I've got a VM that is running as a guest on an open stack compute node. I would like to run kvm within my guest but my guest VM's /proc/cpuinfo reports the vmx flag is missing (and kvm doesn't work). lscpu run from my guest shows the following:

Vendor ID: GenuineIntel
CPU family: 6
Model: 42
Stepping: 1
CPU MHz: 2593.750
BogoMIPS: 5187.50
Hypervisor vendor: KVM
Virtualization type: full

What might cause my guest VM to not have the vmx flag set?

Thanks

You are running inside a VM, of course VMX will be missing. To get it, you need to have nesting enabled on the host, and even with nesting enabled, performance will be petty bad.

If you cannot enable nesting on the host, I suggest you use containers or a virtualization system that doesn't require VT/SVM

Thanks for the reply. Yes I need nested virtualization-- for my application I need to run kvm inside my guest VM. Containers etc aren't an option. This is functional work, not performance oriented work so performance isn't a concern. Note that I have dozens of guest VM's where they see the vmx flag set and only a handful of guest VM's don't see the vmx flag-- and all these VM's are booting from the same image. I'm looking for specific config's that should be present on the compute host to make sure the vmx flag is passed- apparently that config is present in most of the compute hosts but not all.

Notice that the lscpu output below from the guest VM shows full virtualization enabled-- but the vmx flag is not set in /proc/cpuinfo-- does this provide any insight into what config is missing on the compute host?

Thanks

Why don't you start by providing some details on what you have on the hosts, how it is set up at the moment, VM XML dumps, loaded modules, distros etc? All the telepathic LQ members are on vacation today, I am truly sorry

Funny! Me either! Unfortunately, I don't have access to the underlying host or corresponding setup-- this is being done on a 3rd party Openstack setup. So i'm looking to understand what might prevent the VMX flag to not get passed from the host to the guest -- as this would help seed the reviews steps the 3rd party Ops folks would need to check. Insights? And what does it mean for lscpu to report full virtualization yet no vmx flag is present?

Thanks

ah, so we're starting to glimpse some of those coveted details, wonderful.

first of all, you need to understand that nesting isn't something normally done, because, besides providing a sluggish testbed for distrohopping, there isn't much use for it. which logically means, that normally, it is disabled, and if you really need it you have to enable it, while you seem to be under the impression that it's the other way around, and some horrible person disabled it to spite you.

Now that we know this is openstack we're talking about (thanks so much for letting at least some information slip), I know what to look for, and it is "enable nested kvm openstack".

Sounds easy all of a sudden, right?

http://dachary.org/?p=1318

You're welcome.