[Qemu-devel] [PATCH 0/2] block: drive_add/del without BlockBackend

[Kevin Wolf <kwolf@redhat.com>]

See patch 1 for the detailed description why this is needed. The short
version is that libvirt needs to enable detect-zeroes on a mirror
target.

Peter, can you please check if this provides what you need? I checked
whether I could do the mirroring operation manually; and if I did it
right, it looks good to me. (Shortened) protocol of my test:

$ ./qemu-img create -f qcow2 /tmp/test.qcow2 64M
Formatting '/tmp/test.qcow2', fmt=qcow2 size=67108864 encryption=off cluster_size=65536 lazy_refcounts=off refcount_bits=16

$ ./qemu-io -c 'write -P 0 0 64M' /tmp/test.qcow2 
wrote 67108864/67108864 bytes at offset 0
64 MiB, 1 ops; 0.3141 sec (203.694 MiB/sec and 3.1827 ops/sec)

$ ls -lh /tmp/test.qcow2 
-rw-r--r--. 1 kwolf kwolf 65M 23. Feb 17:57 /tmp/test.qcow2

$ ./qemu-img create -f qcow2 /tmp/copy.qcow2 64M
Formatting '/tmp/copy.qcow2', fmt=qcow2 size=67108864 encryption=off cluster_size=65536 lazy_refcounts=off refcount_bits=16

$ x86_64-softmmu/qemu-system-x86_64 -qmp stdio -hda /tmp/test.qcow2
{"QMP": {"version": {"qemu": {"micro": 50, "minor": 5, "major": 2}, "package": ""}, "capabilities": []}}
{"execute":"qmp_capabilities"}
{"return": {}}
{"execute":"human-monitor-command","arguments":{"command-line":"drive_add -n 0 file.filename=/tmp/copy.qcow2,node-name=copy,detect-zeroes=on"}}
{"return": ""}
{"execute":"blockdev-mirror","arguments":{"device":"ide0-hd0","target":"copy","sync":"full"}}
{"return": {}}
{"timestamp": {"seconds": 1456247099, "microseconds": 895774}, "event": "BLOCK_JOB_READY", "data": {"device": "ide0-hd0", "len": 67108864, "offset": 67108864, "speed": 0, "type": "mirror"}}
{"execute":"block-job-complete","arguments":{"device":"ide0-hd0"}}
{"return": {}}
{"timestamp": {"seconds": 1456247127, "microseconds": 552227}, "event": "BLOCK_JOB_COMPLETED", "data": {"device": "ide0-hd0", "len": 67108864, "offset": 67108864, "speed": 0, "type": "mirror"}}

$ ls -lh /tmp/copy.qcow2 
-rw-r--r--. 1 kwolf kwolf 320K 23. Feb 18:04 /tmp/copy.qcow2

Kevin Wolf (2):
  hmp: 'drive_add -n' for creating a node without BB
  hmp: Extend drive_del to delete nodes without BB

 blockdev.c                | 39 +++++++++++++++++++++++++++++++++++++++
 device-hotplug.c          |  7 +++++++
 hmp-commands.hx           |  4 ++--
 include/block/block_int.h |  2 ++
 4 files changed, 50 insertions(+), 2 deletions(-)

-- 
1.8.3.1