Re: [PATCH for-4.7] docs: Feature Levelling feature document

[Andrew Cooper <andrew.cooper3@citrix.com>]

On 01/06/16 13:14, Ian Jackson wrote:
> Andrew Cooper writes ("Re: [PATCH for-4.7] docs: Feature Levelling feature document"):
>> On 01/06/16 11:25, Ian Jackson wrote:
>>> I would prefer a wording which was more encouraging to future
>>> improvements.  Shall I suggest something ?
>> I guess there are two different issues here.  (Note: I am specifically
>> distinguishing `xl` as a toolstack itself, from libxl which is a just a
>> library.)
>>
>> Simply exposing the levelling/featureset information in `xl info` is
>> certainly a possible thing to do.  Joao has some plans for surfacing the
>> levelling information in libxl for libvirt to use.
> Right.
>
>> However, without a fundamental redesign of how xl works, it isn't going
>> to gain multi-host knowledge and consideration during domain creation.
> IMO xl ought to have the moving parts necessary to allow an
> administrator to: 1. collect feature information from their hosts;
> 2. combine that information into the desired feature set to expose to
> guests; 3. specify the feature set in their host configuration; 4. do
> all of the above conveniently, without seddery.
>
> We should assume that the administrator has available tools like
> GNU parallel, ansible, or whatever.
>
> I don't want to design this now but I do want the feature levelling
> documentation to welcome suggestions for it, or at least not to seem
> to rule it out.

1) is currently available via the `xen-cpuid` binary introduced,
although I intended it more as a developer tool

Combining is the awkward part, but in the common case, it is just a
bitwise AND of the bitmaps provided by `xen-cpuid`.

3) I don't know what you mean about their host configuration.  Do you
mean guest configuration?

All of this works in combination with the existing cpuid= guest
configuration.

~Andrew

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