Date:	Fri, 2 Apr 2010 10:16:16 +0800
From:	"Xin, Xiaohui" <xiaohui.xin@...el.com>
To:	"Michael S. Tsirkin" <mst@...hat.com>
CC:	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"kvm@...r.kernel.org" <kvm@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"mingo@...e.hu" <mingo@...e.hu>,
	"jdike@...toit.com" <jdike@...toit.com>
Subject: RE: [PATCH v1 2/3] Provides multiple submits and asynchronous
	notifications.


>> For the write logging, do you have a function in hand that we can
>> recompute the log? If that, I think I can use it to recompute the
>>log info when the logging is suddenly enabled.
>> For the outstanding requests, do you mean all the user buffers have
>>submitted before the logging ioctl changed? That may be a lot, and
>> some of them are still in NIC ring descriptors. Waiting them to be
>>finished may be need some time. I think when logging ioctl changed,
>> then the logging is changed just after that is also reasonable.

>The key point is that after loggin ioctl returns, any
>subsequent change to memory must be logged. It does not
>matter when was the request submitted, otherwise we will
>get memory corruption on migration.

The change to memory happens when vhost_add_used_and_signal(), right?
So after ioctl returns, just recompute the log info to the events in the async queue,
is ok. Since the ioctl and write log operations are all protected by vq->mutex.

Thanks
Xiaohui

> Thanks
> Xiaohui
> 
>  drivers/vhost/net.c   |  189 +++++++++++++++++++++++++++++++++++++++++++++++--
>  drivers/vhost/vhost.h |   10 +++
>  2 files changed, 192 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
> index 22d5fef..2aafd90 100644
> --- a/drivers/vhost/net.c
> +++ b/drivers/vhost/net.c
> @@ -17,11 +17,13 @@
>  #include <linux/workqueue.h>
>  #include <linux/rcupdate.h>
>  #include <linux/file.h>
> +#include <linux/aio.h>
>  
>  #include <linux/net.h>
>  #include <linux/if_packet.h>
>  #include <linux/if_arp.h>
>  #include <linux/if_tun.h>
> +#include <linux/mpassthru.h>
>  
>  #include <net/sock.h>
>  
> @@ -47,6 +49,7 @@ struct vhost_net {
>  	struct vhost_dev dev;
>  	struct vhost_virtqueue vqs[VHOST_NET_VQ_MAX];
>  	struct vhost_poll poll[VHOST_NET_VQ_MAX];
> +	struct kmem_cache       *cache;
>  	/* Tells us whether we are polling a socket for TX.
>  	 * We only do this when socket buffer fills up.
>  	 * Protected by tx vq lock. */
> @@ -91,11 +94,88 @@ static void tx_poll_start(struct vhost_net *net, struct socket *sock)
>  	net->tx_poll_state = VHOST_NET_POLL_STARTED;
>  }
>  
> +struct kiocb *notify_dequeue(struct vhost_virtqueue *vq)
> +{
> +	struct kiocb *iocb = NULL;
> +	unsigned long flags;
> +
> +	spin_lock_irqsave(&vq->notify_lock, flags);
> +	if (!list_empty(&vq->notifier)) {
> +		iocb = list_first_entry(&vq->notifier,
> +				struct kiocb, ki_list);
> +		list_del(&iocb->ki_list);
> +	}
> +	spin_unlock_irqrestore(&vq->notify_lock, flags);
> +	return iocb;
> +}
> +
> +static void handle_async_rx_events_notify(struct vhost_net *net,
> +					struct vhost_virtqueue *vq)
> +{
> +	struct kiocb *iocb = NULL;
> +	struct vhost_log *vq_log = NULL;
> +	int rx_total_len = 0;
> +	int log, size;
> +
> +	if (vq->link_state != VHOST_VQ_LINK_ASYNC)
> +		return;
> +
> +	if (vq->receiver)
> +		vq->receiver(vq);
> +
> +	vq_log = unlikely(vhost_has_feature(
> +				&net->dev, VHOST_F_LOG_ALL)) ? vq->log : NULL;
> +	while ((iocb = notify_dequeue(vq)) != NULL) {
> +		vhost_add_used_and_signal(&net->dev, vq,
> +				iocb->ki_pos, iocb->ki_nbytes);
> +		log = (int)iocb->ki_user_data;
> +		size = iocb->ki_nbytes;
> +		rx_total_len += iocb->ki_nbytes;
> +
> +		if (iocb->ki_dtor)
> +			iocb->ki_dtor(iocb);
> +		kmem_cache_free(net->cache, iocb);
> +
> +		if (unlikely(vq_log))
> +			vhost_log_write(vq, vq_log, log, size);
> +		if (unlikely(rx_total_len >= VHOST_NET_WEIGHT)) {
> +			vhost_poll_queue(&vq->poll);
> +			break;
> +		}
> +	}
> +}
> +
> +static void handle_async_tx_events_notify(struct vhost_net *net,
> +					struct vhost_virtqueue *vq)
> +{
> +	struct kiocb *iocb = NULL;
> +	int tx_total_len = 0;
> +
> +	if (vq->link_state != VHOST_VQ_LINK_ASYNC)
> +		return;
> +
> +	while ((iocb = notify_dequeue(vq)) != NULL) {
> +		vhost_add_used_and_signal(&net->dev, vq,
> +				iocb->ki_pos, 0);
> +		tx_total_len += iocb->ki_nbytes;
> +
> +		if (iocb->ki_dtor)
> +			iocb->ki_dtor(iocb);
> +
> +		kmem_cache_free(net->cache, iocb);
> +		if (unlikely(tx_total_len >= VHOST_NET_WEIGHT)) {
> +			vhost_poll_queue(&vq->poll);
> +			break;
> +		}
> +	}
> +}
> +
>  /* Expects to be always run from workqueue - which acts as
>   * read-size critical section for our kind of RCU. */
>  static void handle_tx(struct vhost_net *net)
>  {
>  	struct vhost_virtqueue *vq = &net->dev.vqs[VHOST_NET_VQ_TX];
> +	struct kiocb *iocb = NULL;
>  	unsigned head, out, in, s;
>  	struct msghdr msg = {
>  		.msg_name = NULL,
> @@ -124,6 +204,8 @@ static void handle_tx(struct vhost_net *net)
>  		tx_poll_stop(net);
>  	hdr_size = vq->hdr_size;
>  
> +	handle_async_tx_events_notify(net, vq);
> +
>  	for (;;) {
>  		head = vhost_get_vq_desc(&net->dev, vq, vq->iov,
>  					 ARRAY_SIZE(vq->iov),
> @@ -151,6 +233,15 @@ static void handle_tx(struct vhost_net *net)
>  		/* Skip header. TODO: support TSO. */
>  		s = move_iovec_hdr(vq->iov, vq->hdr, hdr_size, out);
>  		msg.msg_iovlen = out;
> +
> +		if (vq->link_state == VHOST_VQ_LINK_ASYNC) {
> +			iocb = kmem_cache_zalloc(net->cache, GFP_KERNEL);
> +			if (!iocb)
> +				break;
> +			iocb->ki_pos = head;
> +			iocb->private = (void *)vq;
> +		}
> +
>  		len = iov_length(vq->iov, out);
>  		/* Sanity check */
>  		if (!len) {
> @@ -160,12 +251,16 @@ static void handle_tx(struct vhost_net *net)
>  			break;
>  		}
>  		/* TODO: Check specific error and bomb out unless ENOBUFS? */
> -		err = sock->ops->sendmsg(NULL, sock, &msg, len);
> +		err = sock->ops->sendmsg(iocb, sock, &msg, len);
>  		if (unlikely(err < 0)) {
>  			vhost_discard_vq_desc(vq);
>  			tx_poll_start(net, sock);
>  			break;
>  		}
> +
> +		if (vq->link_state == VHOST_VQ_LINK_ASYNC)
> +			continue;
> +
>  		if (err != len)
>  			pr_err("Truncated TX packet: "
>  			       " len %d != %zd\n", err, len);
> @@ -177,6 +272,8 @@ static void handle_tx(struct vhost_net *net)
>  		}
>  	}
>  
> +	handle_async_tx_events_notify(net, vq);
> +
>  	mutex_unlock(&vq->mutex);
>  	unuse_mm(net->dev.mm);
>  }
> @@ -186,6 +283,7 @@ static void handle_tx(struct vhost_net *net)
>  static void handle_rx(struct vhost_net *net)
>  {
>  	struct vhost_virtqueue *vq = &net->dev.vqs[VHOST_NET_VQ_RX];
> +	struct kiocb *iocb = NULL;
>  	unsigned head, out, in, log, s;
>  	struct vhost_log *vq_log;
>  	struct msghdr msg = {
> @@ -206,7 +304,8 @@ static void handle_rx(struct vhost_net *net)
>  	int err;
>  	size_t hdr_size;
>  	struct socket *sock = rcu_dereference(vq->private_data);
> -	if (!sock || skb_queue_empty(&sock->sk->sk_receive_queue))
> +	if (!sock || (skb_queue_empty(&sock->sk->sk_receive_queue) &&
> +			vq->link_state == VHOST_VQ_LINK_SYNC))
>  		return;
>  
>  	use_mm(net->dev.mm);
> @@ -214,9 +313,18 @@ static void handle_rx(struct vhost_net *net)
>  	vhost_disable_notify(vq);
>  	hdr_size = vq->hdr_size;
>  
> -	vq_log = unlikely(vhost_has_feature(&net->dev, VHOST_F_LOG_ALL)) ?
> +	/* In async cases, for write logging, the simple way is to get
> +	 * the log info always, and really logging is decided later.
> +	 * Thus, when logging enabled, we can get log, and when logging
> +	 * disabled, we can get log disabled accordingly.
> +	 */
> +
> +	vq_log = unlikely(vhost_has_feature(&net->dev, VHOST_F_LOG_ALL)) |
> +		(vq->link_state == VHOST_VQ_LINK_ASYNC) ?
>  		vq->log : NULL;
>  
> +	handle_async_rx_events_notify(net, vq);
> +
>  	for (;;) {
>  		head = vhost_get_vq_desc(&net->dev, vq, vq->iov,
>  					 ARRAY_SIZE(vq->iov),
> @@ -245,6 +353,14 @@ static void handle_rx(struct vhost_net *net)
>  		s = move_iovec_hdr(vq->iov, vq->hdr, hdr_size, in);
>  		msg.msg_iovlen = in;
>  		len = iov_length(vq->iov, in);
> +		if (vq->link_state == VHOST_VQ_LINK_ASYNC) {
> +			iocb = kmem_cache_zalloc(net->cache, GFP_KERNEL);
> +			if (!iocb)
> +				break;
> +			iocb->private = vq;
> +			iocb->ki_pos = head;
> +			iocb->ki_user_data = log;
> +		}
>  		/* Sanity check */
>  		if (!len) {
>  			vq_err(vq, "Unexpected header len for RX: "
> @@ -252,13 +368,18 @@ static void handle_rx(struct vhost_net *net)
>  			       iov_length(vq->hdr, s), hdr_size);
>  			break;
>  		}
> -		err = sock->ops->recvmsg(NULL, sock, &msg,
> +
> +		err = sock->ops->recvmsg(iocb, sock, &msg,
>  					 len, MSG_DONTWAIT | MSG_TRUNC);
>  		/* TODO: Check specific error and bomb out unless EAGAIN? */
>  		if (err < 0) {
>  			vhost_discard_vq_desc(vq);
>  			break;
>  		}
> +
> +		if (vq->link_state == VHOST_VQ_LINK_ASYNC)
> +			continue;
> +
>  		/* TODO: Should check and handle checksum. */
>  		if (err > len) {
>  			pr_err("Discarded truncated rx packet: "
> @@ -284,10 +405,13 @@ static void handle_rx(struct vhost_net *net)
>  		}
>  	}
>  
> +	handle_async_rx_events_notify(net, vq);
> +
>  	mutex_unlock(&vq->mutex);
>  	unuse_mm(net->dev.mm);
>  }
>  
> +
>  static void handle_tx_kick(struct work_struct *work)
>  {
>  	struct vhost_virtqueue *vq;
> @@ -338,6 +462,7 @@ static int vhost_net_open(struct inode *inode, struct file *f)
>  	vhost_poll_init(n->poll + VHOST_NET_VQ_TX, handle_tx_net, POLLOUT);
>  	vhost_poll_init(n->poll + VHOST_NET_VQ_RX, handle_rx_net, POLLIN);
>  	n->tx_poll_state = VHOST_NET_POLL_DISABLED;
> +	n->cache = NULL;
>  	return 0;
>  }
>  
> @@ -398,6 +523,17 @@ static void vhost_net_flush(struct vhost_net *n)
>  	vhost_net_flush_vq(n, VHOST_NET_VQ_RX);
>  }
>  
> +static void vhost_notifier_cleanup(struct vhost_net *n)
> +{
> +	struct vhost_virtqueue *vq = &n->dev.vqs[VHOST_NET_VQ_RX];
> +	struct kiocb *iocb = NULL;
> +	if (n->cache) {
> +		while ((iocb = notify_dequeue(vq)) != NULL)
> +			kmem_cache_free(n->cache, iocb);
> +		kmem_cache_destroy(n->cache);
> +	}
> +}
> +
>  static int vhost_net_release(struct inode *inode, struct file *f)
>  {
>  	struct vhost_net *n = f->private_data;
> @@ -414,6 +550,7 @@ static int vhost_net_release(struct inode *inode, struct file *f)
>  	/* We do an extra flush before freeing memory,
>  	 * since jobs can re-queue themselves. */
>  	vhost_net_flush(n);
> +	vhost_notifier_cleanup(n);
>  	kfree(n);
>  	return 0;
>  }
> @@ -462,7 +599,19 @@ static struct socket *get_tun_socket(int fd)
>  	return sock;
>  }
>  
> -static struct socket *get_socket(int fd)
> +static struct socket *get_mp_socket(int fd)
> +{
> +	struct file *file = fget(fd);
> +	struct socket *sock;
> +	if (!file)
> +		return ERR_PTR(-EBADF);
> +	sock = mp_get_socket(file);
> +	if (IS_ERR(sock))
> +		fput(file);
> +	return sock;
> +}
> +
> +static struct socket *get_socket(struct vhost_virtqueue *vq, int fd)
>  {
>  	struct socket *sock;
>  	if (fd == -1)
> @@ -473,9 +622,31 @@ static struct socket *get_socket(int fd)
>  	sock = get_tun_socket(fd);
>  	if (!IS_ERR(sock))
>  		return sock;
> +	sock = get_mp_socket(fd);
> +	if (!IS_ERR(sock)) {
> +		vq->link_state = VHOST_VQ_LINK_ASYNC;
> +		return sock;
> +	}
>  	return ERR_PTR(-ENOTSOCK);
>  }
>  
> +static void vhost_init_link_state(struct vhost_net *n, int index)
> +{
> +	struct vhost_virtqueue *vq = n->vqs + index;
> +
> +	WARN_ON(!mutex_is_locked(&vq->mutex));
> +	if (vq->link_state == VHOST_VQ_LINK_ASYNC) {
> +		vq->receiver = NULL;
> +		INIT_LIST_HEAD(&vq->notifier);
> +		spin_lock_init(&vq->notify_lock);
> +		if (!n->cache) {
> +			n->cache = kmem_cache_create("vhost_kiocb",
> +					sizeof(struct kiocb), 0,
> +					SLAB_HWCACHE_ALIGN, NULL);
> +		}
> +	}
> +}
> +
>  static long vhost_net_set_backend(struct vhost_net *n, unsigned index, int fd)
>  {
>  	struct socket *sock, *oldsock;
> @@ -493,12 +664,15 @@ static long vhost_net_set_backend(struct vhost_net *n, unsigned index, int fd)
>  	}
>  	vq = n->vqs + index;
>  	mutex_lock(&vq->mutex);
> -	sock = get_socket(fd);
> +	vq->link_state = VHOST_VQ_LINK_SYNC;
> +	sock = get_socket(vq, fd);
>  	if (IS_ERR(sock)) {
>  		r = PTR_ERR(sock);
>  		goto err;
>  	}
>  
> +	vhost_init_link_state(n, index);
> +
>  	/* start polling new socket */
>  	oldsock = vq->private_data;
>  	if (sock == oldsock)
> @@ -507,8 +681,8 @@ static long vhost_net_set_backend(struct vhost_net *n, unsigned index, int fd)
>  	vhost_net_disable_vq(n, vq);
>  	rcu_assign_pointer(vq->private_data, sock);
>  	vhost_net_enable_vq(n, vq);
> -	mutex_unlock(&vq->mutex);
>  done:
> +	mutex_unlock(&vq->mutex);
>  	mutex_unlock(&n->dev.mutex);
>  	if (oldsock) {
>  		vhost_net_flush_vq(n, index);
> @@ -516,6 +690,7 @@ done:
>  	}
>  	return r;
>  err:
> +	mutex_unlock(&vq->mutex);
>  	mutex_unlock(&n->dev.mutex);
>  	return r;
>  }
> diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
> index d1f0453..cffe39a 100644
> --- a/drivers/vhost/vhost.h
> +++ b/drivers/vhost/vhost.h
> @@ -43,6 +43,11 @@ struct vhost_log {
>  	u64 len;
>  };
>  
> +enum vhost_vq_link_state {
> +	VHOST_VQ_LINK_SYNC = 	0,
> +	VHOST_VQ_LINK_ASYNC = 	1,
> +};
> +
>  /* The virtqueue structure describes a queue attached to a device. */
>  struct vhost_virtqueue {
>  	struct vhost_dev *dev;
> @@ -96,6 +101,11 @@ struct vhost_virtqueue {
>  	/* Log write descriptors */
>  	void __user *log_base;
>  	struct vhost_log log[VHOST_NET_MAX_SG];
> +	/*Differiate async socket for 0-copy from normal*/
> +	enum vhost_vq_link_state link_state;
> +	struct list_head notifier;
> +	spinlock_t notify_lock;
> +	void (*receiver)(struct vhost_virtqueue *);
>  };
>  
>  struct vhost_dev {
> -- 
> 1.5.4.4
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