memory: Provide separate handling of unassigned io ports accesses

Accesses to unassigned io ports shall return -1 on read and be ignored
on write. Ensure these properties via dedicated ops, decoupling us from
the memory core's handling of unassigned accesses.

Cc: qemu-stable@nongnu.org
Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 2 insertions, 1 deletions

diff --git a/exec.c b/exec.c
index e6f04d8..3859b02 100644
--- a/exec.c
+++ b/exec.c
@@ -1805,7 +1805,8 @@ static void memory_map_init(void)
     address_space_init(&address_space_memory, system_memory, "memory");
 
     system_io = g_malloc(sizeof(*system_io));
-    memory_region_init(system_io, NULL, "io", 65536);
+    memory_region_init_io(system_io, NULL, &unassigned_io_ops, NULL, "io",
+                          65536);
     address_space_init(&address_space_io, system_io, "I/O");
 
     memory_listener_register(&core_memory_listener, &address_space_memory);