Re: [Xen-devel] [PATCH 00/12] add per-domain and per-cpupool generic parameters

[Juergen Gross <jgross@xxxxxxxx>]

On 18/09/18 12:32, Jan Beulich wrote:
>>>> On 18.09.18 at 08:02, <jgross@xxxxxxxx> wrote:
>> Instead of using binary hypervisor interfaces for new parameters of
>> domains or cpupools this patch series adds support for generic text
>> based parameter parsing.
>>
>> Parameters are defined via new macros similar to those of boot
>> parameters. Parsing of parameter strings is done via the already
>> existing boot parameter parsing function which is extended a little
>> bit.
>>
>> Parameter settings can either be specified in configuration files of
>> domains or cpupools, or they can be set via new xl sub-commands.
> 
> Without having looked at any of the patches yet (not even their
> descriptions) I'm still wondering what the benefit of textual parameters
> really is: Just like "binary" ones, they become part of the public
> interface, and hence subsequently can't be changed any more or
> less than the ones we currently have (in particular, anything valid in
> a guest config file will imo need to remain to be valid and meaningful
> down the road).

So lets look what would be needed for adding something like the
per-domain xpti parameter using binary interfaces:

1 an extension of some domctl interface, maybe bumping of the domctl
  interface version
2 adding the logic to domctl handling
3 adding libxc support
4 adding libxl support
5 adding a new xl sub-command
6 adding domain config support
7 adding documentation

With my approach only 2 (in a modified form, parameter handling instead
of domctl, but comparable in the needed effort) and 7 are needed.

So once the framework is in place it is _much_ easier to add new
features.


Juergen

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