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Date: Tue, 12 Mar 2013 11:07:54 +0100
From: Stefan Hajnoczi <stefanha@gmail.com>
Message-ID: <20130312100754.GC19624@stefanha-thinkpad.redhat.com>
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Subject: Re: [Qemu-devel] [PATCH V9 00/14] qmp/hmp interfaces for internal
	snapshot info
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To: Wenchao Xia <xiawenc@linux.vnet.ibm.com>
Cc: kwolf@redhat.com, armbru@redhat.com, qemu-devel@nongnu.org, lcapitulino@redhat.com, pbonzini@redhat.com

On Mon, Mar 11, 2013 at 07:23:02PM +0800, Wenchao Xia wrote:
>   In the use of snapshot a way to retrieve related info at runtime is needed,
> so this serial of patches will merge some code for qemu and qemu-img, and add
> following interfaces for qemu:
> 
> 1) qmp: query-images, show image info for a block device
> Example:
> -> { "execute": "query-images" }
> <- {
>       "return":[
>          {
>             "device":"ide0-hd0",
>             "image":{
>                "filename":"disks/test1.img",
>                "format":"qcow2",
>                "virtual-size":2048000,
>                "snapshots":[
>                   {
>                      "id": "1",
>                      "name": "snapshot1",
>                      "vm-state-size": 0,
>                      "date-sec": 10000200,
>                      "date-nsec": 12,
>                      "vm-clock-sec": 206,
>                      "vm-clock-nsec": 30
>                   }
>                ]
>             }
>          }
>       ]
>    }

See my recent RFC patch to add a virtual_size to query-block:
http://permalink.gmane.org/gmane.comp.emulators.qemu/199443

Is there a reason you added the new query-images command instead of
extending BlockDeviceInfo with an ImageInfo field?  Then query-block,
which is already used today, just provides ImageInfo as well.

I suggest this because it makes life easier for clients - they can issue
a single command to extract all image information.  If we have two
commands they may have to invoke both and then match the results
together.

Stefan