FEX Awaits The Linux Kernel To Align With Windows & macOS On ARM Register Usage
FEX 2611 continues its x86-on-AArch64 JIT work and prepares for a proposed Linux change that would expose the current CPU number through TPIDRRO_EL0.
Linux currently returns zero there; FEX says a fast userspace CPU identifier would help emulate x86 CPU-identification instructions, especially under Wine. The kernel change is not merged: maintainers have raised the cost of reserving the register for this use.