1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * IRQ offload/bypass manager
4 *
5 * Copyright (C) 2015 Red Hat, Inc.
6 * Copyright (c) 2015 Linaro Ltd.
7 *
8 * Various virtualization hardware acceleration techniques allow bypassing or
9 * offloading interrupts received from devices around the host kernel. Posted
10 * Interrupts on Intel VT-d systems can allow interrupts to be received
11 * directly by a virtual machine. ARM IRQ Forwarding allows forwarded physical
12 * interrupts to be directly deactivated by the guest. This manager allows
13 * interrupt producers and consumers to find each other to enable this sort of
14 * bypass.
15 */
16
17 #include <linux/irqbypass.h>
18 #include <linux/list.h>
19 #include <linux/module.h>
20 #include <linux/mutex.h>
21
22 MODULE_LICENSE("GPL v2");
23 MODULE_DESCRIPTION("IRQ bypass manager utility module");
24
25 static LIST_HEAD(producers);
26 static LIST_HEAD(consumers);
27 static DEFINE_MUTEX(lock);
28
29 /* @lock must be held when calling connect */
__connect(struct irq_bypass_producer * prod,struct irq_bypass_consumer * cons)30 static int __connect(struct irq_bypass_producer *prod,
31 struct irq_bypass_consumer *cons)
32 {
33 int ret = 0;
34
35 if (prod->stop)
36 prod->stop(prod);
37 if (cons->stop)
38 cons->stop(cons);
39
40 if (prod->add_consumer)
41 ret = prod->add_consumer(prod, cons);
42
43 if (!ret) {
44 ret = cons->add_producer(cons, prod);
45 if (ret && prod->del_consumer)
46 prod->del_consumer(prod, cons);
47 }
48
49 if (cons->start)
50 cons->start(cons);
51 if (prod->start)
52 prod->start(prod);
53
54 return ret;
55 }
56
57 /* @lock must be held when calling disconnect */
__disconnect(struct irq_bypass_producer * prod,struct irq_bypass_consumer * cons)58 static void __disconnect(struct irq_bypass_producer *prod,
59 struct irq_bypass_consumer *cons)
60 {
61 if (prod->stop)
62 prod->stop(prod);
63 if (cons->stop)
64 cons->stop(cons);
65
66 cons->del_producer(cons, prod);
67
68 if (prod->del_consumer)
69 prod->del_consumer(prod, cons);
70
71 if (cons->start)
72 cons->start(cons);
73 if (prod->start)
74 prod->start(prod);
75 }
76
77 /**
78 * irq_bypass_register_producer - register IRQ bypass producer
79 * @producer: pointer to producer structure
80 *
81 * Add the provided IRQ producer to the list of producers and connect
82 * with any matching token found on the IRQ consumers list.
83 */
irq_bypass_register_producer(struct irq_bypass_producer * producer)84 int irq_bypass_register_producer(struct irq_bypass_producer *producer)
85 {
86 struct irq_bypass_producer *tmp;
87 struct irq_bypass_consumer *consumer;
88
89 if (!producer->token)
90 return -EINVAL;
91
92 might_sleep();
93
94 if (!try_module_get(THIS_MODULE))
95 return -ENODEV;
96
97 mutex_lock(&lock);
98
99 list_for_each_entry(tmp, &producers, node) {
100 if (tmp->token == producer->token) {
101 mutex_unlock(&lock);
102 module_put(THIS_MODULE);
103 return -EBUSY;
104 }
105 }
106
107 list_for_each_entry(consumer, &consumers, node) {
108 if (consumer->token == producer->token) {
109 int ret = __connect(producer, consumer);
110 if (ret) {
111 mutex_unlock(&lock);
112 module_put(THIS_MODULE);
113 return ret;
114 }
115 break;
116 }
117 }
118
119 list_add(&producer->node, &producers);
120
121 mutex_unlock(&lock);
122
123 return 0;
124 }
125 EXPORT_SYMBOL_GPL(irq_bypass_register_producer);
126
127 /**
128 * irq_bypass_unregister_producer - unregister IRQ bypass producer
129 * @producer: pointer to producer structure
130 *
131 * Remove a previously registered IRQ producer from the list of producers
132 * and disconnect it from any connected IRQ consumer.
133 */
irq_bypass_unregister_producer(struct irq_bypass_producer * producer)134 void irq_bypass_unregister_producer(struct irq_bypass_producer *producer)
135 {
136 struct irq_bypass_producer *tmp;
137 struct irq_bypass_consumer *consumer;
138
139 if (!producer->token)
140 return;
141
142 might_sleep();
143
144 if (!try_module_get(THIS_MODULE))
145 return; /* nothing in the list anyway */
146
147 mutex_lock(&lock);
148
149 list_for_each_entry(tmp, &producers, node) {
150 if (tmp->token != producer->token)
151 continue;
152
153 list_for_each_entry(consumer, &consumers, node) {
154 if (consumer->token == producer->token) {
155 __disconnect(producer, consumer);
156 break;
157 }
158 }
159
160 list_del(&producer->node);
161 module_put(THIS_MODULE);
162 break;
163 }
164
165 mutex_unlock(&lock);
166
167 module_put(THIS_MODULE);
168 }
169 EXPORT_SYMBOL_GPL(irq_bypass_unregister_producer);
170
171 /**
172 * irq_bypass_register_consumer - register IRQ bypass consumer
173 * @consumer: pointer to consumer structure
174 *
175 * Add the provided IRQ consumer to the list of consumers and connect
176 * with any matching token found on the IRQ producer list.
177 */
irq_bypass_register_consumer(struct irq_bypass_consumer * consumer)178 int irq_bypass_register_consumer(struct irq_bypass_consumer *consumer)
179 {
180 struct irq_bypass_consumer *tmp;
181 struct irq_bypass_producer *producer;
182
183 if (!consumer->token ||
184 !consumer->add_producer || !consumer->del_producer)
185 return -EINVAL;
186
187 might_sleep();
188
189 if (!try_module_get(THIS_MODULE))
190 return -ENODEV;
191
192 mutex_lock(&lock);
193
194 list_for_each_entry(tmp, &consumers, node) {
195 if (tmp->token == consumer->token || tmp == consumer) {
196 mutex_unlock(&lock);
197 module_put(THIS_MODULE);
198 return -EBUSY;
199 }
200 }
201
202 list_for_each_entry(producer, &producers, node) {
203 if (producer->token == consumer->token) {
204 int ret = __connect(producer, consumer);
205 if (ret) {
206 mutex_unlock(&lock);
207 module_put(THIS_MODULE);
208 return ret;
209 }
210 break;
211 }
212 }
213
214 list_add(&consumer->node, &consumers);
215
216 mutex_unlock(&lock);
217
218 return 0;
219 }
220 EXPORT_SYMBOL_GPL(irq_bypass_register_consumer);
221
222 /**
223 * irq_bypass_unregister_consumer - unregister IRQ bypass consumer
224 * @consumer: pointer to consumer structure
225 *
226 * Remove a previously registered IRQ consumer from the list of consumers
227 * and disconnect it from any connected IRQ producer.
228 */
irq_bypass_unregister_consumer(struct irq_bypass_consumer * consumer)229 void irq_bypass_unregister_consumer(struct irq_bypass_consumer *consumer)
230 {
231 struct irq_bypass_consumer *tmp;
232 struct irq_bypass_producer *producer;
233
234 if (!consumer->token)
235 return;
236
237 might_sleep();
238
239 if (!try_module_get(THIS_MODULE))
240 return; /* nothing in the list anyway */
241
242 mutex_lock(&lock);
243
244 list_for_each_entry(tmp, &consumers, node) {
245 if (tmp != consumer)
246 continue;
247
248 list_for_each_entry(producer, &producers, node) {
249 if (producer->token == consumer->token) {
250 __disconnect(producer, consumer);
251 break;
252 }
253 }
254
255 list_del(&consumer->node);
256 module_put(THIS_MODULE);
257 break;
258 }
259
260 mutex_unlock(&lock);
261
262 module_put(THIS_MODULE);
263 }
264 EXPORT_SYMBOL_GPL(irq_bypass_unregister_consumer);
265