[ovs-discuss] cannot start a VM with vhostuser interfaces

Riccardo Ravaioli riccardoravaioli at gmail.com
Thu Feb 22 16:58:35 UTC 2018


I'm having trouble starting a VM with vhostuser interfaces and I'm not sure
if it's due to my configuration of libvirt or of openvswitch.

I have a simple configuration where a VM running Debian has 1 vhostuser
interface plugged into an OVS switch where a DPDK interface is already
plugged in.
$ 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">
 <!-- [...]  -->
    <!-- [...]  -->
    <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"/>
    <!-- [...]  -->
    <ns0:arg value="-object"/>
    <ns0:arg value="memory-backend-file,id=mem,size=2G,mem-path=/dev/
    <ns0:arg value="-numa"/>
    <ns0:arg value="node,memdev=mem"/>
    <ns0:arg value="-mem-prealloc"/>

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

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
/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

Am I missing something on the openvswitch or on the libvirt side?

It looks like openvswitch can't find /opt/oa/vhost/0.vm.sock, but isn't
either openvswitch or libvirt in charge of creating it?
Then, I'm not too sure about the error messages in libvirtd.log...

My software versions are: libvirt 3.10.0, qemu 2.10.2, openvswitch 2.8.1
and DPDK 17.11.

Thanks a lot!
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