What were you trying to do that didn't work?

Failed to start guest with  ethernet type + managed=no + mutiqueue enabled interface device:

error: Failed to start domain 'avocado-vt-vm1'
error: Unable to create tap device tap_u48: Invalid argument

Please provide the package NVR for which bug is seen:

libvirt-10.5.0-5.el9.x86_64

qemu-kvm-9.0.0-8.el9.x86_64

kernel-5.14.0-494.el9.x86_64

How reproducible:

100%

Steps to reproduce

1. Create tap device:

 # ip tuntap add mode tap name tap_u48;ip link set dev tap_u48 mtu 2000
 # ip link show tap_u48
255: tap_u48: <BROADCAST,MULTICAST> mtu 2000 qdisc noop state DOWN mode DEFAULT group default qlen 1000

      2.Prepare an inactive guest with 

#virsh dumpxml avocado-vt-vm1 --xpath //interface
<interface type="ethernet">
  <mac address="52:54:00:d6:bb:94"/>
  <target dev="tap_u48" managed="no"/>
  <model type="virtio"/>
  <driver queues="2"/>
  <mtu size="1400"/>
  <address type="pci" domain="0x0000" bus="0x07" slot="0x00" function="0x0"/>
</interface>
 

   3.Start the guest:

 # virsh start avocado-vt-vm1
error: Failed to start domain 'avocado-vt-vm1'
error: Unable to create tap device tap_u48: Invalid argument

Expected results

1.If ethernet type + managed=no + mutiqueue enabled interface device is supported, guest should start successfully.

2. If ethernet type + managed=no + mutiqueue enabled interface device is not supported, the error info is strange because libvirt should not create tap device with managed=no.

Actual results

Failed to start guest with ethernet type + managed=no + mutiqueue enabled  interface device.

Additional info:

Guest can start successfully if not enable multiqueue.