ARM has today posted their set of patches that implements core Linux kernel support for AArch64, the ARM 64-bit architecture.
Catalin Marinas of ARM posted to the Linux kernel mailing list a set of 36 patches that provides this initial 64-bit ARMv8 architecture support. "ARM introduced AArch64 as part of the ARMv8 architecture and consists of a substantially revised exception model (with 4 exception levels: EL0 - user, EL1 - kernel, EL2 - hypervisor, EL3 - secure monitor), new A64 instruction set based on larger register file, new FP/SIMD instructions. The new ABI is LP64 and takes advantage of the larger register file and mandates FP."
ARM previously published the AArch64 documentation concerning the instruction set and ABI but now it's met by nearly 23,000 lines of new arch/ code for the Linux kernel.
For some additional information from the mailing list announcement: