Background: I'm working on a project that needs device tree like capability. Using the device tree OF driver works well and I don't want to create something that closely duplicates that functionality. When building a 32bit kernel, all works fine. However when building a 64bit kernel, the linking stage fails with an unresolved symbol: apic_force_enable This symbol is getting called from arch/x86/kernel/devicetree.c and is defined in arch/x86/kernel/apic/apic.c but only when !CONFIG_X86_64 I see two possible fixes but as I'm unfamiliar with this area of the kernel I don't know which would be a better choice. 1) in arch/x86/kernel/apic/apic.c, define the apic_force_enable() function in the X86_64 bit path and have it return 0. Something like: int __init apic_force_enable(unsigned long addr) { return 0; } 2) wrap the call to apic_force_enable with a #ifndef CONFIG_X86_64 in devicetree.c. Something like : #ifndef CONFIG_X86_64 if (apic_force_enable(r.start)) return; #else return; #endif I've been using #1 successfully in my development and it seems like it would be the best choice long term. I'm looking for some validation that this makes sense and if so, I'll submit a patch to lkm with the fix.