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rust: qdev: const_refs_to_static

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Now that const_refs_static can be assumed, convert the members of
the DeviceImpl trait from functions to constants.  This lets the
compiler know that they have a 'static lifetime, and removes the
need for the weird "Box::leak()".

Reviewed-by: Zhao Liu <zhao1.liu@intel.com>
Link: https://lore.kernel.org/r/20250908105005.2119297-10-pbonzini@redhat.com
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Paolo Bonzini 2025-09-08 12:49:41 +02:00
parent dcdee1e718
commit 2a8a7bb8aa
6 changed files with 33 additions and 55 deletions
Download patch file Download diff file Expand all files Collapse all files

4
rust/hw/char/pl011/src/device.rs
View file

@ -172,9 +172,7 @@ impl ObjectImpl for PL011State {
}
impl DeviceImpl for PL011State {
fn vmsd() -> Option<VMStateDescription<Self>> {
Some(VMSTATE_PL011)
}
const VMSTATE: Option<VMStateDescription<Self>> = Some(VMSTATE_PL011);
const REALIZE: Option<fn(&Self) -> qemu_api::Result<()>> = Some(Self::realize);
}

9
rust/hw/timer/hpet/src/device.rs
View file

@ -1008,16 +1008,11 @@ const VMSTATE_HPET: VMStateDescription<HPETState> =
// SAFETY: HPET_PROPERTIES is a valid Property array constructed with the
// qemu_api::declare_properties macro.
unsafe impl qemu_api::qdev::DevicePropertiesImpl for HPETState {
fn properties() -> &'static [Property] {
&HPET_PROPERTIES
}
const PROPERTIES: &'static [Property] = &HPET_PROPERTIES;
}
impl DeviceImpl for HPETState {
fn vmsd() -> Option<VMStateDescription<Self>> {
Some(VMSTATE_HPET)
}
const VMSTATE: Option<VMStateDescription<Self>> = Some(VMSTATE_HPET);
const REALIZE: Option<fn(&Self) -> qemu_api::Result<()>> = Some(Self::realize);
}

8
rust/qemu-api-macros/src/lib.rs
View file

@ -289,11 +289,9 @@ fn derive_device_or_error(input: DeriveInput) -> Result<proc_macro2::TokenStream
Ok(quote_spanned! {input.span() =>
unsafe impl ::qemu_api::qdev::DevicePropertiesImpl for #name {
fn properties() -> &'static [::qemu_api::bindings::Property] {
static PROPERTIES: &[::qemu_api::bindings::Property] = &[#(#properties_expanded),*];
PROPERTIES
}
const PROPERTIES: &'static [::qemu_api::bindings::Property] = &[
#(#properties_expanded),*
];
}
})
}

44
rust/qemu-api-macros/src/tests.rs
View file

@ -101,18 +101,16 @@ fn test_derive_device() {
},
quote! {
unsafe impl ::qemu_api::qdev::DevicePropertiesImpl for DummyState {
fn properties() -> &'static [::qemu_api::bindings::Property] {
static PROPERTIES: &[::qemu_api::bindings::Property] =
&[::qemu_api::bindings::Property {
name: ::std::ffi::CStr::as_ptr(c"migrate_clock"),
info: <bool as ::qemu_api::qdev::QDevProp>::VALUE,
offset: ::core::mem::offset_of!(DummyState, migrate_clock) as isize,
set_default: true,
defval: ::qemu_api::bindings::Property__bindgen_ty_1 { u: true as u64 },
..::qemu_api::zeroable::Zeroable::ZERO
}];
PROPERTIES
}
const PROPERTIES: &'static [::qemu_api::bindings::Property] = &[
::qemu_api::bindings::Property {
name: ::std::ffi::CStr::as_ptr(c"migrate_clock"),
info: <bool as ::qemu_api::qdev::QDevProp>::VALUE,
offset: ::core::mem::offset_of!(DummyState, migrate_clock) as isize,
set_default: true,
defval: ::qemu_api::bindings::Property__bindgen_ty_1 { u: true as u64 },
..::qemu_api::zeroable::Zeroable::ZERO
}
];
}
}
);
@ -130,18 +128,16 @@ fn test_derive_device() {
},
quote! {
unsafe impl ::qemu_api::qdev::DevicePropertiesImpl for DummyState {
fn properties() -> &'static [::qemu_api::bindings::Property] {
static PROPERTIES: &[::qemu_api::bindings::Property] =
&[::qemu_api::bindings::Property {
name: ::std::ffi::CStr::as_ptr(c"migrate-clk"),
info: <bool as ::qemu_api::qdev::QDevProp>::VALUE,
offset: ::core::mem::offset_of!(DummyState, migrate_clock) as isize,
set_default: true,
defval: ::qemu_api::bindings::Property__bindgen_ty_1 { u: true as u64 },
..::qemu_api::zeroable::Zeroable::ZERO
}];
PROPERTIES
}
const PROPERTIES: &'static [::qemu_api::bindings::Property] = &[
::qemu_api::bindings::Property {
name: ::std::ffi::CStr::as_ptr(c"migrate-clk"),
info: <bool as ::qemu_api::qdev::QDevProp>::VALUE,
offset: ::core::mem::offset_of!(DummyState, migrate_clock) as isize,
set_default: true,
defval: ::qemu_api::bindings::Property__bindgen_ty_1 { u: true as u64 },
..::qemu_api::zeroable::Zeroable::ZERO
}
];
}
}
);

19
rust/qemu-api/src/qdev.rs
View file

@ -151,11 +151,8 @@ unsafe impl QDevProp for crate::chardev::CharBackend {
/// Caller is responsible for the validity of properties array.
pub unsafe trait DevicePropertiesImpl {
/// An array providing the properties that the user can set on the
/// device. Not a `const` because referencing statics in constants
/// is unstable until Rust 1.83.0.
fn properties() -> &'static [Property] {
&[]
}
/// device.
const PROPERTIES: &'static [Property] = &[];
}
/// Trait providing the contents of [`DeviceClass`].
@ -173,9 +170,7 @@ pub trait DeviceImpl:
/// A `VMStateDescription` providing the migration format for the device
/// Not a `const` because referencing statics in constants is unstable
/// until Rust 1.83.0.
fn vmsd() -> Option<VMStateDescription<Self>> {
None
}
const VMSTATE: Option<VMStateDescription<Self>> = None;
}
/// # Safety
@ -224,12 +219,10 @@ impl DeviceClass {
if <T as DeviceImpl>::REALIZE.is_some() {
self.realize = Some(rust_realize_fn::<T>);
}
if let Some(vmsd) = <T as DeviceImpl>::vmsd() {
// Give a 'static lifetime to the return value of vmsd().
// Temporary until vmsd() can be changed into a const.
self.vmsd = Box::leak(Box::new(vmsd.get()));
if let Some(ref vmsd) = <T as DeviceImpl>::VMSTATE {
self.vmsd = vmsd.as_ref();
}
let prop = <T as DevicePropertiesImpl>::properties();
let prop = <T as DevicePropertiesImpl>::PROPERTIES;
if !prop.is_empty() {
unsafe {
bindings::device_class_set_props_n(self, prop.as_ptr(), prop.len());

4
rust/qemu-api/tests/tests.rs
View file

@ -56,9 +56,7 @@ impl ObjectImpl for DummyState {
impl ResettablePhasesImpl for DummyState {}
impl DeviceImpl for DummyState {
fn vmsd() -> Option<VMStateDescription<Self>> {
Some(VMSTATE)
}
const VMSTATE: Option<VMStateDescription<Self>> = Some(VMSTATE);
}
#[repr(C)]