I've tried naively to convince libvirt to use virtio-scsi and still present it to the guest as 'vd*' - that didn't work (
<disk type='file' device='disk'>
<driver name='qemu' type='qcow2'/>
<source file='/dev/shm/run/default/images/lago_basic_suite_master_storage_root.qcow2'/>
<backingStore type='file' index='1'>
<format type='raw'/>
<source file='/home/lagostore/phx_repo:el7-base:latest'/>
<backingStore/>
</backingStore>
<target dev='vda' bus='scsi'/>
<boot order='1'/>
<alias name='scsi0-0-0'/>
<address type='drive' controller='0' bus='0' target='0' unit='0'/>
</disk>
Y.