One more detail here, then Xen versions:
m1.large, passed: 3.4.3-2.6.18 (preserve-AD)
m1.large, failed: 3.0.3-rc5-8.1.14.f
t1.micro32, failed: 3.1.2-128.1.10.el5 (preserve-AD)
The primary bug likely is domU selecting mwait_idle. This should be hlt. I may be possible that some change tried to make it available for dom0 and does not fence correctly. At least there seems to be a bit of a relation to the hypervisor version of the host as well.
One more detail here, then Xen versions:
m1.large, passed: 3.4.3-2.6.18 (preserve-AD)
m1.large, failed: 3.0.3-rc5-8.1.14.f
t1.micro32, failed: 3.1.2-128.1.10.el5 (preserve-AD)
The primary bug likely is domU selecting mwait_idle. This should be hlt. I may be possible that some change tried to make it available for dom0 and does not fence correctly. At least there seems to be a bit of a relation to the hypervisor version of the host as well.