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    Subject[KVM PATCH v5 2/2] kvm: add support for irqfd via eventfd-notification interface
    Date
    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>
    ---
    arch/x86/kvm/Makefile | 2 -
    arch/x86/kvm/x86.c | 1
    include/linux/kvm.h | 8 ++
    include/linux/kvm_host.h | 4 +
    virt/kvm/irqfd.c | 163 ++++++++++++++++++++++++++++++++++++++++++++++
    virt/kvm/kvm_main.c | 11 +++
    6 files changed, 188 insertions(+), 1 deletions(-)
    create mode 100644 virt/kvm/irqfd.c
    diff --git a/arch/x86/kvm/Makefile b/arch/x86/kvm/Makefile
    index b43c4ef..d5fff51 100644
    --- a/arch/x86/kvm/Makefile
    +++ b/arch/x86/kvm/Makefile
    @@ -3,7 +3,7 @@
    #

    common-objs = $(addprefix ../../../virt/kvm/, kvm_main.o ioapic.o \
    - coalesced_mmio.o irq_comm.o)
    + coalesced_mmio.o irq_comm.o irqfd.o)
    ifeq ($(CONFIG_KVM_TRACE),y)
    common-objs += $(addprefix ../../../virt/kvm/, kvm_trace.o)
    endif
    diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
    index 308d8e9..e68e415 100644
    --- a/arch/x86/kvm/x86.c
    +++ b/arch/x86/kvm/x86.c
    @@ -1026,6 +1026,7 @@ 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 3db5d8d..ff8a08a 100644
    --- a/include/linux/kvm.h
    +++ b/include/linux/kvm.h
    @@ -415,6 +415,7 @@ struct kvm_trace_rec {
    #define KVM_CAP_ASSIGN_DEV_IRQ 29
    /* Another bug in KVM_SET_USER_MEMORY_REGION fixed: */
    #define KVM_CAP_JOIN_MEMORY_REGIONS_WORKS 30
    +#define KVM_CAP_IRQFD 31

    #ifdef KVM_CAP_IRQ_ROUTING

    @@ -454,6 +455,12 @@ struct kvm_irq_routing {

    #endif

    +struct kvm_irqfd {
    + __u32 gsi;
    + __u32 flags;
    + __u8 pad[24];
    +};
    +
    /*
    * ioctls for VM fds
    */
    @@ -498,6 +505,7 @@ struct kvm_irq_routing {
    #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 095ebb6..6a8d1c1 100644
    --- a/include/linux/kvm_host.h
    +++ b/include/linux/kvm_host.h
    @@ -134,6 +134,7 @@ struct kvm {
    struct list_head vm_list;
    struct kvm_io_bus mmio_bus;
    struct kvm_io_bus pio_bus;
    + struct list_head irqfds;
    struct kvm_vm_stat stat;
    struct kvm_arch arch;
    atomic_t users_count;
    @@ -524,4 +525,7 @@ static inline void kvm_free_irq_routing(struct kvm *kvm) {}

    #endif

    +int kvm_irqfd(struct kvm *kvm, int gsi, int flags);
    +void kvm_irqfd_release(struct kvm *kvm);
    +
    #endif
    diff --git a/virt/kvm/irqfd.c b/virt/kvm/irqfd.c
    new file mode 100644
    index 0000000..962e90e
    --- /dev/null
    +++ b/virt/kvm/irqfd.c
    @@ -0,0 +1,163 @@
    +/*
    + * irqfd: Allows an eventfd to be used to inject an interrupt to the guest
    + *
    + * Credit goes to Avi Kivity for the original idea.
    + *
    + * 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/eventfd.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>
    +
    +struct _irqfd {
    + struct kvm *kvm;
    + int gsi;
    + struct file *file;
    + struct list_head list;
    + poll_table pt;
    + wait_queue_head_t *wqh;
    + wait_queue_t wait;
    + struct work_struct work;
    +};
    +
    +static void
    +irqfd_inject(struct work_struct *work)
    +{
    + struct _irqfd *irqfd = container_of(work, struct _irqfd, work);
    + 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);
    +}
    +
    +static int
    +irqfd_wakeup(wait_queue_t *wait, unsigned mode, int sync, void *key)
    +{
    + struct _irqfd *irqfd = container_of(wait, struct _irqfd, wait);
    +
    + /*
    + * The eventfd calls its wake_up with interrupts disabled, and
    + * eventfd_signal() may be called from interrupt context. Therefore
    + * we need to defer the IRQ injection until later since we need to
    + * acquire the kvm->lock to do so.
    + */
    + schedule_work(&irqfd->work);
    +
    + 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);
    +}
    +
    +int
    +kvm_irqfd(struct kvm *kvm, int gsi, int flags)
    +{
    + struct _irqfd *irqfd;
    + struct file *file = NULL;
    + int fd = -1;
    + int ret;
    +
    + irqfd = kzalloc(sizeof(*irqfd), GFP_KERNEL);
    + if (!irqfd)
    + return -ENOMEM;
    +
    + irqfd->kvm = kvm;
    + irqfd->gsi = gsi;
    + INIT_LIST_HEAD(&irqfd->list);
    + INIT_WORK(&irqfd->work, irqfd_inject);
    +
    + /*
    + * We re-use eventfd for irqfd, and therefore will embed the eventfd
    + * lifetime in the irqfd.
    + */
    + file = eventfd_file_create(0, 0);
    + if (IS_ERR(file)) {
    + ret = PTR_ERR(file);
    + goto fail;
    + }
    +
    + /*
    + * 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);
    +
    + ret = file->f_op->poll(file, &irqfd->pt);
    + if (ret < 0)
    + goto fail;
    +
    + fd = get_unused_fd();
    + if (fd < 0) {
    + ret = fd;
    + goto fail;
    + }
    +
    + fd_install(fd, file);
    +
    + get_file(file);
    + irqfd->file = file;
    +
    + mutex_lock(&kvm->lock);
    + list_add_tail(&irqfd->list, &kvm->irqfds);
    + mutex_unlock(&kvm->lock);
    +
    + return fd;
    +
    +fail:
    + if (irqfd->wqh)
    + remove_wait_queue(irqfd->wqh, &irqfd->wait);
    +
    + if (file && !IS_ERR(file))
    + fput(file);
    +
    + kfree(irqfd);
    + return ret;
    +}
    +
    +void
    +kvm_irqfd_release(struct kvm *kvm)
    +{
    + struct _irqfd *irqfd, *tmp;
    +
    + list_for_each_entry_safe(irqfd, tmp, &kvm->irqfds, list) {
    + remove_wait_queue(irqfd->wqh, &irqfd->wait);
    +
    + flush_work(&irqfd->work);
    + fput(irqfd->file);
    +
    + list_del(&irqfd->list);
    + kfree(irqfd);
    + }
    +}
    diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
    index 2b73e19..8b3b06a 100644
    --- a/virt/kvm/kvm_main.c
    +++ b/virt/kvm/kvm_main.c
    @@ -972,6 +972,7 @@ static struct kvm *kvm_create_vm(void)
    atomic_inc(&kvm->mm->mm_count);
    spin_lock_init(&kvm->mmu_lock);
    kvm_io_bus_init(&kvm->pio_bus);
    + INIT_LIST_HEAD(&kvm->irqfds);
    mutex_init(&kvm->lock);
    kvm_io_bus_init(&kvm->mmio_bus);
    init_rwsem(&kvm->slots_lock);
    @@ -1023,6 +1024,7 @@ static void kvm_destroy_vm(struct kvm *kvm)
    spin_lock(&kvm_lock);
    list_del(&kvm->vm_list);
    spin_unlock(&kvm_lock);
    + kvm_irqfd_release(kvm);
    kvm_free_irq_routing(kvm);
    kvm_io_bus_destroy(&kvm->pio_bus);
    kvm_io_bus_destroy(&kvm->mmio_bus);
    @@ -2197,6 +2199,15 @@ 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.gsi, data.flags);
    + break;
    + }
    default:
    r = kvm_arch_vm_ioctl(filp, ioctl, arg);
    }


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