kernel/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         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  */
 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         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 }
 166 EXPORT_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  */
 175 int 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 }
 216 EXPORT_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  */
 225 void 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 }
 257 EXPORT_SYMBOL_GPL(irq_bypass_unregister_consumer);