* 'Klaus Aehlig' via ganeti-devel <[email protected]> [2014-10-02 
12:17:35 +0200]:

> 
> Hi Dimara,
> 
> thanks for your email. I have to admit that this patch
> series mainly focused on Xen where the absense of that
> check did cause problems.
> 

I just saw issue 945 that was reported internally by Google
and you are not using KVM..

> > [...] This overrides the machine_version feature (which I know is only for 
> > the
> > KVM hypervisor) but is working correctly.
> 
> So what would you suggest? Only check if Xen is used?
> 

This would be hackish.. A reasonable work around is to change the
--ignore-hvversions to --check-hvversions and set it False by default.
This would not break compatibility (but it would require a change in
external scripts that would like to use this new feature).

Still since this is supposed to by hypervisor specific, I guess the
proper way to implement it is the following way:

 - Get hypervisor version source (but the one of the running instance
   and not the node's one). In Xen it should be the same but in KVM it
   requires a monitor call. I guess this requires extending the RPC
   mechanism.
 - Get the hypervisor version of target node. This is done already.
 - Introduce new classmethod of BaseHypervisor (e.g.
   IsMigrationSupportedBetween(cls, src, tgt)) that takes source and
   target version and returns True or False (and move it out from
   utils).
 - And based on the opcode's options abort or not.

What do you think?

dimara

> Thanks,
> Klaus
> 
> -- 
> Klaus Aehlig
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