| blob | 2af7a1cd665893d9ff509730c73e0e0852a6881a |
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 */
10 #ifndef __XEN_PUBLIC_IO_RING_H__
11 #define __XEN_PUBLIC_IO_RING_H__
13 #include <xen/interface/grant_table.h>
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))
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])))
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])))
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 */
74 #define DEFINE_RING_TYPES(__name, __req_t, __rsp_t) \
75 \
77 union __name##_sring_entry { \
78 __req_t req; \
79 __rsp_t rsp; \
80 }; \
81 \
83 struct __name##_sring { \
84 RING_IDX req_prod, req_event; \
85 RING_IDX rsp_prod, rsp_event; \
86 uint8_t pad[48]; \
88 }; \
89 \
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 \
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 };
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 */
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)
128 #define FRONT_RING_ATTACH(_r, _s, _i, __size) do { \
129 (_r)->req_prod_pvt = (_i); \
130 (_r)->rsp_cons = (_i); \
131 (_r)->nr_ents = __RING_SIZE(_s, __size); \
132 (_r)->sring = (_s); \
133 } while (0)
135 #define FRONT_RING_INIT(_r, _s, __size) FRONT_RING_ATTACH(_r, _s, 0, __size)
137 #define BACK_RING_ATTACH(_r, _s, _i, __size) do { \
138 (_r)->rsp_prod_pvt = (_i); \
139 (_r)->req_cons = (_i); \
140 (_r)->nr_ents = __RING_SIZE(_s, __size); \
141 (_r)->sring = (_s); \
142 } while (0)
144 #define BACK_RING_INIT(_r, _s, __size) BACK_RING_ATTACH(_r, _s, 0, __size)
146 /* How big is this ring? */
147 #define RING_SIZE(_r) \
148 ((_r)->nr_ents)
150 /* Number of free requests (for use on front side only). */
151 #define RING_FREE_REQUESTS(_r) \
152 (RING_SIZE(_r) - ((_r)->req_prod_pvt - (_r)->rsp_cons))
154 /* Test if there is an empty slot available on the front ring.
155 * (This is only meaningful from the front. )
156 */
157 #define RING_FULL(_r) \
158 (RING_FREE_REQUESTS(_r) == 0)
160 /* Test if there are outstanding messages to be processed on a ring. */
161 #define RING_HAS_UNCONSUMED_RESPONSES(_r) \
162 ((_r)->sring->rsp_prod - (_r)->rsp_cons)
164 #define RING_HAS_UNCONSUMED_REQUESTS(_r) \
165 ({ \
166 unsigned int req = (_r)->sring->req_prod - (_r)->req_cons; \
167 unsigned int rsp = RING_SIZE(_r) - \
168 ((_r)->req_cons - (_r)->rsp_prod_pvt); \
169 req < rsp ? req : rsp; \
170 })
172 /* Direct access to individual ring elements, by index. */
173 #define RING_GET_REQUEST(_r, _idx) \
174 (&((_r)->sring->ring[((_idx) & (RING_SIZE(_r) - 1))].req))
176 /*
177 * Get a local copy of a request.
178 *
179 * Use this in preference to RING_GET_REQUEST() so all processing is
180 * done on a local copy that cannot be modified by the other end.
181 *
182 * Note that https://gcc.gnu.org/bugzilla/show_bug.cgi?id=58145 may cause this
183 * to be ineffective where _req is a struct which consists of only bitfields.
184 */
185 #define RING_COPY_REQUEST(_r, _idx, _req) do { \
187 *(_req) = *(volatile typeof(_req))RING_GET_REQUEST(_r, _idx); \
188 } while (0)
190 #define RING_GET_RESPONSE(_r, _idx) \
191 (&((_r)->sring->ring[((_idx) & (RING_SIZE(_r) - 1))].rsp))
193 /* Loop termination condition: Would the specified index overflow the ring? */
194 #define RING_REQUEST_CONS_OVERFLOW(_r, _cons) \
195 (((_cons) - (_r)->rsp_prod_pvt) >= RING_SIZE(_r))
197 /* Ill-behaved frontend determination: Can there be this many requests? */
198 #define RING_REQUEST_PROD_OVERFLOW(_r, _prod) \
199 (((_prod) - (_r)->rsp_prod_pvt) > RING_SIZE(_r))
202 #define RING_PUSH_REQUESTS(_r) do { \
204 (_r)->sring->req_prod = (_r)->req_prod_pvt; \
205 } while (0)
207 #define RING_PUSH_RESPONSES(_r) do { \
209 (_r)->sring->rsp_prod = (_r)->rsp_prod_pvt; \
210 } while (0)
212 /*
213 * Notification hold-off (req_event and rsp_event):
214 *
215 * When queueing requests or responses on a shared ring, it may not always be
216 * necessary to notify the remote end. For example, if requests are in flight
217 * in a backend, the front may be able to queue further requests without
218 * notifying the back (if the back checks for new requests when it queues
219 * responses).
220 *
221 * When enqueuing requests or responses:
222 *
223 * Use RING_PUSH_{REQUESTS,RESPONSES}_AND_CHECK_NOTIFY(). The second argument
224 * is a boolean return value. True indicates that the receiver requires an
225 * asynchronous notification.
226 *
227 * After dequeuing requests or responses (before sleeping the connection):
228 *
229 * Use RING_FINAL_CHECK_FOR_REQUESTS() or RING_FINAL_CHECK_FOR_RESPONSES().
230 * The second argument is a boolean return value. True indicates that there
231 * are pending messages on the ring (i.e., the connection should not be put
232 * to sleep).
233 *
234 * These macros will set the req_event/rsp_event field to trigger a
235 * notification on the very next message that is enqueued. If you want to
236 * create batches of work (i.e., only receive a notification after several
237 * messages have been enqueued) then you will need to create a customised
238 * version of the FINAL_CHECK macro in your own code, which sets the event
239 * field appropriately.
240 */
242 #define RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(_r, _notify) do { \
243 RING_IDX __old = (_r)->sring->req_prod; \
244 RING_IDX __new = (_r)->req_prod_pvt; \
246 (_r)->sring->req_prod = __new; \
248 (_notify) = ((RING_IDX)(__new - (_r)->sring->req_event) < \
249 (RING_IDX)(__new - __old)); \
250 } while (0)
252 #define RING_PUSH_RESPONSES_AND_CHECK_NOTIFY(_r, _notify) do { \
253 RING_IDX __old = (_r)->sring->rsp_prod; \
254 RING_IDX __new = (_r)->rsp_prod_pvt; \
256 (_r)->sring->rsp_prod = __new; \
258 (_notify) = ((RING_IDX)(__new - (_r)->sring->rsp_event) < \
259 (RING_IDX)(__new - __old)); \
260 } while (0)
262 #define RING_FINAL_CHECK_FOR_REQUESTS(_r, _work_to_do) do { \
263 (_work_to_do) = RING_HAS_UNCONSUMED_REQUESTS(_r); \
264 if (_work_to_do) break; \
265 (_r)->sring->req_event = (_r)->req_cons + 1; \
266 virt_mb(); \
267 (_work_to_do) = RING_HAS_UNCONSUMED_REQUESTS(_r); \
268 } while (0)
270 #define RING_FINAL_CHECK_FOR_RESPONSES(_r, _work_to_do) do { \
271 (_work_to_do) = RING_HAS_UNCONSUMED_RESPONSES(_r); \
272 if (_work_to_do) break; \
273 (_r)->sring->rsp_event = (_r)->rsp_cons + 1; \
274 virt_mb(); \
275 (_work_to_do) = RING_HAS_UNCONSUMED_RESPONSES(_r); \
276 } while (0)
279 /*
280 * DEFINE_XEN_FLEX_RING_AND_INTF defines two monodirectional rings and
281 * functions to check if there is data on the ring, and to read and
282 * write to them.
283 *
284 * DEFINE_XEN_FLEX_RING is similar to DEFINE_XEN_FLEX_RING_AND_INTF, but
285 * does not define the indexes page. As different protocols can have
286 * extensions to the basic format, this macro allow them to define their
287 * own struct.
288 *
289 * XEN_FLEX_RING_SIZE
290 * Convenience macro to calculate the size of one of the two rings
291 * from the overall order.
292 *
293 * $NAME_mask
294 * Function to apply the size mask to an index, to reduce the index
295 * within the range [0-size].
296 *
297 * $NAME_read_packet
298 * Function to read data from the ring. The amount of data to read is
299 * specified by the "size" argument.
300 *
301 * $NAME_write_packet
302 * Function to write data to the ring. The amount of data to write is
303 * specified by the "size" argument.
304 *
305 * $NAME_get_ring_ptr
306 * Convenience function that returns a pointer to read/write to the
307 * ring at the right location.
308 *
309 * $NAME_data_intf
310 * Indexes page, shared between frontend and backend. It also
311 * contains the array of grant refs.
312 *
313 * $NAME_queued
314 * Function to calculate how many bytes are currently on the ring,
315 * ready to be read. It can also be used to calculate how much free
316 * space is currently on the ring (XEN_FLEX_RING_SIZE() -
317 * $NAME_queued()).
318 */
320 #ifndef XEN_PAGE_SHIFT
321 /* The PAGE_SIZE for ring protocols and hypercall interfaces is always
322 * 4K, regardless of the architecture, and page granularity chosen by
323 * operating systems.
324 */
325 #define XEN_PAGE_SHIFT 12
326 #endif
327 #define XEN_FLEX_RING_SIZE(order) \
328 (1UL << ((order) + XEN_PAGE_SHIFT - 1))
330 #define DEFINE_XEN_FLEX_RING(name) \
331 static inline RING_IDX name##_mask(RING_IDX idx, RING_IDX ring_size) \
332 { \
333 return idx & (ring_size - 1); \
334 } \
335 \
336 static inline unsigned char *name##_get_ring_ptr(unsigned char *buf, \
337 RING_IDX idx, \
338 RING_IDX ring_size) \
339 { \
340 return buf + name##_mask(idx, ring_size); \
341 } \
342 \
343 static inline void name##_read_packet(void *opaque, \
344 const unsigned char *buf, \
345 size_t size, \
346 RING_IDX masked_prod, \
347 RING_IDX *masked_cons, \
348 RING_IDX ring_size) \
349 { \
350 if (*masked_cons < masked_prod || \
351 size <= ring_size - *masked_cons) { \
352 memcpy(opaque, buf + *masked_cons, size); \
353 } else { \
354 memcpy(opaque, buf + *masked_cons, ring_size - *masked_cons); \
355 memcpy((unsigned char *)opaque + ring_size - *masked_cons, buf, \
356 size - (ring_size - *masked_cons)); \
357 } \
358 *masked_cons = name##_mask(*masked_cons + size, ring_size); \
359 } \
360 \
361 static inline void name##_write_packet(unsigned char *buf, \
362 const void *opaque, \
363 size_t size, \
364 RING_IDX *masked_prod, \
365 RING_IDX masked_cons, \
366 RING_IDX ring_size) \
367 { \
368 if (*masked_prod < masked_cons || \
369 size <= ring_size - *masked_prod) { \
370 memcpy(buf + *masked_prod, opaque, size); \
371 } else { \
372 memcpy(buf + *masked_prod, opaque, ring_size - *masked_prod); \
373 memcpy(buf, (unsigned char *)opaque + (ring_size - *masked_prod), \
374 size - (ring_size - *masked_prod)); \
375 } \
376 *masked_prod = name##_mask(*masked_prod + size, ring_size); \
377 } \
378 \
379 static inline RING_IDX name##_queued(RING_IDX prod, \
380 RING_IDX cons, \
381 RING_IDX ring_size) \
382 { \
383 RING_IDX size; \
384 \
385 if (prod == cons) \
386 return 0; \
387 \
388 prod = name##_mask(prod, ring_size); \
389 cons = name##_mask(cons, ring_size); \
390 \
391 if (prod == cons) \
392 return ring_size; \
393 \
394 if (prod > cons) \
395 size = prod - cons; \
396 else \
397 size = ring_size - (cons - prod); \
398 return size; \
399 } \
400 \
401 struct name##_data { \
404 }
406 #define DEFINE_XEN_FLEX_RING_AND_INTF(name) \
407 struct name##_data_intf { \
408 RING_IDX in_cons, in_prod; \
409 \
410 uint8_t pad1[56]; \
411 \
412 RING_IDX out_cons, out_prod; \
413 \
414 uint8_t pad2[56]; \
415 \
416 RING_IDX ring_order; \
417 grant_ref_t ref[]; \
418 }; \
419 DEFINE_XEN_FLEX_RING(name)