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1/* SPDX-License-Identifier: MIT */2/******************************************************************************3 * ring.h4 *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 following15 * 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 to20 * provide the following, before invoking the FLEX macros:21 * - size_t22 * - memcpy23 * - grant_ref_t24 * 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 30typedef 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 the41 * 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 nearest43 * 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 size72 * of the shared memory area (PAGE_SIZE, for instance). To initialise73 * the front half:74 *75 * mytag_front_ring_t ring;76 * XEN_FRONT_RING_INIT(&ring, (mytag_sring_t *)shared_page, PAGE_SIZE);77 *78 * Initializing the back follows similarly (note that only the front79 * initializes the shared ring):80 *81 * mytag_back_ring_t back_ring;82 * BACK_RING_INIT(&back_ring, (mytag_sring_t *)shared_page, PAGE_SIZE);83 */84 85#define DEFINE_RING_TYPES(__name, __req_t, __rsp_t) \86 \87/* Shared ring entry */ \88union __name##_sring_entry { \89 __req_t req; \90 __rsp_t rsp; \91}; \92 \93/* Shared ring page */ \94struct __name##_sring { \95 RING_IDX req_prod, req_event; \96 RING_IDX rsp_prod, rsp_event; \97 uint8_t __pad[48]; \98 union __name##_sring_entry ring[]; \99}; \100 \101/* "Front" end's private variables */ \102struct __name##_front_ring { \103 RING_IDX req_prod_pvt; \104 RING_IDX rsp_cons; \105 unsigned int nr_ents; \106 struct __name##_sring *sring; \107}; \108 \109/* "Back" end's private variables */ \110struct __name##_back_ring { \111 RING_IDX rsp_prod_pvt; \112 RING_IDX req_cons; \113 unsigned int nr_ents; \114 struct __name##_sring *sring; \115}; \116 \117/*118 * Macros for manipulating rings.119 *120 * FRONT_RING_whatever works on the "front end" of a ring: here121 * requests are pushed on to the ring and responses taken off it.122 *123 * BACK_RING_whatever works on the "back end" of a ring: here124 * requests are taken off the ring and responses put on.125 *126 * N.B. these macros do NO INTERLOCKS OR FLOW CONTROL.127 * This is OK in 1-for-1 request-response situations where the128 * requestor (front end) never has more than RING_SIZE()-1129 * outstanding requests.130 */131 132/* Initialising empty rings */133#define SHARED_RING_INIT(_s) do { \134 (_s)->req_prod = (_s)->rsp_prod = 0; \135 (_s)->req_event = (_s)->rsp_event = 1; \136 (void)memset((_s)->__pad, 0, sizeof((_s)->__pad)); \137} while(0)138 139#define FRONT_RING_ATTACH(_r, _s, _i, __size) do { \140 (_r)->req_prod_pvt = (_i); \141 (_r)->rsp_cons = (_i); \142 (_r)->nr_ents = __RING_SIZE(_s, __size); \143 (_r)->sring = (_s); \144} while (0)145 146#define FRONT_RING_INIT(_r, _s, __size) FRONT_RING_ATTACH(_r, _s, 0, __size)147 148#define XEN_FRONT_RING_INIT(r, s, size) do { \149 SHARED_RING_INIT(s); \150 FRONT_RING_INIT(r, s, size); \151} while (0)152 153#define BACK_RING_ATTACH(_r, _s, _i, __size) do { \154 (_r)->rsp_prod_pvt = (_i); \155 (_r)->req_cons = (_i); \156 (_r)->nr_ents = __RING_SIZE(_s, __size); \157 (_r)->sring = (_s); \158} while (0)159 160#define BACK_RING_INIT(_r, _s, __size) BACK_RING_ATTACH(_r, _s, 0, __size)161 162/* How big is this ring? */163#define RING_SIZE(_r) \164 ((_r)->nr_ents)165 166/* Number of free requests (for use on front side only). */167#define RING_FREE_REQUESTS(_r) \168 (RING_SIZE(_r) - ((_r)->req_prod_pvt - (_r)->rsp_cons))169 170/* Test if there is an empty slot available on the front ring.171 * (This is only meaningful from the front. )172 */173#define RING_FULL(_r) \174 (RING_FREE_REQUESTS(_r) == 0)175 176/* Test if there are outstanding messages to be processed on a ring. */177#define XEN_RING_NR_UNCONSUMED_RESPONSES(_r) \178 ((_r)->sring->rsp_prod - (_r)->rsp_cons)179 180#define XEN_RING_NR_UNCONSUMED_REQUESTS(_r) ({ \181 unsigned int req = (_r)->sring->req_prod - (_r)->req_cons; \182 unsigned int rsp = RING_SIZE(_r) - \183 ((_r)->req_cons - (_r)->rsp_prod_pvt); \184 req < rsp ? req : rsp; \185})186 187#define RING_HAS_UNCONSUMED_RESPONSES(_r) \188 (!!XEN_RING_NR_UNCONSUMED_RESPONSES(_r))189#define RING_HAS_UNCONSUMED_REQUESTS(_r) \190 (!!XEN_RING_NR_UNCONSUMED_REQUESTS(_r))191 192/* Direct access to individual ring elements, by index. */193#define RING_GET_REQUEST(_r, _idx) \194 (&((_r)->sring->ring[((_idx) & (RING_SIZE(_r) - 1))].req))195 196#define RING_GET_RESPONSE(_r, _idx) \197 (&((_r)->sring->ring[((_idx) & (RING_SIZE(_r) - 1))].rsp))198 199/*200 * Get a local copy of a request/response.201 *202 * Use this in preference to RING_GET_{REQUEST,RESPONSE}() so all processing is203 * done on a local copy that cannot be modified by the other end.204 *205 * Note that https://gcc.gnu.org/bugzilla/show_bug.cgi?id=58145 may cause this206 * to be ineffective where dest is a struct which consists of only bitfields.207 */208#define RING_COPY_(type, r, idx, dest) do { \209 /* Use volatile to force the copy into dest. */ \210 *(dest) = *(volatile typeof(dest))RING_GET_##type(r, idx); \211} while (0)212 213#define RING_COPY_REQUEST(r, idx, req) RING_COPY_(REQUEST, r, idx, req)214#define RING_COPY_RESPONSE(r, idx, rsp) RING_COPY_(RESPONSE, r, idx, rsp)215 216/* Loop termination condition: Would the specified index overflow the ring? */217#define RING_REQUEST_CONS_OVERFLOW(_r, _cons) \218 (((_cons) - (_r)->rsp_prod_pvt) >= RING_SIZE(_r))219 220/* Ill-behaved frontend determination: Can there be this many requests? */221#define RING_REQUEST_PROD_OVERFLOW(_r, _prod) \222 (((_prod) - (_r)->rsp_prod_pvt) > RING_SIZE(_r))223 224/* Ill-behaved backend determination: Can there be this many responses? */225#define RING_RESPONSE_PROD_OVERFLOW(_r, _prod) \226 (((_prod) - (_r)->rsp_cons) > RING_SIZE(_r))227 228#define RING_PUSH_REQUESTS(_r) do { \229 virt_wmb(); /* back sees requests /before/ updated producer index */\230 (_r)->sring->req_prod = (_r)->req_prod_pvt; \231} while (0)232 233#define RING_PUSH_RESPONSES(_r) do { \234 virt_wmb(); /* front sees resps /before/ updated producer index */ \235 (_r)->sring->rsp_prod = (_r)->rsp_prod_pvt; \236} while (0)237 238/*239 * Notification hold-off (req_event and rsp_event):240 *241 * When queueing requests or responses on a shared ring, it may not always be242 * necessary to notify the remote end. For example, if requests are in flight243 * in a backend, the front may be able to queue further requests without244 * notifying the back (if the back checks for new requests when it queues245 * responses).246 *247 * When enqueuing requests or responses:248 *249 * Use RING_PUSH_{REQUESTS,RESPONSES}_AND_CHECK_NOTIFY(). The second argument250 * is a boolean return value. True indicates that the receiver requires an251 * asynchronous notification.252 *253 * After dequeuing requests or responses (before sleeping the connection):254 *255 * Use RING_FINAL_CHECK_FOR_REQUESTS() or RING_FINAL_CHECK_FOR_RESPONSES().256 * The second argument is a boolean return value. True indicates that there257 * are pending messages on the ring (i.e., the connection should not be put258 * to sleep).259 *260 * These macros will set the req_event/rsp_event field to trigger a261 * notification on the very next message that is enqueued. If you want to262 * create batches of work (i.e., only receive a notification after several263 * messages have been enqueued) then you will need to create a customised264 * version of the FINAL_CHECK macro in your own code, which sets the event265 * field appropriately.266 */267 268#define RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(_r, _notify) do { \269 RING_IDX __old = (_r)->sring->req_prod; \270 RING_IDX __new = (_r)->req_prod_pvt; \271 virt_wmb(); /* back sees requests /before/ updated producer index */\272 (_r)->sring->req_prod = __new; \273 virt_mb(); /* back sees new requests /before/ we check req_event */ \274 (_notify) = ((RING_IDX)(__new - (_r)->sring->req_event) < \275 (RING_IDX)(__new - __old)); \276} while (0)277 278#define RING_PUSH_RESPONSES_AND_CHECK_NOTIFY(_r, _notify) do { \279 RING_IDX __old = (_r)->sring->rsp_prod; \280 RING_IDX __new = (_r)->rsp_prod_pvt; \281 virt_wmb(); /* front sees resps /before/ updated producer index */ \282 (_r)->sring->rsp_prod = __new; \283 virt_mb(); /* front sees new resps /before/ we check rsp_event */ \284 (_notify) = ((RING_IDX)(__new - (_r)->sring->rsp_event) < \285 (RING_IDX)(__new - __old)); \286} while (0)287 288#define RING_FINAL_CHECK_FOR_REQUESTS(_r, _work_to_do) do { \289 (_work_to_do) = RING_HAS_UNCONSUMED_REQUESTS(_r); \290 if (_work_to_do) break; \291 (_r)->sring->req_event = (_r)->req_cons + 1; \292 virt_mb(); \293 (_work_to_do) = RING_HAS_UNCONSUMED_REQUESTS(_r); \294} while (0)295 296#define RING_FINAL_CHECK_FOR_RESPONSES(_r, _work_to_do) do { \297 (_work_to_do) = RING_HAS_UNCONSUMED_RESPONSES(_r); \298 if (_work_to_do) break; \299 (_r)->sring->rsp_event = (_r)->rsp_cons + 1; \300 virt_mb(); \301 (_work_to_do) = RING_HAS_UNCONSUMED_RESPONSES(_r); \302} while (0)303 304 305/*306 * DEFINE_XEN_FLEX_RING_AND_INTF defines two monodirectional rings and307 * functions to check if there is data on the ring, and to read and308 * write to them.309 *310 * DEFINE_XEN_FLEX_RING is similar to DEFINE_XEN_FLEX_RING_AND_INTF, but311 * does not define the indexes page. As different protocols can have312 * extensions to the basic format, this macro allow them to define their313 * own struct.314 *315 * XEN_FLEX_RING_SIZE316 * Convenience macro to calculate the size of one of the two rings317 * from the overall order.318 *319 * $NAME_mask320 * Function to apply the size mask to an index, to reduce the index321 * within the range [0-size].322 *323 * $NAME_read_packet324 * Function to read data from the ring. The amount of data to read is325 * specified by the "size" argument.326 *327 * $NAME_write_packet328 * Function to write data to the ring. The amount of data to write is329 * specified by the "size" argument.330 *331 * $NAME_get_ring_ptr332 * Convenience function that returns a pointer to read/write to the333 * ring at the right location.334 *335 * $NAME_data_intf336 * Indexes page, shared between frontend and backend. It also337 * contains the array of grant refs.338 *339 * $NAME_queued340 * Function to calculate how many bytes are currently on the ring,341 * ready to be read. It can also be used to calculate how much free342 * space is currently on the ring (XEN_FLEX_RING_SIZE() -343 * $NAME_queued()).344 */345 346#ifndef XEN_PAGE_SHIFT347/* The PAGE_SIZE for ring protocols and hypercall interfaces is always348 * 4K, regardless of the architecture, and page granularity chosen by349 * operating systems.350 */351#define XEN_PAGE_SHIFT 12352#endif353#define XEN_FLEX_RING_SIZE(order) \354 (1UL << ((order) + XEN_PAGE_SHIFT - 1))355 356#define DEFINE_XEN_FLEX_RING(name) \357static inline RING_IDX name##_mask(RING_IDX idx, RING_IDX ring_size) \358{ \359 return idx & (ring_size - 1); \360} \361 \362static inline unsigned char *name##_get_ring_ptr(unsigned char *buf, \363 RING_IDX idx, \364 RING_IDX ring_size) \365{ \366 return buf + name##_mask(idx, ring_size); \367} \368 \369static inline void name##_read_packet(void *opaque, \370 const unsigned char *buf, \371 size_t size, \372 RING_IDX masked_prod, \373 RING_IDX *masked_cons, \374 RING_IDX ring_size) \375{ \376 if (*masked_cons < masked_prod || \377 size <= ring_size - *masked_cons) { \378 memcpy(opaque, buf + *masked_cons, size); \379 } else { \380 memcpy(opaque, buf + *masked_cons, ring_size - *masked_cons); \381 memcpy((unsigned char *)opaque + ring_size - *masked_cons, buf, \382 size - (ring_size - *masked_cons)); \383 } \384 *masked_cons = name##_mask(*masked_cons + size, ring_size); \385} \386 \387static inline void name##_write_packet(unsigned char *buf, \388 const void *opaque, \389 size_t size, \390 RING_IDX *masked_prod, \391 RING_IDX masked_cons, \392 RING_IDX ring_size) \393{ \394 if (*masked_prod < masked_cons || \395 size <= ring_size - *masked_prod) { \396 memcpy(buf + *masked_prod, opaque, size); \397 } else { \398 memcpy(buf + *masked_prod, opaque, ring_size - *masked_prod); \399 memcpy(buf, (unsigned char *)opaque + (ring_size - *masked_prod), \400 size - (ring_size - *masked_prod)); \401 } \402 *masked_prod = name##_mask(*masked_prod + size, ring_size); \403} \404 \405static inline RING_IDX name##_queued(RING_IDX prod, \406 RING_IDX cons, \407 RING_IDX ring_size) \408{ \409 RING_IDX size; \410 \411 if (prod == cons) \412 return 0; \413 \414 prod = name##_mask(prod, ring_size); \415 cons = name##_mask(cons, ring_size); \416 \417 if (prod == cons) \418 return ring_size; \419 \420 if (prod > cons) \421 size = prod - cons; \422 else \423 size = ring_size - (cons - prod); \424 return size; \425} \426 \427struct name##_data { \428 unsigned char *in; /* half of the allocation */ \429 unsigned char *out; /* half of the allocation */ \430}431 432#define DEFINE_XEN_FLEX_RING_AND_INTF(name) \433struct name##_data_intf { \434 RING_IDX in_cons, in_prod; \435 \436 uint8_t pad1[56]; \437 \438 RING_IDX out_cons, out_prod; \439 \440 uint8_t pad2[56]; \441 \442 RING_IDX ring_order; \443 grant_ref_t ref[]; \444}; \445DEFINE_XEN_FLEX_RING(name)446 447#endif /* __XEN_PUBLIC_IO_RING_H__ */448