PolkaVM

PolkaVM is a general purpose user-level RISC-V based virtual machine.

This project is still unfinished and is a very heavy work-in-progress! Do not use it in production!

Design goals

(Note: not all of these are currently true!)

• Secure and sandboxed by default. The code running in the VM should run in a separate process, and should not be able to access the host system, even in the presence of an attacker with full remote code execution priviledges inside of the VM.
• Fast to execute. The runtime performance of the code running in the VM should be competetive with state-of-art WebAssembly VMs, at least within the same order of magnitude.
• Fast to compile, with guaranteed single-pass O(n) compilation. Loading new code into the VM should be near instanteneous.
• Low memory footprint. Each concurrent instance of the VM should have a baseline memory overhead of no more than 128KB.
• Small binaries. Programs compiled for this VM should take up as little space as possible.
• No wasted virtual address space. The VM should not preallocate gigabytes of virtual address space for sandboxing purposes.
• Fully deterministic. Given the same inputs and the same code the execution should always return exactly the same output.
• Support for high performance asynchronous gas metering. Gas metering should be cheap, deterministic, and reasonably accurate.
• Simple. It should be possible for a single programmer to write an interpreter fully compatible with this VM in less than a week.
• Versioned operational semantics. Any future changes to the semantics that are observable by a guest program will be versioned, and will be explicitly opt-in.
• Standarized. There should be a spec fully describing the guest-observable operational semantics of this VM.
• Cross-platform. On unsupported OSes and platforms the VM will run in an interpreted mode.
• Minimum external dependencies. The VM should be mostly self-contained, fast to compile, and resistant to supply-chain attacks.
• Built-in tooling for debugging and performance profiling.

Non-goals

• System level emulation. This VM will never be able to run a normal operating system.
• Full support for architectures other than amd64 (also known as x86_64) and aarch64 (also known as arm64). Anything else will run in an interpreted mode.
• Full support for operating systems other than Linux, macOS and Windows. On any other OS the VM will run in an interpreted mode.
• Floating point support, SIMD, and other more niche RISC-V extensions. These could be added as an opt-in feature in the future if necessary, but this is not currently planned.
• Support for full 32-register RISC-V ISA. This VM currently only targets the RV32EM.

License

Licensed under either of

• Apache License, Version 2.0, (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
• MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT)

at your option.

Contribution

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.