Re: [KVM PATCH v4 2/2] kvm: add support for irqfd via eventfd-notification interface

Gregory Haskins
2009-05-06T11:35:30Z

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Al, Davide,

Gregory Haskins wrote:
> +
> +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;
> + }
> +
> + irqfd->file = file;
> +
> + /*
> + * 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;
> +
> + mutex_lock(&kvm->lock);
> + list_add_tail(&irqfd->list, &kvm->irqfds);
> + mutex_unlock(&kvm->lock);
> +
> + ret = get_unused_fd();
> + if (ret < 0)
> + goto fail;
> +
> + fd = ret;
> +
> + fd_install(fd, file);
>

Can you comment on whether this function needs to take an additional
reference on file here? (one for the one held by userspace/fd, and the
other for irqfd->file) My instinct is telling me this may be currently
broken, but I am not sure.

-Greg

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