virt/lib/irqbypass.c

   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);