[libvirt] RFCv2: virDomainSnapshotCreateXML enhancements

[Eric Blake]

On 08/12/2011 02:56 AM, Philipp Hahn wrote:
>>> For -loadvm to work you have to call kvm with the nearly same command
>>> line arguments again; what may change you probably know better than me.
>>> For I thinks it's essential to store the VM consiguration with the
>>> snapshot, which would be the qemu command line arguments, which is
>>> equivalent to libvirts XML description.
>>
>> Yes, I understand this. I was talking about snapshots taken while the VM
>> is shut off, where it's not as clear.
>
> I think is very useful for offline snapshots too, since your VM might depends
> on the exact qemu command line: think of (incomplete) RAIDs or udevs
> persistent MAC address rules.
>
>> But for consistency it's probably
>> better to do the same with offline and online snapshots, so what libvirt
>> implements (or was it only Eric's plan?) is fine here.

My plan is to do full-scale revert to the embedded <domain>, whether the 
checkpoint was online or offline.  To go from running to an online 
checkpoint when the <domain> is still ABI compatible, I will continue to 
use the 'loadvm' monitor command; for all other cases, loading an online 
checkpoint will create a new qemu process with the '-loadvm' command 
line argument.

>
> Currently as of libvirt-0.9.4 the domain configuration is not saved with the
> snapshot. I have implemented that for our internal 0.8.4 version as a working
> proof-on-concept, but Eric is now reviewing the whole picture.

Yep, I'm heavily re-using Philipp's proof-of-concept in the part of my 
patch series that embeds the full <domain> into <domainsnapshot>.

-- 
Eric Blake   eblake at redhat.com    +1-801-349-2682
Libvirt virtualization library http://libvirt.org