Hi,

this is an incompatibility of current libvirt in unstable with current
qemu in unstable, documented upstream as https://gitlab.com/libvirt/libvirt/-/issues/212

In a nutstell, it seems no longer possible to add a storage device
pointing to, for example, /dev/sda6 od /dev/mapper/lvname. A VM with
such a definition:

    <disk type='file' device='disk'>
      <driver name='qemu' type='raw'/>
      <source file='/dev/mapper/cryptodevice'/>
      <target dev='vda' bus='virtio'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x08' function='0x>
    </disk>                                                                                      ,
will no longer start:

+{"driver":"file","filename":"/dev/mapper/cryptodevice","node-name":"libvirt-1-storage","auto-read-only":true,"discard":"unmap"}: 'file' driver requires '/dev/mapper/cryptodevice' to be a regular file

Especially virt-manager users will be bitten by this since they don't
know how to write proper XML to make their VM work again.

I don't know whether this needs to be fixed in libvirt or virt-manager
(I suspect in both), since this seems to be an intended change in qemu.

For the time being, I recommend adding versioned dependencies, breaks
and/or conflicts with qemu 6.x to libvirt to avoid people updating into
unusable libvirt/qemu. The appropriate bug to qemu is #Bug#993688

Please forward appropriately to virt-manager in case virt-manager needs
to do things as well.

Greetings
Marc