); \ 133 } while (0) 134 135 #define BACK_RING_INIT(_r, _s, __size) do { \ 136 (_r)->rsp_prod_pvt = 0; \ 137 (_r)->req_cons = 0; \ 138 (_r)->nr_ents = __RING_SIZE(_s, __size); \ 139 (_r)->sring = (_s); \ 140 } while (0) 141 142 /* Initialize to existing shared indexes -- for recovery */ 143 #define FRONT_RING_ATTACH(_r, _s, __size) do { \ 144 (_r)->sring = (_s); \ 145 (_r)->req_prod_pvt = (_s)->req_prod; \ 146 (_r)->rsp_cons = (_s)->rsp_prod; \ 147 (_r)->nr_ents = __RING_SIZE(_s, __size); \ 148 } while (0) 149 150 #define BACK_RING_ATTACH(_r, _s, __size) do { \ 151 (_r)->sring = (_s); \ 152 (_r)->rsp_prod_pvt = (_s)->rsp_prod; \ 153 (_r)->req_cons = (_s)->req_prod; \ 154 (_r)->nr_ents = __RING_SIZE(_s, __size); \ 155 } while (0) 156 157 /* How big is this ring? */ 158 #define RING_SIZE(_r) \ 159 ((_r)->nr_ents) 160 161 /* Number of free requests (for use on front side only). */ 162 #define RING_FREE_REQUESTS(_r) \ 163 (RING_SIZE(_r) - ((_r)->req_prod_pvt - (_r)->rsp_cons)) 164 165 /* Test if there is an empty slot available on the front ring. 166 * (This is only meaningful from the front. ) 167 */ 168 #define RING_FULL(_r) \ 169 (RING_FREE_REQUESTS(_r) == 0) 170 171 /* Test if there are outstanding messages to be processed on a ring. */ 172 #define RING_HAS_UNCONSUMED_RESPONSES(_r) \ 173 ((_r)->sring->rsp_prod - (_r)->rsp_cons) 174 175 #define RING_HAS_UNCONSUMED_REQUESTS(_r) \ 176 ({ \ 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 /* 188 * Get a local copy of a request. 189 * 190 * Use this in preference to RING_GET_REQUEST() so all processing is 191 * done on a local copy that cannot be modified by the other end. 192 * 193 * Note that https://gcc.gnu.org/bugzilla/show_bug.cgi?id=58145 may cause this 194 * to be ineffective where _req is a struct which consists of only bitfields. 195 */ 196 #define RING_COPY_REQUEST(_r, _idx, _req) do { \ 197 /* Use volatile to force the copy into _req. */ \ 198 *(_req) = *(volatile typeof(_req))RING_GET_REQUEST(_r, _idx); \ 199 } while (0) 200 201 #define RING_GET_RESPONSE(_r, _idx) \ 202 (&((_r)->sring->ring[((_idx) & (RING_SIZE(_r) - 1))].rsp)) 203 204 /* Loop termination condition: Would the specified index overflow the ring? */ 205 #define RING_REQUEST_CONS_OVERFLOW(_r, _cons) \ 206 (((_cons) - (_r)->rsp_prod_pvt) >= RING_SIZE(_r)) 207 208 /* Ill-behaved frontend determination: Can there be this many requests? */ 209 #define RING_REQUEST_PROD_OVERFLOW(_r, _prod) \ 210 (((_prod) - (_r)->rsp_prod_pvt) > RING_SIZE(_r)) 211 212 213 #define RING_PUSH_REQUESTS(_r) do { \ 214 virt_wmb(); /* back sees requests /before/ updated producer index */ \ 215 (_r)->sring->req_prod = (_r)->req_prod_pvt; \ 216 } while (0) 217 218 #define RING_PUSH_RESPONSES(_r) do { \ 219 virt_wmb(); /* front sees responses /before/ updated producer index */ \ 220 (_r)->sring->rsp_prod = (_r)->rsp_prod_pvt; \ 221 } while (0) 222 223 /* 224 * Notification hold-off (req_event and rsp_event): 225 * 226 * When queueing requests or responses on a shared ring, it may not always be 227 * necessary to notify the remote end. For example, if requests are in flight 228 * in a backend, the front may be able to queue further requests without 229 * notifying the back (if the back checks for new requests when it queues 230 * responses). 231 * 232 * When enqueuing requests or responses: 233 * 234 * Use RING_PUSH_{REQUESTS,RESPONSES}_AND_CHECK_NOTIFY(). The second argument 235 * is a boolean return value. True indicates that the receiver requires an 236 * asynchronous notification. 237 * 238 * After dequeuing requests or responses (before sleeping the connection): 239 * 240 * Use RING_FINAL_CHECK_FOR_REQUESTS() or RING_FINAL_CHECK_FOR_RESPONSES(). 241 * The second argument is a boolean return value. True indicates that there 242 * are pending messages on the ring (i.e., the connection should not be put 243 * to sleep). 244 * 245 * These macros will set the req_event/rsp_event field to trigger a 246 * notification on the very next message that is enqueued. If you want to 247 * create batches of work (i.e., only receive a notification after several 248 * messages have been enqueued) then you will need to create a customised 249 * version of the FINAL_CHECK macro in your own code, which sets the event 250 * field appropriately. 251 */ 252 253 #define RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(_r, _notify) do { \ 254 RING_IDX __old = (_r)->sring->req_prod; \ 255 RING_IDX __new = (_r)->req_prod_pvt; \ 256 virt_wmb(); /* back sees requests /before/ updated producer index */ \ 257 (_r)->sring->req_prod = __new; \ 258 virt_mb(); /* back sees new requests /before/ we check req_event */ \ 259 (_notify) = ((RING_IDX)(__new - (_r)->sring->req_event) < \ 260 (RING_IDX)(__new - __old)); \ 261 } while (0) 262 263 #define RING_PUSH_RESPONSES_AND_CHECK_NOTIFY(_r, _notify) do { \ 264 RING_IDX __old = (_r)->sring->rsp_prod; \ 265 RING_IDX __new = (_r)->rsp_prod_pvt; \ 266 virt_wmb(); /* front sees responses /before/ updated producer index */ \ 267 (_r)->sring->rsp_prod = __new; \ 268 virt_mb(); /* front sees new responses /before/ we check rsp_event */ \ 269 (_notify) = ((RING_IDX)(__new - (_r)->sring->rsp_event) < \ 270 (RING_IDX)(__new - __old)); \ 271 } while (0) 272 273 #define RING_FINAL_CHECK_FOR_REQUESTS(_r, _work_to_do) do { \ 274 (_work_to_do) = RING_HAS_UNCONSUMED_REQUESTS(_r); \ 275 if (_work_to_do) break; \ 276 (_r)->sring->req_event = (_r)->req_cons + 1; \ 277 virt_mb(); \ 278 (_work_to_do) = RING_HAS_UNCONSUMED_REQUESTS(_r); \ 279 } while (0) 280 281 #define RING_FINAL_CHECK_FOR_RESPONSES(_r, _work_to_do) do { \ 282 (_work_to_do) = RING_HAS_UNCONSUMED_RESPONSES(_r); \ 283 if (_work_to_do) break; \ 284 (_r)->sring->rsp_event = (_r)->rsp_cons + 1; \ 285 virt_mb(); \ 286 (_work_to_do) = RING_HAS_UNCONSUMED_RESPONSES(_r); \ 287 } while (0) 288 289 290 /* 291 * DEFINE_XEN_FLEX_RING_AND_INTF defines two monodirectional rings and 292 * functions to check if there is data on the ring, and to read and 293 * write to them. 294 * 295 * DEFINE_XEN_FLEX_RING is similar to DEFINE_XEN_FLEX_RING_AND_INTF, but 296 * does not define the indexes page. As different protocols can have 297 * extensions to the basic format, this macro allow them to define their 298 * own struct. 299 * 300 * XEN_FLEX_RING_SIZE 301 * Convenience macro to calculate the size of one of the two rings 302 * from the overall order. 303 * 304 * $NAME_mask 305 * Function to apply the size mask to an index, to reduce the index 306 * within the range [0-size]. 307 * 308 * $NAME_read_packet 309 * Function to read data from the ring. The amount of data to read is 310 * specified by the "size" argument. 311 * 312 * $NAME_write_packet 313 * Function to write data to the ring. The amount of data to write is 314 * specified by the "size" argument. 315 * 316 * $NAME_get_ring_ptr 317 * Convenience function that returns a pointer to read/write to the 318 * ring at the right location. 319 * 320 * $NAME_data_intf 321 * Indexes page, shared between frontend and backend. It also 322 * contains the array of grant refs. 323 * 324 * $NAME_queued 325 * Function to calculate how many bytes are currently on the ring, 326 * ready to be read. It can also be used to calculate how much free 327 * space is currently on the ring (XEN_FLEX_RING_SIZE() - 328 * $NAME_queued()). 329 */ 330 331 #ifndef XEN_PAGE_SHIFT 332 /* The PAGE_SIZE for ring protocols and hypercall interfaces is always 333 * 4K, regardless of the architecture, and page granularity chosen by 334 * operating systems. 335 */ 336 #define XEN_PAGE_SHIFT 12 337 #endif 338 #define XEN_FLEX_RING_SIZE(order) \ 339 (1UL << ((order) + XEN_PAGE_SHIFT - 1)) 340 341 #define DEFINE_XEN_FLEX_RING(name) \ 342 static inline RING_IDX name##_mask(RING_IDX idx, RING_IDX ring_size) \ 343 { \ 344 return idx & (ring_size - 1); \ 345 } \ 346 \ 347 static inline unsigned char *name##_get_ring_ptr(unsigned char *buf, \ 348 RING_IDX idx, \ 349 RING_IDX ring_size) \ 350 { \ 351 return buf + name##_mask(idx, ring_size); \ 352 } \ 353 \ 354 static inline void name##_read_packet(void *opaque, \ 355 const unsigned char *buf, \ 356 size_t size, \ 357 RING_IDX masked_prod, \ 358 RING_IDX *masked_cons, \ 359 RING_IDX ring_size) \ 360 { \ 361 if (*masked_cons < masked_prod || \ 362 size <= ring_size - *masked_cons) { \ 363 memcpy(opaque, buf + *masked_cons, size); \ 364 } else { \ 365 memcpy(opaque, buf + *masked_cons, ring_size - *masked_cons); \ 366 memcpy((unsigned char *)opaque + ring_size - *masked_cons, buf, \ 367 size - (ring_size - *masked_cons)); \ 368 } \ 369 *masked_cons = name##_mask(*masked_cons + size, ring_size); \ 370 } \ 371 \ 372 static inline void name##_write_packet(unsigned char *buf, \ 373 const void *opaque, \ 374 size_t size, \ 375 RING_IDX *masked_prod, \ 376 RING_IDX masked_cons, \ 377 RING_IDX ring_size) \ 378 { \ 379 if (*masked_prod < masked_cons || \ 380 size <= ring_size - *masked_prod) { \ 381 memcpy(buf + *masked_prod, opaque, size); \ 382 } else { \ 383 memcpy(buf + *masked_prod, opaque, ring_size - *masked_prod); \ 384 memcpy(buf, (unsigned char *)opaque + (ring_size - *masked_prod), \ 385 size - (ring_size - *masked_prod)); \ 386 } \ 387 *masked_prod = name##_mask(*masked_prod + size, ring_size); \ 388 } \ 389 \ 390 static inline RING_IDX name##_queued(RING_IDX prod, \ 391 RING_IDX cons, \ 392 RING_IDX ring_size) \ 393 { \ 394 RING_IDX size; \ 395 \ 396 if (prod == cons) \ 397 return 0; \ 398 \ 399 prod = name##_mask(prod, ring_size); \ 400 cons = name##_mask(cons, ring_size); \ 401 \ 402 if (prod == cons) \ 403 return ring_size; \ 404 \ 405 if (prod > cons) \ 406 size = prod - cons; \ 407 else \ 408 size = ring_size - (cons - prod); \ 409 return size; \ 410 } \ 411 \ 412 struct name##_data { \ 413 unsigned char *in; /* half of the allocation */ \ 414 unsigned char *out; /* half of the allocation */ \ 415 } 416 417 #define DEFINE_XEN_FLEX_RING_AND_INTF(name) \ 418 struct name##_data_intf { \ 419 RING_IDX in_cons, in_prod; \ 420 \ 421 uint8_t pad1[56]; \ 422 \ 423 RING_IDX out_cons, out_prod; \ 424 \ 425 uint8_t pad2[56]; \ 426 \ 427 RING_IDX ring_order; \ 428 grant_ref_t ref[]; \ 429 }; \ 430 DEFINE_XEN_FLEX_RING(name) 431 432 #endif /* __XEN_PUBLIC_IO_RING_H__ */ 433