1 | /* $NetBSD: ring.h,v 1.3 2016/01/06 15:28:40 bouyer Exp $ */ |
2 | /****************************************************************************** |
3 | * ring.h |
4 | * |
5 | * Shared producer-consumer ring macros. |
6 | * |
7 | * Permission is hereby granted, free of charge, to any person obtaining a copy |
8 | * of this software and associated documentation files (the "Software"), to |
9 | * deal in the Software without restriction, including without limitation the |
10 | * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or |
11 | * sell copies of the Software, and to permit persons to whom the Software is |
12 | * furnished to do so, subject to the following conditions: |
13 | * |
14 | * The above copyright notice and this permission notice shall be included in |
15 | * all copies or substantial portions of the Software. |
16 | * |
17 | * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR |
18 | * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, |
19 | * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE |
20 | * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER |
21 | * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING |
22 | * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER |
23 | * DEALINGS IN THE SOFTWARE. |
24 | * |
25 | * Tim Deegan and Andrew Warfield November 2004. |
26 | */ |
27 | |
28 | #ifndef __XEN_PUBLIC_IO_RING_H__ |
29 | #define __XEN_PUBLIC_IO_RING_H__ |
30 | |
31 | #include "../xen-compat.h" |
32 | |
33 | #if __XEN_INTERFACE_VERSION__ < 0x00030208 |
34 | #if defined(__Linux__) |
35 | #define xen_mb() mb() |
36 | #define xen_rmb() rmb() |
37 | #define xen_wmb() wmb() |
38 | #endif |
39 | #endif |
40 | |
41 | #if defined(__NetBSD__) |
42 | #define xen_mb() x86_mfence() |
43 | #define xen_rmb() x86_lfence() |
44 | #define xen_wmb() x86_sfence() |
45 | #endif |
46 | |
47 | typedef unsigned int RING_IDX; |
48 | |
49 | /* Round a 32-bit unsigned constant down to the nearest power of two. */ |
50 | #define __RD2(_x) (((_x) & 0x00000002) ? 0x2 : ((_x) & 0x1)) |
51 | #define __RD4(_x) (((_x) & 0x0000000c) ? __RD2((_x)>>2)<<2 : __RD2(_x)) |
52 | #define __RD8(_x) (((_x) & 0x000000f0) ? __RD4((_x)>>4)<<4 : __RD4(_x)) |
53 | #define __RD16(_x) (((_x) & 0x0000ff00) ? __RD8((_x)>>8)<<8 : __RD8(_x)) |
54 | #define __RD32(_x) (((_x) & 0xffff0000) ? __RD16((_x)>>16)<<16 : __RD16(_x)) |
55 | |
56 | /* |
57 | * Calculate size of a shared ring, given the total available space for the |
58 | * ring and indexes (_sz), and the name tag of the request/response structure. |
59 | * A ring contains as many entries as will fit, rounded down to the nearest |
60 | * power of two (so we can mask with (size-1) to loop around). |
61 | */ |
62 | #define __CONST_RING_SIZE(_s, _sz) \ |
63 | (__RD32(((_sz) - offsetof(struct _s##_sring, ring)) / \ |
64 | sizeof(((struct _s##_sring *)0)->ring[0]))) |
65 | /* |
66 | * The same for passing in an actual pointer instead of a name tag. |
67 | */ |
68 | #define __RING_SIZE(_s, _sz) \ |
69 | (__RD32(((_sz) - (long)(_s)->ring + (long)(_s)) / sizeof((_s)->ring[0]))) |
70 | |
71 | /* |
72 | * Macros to make the correct C datatypes for a new kind of ring. |
73 | * |
74 | * To make a new ring datatype, you need to have two message structures, |
75 | * let's say request_t, and response_t already defined. |
76 | * |
77 | * In a header where you want the ring datatype declared, you then do: |
78 | * |
79 | * DEFINE_RING_TYPES(mytag, request_t, response_t); |
80 | * |
81 | * These expand out to give you a set of types, as you can see below. |
82 | * The most important of these are: |
83 | * |
84 | * mytag_sring_t - The shared ring. |
85 | * mytag_front_ring_t - The 'front' half of the ring. |
86 | * mytag_back_ring_t - The 'back' half of the ring. |
87 | * |
88 | * To initialize a ring in your code you need to know the location and size |
89 | * of the shared memory area (PAGE_SIZE, for instance). To initialise |
90 | * the front half: |
91 | * |
92 | * mytag_front_ring_t front_ring; |
93 | * SHARED_RING_INIT((mytag_sring_t *)shared_page); |
94 | * FRONT_RING_INIT(&front_ring, (mytag_sring_t *)shared_page, PAGE_SIZE); |
95 | * |
96 | * Initializing the back follows similarly (note that only the front |
97 | * initializes the shared ring): |
98 | * |
99 | * mytag_back_ring_t back_ring; |
100 | * BACK_RING_INIT(&back_ring, (mytag_sring_t *)shared_page, PAGE_SIZE); |
101 | */ |
102 | |
103 | #define DEFINE_RING_TYPES(__name, __req_t, __rsp_t) \ |
104 | \ |
105 | /* Shared ring entry */ \ |
106 | union __name##_sring_entry { \ |
107 | __req_t req; \ |
108 | __rsp_t rsp; \ |
109 | }; \ |
110 | \ |
111 | /* Shared ring page */ \ |
112 | struct __name##_sring { \ |
113 | RING_IDX req_prod, req_event; \ |
114 | RING_IDX rsp_prod, rsp_event; \ |
115 | union { \ |
116 | struct { \ |
117 | uint8_t smartpoll_active; \ |
118 | } netif; \ |
119 | struct { \ |
120 | uint8_t msg; \ |
121 | } tapif_user; \ |
122 | uint8_t pvt_pad[4]; \ |
123 | } private; \ |
124 | uint8_t __pad[44]; \ |
125 | union __name##_sring_entry ring[1]; /* variable-length */ \ |
126 | }; \ |
127 | \ |
128 | /* "Front" end's private variables */ \ |
129 | struct __name##_front_ring { \ |
130 | RING_IDX req_prod_pvt; \ |
131 | RING_IDX rsp_cons; \ |
132 | unsigned int nr_ents; \ |
133 | struct __name##_sring *sring; \ |
134 | }; \ |
135 | \ |
136 | /* "Back" end's private variables */ \ |
137 | struct __name##_back_ring { \ |
138 | RING_IDX rsp_prod_pvt; \ |
139 | RING_IDX req_cons; \ |
140 | unsigned int nr_ents; \ |
141 | struct __name##_sring *sring; \ |
142 | }; \ |
143 | \ |
144 | /* Syntactic sugar */ \ |
145 | typedef struct __name##_sring __name##_sring_t; \ |
146 | typedef struct __name##_front_ring __name##_front_ring_t; \ |
147 | typedef struct __name##_back_ring __name##_back_ring_t |
148 | |
149 | /* |
150 | * Macros for manipulating rings. |
151 | * |
152 | * FRONT_RING_whatever works on the "front end" of a ring: here |
153 | * requests are pushed on to the ring and responses taken off it. |
154 | * |
155 | * BACK_RING_whatever works on the "back end" of a ring: here |
156 | * requests are taken off the ring and responses put on. |
157 | * |
158 | * N.B. these macros do NO INTERLOCKS OR FLOW CONTROL. |
159 | * This is OK in 1-for-1 request-response situations where the |
160 | * requestor (front end) never has more than RING_SIZE()-1 |
161 | * outstanding requests. |
162 | */ |
163 | |
164 | /* Initialising empty rings */ |
165 | #define SHARED_RING_INIT(_s) do { \ |
166 | (_s)->req_prod = (_s)->rsp_prod = 0; \ |
167 | (_s)->req_event = (_s)->rsp_event = 1; \ |
168 | (void)memset((_s)->private.pvt_pad, 0, sizeof((_s)->private.pvt_pad)); \ |
169 | (void)memset((_s)->__pad, 0, sizeof((_s)->__pad)); \ |
170 | } while(0) |
171 | |
172 | #define FRONT_RING_INIT(_r, _s, __size) do { \ |
173 | (_r)->req_prod_pvt = 0; \ |
174 | (_r)->rsp_cons = 0; \ |
175 | (_r)->nr_ents = __RING_SIZE(_s, __size); \ |
176 | (_r)->sring = (_s); \ |
177 | } while (0) |
178 | |
179 | #define BACK_RING_INIT(_r, _s, __size) do { \ |
180 | (_r)->rsp_prod_pvt = 0; \ |
181 | (_r)->req_cons = 0; \ |
182 | (_r)->nr_ents = __RING_SIZE(_s, __size); \ |
183 | (_r)->sring = (_s); \ |
184 | } while (0) |
185 | |
186 | /* Initialize to existing shared indexes -- for recovery */ |
187 | #define FRONT_RING_ATTACH(_r, _s, __size) do { \ |
188 | (_r)->sring = (_s); \ |
189 | (_r)->req_prod_pvt = (_s)->req_prod; \ |
190 | (_r)->rsp_cons = (_s)->rsp_prod; \ |
191 | (_r)->nr_ents = __RING_SIZE(_s, __size); \ |
192 | } while (0) |
193 | |
194 | #define BACK_RING_ATTACH(_r, _s, __size) do { \ |
195 | (_r)->sring = (_s); \ |
196 | (_r)->rsp_prod_pvt = (_s)->rsp_prod; \ |
197 | (_r)->req_cons = (_s)->req_prod; \ |
198 | (_r)->nr_ents = __RING_SIZE(_s, __size); \ |
199 | } while (0) |
200 | |
201 | /* How big is this ring? */ |
202 | #define RING_SIZE(_r) \ |
203 | ((_r)->nr_ents) |
204 | |
205 | /* Number of free requests (for use on front side only). */ |
206 | #define RING_FREE_REQUESTS(_r) \ |
207 | (RING_SIZE(_r) - ((_r)->req_prod_pvt - (_r)->rsp_cons)) |
208 | |
209 | /* Test if there is an empty slot available on the front ring. |
210 | * (This is only meaningful from the front. ) |
211 | */ |
212 | #define RING_FULL(_r) \ |
213 | (RING_FREE_REQUESTS(_r) == 0) |
214 | |
215 | /* Test if there are outstanding messages to be processed on a ring. */ |
216 | #define RING_HAS_UNCONSUMED_RESPONSES(_r) \ |
217 | ((_r)->sring->rsp_prod - (_r)->rsp_cons) |
218 | |
219 | #ifdef __GNUC__ |
220 | #define RING_HAS_UNCONSUMED_REQUESTS(_r) ({ \ |
221 | unsigned int req = (_r)->sring->req_prod - (_r)->req_cons; \ |
222 | unsigned int rsp = RING_SIZE(_r) - \ |
223 | ((_r)->req_cons - (_r)->rsp_prod_pvt); \ |
224 | req < rsp ? req : rsp; \ |
225 | }) |
226 | #else |
227 | /* Same as above, but without the nice GCC ({ ... }) syntax. */ |
228 | #define RING_HAS_UNCONSUMED_REQUESTS(_r) \ |
229 | ((((_r)->sring->req_prod - (_r)->req_cons) < \ |
230 | (RING_SIZE(_r) - ((_r)->req_cons - (_r)->rsp_prod_pvt))) ? \ |
231 | ((_r)->sring->req_prod - (_r)->req_cons) : \ |
232 | (RING_SIZE(_r) - ((_r)->req_cons - (_r)->rsp_prod_pvt))) |
233 | #endif |
234 | |
235 | /* Direct access to individual ring elements, by index. */ |
236 | #define RING_GET_REQUEST(_r, _idx) \ |
237 | (&((_r)->sring->ring[((_idx) & (RING_SIZE(_r) - 1))].req)) |
238 | |
239 | /* |
240 | * Get a local copy of a request. |
241 | * |
242 | * Use this in preference to RING_GET_REQUEST() so all processing is |
243 | * done on a local copy that cannot be modified by the other end. |
244 | * |
245 | * Note that https://gcc.gnu.org/bugzilla/show_bug.cgi?id=58145 may cause this |
246 | * to be ineffective where _req is a struct which consists of only bitfields. |
247 | */ |
248 | #define RING_COPY_REQUEST(_r, _idx, _req) do { \ |
249 | /* Use volatile to force the copy into _req. */ \ |
250 | *(_req) = *(volatile typeof(_req))RING_GET_REQUEST(_r, _idx); \ |
251 | } while (0) |
252 | |
253 | #define RING_GET_RESPONSE(_r, _idx) \ |
254 | (&((_r)->sring->ring[((_idx) & (RING_SIZE(_r) - 1))].rsp)) |
255 | |
256 | /* Loop termination condition: Would the specified index overflow the ring? */ |
257 | #define RING_REQUEST_CONS_OVERFLOW(_r, _cons) \ |
258 | (((_cons) - (_r)->rsp_prod_pvt) >= RING_SIZE(_r)) |
259 | |
260 | #define RING_PUSH_REQUESTS(_r) do { \ |
261 | xen_wmb(); /* back sees requests /before/ updated producer index */ \ |
262 | (_r)->sring->req_prod = (_r)->req_prod_pvt; \ |
263 | } while (0) |
264 | |
265 | #define RING_PUSH_RESPONSES(_r) do { \ |
266 | xen_wmb(); /* front sees resps /before/ updated producer index */ \ |
267 | (_r)->sring->rsp_prod = (_r)->rsp_prod_pvt; \ |
268 | } while (0) |
269 | |
270 | /* |
271 | * Notification hold-off (req_event and rsp_event): |
272 | * |
273 | * When queueing requests or responses on a shared ring, it may not always be |
274 | * necessary to notify the remote end. For example, if requests are in flight |
275 | * in a backend, the front may be able to queue further requests without |
276 | * notifying the back (if the back checks for new requests when it queues |
277 | * responses). |
278 | * |
279 | * When enqueuing requests or responses: |
280 | * |
281 | * Use RING_PUSH_{REQUESTS,RESPONSES}_AND_CHECK_NOTIFY(). The second argument |
282 | * is a boolean return value. True indicates that the receiver requires an |
283 | * asynchronous notification. |
284 | * |
285 | * After dequeuing requests or responses (before sleeping the connection): |
286 | * |
287 | * Use RING_FINAL_CHECK_FOR_REQUESTS() or RING_FINAL_CHECK_FOR_RESPONSES(). |
288 | * The second argument is a boolean return value. True indicates that there |
289 | * are pending messages on the ring (i.e., the connection should not be put |
290 | * to sleep). |
291 | * |
292 | * These macros will set the req_event/rsp_event field to trigger a |
293 | * notification on the very next message that is enqueued. If you want to |
294 | * create batches of work (i.e., only receive a notification after several |
295 | * messages have been enqueued) then you will need to create a customised |
296 | * version of the FINAL_CHECK macro in your own code, which sets the event |
297 | * field appropriately. |
298 | */ |
299 | |
300 | #define RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(_r, _notify) do { \ |
301 | RING_IDX __old = (_r)->sring->req_prod; \ |
302 | RING_IDX __new = (_r)->req_prod_pvt; \ |
303 | xen_wmb(); /* back sees requests /before/ updated producer index */ \ |
304 | (_r)->sring->req_prod = __new; \ |
305 | xen_mb(); /* back sees new requests /before/ we check req_event */ \ |
306 | (_notify) = ((RING_IDX)(__new - (_r)->sring->req_event) < \ |
307 | (RING_IDX)(__new - __old)); \ |
308 | } while (0) |
309 | |
310 | #define RING_PUSH_RESPONSES_AND_CHECK_NOTIFY(_r, _notify) do { \ |
311 | RING_IDX __old = (_r)->sring->rsp_prod; \ |
312 | RING_IDX __new = (_r)->rsp_prod_pvt; \ |
313 | xen_wmb(); /* front sees resps /before/ updated producer index */ \ |
314 | (_r)->sring->rsp_prod = __new; \ |
315 | xen_mb(); /* front sees new resps /before/ we check rsp_event */ \ |
316 | (_notify) = ((RING_IDX)(__new - (_r)->sring->rsp_event) < \ |
317 | (RING_IDX)(__new - __old)); \ |
318 | } while (0) |
319 | |
320 | #define RING_FINAL_CHECK_FOR_REQUESTS(_r, _work_to_do) do { \ |
321 | (_work_to_do) = RING_HAS_UNCONSUMED_REQUESTS(_r); \ |
322 | if (_work_to_do) break; \ |
323 | (_r)->sring->req_event = (_r)->req_cons + 1; \ |
324 | xen_mb(); \ |
325 | (_work_to_do) = RING_HAS_UNCONSUMED_REQUESTS(_r); \ |
326 | } while (0) |
327 | |
328 | #define RING_FINAL_CHECK_FOR_RESPONSES(_r, _work_to_do) do { \ |
329 | (_work_to_do) = RING_HAS_UNCONSUMED_RESPONSES(_r); \ |
330 | if (_work_to_do) break; \ |
331 | (_r)->sring->rsp_event = (_r)->rsp_cons + 1; \ |
332 | xen_mb(); \ |
333 | (_work_to_do) = RING_HAS_UNCONSUMED_RESPONSES(_r); \ |
334 | } while (0) |
335 | |
336 | #endif /* __XEN_PUBLIC_IO_RING_H__ */ |
337 | |
338 | /* |
339 | * Local variables: |
340 | * mode: C |
341 | * c-set-style: "BSD" |
342 | * c-basic-offset: 4 |
343 | * tab-width: 4 |
344 | * indent-tabs-mode: nil |
345 | * End: |
346 | */ |
347 | |