eventfd.c

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// 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);
    synchronize_srcu(&kvm->irq_srcu);
 
    if (list_empty(&resampler->list)) {
        list_del_rcu(&resampler->link);
        kvm_unregister_irq_ack_notifier(kvm, &resampler->notifier);
        /*
         * synchronize_srcu(&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);
    }
 
    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;
    int ret = 0;
 
    if (flags & EPOLLIN) {
        u64 cnt;
        eventfd_ctx_do_read(irqfd->eventfd, &cnt);
 
        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);
        ret = 1;
    }
 
    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 ret;
}
 
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_priority(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;
}
 
bool __attribute__((weak)) kvm_arch_irqfd_route_changed(
                struct kvm_kernel_irq_routing_entry *old,
                struct kvm_kernel_irq_routing_entry *new)
{
    return true;
}
#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_rcu(&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);
}
 
/*
 * 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) {
#ifdef CONFIG_HAVE_KVM_IRQ_BYPASS
        /* Under irqfds.lock, so can read irq_entry safely */
        struct kvm_kernel_irq_routing_entry old = irqfd->irq_entry;
#endif
 
        irqfd_update(kvm, irqfd);
 
#ifdef CONFIG_HAVE_KVM_IRQ_BYPASS
        if (irqfd->producer &&
            kvm_arch_irqfd_route_changed(&old, &irqfd->irq_entry)) {
            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);
}
 
bool kvm_notify_irqfd_resampler(struct kvm *kvm,
                unsigned int irqchip,
                unsigned int pin)
{
    struct kvm_kernel_irqfd_resampler *resampler;
    int gsi, idx;
 
    idx = srcu_read_lock(&kvm->irq_srcu);
    gsi = kvm_irq_map_chip_pin(kvm, irqchip, pin);
    if (gsi != -1) {
        list_for_each_entry_srcu(resampler,
                     &kvm->irqfds.resampler_list, link,
                     srcu_read_lock_held(&kvm->irq_srcu)) {
            if (resampler->notifier.gsi == gsi) {
                irqfd_resampler_notify(resampler);
                srcu_read_unlock(&kvm->irq_srcu, idx);
                return true;
            }
        }
    }
    srcu_read_unlock(&kvm->irq_srcu, idx);
 
    return false;
}
 
/*
 * 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);
    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);
    kfree(p);
 
fail:
    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;
    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(p, &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--;
        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);
}
 
void
kvm_eventfd_init(struct kvm *kvm)
{
#ifdef CONFIG_HAVE_KVM_IRQCHIP
    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);
}