exec: protect mru_block with RCU

Hence, freeing a RAMBlock has to be switched to call_rcu.

Reviewed-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
diff --git a/include/exec/cpu-all.h b/include/exec/cpu-all.h
index 2c48286..b8781d1 100644
--- a/include/exec/cpu-all.h
+++ b/include/exec/cpu-all.h
@@ -24,6 +24,7 @@
 #include "exec/memory.h"
 #include "qemu/thread.h"
 #include "qom/cpu.h"
+#include "qemu/rcu.h"
 
 /* some important defines:
  *
@@ -268,6 +269,7 @@
 typedef struct RAMBlock RAMBlock;
 
 struct RAMBlock {
+    struct rcu_head rcu;
     struct MemoryRegion *mr;
     uint8_t *host;
     ram_addr_t offset;