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

[Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>]

Roger Pau Monne writes ("[Xen-devel] [PATCH v2 2/7] libxl: add new hotplug 
interface support to hotplug script callers"):
> +This document specifies the new libxl hotplug interface. This new
> +interface has been designed to operate better with complex hotplug
> +scripts, that need to perform several operations and can take a
> +considerable time to execute.
> +
> +Hotplug scripts are expected to take a parameter, passed by the caller
> +and provide a block device as output, that will be attached to the guest.

> +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 ?

Thanks,
Ian.

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