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[GUIDE] Unlocking CFG with OpenCore and CFGLock.efi


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What is CFG Lock and MSR 0xE2?

 

CFG Lock is a BIOS setting that allows writing to a specific register, in this case MSR E2 (MSR = Model Specific Register). An MSR consists of one or more registers in blocks of instructions used to do certain tasks on a CPU. MTRs are also used to control CPU's access to memory ranges. Commands capable of reading and writing to MSR work with elevated privileges (the operating system, primarily).

Many motherboards come from factory with MSR E2 region locked (read but not write) and quite a few of them even hide this option in BIOS user interface. In those that do show the option to block or unblock this variable, it is usually called CFG Lock. CFG Lock is a bit with 2 values, 0x1 or 0x0. When it is 0x1, macOS cannot write into this region and kernel patches are required.

macOS wants to write this registry, both the Kernel and AppleIntelPowerManagement. It defines the C-states of the CPU, which is why it is essential for macOS. Without the ability to write to MSR E2, all or most of the CPU power management is lost and the system does not boot.

In Clover 2 patches have been used: KernelPM (for AppleIntelPowerManagement.kext) and KernelXCPM (for the kernel). In OpenCore 2 others have been used: AppleCpuPmCfgLock (for AppleIntelPowerManagement.kext) and AppleXcpmCfgLock (for the kernel). These patches fix the problem but the registry is still read-only. To ensure native CPU power management, CFG Lock bit must be set to 0x0.

To achieve this, the firmware must be modified to support writing to MSR E2. This method is preferred over Clover and OC patches, it generates greater system stability and the CPU power management more closely resembles that of a real Mac. The methods that are usually proposed for this task are too complex for most users who do not have a high level of knowledge, requiring specialized tools and even modified Grub.

Below I comment on an alternative method that is much simpler and that, at least in my case, seems to have been successful. Like any of the methods that modify this bit, it has the risk of not working or even damaging the BIOS, so if you try it it is under your entire responsibility.

CFGLock.efi

User @Brumbaer has a tool called CFGLock.efi (see post). It is an EFI application, it has to be installed in OC Tools folder (Misc - Tools in config.plist) and in this way it is available in the OC menu next to Reset NVRAM. It should be accompanied by another tool included in the OC package called VerifyMsrE2.efi that reports current status of CFG Lock (locked / unlocked).

When CFGLock.efi runs, it displays information (CFG variable found, varstore in which it resides, current reading and requests user intervention to make the change from 0x1 to 0x0 or vice versa). Then you have to restart. With VerifyMsrE2.efi we can check if the change has been successful.

Both EFI applications can be run by selecting them directly in the OC menu but it is also possible, by installing OpenShell.efi tool, to run this shell and running them from there. Information for handling OpenShell.efi is available in OC and elsewhere.

 

oc-menu.thumb.png.cb62e720820f5aad2297381290e7e8c7.png

 

After CFGLock.efi


I have tried CFGLock.efi and apparently it has worked well.
 

  1. macOS boots up and works fine with the OC patches AppleCpuPmCfgLock and AppleXcpmCfgLock disabled.
     
  2. VerifyMsrE2.efi reports "This firmware has UNLOCKED MSR 0XE2 register!".
     
  3. Hackintool in Utilities - Get AppleIntelInfo displays this text:
    AppleIntelInfo.kext v3.0 Copyright © 2012-2017 Pike R. Alpha. All rights reserved.
    IA32_MISC_ENABLES................(0x1A0) : 0x850089
    ------------------------------------------
    - CFG Lock............................. : 0 (MSR not locked)
    Note: Hackintool current version (3.4.6) doesn't show text after Get AppleIntelInfo in Big Sur beta 10. It's got from Catalina.
     
  4. Intel Power Gadget - Frequency graph shows variations between maximum and minimum suggestive of CPUPM.

 

cpupm.png.f7f36d99fd17e900e5d73cee2bdcd6cf.png

Edited by miliuco
  • 3 weeks later...

Note: Gigabyte has published (09/16/2020) a new BIOS for my Z390 Aorus Elite board, it is the F10g version and the main novelty, at least in the graphical interface, is the presence of a new option to block or unblock CFG so this task is much easier from now on.

cfg0.jpg.5aca27cb6feb2179f61c0726b63e20f7.jpg

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