How to enable dm-verity on Android 8

[cn-xueliang_bao]

I have made Android 8.0.0 Oreo (O8.0.0_1.0.0, 4.9 kernel) run well on I.MX6DL.

But by default, A/B system and dm-verity is disabled.

Are there any patches to enable dm-verity?

Are there any patches to enable A/B system?

Thanks.