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Date: Tue, 2 Dec 2014 21:03:45 +0200
From: "Michael S. Tsirkin" <mst@redhat.com>
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In-Reply-To: <20141202164136.1a57f358.cornelia.huck@de.ibm.com>
Subject: Re: [Qemu-devel] [PATCH RFC v5 07/19] virtio: allow virtio-1 queue
	layout
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To: Cornelia Huck <cornelia.huck@de.ibm.com>
Cc: thuth@linux.vnet.ibm.com, rusty@rustcorp.com.au, qemu-devel@nongnu.org, kvm@vger.kernel.org, virtualization@lists.linux-foundation.org

On Tue, Dec 02, 2014 at 04:41:36PM +0100, Cornelia Huck wrote:
>  void virtio_queue_set_num(VirtIODevice *vdev, int n, int num)
>  {
> +    /*
> +     * For virtio-1 devices, the number of buffers may only be
> +     * updated if the ring addresses have not yet been set up.

Where does it say that?

> +     */
> +    if (virtio_has_feature(vdev, VIRTIO_F_VERSION_1) &&
> +        vdev->vq[n].vring.desc) {
> +        error_report("tried to modify buffer num for virtio-1 device");
> +        return;
> +    }
>      /* Don't allow guest to flip queue between existent and
>       * nonexistent states, or to set it to an invalid size.
>       */