Re: [Xen-devel] Re: [PATCH] xen: fix XEN_SAVE_RESTORE Kconfig dependencies

["Jan Beulich" <JBeulich@xxxxxxxxxx>]

>>> On 23.02.11 at 12:10, Ian Campbell <Ian.Campbell@xxxxxxxxxxxxx> wrote:
> On Wed, 2011-02-23 at 10:58 +0000, Jan Beulich wrote:
>> >>> On 23.02.11 at 10:08, Ian Campbell <Ian.Campbell@xxxxxxxxxxxxx> wrote:
>> > On Wed, 2011-02-23 at 07:27 +0000, Shriram Rajagopalan wrote:
>> >> Make XEN_SAVE_RESTORE user visible and enable HIBERNATION and SWAP,
>> >> if this option is enabled.
>> > 
>> > I was under the (perhaps mistaken?) impression that selecting user
>> > visible Kconfig symbols was verboten since it has side-effects which
>> > make it hard for users to figure out why something cannot be switched
>> > off and/or how to turn things on etc.
>> > 
>> > In any case I think I preferred the "depends HIBERNATION" idea -- I
>> > thought that was the consensus of the thread too?
>> 
>> Why HIBERNATION (and SWAP) instead of SUSPEND? Xen doesn't
>> support the former (other than the latter)...
> 
> HIBERNATION provides the FREEZE, THAW and RESUME methods which we would
> like to use to integrate save/restore/checkpoint with the PM core i.e.
> choose THAW vs. RESUME based on whether the suspend was cancelled (aka a
> checkpoint) or not. See Shriram's other recent patch for details.

But imo it's nevertheless wrong to select HIBERNATION (and bogus
to select SWAP), as that'll create to user space the impression that
the kernel is capable of doing hibernation, which is wrong. If you
need the particular PM operations but no hibernation, then an
intermediary option will need to be introduced.

Jan


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