明确地址空间设计

[longfangsong]

Feature Request

Is your feature request related to a problem? Please describe:

Also /cc #23，目前我们地址空间怎么定纯粹是拍脑袋的，这好嘛，这不好。

Describe the feature you'd like:

明确划定一个地址空间，什么硬件映射到什么地址。

Describe alternatives you've considered:

直接抄一些现成实现的地址空间。

Teachability, Documentation, Adoption, Migration Strategy:

TBA