/*
* 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>
*
* This file is free software; you can redistribute it and/or modify
* it under the terms of version 2 of the GNU General Public License
* as published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA.
*/
#include <linux/kvm_host.h>
#include <linux/kvm.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/slab.h>
#include "iodev.h"
#ifdef __KVM_HAVE_IOAPIC
/*
* --------------------------------------------------------------------
* irqfd: Allows an fd to be used to inject an interrupt to the guest
*
* Credit goes to Avi Kivity for the original idea.
* --------------------------------------------------------------------
*/
/*
* Resampling irqfds are a special variety of irqfds used to emulate
* level triggered interrupts. The interrupt is asserted on eventfd
* trigger. On acknowledgement through the irq ack notifier, the
* interrupt is de-asserted and userspace is notified through the
* resamplefd. All resamplers on the same gsi are de-asserted
* together, so we don't need to track the state of each individual
* user. We can also therefore share the same irq source ID.
*/
struct _irqfd_resampler {
struct kvm *kvm;
/*
* List of resampling struct _irqfd objects sharing this gsi.
* RCU list modified under kvm->irqfds.resampler_lock
*/
struct list_head list;
struct kvm_irq_ack_notifier notifier;
/*
* Entry in list of kvm->irqfd.resampler_list. Use for sharing
* resamplers among irqfds on the same gsi.
* Accessed and modified under kvm->irqfds.resampler_lock
*/
struct list_head link;
};
struct _irqfd {
/* Used for MSI fast-path */
struct kvm *kvm;
wait_queue_t wait;
/* Update side is protected by irqfds.lock */
struct kvm_kernel_irq_routing_entry __rcu *irq_entry;
/* Used for level IRQ fast-path */
int gsi;
struct work_struct inject;
/* The resampler used by this irqfd (resampler-only) */
struct _irqfd_resampler *resampler;
/* Eventfd notified on resample (resampler-only) */
struct eventfd_ctx *resamplefd;
/* Entry in list of irqfds for a resampler (resampler-only) */
struct list_head resampler_link;
/* Used for setup/shutdown */
struct eventfd_ctx *eventfd;
struct list_head list;
poll_table pt;
struct work_struct shutdown;
};
static struct workqueue_struct *irqfd_cleanup_wq;
static void
irqfd_inject(struct work_struct *work)
{
struct _irqfd *irqfd = container_of(work, struct _irqfd, inject);
struct kvm *kvm = irqfd->kvm;
if (!irqfd->resampler) {
kvm_set_irq(kvm, KVM_USERSPACE_IRQ_SOURCE_ID, irqfd->gsi, 1);
kvm_set_irq(kvm, KVM_USERSPACE_IRQ_SOURCE_ID, irqfd->gsi, 0);
} else
kvm_set_irq(kvm, KVM_IRQFD_RESAMPLE_IRQ_SOURCE_ID,
irqfd->gsi, 1);
}
/*
* 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 _irqfd_resampler *resampler;
struct _irqfd *irqfd;
resampler = container_of(kian, struct _irqfd_resampler, notifier);
kvm_set_irq(resampler->kvm, KVM_IRQFD_RESAMPLE_IRQ_SOURCE_ID,
resampler->notifier.gsi, 0);
rcu_read_lock();
list_for_each_entry_rcu(irqfd, &resampler->list, resampler_link)
eventfd_signal(irqfd->resamplefd, 1);
rcu_read_unlock();
}
static void
irqfd_resampler_shutdown(struct _irqfd *irqfd)
{
struct _irqfd_resampler *resampler = irqfd->resampler;
struct kvm *kvm = resampler->kvm;
mutex_lock(&kvm->irqfds.resampler_lock);
list_del_rcu(&irqfd->resampler_link);
synchronize_rcu();
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);
kfree(resampler);
}
mutex_unlock(&kvm->irqfds.resampler_lock);
}
/*
* Race-free decouple logic (ordering is critical)
*/
static void
irqfd_shutdown(struct work_struct *work)
{
struct _irqfd *irqfd = container_of(work, struct _irqfd, shutdown);
u64 cnt;
/*
* 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
*/
eventfd_ctx_put(irqfd->eventfd);
kfree(irqfd);
}
/* assumes kvm->irqfds.lock is held */
static bool
irqfd_is_active(struct _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 _irqfd *irqfd)
{
BUG_ON(!irqfd_is_active(irqfd));
list_del_init(&irqfd->list);
queue_work(irqfd_cleanup_wq, &irqfd->shutdown);
}
/*
* Called with wqh->lock held and interrupts disabled
*/
static int
irqfd_wakeup(wait_queue_t *wait, unsigned mode, int sync, void *key)
{
struct _irqfd *irqfd = container_of(wait, struct _irqfd, wait);
unsigned long flags = (unsigned long)key;
struct kvm_kernel_irq_routing_entry *irq;
struct kvm *kvm = irqfd->kvm;
if (flags & POLLIN) {
rcu_read_lock();
irq = rcu_dereference(irqfd->irq_entry);
/* An event has been signaled, inject an interrupt */
if (irq)
kvm_set_msi(irq, kvm, KVM_USERSPACE_IRQ_SOURCE_ID, 1);
else
schedule_work(&irqfd->inject);
rcu_read_unlock();
}
if (flags & POLLHUP) {
/* The eventfd is closing, detach from KVM */
unsigned long flags;
spin_lock_irqsave(&kvm->irqfds.lock, flags);
/*
* 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, flags);
}
return 0;
}
static void
irqfd_ptable_queue_proc(struct file *file, wait_queue_head_t *wqh,
poll_table *pt)
{
struct _irqfd *irqfd = container_of(pt, struct _irqfd, pt);
add_wait_queue(wqh, &irqfd->wait);
}
/* Must be called under irqfds.lock */
static void irqfd_update(struct kvm *kvm, struct _irqfd *irqfd,
struct kvm_irq_routing_table *irq_rt)
{
struct kvm_kernel_irq_routing_entry *e;
struct hlist_node *n;
if (irqfd->gsi >= irq_rt->nr_rt_entries) {
rcu_assign_pointer(irqfd->irq_entry, NULL);
return;
}
hlist_for_each_entry(e, n, &irq_rt->map[irqfd->gsi], link) {
/* Only fast-path MSI. */
if (e->type == KVM_IRQ_ROUTING_MSI)
rcu_assign_pointer(irqfd->irq_entry, e);
else
rcu_assign_pointer(irqfd->irq_entry, NULL);
}
}
static int
kvm_irqfd_assign(struct kvm *kvm, struct kvm_irqfd *args)
{
struct kvm_irq_routing_table *irq_rt;
struct _irqfd *irqfd, *tmp;
struct file *file = NULL;
struct eventfd_ctx *eventfd = NULL, *resamplefd = NULL;
int ret;
unsigned int events;
irqfd = kzalloc(sizeof(*irqfd), GFP_KERNEL);
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);
file = eventfd_fget(args->fd);
if (IS_ERR(file)) {
ret = PTR_ERR(file);
goto fail;
}
eventfd = eventfd_ctx_fileget(file);
if (IS_ERR(eventfd)) {
ret = PTR_ERR(eventfd);
goto fail;
}
irqfd->eventfd = eventfd;
if (args->flags & KVM_IRQFD_FLAG_RESAMPLE) {
struct _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);
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_rcu();
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;
}
irq_rt = rcu_dereference_protected(kvm->irq_routing,
lockdep_is_held(&kvm->irqfds.lock));
irqfd_update(kvm, irqfd, irq_rt);
events = file->f_op->poll(file, &irqfd->pt);
list_add_tail(&irqfd->list, &kvm->irqfds.items);
/*
* Check if there was an event already pending on the eventfd
* before we registered, and trigger it as if we didn't miss it.
*/
if (events & POLLIN)
schedule_work(&irqfd->inject);
spin_unlock_irq(&kvm->irqfds.lock);
/*
* do not drop the file until the irqfd is fully initialized, otherwise
* we might race against the POLLHUP
*/
fput(file);
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);
if (!IS_ERR(file))
fput(file);
kfree(irqfd);
return ret;
}
#endif
void
kvm_eventfd_init(struct kvm *kvm)
{
#ifdef __KVM_HAVE_IOAPIC
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 __KVM_HAVE_IOAPIC
/*
* shutdown any irqfd's that match fd+gsi
*/
static int
kvm_irqfd_deassign(struct kvm *kvm, struct kvm_irqfd *args)
{
struct _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 rcu_assign_pointer 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).
* It is paired with synchronize_rcu done by caller
* of that function.
*/
rcu_assign_pointer(irqfd->irq_entry, NULL);
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 _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);
}
/*
* Change irq_routing and irqfd.
* Caller must invoke synchronize_rcu afterwards.
*/
void kvm_irq_routing_update(struct kvm *kvm,
struct kvm_irq_routing_table *irq_rt)
{
struct _irqfd *irqfd;
spin_lock_irq(&kvm->irqfds.lock);
rcu_assign_pointer(kvm->irq_routing, irq_rt);
list_for_each_entry(irqfd, &kvm->irqfds.items, list)
irqfd_update(kvm, irqfd, irq_rt);
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 single-thread
* queue to prevent deadlock against flushing the normal work-queue.
*/
static int __init irqfd_module_init(void)
{
irqfd_cleanup_wq = create_singlethread_workqueue("kvm-irqfd-cleanup");
if (!irqfd_cleanup_wq)
return -ENOMEM;
return 0;
}
static void __exit irqfd_module_exit(void)
{
destroy_workqueue(irqfd_cleanup_wq);
}
module_init(irqfd_module_init);
module_exit(irqfd_module_exit);
#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;
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 && 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 ? true : false;
}
/* MMIO/PIO writes trigger an event if the addr/val match */
static int
ioeventfd_write(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->addr == p->addr && _p->length == p->length &&
(_p->wildcard || p->wildcard ||
_p->datamatch == p->datamatch))
return true;
return false;
}
static int
kvm_assign_ioeventfd(struct kvm *kvm, struct kvm_ioeventfd *args)
{
int pio = args->flags & KVM_IOEVENTFD_FLAG_PIO;
enum kvm_bus bus_idx = pio ? KVM_PIO_BUS : KVM_MMIO_BUS;
struct _ioeventfd *p;
struct eventfd_ctx *eventfd;
int ret;
/* must be natural-word sized */
switch (args->len) {
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;
eventfd = eventfd_ctx_fdget(args->fd);
if (IS_ERR(eventfd))
return PTR_ERR(eventfd);
p = kzalloc(sizeof(*p), GFP_KERNEL);
if (!p) {
ret = -ENOMEM;
goto fail;
}
INIT_LIST_HEAD(&p->list);
p->addr = args->addr;
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;
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(struct kvm *kvm, struct kvm_ioeventfd *args)
{
int pio = args->flags & KVM_IOEVENTFD_FLAG_PIO;
enum kvm_bus bus_idx = pio ? KVM_PIO_BUS : KVM_MMIO_BUS;
struct _ioeventfd *p, *tmp;
struct eventfd_ctx *eventfd;
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->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);
ioeventfd_release(p);
ret = 0;
break;
}
mutex_unlock(&kvm->slots_lock);
eventfd_ctx_put(eventfd);
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);
}
