tci: Make direct jump patching thread-safe

Ensure direct jump patching in TCI is atomic by:
 * naturally aligning a location of direct jump address;
 * using atomic_read()/atomic_set() to load/store the address.

Signed-off-by: Sergey Fedorov <serge.fdrv@gmail.com>
Signed-off-by: Sergey Fedorov <sergey.fedorov@linaro.org>
Message-Id: <1461341333-19646-4-git-send-email-sergey.fedorov@linaro.org>
Signed-off-by: Richard Henderson <rth@twiddle.net>

1 files changed, 4 insertions, 1 deletions

diff --git a/tci.c b/tci.c
index 82705fe772..a8939e6d3c 100644
--- a/tci.c
+++ b/tci.c
@@ -1089,7 +1089,10 @@ uintptr_t tcg_qemu_tb_exec(CPUArchState *env, uint8_t *tb_ptr)
             goto exit;
             break;
         case INDEX_op_goto_tb:
-            t0 = tci_read_i32(&tb_ptr);
+            /* Jump address is aligned */
+            tb_ptr = QEMU_ALIGN_PTR_UP(tb_ptr, 4);
+            t0 = atomic_read((int32_t *)tb_ptr);
+            tb_ptr += sizeof(int32_t);
             tci_assert(tb_ptr == old_code_ptr + op_size);
             tb_ptr += (int32_t)t0;
             continue;