v3:
- Rebase on master
- Add a test case for detached LUKS header
- Adjust the design to honour preallocation of the payload device
- Adjust the design to honour the payload offset from the header,
  even when detached
- Support detached LUKS header creation using qemu-img
- Support detached LUKS header querying
- Do some code clean

Thanks for commenting on this series, please review.

Best regared,

Yong

v2:
- Simplify the design by reusing the LUKS driver to implement
  the generic Luks encryption, thank Daniel for the insightful 
  advice.
- rebase on master. 

This functionality was motivated by the following to-do list seen
in crypto documents:
https://wiki.qemu.org/Features/Block/Crypto 

The last chapter says we should "separate header volume": 

The LUKS format has ability to store the header in a separate volume
from the payload. We should extend the LUKS driver in QEMU to support
this use case.

By enhancing the LUKS driver, it is possible to enable
the detachable LUKS header and, as a result, achieve
general encryption for any disk format that QEMU has
supported.

Take the qcow2 as an example, the usage of the generic
LUKS encryption as follows:

1. add a protocol blockdev node of data disk
$ virsh qemu-monitor-command vm '{"execute":"blockdev-add",
> "arguments":{"node-name":"libvirt-1-storage", "driver":"file",
> "filename":"/path/to/test_disk.qcow2"}}'

2. add a protocol blockdev node of LUKS header as above.
$ virsh qemu-monitor-command vm '{"execute":"blockdev-add",
> "arguments":{"node-name":"libvirt-2-storage", "driver":"file",
> "filename": "/path/to/cipher.gluks" }}'

3. add the secret for decrypting the cipher stored in LUKS
   header above
$ virsh qemu-monitor-command vm '{"execute":"object-add",
> "arguments":{"qom-type":"secret", "id":
> "libvirt-2-storage-secret0", "data":"abc123"}}'

4. add the qcow2-drived blockdev format node
$ virsh qemu-monitor-command vm '{"execute":"blockdev-add",
> "arguments":{"node-name":"libvirt-1-format", "driver":"qcow2",
> "file":"libvirt-1-storage"}}'

5. add the luks-drived blockdev to link the qcow2 disk with
   LUKS header by specifying the field "header"
$ virsh qemu-monitor-command vm '{"execute":"blockdev-add",
> "arguments":{"node-name":"libvirt-2-format", "driver":"luks",
> "file":"libvirt-1-format", "header":"libvirt-2-storage",
> "key-secret":"libvirt-2-format-secret0"}}'

6. add the virtio-blk device finally
$ virsh qemu-monitor-command vm '{"execute":"device_add",
> "arguments": {"num-queues":"1", "driver":"virtio-blk-pci",
> "drive": "libvirt-2-format", "id":"virtio-disk2"}}'

The generic LUKS encryption method of starting a virtual
machine (VM) is somewhat similar to hot-plug in that both
maintaining the same json command while the starting VM
changes the "blockdev-add/device_add" parameters to
"blockdev/device".

Hyman Huang (10):
  crypto: Introduce option and structure for detached LUKS header
  crypto: Support generic LUKS encryption
  qapi: Make parameter 'file' optional for BlockdevCreateOptionsLUKS
  crypto: Introduce creation option and structure for detached LUKS
    header
  crypto: Mark the payload_offset_sector invalid for detached LUKS
    header
  block: Support detached LUKS header creation using blockdev-create
  block: Support detached LUKS header creation using qemu-img
  crypto: Introduce 'detached-header' field in QCryptoBlockInfoLUKS
  tests: Add detached LUKS header case
  MAINTAINERS: Add section "Detached LUKS header"

 MAINTAINERS                                   |   5 +
 block.c                                       |   5 +-
 block/crypto.c                                | 146 ++++++++++--
 block/crypto.h                                |   8 +
 crypto/block-luks.c                           |  49 +++-
 crypto/block.c                                |   1 +
 crypto/blockpriv.h                            |   3 +
 qapi/block-core.json                          |  14 +-
 qapi/crypto.json                              |  13 +-
 tests/qemu-iotests/210.out                    |   4 +
 tests/qemu-iotests/tests/luks-detached-header | 214 ++++++++++++++++++
 .../tests/luks-detached-header.out            |   5 +
 12 files changed, 436 insertions(+), 31 deletions(-)
 create mode 100755 tests/qemu-iotests/tests/luks-detached-header
 create mode 100644 tests/qemu-iotests/tests/luks-detached-header.out

-- 
2.39.1