We observed a 2.6.18.8 dom0 kernel crash when Xen has maxcpus < num of 
physical cores (maxcpus=4 for a 12-core system). It appeared that 
hypervisor doesn't check whether CPU is online or not. This small patch 
fixed the issue.

Signed-off-by: Uwe Dannowski <uwe.dannowski@amd.com>
Acked-by: Wei Huang <wei.huang2@amd.com>