I've tested a 5.19-rc3 kernel on top of QEMU/KVM with machine type
pc-q35-5.2.  It has a virtio balloon device defined in libvirt as:

    <memballoon model="virtio">
      <address type="pci" domain="0x0000" bus="0x05" slot="0x00" function="0x0"/>
    </memballoon>

but the virtio_balloon driver fails to bind to it:

    virtio_balloon virtio4: init_vqs: add stat_vq failed
    virtio_balloon: probe of virtio4 failed with error -5

On a 5.18 kernel with similar configuration, it binds successfully.

I've attached the kernel config for 5.19-rc3.

Ben.

-- 
Ben Hutchings
Q.  Which is the greater problem in the world today,
    ignorance or apathy?
A.  I don't know and I couldn't care less.