Re: [Xen-users] Hibernation

[Mark Williamson <mark.williamson@xxxxxxxxxxxx>]

> I understand that currently the standard hibernation mechanisms of
> operating systems cannot be used with Xen.
> With Xen, it is possible to use xm save/xm restore which is in its effect
> quite similar, but I am a bit scared that this might cause problems within
> the affected OS because after restore, the system clock will show a great
> leap. This is also true with "native" hibernation, but the OS is aware of
> this and can react accordingly when it is woken up again.
> Does anybody know if this really can cause trouble or if - in the PV case -
> the kernel is patched so to that similar actions are taken as when the OS
> resumes from hibernation?

Paravirtualised guests are aware of the suspend / resume and are required to 
actively co-operate with it; therefore they ought to work fine.  This doesn't 
stop userspace apps getting a bit confused by the jump in time, but this is 
no more the case for Xen than any OS suspend / resume mechanism.

> Recently, I saw a patch on the xen-devel mailinglist that adds S3 support.
>
> >From my understanding, the potential problems that I have described above
>
> would be circumvented if the DomU is put into S3 state and then saved using
> xm save?

Suspend / resume for HVM guests is in 3.1 but I'm not sure if or how it 
handles things like time jumps from the guest's PoV.  S3 isn't currently used 
as part of this; I'm not entirely sure what's going on in the power 
management area, but I do know there are general efforts to allow host low 
power states to work.

Cheers,
Mark

-- 
Dave: Just a question. What use is a unicyle with no seat?  And no pedals!
Mark: To answer a question with a question: What use is a skateboard?
Dave: Skateboards have wheels.
Mark: My wheel has a wheel!

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