[PULL 7/9] physmem: add missing memory barrier

[Paolo Bonzini]

Reviewed-by: Richard Henderson <richard.hender...@linaro.org>
Reviewed-by: David Hildenbrand <da...@redhat.com>
Signed-off-by: Paolo Bonzini <pbonz...@redhat.com>
---
 softmmu/physmem.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/softmmu/physmem.c b/softmmu/physmem.c
index 47143edb4f6c..a6efd8e8dd11 100644
--- a/softmmu/physmem.c
+++ b/softmmu/physmem.c
@@ -2927,6 +2927,8 @@ void cpu_register_map_client(QEMUBH *bh)
     qemu_mutex_lock(&map_client_list_lock);
     client->bh = bh;
     QLIST_INSERT_HEAD(&map_client_list, client, link);
+    /* Write map_client_list before reading in_use.  */
+    smp_mb();
     if (!qatomic_read(&bounce.in_use)) {
         cpu_notify_map_clients_locked();
     }
@@ -3116,6 +3118,7 @@ void address_space_unmap(AddressSpace *as, void *buffer, 
hwaddr len,
     qemu_vfree(bounce.buffer);
     bounce.buffer = NULL;
     memory_region_unref(bounce.mr);
+    /* Clear in_use before reading map_client_list.  */
     qatomic_mb_set(&bounce.in_use, false);
     cpu_notify_map_clients();
 }
-- 
2.39.1