kvm_amd missing in CentOS 7 virtual machine

fanoflq · 12-16-2016, 01:54 PM

I have a host with Linux Mint 18, and it has KVM like so:

Code:

/proc/sys/dev/cdrom $ lsmod | grep -i kvm
kvm_amd                65536  4
kvm                   540672  1 kvm_amd
irqbypass              16384  1 kvm

I am installing kvm on a CentOS7 virtual machine (VM) so I can run another CentOS7 VM inside this VM!
No, this is not a typo. I am doing it for learning purposes.
There are two way to install virtualization like so:

Quote:

#yum group install "Virtualization Host"
or
# yum install qemu-kvm qemu-img virt-manager libvirt libvirt-python libvirt-client virt-install virt-viewer

I tried both cases, but I am not able to install kvm_amd on my virtual machine.

Code:

[root@server1 ~]# modprobe kvm_amd
modprobe: ERROR: could not insert 'kvm_amd': Operation not supported

#from Centos7 VM, kvm_amd is missing!:
[root@server1 ~]# lsmod | grep -i kvm
kvm                   525409  0

What did I missed?
Thank you.

lazydog · 12-16-2016, 02:30 PM

You cannot run a VM in a VM.

Coffee!!! · 12-16-2016, 03:09 PM

What you're trying to attempt is called nested virtualization and is not usually supported in consumer grade products like VirtualBox and VMware Player (do they still call it that?). What virtualization client are you using to host your CentOS 7 VM?

fanoflq · 12-16-2016, 03:41 PM

Quote:

Originally Posted by lazydog

You cannot run a VM in a VM.

Incorrect, IMHO.

fanoflq · 12-16-2016, 03:41 PM

Quote:

Originally Posted by Coffee!!!

What you're trying to attempt is called nested virtualization and is not usually supported in consumer grade products like VirtualBox and VMware Player (do they still call it that?). What virtualization client are you using to host your CentOS 7 VM?

See OP at top.....

Coffee!!! · 12-19-2016, 08:18 AM

The confusion for me is that you didn't explicitly say what platform were hosting the VM on. You just compared the VM to your KVM setup on your Mint host. So the explanation to your problem is that your VM doesn't have a virtualization bit. When you look at the modules currently loaded on your Mint Host, you see KVM is supported because you have an AMD processor with virtualization support. As soon as you create a guest(VM) on top of the KVM host, you're not going to see virtualization support because its a virtual CPU and there is a layer of abstraction that prevents the guest from seeing the actual hardware of the host. There's a nice article on Wikipedia about virtualization that I think you should read (both Intel and AMD sections): https://en.wikipedia.org/wiki/X86_vi...on_.28AMD-V.29