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![Julia Lawall](/assets/img/avatar_default.png)
This code is not executed before file has been initialized to the result of calling eventfd_fget. This function returns an ERR_PTR value in an error case instead of NULL. Thus the test that file is not NULL is always true. A simplified version of the semantic match that finds this problem is as follows: (http://coccinelle.lip6.fr/) // <smpl> @match exists@ expression x, E; statement S1, S2; @@ x = eventfd_fget(...) ... when != x = E ( * if (x == NULL || ...) S1 else S2 | * if (x == NULL && ...) S1 else S2 ) // </smpl> Signed-off-by: Julia Lawall <julia@diku.dk> Signed-off-by: Avi Kivity <avi@redhat.com>
578 lines
13 KiB
C
578 lines
13 KiB
C
/*
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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/kvm.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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#include <linux/kernel.h>
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#include "iodev.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->irq_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->irq_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 (!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_eventfd_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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INIT_LIST_HEAD(&kvm->ioeventfds);
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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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/*
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* --------------------------------------------------------------------
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* ioeventfd: translate a PIO/MMIO memory write to an eventfd signal.
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*
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* userspace can register a PIO/MMIO address with an eventfd for receiving
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* notification when the memory has been touched.
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* --------------------------------------------------------------------
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*/
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struct _ioeventfd {
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struct list_head list;
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u64 addr;
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int length;
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struct eventfd_ctx *eventfd;
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u64 datamatch;
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struct kvm_io_device dev;
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bool wildcard;
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};
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static inline struct _ioeventfd *
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to_ioeventfd(struct kvm_io_device *dev)
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{
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return container_of(dev, struct _ioeventfd, dev);
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}
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static void
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ioeventfd_release(struct _ioeventfd *p)
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{
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eventfd_ctx_put(p->eventfd);
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list_del(&p->list);
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kfree(p);
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}
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static bool
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ioeventfd_in_range(struct _ioeventfd *p, gpa_t addr, int len, const void *val)
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{
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u64 _val;
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if (!(addr == p->addr && len == p->length))
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/* address-range must be precise for a hit */
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return false;
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if (p->wildcard)
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/* all else equal, wildcard is always a hit */
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return true;
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/* otherwise, we have to actually compare the data */
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BUG_ON(!IS_ALIGNED((unsigned long)val, len));
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switch (len) {
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case 1:
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_val = *(u8 *)val;
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break;
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case 2:
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_val = *(u16 *)val;
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break;
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case 4:
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_val = *(u32 *)val;
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break;
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case 8:
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_val = *(u64 *)val;
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break;
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default:
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return false;
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}
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return _val == p->datamatch ? true : false;
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}
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/* MMIO/PIO writes trigger an event if the addr/val match */
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static int
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ioeventfd_write(struct kvm_io_device *this, gpa_t addr, int len,
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const void *val)
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{
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struct _ioeventfd *p = to_ioeventfd(this);
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if (!ioeventfd_in_range(p, addr, len, val))
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return -EOPNOTSUPP;
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eventfd_signal(p->eventfd, 1);
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return 0;
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}
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/*
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* This function is called as KVM is completely shutting down. We do not
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* need to worry about locking just nuke anything we have as quickly as possible
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*/
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static void
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ioeventfd_destructor(struct kvm_io_device *this)
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{
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struct _ioeventfd *p = to_ioeventfd(this);
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ioeventfd_release(p);
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}
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static const struct kvm_io_device_ops ioeventfd_ops = {
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.write = ioeventfd_write,
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.destructor = ioeventfd_destructor,
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};
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/* assumes kvm->slots_lock held */
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static bool
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ioeventfd_check_collision(struct kvm *kvm, struct _ioeventfd *p)
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{
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struct _ioeventfd *_p;
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list_for_each_entry(_p, &kvm->ioeventfds, list)
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if (_p->addr == p->addr && _p->length == p->length &&
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(_p->wildcard || p->wildcard ||
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_p->datamatch == p->datamatch))
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return true;
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return false;
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}
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static int
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kvm_assign_ioeventfd(struct kvm *kvm, struct kvm_ioeventfd *args)
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{
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int pio = args->flags & KVM_IOEVENTFD_FLAG_PIO;
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struct kvm_io_bus *bus = pio ? &kvm->pio_bus : &kvm->mmio_bus;
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struct _ioeventfd *p;
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struct eventfd_ctx *eventfd;
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int ret;
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/* must be natural-word sized */
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switch (args->len) {
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case 1:
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case 2:
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case 4:
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case 8:
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break;
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default:
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return -EINVAL;
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}
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/* check for range overflow */
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if (args->addr + args->len < args->addr)
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return -EINVAL;
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/* check for extra flags that we don't understand */
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if (args->flags & ~KVM_IOEVENTFD_VALID_FLAG_MASK)
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return -EINVAL;
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eventfd = eventfd_ctx_fdget(args->fd);
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if (IS_ERR(eventfd))
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return PTR_ERR(eventfd);
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p = kzalloc(sizeof(*p), GFP_KERNEL);
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if (!p) {
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ret = -ENOMEM;
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goto fail;
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}
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INIT_LIST_HEAD(&p->list);
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p->addr = args->addr;
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p->length = args->len;
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p->eventfd = eventfd;
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/* The datamatch feature is optional, otherwise this is a wildcard */
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if (args->flags & KVM_IOEVENTFD_FLAG_DATAMATCH)
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p->datamatch = args->datamatch;
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else
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p->wildcard = true;
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down_write(&kvm->slots_lock);
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/* Verify that there isnt a match already */
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if (ioeventfd_check_collision(kvm, p)) {
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ret = -EEXIST;
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goto unlock_fail;
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}
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kvm_iodevice_init(&p->dev, &ioeventfd_ops);
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ret = __kvm_io_bus_register_dev(bus, &p->dev);
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if (ret < 0)
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goto unlock_fail;
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list_add_tail(&p->list, &kvm->ioeventfds);
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up_write(&kvm->slots_lock);
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return 0;
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unlock_fail:
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up_write(&kvm->slots_lock);
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fail:
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kfree(p);
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eventfd_ctx_put(eventfd);
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return ret;
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}
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static int
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kvm_deassign_ioeventfd(struct kvm *kvm, struct kvm_ioeventfd *args)
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{
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int pio = args->flags & KVM_IOEVENTFD_FLAG_PIO;
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struct kvm_io_bus *bus = pio ? &kvm->pio_bus : &kvm->mmio_bus;
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struct _ioeventfd *p, *tmp;
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struct eventfd_ctx *eventfd;
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int ret = -ENOENT;
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eventfd = eventfd_ctx_fdget(args->fd);
|
|
if (IS_ERR(eventfd))
|
|
return PTR_ERR(eventfd);
|
|
|
|
down_write(&kvm->slots_lock);
|
|
|
|
list_for_each_entry_safe(p, tmp, &kvm->ioeventfds, list) {
|
|
bool wildcard = !(args->flags & KVM_IOEVENTFD_FLAG_DATAMATCH);
|
|
|
|
if (p->eventfd != eventfd ||
|
|
p->addr != args->addr ||
|
|
p->length != args->len ||
|
|
p->wildcard != wildcard)
|
|
continue;
|
|
|
|
if (!p->wildcard && p->datamatch != args->datamatch)
|
|
continue;
|
|
|
|
__kvm_io_bus_unregister_dev(bus, &p->dev);
|
|
ioeventfd_release(p);
|
|
ret = 0;
|
|
break;
|
|
}
|
|
|
|
up_write(&kvm->slots_lock);
|
|
|
|
eventfd_ctx_put(eventfd);
|
|
|
|
return ret;
|
|
}
|
|
|
|
int
|
|
kvm_ioeventfd(struct kvm *kvm, struct kvm_ioeventfd *args)
|
|
{
|
|
if (args->flags & KVM_IOEVENTFD_FLAG_DEASSIGN)
|
|
return kvm_deassign_ioeventfd(kvm, args);
|
|
|
|
return kvm_assign_ioeventfd(kvm, args);
|
|
}
|