Remove KVM Disk
A note about removing virtual disks from KVM guests when using virtio-blk-data-plane.
When a disk is removed from a KVM guest using the virt-manager GUI tool, and if virtio-blk-data-plane is being used, an error will occur when restarting the KVM guest as shown below.
gstanden@vmem1:~$ virsh start oracle651
error: Failed to start domain oracle651
error: internal error: process exited while connecting to monitor: qemu-system-x86_64: -set device.virtio-disk2.scsi=off: there is no device "virtio-disk2" defined
gstanden@vmem1:~$ virsh edit oracle651
This occurs because virt-manager has no knowledge of virtio-blk-data-plane code in the XML file defining the VM. The code for the virtio-blk-data-plane feature must be removed manually as shown below. Remove the bolded entries as shown below using the error message shown above to indicate which "Disk#" is referenced by the deleted disk, in this case "Disk2".
gstanden@vmem1:~$ cat oracle651.xml
<domain type='kvm' xmlns:qemu='http://libvirt.org/schemas/domain/qemu/1.0'>
<name>oracle651</name>
<uuid>9a017de6-d362-4269-90fe-09331460aca0</uuid>
<memory unit='KiB'>1048576</memory>
<currentMemory unit='KiB'>1048576</currentMemory>
<vcpu placement='static'>8</vcpu>
<resource>
<partition>/machine</partition>
</resource>
<os>
<type arch='x86_64' machine='pc-i440fx-trusty'>hvm</type>
<boot dev='hd'/>
<boot dev='cdrom'/>
<bootmenu enable='yes'/>
</os>
<features>
<acpi/>
<apic/>
<pae/>
</features>
<clock offset='utc'/>
<on_poweroff>destroy</on_poweroff>
<on_reboot>restart</on_reboot>
<on_crash>restart</on_crash>
<devices>
<emulator>/usr/bin/kvm-spice</emulator>
<disk type='file' device='disk'>
<driver name='qemu' type='raw' cache='none' io='native'/>
<source file='/var/lib/libvirt/images/oracle651-0.img'/>
<target dev='vda' bus='virtio'/>
<address type='pci' domain='0x0000' bus='0x00' slot='0x05' function='0x0'/>
</disk>
<disk type='file' device='disk'>
<driver name='qemu' type='raw' cache='none' io='native'/>
<source file='/var/lib/libvirt/images/oracle651-3.img'/>
<target dev='vdd' bus='virtio'/>
<address type='pci' domain='0x0000' bus='0x00' slot='0x0b' function='0x0'/>
</disk>
<disk type='file' device='disk'>
<driver name='qemu' type='raw' cache='none' io='native'/>
<source file='/var/lib/libvirt/images/oracle651-4.img'/>
<target dev='vde' bus='virtio'/>
<address type='pci' domain='0x0000' bus='0x00' slot='0x0c' function='0x0'/>
</disk>
<disk type='block' device='cdrom'>
<driver name='qemu' type='raw'/>
<target dev='hdc' bus='ide' tray='open'/>
<readonly/>
<address type='drive' controller='0' bus='1' target='0' unit='0'/>
</disk>
<controller type='usb' index='0'>
<address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x2'/>
</controller>
<controller type='pci' index='0' model='pci-root'/>
<controller type='ide' index='0'>
<address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x1'/>
</controller>
<interface type='bridge'>
<mac address='52:54:00:66:26:a0'/>
<source bridge='sw1'/>
<virtualport type='openvswitch'>
<parameters interfaceid='0efa5f2a-cbf2-46df-9ff2-66bddb09218d'/>
</virtualport>
<target dev='s4'/>
<model type='virtio'/>
<address type='pci' domain='0x0000' bus='0x00' slot='0x03' function='0x0'/>
</interface>
<interface type='bridge'>
<mac address='52:54:00:65:c2:e5'/>
<source bridge='sw2'/>
<virtualport type='openvswitch'>
<parameters interfaceid='bd4a4643-dae2-488c-8d84-24c388941207'/>
</virtualport>
<target dev='t4'/>
<model type='virtio'/>
<address type='pci' domain='0x0000' bus='0x00' slot='0x09' function='0x0'/>
</interface>
<interface type='bridge'>
<mac address='52:54:00:87:44:e1'/>
<source bridge='sw3'/>
<virtualport type='openvswitch'>
<parameters interfaceid='8a67e2de-d3b5-4fa8-af93-3e115e7f70e3'/>
</virtualport>
<target dev='w4'/>
<model type='virtio'/>
<address type='pci' domain='0x0000' bus='0x00' slot='0x0a' function='0x0'/>
</interface>
<serial type='pty'>
<target port='0'/>
</serial>
<console type='pty'>
<target type='serial' port='0'/>
</console>
<input type='mouse' bus='ps2'/>
<input type='keyboard' bus='ps2'/>
<graphics type='vnc' port='-1' autoport='yes' listen='127.0.0.1'>
<listen type='address' address='127.0.0.1'/>
</graphics>
<sound model='ich6'>
<address type='pci' domain='0x0000' bus='0x00' slot='0x04' function='0x0'/>
</sound>
<video>
<model type='cirrus' vram='9216' heads='1'/>
<address type='pci' domain='0x0000' bus='0x00' slot='0x02' function='0x0'/>
</video>
<memballoon model='virtio'>
<address type='pci' domain='0x0000' bus='0x00' slot='0x06' function='0x0'/>
</memballoon>
</devices>
<seclabel type='dynamic' model='apparmor' relabel='yes'/>
<qemu:commandline>
<qemu:arg value='-set'/>
<qemu:arg value='device.virtio-disk0.scsi=off'/>
<qemu:arg value='-set'/>
<qemu:arg value='device.virtio-disk0.config-wce=off'/>
<qemu:arg value='-set'/>
<qemu:arg value='device.virtio-disk0.x-data-plane=on'/>
<qemu:arg value='-set'/>
<qemu:arg value='device.virtio-disk2.scsi=off'/>
<qemu:arg value='-set'/>
<qemu:arg value='device.virtio-disk2.config-wce=off'/>
<qemu:arg value='-set'/>
<qemu:arg value='device.virtio-disk2.x-data-plane=on'/>
<qemu:arg value='-set'/>
<qemu:arg value='device.virtio-disk2.logical_block_size=4096'/>
<qemu:arg value='-set'/>
<qemu:arg value='device.virtio-disk2.physical_block_size=4096'/>
<qemu:arg value='-set'/>
<qemu:arg value='device.virtio-disk3.scsi=off'/>
<qemu:arg value='-set'/>
<qemu:arg value='device.virtio-disk3.config-wce=off'/>
<qemu:arg value='-set'/>
<qemu:arg value='device.virtio-disk3.x-data-plane=on'/>
<qemu:arg value='-set'/>
<qemu:arg value='device.virtio-disk3.physical_block_size=4096'/>
<qemu:arg value='-set'/>
<qemu:arg value='device.virtio-disk4.scsi=off'/>
<qemu:arg value='-set'/>
<qemu:arg value='device.virtio-disk4.config-wce=off'/>
<qemu:arg value='-set'/>
<qemu:arg value='device.virtio-disk4.x-data-plane=on'/>
<qemu:arg value='-set'/>
<qemu:arg value='device.virtio-disk4.physical_block_size=4096'/>
</qemu:commandline>
</domain>
gstanden@vmem1:~$
Once these references to the removed disk have been removed, the KVM guest will start normally with no errors.