Merge tag 'for-upstream' of https://gitlab.com/bonzini/qemu into staging

* qdev: second part of Property cleanups
* rust: second part of QOM rework
* rust: callbacks wrapper
* rust: pl011 bugfixes
* kvm: cleanup errors in kvm_convert_memory()

 # -----BEGIN PGP SIGNATURE-----
 #
 # iQFIBAABCAAyFiEE8TM4V0tmI4mGbHaCv/vSX3jHroMFAmdkaEkUHHBib256aW5p
 # QHJlZGhhdC5jb20ACgkQv/vSX3jHroN0/wgAgIJg8BrlRKfmiz14NZfph8/jarSj
 # TOWYVxL2v4q98KBuL5pta2ucObgzwqyqSyc02S2DGSOIMQCIiBB5MaCk1iMjx+BO
 # pmVU8gNlD8faO8SSmnnr+jDQt+G+bQ/nRgQJOAReF8oVw3O2aC/FaVKpitMzWtvv
 # PLnJWdrqqpGq14OzX8iNCzSujxppAuyjrhT4lNlekzDoDfdTez72r+rXkvg4GzZL
 # QC3xLYg/LrT8Rs+zgOhm/AaIyS4bOyMlkU9Du1rQ6Tyne45ey2FCwKVzBKrJdGcw
 # sVbzEclxseLenoTbZqYK6JTzLdDoThVUbY2JwoCGUaIm+74P4NjEsUsTVg==
 # =TuQM
 # -----END PGP SIGNATURE-----
 # gpg: Signature made Thu 19 Dec 2024 13:39:05 EST
 # gpg:                using RSA key F13338574B662389866C7682BFFBD25F78C7AE83
 # gpg:                issuer "pbonzini@redhat.com"
 # gpg: Good signature from "Paolo Bonzini <bonzini@gnu.org>" [full]
 # gpg:                 aka "Paolo Bonzini <pbonzini@redhat.com>" [full]
 # Primary key fingerprint: 46F5 9FBD 57D6 12E7 BFD4  E2F7 7E15 100C CD36 69B1
 #      Subkey fingerprint: F133 3857 4B66 2389 866C  7682 BFFB D25F 78C7 AE83

* tag 'for-upstream' of https://gitlab.com/bonzini/qemu: (42 commits)
  rust: pl011: simplify handling of the FIFO enabled bit in LCR
  rust: pl011: fix migration stream
  rust: pl011: extend registers to 32 bits
  rust: pl011: fix break errors and definition of Data struct
  rust: pl011: always use reset() method on registers
  rust: pl011: match break logic of C version
  rust: pl011: fix declaration of LineControl bits
  target/i386: Reset TSCs of parked vCPUs too on VM reset
  kvm: consistently return 0/-errno from kvm_convert_memory
  rust: qemu-api: add a module to wrap functions and zero-sized closures
  rust: qom: add initial subset of methods on Object
  rust: qom: add casting functionality
  rust: tests: allow writing more than one test
  bql: add a "mock" BQL for Rust unit tests
  rust: re-export C types from qemu-api submodules
  rust: rename qemu-api modules to follow C code a bit more
  rust: qom: add possibility of overriding unparent
  rust: qom: put class_init together from multiple ClassInitImpl<>
  Constify all opaque Property pointers
  hw/core/qdev-properties: Constify Property argument to PropertyInfo.print
  ...

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

10 files changed, 861 insertions, 238 deletions

diff --git a/rust/qemu-api/src/callbacks.rs b/rust/qemu-api/src/callbacks.rs
new file mode 100644
index 0000000..314f9dc
--- /dev/null
+++ b/rust/qemu-api/src/callbacks.rs
@@ -0,0 +1,144 @@
+// SPDX-License-Identifier: MIT
+
+//! Utility functions to deal with callbacks from C to Rust.
+
+use std::{mem, ptr::NonNull};
+
+/// Trait for functions (types implementing [`Fn`]) that can be used as
+/// callbacks. These include both zero-capture closures and function pointers.
+///
+/// In Rust, calling a function through the `Fn` trait normally requires a
+/// `self` parameter, even though for zero-sized functions (including function
+/// pointers) the type itself contains all necessary information to call the
+/// function. This trait provides a `call` function that doesn't require `self`,
+/// allowing zero-sized functions to be called using only their type.
+///
+/// This enables zero-sized functions to be passed entirely through generic
+/// parameters and resolved at compile-time. A typical use is a function
+/// receiving an unused parameter of generic type `F` and calling it via
+/// `F::call` or passing it to another function via `func::<F>`.
+///
+/// QEMU uses this trick to create wrappers to C callbacks.  The wrappers
+/// are needed to convert an opaque `*mut c_void` into a Rust reference,
+/// but they only have a single opaque that they can use.  The `FnCall`
+/// trait makes it possible to use that opaque for `self` or any other
+/// reference:
+///
+/// ```ignore
+/// // The compiler creates a new `rust_bh_cb` wrapper for each function
+/// // passed to `qemu_bh_schedule_oneshot` below.
+/// unsafe extern "C" fn rust_bh_cb<T, F: for<'a> FnCall<(&'a T,)>>(
+///     opaque: *mut c_void,
+/// ) {
+///     // SAFETY: the opaque was passed as a reference to `T`.
+///     F::call((unsafe { &*(opaque.cast::<T>()) }, ))
+/// }
+///
+/// // The `_f` parameter is unused but it helps the compiler build the appropriate `F`.
+/// // Using a reference allows usage in const context.
+/// fn qemu_bh_schedule_oneshot<T, F: for<'a> FnCall<(&'a T,)>>(_f: &F, opaque: &T) {
+///     let cb: unsafe extern "C" fn(*mut c_void) = rust_bh_cb::<T, F>;
+///     unsafe {
+///         bindings::qemu_bh_schedule_oneshot(cb, opaque as *const T as *const c_void as *mut c_void)
+///     }
+/// }
+/// ```
+///
+/// Each wrapper is a separate instance of `rust_bh_cb` and is therefore
+/// compiled to a separate function ("monomorphization").  If you wanted
+/// to pass `self` as the opaque value, the generic parameters would be
+/// `rust_bh_cb::<Self, F>`.
+///
+/// `Args` is a tuple type whose types are the arguments of the function,
+/// while `R` is the returned type.
+///
+/// # Examples
+///
+/// ```
+/// # use qemu_api::callbacks::FnCall;
+/// fn call_it<F: for<'a> FnCall<(&'a str,), String>>(_f: &F, s: &str) -> String {
+///     F::call((s,))
+/// }
+///
+/// let s: String = call_it(&str::to_owned, "hello world");
+/// assert_eq!(s, "hello world");
+/// ```
+///
+/// Note that the compiler will produce a different version of `call_it` for
+/// each function that is passed to it.  Therefore the argument is not really
+/// used, except to decide what is `F` and what `F::call` does.
+///
+/// Attempting to pass a non-zero-sized closure causes a compile-time failure:
+///
+/// ```compile_fail
+/// # use qemu_api::callbacks::FnCall;
+/// # fn call_it<'a, F: FnCall<(&'a str,), String>>(_f: &F, s: &'a str) -> String {
+/// #     F::call((s,))
+/// # }
+/// let x: &'static str = "goodbye world";
+/// call_it(&move |_| String::from(x), "hello workd");
+/// ```
+///
+/// # Safety
+///
+/// Because `Self` is a zero-sized type, all instances of the type are
+/// equivalent. However, in addition to this, `Self` must have no invariants
+/// that could be violated by creating a reference to it.
+///
+/// This is always true for zero-capture closures and function pointers, as long
+/// as the code is able to name the function in the first place.
+pub unsafe trait FnCall<Args, R = ()>: 'static + Sync + Sized {
+    /// Referring to this internal constant asserts that the `Self` type is
+    /// zero-sized.  Can be replaced by an inline const expression in
+    /// Rust 1.79.0+.
+    const ASSERT_ZERO_SIZED: () = { assert!(mem::size_of::<Self>() == 0) };
+
+    /// Call the function with the arguments in args.
+    fn call(a: Args) -> R;
+}
+
+macro_rules! impl_call {
+    ($($args:ident,)* ) => (
+        // SAFETY: because each function is treated as a separate type,
+        // accessing `FnCall` is only possible in code that would be
+        // allowed to call the function.
+        unsafe impl<F, $($args,)* R> FnCall<($($args,)*), R> for F
+        where
+            F: 'static + Sync + Sized + Fn($($args, )*) -> R,
+        {
+            #[inline(always)]
+            fn call(a: ($($args,)*)) -> R {
+                let _: () = Self::ASSERT_ZERO_SIZED;
+
+                // SAFETY: the safety of this method is the condition for implementing
+                // `FnCall`.  As to the `NonNull` idiom to create a zero-sized type,
+                // see https://github.com/rust-lang/libs-team/issues/292.
+                let f: &'static F = unsafe { &*NonNull::<Self>::dangling().as_ptr() };
+                let ($($args,)*) = a;
+                f($($args,)*)
+            }
+        }
+    )
+}
+
+impl_call!(_1, _2, _3, _4, _5,);
+impl_call!(_1, _2, _3, _4,);
+impl_call!(_1, _2, _3,);
+impl_call!(_1, _2,);
+impl_call!(_1,);
+impl_call!();
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    // The `_f` parameter is unused but it helps the compiler infer `F`.
+    fn do_test_call<'a, F: FnCall<(&'a str,), String>>(_f: &F) -> String {
+        F::call(("hello world",))
+    }
+
+    #[test]
+    fn test_call() {
+        assert_eq!(do_test_call(&str::to_owned), "hello world")
+    }
+}
diff --git a/rust/qemu-api/src/cell.rs b/rust/qemu-api/src/cell.rs
index 28349de..eae4e2c 100644
--- a/rust/qemu-api/src/cell.rs
+++ b/rust/qemu-api/src/cell.rs
@@ -124,9 +124,18 @@ use std::{
 
 use crate::bindings;
 
-// TODO: When building doctests do not include the actual BQL, because cargo
-// does not know how to link them to libqemuutil.  This can be fixed by
-// running rustdoc from "meson test" instead of relying on cargo.
+/// An internal function that is used by doctests.
+pub fn bql_start_test() {
+    if cfg!(MESON) {
+        // SAFETY: integration tests are run with --test-threads=1, while
+        // unit tests and doctests are not multithreaded and do not have
+        // any BQL-protected data.  Just set bql_locked to true.
+        unsafe {
+            bindings::rust_bql_mock_lock();
+        }
+    }
+}
+
 pub fn bql_locked() -> bool {
     // SAFETY: the function does nothing but return a thread-local bool
     !cfg!(MESON) || unsafe { bindings::bql_locked() }
@@ -220,6 +229,7 @@ impl<T> BqlCell<T> {
     ///
     /// ```
     /// use qemu_api::cell::BqlCell;
+    /// # qemu_api::cell::bql_start_test();
     ///
     /// let c = BqlCell::new(5);
     /// ```
@@ -236,6 +246,7 @@ impl<T> BqlCell<T> {
     ///
     /// ```
     /// use qemu_api::cell::BqlCell;
+    /// # qemu_api::cell::bql_start_test();
     ///
     /// let c = BqlCell::new(5);
     ///
@@ -253,6 +264,7 @@ impl<T> BqlCell<T> {
     ///
     /// ```
     /// use qemu_api::cell::BqlCell;
+    /// # qemu_api::cell::bql_start_test();
     ///
     /// let cell = BqlCell::new(5);
     /// assert_eq!(cell.get(), 5);
@@ -274,6 +286,7 @@ impl<T> BqlCell<T> {
     ///
     /// ```
     /// use qemu_api::cell::BqlCell;
+    /// # qemu_api::cell::bql_start_test();
     ///
     /// let c = BqlCell::new(5);
     /// let five = c.into_inner();
@@ -293,6 +306,7 @@ impl<T: Copy> BqlCell<T> {
     ///
     /// ```
     /// use qemu_api::cell::BqlCell;
+    /// # qemu_api::cell::bql_start_test();
     ///
     /// let c = BqlCell::new(5);
     ///
@@ -315,6 +329,7 @@ impl<T> BqlCell<T> {
     ///
     /// ```
     /// use qemu_api::cell::BqlCell;
+    /// # qemu_api::cell::bql_start_test();
     ///
     /// let c = BqlCell::new(5);
     ///
@@ -333,6 +348,7 @@ impl<T: Default> BqlCell<T> {
     ///
     /// ```
     /// use qemu_api::cell::BqlCell;
+    /// # qemu_api::cell::bql_start_test();
     ///
     /// let c = BqlCell::new(5);
     /// let five = c.take();
@@ -461,6 +477,7 @@ impl<T> BqlRefCell<T> {
     ///
     /// ```
     /// use qemu_api::cell::BqlRefCell;
+    /// # qemu_api::cell::bql_start_test();
     ///
     /// let c = BqlRefCell::new(5);
     ///
@@ -472,6 +489,7 @@ impl<T> BqlRefCell<T> {
     ///
     /// ```should_panic
     /// use qemu_api::cell::BqlRefCell;
+    /// # qemu_api::cell::bql_start_test();
     ///
     /// let c = BqlRefCell::new(5);
     ///
@@ -513,6 +531,7 @@ impl<T> BqlRefCell<T> {
     ///
     /// ```
     /// use qemu_api::cell::BqlRefCell;
+    /// # qemu_api::cell::bql_start_test();
     ///
     /// let c = BqlRefCell::new("hello".to_owned());
     ///
@@ -525,6 +544,7 @@ impl<T> BqlRefCell<T> {
     ///
     /// ```should_panic
     /// use qemu_api::cell::BqlRefCell;
+    /// # qemu_api::cell::bql_start_test();
     ///
     /// let c = BqlRefCell::new(5);
     /// let m = c.borrow();
diff --git a/rust/qemu-api/src/definitions.rs b/rust/qemu-api/src/definitions.rs
deleted file mode 100644
index df91a2e..0000000
--- a/rust/qemu-api/src/definitions.rs
+++ /dev/null
@@ -1,168 +0,0 @@
-// Copyright 2024, Linaro Limited
-// Author(s): Manos Pitsidianakis <manos.pitsidianakis@linaro.org>
-// SPDX-License-Identifier: GPL-2.0-or-later
-
-//! Definitions required by QEMU when registering a device.
-
-use std::{ffi::CStr, os::raw::c_void};
-
-use crate::bindings::{Object, ObjectClass, TypeInfo};
-
-unsafe extern "C" fn rust_instance_init<T: ObjectImpl>(obj: *mut Object) {
-    // SAFETY: obj is an instance of T, since rust_instance_init<T>
-    // is called from QOM core as the instance_init function
-    // for class T
-    unsafe { T::INSTANCE_INIT.unwrap()(&mut *obj.cast::<T>()) }
-}
-
-unsafe extern "C" fn rust_instance_post_init<T: ObjectImpl>(obj: *mut Object) {
-    // SAFETY: obj is an instance of T, since rust_instance_post_init<T>
-    // is called from QOM core as the instance_post_init function
-    // for class T
-    //
-    // FIXME: it's not really guaranteed that there are no backpointers to
-    // obj; it's quite possible that they have been created by instance_init().
-    // The receiver should be &self, not &mut self.
-    T::INSTANCE_POST_INIT.unwrap()(unsafe { &mut *obj.cast::<T>() })
-}
-
-/// Trait exposed by all structs corresponding to QOM objects.
-///
-/// # Safety
-///
-/// For classes declared in C:
-///
-/// - `Class` and `TYPE` must match the data in the `TypeInfo`;
-///
-/// - the first field of the struct must be of the instance type corresponding
-///   to the superclass, as declared in the `TypeInfo`
-///
-/// - likewise, the first field of the `Class` struct must be of the class type
-///   corresponding to the superclass
-///
-/// For classes declared in Rust and implementing [`ObjectImpl`]:
-///
-/// - the struct must be `#[repr(C)]`;
-///
-/// - the first field of the struct must be of the instance struct corresponding
-///   to the superclass, which is `ObjectImpl::ParentType`
-///
-/// - likewise, the first field of the `Class` must be of the class struct
-///   corresponding to the superclass, which is `ObjectImpl::ParentType::Class`.
-pub unsafe trait ObjectType: Sized {
-    /// The QOM class object corresponding to this struct.  Not used yet.
-    type Class;
-
-    /// The name of the type, which can be passed to `object_new()` to
-    /// generate an instance of this type.
-    const TYPE_NAME: &'static CStr;
-}
-
-/// Trait a type must implement to be registered with QEMU.
-pub trait ObjectImpl: ObjectType + ClassInitImpl {
-    /// The parent of the type.  This should match the first field of
-    /// the struct that implements `ObjectImpl`:
-    type ParentType: ObjectType;
-
-    /// Whether the object can be instantiated
-    const ABSTRACT: bool = false;
-    const INSTANCE_FINALIZE: Option<unsafe extern "C" fn(obj: *mut Object)> = None;
-
-    /// Function that is called to initialize an object.  The parent class will
-    /// have already been initialized so the type is only responsible for
-    /// initializing its own members.
-    ///
-    /// FIXME: The argument is not really a valid reference. `&mut
-    /// MaybeUninit<Self>` would be a better description.
-    const INSTANCE_INIT: Option<unsafe fn(&mut Self)> = None;
-
-    /// Function that is called to finish initialization of an object, once
-    /// `INSTANCE_INIT` functions have been called.
-    const INSTANCE_POST_INIT: Option<fn(&mut Self)> = None;
-
-    const TYPE_INFO: TypeInfo = TypeInfo {
-        name: Self::TYPE_NAME.as_ptr(),
-        parent: Self::ParentType::TYPE_NAME.as_ptr(),
-        instance_size: core::mem::size_of::<Self>(),
-        instance_align: core::mem::align_of::<Self>(),
-        instance_init: match Self::INSTANCE_INIT {
-            None => None,
-            Some(_) => Some(rust_instance_init::<Self>),
-        },
-        instance_post_init: match Self::INSTANCE_POST_INIT {
-            None => None,
-            Some(_) => Some(rust_instance_post_init::<Self>),
-        },
-        instance_finalize: Self::INSTANCE_FINALIZE,
-        abstract_: Self::ABSTRACT,
-        class_size: core::mem::size_of::<Self::Class>(),
-        class_init: <Self as ClassInitImpl>::CLASS_INIT,
-        class_base_init: <Self as ClassInitImpl>::CLASS_BASE_INIT,
-        class_data: core::ptr::null_mut(),
-        interfaces: core::ptr::null_mut(),
-    };
-}
-
-/// Trait used to fill in a class struct.
-///
-/// Each QOM class that has virtual methods describes them in a
-/// _class struct_.  Class structs include a parent field corresponding
-/// to the vtable of the parent class, all the way up to [`ObjectClass`].
-/// Each QOM type has one such class struct.
-///
-/// The Rust implementation of methods will usually come from a trait
-/// like [`ObjectImpl`] or [`DeviceImpl`](crate::device_class::DeviceImpl).
-pub trait ClassInitImpl {
-    /// Function that is called after all parent class initialization
-    /// has occurred.  On entry, the virtual method pointers are set to
-    /// the default values coming from the parent classes; the function
-    /// can change them to override virtual methods of a parent class.
-    const CLASS_INIT: Option<unsafe extern "C" fn(klass: *mut ObjectClass, data: *mut c_void)>;
-
-    /// Called on descendent classes after all parent class initialization
-    /// has occurred, but before the class itself is initialized.  This
-    /// is only useful if a class is not a leaf, and can be used to undo
-    /// the effects of copying the contents of the parent's class struct
-    /// to the descendants.
-    const CLASS_BASE_INIT: Option<
-        unsafe extern "C" fn(klass: *mut ObjectClass, data: *mut c_void),
-    >;
-}
-
-#[macro_export]
-macro_rules! module_init {
-    ($type:ident => $body:block) => {
-        const _: () = {
-            #[used]
-            #[cfg_attr(
-                not(any(target_vendor = "apple", target_os = "windows")),
-                link_section = ".init_array"
-            )]
-            #[cfg_attr(target_vendor = "apple", link_section = "__DATA,__mod_init_func")]
-            #[cfg_attr(target_os = "windows", link_section = ".CRT$XCU")]
-            pub static LOAD_MODULE: extern "C" fn() = {
-                extern "C" fn init_fn() {
-                    $body
-                }
-
-                extern "C" fn ctor_fn() {
-                    unsafe {
-                        $crate::bindings::register_module_init(
-                            Some(init_fn),
-                            $crate::bindings::module_init_type::$type,
-                        );
-                    }
-                }
-
-                ctor_fn
-            };
-        };
-    };
-
-    // shortcut because it's quite common that $body needs unsafe {}
-    ($type:ident => unsafe $body:block) => {
-        $crate::module_init! {
-            $type => { unsafe { $body } }
-        }
-    };
-}
diff --git a/rust/qemu-api/src/lib.rs b/rust/qemu-api/src/lib.rs
index 9e007e1..4b43e02 100644
--- a/rust/qemu-api/src/lib.rs
+++ b/rust/qemu-api/src/lib.rs
@@ -14,11 +14,13 @@ pub mod prelude;
 
 pub mod bitops;
 pub mod c_str;
+pub mod callbacks;
 pub mod cell;
-pub mod definitions;
-pub mod device_class;
 pub mod irq;
+pub mod module;
 pub mod offset_of;
+pub mod qdev;
+pub mod qom;
 pub mod sysbus;
 pub mod vmstate;
 pub mod zeroable;
diff --git a/rust/qemu-api/src/module.rs b/rust/qemu-api/src/module.rs
new file mode 100644
index 0000000..fa5cea3
--- /dev/null
+++ b/rust/qemu-api/src/module.rs
@@ -0,0 +1,43 @@
+// Copyright 2024, Linaro Limited
+// Author(s): Manos Pitsidianakis <manos.pitsidianakis@linaro.org>
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+//! Macro to register blocks of code that run as QEMU starts up.
+
+#[macro_export]
+macro_rules! module_init {
+    ($type:ident => $body:block) => {
+        const _: () = {
+            #[used]
+            #[cfg_attr(
+                not(any(target_vendor = "apple", target_os = "windows")),
+                link_section = ".init_array"
+            )]
+            #[cfg_attr(target_vendor = "apple", link_section = "__DATA,__mod_init_func")]
+            #[cfg_attr(target_os = "windows", link_section = ".CRT$XCU")]
+            pub static LOAD_MODULE: extern "C" fn() = {
+                extern "C" fn init_fn() {
+                    $body
+                }
+
+                extern "C" fn ctor_fn() {
+                    unsafe {
+                        $crate::bindings::register_module_init(
+                            Some(init_fn),
+                            $crate::bindings::module_init_type::$type,
+                        );
+                    }
+                }
+
+                ctor_fn
+            };
+        };
+    };
+
+    // shortcut because it's quite common that $body needs unsafe {}
+    ($type:ident => unsafe $body:block) => {
+        $crate::module_init! {
+            $type => { unsafe { $body } }
+        }
+    };
+}
diff --git a/rust/qemu-api/src/prelude.rs b/rust/qemu-api/src/prelude.rs
index 1b8677b..6f32dee 100644
--- a/rust/qemu-api/src/prelude.rs
+++ b/rust/qemu-api/src/prelude.rs
@@ -7,4 +7,12 @@ pub use crate::bitops::IntegerExt;
 pub use crate::cell::BqlCell;
 pub use crate::cell::BqlRefCell;
 
-pub use crate::definitions::ObjectType;
+pub use crate::qom::IsA;
+pub use crate::qom::Object;
+pub use crate::qom::ObjectCast;
+pub use crate::qom::ObjectCastMut;
+pub use crate::qom::ObjectDeref;
+pub use crate::qom::ObjectMethods;
+pub use crate::qom::ObjectType;
+
+pub use crate::qom_isa;
diff --git a/rust/qemu-api/src/device_class.rs b/rust/qemu-api/src/qdev.rs
index 03d03fe..686054e 100644
--- a/rust/qemu-api/src/device_class.rs
+++ b/rust/qemu-api/src/qdev.rs
@@ -2,12 +2,17 @@
 // Author(s): Manos Pitsidianakis <manos.pitsidianakis@linaro.org>
 // SPDX-License-Identifier: GPL-2.0-or-later
 
-use std::{ffi::CStr, os::raw::c_void};
+//! Bindings to create devices and access device functionality from Rust.
+
+use std::ffi::CStr;
+
+pub use bindings::{DeviceClass, DeviceState, Property};
 
 use crate::{
-    bindings::{self, DeviceClass, DeviceState, Error, ObjectClass, Property, VMStateDescription},
+    bindings::{self, Error},
     prelude::*,
-    zeroable::Zeroable,
+    qom::{ClassInitImpl, ObjectClass},
+    vmstate::VMStateDescription,
 };
 
 /// Trait providing the contents of [`DeviceClass`].
@@ -31,7 +36,7 @@ pub trait DeviceImpl {
     /// device.  Not a `const` because referencing statics in constants
     /// is unstable until Rust 1.83.0.
     fn properties() -> &'static [Property] {
-        &[Zeroable::ZERO; 1]
+        &[]
     }
 
     /// A `VMStateDescription` providing the migration format for the device
@@ -45,7 +50,7 @@ pub trait DeviceImpl {
 /// # Safety
 ///
 /// This function is only called through the QOM machinery and
-/// the `impl_device_class!` macro.
+/// used by the `ClassInitImpl<DeviceClass>` trait.
 /// We expect the FFI user of this function to pass a valid pointer that
 /// can be downcasted to type `T`. We also expect the device is
 /// readable/writeable from one thread at any time.
@@ -66,43 +71,31 @@ unsafe extern "C" fn rust_reset_fn<T: DeviceImpl>(dev: *mut DeviceState) {
     T::RESET.unwrap()(unsafe { &mut *state });
 }
 
-/// # Safety
-///
-/// We expect the FFI user of this function to pass a valid pointer that
-/// can be downcasted to type `DeviceClass`, because `T` implements
-/// `DeviceImpl`.
-pub unsafe extern "C" fn rust_device_class_init<T: DeviceImpl>(
-    klass: *mut ObjectClass,
-    _: *mut c_void,
-) {
-    let mut dc = ::core::ptr::NonNull::new(klass.cast::<DeviceClass>()).unwrap();
-    unsafe {
-        let dc = dc.as_mut();
+impl<T> ClassInitImpl<DeviceClass> for T
+where
+    T: ClassInitImpl<ObjectClass> + DeviceImpl,
+{
+    fn class_init(dc: &mut DeviceClass) {
         if <T as DeviceImpl>::REALIZE.is_some() {
             dc.realize = Some(rust_realize_fn::<T>);
         }
         if <T as DeviceImpl>::RESET.is_some() {
-            bindings::device_class_set_legacy_reset(dc, Some(rust_reset_fn::<T>));
+            unsafe {
+                bindings::device_class_set_legacy_reset(dc, Some(rust_reset_fn::<T>));
+            }
         }
         if let Some(vmsd) = <T as DeviceImpl>::vmsd() {
             dc.vmsd = vmsd;
         }
-        bindings::device_class_set_props(dc, <T as DeviceImpl>::properties().as_ptr());
-    }
-}
-
-#[macro_export]
-macro_rules! impl_device_class {
-    ($type:ty) => {
-        impl $crate::definitions::ClassInitImpl for $type {
-            const CLASS_INIT: Option<
-                unsafe extern "C" fn(klass: *mut ObjectClass, data: *mut ::std::os::raw::c_void),
-            > = Some($crate::device_class::rust_device_class_init::<$type>);
-            const CLASS_BASE_INIT: Option<
-                unsafe extern "C" fn(klass: *mut ObjectClass, data: *mut ::std::os::raw::c_void),
-            > = None;
+        let prop = <T as DeviceImpl>::properties();
+        if !prop.is_empty() {
+            unsafe {
+                bindings::device_class_set_props_n(dc, prop.as_ptr(), prop.len());
+            }
         }
-    };
+
+        <T as ClassInitImpl<ObjectClass>>::class_init(&mut dc.parent_class);
+    }
 }
 
 #[macro_export]
@@ -134,7 +127,7 @@ macro_rules! define_property {
 macro_rules! declare_properties {
     ($ident:ident, $($prop:expr),*$(,)*) => {
         pub static $ident: [$crate::bindings::Property; {
-            let mut len = 1;
+            let mut len = 0;
             $({
                 _ = stringify!($prop);
                 len += 1;
@@ -142,13 +135,13 @@ macro_rules! declare_properties {
             len
         }] = [
             $($prop),*,
-            $crate::zeroable::Zeroable::ZERO,
         ];
     };
 }
 
-unsafe impl ObjectType for bindings::DeviceState {
-    type Class = bindings::DeviceClass;
+unsafe impl ObjectType for DeviceState {
+    type Class = DeviceClass;
     const TYPE_NAME: &'static CStr =
         unsafe { CStr::from_bytes_with_nul_unchecked(bindings::TYPE_DEVICE) };
 }
+qom_isa!(DeviceState: Object);
diff --git a/rust/qemu-api/src/qom.rs b/rust/qemu-api/src/qom.rs
new file mode 100644
index 0000000..7d5fbef
--- /dev/null
+++ b/rust/qemu-api/src/qom.rs
@@ -0,0 +1,584 @@
+// Copyright 2024, Linaro Limited
+// Author(s): Manos Pitsidianakis <manos.pitsidianakis@linaro.org>
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+//! Bindings to access QOM functionality from Rust.
+//!
+//! The QEMU Object Model (QOM) provides inheritance and dynamic typing for QEMU
+//! devices. This module makes QOM's features available in Rust through three
+//! main mechanisms:
+//!
+//! * Automatic creation and registration of `TypeInfo` for classes that are
+//!   written in Rust, as well as mapping between Rust traits and QOM vtables.
+//!
+//! * Type-safe casting between parent and child classes, through the [`IsA`]
+//!   trait and methods such as [`upcast`](ObjectCast::upcast) and
+//!   [`downcast`](ObjectCast::downcast).
+//!
+//! * Automatic delegation of parent class methods to child classes. When a
+//!   trait uses [`IsA`] as a bound, its contents become available to all child
+//!   classes through blanket implementations. This works both for class methods
+//!   and for instance methods accessed through references or smart pointers.
+//!
+//! # Structure of a class
+//!
+//! A leaf class only needs a struct holding instance state. The struct must
+//! implement the [`ObjectType`] and [`IsA`] traits, as well as any `*Impl`
+//! traits that exist for its superclasses.
+//!
+//! If a class has subclasses, it will also provide a struct for instance data,
+//! with the same characteristics as for concrete classes, but it also needs
+//! additional components to support virtual methods:
+//!
+//! * a struct for class data, for example `DeviceClass`. This corresponds to
+//!   the C "class struct" and holds the vtable that is used by instances of the
+//!   class and its subclasses. It must start with its parent's class struct.
+//!
+//! * a trait for virtual method implementations, for example `DeviceImpl`.
+//!   Child classes implement this trait to provide their own behavior for
+//!   virtual methods. The trait's methods take `&self` to access instance data.
+//!
+//! * an implementation of [`ClassInitImpl`], for example
+//!   `ClassInitImpl<DeviceClass>`. This fills the vtable in the class struct;
+//!   the source for this is the `*Impl` trait; the associated consts and
+//!   functions if needed are wrapped to map C types into Rust types.
+//!
+//! * a trait for instance methods, for example `DeviceMethods`. This trait is
+//!   automatically implemented for any reference or smart pointer to a device
+//!   instance.  It calls into the vtable provides access across all subclasses
+//!   to methods defined for the class.
+//!
+//! * optionally, a trait for class methods, for example `DeviceClassMethods`.
+//!   This provides access to class-wide functionality that doesn't depend on
+//!   instance data. Like instance methods, these are automatically inherited by
+//!   child classes.
+
+use std::{
+    ffi::CStr,
+    ops::{Deref, DerefMut},
+    os::raw::c_void,
+};
+
+pub use bindings::{Object, ObjectClass};
+
+use crate::bindings::{self, object_dynamic_cast, object_get_class, object_get_typename, TypeInfo};
+
+/// Marker trait: `Self` can be statically upcasted to `P` (i.e. `P` is a direct
+/// or indirect parent of `Self`).
+///
+/// # Safety
+///
+/// The struct `Self` must be `#[repr(C)]` and must begin, directly or
+/// indirectly, with a field of type `P`.  This ensures that invalid casts,
+/// which rely on `IsA<>` for static checking, are rejected at compile time.
+pub unsafe trait IsA<P: ObjectType>: ObjectType {}
+
+// SAFETY: it is always safe to cast to your own type
+unsafe impl<T: ObjectType> IsA<T> for T {}
+
+/// Macro to mark superclasses of QOM classes.  This enables type-safe
+/// up- and downcasting.
+///
+/// # Safety
+///
+/// This macro is a thin wrapper around the [`IsA`] trait and performs
+/// no checking whatsoever of what is declared.  It is the caller's
+/// responsibility to have $struct begin, directly or indirectly, with
+/// a field of type `$parent`.
+#[macro_export]
+macro_rules! qom_isa {
+    ($struct:ty : $($parent:ty),* ) => {
+        $(
+            // SAFETY: it is the caller responsibility to have $parent as the
+            // first field
+            unsafe impl $crate::qom::IsA<$parent> for $struct {}
+
+            impl AsRef<$parent> for $struct {
+                fn as_ref(&self) -> &$parent {
+                    // SAFETY: follows the same rules as for IsA<U>, which is
+                    // declared above.
+                    let ptr: *const Self = self;
+                    unsafe { &*ptr.cast::<$parent>() }
+                }
+            }
+        )*
+    };
+}
+
+unsafe extern "C" fn rust_instance_init<T: ObjectImpl>(obj: *mut Object) {
+    // SAFETY: obj is an instance of T, since rust_instance_init<T>
+    // is called from QOM core as the instance_init function
+    // for class T
+    unsafe { T::INSTANCE_INIT.unwrap()(&mut *obj.cast::<T>()) }
+}
+
+unsafe extern "C" fn rust_instance_post_init<T: ObjectImpl>(obj: *mut Object) {
+    // SAFETY: obj is an instance of T, since rust_instance_post_init<T>
+    // is called from QOM core as the instance_post_init function
+    // for class T
+    //
+    // FIXME: it's not really guaranteed that there are no backpointers to
+    // obj; it's quite possible that they have been created by instance_init().
+    // The receiver should be &self, not &mut self.
+    T::INSTANCE_POST_INIT.unwrap()(unsafe { &mut *obj.cast::<T>() })
+}
+
+unsafe extern "C" fn rust_class_init<T: ObjectType + ClassInitImpl<T::Class>>(
+    klass: *mut ObjectClass,
+    _data: *mut c_void,
+) {
+    // SAFETY: klass is a T::Class, since rust_class_init<T>
+    // is called from QOM core as the class_init function
+    // for class T
+    T::class_init(unsafe { &mut *klass.cast::<T::Class>() })
+}
+
+/// Trait exposed by all structs corresponding to QOM objects.
+///
+/// # Safety
+///
+/// For classes declared in C:
+///
+/// - `Class` and `TYPE` must match the data in the `TypeInfo`;
+///
+/// - the first field of the struct must be of the instance type corresponding
+///   to the superclass, as declared in the `TypeInfo`
+///
+/// - likewise, the first field of the `Class` struct must be of the class type
+///   corresponding to the superclass
+///
+/// For classes declared in Rust and implementing [`ObjectImpl`]:
+///
+/// - the struct must be `#[repr(C)]`;
+///
+/// - the first field of the struct must be of the instance struct corresponding
+///   to the superclass, which is `ObjectImpl::ParentType`
+///
+/// - likewise, the first field of the `Class` must be of the class struct
+///   corresponding to the superclass, which is `ObjectImpl::ParentType::Class`.
+pub unsafe trait ObjectType: Sized {
+    /// The QOM class object corresponding to this struct.  This is used
+    /// to automatically generate a `class_init` method.
+    type Class;
+
+    /// The name of the type, which can be passed to `object_new()` to
+    /// generate an instance of this type.
+    const TYPE_NAME: &'static CStr;
+
+    /// Return the receiver as an Object.  This is always safe, even
+    /// if this type represents an interface.
+    fn as_object(&self) -> &Object {
+        unsafe { &*self.as_object_ptr() }
+    }
+
+    /// Return the receiver as a const raw pointer to Object.
+    /// This is preferrable to `as_object_mut_ptr()` if a C
+    /// function only needs a `const Object *`.
+    fn as_object_ptr(&self) -> *const Object {
+        self.as_ptr().cast()
+    }
+
+    /// Return the receiver as a mutable raw pointer to Object.
+    ///
+    /// # Safety
+    ///
+    /// This cast is always safe, but because the result is mutable
+    /// and the incoming reference is not, this should only be used
+    /// for calls to C functions, and only if needed.
+    unsafe fn as_object_mut_ptr(&self) -> *mut Object {
+        self.as_object_ptr() as *mut _
+    }
+}
+
+/// This trait provides safe casting operations for QOM objects to raw pointers,
+/// to be used for example for FFI. The trait can be applied to any kind of
+/// reference or smart pointers, and enforces correctness through the [`IsA`]
+/// trait.
+pub trait ObjectDeref: Deref
+where
+    Self::Target: ObjectType,
+{
+    /// Convert to a const Rust pointer, to be used for example for FFI.
+    /// The target pointer type must be the type of `self` or a superclass
+    fn as_ptr<U: ObjectType>(&self) -> *const U
+    where
+        Self::Target: IsA<U>,
+    {
+        let ptr: *const Self::Target = self.deref();
+        ptr.cast::<U>()
+    }
+
+    /// Convert to a mutable Rust pointer, to be used for example for FFI.
+    /// The target pointer type must be the type of `self` or a superclass.
+    /// Used to implement interior mutability for objects.
+    ///
+    /// # Safety
+    ///
+    /// This method is unsafe because it overrides const-ness of `&self`.
+    /// Bindings to C APIs will use it a lot, but otherwise it should not
+    /// be necessary.
+    unsafe fn as_mut_ptr<U: ObjectType>(&self) -> *mut U
+    where
+        Self::Target: IsA<U>,
+    {
+        #[allow(clippy::as_ptr_cast_mut)]
+        {
+            self.as_ptr::<U>() as *mut _
+        }
+    }
+}
+
+/// Trait that adds extra functionality for `&T` where `T` is a QOM
+/// object type.  Allows conversion to/from C objects in generic code.
+pub trait ObjectCast: ObjectDeref + Copy
+where
+    Self::Target: ObjectType,
+{
+    /// Safely convert from a derived type to one of its parent types.
+    ///
+    /// This is always safe; the [`IsA`] trait provides static verification
+    /// trait that `Self` dereferences to `U` or a child of `U`.
+    fn upcast<'a, U: ObjectType>(self) -> &'a U
+    where
+        Self::Target: IsA<U>,
+        Self: 'a,
+    {
+        // SAFETY: soundness is declared via IsA<U>, which is an unsafe trait
+        unsafe { self.unsafe_cast::<U>() }
+    }
+
+    /// Attempt to convert to a derived type.
+    ///
+    /// Returns `None` if the object is not actually of type `U`. This is
+    /// verified at runtime by checking the object's type information.
+    fn downcast<'a, U: IsA<Self::Target>>(self) -> Option<&'a U>
+    where
+        Self: 'a,
+    {
+        self.dynamic_cast::<U>()
+    }
+
+    /// Attempt to convert between any two types in the QOM hierarchy.
+    ///
+    /// Returns `None` if the object is not actually of type `U`. This is
+    /// verified at runtime by checking the object's type information.
+    fn dynamic_cast<'a, U: ObjectType>(self) -> Option<&'a U>
+    where
+        Self: 'a,
+    {
+        unsafe {
+            // SAFETY: upcasting to Object is always valid, and the
+            // return type is either NULL or the argument itself
+            let result: *const U =
+                object_dynamic_cast(self.as_object_mut_ptr(), U::TYPE_NAME.as_ptr()).cast();
+
+            result.as_ref()
+        }
+    }
+
+    /// Convert to any QOM type without verification.
+    ///
+    /// # Safety
+    ///
+    /// What safety? You need to know yourself that the cast is correct; only
+    /// use when performance is paramount.  It is still better than a raw
+    /// pointer `cast()`, which does not even check that you remain in the
+    /// realm of QOM `ObjectType`s.
+    ///
+    /// `unsafe_cast::<Object>()` is always safe.
+    unsafe fn unsafe_cast<'a, U: ObjectType>(self) -> &'a U
+    where
+        Self: 'a,
+    {
+        unsafe { &*(self.as_ptr::<Self::Target>().cast::<U>()) }
+    }
+}
+
+impl<T: ObjectType> ObjectDeref for &T {}
+impl<T: ObjectType> ObjectCast for &T {}
+
+/// Trait for mutable type casting operations in the QOM hierarchy.
+///
+/// This trait provides the mutable counterparts to [`ObjectCast`]'s conversion
+/// functions. Unlike `ObjectCast`, this trait returns `Result` for fallible
+/// conversions to preserve the original smart pointer if the cast fails. This
+/// is necessary because mutable references cannot be copied, so a failed cast
+/// must return ownership of the original reference. For example:
+///
+/// ```ignore
+/// let mut dev = get_device();
+/// // If this fails, we need the original `dev` back to try something else
+/// match dev.dynamic_cast_mut::<FooDevice>() {
+///    Ok(foodev) => /* use foodev */,
+///    Err(dev) => /* still have ownership of dev */
+/// }
+/// ```
+pub trait ObjectCastMut: Sized + ObjectDeref + DerefMut
+where
+    Self::Target: ObjectType,
+{
+    /// Safely convert from a derived type to one of its parent types.
+    ///
+    /// This is always safe; the [`IsA`] trait provides static verification
+    /// that `Self` dereferences to `U` or a child of `U`.
+    fn upcast_mut<'a, U: ObjectType>(self) -> &'a mut U
+    where
+        Self::Target: IsA<U>,
+        Self: 'a,
+    {
+        // SAFETY: soundness is declared via IsA<U>, which is an unsafe trait
+        unsafe { self.unsafe_cast_mut::<U>() }
+    }
+
+    /// Attempt to convert to a derived type.
+    ///
+    /// Returns `Ok(..)` if the object is of type `U`, or `Err(self)` if the
+    /// object if the conversion failed. This is verified at runtime by
+    /// checking the object's type information.
+    fn downcast_mut<'a, U: IsA<Self::Target>>(self) -> Result<&'a mut U, Self>
+    where
+        Self: 'a,
+    {
+        self.dynamic_cast_mut::<U>()
+    }
+
+    /// Attempt to convert between any two types in the QOM hierarchy.
+    ///
+    /// Returns `Ok(..)` if the object is of type `U`, or `Err(self)` if the
+    /// object if the conversion failed. This is verified at runtime by
+    /// checking the object's type information.
+    fn dynamic_cast_mut<'a, U: ObjectType>(self) -> Result<&'a mut U, Self>
+    where
+        Self: 'a,
+    {
+        unsafe {
+            // SAFETY: upcasting to Object is always valid, and the
+            // return type is either NULL or the argument itself
+            let result: *mut U =
+                object_dynamic_cast(self.as_object_mut_ptr(), U::TYPE_NAME.as_ptr()).cast();
+
+            result.as_mut().ok_or(self)
+        }
+    }
+
+    /// Convert to any QOM type without verification.
+    ///
+    /// # Safety
+    ///
+    /// What safety? You need to know yourself that the cast is correct; only
+    /// use when performance is paramount.  It is still better than a raw
+    /// pointer `cast()`, which does not even check that you remain in the
+    /// realm of QOM `ObjectType`s.
+    ///
+    /// `unsafe_cast::<Object>()` is always safe.
+    unsafe fn unsafe_cast_mut<'a, U: ObjectType>(self) -> &'a mut U
+    where
+        Self: 'a,
+    {
+        unsafe { &mut *self.as_mut_ptr::<Self::Target>().cast::<U>() }
+    }
+}
+
+impl<T: ObjectType> ObjectDeref for &mut T {}
+impl<T: ObjectType> ObjectCastMut for &mut T {}
+
+/// Trait a type must implement to be registered with QEMU.
+pub trait ObjectImpl: ObjectType + ClassInitImpl<Self::Class> {
+    /// The parent of the type.  This should match the first field of
+    /// the struct that implements `ObjectImpl`:
+    type ParentType: ObjectType;
+
+    /// Whether the object can be instantiated
+    const ABSTRACT: bool = false;
+    const INSTANCE_FINALIZE: Option<unsafe extern "C" fn(obj: *mut Object)> = None;
+
+    /// Function that is called to initialize an object.  The parent class will
+    /// have already been initialized so the type is only responsible for
+    /// initializing its own members.
+    ///
+    /// FIXME: The argument is not really a valid reference. `&mut
+    /// MaybeUninit<Self>` would be a better description.
+    const INSTANCE_INIT: Option<unsafe fn(&mut Self)> = None;
+
+    /// Function that is called to finish initialization of an object, once
+    /// `INSTANCE_INIT` functions have been called.
+    const INSTANCE_POST_INIT: Option<fn(&mut Self)> = None;
+
+    /// Called on descendent classes after all parent class initialization
+    /// has occurred, but before the class itself is initialized.  This
+    /// is only useful if a class is not a leaf, and can be used to undo
+    /// the effects of copying the contents of the parent's class struct
+    /// to the descendants.
+    const CLASS_BASE_INIT: Option<
+        unsafe extern "C" fn(klass: *mut ObjectClass, data: *mut c_void),
+    > = None;
+
+    const TYPE_INFO: TypeInfo = TypeInfo {
+        name: Self::TYPE_NAME.as_ptr(),
+        parent: Self::ParentType::TYPE_NAME.as_ptr(),
+        instance_size: core::mem::size_of::<Self>(),
+        instance_align: core::mem::align_of::<Self>(),
+        instance_init: match Self::INSTANCE_INIT {
+            None => None,
+            Some(_) => Some(rust_instance_init::<Self>),
+        },
+        instance_post_init: match Self::INSTANCE_POST_INIT {
+            None => None,
+            Some(_) => Some(rust_instance_post_init::<Self>),
+        },
+        instance_finalize: Self::INSTANCE_FINALIZE,
+        abstract_: Self::ABSTRACT,
+        class_size: core::mem::size_of::<Self::Class>(),
+        class_init: Some(rust_class_init::<Self>),
+        class_base_init: Self::CLASS_BASE_INIT,
+        class_data: core::ptr::null_mut(),
+        interfaces: core::ptr::null_mut(),
+    };
+
+    // methods on ObjectClass
+    const UNPARENT: Option<fn(&Self)> = None;
+}
+
+/// Internal trait used to automatically fill in a class struct.
+///
+/// Each QOM class that has virtual methods describes them in a
+/// _class struct_.  Class structs include a parent field corresponding
+/// to the vtable of the parent class, all the way up to [`ObjectClass`].
+/// Each QOM type has one such class struct; this trait takes care of
+/// initializing the `T` part of the class struct, for the type that
+/// implements the trait.
+///
+/// Each struct will implement this trait with `T` equal to each
+/// superclass.  For example, a device should implement at least
+/// `ClassInitImpl<`[`DeviceClass`](crate::qdev::DeviceClass)`>` and
+/// `ClassInitImpl<`[`ObjectClass`]`>`.  Such implementations are made
+/// in one of two ways.
+///
+/// For most superclasses, `ClassInitImpl` is provided by the `qemu-api`
+/// crate itself.  The Rust implementation of methods will come from a
+/// trait like [`ObjectImpl`] or [`DeviceImpl`](crate::qdev::DeviceImpl),
+/// and `ClassInitImpl` is provided by blanket implementations that
+/// operate on all implementors of the `*Impl`* trait.  For example:
+///
+/// ```ignore
+/// impl<T> ClassInitImpl<DeviceClass> for T
+/// where
+///     T: ClassInitImpl<ObjectClass> + DeviceImpl,
+/// ```
+///
+/// The bound on `ClassInitImpl<ObjectClass>` is needed so that,
+/// after initializing the `DeviceClass` part of the class struct,
+/// the parent [`ObjectClass`] is initialized as well.
+///
+/// The other case is when manual implementation of the trait is needed.
+/// This covers the following cases:
+///
+/// * if a class implements a QOM interface, the Rust code _has_ to define its
+///   own class struct `FooClass` and implement `ClassInitImpl<FooClass>`.
+///   `ClassInitImpl<FooClass>`'s `class_init` method will then forward to
+///   multiple other `class_init`s, for the interfaces as well as the
+///   superclass. (Note that there is no Rust example yet for using interfaces).
+///
+/// * for classes implemented outside the ``qemu-api`` crate, it's not possible
+///   to add blanket implementations like the above one, due to orphan rules. In
+///   that case, the easiest solution is to implement
+///   `ClassInitImpl<YourSuperclass>` for each subclass and not have a
+///   `YourSuperclassImpl` trait at all.
+///
+/// ```ignore
+/// impl ClassInitImpl<YourSuperclass> for YourSubclass {
+///     fn class_init(klass: &mut YourSuperclass) {
+///         klass.some_method = Some(Self::some_method);
+///         <Self as ClassInitImpl<SysBusDeviceClass>>::class_init(&mut klass.parent_class);
+///     }
+/// }
+/// ```
+///
+///   While this method incurs a small amount of code duplication,
+///   it is generally limited to the recursive call on the last line.
+///   This is because classes defined in Rust do not need the same
+///   glue code that is needed when the classes are defined in C code.
+///   You may consider using a macro if you have many subclasses.
+pub trait ClassInitImpl<T> {
+    /// Initialize `klass` to point to the virtual method implementations
+    /// for `Self`.  On entry, the virtual method pointers are set to
+    /// the default values coming from the parent classes; the function
+    /// can change them to override virtual methods of a parent class.
+    ///
+    /// The virtual method implementations usually come from another
+    /// trait, for example [`DeviceImpl`](crate::qdev::DeviceImpl)
+    /// when `T` is [`DeviceClass`](crate::qdev::DeviceClass).
+    ///
+    /// On entry, `klass`'s parent class is initialized, while the other fields
+    /// are all zero; it is therefore assumed that all fields in `T` can be
+    /// zeroed, otherwise it would not be possible to provide the class as a
+    /// `&mut T`.  TODO: add a bound of [`Zeroable`](crate::zeroable::Zeroable)
+    /// to T; this is more easily done once Zeroable does not require a manual
+    /// implementation (Rust 1.75.0).
+    fn class_init(klass: &mut T);
+}
+
+/// # Safety
+///
+/// We expect the FFI user of this function to pass a valid pointer that
+/// can be downcasted to type `T`. We also expect the device is
+/// readable/writeable from one thread at any time.
+unsafe extern "C" fn rust_unparent_fn<T: ObjectImpl>(dev: *mut Object) {
+    unsafe {
+        assert!(!dev.is_null());
+        let state = core::ptr::NonNull::new_unchecked(dev.cast::<T>());
+        T::UNPARENT.unwrap()(state.as_ref());
+    }
+}
+
+impl<T> ClassInitImpl<ObjectClass> for T
+where
+    T: ObjectImpl,
+{
+    fn class_init(oc: &mut ObjectClass) {
+        if <T as ObjectImpl>::UNPARENT.is_some() {
+            oc.unparent = Some(rust_unparent_fn::<T>);
+        }
+    }
+}
+
+unsafe impl ObjectType for Object {
+    type Class = ObjectClass;
+    const TYPE_NAME: &'static CStr =
+        unsafe { CStr::from_bytes_with_nul_unchecked(bindings::TYPE_OBJECT) };
+}
+
+/// Trait for methods exposed by the Object class.  The methods can be
+/// called on all objects that have the trait `IsA<Object>`.
+///
+/// The trait should only be used through the blanket implementation,
+/// which guarantees safety via `IsA`
+pub trait ObjectMethods: ObjectDeref
+where
+    Self::Target: IsA<Object>,
+{
+    /// Return the name of the type of `self`
+    fn typename(&self) -> std::borrow::Cow<'_, str> {
+        let obj = self.upcast::<Object>();
+        // SAFETY: safety of this is the requirement for implementing IsA
+        // The result of the C API has static lifetime
+        unsafe {
+            let p = object_get_typename(obj.as_mut_ptr());
+            CStr::from_ptr(p).to_string_lossy()
+        }
+    }
+
+    fn get_class(&self) -> &'static <Self::Target as ObjectType>::Class {
+        let obj = self.upcast::<Object>();
+
+        // SAFETY: all objects can call object_get_class; the actual class
+        // type is guaranteed by the implementation of `ObjectType` and
+        // `ObjectImpl`.
+        let klass: &'static <Self::Target as ObjectType>::Class =
+            unsafe { &*object_get_class(obj.as_mut_ptr()).cast() };
+
+        klass
+    }
+}
+
+impl<R: ObjectDeref> ObjectMethods for R where R::Target: IsA<Object> {}
diff --git a/rust/qemu-api/src/sysbus.rs b/rust/qemu-api/src/sysbus.rs
index 5ee0685..8193734 100644
--- a/rust/qemu-api/src/sysbus.rs
+++ b/rust/qemu-api/src/sysbus.rs
@@ -6,13 +6,31 @@ use std::{ffi::CStr, ptr::addr_of};
 
 pub use bindings::{SysBusDevice, SysBusDeviceClass};
 
-use crate::{bindings, cell::bql_locked, irq::InterruptSource, prelude::*};
+use crate::{
+    bindings,
+    cell::bql_locked,
+    irq::InterruptSource,
+    prelude::*,
+    qdev::{DeviceClass, DeviceState},
+    qom::ClassInitImpl,
+};
 
 unsafe impl ObjectType for SysBusDevice {
     type Class = SysBusDeviceClass;
     const TYPE_NAME: &'static CStr =
         unsafe { CStr::from_bytes_with_nul_unchecked(bindings::TYPE_SYS_BUS_DEVICE) };
 }
+qom_isa!(SysBusDevice: DeviceState, Object);
+
+// TODO: add SysBusDeviceImpl
+impl<T> ClassInitImpl<SysBusDeviceClass> for T
+where
+    T: ClassInitImpl<DeviceClass>,
+{
+    fn class_init(sdc: &mut SysBusDeviceClass) {
+        <T as ClassInitImpl<DeviceClass>>::class_init(&mut sdc.parent_class);
+    }
+}
 
 impl SysBusDevice {
     /// Return `self` cast to a mutable pointer, for use in calls to C code.
diff --git a/rust/qemu-api/src/vmstate.rs b/rust/qemu-api/src/vmstate.rs
index bedcf1e..63c897a 100644
--- a/rust/qemu-api/src/vmstate.rs
+++ b/rust/qemu-api/src/vmstate.rs
@@ -10,6 +10,8 @@
 //! [`vmstate_fields`](crate::vmstate_fields) are meant to be used when
 //! declaring a device model state struct.
 
+pub use crate::bindings::VMStateDescription;
+
 #[doc(alias = "VMSTATE_UNUSED_BUFFER")]
 #[macro_export]
 macro_rules! vmstate_unused_buffer {
@@ -104,28 +106,6 @@ macro_rules! vmstate_uint32 {
     }};
 }
 
-#[doc(alias = "VMSTATE_INT32_V")]
-#[macro_export]
-macro_rules! vmstate_int32_v {
-    ($field_name:ident, $struct_name:ty, $version_id:expr) => {{
-        $crate::vmstate_single!(
-            $field_name,
-            $struct_name,
-            $version_id,
-            ::core::ptr::addr_of!($crate::bindings::vmstate_info_int32),
-            ::core::mem::size_of::<i32>()
-        )
-    }};
-}
-
-#[doc(alias = "VMSTATE_INT32")]
-#[macro_export]
-macro_rules! vmstate_int32 {
-    ($field_name:ident, $struct_name:ty) => {{
-        $crate::vmstate_int32_v!($field_name, $struct_name, 0)
-    }};
-}
-
 #[doc(alias = "VMSTATE_ARRAY")]
 #[macro_export]
 macro_rules! vmstate_array {
@@ -328,7 +308,7 @@ macro_rules! vmstate_fields {
 }
 
 /// A transparent wrapper type for the `subsections` field of
-/// [`VMStateDescription`](crate::bindings::VMStateDescription).
+/// [`VMStateDescription`].
 ///
 /// This is necessary to be able to declare subsection descriptions as statics,
 /// because the only way to implement `Sync` for a foreign type (and `*const`
@@ -342,9 +322,8 @@ pub struct VMStateSubsectionsWrapper(pub &'static [*const crate::bindings::VMSta
 
 unsafe impl Sync for VMStateSubsectionsWrapper {}
 
-/// Helper macro to declare a list of subsections
-/// ([`VMStateDescription`](`crate::bindings::VMStateDescription`)) into a
-/// static and return a pointer to the array of pointers it created.
+/// Helper macro to declare a list of subsections ([`VMStateDescription`])
+/// into a static and return a pointer to the array of pointers it created.
 #[macro_export]
 macro_rules! vmstate_subsections {
     ($($subsection:expr),*$(,)*) => {{