2 files changed, 51 insertions, 0 deletions
diff --git a/util/Makefile.objs b/util/Makefile.objs
index ae90b9963d..728c3541db 100644
--- a/util/Makefile.objs
+++ b/util/Makefile.objs
@@ -33,6 +33,7 @@ util-obj-y += throttle.o
 util-obj-y += getauxval.o
 util-obj-y += readline.o
 util-obj-y += rcu.o
+util-obj-$(CONFIG_MEMBARRIER) += sys_membarrier.o
 util-obj-y += qemu-coroutine.o qemu-coroutine-lock.o qemu-coroutine-io.o
 util-obj-y += qemu-coroutine-sleep.o
 util-obj-y += coroutine-$(CONFIG_COROUTINE_BACKEND).o
diff --git a/util/sys_membarrier.c b/util/sys_membarrier.c
new file mode 100644
index 0000000000..8dcb53e63e
--- /dev/null
+++ b/util/sys_membarrier.c
@@ -0,0 +1,50 @@
+/*
+ * Process-global memory barriers
+ *
+ * Copyright (c) 2018 Red Hat, Inc.
+ *
+ * Author: Paolo Bonzini <pbonzini@redhat.com>
+ */
+
+#include <qemu/osdep.h>
+#include <qemu/sys_membarrier.h>
+#include <qemu/error-report.h>
+
+#ifdef CONFIG_LINUX
+#include <linux/membarrier.h>
+#include <sys/syscall.h>
+
+static int
+membarrier(int cmd, int flags)
+{
+    return syscall(__NR_membarrier, cmd, flags);
+}
+#endif
+
+void smp_mb_global(void)
+{
+#if defined CONFIG_WIN32
+    FlushProcessWriteBuffers();
+#elif defined CONFIG_LINUX
+    membarrier(MEMBARRIER_CMD_SHARED, 0);
+#else
+#error --enable-membarrier is not supported on this operating system.
+#endif
+}
+
+void smp_mb_global_init(void)
+{
+#ifdef CONFIG_LINUX
+    int ret = membarrier(MEMBARRIER_CMD_QUERY, 0);
+    if (ret < 0) {
+        error_report("This QEMU binary requires the membarrier system call.");
+        error_report("Please upgrade your system to a newer version of Linux");
+        exit(1);
+    }
+    if (!(ret & MEMBARRIER_CMD_SHARED)) {
+        error_report("This QEMU binary requires MEMBARRIER_CMD_SHARED support.");
+        error_report("Please upgrade your system to a newer version of Linux");
+        exit(1);
+    }
+#endif
+}