Re: [Xen-devel] [PATCH V5 31/32] libxl: update domain configuration when updating memory targets

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Tue, 2014-05-20 at 16:44 +0100, Ian Jackson wrote:
> Ian Campbell writes ("Re: [PATCH V5 31/32] libxl: update domain configuration 
> when updating memory targets"):
> > The device cases in particular are a lot harder to handle in that way.
> > This was how I originally envisaged this would work, Wei's approach
> > seemed to me to be much much simpler.
> 
> Much of the work of turning the xenstore info for a device back into a
> libxl_disk_device or whatever has already been done: see e.g.
> libxl__device_disk_from_xs_be.

For example this would omit the distinction between the user asking for
a default backend and them asking for a specific one. If the user asked
for the default then the receiving xl would end up inheriting the
sending xl's decision, which is not correct.

So the original configuration, before setdefaults etc, needs to be
stored somewhere that it can be retrieved. Same goes for a lot of fields
I think.

> Merging the lists from libxl_device_disk_list and the JSON
> configuration shouldn't be too hard and will eliminate a lot of worry
> about races.

I think the presence of defaults in the libxl API makes it hard.

Ian.



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