irqbypass: Take ownership of producer/consumer token tracking

Move ownership of IRQ bypass token tracking into irqbypass.ko, and
explicitly require callers to pass an eventfd_ctx structure instead of a
completely opaque token.  Relying on producers and consumers to set the
token appropriately is error prone, and hiding the fact that the token must
be an eventfd_ctx pointer (for all intents and purposes) unnecessarily
obfuscates the code and makes it more brittle.

Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Alex Williamson <alex.williamson@redhat.com>
Link: https://lore.kernel.org/r/20250516230734.2564775-4-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index b58a74c1722de3f2d180cf8d6a3cf0ce9cf534fd..3dc93e2d47774530fafd3c38fe4c2ff163d7adcf 100644 (file)
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -13669,8 +13669,8 @@ void kvm_arch_irq_bypass_del_producer(struct irq_bypass_consumer *cons,
        ret = kvm_x86_call(pi_update_irte)(irqfd->kvm,
                                           prod->irq, irqfd->gsi, 0);
        if (ret)
-               printk(KERN_INFO "irq bypass consumer (token %p) unregistration"
-                      " fails: %d\n", irqfd->consumer.token, ret);
+               printk(KERN_INFO "irq bypass consumer (eventfd %p) unregistration"
+                      " fails: %d\n", irqfd->consumer.eventfd, ret);
 
        spin_unlock_irq(&kvm->irqfds.lock);
 

diff --git a/drivers/vfio/pci/vfio_pci_intrs.c b/drivers/vfio/pci/vfio_pci_intrs.c
index 565966351dfadc590f6ab59b5cabce1b3a5b09f7..d87fe116762a3e2adc8eb612093fd125b2fa1641 100644 (file)
--- a/drivers/vfio/pci/vfio_pci_intrs.c
+++ b/drivers/vfio/pci/vfio_pci_intrs.c
@@ -505,15 +505,12 @@ static int vfio_msi_set_vector_signal(struct vfio_pci_core_device *vdev,
        if (ret)
                goto out_put_eventfd_ctx;
 
-       ctx->producer.token = trigger;
        ctx->producer.irq = irq;
-       ret = irq_bypass_register_producer(&ctx->producer);
+       ret = irq_bypass_register_producer(&ctx->producer, trigger);
        if (unlikely(ret)) {
                dev_info(&pdev->dev,
-               "irq bypass producer (token %p) registration fails: %d\n",
-               ctx->producer.token, ret);
-
-               ctx->producer.token = NULL;
+               "irq bypass producer (eventfd %p) registration fails: %d\n",
+               trigger, ret);
        }
        ctx->trigger = trigger;
 

diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c
index 5a49b5a6d49641e75b1e3f09086ef19bee7d0d6f..7b265ffda6970b553deee15371587d0e7ade2460 100644 (file)
--- a/drivers/vhost/vdpa.c
+++ b/drivers/vhost/vdpa.c
@@ -213,10 +213,10 @@ static void vhost_vdpa_setup_vq_irq(struct vhost_vdpa *v, u16 qid)
                return;
 
        vq->call_ctx.producer.irq = irq;
-       ret = irq_bypass_register_producer(&vq->call_ctx.producer);
+       ret = irq_bypass_register_producer(&vq->call_ctx.producer, vq->call_ctx.ctx);
        if (unlikely(ret))
-               dev_info(&v->dev, "vq %u, irq bypass producer (token %p) registration fails, ret =  %d\n",
-                        qid, vq->call_ctx.producer.token, ret);
+               dev_info(&v->dev, "vq %u, irq bypass producer (eventfd %p) registration fails, ret =  %d\n",
+                        qid, vq->call_ctx.ctx, ret);
 }
 
 static void vhost_vdpa_unsetup_vq_irq(struct vhost_vdpa *v, u16 qid)
@@ -712,7 +712,6 @@ static long vhost_vdpa_vring_ioctl(struct vhost_vdpa *v, unsigned int cmd,
                        if (ops->get_status(vdpa) &
                            VIRTIO_CONFIG_S_DRIVER_OK)
                                vhost_vdpa_unsetup_vq_irq(v, idx);
-                       vq->call_ctx.producer.token = NULL;
                }
                break;
        }
@@ -753,7 +752,6 @@ static long vhost_vdpa_vring_ioctl(struct vhost_vdpa *v, unsigned int cmd,
                        cb.callback = vhost_vdpa_virtqueue_cb;
                        cb.private = vq;
                        cb.trigger = vq->call_ctx.ctx;
-                       vq->call_ctx.producer.token = vq->call_ctx.ctx;
                        if (ops->get_status(vdpa) &
                            VIRTIO_CONFIG_S_DRIVER_OK)
                                vhost_vdpa_setup_vq_irq(v, idx);

diff --git a/include/linux/irqbypass.h b/include/linux/irqbypass.h
index 9bdb2a7818418d53d06feeac3f6d20b56f979531..1b57d15ac4cf21e7c009508cb55ca2bec7f9e0b8 100644 (file)
--- a/include/linux/irqbypass.h
+++ b/include/linux/irqbypass.h
@@ -10,6 +10,7 @@
 
 #include <linux/list.h>
 
+struct eventfd_ctx;
 struct irq_bypass_consumer;
 
 /*
@@ -18,20 +19,20 @@ struct irq_bypass_consumer;
  * The IRQ bypass manager is a simple set of lists and callbacks that allows
  * IRQ producers (ex. physical interrupt sources) to be matched to IRQ
  * consumers (ex. virtualization hardware that allows IRQ bypass or offload)
- * via a shared token (ex. eventfd_ctx).  Producers and consumers register
- * independently.  When a token match is found, the optional @stop callback
- * will be called for each participant.  The pair will then be connected via
- * the @add_* callbacks, and finally the optional @start callback will allow
- * any final coordination.  When either participant is unregistered, the
- * process is repeated using the @del_* callbacks in place of the @add_*
- * callbacks.  Match tokens must be unique per producer/consumer, 1:N pairings
- * are not supported.
+ * via a shared eventfd_ctx.  Producers and consumers register independently.
+ * When a producer and consumer are paired, i.e. an eventfd match is found, the
+ * optional @stop callback will be called for each participant.  The pair will
+ * then be connected via the @add_* callbacks, and finally the optional @start
+ * callback will allow any final coordination.  When either participant is
+ * unregistered, the process is repeated using the @del_* callbacks in place of
+ * the @add_* callbacks.  eventfds must be unique per producer/consumer, 1:N
+ * pairings are not supported.
  */
 
 /**
  * struct irq_bypass_producer - IRQ bypass producer definition
  * @node: IRQ bypass manager private list management
- * @token: opaque token to match between producer and consumer (non-NULL)
+ * @eventfd: eventfd context used to match producers and consumers
  * @irq: Linux IRQ number for the producer device
  * @add_consumer: Connect the IRQ producer to an IRQ consumer (optional)
  * @del_consumer: Disconnect the IRQ producer from an IRQ consumer (optional)
@@ -44,7 +45,7 @@ struct irq_bypass_consumer;
  */
 struct irq_bypass_producer {
        struct list_head node;
-       void *token;
+       struct eventfd_ctx *eventfd;
        int irq;
        int (*add_consumer)(struct irq_bypass_producer *,
                            struct irq_bypass_consumer *);
@@ -57,7 +58,7 @@ struct irq_bypass_producer {
 /**
  * struct irq_bypass_consumer - IRQ bypass consumer definition
  * @node: IRQ bypass manager private list management
- * @token: opaque token to match between producer and consumer (non-NULL)
+ * @eventfd: eventfd context used to match producers and consumers
  * @add_producer: Connect the IRQ consumer to an IRQ producer
  * @del_producer: Disconnect the IRQ consumer from an IRQ producer
  * @stop: Perform any quiesce operations necessary prior to add/del (optional)
@@ -70,7 +71,7 @@ struct irq_bypass_producer {
  */
 struct irq_bypass_consumer {
        struct list_head node;
-       void *token;
+       struct eventfd_ctx *eventfd;
        int (*add_producer)(struct irq_bypass_consumer *,
                            struct irq_bypass_producer *);
        void (*del_producer)(struct irq_bypass_consumer *,
@@ -79,9 +80,11 @@ struct irq_bypass_consumer {
        void (*start)(struct irq_bypass_consumer *);
 };
 
-int irq_bypass_register_producer(struct irq_bypass_producer *);
-void irq_bypass_unregister_producer(struct irq_bypass_producer *);
-int irq_bypass_register_consumer(struct irq_bypass_consumer *);
-void irq_bypass_unregister_consumer(struct irq_bypass_consumer *);
+int irq_bypass_register_producer(struct irq_bypass_producer *producer,
+                                struct eventfd_ctx *eventfd);
+void irq_bypass_unregister_producer(struct irq_bypass_producer *producer);
+int irq_bypass_register_consumer(struct irq_bypass_consumer *consumer,
+                                struct eventfd_ctx *eventfd);
+void irq_bypass_unregister_consumer(struct irq_bypass_consumer *consumer);
 
 #endif /* IRQBYPASS_H */

diff --git a/virt/kvm/eventfd.c b/virt/kvm/eventfd.c
index 11e5d1e3f12eae2d5aab717f52fcfee7df8190f3..5bc6abe3074889a94a3f7c27861dd3c96f902092 100644 (file)
--- a/virt/kvm/eventfd.c
+++ b/virt/kvm/eventfd.c
@@ -426,15 +426,14 @@ kvm_irqfd_assign(struct kvm *kvm, struct kvm_irqfd *args)
 
 #if IS_ENABLED(CONFIG_HAVE_KVM_IRQ_BYPASS)
        if (kvm_arch_has_irq_bypass()) {
-               irqfd->consumer.token = (void *)irqfd->eventfd;
                irqfd->consumer.add_producer = kvm_arch_irq_bypass_add_producer;
                irqfd->consumer.del_producer = kvm_arch_irq_bypass_del_producer;
                irqfd->consumer.stop = kvm_arch_irq_bypass_stop;
                irqfd->consumer.start = kvm_arch_irq_bypass_start;
-               ret = irq_bypass_register_consumer(&irqfd->consumer);
+               ret = irq_bypass_register_consumer(&irqfd->consumer, irqfd->eventfd);
                if (ret)
-                       pr_info("irq bypass consumer (token %p) registration fails: %d\n",
-                               irqfd->consumer.token, ret);
+                       pr_info("irq bypass consumer (eventfd %p) registration fails: %d\n",
+                               irqfd->eventfd, ret);
        }
 #endif
 

diff --git a/virt/lib/irqbypass.c b/virt/lib/irqbypass.c
index 28a4d933569aca7d9fabbc61041a9b08f2b623cf..e8d7c420db52c89558f68753a4646b397a3fef2c 100644 (file)
--- a/virt/lib/irqbypass.c
+++ b/virt/lib/irqbypass.c
@@ -77,30 +77,32 @@ static void __disconnect(struct irq_bypass_producer *prod,
 /**
  * irq_bypass_register_producer - register IRQ bypass producer
  * @producer: pointer to producer structure
+ * @eventfd: pointer to the eventfd context associated with the producer
  *
  * Add the provided IRQ producer to the list of producers and connect
- * with any matching token found on the IRQ consumers list.
+ * with any matching eventfd found on the IRQ consumers list.
  */
-int irq_bypass_register_producer(struct irq_bypass_producer *producer)
+int irq_bypass_register_producer(struct irq_bypass_producer *producer,
+                                struct eventfd_ctx *eventfd)
 {
        struct irq_bypass_producer *tmp;
        struct irq_bypass_consumer *consumer;
        int ret;
 
-       if (!producer->token)
+       if (WARN_ON_ONCE(producer->eventfd))
                return -EINVAL;
 
        mutex_lock(&lock);
 
        list_for_each_entry(tmp, &producers, node) {
-               if (tmp->token == producer->token) {
+               if (tmp->eventfd == eventfd) {
                        ret = -EBUSY;
                        goto out_err;
                }
        }
 
        list_for_each_entry(consumer, &consumers, node) {
-               if (consumer->token == producer->token) {
+               if (consumer->eventfd == eventfd) {
                        ret = __connect(producer, consumer);
                        if (ret)
                                goto out_err;
@@ -108,6 +110,7 @@ int irq_bypass_register_producer(struct irq_bypass_producer *producer)
                }
        }
 
+       producer->eventfd = eventfd;
        list_add(&producer->node, &producers);
 
        mutex_unlock(&lock);
@@ -131,26 +134,28 @@ void irq_bypass_unregister_producer(struct irq_bypass_producer *producer)
        struct irq_bypass_producer *tmp;
        struct irq_bypass_consumer *consumer;
 
-       if (!producer->token)
+       if (!producer->eventfd)
                return;
 
        mutex_lock(&lock);
 
        list_for_each_entry(tmp, &producers, node) {
-               if (tmp->token != producer->token)
+               if (tmp->eventfd != producer->eventfd)
                        continue;
 
                list_for_each_entry(consumer, &consumers, node) {
-                       if (consumer->token == producer->token) {
+                       if (consumer->eventfd == producer->eventfd) {
                                __disconnect(producer, consumer);
                                break;
                        }
                }
 
+               producer->eventfd = NULL;
                list_del(&producer->node);
                break;
        }
 
+       WARN_ON_ONCE(producer->eventfd);
        mutex_unlock(&lock);
 }
 EXPORT_SYMBOL_GPL(irq_bypass_unregister_producer);
@@ -158,31 +163,35 @@ EXPORT_SYMBOL_GPL(irq_bypass_unregister_producer);
 /**
  * irq_bypass_register_consumer - register IRQ bypass consumer
  * @consumer: pointer to consumer structure
+ * @eventfd: pointer to the eventfd context associated with the consumer
  *
  * Add the provided IRQ consumer to the list of consumers and connect
- * with any matching token found on the IRQ producer list.
+ * with any matching eventfd found on the IRQ producer list.
  */
-int irq_bypass_register_consumer(struct irq_bypass_consumer *consumer)
+int irq_bypass_register_consumer(struct irq_bypass_consumer *consumer,
+                                struct eventfd_ctx *eventfd)
 {
        struct irq_bypass_consumer *tmp;
        struct irq_bypass_producer *producer;
        int ret;
 
-       if (!consumer->token ||
-           !consumer->add_producer || !consumer->del_producer)
+       if (WARN_ON_ONCE(consumer->eventfd))
+               return -EINVAL;
+
+       if (!consumer->add_producer || !consumer->del_producer)
                return -EINVAL;
 
        mutex_lock(&lock);
 
        list_for_each_entry(tmp, &consumers, node) {
-               if (tmp->token == consumer->token || tmp == consumer) {
+               if (tmp->eventfd == eventfd) {
                        ret = -EBUSY;
                        goto out_err;
                }
        }
 
        list_for_each_entry(producer, &producers, node) {
-               if (producer->token == consumer->token) {
+               if (producer->eventfd == eventfd) {
                        ret = __connect(producer, consumer);
                        if (ret)
                                goto out_err;
@@ -190,6 +199,7 @@ int irq_bypass_register_consumer(struct irq_bypass_consumer *consumer)
                }
        }
 
+       consumer->eventfd = eventfd;
        list_add(&consumer->node, &consumers);
 
        mutex_unlock(&lock);
@@ -213,7 +223,7 @@ void irq_bypass_unregister_consumer(struct irq_bypass_consumer *consumer)
        struct irq_bypass_consumer *tmp;
        struct irq_bypass_producer *producer;
 
-       if (!consumer->token)
+       if (!consumer->eventfd)
                return;
 
        mutex_lock(&lock);
@@ -223,16 +233,18 @@ void irq_bypass_unregister_consumer(struct irq_bypass_consumer *consumer)
                        continue;
 
                list_for_each_entry(producer, &producers, node) {
-                       if (producer->token == consumer->token) {
+                       if (producer->eventfd == consumer->eventfd) {
                                __disconnect(producer, consumer);
                                break;
                        }
                }
 
+               consumer->eventfd = NULL;
                list_del(&consumer->node);
                break;
        }
 
+       WARN_ON_ONCE(consumer->eventfd);
        mutex_unlock(&lock);
 }
 EXPORT_SYMBOL_GPL(irq_bypass_unregister_consumer);