1 files changed, 7 insertions, 1 deletions
diff --git a/include/exec/gen-icount.h b/include/exec/gen-icount.h
index 4004e6c9d0..822c43cfd3 100644
--- a/include/exec/gen-icount.h
+++ b/include/exec/gen-icount.h
@@ -16,6 +16,13 @@ static inline void gen_io_start(void)
     tcg_temp_free_i32(tmp);
 }
 
+/*
+ * cpu->can_do_io is cleared automatically at the beginning of
+ * each translation block.  The cost is minimal and only paid
+ * for -icount, plus it would be very easy to forget doing it
+ * in the translator.  Therefore, backends only need to call
+ * gen_io_start.
+ */
 static inline void gen_io_end(void)
 {
     TCGv_i32 tmp = tcg_const_i32(0);
@@ -58,7 +65,6 @@ static inline void gen_tb_start(TranslationBlock *tb)
         tcg_gen_st16_i32(count, cpu_env,
                          offsetof(ArchCPU, neg.icount_decr.u16.low) -
                          offsetof(ArchCPU, env));
-        /* Disable I/O by default */
         gen_io_end();
     }