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
25MODULE_LICENSE("GPL v2");
26MODULE_DESCRIPTION("IRQ bypass manager utility module");
27
28static LIST_HEAD(producers);
29static LIST_HEAD(consumers);
30static DEFINE_MUTEX(lock);
31
32/* @lock must be held when calling connect */
33static 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 */
61static 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 */
87int irq_bypass_register_producer(struct irq_bypass_producer *producer)
88{
89	struct irq_bypass_producer *tmp;
90	struct irq_bypass_consumer *consumer;
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}
125EXPORT_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 */
134void irq_bypass_unregister_producer(struct irq_bypass_producer *producer)
135{
136	struct irq_bypass_producer *tmp;
137	struct irq_bypass_consumer *consumer;
138
139	might_sleep();
140
141	if (!try_module_get(THIS_MODULE))
142		return; /* nothing in the list anyway */
143
144	mutex_lock(&lock);
145
146	list_for_each_entry(tmp, &producers, node) {
147		if (tmp->token != producer->token)
148			continue;
149
150		list_for_each_entry(consumer, &consumers, node) {
151			if (consumer->token == producer->token) {
152				__disconnect(producer, consumer);
153				break;
154			}
155		}
156
157		list_del(&producer->node);
158		module_put(THIS_MODULE);
159		break;
160	}
161
162	mutex_unlock(&lock);
163
164	module_put(THIS_MODULE);
165}
166EXPORT_SYMBOL_GPL(irq_bypass_unregister_producer);
167
168/**
169 * irq_bypass_register_consumer - register IRQ bypass consumer
170 * @consumer: pointer to consumer structure
171 *
172 * Add the provided IRQ consumer to the list of consumers and connect
173 * with any matching token found on the IRQ producer list.
174 */
175int irq_bypass_register_consumer(struct irq_bypass_consumer *consumer)
176{
177	struct irq_bypass_consumer *tmp;
178	struct irq_bypass_producer *producer;
179
180	if (!consumer->add_producer || !consumer->del_producer)
181		return -EINVAL;
182
183	might_sleep();
184
185	if (!try_module_get(THIS_MODULE))
186		return -ENODEV;
187
188	mutex_lock(&lock);
189
190	list_for_each_entry(tmp, &consumers, node) {
191		if (tmp->token == consumer->token) {
192			mutex_unlock(&lock);
193			module_put(THIS_MODULE);
194			return -EBUSY;
195		}
196	}
197
198	list_for_each_entry(producer, &producers, node) {
199		if (producer->token == consumer->token) {
200			int ret = __connect(producer, consumer);
201			if (ret) {
202				mutex_unlock(&lock);
203				module_put(THIS_MODULE);
204				return ret;
205			}
206			break;
207		}
208	}
209
210	list_add(&consumer->node, &consumers);
211
212	mutex_unlock(&lock);
213
214	return 0;
215}
216EXPORT_SYMBOL_GPL(irq_bypass_register_consumer);
217
218/**
219 * irq_bypass_unregister_consumer - unregister IRQ bypass consumer
220 * @consumer: pointer to consumer structure
221 *
222 * Remove a previously registered IRQ consumer from the list of consumers
223 * and disconnect it from any connected IRQ producer.
224 */
225void irq_bypass_unregister_consumer(struct irq_bypass_consumer *consumer)
226{
227	struct irq_bypass_consumer *tmp;
228	struct irq_bypass_producer *producer;
229
230	might_sleep();
231
232	if (!try_module_get(THIS_MODULE))
233		return; /* nothing in the list anyway */
234
235	mutex_lock(&lock);
236
237	list_for_each_entry(tmp, &consumers, node) {
238		if (tmp->token != consumer->token)
239			continue;
240
241		list_for_each_entry(producer, &producers, node) {
242			if (producer->token == consumer->token) {
243				__disconnect(producer, consumer);
244				break;
245			}
246		}
247
248		list_del(&consumer->node);
249		module_put(THIS_MODULE);
250		break;
251	}
252
253	mutex_unlock(&lock);
254
255	module_put(THIS_MODULE);
256}
257EXPORT_SYMBOL_GPL(irq_bypass_unregister_consumer);
258