membarrier: introduce qemu/sys_membarrier.h

This new header file provides heavy-weight "global" memory barriers that
enforce memory ordering on each running thread belonging to the current
process.  For now, use a dummy implementation that issues memory barriers
on both sides (matching what QEMU has been doing so far).

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 17 insertions, 0 deletions

diff --git a/include/qemu/sys_membarrier.h b/include/qemu/sys_membarrier.h
new file mode 100644
index 0000000000..9ce7f5210b
--- /dev/null
+++ b/include/qemu/sys_membarrier.h
@@ -0,0 +1,17 @@
+/*
+ * Process-global memory barriers
+ *
+ * Copyright (c) 2018 Red Hat, Inc.
+ *
+ * Author: Paolo Bonzini <pbonzini@redhat.com>
+ */
+
+#ifndef QEMU_SYS_MEMBARRIER_H
+#define QEMU_SYS_MEMBARRIER_H 1
+
+/* Keep it simple, execute a real memory barrier on both sides.  */
+static inline void smp_mb_global_init(void) {}
+#define smp_mb_global()            smp_mb()
+#define smp_mb_placeholder()       smp_mb()
+
+#endif