include/qemu/processor.h

   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 */