xref: /qemu/include/qemu/processor.h (revision ab5f8fc7)
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 #if defined(__i386__) || defined(__x86_64__)
11 # define cpu_relax() asm volatile("rep; nop" ::: "memory")
12 
13 #elif defined(__aarch64__)
14 # define cpu_relax() asm volatile("yield" ::: "memory")
15 
16 #elif defined(__powerpc64__)
17 /* set Hardware Multi-Threading (HMT) priority to low; then back to medium */
18 # define cpu_relax() asm volatile("or 1, 1, 1;" \
19                                   "or 2, 2, 2;" ::: "memory")
20 
21 #else
22 # define cpu_relax() barrier()
23 #endif
24 
25 #endif /* QEMU_PROCESSOR_H */
26