| blob | 025939278b83b5f9c7ef1527a417bb22283eed5c |
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 */
10 #ifndef __XEN_PUBLIC_IO_RING_H__
11 #define __XEN_PUBLIC_IO_RING_H__
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 */
30 #if __XEN_INTERFACE_VERSION__ < 0x00030208
31 #define xen_mb() mb()
32 #define xen_rmb() rmb()
33 #define xen_wmb() wmb()
34 #endif
38 /* Round a 32-bit unsigned constant down to the nearest power of two. */
39 #define __RD2(_x) (((_x) & 0x00000002) ? 0x2 : ((_x) & 0x1))
40 #define __RD4(_x) (((_x) & 0x0000000c) ? __RD2((_x)>>2)<<2 : __RD2(_x))
41 #define __RD8(_x) (((_x) & 0x000000f0) ? __RD4((_x)>>4)<<4 : __RD4(_x))
42 #define __RD16(_x) (((_x) & 0x0000ff00) ? __RD8((_x)>>8)<<8 : __RD8(_x))
43 #define __RD32(_x) (((_x) & 0xffff0000) ? __RD16((_x)>>16)<<16 : __RD16(_x))
45 /*
46 * Calculate size of a shared ring, given the total available space for the
47 * ring and indexes (_sz), and the name tag of the request/response structure.
48 * A ring contains as many entries as will fit, rounded down to the nearest
49 * power of two (so we can mask with (size-1) to loop around).
50 */
51 #define __CONST_RING_SIZE(_s, _sz) \
52 (__RD32(((_sz) - offsetof(struct _s##_sring, ring)) / \
53 sizeof(((struct _s##_sring *)0)->ring[0])))
54 /*
55 * The same for passing in an actual pointer instead of a name tag.
56 */
57 #define __RING_SIZE(_s, _sz) \
58 (__RD32(((_sz) - (long)(_s)->ring + (long)(_s)) / sizeof((_s)->ring[0])))
60 /*
61 * Macros to make the correct C datatypes for a new kind of ring.
62 *
63 * To make a new ring datatype, you need to have two message structures,
64 * let's say request_t, and response_t already defined.
65 *
66 * In a header where you want the ring datatype declared, you then do:
67 *
68 * DEFINE_RING_TYPES(mytag, request_t, response_t);
69 *
70 * These expand out to give you a set of types, as you can see below.
71 * The most important of these are:
72 *
73 * mytag_sring_t - The shared ring.
74 * mytag_front_ring_t - The 'front' half of the ring.
75 * mytag_back_ring_t - The 'back' half of the ring.
76 *
77 * To initialize a ring in your code you need to know the location and size
78 * of the shared memory area (PAGE_SIZE, for instance). To initialise
79 * the front half:
80 *
81 * mytag_front_ring_t ring;
82 * XEN_FRONT_RING_INIT(&ring, (mytag_sring_t *)shared_page, PAGE_SIZE);
83 *
84 * Initializing the back follows similarly (note that only the front
85 * initializes the shared ring):
86 *
87 * mytag_back_ring_t back_ring;
88 * BACK_RING_INIT(&back_ring, (mytag_sring_t *)shared_page, PAGE_SIZE);
89 */
91 #define DEFINE_RING_TYPES(__name, __req_t, __rsp_t) \
92 \
94 union __name##_sring_entry { \
95 __req_t req; \
96 __rsp_t rsp; \
97 }; \
98 \
100 struct __name##_sring { \
101 RING_IDX req_prod, req_event; \
102 RING_IDX rsp_prod, rsp_event; \
103 union { \
104 struct { \
105 uint8_t smartpoll_active; \
106 } netif; \
107 struct { \
108 uint8_t msg; \
109 } tapif_user; \
110 uint8_t pvt_pad[4]; \
111 } pvt; \
112 uint8_t __pad[44]; \
114 }; \
115 \
117 struct __name##_front_ring { \
118 RING_IDX req_prod_pvt; \
119 RING_IDX rsp_cons; \
120 unsigned int nr_ents; \
121 struct __name##_sring *sring; \
122 }; \
123 \
125 struct __name##_back_ring { \
126 RING_IDX rsp_prod_pvt; \
127 RING_IDX req_cons; \
128 unsigned int nr_ents; \
129 struct __name##_sring *sring; \
130 }; \
131 \
133 typedef struct __name##_sring __name##_sring_t; \
134 typedef struct __name##_front_ring __name##_front_ring_t; \
135 typedef struct __name##_back_ring __name##_back_ring_t
137 /*
138 * Macros for manipulating rings.
139 *
140 * FRONT_RING_whatever works on the "front end" of a ring: here
141 * requests are pushed on to the ring and responses taken off it.
142 *
143 * BACK_RING_whatever works on the "back end" of a ring: here
144 * requests are taken off the ring and responses put on.
145 *
146 * N.B. these macros do NO INTERLOCKS OR FLOW CONTROL.
147 * This is OK in 1-for-1 request-response situations where the
148 * requestor (front end) never has more than RING_SIZE()-1
149 * outstanding requests.
150 */
152 /* Initialising empty rings */
153 #define SHARED_RING_INIT(_s) do { \
154 (_s)->req_prod = (_s)->rsp_prod = 0; \
155 (_s)->req_event = (_s)->rsp_event = 1; \
156 (void)memset((_s)->pvt.pvt_pad, 0, sizeof((_s)->pvt.pvt_pad)); \
157 (void)memset((_s)->__pad, 0, sizeof((_s)->__pad)); \
158 } while(0)
160 #define FRONT_RING_ATTACH(_r, _s, _i, __size) do { \
161 (_r)->req_prod_pvt = (_i); \
162 (_r)->rsp_cons = (_i); \
163 (_r)->nr_ents = __RING_SIZE(_s, __size); \
164 (_r)->sring = (_s); \
165 } while (0)
167 #define FRONT_RING_INIT(_r, _s, __size) FRONT_RING_ATTACH(_r, _s, 0, __size)
169 #define XEN_FRONT_RING_INIT(r, s, size) do { \
170 SHARED_RING_INIT(s); \
171 FRONT_RING_INIT(r, s, size); \
172 } while (0)
174 #define BACK_RING_ATTACH(_r, _s, _i, __size) do { \
175 (_r)->rsp_prod_pvt = (_i); \
176 (_r)->req_cons = (_i); \
177 (_r)->nr_ents = __RING_SIZE(_s, __size); \
178 (_r)->sring = (_s); \
179 } while (0)
181 #define BACK_RING_INIT(_r, _s, __size) BACK_RING_ATTACH(_r, _s, 0, __size)
183 /* How big is this ring? */
184 #define RING_SIZE(_r) \
185 ((_r)->nr_ents)
187 /* Number of free requests (for use on front side only). */
188 #define RING_FREE_REQUESTS(_r) \
189 (RING_SIZE(_r) - ((_r)->req_prod_pvt - (_r)->rsp_cons))
191 /* Test if there is an empty slot available on the front ring.
192 * (This is only meaningful from the front. )
193 */
194 #define RING_FULL(_r) \
195 (RING_FREE_REQUESTS(_r) == 0)
197 /* Test if there are outstanding messages to be processed on a ring. */
198 #define XEN_RING_NR_UNCONSUMED_RESPONSES(_r) \
199 ((_r)->sring->rsp_prod - (_r)->rsp_cons)
201 #ifdef __GNUC__
202 #define XEN_RING_NR_UNCONSUMED_REQUESTS(_r) ({ \
203 unsigned int req = (_r)->sring->req_prod - (_r)->req_cons; \
204 unsigned int rsp = RING_SIZE(_r) - \
205 ((_r)->req_cons - (_r)->rsp_prod_pvt); \
206 req < rsp ? req : rsp; \
207 })
208 #else
209 /* Same as above, but without the nice GCC ({ ... }) syntax. */
210 #define XEN_RING_NR_UNCONSUMED_REQUESTS(_r) \
211 ((((_r)->sring->req_prod - (_r)->req_cons) < \
212 (RING_SIZE(_r) - ((_r)->req_cons - (_r)->rsp_prod_pvt))) ? \
213 ((_r)->sring->req_prod - (_r)->req_cons) : \
214 (RING_SIZE(_r) - ((_r)->req_cons - (_r)->rsp_prod_pvt)))
215 #endif
217 #ifdef XEN_RING_HAS_UNCONSUMED_IS_BOOL
218 /*
219 * These variants should only be used in case no caller is abusing them for
220 * obtaining the number of unconsumed responses/requests.
221 */
222 #define RING_HAS_UNCONSUMED_RESPONSES(_r) \
223 (!!XEN_RING_NR_UNCONSUMED_RESPONSES(_r))
224 #define RING_HAS_UNCONSUMED_REQUESTS(_r) \
225 (!!XEN_RING_NR_UNCONSUMED_REQUESTS(_r))
226 #else
227 #define RING_HAS_UNCONSUMED_RESPONSES(_r) XEN_RING_NR_UNCONSUMED_RESPONSES(_r)
228 #define RING_HAS_UNCONSUMED_REQUESTS(_r) XEN_RING_NR_UNCONSUMED_REQUESTS(_r)
229 #endif
231 /* Direct access to individual ring elements, by index. */
232 #define RING_GET_REQUEST(_r, _idx) \
233 (&((_r)->sring->ring[((_idx) & (RING_SIZE(_r) - 1))].req))
235 #define RING_GET_RESPONSE(_r, _idx) \
236 (&((_r)->sring->ring[((_idx) & (RING_SIZE(_r) - 1))].rsp))
238 /*
239 * Get a local copy of a request/response.
240 *
241 * Use this in preference to RING_GET_{REQUEST,RESPONSE}() so all processing is
242 * done on a local copy that cannot be modified by the other end.
243 *
244 * Note that https://gcc.gnu.org/bugzilla/show_bug.cgi?id=58145 may cause this
245 * to be ineffective where dest is a struct which consists of only bitfields.
246 */
247 #define RING_COPY_(type, r, idx, dest) do { \
249 *(dest) = *(volatile __typeof__(dest))RING_GET_##type(r, idx); \
250 } while (0)
252 #define RING_COPY_REQUEST(r, idx, req) RING_COPY_(REQUEST, r, idx, req)
253 #define RING_COPY_RESPONSE(r, idx, rsp) RING_COPY_(RESPONSE, r, idx, rsp)
255 /* Loop termination condition: Would the specified index overflow the ring? */
256 #define RING_REQUEST_CONS_OVERFLOW(_r, _cons) \
257 (((_cons) - (_r)->rsp_prod_pvt) >= RING_SIZE(_r))
259 /* Ill-behaved frontend determination: Can there be this many requests? */
260 #define RING_REQUEST_PROD_OVERFLOW(_r, _prod) \
261 (((_prod) - (_r)->rsp_prod_pvt) > RING_SIZE(_r))
263 /* Ill-behaved backend determination: Can there be this many responses? */
264 #define RING_RESPONSE_PROD_OVERFLOW(_r, _prod) \
265 (((_prod) - (_r)->rsp_cons) > RING_SIZE(_r))
267 #define RING_PUSH_REQUESTS(_r) do { \
269 (_r)->sring->req_prod = (_r)->req_prod_pvt; \
270 } while (0)
272 #define RING_PUSH_RESPONSES(_r) do { \
274 (_r)->sring->rsp_prod = (_r)->rsp_prod_pvt; \
275 } while (0)
277 /*
278 * Notification hold-off (req_event and rsp_event):
279 *
280 * When queueing requests or responses on a shared ring, it may not always be
281 * necessary to notify the remote end. For example, if requests are in flight
282 * in a backend, the front may be able to queue further requests without
283 * notifying the back (if the back checks for new requests when it queues
284 * responses).
285 *
286 * When enqueuing requests or responses:
287 *
288 * Use RING_PUSH_{REQUESTS,RESPONSES}_AND_CHECK_NOTIFY(). The second argument
289 * is a boolean return value. True indicates that the receiver requires an
290 * asynchronous notification.
291 *
292 * After dequeuing requests or responses (before sleeping the connection):
293 *
294 * Use RING_FINAL_CHECK_FOR_REQUESTS() or RING_FINAL_CHECK_FOR_RESPONSES().
295 * The second argument is a boolean return value. True indicates that there
296 * are pending messages on the ring (i.e., the connection should not be put
297 * to sleep).
298 *
299 * These macros will set the req_event/rsp_event field to trigger a
300 * notification on the very next message that is enqueued. If you want to
301 * create batches of work (i.e., only receive a notification after several
302 * messages have been enqueued) then you will need to create a customised
303 * version of the FINAL_CHECK macro in your own code, which sets the event
304 * field appropriately.
305 */
307 #define RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(_r, _notify) do { \
308 RING_IDX __old = (_r)->sring->req_prod; \
309 RING_IDX __new = (_r)->req_prod_pvt; \
311 (_r)->sring->req_prod = __new; \
313 (_notify) = ((RING_IDX)(__new - (_r)->sring->req_event) < \
314 (RING_IDX)(__new - __old)); \
315 } while (0)
317 #define RING_PUSH_RESPONSES_AND_CHECK_NOTIFY(_r, _notify) do { \
318 RING_IDX __old = (_r)->sring->rsp_prod; \
319 RING_IDX __new = (_r)->rsp_prod_pvt; \
321 (_r)->sring->rsp_prod = __new; \
323 (_notify) = ((RING_IDX)(__new - (_r)->sring->rsp_event) < \
324 (RING_IDX)(__new - __old)); \
325 } while (0)
327 #define RING_FINAL_CHECK_FOR_REQUESTS(_r, _work_to_do) do { \
328 (_work_to_do) = RING_HAS_UNCONSUMED_REQUESTS(_r); \
329 if (_work_to_do) break; \
330 (_r)->sring->req_event = (_r)->req_cons + 1; \
331 xen_mb(); \
332 (_work_to_do) = RING_HAS_UNCONSUMED_REQUESTS(_r); \
333 } while (0)
335 #define RING_FINAL_CHECK_FOR_RESPONSES(_r, _work_to_do) do { \
336 (_work_to_do) = RING_HAS_UNCONSUMED_RESPONSES(_r); \
337 if (_work_to_do) break; \
338 (_r)->sring->rsp_event = (_r)->rsp_cons + 1; \
339 xen_mb(); \
340 (_work_to_do) = RING_HAS_UNCONSUMED_RESPONSES(_r); \
341 } while (0)
344 /*
345 * DEFINE_XEN_FLEX_RING_AND_INTF defines two monodirectional rings and
346 * functions to check if there is data on the ring, and to read and
347 * write to them.
348 *
349 * DEFINE_XEN_FLEX_RING is similar to DEFINE_XEN_FLEX_RING_AND_INTF, but
350 * does not define the indexes page. As different protocols can have
351 * extensions to the basic format, this macro allow them to define their
352 * own struct.
353 *
354 * XEN_FLEX_RING_SIZE
355 * Convenience macro to calculate the size of one of the two rings
356 * from the overall order.
357 *
358 * $NAME_mask
359 * Function to apply the size mask to an index, to reduce the index
360 * within the range [0-size].
361 *
362 * $NAME_read_packet
363 * Function to read data from the ring. The amount of data to read is
364 * specified by the "size" argument.
365 *
366 * $NAME_write_packet
367 * Function to write data to the ring. The amount of data to write is
368 * specified by the "size" argument.
369 *
370 * $NAME_get_ring_ptr
371 * Convenience function that returns a pointer to read/write to the
372 * ring at the right location.
373 *
374 * $NAME_data_intf
375 * Indexes page, shared between frontend and backend. It also
376 * contains the array of grant refs.
377 *
378 * $NAME_queued
379 * Function to calculate how many bytes are currently on the ring,
380 * ready to be read. It can also be used to calculate how much free
381 * space is currently on the ring (XEN_FLEX_RING_SIZE() -
382 * $NAME_queued()).
383 */
385 #ifndef XEN_PAGE_SHIFT
386 /* The PAGE_SIZE for ring protocols and hypercall interfaces is always
387 * 4K, regardless of the architecture, and page granularity chosen by
388 * operating systems.
389 */
390 #define XEN_PAGE_SHIFT 12
391 #endif
392 #define XEN_FLEX_RING_SIZE(order) \
393 (1UL << ((order) + XEN_PAGE_SHIFT - 1))
395 #define DEFINE_XEN_FLEX_RING(name) \
396 static inline RING_IDX name##_mask(RING_IDX idx, RING_IDX ring_size) \
397 { \
398 return idx & (ring_size - 1); \
399 } \
400 \
401 static inline unsigned char *name##_get_ring_ptr(unsigned char *buf, \
402 RING_IDX idx, \
403 RING_IDX ring_size) \
404 { \
405 return buf + name##_mask(idx, ring_size); \
406 } \
407 \
408 static inline void name##_read_packet(void *opaque, \
409 const unsigned char *buf, \
410 size_t size, \
411 RING_IDX masked_prod, \
412 RING_IDX *masked_cons, \
413 RING_IDX ring_size) \
414 { \
415 if (*masked_cons < masked_prod || \
416 size <= ring_size - *masked_cons) { \
417 memcpy(opaque, buf + *masked_cons, size); \
418 } else { \
419 memcpy(opaque, buf + *masked_cons, ring_size - *masked_cons); \
420 memcpy((unsigned char *)opaque + ring_size - *masked_cons, buf, \
421 size - (ring_size - *masked_cons)); \
422 } \
423 *masked_cons = name##_mask(*masked_cons + size, ring_size); \
424 } \
425 \
426 static inline void name##_write_packet(unsigned char *buf, \
427 const void *opaque, \
428 size_t size, \
429 RING_IDX *masked_prod, \
430 RING_IDX masked_cons, \
431 RING_IDX ring_size) \
432 { \
433 if (*masked_prod < masked_cons || \
434 size <= ring_size - *masked_prod) { \
435 memcpy(buf + *masked_prod, opaque, size); \
436 } else { \
437 memcpy(buf + *masked_prod, opaque, ring_size - *masked_prod); \
438 memcpy(buf, (unsigned char *)opaque + (ring_size - *masked_prod), \
439 size - (ring_size - *masked_prod)); \
440 } \
441 *masked_prod = name##_mask(*masked_prod + size, ring_size); \
442 } \
443 \
444 static inline RING_IDX name##_queued(RING_IDX prod, \
445 RING_IDX cons, \
446 RING_IDX ring_size) \
447 { \
448 RING_IDX size; \
449 \
450 if (prod == cons) \
451 return 0; \
452 \
453 prod = name##_mask(prod, ring_size); \
454 cons = name##_mask(cons, ring_size); \
455 \
456 if (prod == cons) \
457 return ring_size; \
458 \
459 if (prod > cons) \
460 size = prod - cons; \
461 else \
462 size = ring_size - (cons - prod); \
463 return size; \
464 } \
465 \
466 struct name##_data { \
469 }
471 #define DEFINE_XEN_FLEX_RING_AND_INTF(name) \
472 struct name##_data_intf { \
473 RING_IDX in_cons, in_prod; \
474 \
475 uint8_t pad1[56]; \
476 \
477 RING_IDX out_cons, out_prod; \
478 \
479 uint8_t pad2[56]; \
480 \
481 RING_IDX ring_order; \
482 grant_ref_t ref[]; \
483 }; \
484 DEFINE_XEN_FLEX_RING(name)
488 /*
489 * Local variables:
490 * mode: C
491 * c-file-style: "BSD"
492 * c-basic-offset: 4
493 * tab-width: 4
494 * indent-tabs-mode: nil
495 * End:
496 */