Bug 1820040

Description of problem:
As subject

Version-Release number of selected component (if applicable):
libvirt-6.0.0-16.module+el8.2.0+6139+d66dece5.x86_64 OR v6.1.0-333-g30d3565181
qemu-kvm-4.2.0-17.module+el8.2.0+6141+0f540f16.x86_64

How reproducible:
100%

Steps to Reproduce:
1. Prepare a scsi block by scsi_debug
2. Prepare luks secret as https://libvirt.org/formatsecret.html .
Format the scsi block with luks:
# qemu-img create -f luks --object secret,data=redhat,id=sec0 -o key-secret=sec0 /dev/sdc 5M

3. Start a VM and attach the scsi disk with device type lun:
# cat /tmp/pr1.xml
<disk type="block" device="lun">
  <driver name="qemu" type="raw"/>
  <source dev="/dev/sdc">
    <encryption format="luks">
      <secret type="passphrase" uuid="90c9b4eb-ad37-479a-95ca-baac7a62fdee"/>
    </encryption>
    <reservations managed="yes"/>
  </source>
  <target dev="sdc" bus="scsi"/>
</disk>

➜  ~ virsh attach-device pc /tmp/pr1.xml                                       
error: Failed to attach device from /tmp/pr1.xml
error: internal error: unable to execute QEMU command 'device_add': cannot get SG_IO version number: Operation not supported

QMP:
2020-04-02 06:19:16.491+0000: 10103: info : qemuMonitorIOWrite:431 : QEMU_MONITOR_IO_WRITE: mon=0x7f7130004a90 buf={"execute":"object-add","arguments":{"qom-type":"pr-manager-helper","id":"pr-helper0","props":{"
path":"/var/lib/libvirt/qemu/domain-1-pc/pr-helper0.sock"}},"id":"libvirt-19"}                                                                                                                                    
2020-04-02 06:19:16.492+0000: 10103: info : qemuMonitorIOWrite:431 : QEMU_MONITOR_IO_WRITE: mon=0x7f7130004a90 buf={"execute":"blockdev-add","arguments":{"driver":"host_device","filename":"/dev/sdc","pr-manager"
:"pr-helper0","node-name":"libvirt-15-storage","auto-read-only":true,"discard":"unmap"},"id":"libvirt-20"}                                                                                                        
2020-04-02 06:19:16.494+0000: 10103: info : qemuMonitorIOWrite:431 : QEMU_MONITOR_IO_WRITE: mon=0x7f7130004a90 buf={"execute":"object-add","arguments":{"qom-type":"secret","id":"libvirt-15-format-encryption-secr
et0","props":{"data":"A6LYmRjat/68EC0f/QghlA==","keyid":"masterKey0","iv":"kOvzS7qSOZGElAXTDgSUMw==","format":"base64"}},"id":"libvirt-21"}                                                                       
2020-04-02 06:19:16.495+0000: 10103: info : qemuMonitorIOWrite:431 : QEMU_MONITOR_IO_WRITE: mon=0x7f7130004a90 buf={"execute":"blockdev-add","arguments":{"node-name":"libvirt-15-format","read-only":false,"driver
":"luks","key-secret":"libvirt-15-format-encryption-secret0","file":"libvirt-15-storage"},"id":"libvirt-22"}                                                                                                      
2020-04-02 06:19:18.785+0000: 10103: info : qemuMonitorIOWrite:431 : QEMU_MONITOR_IO_WRITE: mon=0x7f7130004a90 buf={"execute":"device_add","arguments":{"driver":"scsi-block","bus":"scsi0.0","channel":"0","scsi-i
d":"0","lun":"2","drive":"libvirt-15-format","id":"scsi0-0-0-2"},"id":"libvirt-23"}
2020-04-02 06:19:18.786+0000: 10103: info : qemuMonitorIOWrite:431 : QEMU_MONITOR_IO_WRITE: mon=0x7f7130004a90 buf={"execute":"blockdev-del","arguments":{"node-name":"libvirt-15-format"},"id":"libvirt-24"}     
2020-04-02 06:19:18.787+0000: 10103: info : qemuMonitorIOWrite:431 : QEMU_MONITOR_IO_WRITE: mon=0x7f7130004a90 buf={"execute":"blockdev-del","arguments":{"node-name":"libvirt-15-storage"},"id":"libvirt-25"}    
2020-04-02 06:19:18.788+0000: 10103: info : qemuMonitorIOWrite:431 : QEMU_MONITOR_IO_WRITE: mon=0x7f7130004a90 buf={"execute":"object-del","arguments":{"id":"libvirt-15-format-encryption-secret0"},"id":"libvirt-
26"}
2020-04-02 06:19:18.789+0000: 10103: info : qemuMonitorIOWrite:431 : QEMU_MONITOR_IO_WRITE: mon=0x7f7130004a90 buf={"execute":"object-del","arguments":{"id":"pr-helper0"},"id":"libvirt-27"}   

Actual results:
As subject

Expected results:
If qemu supports scsi-block device with format luks, the attach should be success.


If no, the error should be like:
error: unsupported configuration: disk device 'lun' using target 'scsi' must use **pure** 'raw' format
As we know the qcow2 format is not supported in scsi-block:
When attach a qcow2 lun device:
<disk type="block" device="lun">
  <driver name="qemu" type="qcow2"/>
  <source dev="/dev/sdc">
    <reservations managed="yes"/>
  </source>
  <target dev="sdc" bus="scsi"/>
</disk>

The error will appears:
error: unsupported configuration: disk device 'lun' using target 'scsi' must use  'raw' format

As engineer we know that raw+luks is actually luks format not raw format. But for the users, raw+luks is raw format. So if luks it not supported in scsi-block, not only we should disallow that usage but also improve the error msg.

Additional info: