accel/tcg: Move post-load tb_flush to vm_change_state hook

We need not call tb_flush once per cpu, only once per vmload.

By moving the call from cpu_common_post_load to a tcg-specific
vm_change_state_handler, we do even better than that: we only
flush when called from HMP triggered loadvm, when we had old
state to flush.

Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Pierrick Bouvier <pierrick.bouvier@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

accel/tcg/tcg-all.c

@@ -38,6 +38,8 @@
 #include "qemu/target-info.h"
 #ifndef CONFIG_USER_ONLY
 #include "hw/boards.h"
+#include "exec/tb-flush.h"
+#include "system/runstate.h"
 #endif
 #include "accel/accel-ops.h"
 #include "accel/accel-cpu-ops.h"
@@ -82,6 +84,23 @@ static void tcg_accel_instance_init(Object *obj)
 
 bool one_insn_per_tb;
 
+#ifndef CONFIG_USER_ONLY
+static void tcg_vm_change_state(void *opaque, bool running, RunState state)
+{
+    if (state == RUN_STATE_RESTORE_VM) {
+        /*
+         * loadvm will update the content of RAM, bypassing the usual
+         * mechanisms that ensure we flush TBs for writes to memory
+         * we've translated code from, so we must flush all TBs.
+         *
+         * vm_stop() has just stopped all cpus, so we are exclusive.
+         */
+        assert(!running);
+        tb_flush__exclusive_or_serial();
+    }
+}
+#endif
+
 static int tcg_init_machine(AccelState *as, MachineState *ms)
 {
     TCGState *s = TCG_STATE(as);
@@ -124,6 +143,8 @@ static int tcg_init_machine(AccelState *as, MachineState *ms)
     default:
         g_assert_not_reached();
     }
+
+    qemu_add_vm_change_state_handler(tcg_vm_change_state, NULL);
 #endif
 
     tcg_allowed = true;