RustInQemu

For the old RustInQemu page, see RustInQemu/2022

Active effort

• Current state
• Documentation
• Roadmap: November 2024 | January 2025

Past efforts

• [RFC v3 00/32] Rust binding for QAPI and qemu-ga QMP handler examples
  on patchew on lore

Minimum supported versions

Required versions:

• 1.59.0 has const CStr::from_bytes_with_nul_unchecked, not really possible to go below that. Of the supported distributions only Debian bullseye has an older version.
• 1.63.0 is available on Debian bookworm (though it also rustc-web, which is 1.70.0 on mips64el and 1.78.0 on all other platforms).
• 1.75.0 is available on Ubuntu 22.04 and 24.04. It can return "impl Trait" in traits. This is important when using the pinned_init crate in traits (e.g. to implement QOM instance_init).
• 1.83.0 will allow const_refs_statics and nested offset_of (useful to make vmstate type-safe).

Bindgen 0.60.x has --allowlist-file. Of the supported distributions only Ubuntu 22.04 has an older version (0.59.x).

Work in progress

Paolo

• To be merged: finish QOM, MemoryRegion
• Planned: errno, chardev
• Later: pinned_init
• Upstream Meson support for rustdoc and "objects:"

Manos

• Documentation

Kevin

• Executing async code
• Block driver implementations

Zhao

• hpet timer device
  • timer/gpio/memattrs bindings

TODO

Bugs

• Integration tests are linked with libqemuutil as link_whole, which does not work when modules are enabled
  • meson seems to be buggy and does not allow using link_with instead?
  • probably best to require meson 1.8.0 anyway as it has nicer integration with clippy, and possibly rustdoc
• Add BQL abstraction for tests - avoid running them with "--test-threads 1"
• Distros would prefer to link libstd dynamically; Rust-enabled QEMU binaries are huge

Nice things to have

• run doctests with meson test
• Remove need for manual "meson subprojects update --reset" when updating packagefiles/
• Improve tool integration
  • Run code checks a la "meson test --suite codecheck"? (clippy and rustfmt)
• rustfmt currently requires nightly, decide what to do about it
• Place rustdoc output for master somewhere?
• more QOM procedural macros
  • generate qdev properties?
  • generate parts of TypeInfo?
• distros need dynamically linked libstd (rewrite system/main.c in Rust, or do it in Meson?)

New code to write

• feature parity for pl011
• safe object creation with pinned_init, originating from Linux)
• Generic Rust<->C interop, Error (https://github.com/bonzini/rust-qemu)
• DMA (investigate vm-memory?)
• Trace/log

Ideas for lints without breaking CI

See https://github.com/bonzini/rust-qemu/commit/95b25f7c5f4e2694a85a5503050cc98da7562c7c

• run clippy as part of "make check", possibly only if Rust is newer than some version (1.74.0 so that clippy can be configured in Cargo.toml?)
• deny many individual lints, do not deny groups (complexity, perf, style, suspicious) on regular builds. allow unknown_lints.
• add to CI a fallible job that runs on nightly clippy with -Dclippy::complexity -Dclippy::perf -Dclippy::suspicious -Dclippy::style -Dunknown_lints. the job should generally pass, and if a new lint triggers it probably should be added to Cargo.toml as either "allow" (rare) or "deny" (possibly after adding #[allow()] to the source).

Possible project targets

Miscellanea

- qemu-bridge-helper.c Re-write SUID C executable with useful features.

Devices

• hw/block/pflash_cfi01.c, hw/block/pflash_cfi02.c (claimed, WIP)
  • needs block bindings
• hw/timer/hpet.c, hw/timer/i8254.c (claimed, WIP)
  • needs timer/memattrs/bitops/error/irq/trace bindgings
• hw/mem/nvdimm.c (suggested by Manos)