1 /* 2 * Copyright (C) 2016, Emilio G. Cota <cota@braap.org> 3 * 4 * License: GNU GPL, version 2. 5 * See the COPYING file in the top-level directory. 6 */ 7 #ifndef QEMU_PROCESSOR_H 8 #define QEMU_PROCESSOR_H 9 10 #include "qemu/atomic.h" 11 12 #if defined(__i386__) || defined(__x86_64__) 13 # define cpu_relax() asm volatile("rep; nop" ::: "memory") 14 15 #elif defined(__aarch64__) 16 # define cpu_relax() asm volatile("yield" ::: "memory") 17 18 #elif defined(__powerpc64__) 19 /* set Hardware Multi-Threading (HMT) priority to low; then back to medium */ 20 # define cpu_relax() asm volatile("or 1, 1, 1;" \ 21 "or 2, 2, 2;" ::: "memory") 22 23 #else 24 # define cpu_relax() barrier() 25 #endif 26 27 #endif /* QEMU_PROCESSOR_H */ 28