FEX 2611 Brings x86 Emulation to AArch64 Linux
The release lets Linux and Wine x86 and x86_64 applications run on AArch64 systems, while its developers await a kernel change to a shared register.
Updated on Nov. 6, 2026 in Semiconductors
FEX 2611 has been released to run x86 and x86_64 Linux and Wine games and applications on AArch64 Linux, and it includes JIT improvements. Its developers are still waiting on the Linux kernel to align its use of the TPIDRRO_EL0 register with Windows on ARM and macOS.
Why it matters
Under Linux the TPIDRRO_EL0 register always returns zero, while Windows on ARM and macOS use it to store the current CPU core index. FEX currently falls back on a getcpu system call instead, and the kernel has held the register at zero for about 15 years.
The release is FEX version 2611, and the Linux kernel has hardcoded the TPIDRRO_EL0 register to zero for about 15 years. Igalia's August patch would populate it with the running CPU of a native task, but whether it will be mainlined is not yet known.
The players
FEX
FEX is an open-source emulator project that translates x86 and x86_64 code to run on AArch64 systems.
Igalia
Igalia is a Spain-based open-source consultancy that contributes patches to the Linux kernel and other projects.
Will Deacon
Will Deacon is an ARM Linux kernel developer who warned that using TPIDRRO_EL0 for CPU core reporting would block other future uses of the register.
The details
FEX 2611 lets x86 and x86_64 Linux and Wine games and applications run on AArch64 Linux. Under Wine, FEX disabled the RDPID, RDTSCP, and CPUID instructions because Linux syscalls cannot be used there to emulate them, and it is waiting on TPIDRRO_EL0 to emulate them faster.
Timeline
August: Igalia sent a patch for reporting a native task's running CPU in TPIDRRO_EL0.
- 2026-11-06
FEX 2611 was released.
The Tech Race
Windows on ARM and macOS both store the current CPU core index in TPIDRRO_EL0, a convention that Linux has not followed for about 15 years. FEX's pending use of the register would bring Linux closer to that shared behavior on ARM64 hardware.
Users running x86 Linux and Wine games on ARM64 hardware can use FEX 2611 now, though some instructions such as RDPID, RDTSCP, and CPUID remain disabled under Wine. Faster emulation of those instructions depends on the Linux kernel accepting the TPIDRRO_EL0 change.
The takeaway
The FEX project shows that small kernel-level register conventions can determine how well emulation performs across operating systems. Readers following ARM64 compatibility should watch whether the Linux kernel adopts the proposed TPIDRRO_EL0 change.
Further reading
For related coverage of processor architecture and chip-level compatibility, see Semiconductors.
Source note: This article includes information reported by Phoronix.
