From: Jia He justin.he@arm.com
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] https://github.com/kata-containers/runtime/issues/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
--- drivers/vhost/vsock.c | 5 +++++ 1 file changed, 5 insertions(+)
--- a/drivers/vhost/vsock.c +++ b/drivers/vhost/vsock.c @@ -460,6 +460,11 @@ static int vhost_vsock_start(struct vhos 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;