Skip setting SPTEs if no change is expected.
Reviewed-by: Peter Feiner <pfeiner@google.com>
Signed-off-by: Ben Gardon <bgardon@google.com>

Message-Id: <20210202185734.1680553-16-bgardon@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>