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Re: [Qemu-devel] [PATCH v10 09/16] block: Add QMP support for streaming
From: |
Alberto Garcia |
Subject: |
Re: [Qemu-devel] [PATCH v10 09/16] block: Add QMP support for streaming to an intermediate layer |
Date: |
Tue, 11 Oct 2016 16:30:33 +0200 |
User-agent: |
Notmuch/0.18.2 (http://notmuchmail.org) Emacs/24.4.1 (i586-pc-linux-gnu) |
On Mon 10 Oct 2016 09:09:25 PM CEST, Eric Blake wrote:
>> # @job-id: #optional identifier for the newly-created block job. If
>> # omitted, the device name will be used. (Since 2.7)
>> #
>> -# @device: the device name or node-name of a root node
>> +# @device: the device or node name of the top image
>> #
>> # @base: #optional the common backing file name
>> #
>> -# @backing-file: #optional The backing file string to write into the active
>> -# layer. This filename is not validated.
>> +# @backing-file: #optional The backing file string to write into the top
>> +# image. This filename is not validated.
>
> No change to the actual introspection. What's the easiest way for
> libvirt to learn if the new style command will work, short of actually
> trying it to see if it succeeds or fails? (That may be sufficient,
> but the error message quality can often be improved in libvirt if it
> is known up front if qemu is new enough rather than taking the 'try
> and see' approach and getting stuck with qemu's error message)
I don't think there's any straightforward way. Some ideas:
1) Try to start a block-stream job that does nothing. When base ==
backing_bs(device) that's a no-op, but it fails if device is not the
root node and intermediate block streaming is not supported.
2) We could add an extra parameter. For example 'base-node', which would
be the same as 'base' but would take a node name instead of a file name.
3) QEMU could advertise that feature to the client. This is probably
simpler than trying to figure it out from the API. I guess that's the
idea of 'qmp_capabilities'?
Berto
- [Qemu-devel] [PATCH v10 00/16] Support streaming to an intermediate layer, Alberto Garcia, 2016/10/06
- [Qemu-devel] [PATCH v10 09/16] block: Add QMP support for streaming to an intermediate layer, Alberto Garcia, 2016/10/06
- Re: [Qemu-devel] [PATCH v10 09/16] block: Add QMP support for streaming to an intermediate layer, Eric Blake, 2016/10/10
- Re: [Qemu-devel] [PATCH v10 09/16] block: Add QMP support for streaming to an intermediate layer,
Alberto Garcia <=
- Re: [Qemu-devel] [PATCH v10 09/16] block: Add QMP support for streaming to an intermediate layer, Kevin Wolf, 2016/10/11
- Re: [Qemu-devel] [PATCH v10 09/16] block: Add QMP support for streaming to an intermediate layer, Eric Blake, 2016/10/11
- Re: [Qemu-devel] [PATCH v10 09/16] block: Add QMP support for streaming to an intermediate layer, Markus Armbruster, 2016/10/11
- Re: [Qemu-devel] [PATCH v10 09/16] block: Add QMP support for streaming to an intermediate layer, Kevin Wolf, 2016/10/12
- Re: [Qemu-devel] [PATCH v10 09/16] block: Add QMP support for streaming to an intermediate layer, Alberto Garcia, 2016/10/12
- Re: [Qemu-devel] [PATCH v10 09/16] block: Add QMP support for streaming to an intermediate layer, Markus Armbruster, 2016/10/11
- Re: [Qemu-devel] [PATCH v10 09/16] block: Add QMP support for streaming to an intermediate layer, Alberto Garcia, 2016/10/12
- Re: [Qemu-devel] [PATCH v10 09/16] block: Add QMP support for streaming to an intermediate layer, Markus Armbruster, 2016/10/12
Re: [Qemu-devel] [PATCH v10 09/16] block: Add QMP support for streaming to an intermediate layer, Kevin Wolf, 2016/10/12