icount: clean up cpu_can_io at the entry to the block

Most of IO instructions can be executed only at the end of the block in
icount mode. Therefore translator can set cpu_can_io flag when translating
the last instruction.
But when the blocks are chained, then this flag is not reset and may
remain set at the beginning of the next block.
This patch resets the flag at the entry of any translation block,
making I/O operations impossible by default.

Signed-off-by: Pavel Dovgalyuk <Pavel.Dovgaluk@ispras.ru>
--

v2 changes:
 - reset can_do_io at the start of every TB (suggested by Paolo Bonzini)
Message-Id: <156404428943.18669.15747009371169578935.stgit@pasha-Precision-3630-Tower>

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/accel/tcg/cpu-exec.c b/accel/tcg/cpu-exec.c
index 6c85c3ee1e98096fc477b4527405faf36267033a..48272c781b7e66addbabac3c480de07b45d4e2ff 100644 (file)
--- a/accel/tcg/cpu-exec.c
+++ b/accel/tcg/cpu-exec.c
@@ -169,7 +169,6 @@ static inline tcg_target_ulong cpu_tb_exec(CPUState *cpu, TranslationBlock *itb)
     }
 #endif /* DEBUG_DISAS */
 
-    cpu->can_do_io = !use_icount;
     ret = tcg_qemu_tb_exec(env, tb_ptr);
     cpu->can_do_io = 1;
     last_tb = (TranslationBlock *)(ret & ~TB_EXIT_MASK);

diff --git a/include/exec/gen-icount.h b/include/exec/gen-icount.h
index f7669b684147ccbf83efc43f96231ad4bf93bd9e..4004e6c9d0e179175a578b70b50261ae97e1415a 100644 (file)
--- a/include/exec/gen-icount.h
+++ b/include/exec/gen-icount.h
@@ -7,6 +7,24 @@
 
 static TCGOp *icount_start_insn;
 
+static inline void gen_io_start(void)
+{
+    TCGv_i32 tmp = tcg_const_i32(1);
+    tcg_gen_st_i32(tmp, cpu_env,
+                   offsetof(ArchCPU, parent_obj.can_do_io) -
+                   offsetof(ArchCPU, env));
+    tcg_temp_free_i32(tmp);
+}
+
+static inline void gen_io_end(void)
+{
+    TCGv_i32 tmp = tcg_const_i32(0);
+    tcg_gen_st_i32(tmp, cpu_env,
+                   offsetof(ArchCPU, parent_obj.can_do_io) -
+                   offsetof(ArchCPU, env));
+    tcg_temp_free_i32(tmp);
+}
+
 static inline void gen_tb_start(TranslationBlock *tb)
 {
     TCGv_i32 count, imm;
@@ -40,6 +58,8 @@ 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();
     }
 
     tcg_temp_free_i32(count);
@@ -57,22 +77,4 @@ static inline void gen_tb_end(TranslationBlock *tb, int num_insns)
     tcg_gen_exit_tb(tb, TB_EXIT_REQUESTED);
 }
 
-static inline void gen_io_start(void)
-{
-    TCGv_i32 tmp = tcg_const_i32(1);
-    tcg_gen_st_i32(tmp, cpu_env,
-                   offsetof(ArchCPU, parent_obj.can_do_io) -
-                   offsetof(ArchCPU, env));
-    tcg_temp_free_i32(tmp);
-}
-
-static inline void gen_io_end(void)
-{
-    TCGv_i32 tmp = tcg_const_i32(0);
-    tcg_gen_st_i32(tmp, cpu_env,
-                   offsetof(ArchCPU, parent_obj.can_do_io) -
-                   offsetof(ArchCPU, env));
-    tcg_temp_free_i32(tmp);
-}
-
 #endif