Re: [Qemu-devel] [PATCH v13 1/8] save/load cpu runstate

[Hu Tao]

On Thu, Feb 28, 2013 at 02:12:37PM -0700, Eric Blake wrote:
> On 02/28/2013 05:13 AM, Hu Tao wrote:
> > This patch enables preservation of cpu runstate during save/load vm.
> > So when a vm is restored from snapshot, the cpu runstate is restored,
> > too.
> 
> What happens if a management app wants to override the runstate when
> restoring the domain?  I can think of several useful scenarios:
> 
> 1. management app pauses the guest, then saves domain state and other
> things (management state, or disk clones), then resumes the guest.
> Later, the management wants to revert to the saved state, but have the
> guest running right away.  I guess here, knowing that the guest was
> saved in a paused state doesn't hurt, since the management app can
> resume it right away.
> 
> 2. management app saves domain state of a live guest, then copies that
> state elsewhere.  In its new location, the management app wants to
> investigate the state for forensic analysis - so even though the guest
> remembers that it was running, management wants to start it paused.
> Here, it is important that there must not be a window of time where the
> guest can run, otherwise, the results are not reproducible.

-S takes precedence in the case. But for in-migration, runstate is
loaded from src.