Re: [Xen-devel] [PATCH v2 2/7] libxl: add new hotplug interface support to hotplug script callers [and 1 more messages]

[Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>]

Ian Jackson writes ("Re: [Xen-devel] [PATCH v2 2/7] libxl: add new hotplug 
interface support to hotplug script callers"):
> Roger Pau Monne writes ("[Xen-devel] [PATCH v2 2/7] libxl: add new hotplug 
> interface support to hotplug script callers"):
...
> > +PREPARE
> > +-------
> > +
> > +This is the first operation that the hotplug script will be requested to
> > +execute. This operation is executed before the disk is connected, to
> > +give the hotplug script the chance to offload some work from the "add"
> > +operation, that is performed later.
> 
> But in fact in your implementation this is only called right before
> add, isn't it ?
> 
> Also, IIRC part of the point of this new interface is that for target
> devices which can't be accessed simultaneously from different hosts,
> during migration you'd be able to do costly setup during the initial
> part of the migration and merely "activate" the devices later.
> 
> Am I missing something ?

This question needs to be answered by the documentation, I think.

What are the guarantees that the hotplug scripts rely on ?

AFAICT what happens after your series is applied is that we always
call prepare just before add, and unprepare just after remove (if I
may neglect local attach for now).  So I don't see why these new
functions are necessary to your new scripts.

Ian.

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