vfio_default_config_write
count = vfio_default_config_write(vdev, pos, count, perm, offset, val);
perm->writefn = vfio_default_config_write;
count = vfio_default_config_write(vdev, pos, count, perm, offset, val);
count = vfio_default_config_write(vdev, pos, count, perm, offset, val);
count = vfio_default_config_write(vdev, pos, count, perm, offset, val);
count = vfio_default_config_write(vdev, pos, count, perm, offset, val);
count = vfio_default_config_write(vdev, pos, count, perm, offset, val);