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Date: Fri, 25 Feb 2011 07:16:50 +0000
Message-ID: <AANLkTikPCq74RLdVT0mv53pF_1wRsge57-BCT93mUdOy@mail.gmail.com>
Subject: Re: [Qemu-devel] Re: [patch 2/3] Add support for live block copy
From: Stefan Hajnoczi <stefanha@gmail.com>
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To: Avi Kivity <avi@redhat.com>
Cc: Jes.Sorensen@redhat.com, Marcelo Tosatti <mtosatti@redhat.com>, qemu-devel@nongnu.org

On Wed, Feb 23, 2011 at 3:31 PM, Avi Kivity <avi@redhat.com> wrote:
> On 02/23/2011 04:35 PM, Anthony Liguori wrote:
>>
>> QEMU uses the state database to store information that is created
>> dynamically. =A0For instance, devices added through device_add. =A0A dev=
ice
>> 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 requi=
re
>> the command line being updated.
>
> Then the invoker quickly loses track of what the actual state is. =A0It c=
an't
> just remember which commands it issued (presumably in response to the use=
r
> updating user visible state). =A0It has to parse the stateful config file=
 qemu
> outputs. =A0But at which points should it parse it?
>
> I don't think it's reasonable to have three different ways to interact wi=
th
> qemu, all needed: the command line, reading and writing the stateful conf=
ig
> file, and the monitor. =A0I'd rather push for starting qemu with a blank =
guest
> and assembling (cold-plugging) all the hardware via the monitor before
> starting the guest.

This is why I asked about unifying the stateful config with qdev or
QemuOpts in the machine init mailing list thread.  If we have n
different ways of toggling things inside QEMU including command-line,
HMP, QMP, and stateful config, then a large chunk of QEMU is just
going to be parsing and formatting these external interfaces.

Stefan