From 9ce38c20b9e2449f7d5b7e5dacafe8482e2aa35c Mon Sep 17 00:00:00 2001
From: "Emilio G. Cota" <cota@braap.org>
Date: Tue, 23 Oct 2018 14:36:36 -0400
Subject: [PATCH] tcg: access cpu->icount_decr.u16.high with atomics

Consistently access u16.high with atomics to avoid
undefined behaviour in MTTCG.

Note that icount_decr.u16.low is only used in icount mode,
so regular accesses to it are OK.

Backports part of commit fff42f183ea4c3967405d4c1dce6d97dae4d64c8 from
qemu
---
 qemu/qom/cpu.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/qemu/qom/cpu.c b/qemu/qom/cpu.c
index b79fd8a0..307b9254 100644
--- a/qemu/qom/cpu.c
+++ b/qemu/qom/cpu.c
@@ -145,7 +145,7 @@ static void cpu_common_reset(CPUState *cpu)
     cpu->mem_io_pc = 0;
     cpu->mem_io_vaddr = 0;
     cpu->icount_extra = 0;
-    cpu->icount_decr.u32 = 0;
+    atomic_set(&cpu->icount_decr.u32, 0);
     cpu->can_do_io = 0;
     cpu->exception_index = -1;
     cpu->crash_occurred = false;