Re: [dpdk-dev] [PATCH] vhost: fix mem share between VM and host

["Xie, Huawei" <huawei.xie@intel.com>]

On 4/11/2016 1:29 AM, Zhe Tao wrote:
>  
> +/* Check the share memory in case the QEMU doesn't set the share option
> + * as on for the memory-backend-file object in the QEMU command line.
> + */
> +
> +int
> +vhost_check_mem_shared(struct vhost_device_ctx ctx)
> +{
> +	struct virtio_net *dev;
> +	struct vhost_virtqueue *vq;
> +	int ret = 0;
> +
> +	dev = get_device(ctx);
> +	if ((dev == NULL) || (dev->mem == NULL))
> +		return -1;
> +
> +	/* check first virtqueue 0 rxq. */
> +	vq = dev->virtqueue[VIRTIO_RXQ];
> +	ret = vq->desc[0].next == 0 ? -1 : 0;
> +
> +	if (ret)
> +		RTE_LOG(ERR, VHOST_CONFIG,
> +			"The mem is not shared between VM and host\n");
> +
> +	return ret;
> +}
> +

Zhe: This is known to vhost-user users that share=on is a must-to-have
option. I think this isn't an issue.
It is OK if we could do some early check in vhost, however we couldn't
assume the value of vq->desc[0].next.
Check if there is other simple and reliable way.