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__) || defined(__x86_64__)
   8
   9 /*
  10  * Because of the strongly ordered x86 storage model, wmb() is a nop
  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
  17 #elif defined(__powerpc__)
  18
  19 /*
  20  * We use an eieio() for a wmb() on powerpc.  This assumes we don't
  21  * need to order cacheable and non-cacheable stores with respect to
  22  * each other
  23  */
  24 #define smp_wmb()   asm volatile("eieio" ::: "memory")
  25
  26 #else
  27
  28 /*
  29  * For (host) platforms we don't have explicit barrier definitions
  30  * for, we use the gcc __sync_synchronize() primitive to generate a
  31  * full barrier.  This should be safe on all platforms, though it may
  32  * be overkill.
  33  */
  34 #define smp_wmb()   __sync_synchronize()
  35
  36 #endif
  37
  38 #endif