Commit 0b841030 authored by Jia He's avatar Jia He Committed by Michael S. Tsirkin

vhost: vsock: kick send_pkt worker once device is started

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/1917Reported-by: default avatarNing Bo <n.b@live.com>
Suggested-by: default avatarStefano Garzarella <sgarzare@redhat.com>
Signed-off-by: default avatarJia He <justin.he@arm.com>
Link: https://lore.kernel.org/r/20200501043840.186557-1-justin.he@arm.comSigned-off-by: default avatarMichael S. Tsirkin <mst@redhat.com>
Reviewed-by: default avatarStefano Garzarella <sgarzare@redhat.com>
parent 90b5feb8
...@@ -543,6 +543,11 @@ static int vhost_vsock_start(struct vhost_vsock *vsock) ...@@ -543,6 +543,11 @@ static int vhost_vsock_start(struct vhost_vsock *vsock)
mutex_unlock(&vq->mutex); 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); mutex_unlock(&vsock->dev.mutex);
return 0; return 0;
......
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