Re: [PATCH v2 00/16] rust: QObject and QAPI bindings

Paolo Bonzini
2026-02-17T08:11:06Z

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It's been more than a month... Looking for reviews of the qapi-gen changes,
especially the non-Rust-specific parts.

Paolo

Il gio 8 gen 2026, 14:10 Paolo Bonzini <pbonzini@redhat.com> ha scritto:

> This adds two related parts of the Rust bindings:
>
> - QAPI code generator that creates Rust structs from the JSON
> description. The structs are *not* ABI compatible with the
> C ones, instead they use native Rust data types.
>
> - QObject bindings and (de)serialization support, which can be used to
> convert QObjects to and from QAPI structs.
>
> Unfortunately Rust code is not able to use visitors, other than by
> creating an intermediate QObject. This is because of the different
> architecture of serde vs. QAPI visitors, and because visitor's
> dual-purpose functions, where the same function is used by both input and
> output visitors, rely heavily on the structs using the same representation
> as the visitor arguments (for example NUL-terminated strings).
>
> The serde format implementation was co-authored by me and Marc-André.
> Marc-André did all the bug fixing and integration testing.
>
> As an example of how this would be used, the marshaling functions for
> QMP commands would look like this:
>
> fn qmp_marshal_query_stats(args: *mut QDict,
> retp: *mut *mut QObject, errp: *mut *mut Error)
> {
> let qobj = unsafe { QObject::cloned_from_raw(args.cast()) };
>
> let result = from_qobject::<StatsFilter>(qobj)
> .map_err(anyhow::Error::from)
> .and_then(qmp_query_stats)
> .and_then(|ret|
> to_qobject::<Vec<StatsResult>>(ret).map_err(anyhow::Error::from));
>
> match qmp_marshal_query_stats_rs(qobj) {
> Ok(ret) => unsafe { *retp = ret.into_raw(); },
> Err(e) => unsafe { crate::Error::from(e).propagate(errp) },
> }
> }
>
> Despite the long v1->v2, the changes are mostly cosmetic; there are a few
> small differences in the detection of types to be wrapped with Box<>,
> because Vec<> is now considered to break cycles.
>
> Available at branch rust-next of https://gitlab.com/bonzini/qemu (which
> is now almost empty other than this series, yay).
>
> Paolo
>
> v1->v2, Rust:
> - adjust comments in C code (include/qobject/qobject.h)
> - improve or fix documentation in rust/util/src/qobject/mod.rs
> - introduce a qobject! macro that is equivalent to QOBJECT()
> - remark when functions are converted from C inlines
> - rename from_int/from_uint/from_double macros
> - fix incorrect "native: true" on serde and serde_core overrides
> - rebase
>
> qapi-gen:
> - rewrite QAPISchemaIfCond.rsgen() to avoid messy typing
> - new patches 10-11 to extend existing qapigen code
> - rewritten rs_type() to avoid going through a C type first
> - removed renaming of QAPICBackend
> - reused C functions for case conversions
> - clean up rs_name, move it to common.py (needed for rs_type() changes)
> - Vec<> can break cycles and avoid boxing of structs
> - restrict squashing of consecutive newlines to Rust code
> - add copyright blurb
> - annotate that using a separate qapi-gen backend is temporary
> - drop #[derive(common::TryInto)] from enums
>
> Marc-André Lureau (7):
> rust/qobject: add Display/Debug
> scripts/qapi: add QAPISchemaIfCond.rsgen()
> scripts/qapi: generate high-level Rust bindings
> scripts/rustc_args: add --no-strict-cfg
> rust/util: build QAPI types
> scripts/qapi: add serde attributes
> rust/tests: QAPI integration tests
>
> Paolo Bonzini (9):
> rust/qobject: add basic bindings
> subprojects: add serde
> rust/qobject: add Serialize implementation
> rust/qobject: add Serializer (to_qobject) implementation
> rust/qobject: add Deserialize implementation
> rust/qobject: add Deserializer (from_qobject) implementation
> rust/qobject: add from/to JSON bindings for QObject
> scripts/qapi: add QAPISchemaType.is_predefined
> scripts/qapi: pull c_name from camel_to_upper to caller
>
> docs/devel/rust.rst | 1 +
> meson.build | 4 +-
> include/qobject/qobject.h | 5 +-
> rust/util/wrapper.h | 8 +
> qapi/meson.build | 9 +
> rust/Cargo.lock | 2 +
> rust/Cargo.toml | 2 +
> rust/meson.build | 4 +
> rust/tests/meson.build | 21 +-
> rust/tests/tests/integration.rs | 2 +
> rust/tests/tests/qapi.rs | 444 +++++++++++++
> rust/util/Cargo.toml | 2 +
> rust/util/meson.build | 30 +-
> rust/util/src/lib.rs | 4 +
> rust/util/src/qobject/deserialize.rs | 134 ++++
> rust/util/src/qobject/deserializer.rs | 371 +++++++++++
> rust/util/src/qobject/error.rs | 58 ++
> rust/util/src/qobject/mod.rs | 383 ++++++++++++
> rust/util/src/qobject/serialize.rs | 59 ++
> rust/util/src/qobject/serializer.rs | 585 ++++++++++++++++++
> scripts/archive-source.sh | 3 +
> scripts/make-release | 2 +-
> scripts/qapi/backend.py | 25 +
> scripts/qapi/common.py | 66 +-
> scripts/qapi/rs.py | 61 ++
> scripts/qapi/rs_types.py | 394 ++++++++++++
> scripts/qapi/schema.py | 74 ++-
> scripts/rust/rustc_args.py | 16 +-
> subprojects/.gitignore | 3 +
> .../packagefiles/serde-1-rs/meson.build | 36 ++
> .../packagefiles/serde-1.0.226-include.patch | 16 +
> .../packagefiles/serde_core-1-rs/meson.build | 25 +
> .../serde_core-1.0.226-include.patch | 15 +
> .../serde_derive-1-rs/meson.build | 35 ++
> .../serde_derive-1.0.226-include.patch | 11 +
> subprojects/serde-1-rs.wrap | 11 +
> subprojects/serde_core-1-rs.wrap | 11 +
> subprojects/serde_derive-1-rs.wrap | 11 +
> 38 files changed, 2910 insertions(+), 33 deletions(-)
> create mode 100644 rust/tests/tests/integration.rs
> create mode 100644 rust/tests/tests/qapi.rs
> create mode 100644 rust/util/src/qobject/deserialize.rs
> create mode 100644 rust/util/src/qobject/deserializer.rs
> create mode 100644 rust/util/src/qobject/error.rs
> create mode 100644 rust/util/src/qobject/mod.rs
> create mode 100644 rust/util/src/qobject/serialize.rs
> create mode 100644 rust/util/src/qobject/serializer.rs
> create mode 100644 scripts/qapi/rs.py
> create mode 100644 scripts/qapi/rs_types.py
> create mode 100644 subprojects/packagefiles/serde-1-rs/meson.build
> create mode 100644 subprojects/packagefiles/serde-1.0.226-include.patch
> create mode 100644 subprojects/packagefiles/serde_core-1-rs/meson.build
> create mode 100644
> subprojects/packagefiles/serde_core-1.0.226-include.patch
> create mode 100644 subprojects/packagefiles/serde_derive-1-rs/meson.build
> create mode 100644
> subprojects/packagefiles/serde_derive-1.0.226-include.patch
> create mode 100644 subprojects/serde-1-rs.wrap
> create mode 100644 subprojects/serde_core-1-rs.wrap
> create mode 100644 subprojects/serde_derive-1-rs.wrap
>
> --
> 2.52.0
>

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