[CentOS-virt] KVM + virsh nodeinfo + CentOS 6.3

Wed Oct 24 15:14:29 UTC 2012
Zoltan Frombach <zoltan at frombach.com>


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:

We have two of these CPUs installed and working:
Intel(R) Xeon(R) CPU E5-2620 0 @ 2.00GHz

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