Re: [Xen-devel] [PATCH V3 13/13] xl: introduce "xl-json" format

[Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>]

Wei Liu writes ("[PATCH V3 13/13] xl: introduce "xl-json" format"):
> Originally xl verbatimly copies the domain config file in its user data
> store. This patch adds the functionality to transform text domain config
> file to JSON object and save that object in user data store.

As I said on IRC, I think you should explain your plans for this.  I
approve of your plans :-).

> What this patch does:
> 1. add a mandatory flag to save protocol to indicate whether the saved
>    config is a JSON object
> 2. register a new private data type "xl-json" in libxl.h
> 3. modify xl to save / load "xl-json" file where necessary
> 
> After this change xl supports both "xl" format and "xl-json" format.
> The user-supplied config file is still restricted to normal text config
> file format ("xl"), as xl has more sanity checks when parsing text
> config file. "xl-json" format is only used internally. The saved config
> file is always in "xl-json" format.

I think it would be very useful to allow people to
  - retreive the domain's json config
  - start a new domain with a json config
That would let you write a program to adjust a domain's config, for
example.

If there is something important error that xl checks for, which can
also be represented as an error in the domain config IDL struct, but
which isn't checked for by libxl, I think that's a bug in libxl.

> Tests done so far (xl.{new,old} denotes xl with{,out} "xl_json"
> support):
> 1. xl.new create then hexdump saved file: domain config saved in JSON format
> 2. xl.new create then xl.old restore: failed on mandatory flag check
> 3. xl.new create then xl.new restore: succeeded
> 4. xl.old create then xl.new restore: succeeded
> 5. xl.new create then local migrate, receiving end xl.new: succeeded
> 6. xl.old create then local migrate, receiving end xl.new: succeeded

Great, thanks.

Ian.

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