Unifying physical and virtual address types across the rust OS development ecosystem.

[jounathaen]

Hi,

I think having the semantic differentiation between a PhysicalAddress and a VirtualAddress type provides a lot of value for OS development. What I think would be even better, is to have a [Physical|Virtual]Address type that is coherent across multiple crates AND across different architectures. This could simplify the reuse of code and the compatibility between projects.

Currently, the situation looks as follows:

• x86_64 has type definitions for this, but this can only be used on x86_64. These types are apparently widely used in rust-osdev projects (and I use them in our hypervisor as well).
• I have copycat-ed this into our aarch64 crate to have a compatible type for aarch64. However, riscv64 etc. is still not supported. (And that crate did really not receive the required love to be adopted elsewhere (yet)).
• rust-vmm has a similar approach with their Address Trait. They are using it for GuestAddress'es, which is a use-case for address types I have as well.
• In the Hermit OS, we are actually using the x86 PAddr and VAddr types for x86, the types from the aforementioned aarch64 crate for the ARM architecture and a custom type for RISC-V

So I was thinking of moving the addresses into a separate crate that is not x86_64 specific anymore. The types from that crate could be used and re-exported in the x86_64 crate without changing any interfaces. I guess it is possible to make it compatible with the x86 crate's types as well. And as I'm on it, I could also implement rust-vmm's traits and add a guest physical address type as well.

However, this only makes sense if there is interest in adopting this approach. Otherwise, we'll just end up with a XKCD927 situation. So, what are your thoughts?