In vtd_switch_address_space() we did the memory region switch, however
it's possible that the caller of it has not taken the BQL at all. Make
sure we have it.
CC: Paolo Bonzini <pbonzini@redhat.com> CC: Jason Wang <jasowang@redhat.com> CC: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Peter Xu <peterx@redhat.com> Reviewed-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>