Installing OSX Lion into VMware Fusion on Macbook 2012 gets “cpu disabled by guest operating system” error.

In order to install OS X Lion into a virtual machine running under VMware Fusion, you need the install file from the Mac App store.  In this case, I started with:

  • the Mac App store file “Install Max OS X Lion_10.7.3.app”
  • VMware Fusion 4.1.1
  • Macbook Air 13″ mid-2012

I’ve run OS X Lion under VMs previously, so expected this should work without any difficulties.  I expected wrong.

Attempting to start a new VM resulted in a Fusion error message stating, “The CPU has been disabled by the guest operating system…”

To troubleshoot I:

  1.  started by checking for Fusion updates; the in app update check didn’t show any available updates.
  2. Next I decided to try a reinstall of Fusion.  Deleted the app, rebooted, and went to vmware.com to download a fresh copy.  Found a newer version 4.1.3  Trying this version resulted in same CPU error.
  3. Did some additional searching and found a vmware forum thread which referred to a work around listed in another vmware forum thread.

Here’s a summary of the solution to save the time of going through all of the forum thread references.

The physical Intel CPU in the mid-2012 MacBooks is new.  As a result, if you are using a Mac App store installation file for OS X obtained prior to the 2012 MacBooks, that version won’t understand the new processor.

The solution is to edit the configuration file of the OS X Lion virtual machine to add this entry

cpuid.1.eax = “—-:—-:—-:0010:—-:—-:1010:0111”

The configuration file will be located within the actual VM storage file.  You can use Finder to location the *.vmwarevm file, then right click to “Show Package Contents”.  The config file will be the *.vmx

Any easier way to open the VM’s configuration file is using the VMware Fusion Virtual Machine Library window.  Use the OPTION key + Right Click on the target VM.  An option to “Open Config File in Editor” will be available.

This solution should work on the following combinations of hardware software:

  • All mid-2012 MacBooks
  • VMware Fusion 4.1.3
  • OS X host operating system version Lion 10.7.4
  • OS X guest operating system versions Lion 10.7.3 or 10.7.4

VMware is working on a “Technology Preview 2012″ for OS X Mountain Lion 10.8  As of this writing the workaround for that version is different.    Hopefully VMware will clean this up prior to release the 2012 version.

If Apple releases a Mac App store installation package of Lion 10.7.5, that may also solve the VM CPU configuration issue.

Running OS X Lion in virtual machines is my preferred method of testing new versions of the iOS SDK and Apple’s iOS Device Management tools.  With a recent move to a 2012 MacBook Air 13” and the developer release of iOS v6, apparently it was time to encounter a new collection of configuration issues.

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