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1/******************************************************************************
2 * ring.h
3 *
4 * Shared producer-consumer ring macros.
5 *
6 * Tim Deegan and Andrew Warfield November 2004.
7 */
8
9#ifndef __XEN_PUBLIC_IO_RING_H__
10#define __XEN_PUBLIC_IO_RING_H__
11
12typedef unsigned int RING_IDX;
13
14/* Round a 32-bit unsigned constant down to the nearest power of two. */
15#define __RD2(_x) (((_x) & 0x00000002) ? 0x2 : ((_x) & 0x1))
16#define __RD4(_x) (((_x) & 0x0000000c) ? __RD2((_x)>>2)<<2 : __RD2(_x))
17#define __RD8(_x) (((_x) & 0x000000f0) ? __RD4((_x)>>4)<<4 : __RD4(_x))
18#define __RD16(_x) (((_x) & 0x0000ff00) ? __RD8((_x)>>8)<<8 : __RD8(_x))
19#define __RD32(_x) (((_x) & 0xffff0000) ? __RD16((_x)>>16)<<16 : __RD16(_x))
20
21/*
22 * Calculate size of a shared ring, given the total available space for the
23 * ring and indexes (_sz), and the name tag of the request/response structure.
24 * A ring contains as many entries as will fit, rounded down to the nearest
25 * power of two (so we can mask with (size-1) to loop around).
26 */
27#define __CONST_RING_SIZE(_s, _sz) \
28 (__RD32(((_sz) - offsetof(struct _s##_sring, ring)) / \
29 sizeof(((struct _s##_sring *)0)->ring[0])))
30
31/*
32 * The same for passing in an actual pointer instead of a name tag.
33 */
34#define __RING_SIZE(_s, _sz) \
35 (__RD32(((_sz) - (long)&(_s)->ring + (long)(_s)) / sizeof((_s)->ring[0])))
36
37/*
38 * Macros to make the correct C datatypes for a new kind of ring.
39 *
40 * To make a new ring datatype, you need to have two message structures,
41 * let's say struct request, and struct response already defined.
42 *
43 * In a header where you want the ring datatype declared, you then do:
44 *
45 * DEFINE_RING_TYPES(mytag, struct request, struct response);
46 *
47 * These expand out to give you a set of types, as you can see below.
48 * The most important of these are:
49 *
50 * struct mytag_sring - The shared ring.
51 * struct mytag_front_ring - The 'front' half of the ring.
52 * struct mytag_back_ring - The 'back' half of the ring.
53 *
54 * To initialize a ring in your code you need to know the location and size
55 * of the shared memory area (PAGE_SIZE, for instance). To initialise
56 * the front half:
57 *
58 * struct mytag_front_ring front_ring;
59 * SHARED_RING_INIT((struct mytag_sring *)shared_page);
60 * FRONT_RING_INIT(&front_ring, (struct mytag_sring *)shared_page,
61 * PAGE_SIZE);
62 *
63 * Initializing the back follows similarly (note that only the front
64 * initializes the shared ring):
65 *
66 * struct mytag_back_ring back_ring;
67 * BACK_RING_INIT(&back_ring, (struct mytag_sring *)shared_page,
68 * PAGE_SIZE);
69 */
70
71#define DEFINE_RING_TYPES(__name, __req_t, __rsp_t) \
72 \
73/* Shared ring entry */ \
74union __name##_sring_entry { \
75 __req_t req; \
76 __rsp_t rsp; \
77}; \
78 \
79/* Shared ring page */ \
80struct __name##_sring { \
81 RING_IDX req_prod, req_event; \
82 RING_IDX rsp_prod, rsp_event; \
83 uint8_t pad[48]; \
84 union __name##_sring_entry ring[1]; /* variable-length */ \
85}; \
86 \
87/* "Front" end's private variables */ \
88struct __name##_front_ring { \
89 RING_IDX req_prod_pvt; \
90 RING_IDX rsp_cons; \
91 unsigned int nr_ents; \
92 struct __name##_sring *sring; \
93}; \
94 \
95/* "Back" end's private variables */ \
96struct __name##_back_ring { \
97 RING_IDX rsp_prod_pvt; \
98 RING_IDX req_cons; \
99 unsigned int nr_ents; \
100 struct __name##_sring *sring; \
101};
102
103/*
104 * Macros for manipulating rings.
105 *
106 * FRONT_RING_whatever works on the "front end" of a ring: here
107 * requests are pushed on to the ring and responses taken off it.
108 *
109 * BACK_RING_whatever works on the "back end" of a ring: here
110 * requests are taken off the ring and responses put on.
111 *
112 * N.B. these macros do NO INTERLOCKS OR FLOW CONTROL.
113 * This is OK in 1-for-1 request-response situations where the
114 * requestor (front end) never has more than RING_SIZE()-1
115 * outstanding requests.
116 */
117
118/* Initialising empty rings */
119#define SHARED_RING_INIT(_s) do { \
120 (_s)->req_prod = (_s)->rsp_prod = 0; \
121 (_s)->req_event = (_s)->rsp_event = 1; \
122 memset((_s)->pad, 0, sizeof((_s)->pad)); \
123} while(0)
124
125#define FRONT_RING_INIT(_r, _s, __size) do { \
126 (_r)->req_prod_pvt = 0; \
127 (_r)->rsp_cons = 0; \
128 (_r)->nr_ents = __RING_SIZE(_s, __size); \
129 (_r)->sring = (_s); \
130} while (0)
131
132#define BACK_RING_INIT(_r, _s, __size) do { \
133 (_r)->rsp_prod_pvt = 0; \
134 (_r)->req_cons = 0; \
135 (_r)->nr_ents = __RING_SIZE(_s, __size); \
136 (_r)->sring = (_s); \
137} while (0)
138
139/* Initialize to existing shared indexes -- for recovery */
140#define FRONT_RING_ATTACH(_r, _s, __size) do { \
141 (_r)->sring = (_s); \
142 (_r)->req_prod_pvt = (_s)->req_prod; \
143 (_r)->rsp_cons = (_s)->rsp_prod; \
144 (_r)->nr_ents = __RING_SIZE(_s, __size); \
145} while (0)
146
147#define BACK_RING_ATTACH(_r, _s, __size) do { \
148 (_r)->sring = (_s); \
149 (_r)->rsp_prod_pvt = (_s)->rsp_prod; \
150 (_r)->req_cons = (_s)->req_prod; \
151 (_r)->nr_ents = __RING_SIZE(_s, __size); \
152} while (0)
153
154/* How big is this ring? */
155#define RING_SIZE(_r) \
156 ((_r)->nr_ents)
157
158/* Number of free requests (for use on front side only). */
159#define RING_FREE_REQUESTS(_r) \
160 (RING_SIZE(_r) - ((_r)->req_prod_pvt - (_r)->rsp_cons))
161
162/* Test if there is an empty slot available on the front ring.
163 * (This is only meaningful from the front. )
164 */
165#define RING_FULL(_r) \
166 (RING_FREE_REQUESTS(_r) == 0)
167
168/* Test if there are outstanding messages to be processed on a ring. */
169#define RING_HAS_UNCONSUMED_RESPONSES(_r) \
170 ((_r)->sring->rsp_prod - (_r)->rsp_cons)
171
172#define RING_HAS_UNCONSUMED_REQUESTS(_r) \
173 ({ \
174 unsigned int req = (_r)->sring->req_prod - (_r)->req_cons; \
175 unsigned int rsp = RING_SIZE(_r) - \
176 ((_r)->req_cons - (_r)->rsp_prod_pvt); \
177 req < rsp ? req : rsp; \
178 })
179
180/* Direct access to individual ring elements, by index. */
181#define RING_GET_REQUEST(_r, _idx) \
182 (&((_r)->sring->ring[((_idx) & (RING_SIZE(_r) - 1))].req))
183
184#define RING_GET_RESPONSE(_r, _idx) \
185 (&((_r)->sring->ring[((_idx) & (RING_SIZE(_r) - 1))].rsp))
186
187/* Loop termination condition: Would the specified index overflow the ring? */
188#define RING_REQUEST_CONS_OVERFLOW(_r, _cons) \
189 (((_cons) - (_r)->rsp_prod_pvt) >= RING_SIZE(_r))
190
191#define RING_PUSH_REQUESTS(_r) do { \
192 wmb(); /* back sees requests /before/ updated producer index */ \
193 (_r)->sring->req_prod = (_r)->req_prod_pvt; \
194} while (0)
195
196#define RING_PUSH_RESPONSES(_r) do { \
197 wmb(); /* front sees responses /before/ updated producer index */ \
198 (_r)->sring->rsp_prod = (_r)->rsp_prod_pvt; \
199} while (0)
200
201/*
202 * Notification hold-off (req_event and rsp_event):
203 *
204 * When queueing requests or responses on a shared ring, it may not always be
205 * necessary to notify the remote end. For example, if requests are in flight
206 * in a backend, the front may be able to queue further requests without
207 * notifying the back (if the back checks for new requests when it queues
208 * responses).
209 *
210 * When enqueuing requests or responses:
211 *
212 * Use RING_PUSH_{REQUESTS,RESPONSES}_AND_CHECK_NOTIFY(). The second argument
213 * is a boolean return value. True indicates that the receiver requires an
214 * asynchronous notification.
215 *
216 * After dequeuing requests or responses (before sleeping the connection):
217 *
218 * Use RING_FINAL_CHECK_FOR_REQUESTS() or RING_FINAL_CHECK_FOR_RESPONSES().
219 * The second argument is a boolean return value. True indicates that there
220 * are pending messages on the ring (i.e., the connection should not be put
221 * to sleep).
222 *
223 * These macros will set the req_event/rsp_event field to trigger a
224 * notification on the very next message that is enqueued. If you want to
225 * create batches of work (i.e., only receive a notification after several
226 * messages have been enqueued) then you will need to create a customised
227 * version of the FINAL_CHECK macro in your own code, which sets the event
228 * field appropriately.
229 */
230
231#define RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(_r, _notify) do { \
232 RING_IDX __old = (_r)->sring->req_prod; \
233 RING_IDX __new = (_r)->req_prod_pvt; \
234 wmb(); /* back sees requests /before/ updated producer index */ \
235 (_r)->sring->req_prod = __new; \
236 mb(); /* back sees new requests /before/ we check req_event */ \
237 (_notify) = ((RING_IDX)(__new - (_r)->sring->req_event) < \
238 (RING_IDX)(__new - __old)); \
239} while (0)
240
241#define RING_PUSH_RESPONSES_AND_CHECK_NOTIFY(_r, _notify) do { \
242 RING_IDX __old = (_r)->sring->rsp_prod; \
243 RING_IDX __new = (_r)->rsp_prod_pvt; \
244 wmb(); /* front sees responses /before/ updated producer index */ \
245 (_r)->sring->rsp_prod = __new; \
246 mb(); /* front sees new responses /before/ we check rsp_event */ \
247 (_notify) = ((RING_IDX)(__new - (_r)->sring->rsp_event) < \
248 (RING_IDX)(__new - __old)); \
249} while (0)
250
251#define RING_FINAL_CHECK_FOR_REQUESTS(_r, _work_to_do) do { \
252 (_work_to_do) = RING_HAS_UNCONSUMED_REQUESTS(_r); \
253 if (_work_to_do) break; \
254 (_r)->sring->req_event = (_r)->req_cons + 1; \
255 mb(); \
256 (_work_to_do) = RING_HAS_UNCONSUMED_REQUESTS(_r); \
257} while (0)
258
259#define RING_FINAL_CHECK_FOR_RESPONSES(_r, _work_to_do) do { \
260 (_work_to_do) = RING_HAS_UNCONSUMED_RESPONSES(_r); \
261 if (_work_to_do) break; \
262 (_r)->sring->rsp_event = (_r)->rsp_cons + 1; \
263 mb(); \
264 (_work_to_do) = RING_HAS_UNCONSUMED_RESPONSES(_r); \
265} while (0)
266
267#endif /* __XEN_PUBLIC_IO_RING_H__ */
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 */
9
10#ifndef __XEN_PUBLIC_IO_RING_H__
11#define __XEN_PUBLIC_IO_RING_H__
12
13#include <xen/interface/grant_table.h>
14
15typedef unsigned int RING_IDX;
16
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))
23
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])))
33
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])))
39
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 */
73
74#define DEFINE_RING_TYPES(__name, __req_t, __rsp_t) \
75 \
76/* Shared ring entry */ \
77union __name##_sring_entry { \
78 __req_t req; \
79 __rsp_t rsp; \
80}; \
81 \
82/* Shared ring page */ \
83struct __name##_sring { \
84 RING_IDX req_prod, req_event; \
85 RING_IDX rsp_prod, rsp_event; \
86 uint8_t pad[48]; \
87 union __name##_sring_entry ring[1]; /* variable-length */ \
88}; \
89 \
90/* "Front" end's private variables */ \
91struct __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 \
98/* "Back" end's private variables */ \
99struct __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};
105
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 */
120
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)
127
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)
134
135#define FRONT_RING_INIT(_r, _s, __size) FRONT_RING_ATTACH(_r, _s, 0, __size)
136
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)
143
144#define BACK_RING_INIT(_r, _s, __size) BACK_RING_ATTACH(_r, _s, 0, __size)
145
146/* How big is this ring? */
147#define RING_SIZE(_r) \
148 ((_r)->nr_ents)
149
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))
153
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)
159
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)
163
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 })
171
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))
175
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 { \
186 /* Use volatile to force the copy into _req. */ \
187 *(_req) = *(volatile typeof(_req))RING_GET_REQUEST(_r, _idx); \
188} while (0)
189
190#define RING_GET_RESPONSE(_r, _idx) \
191 (&((_r)->sring->ring[((_idx) & (RING_SIZE(_r) - 1))].rsp))
192
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))
196
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))
200
201
202#define RING_PUSH_REQUESTS(_r) do { \
203 virt_wmb(); /* back sees requests /before/ updated producer index */ \
204 (_r)->sring->req_prod = (_r)->req_prod_pvt; \
205} while (0)
206
207#define RING_PUSH_RESPONSES(_r) do { \
208 virt_wmb(); /* front sees responses /before/ updated producer index */ \
209 (_r)->sring->rsp_prod = (_r)->rsp_prod_pvt; \
210} while (0)
211
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 */
241
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; \
245 virt_wmb(); /* back sees requests /before/ updated producer index */ \
246 (_r)->sring->req_prod = __new; \
247 virt_mb(); /* back sees new requests /before/ we check req_event */ \
248 (_notify) = ((RING_IDX)(__new - (_r)->sring->req_event) < \
249 (RING_IDX)(__new - __old)); \
250} while (0)
251
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; \
255 virt_wmb(); /* front sees responses /before/ updated producer index */ \
256 (_r)->sring->rsp_prod = __new; \
257 virt_mb(); /* front sees new responses /before/ we check rsp_event */ \
258 (_notify) = ((RING_IDX)(__new - (_r)->sring->rsp_event) < \
259 (RING_IDX)(__new - __old)); \
260} while (0)
261
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)
269
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)
277
278
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 */
319
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))
329
330#define DEFINE_XEN_FLEX_RING(name) \
331static inline RING_IDX name##_mask(RING_IDX idx, RING_IDX ring_size) \
332{ \
333 return idx & (ring_size - 1); \
334} \
335 \
336static 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 \
343static 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 \
361static 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 \
379static 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 \
401struct name##_data { \
402 unsigned char *in; /* half of the allocation */ \
403 unsigned char *out; /* half of the allocation */ \
404}
405
406#define DEFINE_XEN_FLEX_RING_AND_INTF(name) \
407struct 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}; \
419DEFINE_XEN_FLEX_RING(name)
420
421#endif /* __XEN_PUBLIC_IO_RING_H__ */