LXR qemu/qemu-barrier.h

   1#ifndef __QEMU_BARRIER_H
   2#define __QEMU_BARRIER_H 1
   3
   4/* Compiler barrier */
   5#define barrier()   asm volatile("" ::: "memory")
   6
   7#if defined(__i386__)
   8
   9/*
  10 * Because of the strongly ordered x86 storage model, wmb() and rmb() are nops
  11 * on x86(well, a compiler barrier only).  Well, at least as long as
  12 * qemu doesn't do accesses to write-combining memory or non-temporal
  13 * load/stores from C code.
  14 */
  15#define smp_wmb()   barrier()
  16#define smp_rmb()   barrier()
  17/*
  18 * We use GCC builtin if it's available, as that can use
  19 * mfence on 32 bit as well, e.g. if built with -march=pentium-m.
  20 * However, on i386, there seem to be known bugs as recently as 4.3.
  21 * */
  22#if defined(__GNUC__) && __GNUC__ >= 4 && __GNUC_MINOR__ >= 4
  23#define smp_mb() __sync_synchronize()
  24#else
  25#define smp_mb() asm volatile("lock; addl $0,0(%%esp) " ::: "memory")
  26#endif
  27
  28#elif defined(__x86_64__)
  29
  30#define smp_wmb()   barrier()
  31#define smp_rmb()   barrier()
  32#define smp_mb() asm volatile("mfence" ::: "memory")
  33
  34#elif defined(_ARCH_PPC)
  35
  36/*
  37 * We use an eieio() for wmb() on powerpc.  This assumes we don't
  38 * need to order cacheable and non-cacheable stores with respect to
  39 * each other
  40 */
  41#define smp_wmb()   asm volatile("eieio" ::: "memory")
  42
  43#if defined(__powerpc64__)
  44#define smp_rmb()   asm volatile("lwsync" ::: "memory")
  45#else
  46#define smp_rmb()   asm volatile("sync" ::: "memory")
  47#endif
  48
  49#define smp_mb()   asm volatile("sync" ::: "memory")
  50
  51#else
  52
  53/*
  54 * For (host) platforms we don't have explicit barrier definitions
  55 * for, we use the gcc __sync_synchronize() primitive to generate a
  56 * full barrier.  This should be safe on all platforms, though it may
  57 * be overkill for wmb() and rmb().
  58 */
  59#define smp_wmb()   __sync_synchronize()
  60#define smp_mb()   __sync_synchronize()
  61#define smp_rmb()   __sync_synchronize()
  62
  63#endif
  64
  65#endif
  66