On Thu, Nov 28, 2019 at 07:26:47PM +0800, ning....@zte.com.cn wrote: > Let me describe the issue with an example via `nc-vsock`: > > Let's assume the Guest cid is 3. > execute 'rmmod vmw_vsock_virtio_transport' in Guest, > then execute 'while true; do nc-vsock 3 1234' in Host. > > Host Guest > # rmmod vmw_vsock_virtio_transport > > # while true; do ./nc-vsock 3 1234; done > (after 2 second) > connect: Connection timed out > (after 2 second) > connect: Connection timed out > ... > > # modprobe vmw_vsock_virtio_transport > > connect: Connection reset by peer > connect: Connection reset by peer > connect: Connection reset by peer > ... > > # nc-vsock -l 1234 > Connetion from cid 2 port ***... > (stop printing) > > > The above process simulates the communication process between > the `kata-runtime` and `kata-agent` after starting the Guest. > In order to connect to `kata-agent` as soon as possible, > `kata-runtime` will continuously try to connect to `kata-agent` in a loop. > see > https://github.com/kata-containers/runtime/blob/d054556f60f092335a22a288011fa29539ad4ccc/vendor/github.com/kata-containers/agent/protocols/client/client.go#L327 > But when the vsock device in the Guest is not ready, the connection > will block for 2 seconds. This situation actually slows down > the entire startup time of `kata-runtime`.
This can be done efficiently as follows: 1. kata-runtime listens on a vsock port 2. kata-agent-port=PORT is added to the kernel command-line options 3. kata-agent parses the port number and connects to the host This eliminates the reconnection attempts. > > I think that adding a QMP event is working around the issue rather than > > fixing the root cause. This is probably a vhost_vsock.ko problem and > > should be fixed there. > > After looking at the source code of vhost_vsock.ko, > I think it is possible to optimize the logic here too. > The simple patch is as follows. Do you think the modification is appropriate? > > diff --git a/drivers/vhost/vsock.c b/drivers/vhost/vsock.c > index 9f57736f..8fad67be 100644 > --- a/drivers/vhost/vsock.c > +++ b/drivers/vhost/vsock.c > @@ -51,6 +51,7 @@ struct vhost_vsock { > atomic_t queued_replies; > > u32 guest_cid; > + u32 state; > }; > > static u32 vhost_transport_get_local_cid(void) > @@ -497,6 +541,7 @@ static int vhost_vsock_start(struct vhost_vsock *vsock) > > mutex_unlock(&vq->mutex); > } > + vsock->state = 1; > > mutex_unlock(&vsock->dev.mutex); > return 0; > @@ -535,6 +580,7 @@ static int vhost_vsock_stop(struct vhost_vsock *vsock) > vq->private_data = NULL; > mutex_unlock(&vq->mutex); > } > + vsock->state = 0; > > err: > mutex_unlock(&vsock->dev.mutex); > @@ -786,6 +832,27 @@ static struct miscdevice vhost_vsock_misc = { > .fops = &vhost_vsock_fops, > }; > > +int vhost_transport_connect(struct vsock_sock *vsk) { > + struct vhost_vsock *vsock; > + > + rcu_read_lock(); > + > + /* Find the vhost_vsock according to guest context id */ > + vsock = vhost_vsock_get(vsk->remote_addr.svm_cid); > + if (!vsock) { > + rcu_read_unlock(); > + return -ENODEV; > + } > + > + rcu_read_unlock(); > + > + if (vsock->state == 1) { > + return virtio_transport_connect(vsk); > + } else { > + return -ECONNRESET; > + } > +} > + > static struct virtio_transport vhost_transport = { > .transport = { > .get_local_cid = vhost_transport_get_local_cid, > @@ -793,7 +860,7 @@ static struct virtio_transport vhost_transport = { > .init = virtio_transport_do_socket_init, > .destruct = virtio_transport_destruct, > .release = virtio_transport_release, > - .connect = virtio_transport_connect, > + .connect = vhost_transport_connect, > .shutdown = virtio_transport_shutdown, > .cancel_pkt = vhost_transport_cancel_pkt, I'm not keen on adding a special case for vhost_vsock.ko connect. Userspace APIs to avoid the 2 second wait already exist: 1. The SO_VM_SOCKETS_CONNECT_TIMEOUT socket option controls the connect timeout for this socket. 2. Non-blocking connect allows the userspace process to do other things while a connection attempt is being made. But the best solution is the one I mentioned above. Stefan
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