From mboxrd@z Thu Jan  1 00:00:00 1970
From: Yuanhan Liu <yuanhan.liu@linux.intel.com>
Subject: Re: [PATCH v2] vhost: Fix default value of kickfd and
	callfd
Date: Fri, 11 Mar 2016 15:19:07 +0800
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To: Tetsuya Mukawa <mukawa@igel.co.jp>
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On Thu, Mar 10, 2016 at 04:06:05PM +0900, Tetsuya Mukawa wrote:
> Currently, default values of kickfd and callfd are -1.
> If the values are -1, current code guesses kickfd and callfd haven't
> been initialized yet. And vhost library will guess the virtqueue isn't
> ready for processing.
> But callfd and kickfd will be set as -1 when "--enable-kvm"
> isn't specified in QEMU command line. It means we cannot treat -1 as
> uninitialized state. The patch changes default values to -2. And the
> patch defines -2 as VIRTIO_UNINITIALIZED_EVENTFD.

This looks more like a workaround to me. Besides, this patch would make
following fail:

    eventfd_write(vq->callfd, (eventfd_t)1);

	--yliu