GHCI/MigTD - Current Migration TD does not support multiple TDs migration

[gaojiaqi7]

Tasks:

• Upgrade rustls
• Async rustls
• Non-blocking device read/write operations, i.e. implementing AsyncRead and AsyncWrite defined in futures-io for VsockStream and VirtioSerialPort
• Non-blocking TDVMCALL
• Async runtime

[gaojiaqi7]

After some investigation, I found that async/await is a good choice for the single threaded execution environment.

Rust does not provide an official implementation of Future runtime, so we need to realize an executor to run our asynchronous tasks. We also need to make some changes on the blocking functions such as TLS, vsock/serial and GHCI to support the async.

• Implements a future runtime which can support multiple tasks, timeout, external events and idle. We can take third-party crates as reference: https://github.com/embassy-rs/embassy.git
• Implements the async rustls (or use async-rustls crate if possible) and add async I/O methods in std-support crate. Reference: https://github.com/smol-rs/async-rustls.git
• Supports non-blocking sending and receiving in device drivers (vsock/serial/vmcall)
• Add Future implementation for GHCI interfaces such as wait_for_request.

[jyao1]

Please describe why we need embassy.

[gaojiaqi7]

Some async runtime projects from community:

Crate	no_std compatible	Complete runtime cycle	Usage and activity
tokio	No	Yes	21.5k stars, active in 1 day
async-std	No	Yes	3.7k stars, active in 3 months
smol	No	Yes	2.9k stars, active in 1 month
Executor	Yes	No	212 stars, active in 1 year
Embassy	Yes	No (Only for Arm and Riscv embedded, no x86 impl)	21.5k stars, active in 1 day
rust/future-rs	Partial (futures-executor and futures-io need std)	?	4.9k stars, active in 3 days

[gaojiaqi7]

Async rustls crates from community:

Async rustls crate	Async IO Crate	Community	Usage and activity
tokio-rustls	tokio::io	rustls	12 stars, 1 week
async-rustls	futures::io	smol-rs	32 stars, 1 week

[gaojiaqi7]

Async IO crates:

Async IO crate	std-dependency	Community	Usage and activity
tokio-io	Yes	tokio-rs	21.6k stars, 1 day
futures-io	Yes	rust-lang	4.9k stars, 1 week