Hi, Please let me know in case I am posting my question to the wrong forum. I apologize if that is the case! Here is my question: We run CentOS 6.3 on a server with dual Xeon CPU's. Our "dual blade" server uses this motherboard: http://www.supermicro.com/products/motherboard/Xeon/C600/X9DRT-HF.cfm We have two of these CPUs installed and working: Intel(R) Xeon(R) CPU E5-2620 0 @ 2.00GHz ( http://ark.intel.com/products/64594/Intel-Xeon-Processor-E5-2620-15M-Cache-2_00-GHz-7_20-GTs-Intel-QPI ) cat /proc/cpuinfo correctly reports a total of 24 cores (2 x 6 phisycal cores plus 2 x 6 hyperthreading cores) However, I get this output from virsh nodeinfo : # virsh nodeinfo CPU model: x86_64 CPU(s): 24 CPU frequency: 2000 MHz CPU socket(s): 1 Core(s) per socket: 6 Thread(s) per core: 2 NUMA cell(s): 2 Memory size: 16303552 kB As you can see, virsh nodeinfo reports only 1 CPU socket while in fact we have two CPU's. I would like to know if this is normal? Why does virsh reports only one physical CPU ?? Also, when we try to run a guest OS (Debian Linux "squeeze") with more than 4 vcpu's assigned to the VM, the guest OS won't boot up. The guest's kernel stuck on a screen right after it detected the /dev/vda block device and its partitions. We're using the VirtIO driver, of course. If I assign only 4 (or less) vcpu's to the guest OS it works fine. I have tried to upgrade the Linux kernel on the guest from debian backports, it did not help, we're experiencing the same issue with both the 2.6.32 and 3.2 Linux kernels. What could be causing this? On the host, we use the Linux kernel that came with CentOS 6.3 : 2.6.32-279.11.1.el6.x86_64 #1 SMP Tue Oct 16 15:57:10 UTC 2012 x86_64 x86_64 x86_64 GNU/Linux Thanks, Zoltan