[Qemu-devel] [PATCH 1/4] tcg: access cpu->icount_decr.u16.high with atomics

[Emilio G. Cota]

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.

Reviewed-by: Richard Henderson <address@hidden>
Signed-off-by: Emilio G. Cota <address@hidden>
---
 accel/tcg/tcg-all.c       | 2 +-
 accel/tcg/translate-all.c | 2 +-
 qom/cpu.c                 | 2 +-
 3 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/accel/tcg/tcg-all.c b/accel/tcg/tcg-all.c
index 56dbb56a16..3d25bdcc17 100644
--- a/accel/tcg/tcg-all.c
+++ b/accel/tcg/tcg-all.c
@@ -51,7 +51,7 @@ static void tcg_handle_interrupt(CPUState *cpu, int mask)
     if (!qemu_cpu_is_self(cpu)) {
         qemu_cpu_kick(cpu);
     } else {
-        cpu->icount_decr.u16.high = -1;
+        atomic_set(&cpu->icount_decr.u16.high, -1);
         if (use_icount &&
             !cpu->can_do_io
             && (mask & ~old_mask) != 0) {
diff --git a/accel/tcg/translate-all.c b/accel/tcg/translate-all.c
index ad5c758246..356dcd0948 100644
--- a/accel/tcg/translate-all.c
+++ b/accel/tcg/translate-all.c
@@ -2341,7 +2341,7 @@ void cpu_interrupt(CPUState *cpu, int mask)
 {
     g_assert(qemu_mutex_iothread_locked());
     cpu->interrupt_request |= mask;
-    cpu->icount_decr.u16.high = -1;
+    atomic_set(&cpu->icount_decr.u16.high, -1);
 }
 
 /*
diff --git a/qom/cpu.c b/qom/cpu.c
index 92599f3541..20ad54d43f 100644
--- a/qom/cpu.c
+++ b/qom/cpu.c
@@ -266,7 +266,7 @@ 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 = 1;
     cpu->exception_index = -1;
     cpu->crash_occurred = false;
-- 
2.17.1