From 462cda505f304c3915e5e30429cee22418f5a6ea Mon Sep 17 00:00:00 2001 From: "Emilio G. Cota" Date: Wed, 8 Jun 2016 14:55:22 -0400 Subject: [PATCH] include/processor.h: define cpu_relax() MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Taken from the linux kernel. Reviewed-by: Sergey Fedorov Reviewed-by: Richard Henderson Reviewed-by: Alex Bennée Signed-off-by: Emilio G. Cota Message-Id: <1465412133-3029-5-git-send-email-cota@braap.org> Signed-off-by: Richard Henderson --- include/qemu/processor.h | 30 ++++++++++++++++++++++++++++++ 1 file changed, 30 insertions(+) create mode 100644 include/qemu/processor.h diff --git a/include/qemu/processor.h b/include/qemu/processor.h new file mode 100644 index 0000000000..8b2570283a --- /dev/null +++ b/include/qemu/processor.h @@ -0,0 +1,30 @@ +/* + * Copyright (C) 2016, Emilio G. Cota + * + * License: GNU GPL, version 2. + * See the COPYING file in the top-level directory. + */ +#ifndef QEMU_PROCESSOR_H +#define QEMU_PROCESSOR_H + +#include "qemu/atomic.h" + +#if defined(__i386__) || defined(__x86_64__) +# define cpu_relax() asm volatile("rep; nop" ::: "memory") + +#elif defined(__ia64__) +# define cpu_relax() asm volatile("hint @pause" ::: "memory") + +#elif defined(__aarch64__) +# define cpu_relax() asm volatile("yield" ::: "memory") + +#elif defined(__powerpc64__) +/* set Hardware Multi-Threading (HMT) priority to low; then back to medium */ +# define cpu_relax() asm volatile("or 1, 1, 1;" \ + "or 2, 2, 2;" ::: "memory") + +#else +# define cpu_relax() barrier() +#endif + +#endif /* QEMU_PROCESSOR_H */