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Re: [Xen-devel] per-domain configuration and inappropriate use of globals
- To: Juergen Gross <jgross@xxxxxxxx>, Xen-devel List <xen-devel@xxxxxxxxxxxxx>, Jan Beulich <JBeulich@xxxxxxxx>, Janakarajan Natarajan <Janakarajan.Natarajan@xxxxxxx>, Roger Pau Monne <roger.pau@xxxxxxxxxx>, Wei Liu <wei.liu2@xxxxxxxxxx>, Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>, Julien Grall <julien.grall@xxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>
- From: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
- Date: Mon, 22 Oct 2018 14:29:40 +0100
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- Delivery-date: Mon, 22 Oct 2018 13:30:27 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
- Openpgp: preference=signencrypt
On 19/10/18 19:22, Juergen Gross wrote:
> On 19/10/2018 18:57, Andrew Cooper wrote:
>> In practice, having fine grain control of all the features like would be
>> excellent for testing purposes, because it allows you to boot two
>> otherwise-identical VMs with one configuration difference between them.
>>
>> In the spirit of the already in progress domaincreate work, options like
>> these should be selectable at domain creation time, and immutable
>> thereafter.
>>
>> That said, there is a plethora of tweakables, and I'm not sure how best
>> to expose them. While most (all?) of these options are inherently
>> supported (as playing with them simulates what Xen would chose on
>> different hardware), I expect there will be ample opportunity for people
>> to break their systems if they tweak too much.
>>
>> Is there liable to be any provision in xl/libxl to have "unstable"
>> configuration, which is easily identified as "may stop working / cease
>> to exist / become invalid at any point in the future?"
>>
>> Alternatively, are there any other suggestions for alternative mechanisms?
> Per-domain parameters like in my series? You could guard the "dangerous"
> ones by a global parameter (boot-time or run-time settable).
I was hoping to separate the discussion of what information should be
configurable, from the mechanism we used to provide said information.
Using a text-based mechanism suffers from the same stable/unstable
issues as xl.cfg, so the same concern applies there.
(Also, I have a separate uneasy feeling about having yet more string
parsing in the hypervisor, but that is definitely unrelated).
~Andrew
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