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1 /*
2 * IRQ offload/bypass manager
3 *
4 * Copyright (C) 2015 Red Hat, Inc.
5 * Copyright (c) 2015 Linaro Ltd.
6 *
7 * This program is free software; you can redistribute it and/or modify
8 * it under the terms of the GNU General Public License version 2 as
9 * published by the Free Software Foundation.
10 *
11 * Various virtualization hardware acceleration techniques allow bypassing or
12 * offloading interrupts received from devices around the host kernel. Posted
13 * Interrupts on Intel VT-d systems can allow interrupts to be received
14 * directly by a virtual machine. ARM IRQ Forwarding allows forwarded physical
15 * interrupts to be directly deactivated by the guest. This manager allows
16 * interrupt producers and consumers to find each other to enable this sort of
17 * bypass.
18 */
19
20 #include <linux/irqbypass.h>
21 #include <linux/list.h>
22 #include <linux/module.h>
23 #include <linux/mutex.h>
24
25 MODULE_LICENSE("GPL v2");
26 MODULE_DESCRIPTION("IRQ bypass manager utility module");
27
28 static LIST_HEAD(producers);
29 static LIST_HEAD(consumers);
30 static DEFINE_MUTEX(lock);
31
32 /* @lock must be held when calling connect */
33 static int __connect(struct irq_bypass_producer *prod,
34 struct irq_bypass_consumer *cons)
35 {
36 int ret = 0;
37
38 if (prod->stop)
39 prod->stop(prod);
40 if (cons->stop)
41 cons->stop(cons);
42
43 if (prod->add_consumer)
44 ret = prod->add_consumer(prod, cons);
45
46 if (!ret) {
47 ret = cons->add_producer(cons, prod);
48 if (ret && prod->del_consumer)
49 prod->del_consumer(prod, cons);
50 }
51
52 if (cons->start)
53 cons->start(cons);
54 if (prod->start)
55 prod->start(prod);
56
57 return ret;
58 }
59
60 /* @lock must be held when calling disconnect */
61 static void __disconnect(struct irq_bypass_producer *prod,
62 struct irq_bypass_consumer *cons)
63 {
64 if (prod->stop)
65 prod->stop(prod);
66 if (cons->stop)
67 cons->stop(cons);
68
69 cons->del_producer(cons, prod);
70
71 if (prod->del_consumer)
72 prod->del_consumer(prod, cons);
73
74 if (cons->start)
75 cons->start(cons);
76 if (prod->start)
77 prod->start(prod);
78 }
79
80 /**
81 * irq_bypass_register_producer - register IRQ bypass producer
82 * @producer: pointer to producer structure
83 *
84 * Add the provided IRQ producer to the list of producers and connect
85 * with any matching token found on the IRQ consumers list.
86 */
87 int irq_bypass_register_producer(struct irq_bypass_producer *producer)
88 {
89 struct irq_bypass_producer *tmp;
90 struct irq_bypass_consumer *consumer;
91
92 if (!producer->token)
93 return -EINVAL;
94
95 might_sleep();
96
97 if (!try_module_get(THIS_MODULE))
98 return -ENODEV;
99
100 mutex_lock(&lock);
101
102 list_for_each_entry(tmp, &producers, node) {
103 if (tmp->token == producer->token) {
104 mutex_unlock(&lock);
105 module_put(THIS_MODULE);
106 return -EBUSY;
107 }
108 }
109
110 list_for_each_entry(consumer, &consumers, node) {
111 if (consumer->token == producer->token) {
112 int ret = __connect(producer, consumer);
113 if (ret) {
114 mutex_unlock(&lock);
115 module_put(THIS_MODULE);
116 return ret;
117 }
118 break;
119 }
120 }
121
122 list_add(&producer->node, &producers);
123
124 mutex_unlock(&lock);
125
126 return 0;
127 }
128 EXPORT_SYMBOL_GPL(irq_bypass_register_producer);
129
130 /**
131 * irq_bypass_unregister_producer - unregister IRQ bypass producer
132 * @producer: pointer to producer structure
133 *
134 * Remove a previously registered IRQ producer from the list of producers
135 * and disconnect it from any connected IRQ consumer.
136 */
137 void irq_bypass_unregister_producer(struct irq_bypass_producer *producer)
138 {
139 struct irq_bypass_producer *tmp;
140 struct irq_bypass_consumer *consumer;
141
142 if (!producer->token)
143 return;
144
145 might_sleep();
146
147 if (!try_module_get(THIS_MODULE))
148 return; /* nothing in the list anyway */
149
150 mutex_lock(&lock);
151
152 list_for_each_entry(tmp, &producers, node) {
153 if (tmp->token != producer->token)
154 continue;
155
156 list_for_each_entry(consumer, &consumers, node) {
157 if (consumer->token == producer->token) {
158 __disconnect(producer, consumer);
159 break;
160 }
161 }
162
163 list_del(&producer->node);
164 module_put(THIS_MODULE);
165 break;
166 }
167
168 mutex_unlock(&lock);
169
170 module_put(THIS_MODULE);
171 }
172 EXPORT_SYMBOL_GPL(irq_bypass_unregister_producer);
173
174 /**
175 * irq_bypass_register_consumer - register IRQ bypass consumer
176 * @consumer: pointer to consumer structure
177 *
178 * Add the provided IRQ consumer to the list of consumers and connect
179 * with any matching token found on the IRQ producer list.
180 */
181 int irq_bypass_register_consumer(struct irq_bypass_consumer *consumer)
182 {
183 struct irq_bypass_consumer *tmp;
184 struct irq_bypass_producer *producer;
185
186 if (!consumer->token ||
187 !consumer->add_producer || !consumer->del_producer)
188 return -EINVAL;
189
190 might_sleep();
191
192 if (!try_module_get(THIS_MODULE))
193 return -ENODEV;
194
195 mutex_lock(&lock);
196
197 list_for_each_entry(tmp, &consumers, node) {
198 if (tmp->token == consumer->token || tmp == consumer) {
199 mutex_unlock(&lock);
200 module_put(THIS_MODULE);
201 return -EBUSY;
202 }
203 }
204
205 list_for_each_entry(producer, &producers, node) {
206 if (producer->token == consumer->token) {
207 int ret = __connect(producer, consumer);
208 if (ret) {
209 mutex_unlock(&lock);
210 module_put(THIS_MODULE);
211 return ret;
212 }
213 break;
214 }
215 }
216
217 list_add(&consumer->node, &consumers);
218
219 mutex_unlock(&lock);
220
221 return 0;
222 }
223 EXPORT_SYMBOL_GPL(irq_bypass_register_consumer);
224
225 /**
226 * irq_bypass_unregister_consumer - unregister IRQ bypass consumer
227 * @consumer: pointer to consumer structure
228 *
229 * Remove a previously registered IRQ consumer from the list of consumers
230 * and disconnect it from any connected IRQ producer.
231 */
232 void irq_bypass_unregister_consumer(struct irq_bypass_consumer *consumer)
233 {
234 struct irq_bypass_consumer *tmp;
235 struct irq_bypass_producer *producer;
236
237 if (!consumer->token)
238 return;
239
240 might_sleep();
241
242 if (!try_module_get(THIS_MODULE))
243 return; /* nothing in the list anyway */
244
245 mutex_lock(&lock);
246
247 list_for_each_entry(tmp, &consumers, node) {
248 if (tmp != consumer)
249 continue;
250
251 list_for_each_entry(producer, &producers, node) {
252 if (producer->token == consumer->token) {
253 __disconnect(producer, consumer);
254 break;
255 }
256 }
257
258 list_del(&consumer->node);
259 module_put(THIS_MODULE);
260 break;
261 }
262
263 mutex_unlock(&lock);
264
265 module_put(THIS_MODULE);
266 }
267 EXPORT_SYMBOL_GPL(irq_bypass_unregister_consumer);