[ipoib] Avoid unnecessary path record lookup for broadcast address
[ipxe.git] / src / include / xen / io / ring.h
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 */
26
27 #ifndef __XEN_PUBLIC_IO_RING_H__
28 #define __XEN_PUBLIC_IO_RING_H__
29
30 FILE_LICENCE ( MIT );
31
32 #include "../xen-compat.h"
33
34 #if __XEN_INTERFACE_VERSION__ < 0x00030208
35 #define xen_mb() mb()
36 #define xen_rmb() rmb()
37 #define xen_wmb() wmb()
38 #endif
39
40 typedef unsigned int RING_IDX;
41
42 /* Round a 32-bit unsigned constant down to the nearest power of two. */
43 #define __RD2(_x) (((_x) & 0x00000002) ? 0x2 : ((_x) & 0x1))
44 #define __RD4(_x) (((_x) & 0x0000000c) ? __RD2((_x)>>2)<<2 : __RD2(_x))
45 #define __RD8(_x) (((_x) & 0x000000f0) ? __RD4((_x)>>4)<<4 : __RD4(_x))
46 #define __RD16(_x) (((_x) & 0x0000ff00) ? __RD8((_x)>>8)<<8 : __RD8(_x))
47 #define __RD32(_x) (((_x) & 0xffff0000) ? __RD16((_x)>>16)<<16 : __RD16(_x))
48
49 /*
50 * Calculate size of a shared ring, given the total available space for the
51 * ring and indexes (_sz), and the name tag of the request/response structure.
52 * A ring contains as many entries as will fit, rounded down to the nearest
53 * power of two (so we can mask with (size-1) to loop around).
54 */
55 #define __CONST_RING_SIZE(_s, _sz) \
56 (__RD32(((_sz) - offsetof(struct _s##_sring, ring)) / \
57 sizeof(((struct _s##_sring *)0)->ring[0])))
58 /*
59 * The same for passing in an actual pointer instead of a name tag.
60 */
61 #define __RING_SIZE(_s, _sz) \
62 (__RD32(((_sz) - (long)(_s)->ring + (long)(_s)) / sizeof((_s)->ring[0])))
63
64 /*
65 * Macros to make the correct C datatypes for a new kind of ring.
66 *
67 * To make a new ring datatype, you need to have two message structures,
68 * let's say request_t, and response_t already defined.
69 *
70 * In a header where you want the ring datatype declared, you then do:
71 *
72 * DEFINE_RING_TYPES(mytag, request_t, response_t);
73 *
74 * These expand out to give you a set of types, as you can see below.
75 * The most important of these are:
76 *
77 * mytag_sring_t - The shared ring.
78 * mytag_front_ring_t - The 'front' half of the ring.
79 * mytag_back_ring_t - The 'back' half of the ring.
80 *
81 * To initialize a ring in your code you need to know the location and size
82 * of the shared memory area (PAGE_SIZE, for instance). To initialise
83 * the front half:
84 *
85 * mytag_front_ring_t front_ring;
86 * SHARED_RING_INIT((mytag_sring_t *)shared_page);
87 * FRONT_RING_INIT(&front_ring, (mytag_sring_t *)shared_page, PAGE_SIZE);
88 *
89 * Initializing the back follows similarly (note that only the front
90 * initializes the shared ring):
91 *
92 * mytag_back_ring_t back_ring;
93 * BACK_RING_INIT(&back_ring, (mytag_sring_t *)shared_page, PAGE_SIZE);
94 */
95
96 #define DEFINE_RING_TYPES(__name, __req_t, __rsp_t) \
97 \
98 /* Shared ring entry */ \
99 union __name##_sring_entry { \
100 __req_t req; \
101 __rsp_t rsp; \
102 }; \
103 \
104 /* Shared ring page */ \
105 struct __name##_sring { \
106 RING_IDX req_prod, req_event; \
107 RING_IDX rsp_prod, rsp_event; \
108 union { \
109 struct { \
110 uint8_t smartpoll_active; \
111 } netif; \
112 struct { \
113 uint8_t msg; \
114 } tapif_user; \
115 uint8_t pvt_pad[4]; \
116 } private; \
117 uint8_t __pad[44]; \
118 union __name##_sring_entry ring[1]; /* variable-length */ \
119 }; \
120 \
121 /* "Front" end's private variables */ \
122 struct __name##_front_ring { \
123 RING_IDX req_prod_pvt; \
124 RING_IDX rsp_cons; \
125 unsigned int nr_ents; \
126 struct __name##_sring *sring; \
127 }; \
128 \
129 /* "Back" end's private variables */ \
130 struct __name##_back_ring { \
131 RING_IDX rsp_prod_pvt; \
132 RING_IDX req_cons; \
133 unsigned int nr_ents; \
134 struct __name##_sring *sring; \
135 }; \
136 \
137 /* Syntactic sugar */ \
138 typedef struct __name##_sring __name##_sring_t; \
139 typedef struct __name##_front_ring __name##_front_ring_t; \
140 typedef struct __name##_back_ring __name##_back_ring_t
141
142 /*
143 * Macros for manipulating rings.
144 *
145 * FRONT_RING_whatever works on the "front end" of a ring: here
146 * requests are pushed on to the ring and responses taken off it.
147 *
148 * BACK_RING_whatever works on the "back end" of a ring: here
149 * requests are taken off the ring and responses put on.
150 *
151 * N.B. these macros do NO INTERLOCKS OR FLOW CONTROL.
152 * This is OK in 1-for-1 request-response situations where the
153 * requestor (front end) never has more than RING_SIZE()-1
154 * outstanding requests.
155 */
156
157 /* Initialising empty rings */
158 #define SHARED_RING_INIT(_s) do { \
159 (_s)->req_prod = (_s)->rsp_prod = 0; \
160 (_s)->req_event = (_s)->rsp_event = 1; \
161 (void)memset((_s)->private.pvt_pad, 0, sizeof((_s)->private.pvt_pad)); \
162 (void)memset((_s)->__pad, 0, sizeof((_s)->__pad)); \
163 } while(0)
164
165 #define FRONT_RING_INIT(_r, _s, __size) do { \
166 (_r)->req_prod_pvt = 0; \
167 (_r)->rsp_cons = 0; \
168 (_r)->nr_ents = __RING_SIZE(_s, __size); \
169 (_r)->sring = (_s); \
170 } while (0)
171
172 #define BACK_RING_INIT(_r, _s, __size) do { \
173 (_r)->rsp_prod_pvt = 0; \
174 (_r)->req_cons = 0; \
175 (_r)->nr_ents = __RING_SIZE(_s, __size); \
176 (_r)->sring = (_s); \
177 } while (0)
178
179 /* How big is this ring? */
180 #define RING_SIZE(_r) \
181 ((_r)->nr_ents)
182
183 /* Number of free requests (for use on front side only). */
184 #define RING_FREE_REQUESTS(_r) \
185 (RING_SIZE(_r) - ((_r)->req_prod_pvt - (_r)->rsp_cons))
186
187 /* Test if there is an empty slot available on the front ring.
188 * (This is only meaningful from the front. )
189 */
190 #define RING_FULL(_r) \
191 (RING_FREE_REQUESTS(_r) == 0)
192
193 /* Test if there are outstanding messages to be processed on a ring. */
194 #define RING_HAS_UNCONSUMED_RESPONSES(_r) \
195 ((_r)->sring->rsp_prod - (_r)->rsp_cons)
196
197 #ifdef __GNUC__
198 #define RING_HAS_UNCONSUMED_REQUESTS(_r) ({ \
199 unsigned int req = (_r)->sring->req_prod - (_r)->req_cons; \
200 unsigned int rsp = RING_SIZE(_r) - \
201 ((_r)->req_cons - (_r)->rsp_prod_pvt); \
202 req < rsp ? req : rsp; \
203 })
204 #else
205 /* Same as above, but without the nice GCC ({ ... }) syntax. */
206 #define RING_HAS_UNCONSUMED_REQUESTS(_r) \
207 ((((_r)->sring->req_prod - (_r)->req_cons) < \
208 (RING_SIZE(_r) - ((_r)->req_cons - (_r)->rsp_prod_pvt))) ? \
209 ((_r)->sring->req_prod - (_r)->req_cons) : \
210 (RING_SIZE(_r) - ((_r)->req_cons - (_r)->rsp_prod_pvt)))
211 #endif
212
213 /* Direct access to individual ring elements, by index. */
214 #define RING_GET_REQUEST(_r, _idx) \
215 (&((_r)->sring->ring[((_idx) & (RING_SIZE(_r) - 1))].req))
216
217 #define RING_GET_RESPONSE(_r, _idx) \
218 (&((_r)->sring->ring[((_idx) & (RING_SIZE(_r) - 1))].rsp))
219
220 /* Loop termination condition: Would the specified index overflow the ring? */
221 #define RING_REQUEST_CONS_OVERFLOW(_r, _cons) \
222 (((_cons) - (_r)->rsp_prod_pvt) >= RING_SIZE(_r))
223
224 /* Ill-behaved frontend determination: Can there be this many requests? */
225 #define RING_REQUEST_PROD_OVERFLOW(_r, _prod) \
226 (((_prod) - (_r)->rsp_prod_pvt) > RING_SIZE(_r))
227
228 #define RING_PUSH_REQUESTS(_r) do { \
229 xen_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 xen_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 xen_wmb(); /* back sees requests /before/ updated producer index */ \
272 (_r)->sring->req_prod = __new; \
273 xen_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 xen_wmb(); /* front sees resps /before/ updated producer index */ \
282 (_r)->sring->rsp_prod = __new; \
283 xen_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 xen_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 xen_mb(); \
301 (_work_to_do) = RING_HAS_UNCONSUMED_RESPONSES(_r); \
302 } while (0)
303
304 #endif /* __XEN_PUBLIC_IO_RING_H__ */
305
306 /*
307 * Local variables:
308 * mode: C
309 * c-file-style: "BSD"
310 * c-basic-offset: 4
311 * tab-width: 4
312 * indent-tabs-mode: nil
313 * End:
314 */