Re: [dpdk-dev] [PATCH] vhost: Fix default value of kickfd and callfd

["Tan, Jianfeng" <jianfeng.tan@intel.com>]

On 3/10/2016 2:14 PM, Tetsuya Mukawa wrote:
> Currently, default value of kickfd and callfd is -1.
> If the value is -1, current code guess kickfd and callfd hasn'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 value to -2. And the
> patch defines -2 as VIRTIO_UNINITIALIZED_EVENTFD.
>
> Signed-off-by: Tetsuya Mukawa <mukawa@igel.co.jp>
> ---
>   lib/librte_vhost/rte_virtio_net.h             | 1 +
>   lib/librte_vhost/vhost_user/virtio-net-user.c | 7 ++++---
>   lib/librte_vhost/virtio-net.c                 | 4 ++--
>   3 files changed, 7 insertions(+), 5 deletions(-)
>
> diff --git a/lib/librte_vhost/rte_virtio_net.h b/lib/librte_vhost/rte_virtio_net.h
> index 7d1fde2..d745707 100644
> --- a/lib/librte_vhost/rte_virtio_net.h
> +++ b/lib/librte_vhost/rte_virtio_net.h
> @@ -89,6 +89,7 @@ struct vhost_virtqueue {
>   	uint16_t		vhost_hlen;		/**< Vhost header length (varies depending on RX merge buffers. */
>   	volatile uint16_t	last_used_idx;		/**< Last index used on the available ring */
>   	volatile uint16_t	last_used_idx_res;	/**< Used for multiple devices reserving buffers. */
> +#define VIRTIO_UNINITIALIZED_EVENTFD	(-2)
>   	int			callfd;			/**< Used to notify the guest (trigger interrupt). */
>   	int			kickfd;			/**< Currently unused as polling mode is enabled. */
>   	int			enabled;
> diff --git a/lib/librte_vhost/vhost_user/virtio-net-user.c b/lib/librte_vhost/vhost_user/virtio-net-user.c
> index 65b5652..591f9bf 100644
> --- a/lib/librte_vhost/vhost_user/virtio-net-user.c
> +++ b/lib/librte_vhost/vhost_user/virtio-net-user.c
> @@ -225,8 +225,8 @@ static int
>   vq_is_ready(struct vhost_virtqueue *vq)
>   {
>   	return vq && vq->desc   &&
> -	       vq->kickfd != -1 &&
> -	       vq->callfd != -1;
> +	       vq->kickfd != VIRTIO_UNINITIALIZED_EVENTFD &&
> +	       vq->callfd != VIRTIO_UNINITIALIZED_EVENTFD;
>   }
>   
>   static int
> @@ -318,7 +318,8 @@ user_get_vring_base(struct vhost_device_ctx ctx,
>   	 */
>   	if (dev->virtqueue[state->index]->kickfd >= 0) {
>   		close(dev->virtqueue[state->index]->kickfd);

Then -1 will be a valid value, need to check if it's not -1 to close()? 
Nevertheless, close(-1) brings no big problem.

Thanks,
Jianfeng

> -		dev->virtqueue[state->index]->kickfd = -1;
> +		dev->virtqueue[state->index]->kickfd =
> +					VIRTIO_UNINITIALIZED_EVENTFD;
>   	}
>   
>   	return 0;
> diff --git a/lib/librte_vhost/virtio-net.c b/lib/librte_vhost/virtio-net.c
> index fe1a77e..3498e9d 100644
> --- a/lib/librte_vhost/virtio-net.c
> +++ b/lib/librte_vhost/virtio-net.c
> @@ -263,8 +263,8 @@ init_vring_queue(struct vhost_virtqueue *vq, int qp_idx)
>   {
>   	memset(vq, 0, sizeof(struct vhost_virtqueue));
>   
> -	vq->kickfd = -1;
> -	vq->callfd = -1;
> +	vq->kickfd = VIRTIO_UNINITIALIZED_EVENTFD;
> +	vq->callfd = VIRTIO_UNINITIALIZED_EVENTFD;
>   
>   	/* Backends are set to -1 indicating an inactive device. */
>   	vq->backend = -1;