/*
* kvm eventfd support - use eventfd objects to signal various KVM events
*
* Copyright 2009 Novell. All Rights Reserved.
*
* 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/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>
/*
* --------------------------------------------------------------------
* irqfd: Allows an fd to be used to inject an interrupt to the guest
*
* Credit goes to Avi Kivity for the original idea.
* --------------------------------------------------------------------
*/
struct _irqfd {
struct kvm *kvm;
struct eventfd_ctx *eventfd;
int gsi;
struct list_head list;
poll_table pt;
wait_queue_head_t *wqh;
wait_queue_t wait;
struct work_struct inject;
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;
mutex_lock(&kvm->lock);
kvm_set_irq(kvm, KVM_USERSPACE_IRQ_SOURCE_ID, irqfd->gsi, 1);
kvm_set_irq(kvm, KVM_USERSPACE_IRQ_SOURCE_ID, irqfd->gsi, 0);
mutex_unlock(&kvm->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);
/*
* Synchronize with the wait-queue and unhook ourselves to prevent
* further events.
*/
remove_wait_queue(irqfd->wqh, &irqfd->wait);
/*
* We know no new events will be scheduled at this point, so block
* until all previously outstanding events have completed
*/
flush_work(&irqfd->inject);
/*
* 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;
if (flags & POLLIN)
/* An event has been signaled, inject an interrupt */
schedule_work(&irqfd->inject);
if (flags & POLLHUP) {
/* The eventfd is closing, detach from KVM */
struct kvm *kvm = irqfd->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);
irqfd->wqh = wqh;
add_wait_queue(wqh, &irqfd->wait);
}
static int
kvm_irqfd_assign(struct kvm *kvm, int fd, int gsi)
{
struct _irqfd *irqfd;
struct file *file = NULL;
struct eventfd_ctx *eventfd = NULL;
int ret;
unsigned int events;
irqfd = kzalloc(sizeof(*irqfd), GFP_KERNEL);
if (!irqfd)
return -ENOMEM;
irqfd->kvm = kvm;
irqfd->gsi = gsi;
INIT_LIST_HEAD(&irqfd->list);
INIT_WORK(&irqfd->inject, irqfd_inject);
INIT_WORK(&irqfd->shutdown, irqfd_shutdown);
file = eventfd_fget(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;
/*
* 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);
events = file->f_op->poll(file, &irqfd->pt);
spin_lock_irq(&kvm->irqfds.lock);
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.
*/
if (events & POLLIN)
schedule_work(&irqfd->inject);
/*
* do not drop the file until the irqfd is fully initialized, otherwise
* we might race against the POLLHUP
*/
fput(file);
return 0;
fail:
if (eventfd && !IS_ERR(eventfd))
eventfd_ctx_put(eventfd);
if (file && !IS_ERR(file))
fput(file);
kfree(irqfd);
return ret;
}
void
kvm_irqfd_init(struct kvm *kvm)
{
spin_lock_init(&kvm->irqfds.lock);
INIT_LIST_HEAD(&kvm->irqfds.items);
}
/*
* shutdown any irqfd's that match fd+gsi
*/
static int
kvm_irqfd_deassign(struct kvm *kvm, int fd, int gsi)
{
struct _irqfd *irqfd, *tmp;
struct eventfd_ctx *eventfd;
eventfd = eventfd_ctx_fdget(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 == gsi)
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, int fd, int gsi, int flags)
{
if (flags & KVM_IRQFD_FLAG_DEASSIGN)
return kvm_irqfd_deassign(kvm, fd, gsi);
return kvm_irqfd_assign(kvm, fd, gsi);
}
/*
* 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);
}
/*
* 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);
