Problem with KVM-84 and more than 4 processors

Matthias Hovestadt
2009-03-03T15:01:49Z

Hi!

I have a system with 2 processors and 4 cores each, which sums
up to 8 processors in total. I installed the system with Gentoo.2008
and KVM-84.

Linux asok04 2.6.27-gentoo-r8 #1 SMP Tue Mar 3 11:34:26 CET 2009 x86_64
Intel(R) Xeon(R) CPU X5355 @ 2.66GHz GenuineIntel GNU/Linux

Everything is running fine as long as I do not change the default
setting of CONFIG_NR_CPUS=4 in the kernel config:

asok04 ~ # lsmod
Module Size Used by
kvm_intel 39176 1
kvm 137072 1 kvm_intel
scsi_wait_scan 1664 0
asok04 ~ #

All KVM modules are loaded and I'm perfectly able to start and use
virtual guests.

However, if I increase CONFIG_NR_CPUS to any number higher than 4, the
additional processors of my system are listed in /proc/cpuinfo, but
this is the output of lsmod:

asok04 ~ # lsmod
Module Size Used by
kvm 137072 283728377
scsi_wait_scan 1664 0
asok04 ~ #

Manually loading the kvm_intel module fails with an "Cannot allocate
memory" error. Also starting VMs fails since he is unable to find
/dev/kvm.

This mail seems to be somehow related to the bug report of Justin Keogh
from 30th Dec 2008. He was able to fix his problem by simply setting
CONFIG_KVM=m, but I'm already using modules, so his workaround can't be
applied here.

Thanks in advance for your help,
Matthias