$ ovs-vsctl show:
Bridge "switch1"
    Port "switch1"
        Interface "switch1"
            type: internal
    Port "1.switch1"
        Interface "1.switch1"
            type: dpdk
            options: {dpdk-devargs="0000:0b:00.0"}
    Port "0.switch1"
        Interface "0.vm"
            type: dpdkvhostuserclient
            options: {vhost-server-path="/opt/oa/vhost/0.vm.sock"}


The relevant excerpt from the XML of my VM is:

<?xml version="1.0" ?>
<domain type="kvm" xmlns:ns0="http://libvirt.org/schemas/domain/qemu/1.0">
 <!-- [...]  -->
 <devices>
    <emulator>/opt/oa/bin/qemu-system-x86_64</emulator>
    <!-- [...]  -->
    <interface type="vhostuser">
      <script path="/opt/oa/etc/qemu-ifup"/>
      <source mode="server" path="/opt/oa/vhost/0.vm.sock" type="unix"/>
      <mac address="52:54:00:41:37:08"/>
      <model type="virtio"/>
      <driver queues="1">
        <host csum="off"/>
      </driver>
    </interface>
    <!-- [...]  -->
  </devices>
  <ns0:commandline>
    <ns0:arg value="-object"/>
    <ns0:arg value="memory-backend-file,id=mem,size=2G,mem-path=/dev/hugepages,share=on"/>
    <ns0:arg value="-numa"/>
    <ns0:arg value="node,memdev=mem"/>
    <ns0:arg value="-mem-prealloc"/>
  </ns0:commandline>
</domain>


Now, if I try to start my VM, I get the following error and the VM is not started at all:
$ virsh create vm.xml
error: Failed to create domain from vm.xml
error: unsupported configuration: scripts are not supported on interfaces of type vhostuser


The logs from libvirtd.log say:
2018-02-22 09:18:24.982+0000: 2033: warning : qemuProcessStartWarnShmem:4539 : Detected vhost-user interface without any shared memory, the interface might not be operational
2018-02-22 09:18:24.982+0000: 2033: error : qemuBuildHostNetStr:3894 : unsupported configuration: scripts are not supported on interfaces of type vhostuser

The logs from qemu simply say:
2018-02-22 09:26:15.857+0000: shutting down, reason=failed

And finally, ovs-vswitchd.log:
2018-02-22T09:18:24.715Z|00328|dpdk|INFO|VHOST_CONFIG: vhost-user client: socket created, fd: 51
2018-02-22T09:18:24.716Z|00329|netdev_dpdk|INFO|vHost User device '0.vm' created in 'client' mode, using client socket '/opt/oa/vhost/0.vm.sock'
2018-02-22T09:18:24.718Z|00330|dpdk|WARN|VHOST_CONFIG: failed to connect to /opt/oa/vhost/0.vm.sock: No such file or directory
2018-02-22T09:18:24.718Z|00331|dpdk|INFO|VHOST_CONFIG: /opt/oa/vhost/0.vm.sock: reconnecting...
2018-02-22T09:18:24.718Z|00332|bridge|INFO|bridge switch1: added interface 0.vm on port 5