Re: [RFC 4/5] VSOCK: Introduce vhost-vsock.ko

[Asias He <asias@redhat.com>]

On Thu, Jun 27, 2013 at 01:42:46PM +0300, Michael S. Tsirkin wrote:
> On Thu, Jun 27, 2013 at 04:00:03PM +0800, Asias He wrote:
> > VM sockets vhost transport implementation. This module runs in host
> > kernel.
> > 
> > Signed-off-by: Asias He <asias@redhat.com>
> 
> Has any thought been given to how this affects migration?
> I don't see any API for an application to
> move to a different host and reconnect to a running
> vsock in guest.
> 
> I think we could merge without this, there are more
> pressing issues, but it's probably a requirement
> if you want this to replace e.g. serial in many
> scenarious.

I do not plan to support migration for the initial merge as well.

Reconnection is one issue needs to be addressed. Another issue is that if
the destination host is running vhost-vsock already, the port might be
used already. We probably need namesapce support.

> > ---
> >  drivers/vhost/vsock.c | 534 ++++++++++++++++++++++++++++++++++++++++++++++++++
> >  drivers/vhost/vsock.h |   4 +
> >  2 files changed, 538 insertions(+)
> >  create mode 100644 drivers/vhost/vsock.c
> >  create mode 100644 drivers/vhost/vsock.h
> > 
> > diff --git a/drivers/vhost/vsock.c b/drivers/vhost/vsock.c
> > new file mode 100644
> > index 0000000..cb54090
> > --- /dev/null
> > +++ b/drivers/vhost/vsock.c
> > @@ -0,0 +1,534 @@
> > +/*
> > + * vhost transport for vsock
> > + *
> > + * Copyright (C) 2013 Red Hat, Inc.
> > + * Author: Asias He <asias@redhat.com>
> > + *
> > + * This work is licensed under the terms of the GNU GPL, version 2.
> > + */
> > +#include <linux/miscdevice.h>
> > +#include <linux/module.h>
> > +#include <linux/mutex.h>
> > +#include <net/sock.h>
> > +#include <linux/virtio_vsock.h>
> > +#include <linux/vhost.h>
> > +
> > +#include "../../../net/vmw_vsock/af_vsock.h"
> 
> Send patch to move this to include/linux ?

Okay. Will cook a patch.

> > +#include "vhost.h"
> > +#include "vsock.h"
> > +
> > +#define VHOST_VSOCK_DEFAULT_HOST_CID	2;
> 
> Sure you want that ; there? This can result in strange code, e.g.
> 
> 	int a = VHOST_VSOCK_DEFAULT_HOST_CID + 1;
> 	set's a to 2.

Fixed.

> > +
> > +static int vhost_transport_socket_init(struct vsock_sock *vsk,
> > +				       struct vsock_sock *psk);
> > +
> > +enum {
> > +	VHOST_VSOCK_FEATURES = VHOST_FEATURES,
> > +};
> > +
> > +/* Used to track all the vhost_vsock instacne on the system. */
> 
> typo

Fixed.

> > +static LIST_HEAD(vhost_vsock_list);
> > +static DEFINE_MUTEX(vhost_vsock_mutex);
> > +
> > +struct vhost_vsock_virtqueue {
> > +	struct vhost_virtqueue vq;
> > +};
> > +
> > +struct vhost_vsock {
> > +	/* Vhost device */
> > +	struct vhost_dev dev;
> > +	/* Vhost vsock virtqueue*/
> > +	struct vhost_vsock_virtqueue vqs[VSOCK_VQ_MAX];
> > +	/* Link to global vhost_vsock_list*/
> > +	struct list_head list;
> > +	/* Head for pkt from host to guest */
> > +	struct list_head send_pkt_list;
> > +	/* Work item to send pkt */
> > +	struct vhost_work send_pkt_work;
> > +	/* Guest contex id this vhost_vsock instance handles */
> > +	u32 guest_cid;
> > +};
> > +
> > +static u32 vhost_transport_get_local_cid(void)
> > +{
> > +	u32 cid = VHOST_VSOCK_DEFAULT_HOST_CID;
> > +	return cid;
> > +}
> > +
> 
> Interesting. So all hosts in fact have the same CID?

Yes. Andy commented on this already.

> > +static struct vhost_vsock *vhost_vsock_get(u32 guest_cid)
> > +{
> > +	struct vhost_vsock *vsock;
> > +
> > +	mutex_lock(&vhost_vsock_mutex);
> > +	list_for_each_entry(vsock, &vhost_vsock_list, list) {
> > +		if (vsock->guest_cid == guest_cid) {
> > +			mutex_unlock(&vhost_vsock_mutex);
> > +			return vsock;
> > +		}
> > +	}
> > +	mutex_unlock(&vhost_vsock_mutex);
> > +
> > +	return NULL;
> > +}
> > +
> > +static void
> > +vhost_transport_do_send_pkt(struct vhost_vsock *vsock,
> > +			    struct vhost_virtqueue *vq)
> > +{
> > +	struct virtio_vsock_pkt *pkt;
> > +	unsigned out, in;
> > +	struct sock *sk;
> > +	int head, ret;
> > +
> > +	mutex_lock(&vq->mutex);
> > +	vhost_disable_notify(&vsock->dev, vq);
> > +	for (;;) {
> > +		if (list_empty(&vsock->send_pkt_list)) {
> > +			vhost_enable_notify(&vsock->dev, vq);
> > +			break;
> > +		}
> > +
> > +		head = vhost_get_vq_desc(&vsock->dev, vq, vq->iov,
> > +					ARRAY_SIZE(vq->iov), &out, &in,
> > +					NULL, NULL);
> > +		pr_debug("%s: head = %d\n", __func__, head);
> > +		if (head < 0)
> > +			break;
> > +
> > +		if (head == vq->num) {
> > +			if (unlikely(vhost_enable_notify(&vsock->dev, vq))) {
> > +				vhost_disable_notify(&vsock->dev, vq);
> > +				continue;
> > +			}
> > +			break;
> > +		}
> > +
> > +		pkt = list_first_entry(&vsock->send_pkt_list,
> > +				       struct virtio_vsock_pkt, list);
> > +		list_del_init(&pkt->list);
> > +
> > +		/* FIXME: no assumption of frame layout */
> 
> Pls fix. memcpy_from_iovec is not harder.

Do we have this helper?

> > +		ret = __copy_to_user(vq->iov[0].iov_base, &pkt->hdr,
> > +				     sizeof(pkt->hdr));
> > +		if (ret) {
> > +			virtio_transport_free_pkt(pkt);
> > +			vq_err(vq, "Faulted on copying pkt hdr\n");
> > +			break;
> > +		}
> > +		if (pkt->buf && pkt->len > 0) {
> > +			ret = __copy_to_user(vq->iov[1].iov_base, pkt->buf,
> > +					    pkt->len);
> > +			if (ret) {
> > +				virtio_transport_free_pkt(pkt);
> > +				vq_err(vq, "Faulted on copying pkt buf\n");
> > +				break;
> > +			}
> > +		}
> > +
> > +		vhost_add_used(vq, head, pkt->len);
> > +
> > +		virtio_transport_dec_tx_pkt(pkt);
> > +
> > +		sk = sk_vsock(pkt->trans->vsk);
> > +		/* Release refcnt taken in vhost_transport_send_pkt */
> > +		sock_put(sk);
> > +
> > +		virtio_transport_free_pkt(pkt);
> > +	}
> > +	vhost_signal(&vsock->dev, vq);
> 
> I think you should not signal if used was not updated.

Right, it is very easy to add the optimization here.

> > +	mutex_unlock(&vq->mutex);
> > +}
> > +
> > +static void vhost_transport_send_pkt_work(struct vhost_work *work)
> > +{
> > +	struct vhost_virtqueue *vq;
> > +	struct vhost_vsock *vsock;
> > +
> > +	vsock = container_of(work, struct vhost_vsock, send_pkt_work);
> > +	vq = &vsock->vqs[VSOCK_VQ_RX].vq;
> > +
> > +	vhost_transport_do_send_pkt(vsock, vq);
> > +}
> > +
> > +static int
> > +vhost_transport_send_pkt(struct vsock_sock *vsk,
> > +			 struct virtio_vsock_pkt_info *info)
> > +{
> > +	u32 src_cid, src_port, dst_cid, dst_port;
> > +	struct virtio_transport *trans;
> > +	struct virtio_vsock_pkt *pkt;
> > +	struct vhost_virtqueue *vq;
> > +	struct vhost_vsock *vsock;
> > +	u64 credit;
> > +
> > +	src_cid = vhost_transport_get_local_cid();
> 
> interestingly this is the only place cid
> is used. Shouldn't we validate it?

The local cid is a constant, how can we valicate it?

> > +	src_port = vsk->local_addr.svm_port;
> > +	dst_cid = vsk->remote_addr.svm_cid;
> > +	dst_port = vsk->remote_addr.svm_port;
> > +
> > +	/* Find the vhost_vsock according to guest context id  */
> > +	vsock = vhost_vsock_get(dst_cid);
> 
> Confused. There's a single socket per dst cid?

No, each guest has a cid, each guest has a struct vhost_vsock instance,
dst_cid tells us which struct vhost_vsock instance to use for this
packet.

> > +	if (!vsock)
> > +		return -ENODEV;
> > +
> > +	trans = vsk->trans;
> > +	vq = &vsock->vqs[VSOCK_VQ_RX].vq;
> > +
> > +	if (info->type == SOCK_STREAM) {
> > +		credit = virtio_transport_get_credit(trans);
> > +		if (info->len > credit)
> > +			info->len = credit;
> 
> Is there support for non stream sockets?
> Without credits, you get all kind of nasty
> starvation issues.

We support SOCK_STREAM and SOCK_DGRAM. The credit thing is used for
SOCK_STREAM right now. I can extend it to SOCK_DGRAM as well.

> > +	}
> > +	if (info->len > VIRTIO_VSOCK_DEFAULT_RX_BUF_SIZE)
> > +		info->len = VIRTIO_VSOCK_DEFAULT_RX_BUF_SIZE;
> > +	/* Do not send zero length OP_RW pkt*/
> > +	if (info->len == 0 && info->op == VIRTIO_VSOCK_OP_RW)
> > +		return info->len;
> > +
> > +	pkt = virtio_transport_alloc_pkt(vsk, info, info->len,
> > +					 src_cid, src_port,
> > +					 dst_cid, dst_port);
> 
> We also need global limit on amount of memory per
> socket. Even if remote is OK with getting 20G from us,
> we might not have so much kernel memory.

Yes, we need global limit. 

> > +	if (!pkt)
> > +		return -ENOMEM;
> > +
> > +	pr_debug("%s:info->len= %d\n", __func__, info->len);
> > +	/* Released in vhost_transport_do_send_pkt */
> > +	sock_hold(&trans->vsk->sk);
> > +	virtio_transport_inc_tx_pkt(pkt);
> > +
> > +	/* queue it up in vhost work */
> > +	mutex_lock(&vq->mutex);
> > +	list_add_tail(&pkt->list, &vsock->send_pkt_list);
> > +	vhost_work_queue(&vsock->dev, &vsock->send_pkt_work);
> > +	mutex_unlock(&vq->mutex);
> > +
> > +	return info->len;
> > +}
> > +
> > +static struct virtio_transport_pkt_ops vhost_ops = {
> > +	.send_pkt = vhost_transport_send_pkt,
> > +};
> > +
> > +static struct virtio_vsock_pkt *
> > +vhost_vsock_alloc_pkt(struct vhost_virtqueue *vq)
> > +{
> > +	struct virtio_vsock_pkt *pkt;
> > +	int ret;
> > +	int len;
> > +
> > +	pkt = kzalloc(sizeof(*pkt), GFP_KERNEL);
> > +	if (!pkt)
> > +		return NULL;
> > +
> > +	len = sizeof(pkt->hdr);
> > +	if (unlikely(vq->iov[0].iov_len != len)) {
> > +		vq_err(vq, "Expecting pkt->hdr = %d, got %zu bytes\n",
> > +		       len, vq->iov[0].iov_len);
> > +		kfree(pkt);
> > +		return NULL;
> > +	}
> > +	ret = __copy_from_user(&pkt->hdr, vq->iov[0].iov_base, len);
> > +	if (ret) {
> > +		vq_err(vq, "Faulted on virtio_vsock_hdr\n");
> > +		kfree(pkt);
> > +		return NULL;
> > +	}
> > +
> > +	pkt->len = pkt->hdr.len;
> > +	pkt->off = 0;
> > +
> > +	/* No payload */
> > +	if (!pkt->len)
> > +		return pkt;
> > +
> > +	/* The pkt is too big */
> > +	if (pkt->len > VIRTIO_VSOCK_MAX_PKT_BUF_SIZE) {
> > +		kfree(pkt);
> > +		return NULL;
> > +	}
> > +
> > +	pkt->buf = kmalloc(pkt->len, GFP_KERNEL);
> > +	if (!pkt->buf) {
> > +		kfree(pkt);
> > +		return NULL;
> > +	}
> > +
> > +	ret = __copy_from_user(pkt->buf, vq->iov[1].iov_base, pkt->len);
> > +	if (ret) {
> > +		vq_err(vq, "Faulted on virtio_vsock_hdr\n");
> > +		virtio_transport_free_pkt(pkt);
> > +	}
> > +
> > +	return pkt;
> > +}
> > +
> > +static void vhost_vsock_handle_ctl_kick(struct vhost_work *work)
> > +{
> > +	struct vhost_virtqueue *vq = container_of(work, struct vhost_virtqueue,
> > +						  poll.work);
> > +	struct vhost_vsock *vsock = container_of(vq->dev, struct vhost_vsock,
> > +						 dev);
> > +
> > +	pr_debug("%s vq=%p, vsock=%p\n", __func__, vq, vsock);
> > +}
> > +
> > +static void vhost_vsock_handle_tx_kick(struct vhost_work *work)
> > +{
> > +	struct vhost_virtqueue *vq = container_of(work, struct vhost_virtqueue,
> > +						  poll.work);
> > +	struct vhost_vsock *vsock = container_of(vq->dev, struct vhost_vsock,
> > +						 dev);
> > +	struct virtio_vsock_pkt *pkt;
> > +	int head, out, in;
> > +	u32 len;
> > +
> > +	mutex_lock(&vq->mutex);
> > +	vhost_disable_notify(&vsock->dev, vq);
> > +	for (;;) {
> > +		head = vhost_get_vq_desc(&vsock->dev, vq, vq->iov,
> > +					ARRAY_SIZE(vq->iov), &out, &in,
> > +					NULL, NULL);
> > +		if (head < 0)
> > +			break;
> > +
> > +		if (head == vq->num) {
> > +			if (unlikely(vhost_enable_notify(&vsock->dev, vq))) {
> > +				vhost_disable_notify(&vsock->dev, vq);
> > +				continue;
> > +			}
> > +			break;
> > +		}
> > +
> > +		pkt = vhost_vsock_alloc_pkt(vq);
> > +		if (!pkt) {
> > +			vq_err(vq, "Faulted on pkt\n");
> > +			continue;
> > +		}
> > +
> > +		len = pkt->len;
> > +		virtio_transport_recv_pkt(pkt);
> > +		vhost_add_used(vq, head, len);
> > +	}
> > +	vhost_signal(&vsock->dev, vq);
> > +	mutex_unlock(&vq->mutex);
> > +}
> > +
> > +static void vhost_vsock_handle_rx_kick(struct vhost_work *work)
> > +{
> > +	struct vhost_virtqueue *vq = container_of(work, struct vhost_virtqueue,
> > +						poll.work);
> > +	struct vhost_vsock *vsock = container_of(vq->dev, struct vhost_vsock,
> > +						 dev);
> > +
> > +	vhost_transport_do_send_pkt(vsock, vq);
> > +}
> > +
> > +static int vhost_vsock_dev_open(struct inode *inode, struct file *file)
> > +{
> > +	struct vhost_virtqueue **vqs;
> > +	struct vhost_vsock *vsock;
> > +	int ret;
> > +
> > +	vsock = kzalloc(sizeof(*vsock), GFP_KERNEL);
> > +	if (!vsock)
> > +		return -ENOMEM;
> > +
> > +	pr_debug("%s:vsock=%p\n", __func__, vsock);
> > +
> > +	vqs = kmalloc(VSOCK_VQ_MAX * sizeof(*vqs), GFP_KERNEL);
> > +	if (!vqs) {
> > +		ret = -ENOMEM;
> > +		goto out;
> > +	}
> > +
> > +	vqs[VSOCK_VQ_CTRL] = &vsock->vqs[VSOCK_VQ_CTRL].vq;
> > +	vqs[VSOCK_VQ_TX] = &vsock->vqs[VSOCK_VQ_TX].vq;
> > +	vqs[VSOCK_VQ_RX] = &vsock->vqs[VSOCK_VQ_RX].vq;
> > +	vsock->vqs[VSOCK_VQ_CTRL].vq.handle_kick = vhost_vsock_handle_ctl_kick;
> > +	vsock->vqs[VSOCK_VQ_TX].vq.handle_kick = vhost_vsock_handle_tx_kick;
> > +	vsock->vqs[VSOCK_VQ_RX].vq.handle_kick = vhost_vsock_handle_rx_kick;
> > +
> > +	ret = vhost_dev_init(&vsock->dev, vqs, VSOCK_VQ_MAX);
> > +	if (ret < 0)
> > +		goto out_vqs;
> > +
> > +	file->private_data = vsock;
> > +	INIT_LIST_HEAD(&vsock->send_pkt_list);
> > +	vhost_work_init(&vsock->send_pkt_work, vhost_transport_send_pkt_work);
> > +
> > +	mutex_lock(&vhost_vsock_mutex);
> > +	list_add_tail(&vsock->list, &vhost_vsock_list);
> > +	mutex_unlock(&vhost_vsock_mutex);
> > +	return ret;
> > +
> > +out_vqs:
> > +	kfree(vqs);
> > +out:
> > +	kfree(vsock);
> > +	return ret;
> > +}
> > +
> > +static void vhost_vsock_flush(struct vhost_vsock *vsock)
> > +{
> > +	int i;
> > +
> > +	for (i = 0; i < VSOCK_VQ_MAX; i++)
> > +		vhost_poll_flush(&vsock->vqs[i].vq.poll);
> > +	vhost_work_flush(&vsock->dev, &vsock->send_pkt_work);
> > +}
> > +
> > +static int vhost_vsock_dev_release(struct inode *inode, struct file *file)
> > +{
> > +	struct vhost_vsock *vsock = file->private_data;
> > +
> > +	mutex_lock(&vhost_vsock_mutex);
> > +	list_del(&vsock->list);
> > +	mutex_unlock(&vhost_vsock_mutex);
> > +
> > +	vhost_dev_stop(&vsock->dev);
> > +	vhost_vsock_flush(vsock);
> > +	vhost_dev_cleanup(&vsock->dev, false);
> > +	kfree(vsock->dev.vqs);
> > +	kfree(vsock);
> > +	return 0;
> > +}
> > +
> > +static int vhost_vsock_set_cid(struct vhost_vsock *vsock, u32 guest_cid)
> > +{
> > +	mutex_lock(&vhost_vsock_mutex);
> > +	vsock->guest_cid = guest_cid;
> > +	pr_debug("%s:guest_cid=%d\n", __func__, guest_cid);
> > +	mutex_unlock(&vhost_vsock_mutex);
> > +
> > +	return 0;
> > +}
> > +
> > +static long vhost_vsock_dev_ioctl(struct file *f, unsigned int ioctl,
> > +				  unsigned long arg)
> > +{
> > +	struct vhost_vsock *vsock = f->private_data;
> > +	void __user *argp = (void __user *)arg;
> > +	u64 __user *featurep = argp;
> > +	u32 __user *cidp = argp;
> > +	u32 guest_cid;
> > +	u64 features;
> > +	int r;
> > +
> > +	switch (ioctl) {
> > +	case VHOST_VSOCK_SET_GUEST_CID:
> > +		if (get_user(guest_cid, cidp))
> > +			return -EFAULT;
> > +		return vhost_vsock_set_cid(vsock, guest_cid);
> > +	case VHOST_GET_FEATURES:
> > +		features = VHOST_VSOCK_FEATURES;
> > +		if (copy_to_user(featurep, &features, sizeof(features)))
> > +			return -EFAULT;
> > +		return 0;
> > +	case VHOST_SET_FEATURES:
> > +		if (copy_from_user(&features, featurep, sizeof(features)))
> > +			return -EFAULT;
> > +		return 0;
> > +	default:
> > +		mutex_lock(&vsock->dev.mutex);
> > +		r = vhost_dev_ioctl(&vsock->dev, ioctl, argp);
> > +		if (r == -ENOIOCTLCMD)
> > +			r = vhost_vring_ioctl(&vsock->dev, ioctl, argp);
> > +		else
> > +			vhost_vsock_flush(vsock);
> > +		mutex_unlock(&vsock->dev.mutex);
> > +		return r;
> > +	}
> > +}
> > +
> > +static const struct file_operations vhost_vsock_fops = {
> > +	.owner          = THIS_MODULE,
> > +	.open           = vhost_vsock_dev_open,
> > +	.release        = vhost_vsock_dev_release,
> > +	.llseek		= noop_llseek,
> > +	.unlocked_ioctl = vhost_vsock_dev_ioctl,
> > +};
> > +
> > +static struct miscdevice vhost_vsock_misc = {
> > +	.minor = MISC_DYNAMIC_MINOR,
> > +	.name = "vhost-vsock",
> > +	.fops = &vhost_vsock_fops,
> > +};
> > +
> > +static int
> > +vhost_transport_socket_init(struct vsock_sock *vsk, struct vsock_sock *psk)
> > +{
> > +	struct virtio_transport *trans;
> > +	int ret;
> > +
> > +	ret = virtio_transport_do_socket_init(vsk, psk);
> > +	if (ret)
> > +		return ret;
> > +
> > +	trans = vsk->trans;
> > +	trans->ops = &vhost_ops;
> > +
> > +	return ret;
> > +}
> > +
> > +static struct vsock_transport vhost_transport = {
> > +	.get_local_cid            = vhost_transport_get_local_cid,
> > +
> > +	.init                     = vhost_transport_socket_init,
> > +	.destruct                 = virtio_transport_destruct,
> > +	.release                  = virtio_transport_release,
> > +	.connect                  = virtio_transport_connect,
> > +	.shutdown                 = virtio_transport_shutdown,
> > +
> > +	.dgram_enqueue            = virtio_transport_dgram_enqueue,
> > +	.dgram_dequeue            = virtio_transport_dgram_dequeue,
> > +	.dgram_bind               = virtio_transport_dgram_bind,
> > +	.dgram_allow              = virtio_transport_dgram_allow,
> > +
> > +	.stream_enqueue           = virtio_transport_stream_enqueue,
> > +	.stream_dequeue           = virtio_transport_stream_dequeue,
> > +	.stream_has_data          = virtio_transport_stream_has_data,
> > +	.stream_has_space         = virtio_transport_stream_has_space,
> > +	.stream_rcvhiwat          = virtio_transport_stream_rcvhiwat,
> > +	.stream_is_active         = virtio_transport_stream_is_active,
> > +	.stream_allow             = virtio_transport_stream_allow,
> > +
> > +	.notify_poll_in           = virtio_transport_notify_poll_in,
> > +	.notify_poll_out          = virtio_transport_notify_poll_out,
> > +	.notify_recv_init         = virtio_transport_notify_recv_init,
> > +	.notify_recv_pre_block    = virtio_transport_notify_recv_pre_block,
> > +	.notify_recv_pre_dequeue  = virtio_transport_notify_recv_pre_dequeue,
> > +	.notify_recv_post_dequeue = virtio_transport_notify_recv_post_dequeue,
> > +	.notify_send_init         = virtio_transport_notify_send_init,
> > +	.notify_send_pre_block    = virtio_transport_notify_send_pre_block,
> > +	.notify_send_pre_enqueue  = virtio_transport_notify_send_pre_enqueue,
> > +	.notify_send_post_enqueue = virtio_transport_notify_send_post_enqueue,
> > +
> > +	.set_buffer_size          = virtio_transport_set_buffer_size,
> > +	.set_min_buffer_size      = virtio_transport_set_min_buffer_size,
> > +	.set_max_buffer_size      = virtio_transport_set_max_buffer_size,
> > +	.get_buffer_size          = virtio_transport_get_buffer_size,
> > +	.get_min_buffer_size      = virtio_transport_get_min_buffer_size,
> > +	.get_max_buffer_size      = virtio_transport_get_max_buffer_size,
> > +};
> > +
> > +static int __init vhost_vsock_init(void)
> > +{
> > +	int ret;
> > +
> > +	ret = vsock_core_init(&vhost_transport);
> > +	if (ret < 0)
> > +		return ret;
> > +	return misc_register(&vhost_vsock_misc);
> > +};
> > +
> > +static void __exit vhost_vsock_exit(void)
> > +{
> > +	misc_deregister(&vhost_vsock_misc);
> > +	vsock_core_exit();
> > +};
> > +
> > +module_init(vhost_vsock_init);
> > +module_exit(vhost_vsock_exit);
> > +MODULE_LICENSE("GPL v2");
> > +MODULE_AUTHOR("Asias He");
> > +MODULE_DESCRIPTION("vhost transport for vsock ");
> > diff --git a/drivers/vhost/vsock.h b/drivers/vhost/vsock.h
> > new file mode 100644
> > index 0000000..0ddb107
> > --- /dev/null
> > +++ b/drivers/vhost/vsock.h
> > @@ -0,0 +1,4 @@
> > +#ifndef VHOST_VSOCK_H
> > +#define VHOST_VSOCK_H
> > +#define VHOST_VSOCK_SET_GUEST_CID _IOW(VHOST_VIRTIO, 0x60, __u32)
> 
> No SET without GET please.

But the GET is useless here. We know the guest cid in userspace already.

> > +#endif
> > -- 
> > 1.8.1.4

-- 
Asias