linux-kernel - Re: [KVM PATCH v10] kvm: add support for irqfd

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Message-ID: <20090527130447.GA11643@redhat.com>
Date:	Wed, 27 May 2009 16:55:59 +0300
From:	"Michael S. Tsirkin" <mst@...hat.com>
To:	Gregory Haskins <ghaskins@...ell.com>
Cc:	kvm@...r.kernel.org, linux-kernel@...r.kernel.org, avi@...hat.com,
	davidel@...ilserver.org, mtosatti@...hat.com
Subject: Re: [KVM PATCH v10] kvm: add support for irqfd

On Wed, May 20, 2009 at 10:30:49AM -0400, Gregory Haskins wrote:
> +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;
> +	}

So we get a reference to a file, and unless the user is nice to us, it
will only be dropped when kvm char device file is closed?
I think this will deadlock if the fd in question is the open kvm char device.


-- 
MST
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