stdvga+bochs-display: add dummy mmio handler
The bochs-display mmio bar has some sub-regions with the actual hardware
registers. What happens when the guest access something outside those
regions depends on the archirecture. On x86 those reads succeed (and
return 0xff I think). On risc-v qemu aborts.
This patch adds handlers for the parent region, to make the wanted
behavior explicit and to make things consistent across architectures.
v2:
- use existing unassigned_io_ops.
- also cover stdvga.
Cc: Alistair Francis <alistair23@gmail.com>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Message-id:
20200309100009.17624-1-kraxel@redhat.com