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 | */ |
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 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 | */ |
27 | |
28 | #include <xen/interface/grant_table.h> |
29 | |
30 | typedef 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 the |
41 | * 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 nearest |
43 | * 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 size |
72 | * of the shared memory area (PAGE_SIZE, for instance). To initialise |
73 | * 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 front |
79 | * 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 */ \ |
88 | union __name##_sring_entry { \ |
89 | __req_t req; \ |
90 | __rsp_t rsp; \ |
91 | }; \ |
92 | \ |
93 | /* Shared ring page */ \ |
94 | struct __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[1]; /* variable-length */ \ |
99 | }; \ |
100 | \ |
101 | /* "Front" end's private variables */ \ |
102 | struct __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 */ \ |
110 | struct __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: here |
121 | * 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: here |
124 | * 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 the |
128 | * requestor (front end) never has more than RING_SIZE()-1 |
129 | * 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 is |
203 | * 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 this |
206 | * 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 be |
242 | * necessary to notify the remote end. For example, if requests are in flight |
243 | * in a backend, the front may be able to queue further requests without |
244 | * notifying the back (if the back checks for new requests when it queues |
245 | * responses). |
246 | * |
247 | * When enqueuing requests or responses: |
248 | * |
249 | * Use RING_PUSH_{REQUESTS,RESPONSES}_AND_CHECK_NOTIFY(). The second argument |
250 | * is a boolean return value. True indicates that the receiver requires an |
251 | * 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 there |
257 | * are pending messages on the ring (i.e., the connection should not be put |
258 | * to sleep). |
259 | * |
260 | * These macros will set the req_event/rsp_event field to trigger a |
261 | * notification on the very next message that is enqueued. If you want to |
262 | * create batches of work (i.e., only receive a notification after several |
263 | * messages have been enqueued) then you will need to create a customised |
264 | * version of the FINAL_CHECK macro in your own code, which sets the event |
265 | * 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 and |
307 | * functions to check if there is data on the ring, and to read and |
308 | * write to them. |
309 | * |
310 | * DEFINE_XEN_FLEX_RING is similar to DEFINE_XEN_FLEX_RING_AND_INTF, but |
311 | * does not define the indexes page. As different protocols can have |
312 | * extensions to the basic format, this macro allow them to define their |
313 | * own struct. |
314 | * |
315 | * XEN_FLEX_RING_SIZE |
316 | * Convenience macro to calculate the size of one of the two rings |
317 | * from the overall order. |
318 | * |
319 | * $NAME_mask |
320 | * Function to apply the size mask to an index, to reduce the index |
321 | * within the range [0-size]. |
322 | * |
323 | * $NAME_read_packet |
324 | * Function to read data from the ring. The amount of data to read is |
325 | * specified by the "size" argument. |
326 | * |
327 | * $NAME_write_packet |
328 | * Function to write data to the ring. The amount of data to write is |
329 | * specified by the "size" argument. |
330 | * |
331 | * $NAME_get_ring_ptr |
332 | * Convenience function that returns a pointer to read/write to the |
333 | * ring at the right location. |
334 | * |
335 | * $NAME_data_intf |
336 | * Indexes page, shared between frontend and backend. It also |
337 | * contains the array of grant refs. |
338 | * |
339 | * $NAME_queued |
340 | * 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 free |
342 | * space is currently on the ring (XEN_FLEX_RING_SIZE() - |
343 | * $NAME_queued()). |
344 | */ |
345 | |
346 | #ifndef XEN_PAGE_SHIFT |
347 | /* The PAGE_SIZE for ring protocols and hypercall interfaces is always |
348 | * 4K, regardless of the architecture, and page granularity chosen by |
349 | * operating systems. |
350 | */ |
351 | #define XEN_PAGE_SHIFT 12 |
352 | #endif |
353 | #define XEN_FLEX_RING_SIZE(order) \ |
354 | (1UL << ((order) + XEN_PAGE_SHIFT - 1)) |
355 | |
356 | #define DEFINE_XEN_FLEX_RING(name) \ |
357 | static inline RING_IDX name##_mask(RING_IDX idx, RING_IDX ring_size) \ |
358 | { \ |
359 | return idx & (ring_size - 1); \ |
360 | } \ |
361 | \ |
362 | static 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 | \ |
369 | static 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 | \ |
387 | static 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 | \ |
405 | static 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 | \ |
427 | struct 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) \ |
433 | struct 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 | }; \ |
445 | DEFINE_XEN_FLEX_RING(name) |
446 | |
447 | #endif /* __XEN_PUBLIC_IO_RING_H__ */ |
448 | |