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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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      Last update: 2009-08-16 11:49    [W:0.047 / U:0.400 seconds]
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