[Xen-devel] CONFIG_SMP required for save/restore and migration: bug?

[Luca Lesinigo <luca@xxxxxxxxxxx>]

Dear list, I was about to write here seeking for help because my Ubuntu domUs 
were migrating just fine while my Gentoo ones were just hanging "freezed" after 
attempting migration, or after saving and restoring on the same node.

After some more tinkering around, I nailed the issue to my kernel config which 
was stripped down to the bare minimum: no hardware drivers, no loadable 
modules... and no SMP. After enabling SMP support my domU were able to migrate 
without problems. The same happens on 3.2.x and on 3.10.7 kernels.

Before playing with many different kernel configurations, I searched Xen's wiki 
and googled around but could not find anything related to this issue.

So: with my config, non-SMP kernels will freeze after restore, while activating 
CONFIG_SMP and nothing else will make this problem disappear. Maybe non-SMP 
kernels are supposed to migrate but there's a software problem, or maybe SMP is 
a requirement but is not documented (or at least I wasn't able to find it). 
Maybe it's not CONFIG_SMP but one of its dependencies.

Either way, I'm writing to the list to report this experience, maybe it is a 
(software or documentation) bug?

I'll keep an eye to the list in the next days, if you need any other detail 
just ask.

Thank you for developing Xen, keep up with the good work!

--
Luca Lesinigo


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