Subject: Re: [PATCH v1 2/3] Provides multiple submits and asynchronous notifications.

From: "Michael S. Tsirkin" <[email-masked]>
Date: Wed, 7 Apr 2010 11:18:00 +0300

On Wed, Apr 07, 2010 at 09:36:36AM +0800, Xin, Xiaohui wrote:
> Michael,
> > > >>>> 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
> 
> > >>Yes, I think this will work.
> 
> >> Thanks, so do you have the function to recompute the log info in your hand that I can
> >>use? I have weakly remembered that you have noticed it before some time.
> 
> >Doesn't just rerunning vhost_get_vq_desc work?
> 
> Am I missing something here?
> The vhost_get_vq_desc() looks in vq, and finds the first available buffers, and converts it
> to an iovec. I think the first available buffer is not the buffers in the async queue, so I
> think rerunning vhost_get_vq_desc() cannot work.
> 
> Thanks
> Xiaohui

Right, but we can move the head back, so we'll find the same buffers
again, or add a variant of vhost_get_vq_desc that will process
descriptors already consumed.

> > > > 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