Skip to content

Commit

Permalink
vhost: vsock: kick send_pkt worker once device is started
Browse files Browse the repository at this point in the history
commit 0b841030625cde5f784dd62aec72d6a766faae70 upstream.

Ning Bo reported an abnormal 2-second gap when booting Kata container [1].
The unconditional timeout was caused by VSOCK_DEFAULT_CONNECT_TIMEOUT of
connecting from the client side. The vhost vsock client tries to connect
an initializing virtio vsock server.

The abnormal flow looks like:
host-userspace           vhost vsock                       guest vsock
==============           ===========                       ============
connect()     -------->  vhost_transport_send_pkt_work()   initializing
   |                     vq->private_data==NULL
   |                     will not be queued
   V
schedule_timeout(2s)
                         vhost_vsock_start()  <---------   device ready
                         set vq->private_data

wait for 2s and failed
connect() again          vq->private_data!=NULL         recv connecting pkt

Details:
1. Host userspace sends a connect pkt, at that time, guest vsock is under
   initializing, hence the vhost_vsock_start has not been called. So
   vq->private_data==NULL, and the pkt is not been queued to send to guest
2. Then it sleeps for 2s
3. After guest vsock finishes initializing, vq->private_data is set
4. When host userspace wakes up after 2s, send connecting pkt again,
   everything is fine.

As suggested by Stefano Garzarella, this fixes it by additional kicking the
send_pkt worker in vhost_vsock_start once the virtio device is started. This
makes the pending pkt sent again.

After this patch, kata-runtime (with vsock enabled) boot time is reduced
from 3s to 1s on a ThunderX2 arm64 server.

[1] kata-containers/runtime#1917

Reported-by: Ning Bo <n.b@live.com>
Suggested-by: Stefano Garzarella <sgarzare@redhat.com>
Signed-off-by: Jia He <justin.he@arm.com>
Link: https://lore.kernel.org/r/20200501043840.186557-1-justin.he@arm.com
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  • Loading branch information
justin-he authored and Gitea committed Jul 13, 2020
1 parent 0b4653e commit bea31d0
Showing 1 changed file with 5 additions and 0 deletions.
5 changes: 5 additions & 0 deletions drivers/vhost/vsock.c
Original file line number Diff line number Diff line change
Expand Up @@ -460,6 +460,11 @@ static int vhost_vsock_start(struct vhost_vsock *vsock)
mutex_unlock(&vq->mutex);
}

/* Some packets may have been queued before the device was started,
* let's kick the send worker to send them.
*/
vhost_work_queue(&vsock->dev, &vsock->send_pkt_work);

mutex_unlock(&vsock->dev.mutex);
return 0;

Expand Down

0 comments on commit bea31d0

Please sign in to comment.