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>
This commit is contained in:
Gregory Haskins
Avi Kivity
Родитель
0ba12d1081
Коммит
721eecbf4f
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@ -26,6 +26,7 @@ config KVM
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select MMU_NOTIFIER
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select ANON_INODES
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select HAVE_KVM_IRQCHIP
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select HAVE_KVM_EVENTFD
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---help---
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Support hosting fully virtualized guest machines using hardware
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virtualization extensions. You will need a fairly recent
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@ -2,7 +2,7 @@
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EXTRA_CFLAGS += -Ivirt/kvm -Iarch/x86/kvm
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kvm-y += $(addprefix ../../../virt/kvm/, kvm_main.o ioapic.o \
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coalesced_mmio.o irq_comm.o)
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coalesced_mmio.o irq_comm.o eventfd.o)
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kvm-$(CONFIG_KVM_TRACE) += $(addprefix ../../../virt/kvm/, kvm_trace.o)
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kvm-$(CONFIG_IOMMU_API) += $(addprefix ../../../virt/kvm/, iommu.o)
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@ -1126,6 +1126,7 @@ int kvm_dev_ioctl_check_extension(long ext)
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case KVM_CAP_REINJECT_CONTROL:
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case KVM_CAP_IRQ_INJECT_STATUS:
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case KVM_CAP_ASSIGN_DEV_IRQ:
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case KVM_CAP_IRQFD:
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r = 1;
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break;
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case KVM_CAP_COALESCED_MMIO:
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@ -418,6 +418,7 @@ struct kvm_trace_rec {
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#ifdef __KVM_HAVE_MCE
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#define KVM_CAP_MCE 31
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#endif
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#define KVM_CAP_IRQFD 32
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#ifdef KVM_CAP_IRQ_ROUTING
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@ -470,6 +471,15 @@ struct kvm_x86_mce {
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};
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#endif
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#define KVM_IRQFD_FLAG_DEASSIGN (1 << 0)
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struct kvm_irqfd {
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__u32 fd;
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__u32 gsi;
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__u32 flags;
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__u8 pad[20];
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};
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/*
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* ioctls for VM fds
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*/
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@ -514,6 +524,7 @@ struct kvm_x86_mce {
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#define KVM_ASSIGN_SET_MSIX_ENTRY \
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_IOW(KVMIO, 0x74, struct kvm_assigned_msix_entry)
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#define KVM_DEASSIGN_DEV_IRQ _IOW(KVMIO, 0x75, struct kvm_assigned_irq)
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#define KVM_IRQFD _IOW(KVMIO, 0x76, struct kvm_irqfd)
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/*
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* ioctls for vcpu fds
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@ -136,6 +136,12 @@ struct kvm {
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struct list_head vm_list;
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struct kvm_io_bus mmio_bus;
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struct kvm_io_bus pio_bus;
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#ifdef CONFIG_HAVE_KVM_EVENTFD
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struct {
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spinlock_t lock;
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struct list_head items;
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} irqfds;
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#endif
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struct kvm_vm_stat stat;
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struct kvm_arch arch;
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atomic_t users_count;
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@ -525,4 +531,22 @@ static inline void kvm_free_irq_routing(struct kvm *kvm) {}
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#endif
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#ifdef CONFIG_HAVE_KVM_EVENTFD
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void kvm_irqfd_init(struct kvm *kvm);
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int kvm_irqfd(struct kvm *kvm, int fd, int gsi, int flags);
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void kvm_irqfd_release(struct kvm *kvm);
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#else
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static inline void kvm_irqfd_init(struct kvm *kvm) {}
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static inline int kvm_irqfd(struct kvm *kvm, int fd, int gsi, int flags)
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{
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return -EINVAL;
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}
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static inline void kvm_irqfd_release(struct kvm *kvm) {}
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#endif /* CONFIG_HAVE_KVM_EVENTFD */
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#endif
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@ -5,3 +5,7 @@ config HAVE_KVM
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config HAVE_KVM_IRQCHIP
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bool
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config HAVE_KVM_EVENTFD
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bool
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select EVENTFD
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@ -0,0 +1,329 @@
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/*
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* kvm eventfd support - use eventfd objects to signal various KVM events
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*
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* Copyright 2009 Novell. All Rights Reserved.
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*
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* Author:
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* Gregory Haskins <ghaskins@novell.com>
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*
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* This file is free software; you can redistribute it and/or modify
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* it under the terms of version 2 of the GNU General Public License
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* as published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA.
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*/
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#include <linux/kvm_host.h>
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#include <linux/workqueue.h>
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#include <linux/syscalls.h>
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#include <linux/wait.h>
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#include <linux/poll.h>
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#include <linux/file.h>
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#include <linux/list.h>
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#include <linux/eventfd.h>
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/*
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* --------------------------------------------------------------------
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* irqfd: Allows an fd to be used to inject an interrupt to the guest
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*
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* Credit goes to Avi Kivity for the original idea.
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* --------------------------------------------------------------------
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*/
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struct _irqfd {
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struct kvm *kvm;
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struct eventfd_ctx *eventfd;
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int gsi;
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struct list_head list;
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poll_table pt;
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wait_queue_head_t *wqh;
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wait_queue_t wait;
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struct work_struct inject;
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struct work_struct shutdown;
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};
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static struct workqueue_struct *irqfd_cleanup_wq;
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static void
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irqfd_inject(struct work_struct *work)
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{
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struct _irqfd *irqfd = container_of(work, struct _irqfd, inject);
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struct kvm *kvm = irqfd->kvm;
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mutex_lock(&kvm->lock);
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kvm_set_irq(kvm, KVM_USERSPACE_IRQ_SOURCE_ID, irqfd->gsi, 1);
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kvm_set_irq(kvm, KVM_USERSPACE_IRQ_SOURCE_ID, irqfd->gsi, 0);
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mutex_unlock(&kvm->lock);
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}
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/*
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* Race-free decouple logic (ordering is critical)
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*/
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static void
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irqfd_shutdown(struct work_struct *work)
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{
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struct _irqfd *irqfd = container_of(work, struct _irqfd, shutdown);
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/*
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* Synchronize with the wait-queue and unhook ourselves to prevent
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* further events.
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*/
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remove_wait_queue(irqfd->wqh, &irqfd->wait);
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/*
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* We know no new events will be scheduled at this point, so block
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* until all previously outstanding events have completed
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*/
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flush_work(&irqfd->inject);
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/*
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* It is now safe to release the object's resources
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*/
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eventfd_ctx_put(irqfd->eventfd);
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kfree(irqfd);
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}
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/* assumes kvm->irqfds.lock is held */
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static bool
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irqfd_is_active(struct _irqfd *irqfd)
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{
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return list_empty(&irqfd->list) ? false : true;
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}
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/*
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* Mark the irqfd as inactive and schedule it for removal
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*
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* assumes kvm->irqfds.lock is held
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*/
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static void
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irqfd_deactivate(struct _irqfd *irqfd)
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{
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BUG_ON(!irqfd_is_active(irqfd));
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list_del_init(&irqfd->list);
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queue_work(irqfd_cleanup_wq, &irqfd->shutdown);
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}
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/*
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* Called with wqh->lock held and interrupts disabled
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*/
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static int
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irqfd_wakeup(wait_queue_t *wait, unsigned mode, int sync, void *key)
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{
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struct _irqfd *irqfd = container_of(wait, struct _irqfd, wait);
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unsigned long flags = (unsigned long)key;
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if (flags & POLLIN)
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/* An event has been signaled, inject an interrupt */
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schedule_work(&irqfd->inject);
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if (flags & POLLHUP) {
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/* The eventfd is closing, detach from KVM */
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struct kvm *kvm = irqfd->kvm;
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unsigned long flags;
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spin_lock_irqsave(&kvm->irqfds.lock, flags);
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/*
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* We must check if someone deactivated the irqfd before
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* we could acquire the irqfds.lock since the item is
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* deactivated from the KVM side before it is unhooked from
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* the wait-queue. If it is already deactivated, we can
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* simply return knowing the other side will cleanup for us.
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* We cannot race against the irqfd going away since the
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* other side is required to acquire wqh->lock, which we hold
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*/
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if (irqfd_is_active(irqfd))
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irqfd_deactivate(irqfd);
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spin_unlock_irqrestore(&kvm->irqfds.lock, flags);
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}
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return 0;
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}
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static void
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irqfd_ptable_queue_proc(struct file *file, wait_queue_head_t *wqh,
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poll_table *pt)
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{
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struct _irqfd *irqfd = container_of(pt, struct _irqfd, pt);
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irqfd->wqh = wqh;
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add_wait_queue(wqh, &irqfd->wait);
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}
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static int
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kvm_irqfd_assign(struct kvm *kvm, int fd, int gsi)
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{
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struct _irqfd *irqfd;
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struct file *file = NULL;
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struct eventfd_ctx *eventfd = NULL;
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int ret;
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unsigned int events;
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irqfd = kzalloc(sizeof(*irqfd), GFP_KERNEL);
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if (!irqfd)
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return -ENOMEM;
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irqfd->kvm = kvm;
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irqfd->gsi = gsi;
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INIT_LIST_HEAD(&irqfd->list);
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INIT_WORK(&irqfd->inject, irqfd_inject);
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INIT_WORK(&irqfd->shutdown, irqfd_shutdown);
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file = eventfd_fget(fd);
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if (IS_ERR(file)) {
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ret = PTR_ERR(file);
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goto fail;
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}
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eventfd = eventfd_ctx_fileget(file);
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if (IS_ERR(eventfd)) {
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ret = PTR_ERR(eventfd);
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goto fail;
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}
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irqfd->eventfd = eventfd;
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/*
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* Install our own custom wake-up handling so we are notified via
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* a callback whenever someone signals the underlying eventfd
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*/
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init_waitqueue_func_entry(&irqfd->wait, irqfd_wakeup);
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init_poll_funcptr(&irqfd->pt, irqfd_ptable_queue_proc);
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events = file->f_op->poll(file, &irqfd->pt);
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spin_lock_irq(&kvm->irqfds.lock);
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list_add_tail(&irqfd->list, &kvm->irqfds.items);
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spin_unlock_irq(&kvm->irqfds.lock);
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/*
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* Check if there was an event already pending on the eventfd
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* before we registered, and trigger it as if we didn't miss it.
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*/
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if (events & POLLIN)
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schedule_work(&irqfd->inject);
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/*
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* do not drop the file until the irqfd is fully initialized, otherwise
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* we might race against the POLLHUP
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*/
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fput(file);
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return 0;
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fail:
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if (eventfd && !IS_ERR(eventfd))
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eventfd_ctx_put(eventfd);
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if (file && !IS_ERR(file))
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fput(file);
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kfree(irqfd);
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return ret;
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}
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void
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kvm_irqfd_init(struct kvm *kvm)
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{
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spin_lock_init(&kvm->irqfds.lock);
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INIT_LIST_HEAD(&kvm->irqfds.items);
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}
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/*
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* shutdown any irqfd's that match fd+gsi
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*/
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static int
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kvm_irqfd_deassign(struct kvm *kvm, int fd, int gsi)
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{
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struct _irqfd *irqfd, *tmp;
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struct eventfd_ctx *eventfd;
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eventfd = eventfd_ctx_fdget(fd);
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if (IS_ERR(eventfd))
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return PTR_ERR(eventfd);
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spin_lock_irq(&kvm->irqfds.lock);
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list_for_each_entry_safe(irqfd, tmp, &kvm->irqfds.items, list) {
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if (irqfd->eventfd == eventfd && irqfd->gsi == gsi)
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irqfd_deactivate(irqfd);
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}
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spin_unlock_irq(&kvm->irqfds.lock);
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eventfd_ctx_put(eventfd);
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/*
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* Block until we know all outstanding shutdown jobs have completed
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* so that we guarantee there will not be any more interrupts on this
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* gsi once this deassign function returns.
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*/
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flush_workqueue(irqfd_cleanup_wq);
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return 0;
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}
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int
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kvm_irqfd(struct kvm *kvm, int fd, int gsi, int flags)
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{
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if (flags & KVM_IRQFD_FLAG_DEASSIGN)
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return kvm_irqfd_deassign(kvm, fd, gsi);
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return kvm_irqfd_assign(kvm, fd, gsi);
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}
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/*
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* This function is called as the kvm VM fd is being released. Shutdown all
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* irqfds that still remain open
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*/
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void
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kvm_irqfd_release(struct kvm *kvm)
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{
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struct _irqfd *irqfd, *tmp;
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spin_lock_irq(&kvm->irqfds.lock);
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list_for_each_entry_safe(irqfd, tmp, &kvm->irqfds.items, list)
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irqfd_deactivate(irqfd);
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spin_unlock_irq(&kvm->irqfds.lock);
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/*
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* Block until we know all outstanding shutdown jobs have completed
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* since we do not take a kvm* reference.
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*/
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flush_workqueue(irqfd_cleanup_wq);
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}
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/*
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* create a host-wide workqueue for issuing deferred shutdown requests
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* aggregated from all vm* instances. We need our own isolated single-thread
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* queue to prevent deadlock against flushing the normal work-queue.
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*/
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static int __init irqfd_module_init(void)
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{
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irqfd_cleanup_wq = create_singlethread_workqueue("kvm-irqfd-cleanup");
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if (!irqfd_cleanup_wq)
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return -ENOMEM;
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return 0;
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}
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static void __exit irqfd_module_exit(void)
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{
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destroy_workqueue(irqfd_cleanup_wq);
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}
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module_init(irqfd_module_init);
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module_exit(irqfd_module_exit);
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|
|
@ -986,6 +986,7 @@ static struct kvm *kvm_create_vm(void)
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spin_lock_init(&kvm->mmu_lock);
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spin_lock_init(&kvm->requests_lock);
|
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kvm_io_bus_init(&kvm->pio_bus);
|
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kvm_irqfd_init(kvm);
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mutex_init(&kvm->lock);
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kvm_io_bus_init(&kvm->mmio_bus);
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init_rwsem(&kvm->slots_lock);
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|
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@ -1071,6 +1072,8 @@ static int kvm_vm_release(struct inode *inode, struct file *filp)
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{
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struct kvm *kvm = filp->private_data;
|
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kvm_irqfd_release(kvm);
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kvm_put_kvm(kvm);
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return 0;
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}
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@ -2222,6 +2225,15 @@ static long kvm_vm_ioctl(struct file *filp,
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}
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#endif
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#endif /* KVM_CAP_IRQ_ROUTING */
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case KVM_IRQFD: {
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struct kvm_irqfd data;
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r = -EFAULT;
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if (copy_from_user(&data, argp, sizeof data))
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goto out;
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r = kvm_irqfd(kvm, data.fd, data.gsi, data.flags);
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break;
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}
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default:
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r = kvm_arch_vm_ioctl(filp, ioctl, arg);
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}
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|
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