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Re: [Qemu-devel] Re: [patch 2/3] Add support for live block copy
From: |
Markus Armbruster |
Subject: |
Re: [Qemu-devel] Re: [patch 2/3] Add support for live block copy |
Date: |
Wed, 23 Feb 2011 18:26:25 +0100 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/23.1 (gnu/linux) |
Avi Kivity <address@hidden> writes:
> On 02/23/2011 04:35 PM, Anthony Liguori wrote:
>> On 02/23/2011 07:01 AM, Avi Kivity wrote:
>>> On 02/23/2011 01:14 AM, Anthony Liguori wrote:
>>>>
>>>> -drive already ties into the qemuopts infrastructure and we have
>>>> readconfig and writeconfig. I don't think we're missing any major
>>>> pieces to do this in a more proper fashion.
>>>
>>> The problem with qemu config files is that it splits the
>>> authoritative source of where images are stored into two. Is it in
>>> the management tool's database or is it in qemu's config file?
>>
>> I like to use the phrase "stateful config file". To me, it's just a
>> database for QEMU to persist data about the VM. It's the only way
>> for QEMU to make certain transactions atomic in the face of QEMU
>> crashing.
>>
>> The user visible config file is a totally different concept. A
>> management tool launches QEMU and tells it where to keep it's state
>> database. The management application may prepopulate the state
>> database or it may just use an empty file.
>
> In that case the word 'config' is misleading. To me, it implies that
> the user configures something, and qemu reads it, not something mostly
> internal to qemu.
>
> Qemu does keep state. Currently only images, but in theory also the
> on-board NVRAM.
>
>>
>> QEMU uses the state database to store information that is created
>> dynamically. For instance, devices added through device_add. A
>> device added via -device wouldn't necessary get added to the state
>> database.
>>
>> Practically speaking, it let's you invoke QEMU with a fixed command
>> line, while still using the monitor to make changes that would
>> otherwise require the command line being updated.
>
> Then the invoker quickly loses track of what the actual state is. It
> can't just remember which commands it issued (presumably in response
> to the user updating user visible state). It has to parse the
> stateful config file qemu outputs. But at which points should it
> parse it?
>
> I don't think it's reasonable to have three different ways to interact
> with qemu, all needed: the command line, reading and writing the
> stateful config file, and the monitor. I'd rather push for starting
> qemu with a blank guest and assembling (cold-plugging) all the
> hardware via the monitor before starting the guest.
Exactly. And qdev has brought his within our reach.
[...]
- Re: [Qemu-devel] Re: [patch 2/3] Add support for live block copy, (continued)
- Re: [Qemu-devel] Re: [patch 2/3] Add support for live block copy, Anthony Liguori, 2011/02/28
- Re: [Qemu-devel] Re: [patch 2/3] Add support for live block copy, Avi Kivity, 2011/02/28
- Re: [Qemu-devel] Re: [patch 2/3] Add support for live block copy, Anthony Liguori, 2011/02/28
- Re: [Qemu-devel] Re: [patch 2/3] Add support for live block copy, Avi Kivity, 2011/02/28
- Re: [Qemu-devel] Re: [patch 2/3] Add support for live block copy, Anthony Liguori, 2011/02/28
- Re: [Qemu-devel] Re: [patch 2/3] Add support for live block copy, Marcelo Tosatti, 2011/02/28
- Re: [Qemu-devel] Re: [patch 2/3] Add support for live block copy, Peter Maydell, 2011/02/23
- Re: [Qemu-devel] Re: [patch 2/3] Add support for live block copy, Anthony Liguori, 2011/02/23
- [Qemu-devel] Unsubsribing, James Brown, 2011/02/24
- Re: [Qemu-devel] Unsubsribing, Stefan Hajnoczi, 2011/02/24
- Re: [Qemu-devel] Re: [patch 2/3] Add support for live block copy,
Markus Armbruster <=
- Re: [Qemu-devel] Re: [patch 2/3] Add support for live block copy, Anthony Liguori, 2011/02/23
- Re: [Qemu-devel] Re: [patch 2/3] Add support for live block copy, Markus Armbruster, 2011/02/24
- Re: [Qemu-devel] Re: [patch 2/3] Add support for live block copy, Stefan Hajnoczi, 2011/02/25
- Re: [Qemu-devel] Re: [patch 2/3] Add support for live block copy, Marcelo Tosatti, 2011/02/23
- Re: [Qemu-devel] Re: [patch 2/3] Add support for live block copy, Avi Kivity, 2011/02/24
- Re: [Qemu-devel] Re: [patch 2/3] Add support for live block copy, Marcelo Tosatti, 2011/02/24
- Re: [Qemu-devel] Re: [patch 2/3] Add support for live block copy, Avi Kivity, 2011/02/24
- Re: [Qemu-devel] Re: [patch 2/3] Add support for live block copy, Marcelo Tosatti, 2011/02/24
- Re: [Qemu-devel] Re: [patch 2/3] Add support for live block copy, Avi Kivity, 2011/02/24
- Re: [Qemu-devel] Re: [patch 2/3] Add support for live block copy, Anthony Liguori, 2011/02/24