Re: [Xen-devel] [PATCH 2] Add user PM control interface

[Keir Fraser <keir.fraser@xxxxxxxxxxxxx>]

On 10/12/2008 10:04, "Keir Fraser" <keir.fraser@xxxxxxxxxxxxx> wrote:

> The only reason for dom0 kernel not to use domctl/sysctl is that the
> structures may be subject to change. So if you do, then the dom0 kernel in
> that case becomes part of the 'matched set' with Xen itself and the tools.
> As a distributor of 'whole system' software, you may not actually care about
> this limitation (since you can track dependencies and easily cause all
> packages to be upgraded)?
> 
> Adding some domctl/sysctl usage in the Linux kernel would actually be fine
> by me, except that I do think it should be conditional on a Kconfig option
> that makes the above additional constraint very clear to the user.
> 
> And actually, I don't think we've broken sysctl/domctl compatibility, or
> changed their ABI version numbers, at all recently.

Thinking some more, this doesn't work well unless we start guaranteeing
source compatibility at least... Perhaps it's time now to make stronger
guarantees about the domctl and sysctl interfaces.

Really in this case it depends: is support for Linux pm tools going to be
practically useful, especially in the general cases such as #dom0-cpus !=
#physical-cpus? It does seem a bit dubious to me.

 -- Keir



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