How do I emulate the vmx feature with QEMU?

Question

I read from here that vmx capability support on QEMU must be explicitly enabled by providing the +vmx option to the command but the problem is that it does not seem to work. In

Answer 1

The following command works for me:

qemu-system-x86_64 -cpu host -kernel kernel/kernel -serial stdio -enable-kvm

-cpu host makes QEMU report host CPU features inside the VM (so your CPU must support vmx)

-enable-kvm is required by -cpu host

Even though according to this -cpu qemu64,+vmx should work, it doesn't work for me either.

Answer 2

No, the vmx flag is not supported in the processor emulation mode of QEMU. In order to use vmx in QEMU, you must use KVM with QEMU (replacing -no-kvm with -enable-kvm); and your host processor must support vmx.

In this document it shows the nested vmx instructions support in the Linux KVM; meaning this feature must be used with -enable-kvm.

In my test the options -enable-kvm -cpu kvm64,+vmx work, as the vmx feature is detected in the guest OS.