| blob | 115705f3f4361297f2bcf1093c6320417e7fd67a |
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 */
27 #ifndef __XEN_PUBLIC_IO_RING_H__
28 #define __XEN_PUBLIC_IO_RING_H__
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 * Before using the different macros, you need to provide the following
37 * macros:
38 * - xen_mb() a memory barrier
39 * - xen_rmb() a read memory barrier
40 * - xen_wmb() a write memory barrier
41 * Example of those can be found in xenctrl.h.
42 *
43 * In addition, if you intend to use the FLEX macros, you also need to
44 * provide the following, before invoking the FLEX macros:
45 * - size_t
46 * - memcpy
47 * - grant_ref_t
48 * These declarations are provided by string.h of the standard headers,
49 * and grant_table.h from the Xen public headers.
50 */
54 /* Round a 32-bit unsigned constant down to the nearest power of two. */
55 #define __RD2(_x) (((_x) & 0x00000002) ? 0x2 : ((_x) & 0x1))
56 #define __RD4(_x) (((_x) & 0x0000000c) ? __RD2((_x)>>2)<<2 : __RD2(_x))
57 #define __RD8(_x) (((_x) & 0x000000f0) ? __RD4((_x)>>4)<<4 : __RD4(_x))
58 #define __RD16(_x) (((_x) & 0x0000ff00) ? __RD8((_x)>>8)<<8 : __RD8(_x))
59 #define __RD32(_x) (((_x) & 0xffff0000) ? __RD16((_x)>>16)<<16 : __RD16(_x))
61 /*
62 * Calculate size of a shared ring, given the total available space for the
63 * ring and indexes (_sz), and the name tag of the request/response structure.
64 * A ring contains as many entries as will fit, rounded down to the nearest
65 * power of two (so we can mask with (size-1) to loop around).
66 */
67 #define __CONST_RING_SIZE(_s, _sz) \
68 (__RD32(((_sz) - offsetof(struct _s##_sring, ring)) / \
69 sizeof_field(struct _s##_sring, ring[0])))
70 /*
71 * The same for passing in an actual pointer instead of a name tag.
72 */
73 #define __RING_SIZE(_s, _sz) \
74 (__RD32(((_sz) - (long)(_s)->ring + (long)(_s)) / sizeof((_s)->ring[0])))
76 /*
77 * Macros to make the correct C datatypes for a new kind of ring.
78 *
79 * To make a new ring datatype, you need to have two message structures,
80 * let's say request_t, and response_t already defined.
81 *
82 * In a header where you want the ring datatype declared, you then do:
83 *
84 * DEFINE_RING_TYPES(mytag, request_t, response_t);
85 *
86 * These expand out to give you a set of types, as you can see below.
87 * The most important of these are:
88 *
89 * mytag_sring_t - The shared ring.
90 * mytag_front_ring_t - The 'front' half of the ring.
91 * mytag_back_ring_t - The 'back' half of the ring.
92 *
93 * To initialize a ring in your code you need to know the location and size
94 * of the shared memory area (PAGE_SIZE, for instance). To initialise
95 * the front half:
96 *
97 * mytag_front_ring_t front_ring;
98 * SHARED_RING_INIT((mytag_sring_t *)shared_page);
99 * FRONT_RING_INIT(&front_ring, (mytag_sring_t *)shared_page, PAGE_SIZE);
100 *
101 * Initializing the back follows similarly (note that only the front
102 * initializes the shared ring):
103 *
104 * mytag_back_ring_t back_ring;
105 * BACK_RING_INIT(&back_ring, (mytag_sring_t *)shared_page, PAGE_SIZE);
106 */
108 #define DEFINE_RING_TYPES(__name, __req_t, __rsp_t) \
109 \
111 union __name##_sring_entry { \
112 __req_t req; \
113 __rsp_t rsp; \
114 }; \
115 \
117 struct __name##_sring { \
118 RING_IDX req_prod, req_event; \
119 RING_IDX rsp_prod, rsp_event; \
120 union { \
121 struct { \
122 uint8_t smartpoll_active; \
123 } netif; \
124 struct { \
125 uint8_t msg; \
126 } tapif_user; \
127 uint8_t pvt_pad[4]; \
128 } pvt; \
129 uint8_t __pad[44]; \
131 }; \
132 \
134 struct __name##_front_ring { \
135 RING_IDX req_prod_pvt; \
136 RING_IDX rsp_cons; \
137 unsigned int nr_ents; \
138 struct __name##_sring *sring; \
139 }; \
140 \
142 struct __name##_back_ring { \
143 RING_IDX rsp_prod_pvt; \
144 RING_IDX req_cons; \
145 unsigned int nr_ents; \
146 struct __name##_sring *sring; \
147 }; \
148 \
150 typedef struct __name##_sring __name##_sring_t; \
151 typedef struct __name##_front_ring __name##_front_ring_t; \
152 typedef struct __name##_back_ring __name##_back_ring_t
154 /*
155 * Macros for manipulating rings.
156 *
157 * FRONT_RING_whatever works on the "front end" of a ring: here
158 * requests are pushed on to the ring and responses taken off it.
159 *
160 * BACK_RING_whatever works on the "back end" of a ring: here
161 * requests are taken off the ring and responses put on.
162 *
163 * N.B. these macros do NO INTERLOCKS OR FLOW CONTROL.
164 * This is OK in 1-for-1 request-response situations where the
165 * requestor (front end) never has more than RING_SIZE()-1
166 * outstanding requests.
167 */
169 /* Initialising empty rings */
170 #define SHARED_RING_INIT(_s) do { \
171 (_s)->req_prod = (_s)->rsp_prod = 0; \
172 (_s)->req_event = (_s)->rsp_event = 1; \
173 (void)memset((_s)->pvt.pvt_pad, 0, sizeof((_s)->pvt.pvt_pad)); \
174 (void)memset((_s)->__pad, 0, sizeof((_s)->__pad)); \
175 } while(0)
177 #define FRONT_RING_INIT(_r, _s, __size) do { \
178 (_r)->req_prod_pvt = 0; \
179 (_r)->rsp_cons = 0; \
180 (_r)->nr_ents = __RING_SIZE(_s, __size); \
181 (_r)->sring = (_s); \
182 } while (0)
184 #define BACK_RING_INIT(_r, _s, __size) do { \
185 (_r)->rsp_prod_pvt = 0; \
186 (_r)->req_cons = 0; \
187 (_r)->nr_ents = __RING_SIZE(_s, __size); \
188 (_r)->sring = (_s); \
189 } while (0)
191 /* How big is this ring? */
192 #define RING_SIZE(_r) \
193 ((_r)->nr_ents)
195 /* Number of free requests (for use on front side only). */
196 #define RING_FREE_REQUESTS(_r) \
197 (RING_SIZE(_r) - ((_r)->req_prod_pvt - (_r)->rsp_cons))
199 /* Test if there is an empty slot available on the front ring.
200 * (This is only meaningful from the front. )
201 */
202 #define RING_FULL(_r) \
203 (RING_FREE_REQUESTS(_r) == 0)
205 /* Test if there are outstanding messages to be processed on a ring. */
206 #define RING_HAS_UNCONSUMED_RESPONSES(_r) \
207 ((_r)->sring->rsp_prod - (_r)->rsp_cons)
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 })
216 /* Direct access to individual ring elements, by index. */
217 #define RING_GET_REQUEST(_r, _idx) \
218 (&((_r)->sring->ring[((_idx) & (RING_SIZE(_r) - 1))].req))
220 /*
221 * Get a local copy of a request.
222 *
223 * Use this in preference to RING_GET_REQUEST() so all processing is
224 * done on a local copy that cannot be modified by the other end.
225 *
226 * Note that https://gcc.gnu.org/bugzilla/show_bug.cgi?id=58145 may cause this
227 * to be ineffective where _req is a struct which consists of only bitfields.
228 */
229 #define RING_COPY_REQUEST(_r, _idx, _req) do { \
231 *(_req) = *(volatile typeof(_req))RING_GET_REQUEST(_r, _idx); \
232 } while (0)
234 #define RING_GET_RESPONSE(_r, _idx) \
235 (&((_r)->sring->ring[((_idx) & (RING_SIZE(_r) - 1))].rsp))
237 /* Loop termination condition: Would the specified index overflow the ring? */
238 #define RING_REQUEST_CONS_OVERFLOW(_r, _cons) \
239 (((_cons) - (_r)->rsp_prod_pvt) >= RING_SIZE(_r))
241 /* Ill-behaved frontend determination: Can there be this many requests? */
242 #define RING_REQUEST_PROD_OVERFLOW(_r, _prod) \
243 (((_prod) - (_r)->rsp_prod_pvt) > RING_SIZE(_r))
245 #define RING_PUSH_REQUESTS(_r) do { \
247 (_r)->sring->req_prod = (_r)->req_prod_pvt; \
248 } while (0)
250 #define RING_PUSH_RESPONSES(_r) do { \
252 (_r)->sring->rsp_prod = (_r)->rsp_prod_pvt; \
253 } while (0)
255 /*
256 * Notification hold-off (req_event and rsp_event):
257 *
258 * When queueing requests or responses on a shared ring, it may not always be
259 * necessary to notify the remote end. For example, if requests are in flight
260 * in a backend, the front may be able to queue further requests without
261 * notifying the back (if the back checks for new requests when it queues
262 * responses).
263 *
264 * When enqueuing requests or responses:
265 *
266 * Use RING_PUSH_{REQUESTS,RESPONSES}_AND_CHECK_NOTIFY(). The second argument
267 * is a boolean return value. True indicates that the receiver requires an
268 * asynchronous notification.
269 *
270 * After dequeuing requests or responses (before sleeping the connection):
271 *
272 * Use RING_FINAL_CHECK_FOR_REQUESTS() or RING_FINAL_CHECK_FOR_RESPONSES().
273 * The second argument is a boolean return value. True indicates that there
274 * are pending messages on the ring (i.e., the connection should not be put
275 * to sleep).
276 *
277 * These macros will set the req_event/rsp_event field to trigger a
278 * notification on the very next message that is enqueued. If you want to
279 * create batches of work (i.e., only receive a notification after several
280 * messages have been enqueued) then you will need to create a customised
281 * version of the FINAL_CHECK macro in your own code, which sets the event
282 * field appropriately.
283 */
285 #define RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(_r, _notify) do { \
286 RING_IDX __old = (_r)->sring->req_prod; \
287 RING_IDX __new = (_r)->req_prod_pvt; \
289 (_r)->sring->req_prod = __new; \
291 (_notify) = ((RING_IDX)(__new - (_r)->sring->req_event) < \
292 (RING_IDX)(__new - __old)); \
293 } while (0)
295 #define RING_PUSH_RESPONSES_AND_CHECK_NOTIFY(_r, _notify) do { \
296 RING_IDX __old = (_r)->sring->rsp_prod; \
297 RING_IDX __new = (_r)->rsp_prod_pvt; \
299 (_r)->sring->rsp_prod = __new; \
301 (_notify) = ((RING_IDX)(__new - (_r)->sring->rsp_event) < \
302 (RING_IDX)(__new - __old)); \
303 } while (0)
305 #define RING_FINAL_CHECK_FOR_REQUESTS(_r, _work_to_do) do { \
306 (_work_to_do) = RING_HAS_UNCONSUMED_REQUESTS(_r); \
307 if (_work_to_do) break; \
308 (_r)->sring->req_event = (_r)->req_cons + 1; \
309 xen_mb(); \
310 (_work_to_do) = RING_HAS_UNCONSUMED_REQUESTS(_r); \
311 } while (0)
313 #define RING_FINAL_CHECK_FOR_RESPONSES(_r, _work_to_do) do { \
314 (_work_to_do) = RING_HAS_UNCONSUMED_RESPONSES(_r); \
315 if (_work_to_do) break; \
316 (_r)->sring->rsp_event = (_r)->rsp_cons + 1; \
317 xen_mb(); \
318 (_work_to_do) = RING_HAS_UNCONSUMED_RESPONSES(_r); \
319 } while (0)
322 /*
323 * DEFINE_XEN_FLEX_RING_AND_INTF defines two monodirectional rings and
324 * functions to check if there is data on the ring, and to read and
325 * write to them.
326 *
327 * DEFINE_XEN_FLEX_RING is similar to DEFINE_XEN_FLEX_RING_AND_INTF, but
328 * does not define the indexes page. As different protocols can have
329 * extensions to the basic format, this macro allow them to define their
330 * own struct.
331 *
332 * XEN_FLEX_RING_SIZE
333 * Convenience macro to calculate the size of one of the two rings
334 * from the overall order.
335 *
336 * $NAME_mask
337 * Function to apply the size mask to an index, to reduce the index
338 * within the range [0-size].
339 *
340 * $NAME_read_packet
341 * Function to read data from the ring. The amount of data to read is
342 * specified by the "size" argument.
343 *
344 * $NAME_write_packet
345 * Function to write data to the ring. The amount of data to write is
346 * specified by the "size" argument.
347 *
348 * $NAME_get_ring_ptr
349 * Convenience function that returns a pointer to read/write to the
350 * ring at the right location.
351 *
352 * $NAME_data_intf
353 * Indexes page, shared between frontend and backend. It also
354 * contains the array of grant refs.
355 *
356 * $NAME_queued
357 * Function to calculate how many bytes are currently on the ring,
358 * ready to be read. It can also be used to calculate how much free
359 * space is currently on the ring (XEN_FLEX_RING_SIZE() -
360 * $NAME_queued()).
361 */
363 #ifndef XEN_PAGE_SHIFT
364 /* The PAGE_SIZE for ring protocols and hypercall interfaces is always
365 * 4K, regardless of the architecture, and page granularity chosen by
366 * operating systems.
367 */
368 #define XEN_PAGE_SHIFT 12
369 #endif
370 #define XEN_FLEX_RING_SIZE(order) \
371 (1UL << ((order) + XEN_PAGE_SHIFT - 1))
373 #define DEFINE_XEN_FLEX_RING(name) \
374 static inline RING_IDX name##_mask(RING_IDX idx, RING_IDX ring_size) \
375 { \
376 return idx & (ring_size - 1); \
377 } \
378 \
379 static inline unsigned char *name##_get_ring_ptr(unsigned char *buf, \
380 RING_IDX idx, \
381 RING_IDX ring_size) \
382 { \
383 return buf + name##_mask(idx, ring_size); \
384 } \
385 \
386 static inline void name##_read_packet(void *opaque, \
387 const unsigned char *buf, \
388 size_t size, \
389 RING_IDX masked_prod, \
390 RING_IDX *masked_cons, \
391 RING_IDX ring_size) \
392 { \
393 if (*masked_cons < masked_prod || \
394 size <= ring_size - *masked_cons) { \
395 memcpy(opaque, buf + *masked_cons, size); \
396 } else { \
397 memcpy(opaque, buf + *masked_cons, ring_size - *masked_cons); \
398 memcpy((unsigned char *)opaque + ring_size - *masked_cons, buf, \
399 size - (ring_size - *masked_cons)); \
400 } \
401 *masked_cons = name##_mask(*masked_cons + size, ring_size); \
402 } \
403 \
404 static inline void name##_write_packet(unsigned char *buf, \
405 const void *opaque, \
406 size_t size, \
407 RING_IDX *masked_prod, \
408 RING_IDX masked_cons, \
409 RING_IDX ring_size) \
410 { \
411 if (*masked_prod < masked_cons || \
412 size <= ring_size - *masked_prod) { \
413 memcpy(buf + *masked_prod, opaque, size); \
414 } else { \
415 memcpy(buf + *masked_prod, opaque, ring_size - *masked_prod); \
416 memcpy(buf, (unsigned char *)opaque + (ring_size - *masked_prod), \
417 size - (ring_size - *masked_prod)); \
418 } \
419 *masked_prod = name##_mask(*masked_prod + size, ring_size); \
420 } \
421 \
422 static inline RING_IDX name##_queued(RING_IDX prod, \
423 RING_IDX cons, \
424 RING_IDX ring_size) \
425 { \
426 RING_IDX size; \
427 \
428 if (prod == cons) \
429 return 0; \
430 \
431 prod = name##_mask(prod, ring_size); \
432 cons = name##_mask(cons, ring_size); \
433 \
434 if (prod == cons) \
435 return ring_size; \
436 \
437 if (prod > cons) \
438 size = prod - cons; \
439 else \
440 size = ring_size - (cons - prod); \
441 return size; \
442 } \
443 \
444 struct name##_data { \
447 }
449 #define DEFINE_XEN_FLEX_RING_AND_INTF(name) \
450 struct name##_data_intf { \
451 RING_IDX in_cons, in_prod; \
452 \
453 uint8_t pad1[56]; \
454 \
455 RING_IDX out_cons, out_prod; \
456 \
457 uint8_t pad2[56]; \
458 \
459 RING_IDX ring_order; \
460 grant_ref_t ref[]; \
461 }; \
462 DEFINE_XEN_FLEX_RING(name)
466 /*
467 * Local variables:
468 * mode: C
469 * c-file-style: "BSD"
470 * c-basic-offset: 4
471 * tab-width: 4
472 * indent-tabs-mode: nil
473 * End:
474 */