Xen devel - Nov 2009 - Testing for domain states (before starting, before restarting, and after "save")

Is there a way (in the hypervisor) to test a domain to see if is created but has
not yet executed its first instruction (or has been restored/live-migrated but
has not yet executed its first instruction post-restore)?  Or to see if it has
been stopped in anticipation of a save (or live migrate) and will not execute
more instructions unless/until it is restored (or revived on the live-migrate
target machine)?

I''m writing routines for tsc_mode that assumes each of those conditions
and, rather than just comment about it, thought it would be nice to fail if the
assumption is incorrect.  If not (or if it is too complicated), I''ll
just use comments.

Thanks,
Dan


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Hi,

At 00:32 +0000 on 20 Nov (1258677171), Dan Magenheimer
wrote:
> Is there a way (in the hypervisor) to test a domain to see if is
> created but has not yet executed its first instruction (or has been
> restored/live-migrated but has not yet executed its first instruction
> post-restore)? 
I don''t think that''s explicitly available, but if
it''s paused and all
its vcpus'' scheduler stats are at zero, that''s probably good
enough for
the kind of sanity check you''re talking about.
> Or to see if it has been stopped in anticipation of a
> save (or live migrate) and will not execute more instructions
> unless/until it is restored (or revived on the live-migrate target
> machine)?
That''s easier: it''s shut down with shutdown code suspend. 
That doesn''t
mean it will never run again in this domain, because of the Remus
fast-resume path, but it does mean no more instructions executed before
some kind of resume.

Cheers,

Tim.
> I''m writing routines for tsc_mode that assumes each of those
conditions and, rather than just comment about it, thought it would be nice to
fail if the assumption is incorrect.  If not (or if it is too complicated),
I''ll just use comments.
> 
> Thanks,
> Dan
> 
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-- 
Tim Deegan <Tim.Deegan@citrix.com>
Principal Software Engineer, Citrix Systems (R&D) Ltd.
[Company #02300071, SL9 0DZ, UK.]

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