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Subject[PATCH 11/48] KVM: irqfd
Date
From: Gregory Haskins <ghaskins@novell.com>

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>
---
arch/x86/kvm/Kconfig | 1 +
arch/x86/kvm/Makefile | 2 +-
arch/x86/kvm/x86.c | 1 +
include/linux/kvm.h | 11 ++
include/linux/kvm_host.h | 24 ++++
virt/kvm/Kconfig | 4 +
virt/kvm/eventfd.c | 329 ++++++++++++++++++++++++++++++++++++++++++++++
virt/kvm/kvm_main.c | 12 ++
8 files changed, 383 insertions(+), 1 deletions(-)
create mode 100644 virt/kvm/eventfd.c
diff --git a/arch/x86/kvm/Kconfig b/arch/x86/kvm/Kconfig
index 939b1cb..8cd2a4e 100644
--- a/arch/x86/kvm/Kconfig
+++ b/arch/x86/kvm/Kconfig
@@ -26,6 +26,7 @@ config KVM
select MMU_NOTIFIER
select ANON_INODES
select HAVE_KVM_IRQCHIP
+ select HAVE_KVM_EVENTFD
---help---
Support hosting fully virtualized guest machines using hardware
virtualization extensions. You will need a fairly recent
diff --git a/arch/x86/kvm/Makefile b/arch/x86/kvm/Makefile
index bee9512..01e3c61 100644
--- a/arch/x86/kvm/Makefile
+++ b/arch/x86/kvm/Makefile
@@ -2,7 +2,7 @@
EXTRA_CFLAGS += -Ivirt/kvm -Iarch/x86/kvm

kvm-y += $(addprefix ../../../virt/kvm/, kvm_main.o ioapic.o \
- coalesced_mmio.o irq_comm.o)
+ coalesced_mmio.o irq_comm.o eventfd.o)
kvm-$(CONFIG_KVM_TRACE) += $(addprefix ../../../virt/kvm/, kvm_trace.o)
kvm-$(CONFIG_IOMMU_API) += $(addprefix ../../../virt/kvm/, iommu.o)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index f064239..15f39fc 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1126,6 +1126,7 @@ int kvm_dev_ioctl_check_extension(long ext)
case KVM_CAP_REINJECT_CONTROL:
case KVM_CAP_IRQ_INJECT_STATUS:
case KVM_CAP_ASSIGN_DEV_IRQ:
+ case KVM_CAP_IRQFD:
r = 1;
break;
case KVM_CAP_COALESCED_MMIO:
diff --git a/include/linux/kvm.h b/include/linux/kvm.h
index 7b17141..8f53f24 100644
--- a/include/linux/kvm.h
+++ b/include/linux/kvm.h
@@ -418,6 +418,7 @@ struct kvm_trace_rec {
#ifdef __KVM_HAVE_MCE
#define KVM_CAP_MCE 31
#endif
+#define KVM_CAP_IRQFD 32

#ifdef KVM_CAP_IRQ_ROUTING

@@ -470,6 +471,15 @@ struct kvm_x86_mce {
};
#endif

+#define KVM_IRQFD_FLAG_DEASSIGN (1 << 0)
+
+struct kvm_irqfd {
+ __u32 fd;
+ __u32 gsi;
+ __u32 flags;
+ __u8 pad[20];
+};
+
/*
* ioctls for VM fds
*/
@@ -514,6 +524,7 @@ struct kvm_x86_mce {
#define KVM_ASSIGN_SET_MSIX_ENTRY \
_IOW(KVMIO, 0x74, struct kvm_assigned_msix_entry)
#define KVM_DEASSIGN_DEV_IRQ _IOW(KVMIO, 0x75, struct kvm_assigned_irq)
+#define KVM_IRQFD _IOW(KVMIO, 0x76, struct kvm_irqfd)

/*
* ioctls for vcpu fds
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 3060bdc..7724dcb 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -136,6 +136,12 @@ struct kvm {
struct list_head vm_list;
struct kvm_io_bus mmio_bus;
struct kvm_io_bus pio_bus;
+#ifdef CONFIG_HAVE_KVM_EVENTFD
+ struct {
+ spinlock_t lock;
+ struct list_head items;
+ } irqfds;
+#endif
struct kvm_vm_stat stat;
struct kvm_arch arch;
atomic_t users_count;
@@ -525,4 +531,22 @@ static inline void kvm_free_irq_routing(struct kvm *kvm) {}

#endif

+#ifdef CONFIG_HAVE_KVM_EVENTFD
+
+void kvm_irqfd_init(struct kvm *kvm);
+int kvm_irqfd(struct kvm *kvm, int fd, int gsi, int flags);
+void kvm_irqfd_release(struct kvm *kvm);
+
+#else
+
+static inline void kvm_irqfd_init(struct kvm *kvm) {}
+static inline int kvm_irqfd(struct kvm *kvm, int fd, int gsi, int flags)
+{
+ return -EINVAL;
+}
+
+static inline void kvm_irqfd_release(struct kvm *kvm) {}
+
+#endif /* CONFIG_HAVE_KVM_EVENTFD */
+
#endif
diff --git a/virt/kvm/Kconfig b/virt/kvm/Kconfig
index 79e83fc..56c6848 100644
--- a/virt/kvm/Kconfig
+++ b/virt/kvm/Kconfig
@@ -5,3 +5,7 @@ config HAVE_KVM

config HAVE_KVM_IRQCHIP
bool
+
+config HAVE_KVM_EVENTFD
+ bool
+ select EVENTFD
diff --git a/virt/kvm/eventfd.c b/virt/kvm/eventfd.c
new file mode 100644
index 0000000..3140123
--- /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);
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 2884baf..dee321e 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -986,6 +986,7 @@ static struct kvm *kvm_create_vm(void)
spin_lock_init(&kvm->mmu_lock);
spin_lock_init(&kvm->requests_lock);
kvm_io_bus_init(&kvm->pio_bus);
+ kvm_irqfd_init(kvm);
mutex_init(&kvm->lock);
kvm_io_bus_init(&kvm->mmio_bus);
init_rwsem(&kvm->slots_lock);
@@ -1071,6 +1072,8 @@ static int kvm_vm_release(struct inode *inode, struct file *filp)
{
struct kvm *kvm = filp->private_data;

+ kvm_irqfd_release(kvm);
+
kvm_put_kvm(kvm);
return 0;
}
@@ -2222,6 +2225,15 @@ static long kvm_vm_ioctl(struct file *filp,
}
#endif
#endif /* KVM_CAP_IRQ_ROUTING */
+ case KVM_IRQFD: {
+ struct kvm_irqfd data;
+
+ r = -EFAULT;
+ if (copy_from_user(&data, argp, sizeof data))
+ goto out;
+ r = kvm_irqfd(kvm, data.fd, data.gsi, data.flags);
+ break;
+ }
default:
r = kvm_arch_vm_ioctl(filp, ioctl, arg);
}
--
1.6.3.3


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