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Date: Mon, 06 Jul 2009 18:13:26 -0500
From: Anthony Liguori <anthony@codemonkey.ws>
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Subject: Re: [Qemu-devel] Re: [PATCH 0/4] Machine config files
References: <20090610173803.4674.82538.stgit@wren.home>
	<4A52284C.9080604@redhat.com> <4A523444.30002@codemonkey.ws>
	<200907062339.43850.paul@codesourcery.com>
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To: Paul Brook <paul@codesourcery.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>, Jan Kiszka <jan.kiszka@siemens.com>, qemu-devel@nongnu.org, Markus Armbruster <armbru@redhat.com>, Gerd Hoffmann <kraxel@redhat.com>, Avi Kivity <avi@redhat.com>

Paul Brook wrote:
>> Most importantly, machine config should not be sent until non-live
>> migration kicks in.  At this point, the device tree is stable because
>> the guest isn't running.  The device tree should be the first section
>> saved for non-live migration.
>>     
>
> RAM is part of the machine config, and can be hotplugged[1], so you need at 
> least that before you start transferring anything.
>   

You really don't.  The ram_load_live handler should receive RAM as it 
comes in and maintain a growable buffer for all the independently 
transferred regions.  A nice property of live migration is that you'll 
get the whole region at once so something simple based on realloc() will 
work well.

When it comes time to create the virtual machine, you have memory 
buffers ready to be used as the guest's memory.  If it's not sized 
appropriately, you throw an error and migration aborts.

Regards,

Anthony Liguori