path: root/virt/kvm/eventfd.c

// 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_IRQCHIP

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);
}

static void irqfd_resampler_notify(struct kvm_kernel_irqfd_resampler *resampler)
{
	struct kvm_kernel_irqfd *irqfd;

	list_for_each_entry_srcu(irqfd, &resampler->list, resampler_link,
				 srcu_read_lock_held(&resampler->kvm->irq_srcu))
		eventfd_signal(irqfd->resamplefd);
}

/*
 * 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;
	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);
	irqfd_resampler_notify(resampler);
	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);

	if (list_empty(&resampler->list)) {
		list_del_rcu(&resampler->link);
		kvm_unregister_irq_ack_notifier(kvm, &resampler->notifier);
		/*
		 * synchronize_srcu_expedited(&kvm->irq_srcu) already called
		 * in kvm_unregister_irq_ack_notifier().
		 */
		kvm_set_irq(kvm, KVM_IRQFD_RESAMPLE_IRQ_SOURCE_ID,
			    resampler->notifier.gsi, 0, false);
		kfree(resampler);
	} else {
		synchronize_srcu_expedited(&kvm->irq_srcu);
	}

	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_expedited(&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
	 */
#if IS_ENABLED(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