RE: pv 2.6.31 (kernel.org) and save/migrate, domU BUG()

[Dan Magenheimer <dan.magenheimer@oracle.com>]

> > > > machine and it fails to save also.  Are you able to save
> > > > 2.6.31{,.5} successfully?  On latest xen-unstable?
> > > > (NOTE: Yes, I do have CONFIG_XEN_SAVE_RESTORE=y... don't
> > > > know if that is important.)
> 
> Ok. I just tried with a Fedora 12 (rawhide) PV guest. I was able to 
> "xm save" and "xm restore" it without problems. 
> 
> But I noticed there was a BUG printed on the guest console:
> http://pasik.reaktio.net/xen/debug/dmesg-2.6.31.5-122.fc12.x86
> _64-saverestore.txt
> BUG: sleeping function called from invalid context at 
> kernel/mutex.c:94
> in_atomic(): 0, irqs_disabled(): 1, pid: 1052, name: kstop/0
> Pid: 1052, comm: kstop/0 Not tainted 2.6.31.5-122.fc12.x86_64 #1

Ok, so it appears there is something problematic with
saving an upstream kernel.  It might be (partially) fixed
in Fedora 12 or maybe there is some other environmental
difference which makes save fail entirely on my system.

> > The results explain why I can get it to run on
> > one machine (an older laptop) and not run on another
> > machine (a Nehalem system)... looks like this is maybe
> > related to the cpuid-extended-topology-leaf bug that Jeremy
> > sent a fix for upstream recently.
> 
> Did you try with that patch applied? 

No, the patch wasn't posted, just a pull request to Linus,
so I don't have the patch (and am not a git expert so
am not sure how to get it).

http://lists.xensource.com/archives/html/xen-devel/2009-11/msg00182.html

So I'll try it again when .6 or .7 is available.