From: Gregory Haskins <[email protected]> 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 <[email protected]> Signed-off-by: Avi Kivity <[email protected]> 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 7978d32..98c2434 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -1084,6 +1084,7 @@ 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 8f410d3..3b6caf5 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; @@ -528,4 +529,7 @@ static inline void kvm_free_irq_routing(struct kvm *kvm) {} #endif +int kvm_irqfd(struct kvm *kvm, int fd, int gsi, int flags); +void kvm_irqfd_release(struct kvm *kvm); + #endif diff --git a/virt/kvm/eventfd.c b/virt/kvm/eventfd.c new file mode 100644 index 0000000..72a282e --- /dev/null +++ b/virt/kvm/eventfd.c @@ -0,0 +1,228 @@ +/* + * kvm eventfd support - use eventfd objects to signal various KVM events + * + * Copyright 2009 Novell. All Rights Reserved. + * + * Author: + * Gregory Haskins <[email protected]> + * + * 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> + +/* + * -------------------------------------------------------------------- + * 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; + 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 wake_up is called with interrupts disabled. 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); +} + +static int +kvm_assign_irqfd(struct kvm *kvm, int fd, int gsi) +{ + struct _irqfd *irqfd; + struct file *file = NULL; + 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); + + /* + * Embed the file* lifetime in the irqfd. + */ + file = fget(fd); + 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; + + irqfd->file = file; + + mutex_lock(&kvm->lock); + list_add_tail(&irqfd->list, &kvm->irqfds); + mutex_unlock(&kvm->lock); + + return 0; + +fail: + if (irqfd->wqh) + remove_wait_queue(irqfd->wqh, &irqfd->wait); + + if (file && !IS_ERR(file)) + fput(file); + + kfree(irqfd); + return ret; +} + +static void +irqfd_release(struct _irqfd *irqfd) +{ + /* + * The ordering is important. We must remove ourselves from the wqh + * first to ensure no more event callbacks are issued, and then flush + * any previously scheduled work prior to freeing the memory + */ + remove_wait_queue(irqfd->wqh, &irqfd->wait); + + flush_work(&irqfd->work); + + fput(irqfd->file); + kfree(irqfd); +} + +static struct _irqfd * +irqfd_remove(struct kvm *kvm, struct file *file, int gsi) +{ + struct _irqfd *irqfd; + + mutex_lock(&kvm->lock); + + /* + * linear search isn't brilliant, but this should be an infrequent + * slow-path operation, and the list should not grow very large + */ + list_for_each_entry(irqfd, &kvm->irqfds, list) { + if (irqfd->file != file || irqfd->gsi != gsi) + continue; + + list_del(&irqfd->list); + mutex_unlock(&kvm->lock); + + return irqfd; + } + + mutex_unlock(&kvm->lock); + + return NULL; +} + +static int +kvm_deassign_irqfd(struct kvm *kvm, int fd, int gsi) +{ + struct _irqfd *irqfd; + struct file *file; + int count = 0; + + file = fget(fd); + if (IS_ERR(file)) + return PTR_ERR(file); + + while ((irqfd = irqfd_remove(kvm, file, gsi))) { + /* + * We remove the item from the list under the lock, but we + * free it outside the lock to avoid deadlocking with the + * flush_work and the work_item taking the lock + */ + irqfd_release(irqfd); + count++; + } + + fput(file); + + return count ? count : -ENOENT; +} + +int +kvm_irqfd(struct kvm *kvm, int fd, int gsi, int flags) +{ + if (flags & KVM_IRQFD_FLAG_DEASSIGN) + return kvm_deassign_irqfd(kvm, fd, gsi); + + return kvm_assign_irqfd(kvm, fd, gsi); +} + +void +kvm_irqfd_release(struct kvm *kvm) +{ + struct _irqfd *irqfd, *tmp; + + /* don't bother with the lock..we are shutting down */ + list_for_each_entry_safe(irqfd, tmp, &kvm->irqfds, list) { + list_del(&irqfd->list); + irqfd_release(irqfd); + } +} diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index bebfe59..b58837d 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -983,6 +983,7 @@ 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); @@ -1034,6 +1035,7 @@ 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); @@ -2210,6 +2212,15 @@ 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); } -- To unsubscribe from this list: send the line "unsubscribe kvm-commits" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
