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authorGregory Haskins <ghaskins@novell.com>2009-05-20 10:30:49 -0400
committerAvi Kivity <avi@redhat.com>2009-09-10 08:32:41 +0300
commit721eecbf4fe995ca94a9edec0c9843b1cc0eaaf3 (patch)
treec759fe98a4ea5e2e2a7694e4b44a558407077290 /virt/kvm/eventfd.c
parent0ba12d10817a8db1fd7d96d3283ec6c0b294aeab (diff)
downloadlinux-721eecbf4fe995ca94a9edec0c9843b1cc0eaaf3.tar.gz
KVM: irqfd
KVM provides a complete virtual system environment for guests, including support for injecting interrupts modeled after the real exception/interrupt facilities present on the native platform (such as the IDT on x86). Virtual interrupts can come from a variety of sources (emulated devices, pass-through devices, etc) but all must be injected to the guest via the KVM infrastructure. This patch adds a new mechanism to inject a specific interrupt to a guest using a decoupled eventfd mechnanism: Any legal signal on the irqfd (using eventfd semantics from either userspace or kernel) will translate into an injected interrupt in the guest at the next available interrupt window. Signed-off-by: Gregory Haskins <ghaskins@novell.com> Signed-off-by: Avi Kivity <avi@redhat.com>
Diffstat (limited to 'virt/kvm/eventfd.c')
-rw-r--r--virt/kvm/eventfd.c329
1 files changed, 329 insertions, 0 deletions
diff --git a/virt/kvm/eventfd.c b/virt/kvm/eventfd.c
new file mode 100644
index 00000000000..314012323af
--- /dev/null
+++ b/virt/kvm/eventfd.c
@@ -0,0 +1,329 @@
+/*
+ * 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);