1 files changed, 67 insertions, 0 deletions
diff --git a/include/qemu/atomic.h b/include/qemu/atomic.h
new file mode 100644
index 0000000000..96a194bbee
--- /dev/null
+++ b/include/qemu/atomic.h
@@ -0,0 +1,67 @@
+#ifndef __QEMU_BARRIER_H
+#define __QEMU_BARRIER_H 1
+
+/* Compiler barrier */
+#define barrier()   asm volatile("" ::: "memory")
+
+#if defined(__i386__)
+
+#include "qemu/compiler.h"        /* QEMU_GNUC_PREREQ */
+
+/*
+ * Because of the strongly ordered x86 storage model, wmb() and rmb() are nops
+ * on x86(well, a compiler barrier only).  Well, at least as long as
+ * qemu doesn't do accesses to write-combining memory or non-temporal
+ * load/stores from C code.
+ */
+#define smp_wmb()   barrier()
+#define smp_rmb()   barrier()
+/*
+ * We use GCC builtin if it's available, as that can use
+ * mfence on 32 bit as well, e.g. if built with -march=pentium-m.
+ * However, on i386, there seem to be known bugs as recently as 4.3.
+ * */
+#if QEMU_GNUC_PREREQ(4, 4)
+#define smp_mb() __sync_synchronize()
+#else
+#define smp_mb() asm volatile("lock; addl $0,0(%%esp) " ::: "memory")
+#endif
+
+#elif defined(__x86_64__)
+
+#define smp_wmb()   barrier()
+#define smp_rmb()   barrier()
+#define smp_mb() asm volatile("mfence" ::: "memory")
+
+#elif defined(_ARCH_PPC)
+
+/*
+ * We use an eieio() for wmb() on powerpc.  This assumes we don't
+ * need to order cacheable and non-cacheable stores with respect to
+ * each other
+ */
+#define smp_wmb()   asm volatile("eieio" ::: "memory")
+
+#if defined(__powerpc64__)
+#define smp_rmb()   asm volatile("lwsync" ::: "memory")
+#else
+#define smp_rmb()   asm volatile("sync" ::: "memory")
+#endif
+
+#define smp_mb()   asm volatile("sync" ::: "memory")
+
+#else
+
+/*
+ * For (host) platforms we don't have explicit barrier definitions
+ * for, we use the gcc __sync_synchronize() primitive to generate a
+ * full barrier.  This should be safe on all platforms, though it may
+ * be overkill for wmb() and rmb().
+ */
+#define smp_wmb()   __sync_synchronize()
+#define smp_mb()   __sync_synchronize()
+#define smp_rmb()   __sync_synchronize()
+
+#endif
+
+#endif