Adding upstream version 5.10.209.upstream/5.10.209upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 964 insertions, 0 deletions

diff --git a/virt/kvm/eventfd.c b/virt/kvm/eventfd.c
new file mode 100644
index 000000000..518cd8dc3
--- /dev/null
+++ b/virt/kvm/eventfd.c
@@ -0,0 +1,964 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * kvm eventfd support - use eventfd objects to signal various KVM events
+ *
+ * Copyright 2009 Novell.  All Rights Reserved.
+ * Copyright 2010 Red Hat, Inc. and/or its affiliates.
+ *
+ * Author:
+ *	Gregory Haskins <ghaskins@novell.com>
+ */
+
+#include <linux/kvm_host.h>
+#include <linux/kvm.h>
+#include <linux/kvm_irqfd.h>
+#include <linux/workqueue.h>
+#include <linux/syscalls.h>
+#include <linux/wait.h>
+#include <linux/poll.h>
+#include <linux/file.h>
+#include <linux/list.h>
+#include <linux/eventfd.h>
+#include <linux/kernel.h>
+#include <linux/srcu.h>
+#include <linux/slab.h>
+#include <linux/seqlock.h>
+#include <linux/irqbypass.h>
+#include <trace/events/kvm.h>
+
+#include <kvm/iodev.h>
+
+#ifdef CONFIG_HAVE_KVM_IRQFD
+
+static struct workqueue_struct *irqfd_cleanup_wq;
+
+bool __attribute__((weak))
+kvm_arch_irqfd_allowed(struct kvm *kvm, struct kvm_irqfd *args)
+{
+	return true;
+}
+
+static void
+irqfd_inject(struct work_struct *work)
+{
+	struct kvm_kernel_irqfd *irqfd =
+		container_of(work, struct kvm_kernel_irqfd, inject);
+	struct kvm *kvm = irqfd->kvm;
+
+	if (!irqfd->resampler) {
+		kvm_set_irq(kvm, KVM_USERSPACE_IRQ_SOURCE_ID, irqfd->gsi, 1,
+				false);
+		kvm_set_irq(kvm, KVM_USERSPACE_IRQ_SOURCE_ID, irqfd->gsi, 0,
+				false);
+	} else
+		kvm_set_irq(kvm, KVM_IRQFD_RESAMPLE_IRQ_SOURCE_ID,
+			    irqfd->gsi, 1, false);
+}
+
+/*
+ * Since resampler irqfds share an IRQ source ID, we de-assert once
+ * then notify all of the resampler irqfds using this GSI.  We can't
+ * do multiple de-asserts or we risk racing with incoming re-asserts.
+ */
+static void
+irqfd_resampler_ack(struct kvm_irq_ack_notifier *kian)
+{
+	struct kvm_kernel_irqfd_resampler *resampler;
+	struct kvm *kvm;
+	struct kvm_kernel_irqfd *irqfd;
+	int idx;
+
+	resampler = container_of(kian,
+			struct kvm_kernel_irqfd_resampler, notifier);
+	kvm = resampler->kvm;
+
+	kvm_set_irq(kvm, KVM_IRQFD_RESAMPLE_IRQ_SOURCE_ID,
+		    resampler->notifier.gsi, 0, false);
+
+	idx = srcu_read_lock(&kvm->irq_srcu);
+
+	list_for_each_entry_rcu(irqfd, &resampler->list, resampler_link)
+		eventfd_signal(irqfd->resamplefd, 1);
+
+	srcu_read_unlock(&kvm->irq_srcu, idx);
+}
+
+static void
+irqfd_resampler_shutdown(struct kvm_kernel_irqfd *irqfd)
+{
+	struct kvm_kernel_irqfd_resampler *resampler = irqfd->resampler;
+	struct kvm *kvm = resampler->kvm;
+
+	mutex_lock(&kvm->irqfds.resampler_lock);
+
+	list_del_rcu(&irqfd->resampler_link);
+	synchronize_srcu(&kvm->irq_srcu);
+
+	if (list_empty(&resampler->list)) {
+		list_del(&resampler->link);
+		kvm_unregister_irq_ack_notifier(kvm, &resampler->notifier);
+		kvm_set_irq(kvm, KVM_IRQFD_RESAMPLE_IRQ_SOURCE_ID,
+			    resampler->notifier.gsi, 0, false);
+		kfree(resampler);
+	}
+
+	mutex_unlock(&kvm->irqfds.resampler_lock);
+}
+
+/*
+ * Race-free decouple logic (ordering is critical)
+ */
+static void
+irqfd_shutdown(struct work_struct *work)
+{
+	struct kvm_kernel_irqfd *irqfd =
+		container_of(work, struct kvm_kernel_irqfd, shutdown);
+	struct kvm *kvm = irqfd->kvm;
+	u64 cnt;
+
+	/* Make sure irqfd has been initialized in assign path. */
+	synchronize_srcu(&kvm->irq_srcu);
+
+	/*
+	 * Synchronize with the wait-queue and unhook ourselves to prevent
+	 * further events.
+	 */
+	eventfd_ctx_remove_wait_queue(irqfd->eventfd, &irqfd->wait, &cnt);
+
+	/*
+	 * We know no new events will be scheduled at this point, so block
+	 * until all previously outstanding events have completed
+	 */
+	flush_work(&irqfd->inject);
+
+	if (irqfd->resampler) {
+		irqfd_resampler_shutdown(irqfd);
+		eventfd_ctx_put(irqfd->resamplefd);
+	}
+
+	/*
+	 * It is now safe to release the object's resources
+	 */
+#ifdef CONFIG_HAVE_KVM_IRQ_BYPASS
+	irq_bypass_unregister_consumer(&irqfd->consumer);
+#endif
+	eventfd_ctx_put(irqfd->eventfd);
+	kfree(irqfd);
+}
+
+
+/* assumes kvm->irqfds.lock is held */
+static bool
+irqfd_is_active(struct kvm_kernel_irqfd *irqfd)
+{
+	return list_empty(&irqfd->list) ? false : true;
+}
+
+/*
+ * Mark the irqfd as inactive and schedule it for removal
+ *
+ * assumes kvm->irqfds.lock is held
+ */
+static void
+irqfd_deactivate(struct kvm_kernel_irqfd *irqfd)
+{
+	BUG_ON(!irqfd_is_active(irqfd));
+
+	list_del_init(&irqfd->list);
+
+	queue_work(irqfd_cleanup_wq, &irqfd->shutdown);
+}
+
+int __attribute__((weak)) kvm_arch_set_irq_inatomic(
+				struct kvm_kernel_irq_routing_entry *irq,
+				struct kvm *kvm, int irq_source_id,
+				int level,
+				bool line_status)
+{
+	return -EWOULDBLOCK;
+}
+
+/*
+ * Called with wqh->lock held and interrupts disabled
+ */
+static int
+irqfd_wakeup(wait_queue_entry_t *wait, unsigned mode, int sync, void *key)
+{
+	struct kvm_kernel_irqfd *irqfd =
+		container_of(wait, struct kvm_kernel_irqfd, wait);
+	__poll_t flags = key_to_poll(key);
+	struct kvm_kernel_irq_routing_entry irq;
+	struct kvm *kvm = irqfd->kvm;
+	unsigned seq;
+	int idx;
+
+	if (flags & EPOLLIN) {
+		idx = srcu_read_lock(&kvm->irq_srcu);
+		do {
+			seq = read_seqcount_begin(&irqfd->irq_entry_sc);
+			irq = irqfd->irq_entry;
+		} while (read_seqcount_retry(&irqfd->irq_entry_sc, seq));
+		/* An event has been signaled, inject an interrupt */
+		if (kvm_arch_set_irq_inatomic(&irq, kvm,
+					      KVM_USERSPACE_IRQ_SOURCE_ID, 1,
+					      false) == -EWOULDBLOCK)
+			schedule_work(&irqfd->inject);
+		srcu_read_unlock(&kvm->irq_srcu, idx);
+	}
+
+	if (flags & EPOLLHUP) {
+		/* The eventfd is closing, detach from KVM */
+		unsigned long iflags;
+
+		spin_lock_irqsave(&kvm->irqfds.lock, iflags);
+
+		/*
+		 * We must check if someone deactivated the irqfd before
+		 * we could acquire the irqfds.lock since the item is
+		 * deactivated from the KVM side before it is unhooked from
+		 * the wait-queue.  If it is already deactivated, we can
+		 * simply return knowing the other side will cleanup for us.
+		 * We cannot race against the irqfd going away since the
+		 * other side is required to acquire wqh->lock, which we hold
+		 */
+		if (irqfd_is_active(irqfd))
+			irqfd_deactivate(irqfd);
+
+		spin_unlock_irqrestore(&kvm->irqfds.lock, iflags);
+	}
+
+	return 0;
+}
+
+static void
+irqfd_ptable_queue_proc(struct file *file, wait_queue_head_t *wqh,
+			poll_table *pt)
+{
+	struct kvm_kernel_irqfd *irqfd =
+		container_of(pt, struct kvm_kernel_irqfd, pt);
+	add_wait_queue(wqh, &irqfd->wait);
+}
+
+/* Must be called under irqfds.lock */
+static void irqfd_update(struct kvm *kvm, struct kvm_kernel_irqfd *irqfd)
+{
+	struct kvm_kernel_irq_routing_entry *e;
+	struct kvm_kernel_irq_routing_entry entries[KVM_NR_IRQCHIPS];
+	int n_entries;
+
+	n_entries = kvm_irq_map_gsi(kvm, entries, irqfd->gsi);
+
+	write_seqcount_begin(&irqfd->irq_entry_sc);
+
+	e = entries;
+	if (n_entries == 1)
+		irqfd->irq_entry = *e;
+	else
+		irqfd->irq_entry.type = 0;
+
+	write_seqcount_end(&irqfd->irq_entry_sc);
+}
+
+#ifdef CONFIG_HAVE_KVM_IRQ_BYPASS
+void __attribute__((weak)) kvm_arch_irq_bypass_stop(
+				struct irq_bypass_consumer *cons)
+{
+}
+
+void __attribute__((weak)) kvm_arch_irq_bypass_start(
+				struct irq_bypass_consumer *cons)
+{
+}
+
+int  __attribute__((weak)) kvm_arch_update_irqfd_routing(
+				struct kvm *kvm, unsigned int host_irq,
+				uint32_t guest_irq, bool set)
+{
+	return 0;
+}
+#endif
+
+static int
+kvm_irqfd_assign(struct kvm *kvm, struct kvm_irqfd *args)
+{
+	struct kvm_kernel_irqfd *irqfd, *tmp;
+	struct fd f;
+	struct eventfd_ctx *eventfd = NULL, *resamplefd = NULL;
+	int ret;
+	__poll_t events;
+	int idx;
+
+	if (!kvm_arch_intc_initialized(kvm))
+		return -EAGAIN;
+
+	if (!kvm_arch_irqfd_allowed(kvm, args))
+		return -EINVAL;
+
+	irqfd = kzalloc(sizeof(*irqfd), GFP_KERNEL_ACCOUNT);
+	if (!irqfd)
+		return -ENOMEM;
+
+	irqfd->kvm = kvm;
+	irqfd->gsi = args->gsi;
+	INIT_LIST_HEAD(&irqfd->list);
+	INIT_WORK(&irqfd->inject, irqfd_inject);
+	INIT_WORK(&irqfd->shutdown, irqfd_shutdown);
+	seqcount_spinlock_init(&irqfd->irq_entry_sc, &kvm->irqfds.lock);
+
+	f = fdget(args->fd);
+	if (!f.file) {
+		ret = -EBADF;
+		goto out;
+	}
+
+	eventfd = eventfd_ctx_fileget(f.file);
+	if (IS_ERR(eventfd)) {
+		ret = PTR_ERR(eventfd);
+		goto fail;
+	}
+
+	irqfd->eventfd = eventfd;
+
+	if (args->flags & KVM_IRQFD_FLAG_RESAMPLE) {
+		struct kvm_kernel_irqfd_resampler *resampler;
+
+		resamplefd = eventfd_ctx_fdget(args->resamplefd);
+		if (IS_ERR(resamplefd)) {
+			ret = PTR_ERR(resamplefd);
+			goto fail;
+		}
+
+		irqfd->resamplefd = resamplefd;
+		INIT_LIST_HEAD(&irqfd->resampler_link);
+
+		mutex_lock(&kvm->irqfds.resampler_lock);
+
+		list_for_each_entry(resampler,
+				    &kvm->irqfds.resampler_list, link) {
+			if (resampler->notifier.gsi == irqfd->gsi) {
+				irqfd->resampler = resampler;
+				break;
+			}
+		}
+
+		if (!irqfd->resampler) {
+			resampler = kzalloc(sizeof(*resampler),
+					    GFP_KERNEL_ACCOUNT);
+			if (!resampler) {
+				ret = -ENOMEM;
+				mutex_unlock(&kvm->irqfds.resampler_lock);
+				goto fail;
+			}
+
+			resampler->kvm = kvm;
+			INIT_LIST_HEAD(&resampler->list);
+			resampler->notifier.gsi = irqfd->gsi;
+			resampler->notifier.irq_acked = irqfd_resampler_ack;
+			INIT_LIST_HEAD(&resampler->link);
+
+			list_add(&resampler->link, &kvm->irqfds.resampler_list);
+			kvm_register_irq_ack_notifier(kvm,
+						      &resampler->notifier);
+			irqfd->resampler = resampler;
+		}
+
+		list_add_rcu(&irqfd->resampler_link, &irqfd->resampler->list);
+		synchronize_srcu(&kvm->irq_srcu);
+
+		mutex_unlock(&kvm->irqfds.resampler_lock);
+	}
+
+	/*
+	 * Install our own custom wake-up handling so we are notified via
+	 * a callback whenever someone signals the underlying eventfd
+	 */
+	init_waitqueue_func_entry(&irqfd->wait, irqfd_wakeup);
+	init_poll_funcptr(&irqfd->pt, irqfd_ptable_queue_proc);
+
+	spin_lock_irq(&kvm->irqfds.lock);
+
+	ret = 0;
+	list_for_each_entry(tmp, &kvm->irqfds.items, list) {
+		if (irqfd->eventfd != tmp->eventfd)
+			continue;
+		/* This fd is used for another irq already. */
+		ret = -EBUSY;
+		spin_unlock_irq(&kvm->irqfds.lock);
+		goto fail;
+	}
+
+	idx = srcu_read_lock(&kvm->irq_srcu);
+	irqfd_update(kvm, irqfd);
+
+	list_add_tail(&irqfd->list, &kvm->irqfds.items);
+
+	spin_unlock_irq(&kvm->irqfds.lock);
+
+	/*
+	 * Check if there was an event already pending on the eventfd
+	 * before we registered, and trigger it as if we didn't miss it.
+	 */
+	events = vfs_poll(f.file, &irqfd->pt);
+
+	if (events & EPOLLIN)
+		schedule_work(&irqfd->inject);
+
+#ifdef 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);
+		if (ret)
+			pr_info("irq bypass consumer (token %p) registration fails: %d\n",
+				irqfd->consumer.token, ret);
+	}
+#endif
+
+	srcu_read_unlock(&kvm->irq_srcu, idx);
+
+	/*
+	 * do not drop the file until the irqfd is fully initialized, otherwise
+	 * we might race against the EPOLLHUP
+	 */
+	fdput(f);
+	return 0;
+
+fail:
+	if (irqfd->resampler)
+		irqfd_resampler_shutdown(irqfd);
+
+	if (resamplefd && !IS_ERR(resamplefd))
+		eventfd_ctx_put(resamplefd);
+
+	if (eventfd && !IS_ERR(eventfd))
+		eventfd_ctx_put(eventfd);
+
+	fdput(f);
+
+out:
+	kfree(irqfd);
+	return ret;
+}
+
+bool kvm_irq_has_notifier(struct kvm *kvm, unsigned irqchip, unsigned pin)
+{
+	struct kvm_irq_ack_notifier *kian;
+	int gsi, idx;
+
+	idx = srcu_read_lock(&kvm->irq_srcu);
+	gsi = kvm_irq_map_chip_pin(kvm, irqchip, pin);
+	if (gsi != -1)
+		hlist_for_each_entry_srcu(kian, &kvm->irq_ack_notifier_list,
+					  link, srcu_read_lock_held(&kvm->irq_srcu))
+			if (kian->gsi == gsi) {
+				srcu_read_unlock(&kvm->irq_srcu, idx);
+				return true;
+			}
+
+	srcu_read_unlock(&kvm->irq_srcu, idx);
+
+	return false;
+}
+EXPORT_SYMBOL_GPL(kvm_irq_has_notifier);
+
+void kvm_notify_acked_gsi(struct kvm *kvm, int gsi)
+{
+	struct kvm_irq_ack_notifier *kian;
+
+	hlist_for_each_entry_srcu(kian, &kvm->irq_ack_notifier_list,
+				  link, srcu_read_lock_held(&kvm->irq_srcu))
+		if (kian->gsi == gsi)
+			kian->irq_acked(kian);
+}
+
+void kvm_notify_acked_irq(struct kvm *kvm, unsigned irqchip, unsigned pin)
+{
+	int gsi, idx;
+
+	trace_kvm_ack_irq(irqchip, pin);
+
+	idx = srcu_read_lock(&kvm->irq_srcu);
+	gsi = kvm_irq_map_chip_pin(kvm, irqchip, pin);
+	if (gsi != -1)
+		kvm_notify_acked_gsi(kvm, gsi);
+	srcu_read_unlock(&kvm->irq_srcu, idx);
+}
+
+void kvm_register_irq_ack_notifier(struct kvm *kvm,
+				   struct kvm_irq_ack_notifier *kian)
+{
+	mutex_lock(&kvm->irq_lock);
+	hlist_add_head_rcu(&kian->link, &kvm->irq_ack_notifier_list);
+	mutex_unlock(&kvm->irq_lock);
+	kvm_arch_post_irq_ack_notifier_list_update(kvm);
+}
+
+void kvm_unregister_irq_ack_notifier(struct kvm *kvm,
+				    struct kvm_irq_ack_notifier *kian)
+{
+	mutex_lock(&kvm->irq_lock);
+	hlist_del_init_rcu(&kian->link);
+	mutex_unlock(&kvm->irq_lock);
+	synchronize_srcu(&kvm->irq_srcu);
+	kvm_arch_post_irq_ack_notifier_list_update(kvm);
+}
+#endif
+
+void
+kvm_eventfd_init(struct kvm *kvm)
+{
+#ifdef CONFIG_HAVE_KVM_IRQFD
+	spin_lock_init(&kvm->irqfds.lock);
+	INIT_LIST_HEAD(&kvm->irqfds.items);
+	INIT_LIST_HEAD(&kvm->irqfds.resampler_list);
+	mutex_init(&kvm->irqfds.resampler_lock);
+#endif
+	INIT_LIST_HEAD(&kvm->ioeventfds);
+}
+
+#ifdef CONFIG_HAVE_KVM_IRQFD
+/*
+ * shutdown any irqfd's that match fd+gsi
+ */
+static int
+kvm_irqfd_deassign(struct kvm *kvm, struct kvm_irqfd *args)
+{
+	struct kvm_kernel_irqfd *irqfd, *tmp;
+	struct eventfd_ctx *eventfd;
+
+	eventfd = eventfd_ctx_fdget(args->fd);
+	if (IS_ERR(eventfd))
+		return PTR_ERR(eventfd);
+
+	spin_lock_irq(&kvm->irqfds.lock);
+
+	list_for_each_entry_safe(irqfd, tmp, &kvm->irqfds.items, list) {
+		if (irqfd->eventfd == eventfd && irqfd->gsi == args->gsi) {
+			/*
+			 * This clearing of irq_entry.type is needed for when
+			 * another thread calls kvm_irq_routing_update before
+			 * we flush workqueue below (we synchronize with
+			 * kvm_irq_routing_update using irqfds.lock).
+			 */
+			write_seqcount_begin(&irqfd->irq_entry_sc);
+			irqfd->irq_entry.type = 0;
+			write_seqcount_end(&irqfd->irq_entry_sc);
+			irqfd_deactivate(irqfd);
+		}
+	}
+
+	spin_unlock_irq(&kvm->irqfds.lock);
+	eventfd_ctx_put(eventfd);
+
+	/*
+	 * Block until we know all outstanding shutdown jobs have completed
+	 * so that we guarantee there will not be any more interrupts on this
+	 * gsi once this deassign function returns.
+	 */
+	flush_workqueue(irqfd_cleanup_wq);
+
+	return 0;
+}
+
+int
+kvm_irqfd(struct kvm *kvm, struct kvm_irqfd *args)
+{
+	if (args->flags & ~(KVM_IRQFD_FLAG_DEASSIGN | KVM_IRQFD_FLAG_RESAMPLE))
+		return -EINVAL;
+
+	if (args->flags & KVM_IRQFD_FLAG_DEASSIGN)
+		return kvm_irqfd_deassign(kvm, args);
+
+	return kvm_irqfd_assign(kvm, args);
+}
+
+/*
+ * This function is called as the kvm VM fd is being released. Shutdown all
+ * irqfds that still remain open
+ */
+void
+kvm_irqfd_release(struct kvm *kvm)
+{
+	struct kvm_kernel_irqfd *irqfd, *tmp;
+
+	spin_lock_irq(&kvm->irqfds.lock);
+
+	list_for_each_entry_safe(irqfd, tmp, &kvm->irqfds.items, list)
+		irqfd_deactivate(irqfd);
+
+	spin_unlock_irq(&kvm->irqfds.lock);
+
+	/*
+	 * Block until we know all outstanding shutdown jobs have completed
+	 * since we do not take a kvm* reference.
+	 */
+	flush_workqueue(irqfd_cleanup_wq);
+
+}
+
+/*
+ * Take note of a change in irq routing.
+ * Caller must invoke synchronize_srcu(&kvm->irq_srcu) afterwards.
+ */
+void kvm_irq_routing_update(struct kvm *kvm)
+{
+	struct kvm_kernel_irqfd *irqfd;
+
+	spin_lock_irq(&kvm->irqfds.lock);
+
+	list_for_each_entry(irqfd, &kvm->irqfds.items, list) {
+		irqfd_update(kvm, irqfd);
+
+#ifdef CONFIG_HAVE_KVM_IRQ_BYPASS
+		if (irqfd->producer) {
+			int ret = kvm_arch_update_irqfd_routing(
+					irqfd->kvm, irqfd->producer->irq,
+					irqfd->gsi, 1);
+			WARN_ON(ret);
+		}
+#endif
+	}
+
+	spin_unlock_irq(&kvm->irqfds.lock);
+}
+
+/*
+ * create a host-wide workqueue for issuing deferred shutdown requests
+ * aggregated from all vm* instances. We need our own isolated
+ * queue to ease flushing work items when a VM exits.
+ */
+int kvm_irqfd_init(void)
+{
+	irqfd_cleanup_wq = alloc_workqueue("kvm-irqfd-cleanup", 0, 0);
+	if (!irqfd_cleanup_wq)
+		return -ENOMEM;
+
+	return 0;
+}
+
+void kvm_irqfd_exit(void)
+{
+	destroy_workqueue(irqfd_cleanup_wq);
+}
+#endif
+
+/*
+ * --------------------------------------------------------------------
+ * ioeventfd: translate a PIO/MMIO memory write to an eventfd signal.
+ *
+ * userspace can register a PIO/MMIO address with an eventfd for receiving
+ * notification when the memory has been touched.
+ * --------------------------------------------------------------------
+ */
+
+struct _ioeventfd {
+	struct list_head     list;
+	u64                  addr;
+	int                  length;
+	struct eventfd_ctx  *eventfd;
+	u64                  datamatch;
+	struct kvm_io_device dev;
+	u8                   bus_idx;
+	bool                 wildcard;
+};
+
+static inline struct _ioeventfd *
+to_ioeventfd(struct kvm_io_device *dev)
+{
+	return container_of(dev, struct _ioeventfd, dev);
+}
+
+static void
+ioeventfd_release(struct _ioeventfd *p)
+{
+	eventfd_ctx_put(p->eventfd);
+	list_del(&p->list);
+	kfree(p);
+}
+
+static bool
+ioeventfd_in_range(struct _ioeventfd *p, gpa_t addr, int len, const void *val)
+{
+	u64 _val;
+
+	if (addr != p->addr)
+		/* address must be precise for a hit */
+		return false;
+
+	if (!p->length)
+		/* length = 0 means only look at the address, so always a hit */
+		return true;
+
+	if (len != p->length)
+		/* address-range must be precise for a hit */
+		return false;
+
+	if (p->wildcard)
+		/* all else equal, wildcard is always a hit */
+		return true;
+
+	/* otherwise, we have to actually compare the data */
+
+	BUG_ON(!IS_ALIGNED((unsigned long)val, len));
+
+	switch (len) {
+	case 1:
+		_val = *(u8 *)val;
+		break;
+	case 2:
+		_val = *(u16 *)val;
+		break;
+	case 4:
+		_val = *(u32 *)val;
+		break;
+	case 8:
+		_val = *(u64 *)val;
+		break;
+	default:
+		return false;
+	}
+
+	return _val == p->datamatch;
+}
+
+/* MMIO/PIO writes trigger an event if the addr/val match */
+static int
+ioeventfd_write(struct kvm_vcpu *vcpu, struct kvm_io_device *this, gpa_t addr,
+		int len, const void *val)
+{
+	struct _ioeventfd *p = to_ioeventfd(this);
+
+	if (!ioeventfd_in_range(p, addr, len, val))
+		return -EOPNOTSUPP;
+
+	eventfd_signal(p->eventfd, 1);
+	return 0;
+}
+
+/*
+ * This function is called as KVM is completely shutting down.  We do not
+ * need to worry about locking just nuke anything we have as quickly as possible
+ */
+static void
+ioeventfd_destructor(struct kvm_io_device *this)
+{
+	struct _ioeventfd *p = to_ioeventfd(this);
+
+	ioeventfd_release(p);
+}
+
+static const struct kvm_io_device_ops ioeventfd_ops = {
+	.write      = ioeventfd_write,
+	.destructor = ioeventfd_destructor,
+};
+
+/* assumes kvm->slots_lock held */
+static bool
+ioeventfd_check_collision(struct kvm *kvm, struct _ioeventfd *p)
+{
+	struct _ioeventfd *_p;
+
+	list_for_each_entry(_p, &kvm->ioeventfds, list)
+		if (_p->bus_idx == p->bus_idx &&
+		    _p->addr == p->addr &&
+		    (!_p->length || !p->length ||
+		     (_p->length == p->length &&
+		      (_p->wildcard || p->wildcard ||
+		       _p->datamatch == p->datamatch))))
+			return true;
+
+	return false;
+}
+
+static enum kvm_bus ioeventfd_bus_from_flags(__u32 flags)
+{
+	if (flags & KVM_IOEVENTFD_FLAG_PIO)
+		return KVM_PIO_BUS;
+	if (flags & KVM_IOEVENTFD_FLAG_VIRTIO_CCW_NOTIFY)
+		return KVM_VIRTIO_CCW_NOTIFY_BUS;
+	return KVM_MMIO_BUS;
+}
+
+static int kvm_assign_ioeventfd_idx(struct kvm *kvm,
+				enum kvm_bus bus_idx,
+				struct kvm_ioeventfd *args)
+{
+
+	struct eventfd_ctx *eventfd;
+	struct _ioeventfd *p;
+	int ret;
+
+	eventfd = eventfd_ctx_fdget(args->fd);
+	if (IS_ERR(eventfd))
+		return PTR_ERR(eventfd);
+
+	p = kzalloc(sizeof(*p), GFP_KERNEL_ACCOUNT);
+	if (!p) {
+		ret = -ENOMEM;
+		goto fail;
+	}
+
+	INIT_LIST_HEAD(&p->list);
+	p->addr    = args->addr;
+	p->bus_idx = bus_idx;
+	p->length  = args->len;
+	p->eventfd = eventfd;
+
+	/* The datamatch feature is optional, otherwise this is a wildcard */
+	if (args->flags & KVM_IOEVENTFD_FLAG_DATAMATCH)
+		p->datamatch = args->datamatch;
+	else
+		p->wildcard = true;
+
+	mutex_lock(&kvm->slots_lock);
+
+	/* Verify that there isn't a match already */
+	if (ioeventfd_check_collision(kvm, p)) {
+		ret = -EEXIST;
+		goto unlock_fail;
+	}
+
+	kvm_iodevice_init(&p->dev, &ioeventfd_ops);
+
+	ret = kvm_io_bus_register_dev(kvm, bus_idx, p->addr, p->length,
+				      &p->dev);
+	if (ret < 0)
+		goto unlock_fail;
+
+	kvm_get_bus(kvm, bus_idx)->ioeventfd_count++;
+	list_add_tail(&p->list, &kvm->ioeventfds);
+
+	mutex_unlock(&kvm->slots_lock);
+
+	return 0;
+
+unlock_fail:
+	mutex_unlock(&kvm->slots_lock);
+
+fail:
+	kfree(p);
+	eventfd_ctx_put(eventfd);
+
+	return ret;
+}
+
+static int
+kvm_deassign_ioeventfd_idx(struct kvm *kvm, enum kvm_bus bus_idx,
+			   struct kvm_ioeventfd *args)
+{
+	struct _ioeventfd        *p, *tmp;
+	struct eventfd_ctx       *eventfd;
+	struct kvm_io_bus	 *bus;
+	int                       ret = -ENOENT;
+	bool                      wildcard;
+
+	eventfd = eventfd_ctx_fdget(args->fd);
+	if (IS_ERR(eventfd))
+		return PTR_ERR(eventfd);
+
+	wildcard = !(args->flags & KVM_IOEVENTFD_FLAG_DATAMATCH);
+
+	mutex_lock(&kvm->slots_lock);
+
+	list_for_each_entry_safe(p, tmp, &kvm->ioeventfds, list) {
+
+		if (p->bus_idx != bus_idx ||
+		    p->eventfd != eventfd  ||
+		    p->addr != args->addr  ||
+		    p->length != args->len ||
+		    p->wildcard != wildcard)
+			continue;
+
+		if (!p->wildcard && p->datamatch != args->datamatch)
+			continue;
+
+		kvm_io_bus_unregister_dev(kvm, bus_idx, &p->dev);
+		bus = kvm_get_bus(kvm, bus_idx);
+		if (bus)
+			bus->ioeventfd_count--;
+		ioeventfd_release(p);
+		ret = 0;
+		break;
+	}
+
+	mutex_unlock(&kvm->slots_lock);
+
+	eventfd_ctx_put(eventfd);
+
+	return ret;
+}
+
+static int kvm_deassign_ioeventfd(struct kvm *kvm, struct kvm_ioeventfd *args)
+{
+	enum kvm_bus bus_idx = ioeventfd_bus_from_flags(args->flags);
+	int ret = kvm_deassign_ioeventfd_idx(kvm, bus_idx, args);
+
+	if (!args->len && bus_idx == KVM_MMIO_BUS)
+		kvm_deassign_ioeventfd_idx(kvm, KVM_FAST_MMIO_BUS, args);
+
+	return ret;
+}
+
+static int
+kvm_assign_ioeventfd(struct kvm *kvm, struct kvm_ioeventfd *args)
+{
+	enum kvm_bus              bus_idx;
+	int ret;
+
+	bus_idx = ioeventfd_bus_from_flags(args->flags);
+	/* must be natural-word sized, or 0 to ignore length */
+	switch (args->len) {
+	case 0:
+	case 1:
+	case 2:
+	case 4:
+	case 8:
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	/* check for range overflow */
+	if (args->addr + args->len < args->addr)
+		return -EINVAL;
+
+	/* check for extra flags that we don't understand */
+	if (args->flags & ~KVM_IOEVENTFD_VALID_FLAG_MASK)
+		return -EINVAL;
+
+	/* ioeventfd with no length can't be combined with DATAMATCH */
+	if (!args->len && (args->flags & KVM_IOEVENTFD_FLAG_DATAMATCH))
+		return -EINVAL;
+
+	ret = kvm_assign_ioeventfd_idx(kvm, bus_idx, args);
+	if (ret)
+		goto fail;
+
+	/* When length is ignored, MMIO is also put on a separate bus, for
+	 * faster lookups.
+	 */
+	if (!args->len && bus_idx == KVM_MMIO_BUS) {
+		ret = kvm_assign_ioeventfd_idx(kvm, KVM_FAST_MMIO_BUS, args);
+		if (ret < 0)
+			goto fast_fail;
+	}
+
+	return 0;
+
+fast_fail:
+	kvm_deassign_ioeventfd_idx(kvm, bus_idx, args);
+fail:
+	return ret;
+}
+
+int
+kvm_ioeventfd(struct kvm *kvm, struct kvm_ioeventfd *args)
+{
+	if (args->flags & KVM_IOEVENTFD_FLAG_DEASSIGN)
+		return kvm_deassign_ioeventfd(kvm, args);
+
+	return kvm_assign_ioeventfd(kvm, args);
+}