[libvirt-users] a problem about nested vm

hi, I have a problem that confuse me so long. I run a guest os(VM1) on a physical machine(PM1) that had enabled virtualization . Now, I also want to run a guest os (VM2) under VM1,but VM1 print the following message to me: [2013-06-05 10:43:04,379][ERROR] machine:init_vm(57271)|state:init_vm|Create domain failed, unsupported configuration: Domain requires KVM, but it is not available. Check that virtualization is enabled in the host BIOS, and host configuration is setup to load the kvm modules.[2013-06-05 10:43:04,382][ERROR] machine:init_vm(57271)|state:init_vm|Create domain failed, unsupported configuration: Domain requires KVM, but it is not available. Check that virtualization is enabled in the host BIOS, and host configuration is setup to load the kvm modules.[2013-06-05 10:43:04,409][ERROR] machine:init_vm(57271)|state:init_vm|Create domain failed, unsupported configuration: Domain requires KVM, but it is not available. Check that virtualization is enabled in the host BIOS, and host configuration is setup to load the kvm modules.[2013-06-05 10:43:04,412][ERROR] machine:init_vm(57271)|state:init_vm|Create domain failed, unsupported configuration: Domain requires KVM, but it is not available. Check that virtualization is enabled in the host BIOS, and host configuration is setup to load the kvm modules.[2013-06-05 10:43:04,414][ERROR] machine:init_vm(57271)|state:init_vm|Create domain failed, unsupported configuration: Domain requires KVM, but it is not available. Check that virtualization is enabled in the host BIOS, and host configuration is setup to load the kvm modules.[2013-06-05 10:43:04,418][ERROR] machine:init_vm(57271)|state:init_vm|Create domain failed, unsupported configuration: Domain requires KVM, but it is not available. Check that virtualization is enabled in the host BIOS, and host configuration is setup to load the kvm modules.[2013-06-05 10:43:04,421][ERROR] machine:init_vm(57271)|state:init_vm|Create domain failed, unsupported configuration: Domain requires KVM, but it is not available. Check that virtualization is enabled in the host BIOS, and host configuration is setup to load the kvm modules.[2013-06-05 10:43:04,426][ERROR] machine:init_vm(57271)|state:init_vm|Create domain failed, unsupported configuration: Domain requires KVM, but it is not available. Check that virtualization is enabled in the host BIOS, and host configuration is setup to load the kvm modules.[2013-06-05 10:43:04,428][ERROR] machine:init_vm(57271)|state:init_vm|Create domain failed, unsupported configuration: Domain requires KVM, but it is not available. Check that virtualization is enabled in the host BIOS, and host configuration is setup to load the kvm modules.[2013-06-05 10:43:04,432][ERROR] machine:init_vm(57271)|state:init_vm|Create domain failed, unsupported configuration: Domain requires KVM, but it is not available. Check that virtualization is enabled in the host BIOS, and host configuration is setup to load the kvm modules. so, how can i enable the virtualization option in vm1??? thanks a lot. :)