linux/virt/kvm/eventfd.c
Ahmed S. Darwish 5c73b9a2b1 kvm/eventfd: Use sequence counter with associated spinlock
A sequence counter write side critical section must be protected by some
form of locking to serialize writers. A plain seqcount_t does not
contain the information of which lock must be held when entering a write
side critical section.

Use the new seqcount_spinlock_t data type, which allows to associate a
spinlock with the sequence counter. This enables lockdep to verify that
the spinlock used for writer serialization is held when the write side
critical section is entered.

If lockdep is disabled this lock association is compiled out and has
neither storage size nor runtime overhead.

Signed-off-by: Ahmed S. Darwish <a.darwish@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Link: https://lkml.kernel.org/r/20200720155530.1173732-24-a.darwish@linutronix.de
2020-07-29 16:14:29 +02:00

963 lines
22 KiB
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_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_rcu(kian, &kvm->irq_ack_notifier_list,
link)
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_rcu(kian, &kvm->irq_ack_notifier_list,
link)
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;
eventfd = eventfd_ctx_fdget(args->fd);
if (IS_ERR(eventfd))
return PTR_ERR(eventfd);
mutex_lock(&kvm->slots_lock);
list_for_each_entry_safe(p, tmp, &kvm->ioeventfds, list) {
bool wildcard = !(args->flags & KVM_IOEVENTFD_FLAG_DATAMATCH);
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);
}