Introduce proper compiler barrier
Define barrier() as optimization barrier and replace (potentially
unreliable) asm("") fences.
Signed-off-by: Jan Kiszka <[email protected]>
Acked-by: Paolo Bonzini <[email protected]>
Reviewed-by: Marcelo Tosatti <[email protected]>
Signed-off-by: Aurelien Jarno <[email protected]>
diff --git a/cpu-exec.c b/cpu-exec.c
index 026980a..525b3b4 100644
--- a/cpu-exec.c
+++ b/cpu-exec.c
@@ -21,6 +21,7 @@
#include "disas.h"
#include "tcg.h"
#include "kvm.h"
+#include "qemu-barrier.h"
#if !defined(CONFIG_SOFTMMU)
#undef EAX
@@ -233,7 +234,7 @@
use it. */
QEMU_BUILD_BUG_ON (sizeof (saved_env_reg) != sizeof (env));
saved_env_reg = (host_reg_t) env;
- asm("");
+ barrier();
env = env1;
if (exit_request) {
@@ -669,7 +670,7 @@
#endif
/* restore global registers */
- asm("");
+ barrier();
env = (void *) saved_env_reg;
/* fail safe : never use cpu_single_env outside cpu_exec() */
diff --git a/qemu-barrier.h b/qemu-barrier.h
index 3bd1075..b77fce2 100644
--- a/qemu-barrier.h
+++ b/qemu-barrier.h
@@ -4,4 +4,7 @@
/* FIXME: arch dependant, x86 version */
#define smp_wmb() asm volatile("" ::: "memory")
+/* Compiler barrier */
+#define barrier() asm volatile("" ::: "memory")
+
#endif
