virt/lib/irqbypass.c

   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 */
  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 */
  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  */
  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         int ret;
  89
  90         if (!producer->token)
  91                 return -EINVAL;
  92
  93         might_sleep();
  94
  95         if (!try_module_get(THIS_MODULE))
  96                 return -ENODEV;
  97
  98         mutex_lock(&lock);
  99
 100         list_for_each_entry(tmp, &producers, node) {
 101                 if (tmp->token == producer->token) {
 102                         ret = -EBUSY;
 103                         goto out_err;
 104                 }
 105         }
 106
 107         list_for_each_entry(consumer, &consumers, node) {
 108                 if (consumer->token == producer->token) {
 109                         ret = __connect(producer, consumer);
 110                         if (ret)
 111                                 goto out_err;
 112                         break;
 113                 }
 114         }
 115
 116         list_add(&producer->node, &producers);
 117
 118         mutex_unlock(&lock);
 119
 120         return 0;
 121 out_err:
 122         mutex_unlock(&lock);
 123         module_put(THIS_MODULE);
 124         return ret;
 125 }
 126 EXPORT_SYMBOL_GPL(irq_bypass_register_producer);
 127
 128 /**
 129  * irq_bypass_unregister_producer - unregister IRQ bypass producer
 130  * @producer: pointer to producer structure
 131  *
 132  * Remove a previously registered IRQ producer from the list of producers
 133  * and disconnect it from any connected IRQ consumer.
 134  */
 135 void irq_bypass_unregister_producer(struct irq_bypass_producer *producer)
 136 {
 137         struct irq_bypass_producer *tmp;
 138         struct irq_bypass_consumer *consumer;
 139
 140         if (!producer->token)
 141                 return;
 142
 143         might_sleep();
 144
 145         if (!try_module_get(THIS_MODULE))
 146                 return; /* nothing in the list anyway */
 147
 148         mutex_lock(&lock);
 149
 150         list_for_each_entry(tmp, &producers, node) {
 151                 if (tmp->token != producer->token)
 152                         continue;
 153
 154                 list_for_each_entry(consumer, &consumers, node) {
 155                         if (consumer->token == producer->token) {
 156                                 __disconnect(producer, consumer);
 157                                 break;
 158                         }
 159                 }
 160
 161                 list_del(&producer->node);
 162                 module_put(THIS_MODULE);
 163                 break;
 164         }
 165
 166         mutex_unlock(&lock);
 167
 168         module_put(THIS_MODULE);
 169 }
 170 EXPORT_SYMBOL_GPL(irq_bypass_unregister_producer);
 171
 172 /**
 173  * irq_bypass_register_consumer - register IRQ bypass consumer
 174  * @consumer: pointer to consumer structure
 175  *
 176  * Add the provided IRQ consumer to the list of consumers and connect
 177  * with any matching token found on the IRQ producer list.
 178  */
 179 int irq_bypass_register_consumer(struct irq_bypass_consumer *consumer)
 180 {
 181         struct irq_bypass_consumer *tmp;
 182         struct irq_bypass_producer *producer;
 183         int ret;
 184
 185         if (!consumer->token ||
 186             !consumer->add_producer || !consumer->del_producer)
 187                 return -EINVAL;
 188
 189         might_sleep();
 190
 191         if (!try_module_get(THIS_MODULE))
 192                 return -ENODEV;
 193
 194         mutex_lock(&lock);
 195
 196         list_for_each_entry(tmp, &consumers, node) {
 197                 if (tmp->token == consumer->token || tmp == consumer) {
 198                         ret = -EBUSY;
 199                         goto out_err;
 200                 }
 201         }
 202
 203         list_for_each_entry(producer, &producers, node) {
 204                 if (producer->token == consumer->token) {
 205                         ret = __connect(producer, consumer);
 206                         if (ret)
 207                                 goto out_err;
 208                         break;
 209                 }
 210         }
 211
 212         list_add(&consumer->node, &consumers);
 213
 214         mutex_unlock(&lock);
 215
 216         return 0;
 217 out_err:
 218         mutex_unlock(&lock);
 219         module_put(THIS_MODULE);
 220         return ret;
 221 }
 222 EXPORT_SYMBOL_GPL(irq_bypass_register_consumer);
 223
 224 /**
 225  * irq_bypass_unregister_consumer - unregister IRQ bypass consumer
 226  * @consumer: pointer to consumer structure
 227  *
 228  * Remove a previously registered IRQ consumer from the list of consumers
 229  * and disconnect it from any connected IRQ producer.
 230  */
 231 void irq_bypass_unregister_consumer(struct irq_bypass_consumer *consumer)
 232 {
 233         struct irq_bypass_consumer *tmp;
 234         struct irq_bypass_producer *producer;
 235
 236         if (!consumer->token)
 237                 return;
 238
 239         might_sleep();
 240
 241         if (!try_module_get(THIS_MODULE))
 242                 return; /* nothing in the list anyway */
 243
 244         mutex_lock(&lock);
 245
 246         list_for_each_entry(tmp, &consumers, node) {
 247                 if (tmp != consumer)
 248                         continue;
 249
 250                 list_for_each_entry(producer, &producers, node) {
 251                         if (producer->token == consumer->token) {
 252                                 __disconnect(producer, consumer);
 253                                 break;
 254                         }
 255                 }
 256
 257                 list_del(&consumer->node);
 258                 module_put(THIS_MODULE);
 259                 break;
 260         }
 261
 262         mutex_unlock(&lock);
 263
 264         module_put(THIS_MODULE);
 265 }
 266 EXPORT_SYMBOL_GPL(irq_bypass_unregister_consumer);