Re: [Qemu-devel] [libvirt] [PATCH v2 1/4] config: Introduce <migration> for SPICE graphics

[Eric Blake <eblake@redhat.com>]

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[adding qemu]

On 09/14/2012 11:47 AM, Daniel P. Berrange wrote:
> On Fri, Sep 14, 2012 at 07:34:50PM +0200, Michal Privoznik wrote:
>> With this element users will control how SPICE
>> server behaves upon migration. For now, there's
>> just one attribute 'seamless' turning seamless
>> migration on/off/default.
> 
> Ewww, no. This information is a related to a API operation,
> not the VM configuration. It should be either auto-detected
> by libvirt to the best compatible setting, or passed as a
> flag to the virDomainMigrate API call if auto-detection is
> not possible.

But with the current qemu implementation, there's no way to know if the
destination supports this until after you've started the source, and the
current implementation in qemu is that you must declare the semantics at
the time you start qemu, not at the time you send the 'migrate' monitor
command.  For libvirt autodetection to work without polluting the domain
XML, we'd need to be able to auto-detect at the time we start migration.

This sounds like we need to enhance the 'migrate-set-capabilities'
command to enable or disable this feature on the fly, according to what
libvirt detects from the remote end, rather than hard-coding it to the
startup state of qemu on the source side.

-- 
Eric Blake   eblake@redhat.com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org


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