Reviewed-by: Zhao Liu <zhao1....@intel.com>
Signed-off-by: Paolo Bonzini <pbonz...@redhat.com>
---
rust/qemu-api/src/vmstate.rs | 61 ++++++++++++++++++++++++++++++++++--
1 file changed, 58 insertions(+), 3 deletions(-)
diff --git a/rust/qemu-api/src/vmstate.rs b/rust/qemu-api/src/vmstate.rs
index a262c315da1..9ac699b73b7 100644
--- a/rust/qemu-api/src/vmstate.rs
+++ b/rust/qemu-api/src/vmstate.rs
@@ -4,13 +4,18 @@
//! Helper macros to declare migration state for device models.
//!
-//! This module includes three families of macros:
+//! This module includes four families of macros:
//!
//! * [`vmstate_unused!`](crate::vmstate_unused) and
//! [`vmstate_of!`](crate::vmstate_of), which are used to express the
//! migration format for a struct. This is based on the [`VMState`] trait,
//! which is defined by all migrateable types.
//!
+//! * [`impl_vmstate_forward`](crate::impl_vmstate_forward) and
+//! [`impl_vmstate_bitsized`](crate::impl_vmstate_bitsized), which help with
+//! the definition of the [`VMState`] trait (respectively for transparent
+//! structs and for `bilge`-defined types)
+//!
//! * helper macros to declare a device model state struct, in particular
//! [`vmstate_subsections`](crate::vmstate_subsections) and
//! [`vmstate_fields`](crate::vmstate_fields).
@@ -134,7 +139,9 @@ macro_rules! info_enum_to_ref {
/// # Safety
///
/// The contents of this trait go straight into structs that are parsed by C
-/// code and used to introspect into other structs. Be careful.
+/// code and used to introspect into other structs. Generally, you don't need
+/// to implement it except via macros that do it for you, such as
+/// `impl_vmstate_bitsized!`.
pub unsafe trait VMState {
/// The `info` member of a `VMStateField` is a pointer and as such cannot
/// yet be included in the [`BASE`](VMState::BASE) associated constant;
@@ -188,7 +195,9 @@ pub const fn vmstate_varray_flag<T: VMState>(_:
PhantomData<T>) -> VMStateFlags
/// * an array of any of the above
///
/// In order to support other types, the trait `VMState` must be implemented
-/// for them.
+/// for them. The macros
+/// [`impl_vmstate_bitsized!`](crate::impl_vmstate_bitsized)
+/// and [`impl_vmstate_forward!`](crate::impl_vmstate_forward) help with this.
#[macro_export]
macro_rules! vmstate_of {
($struct_name:ty, $field_name:ident $([0 .. $num:ident $(*
$factor:expr)?])? $(,)?) => {
@@ -276,6 +285,32 @@ pub const fn with_varray_multiply(mut self, num: u32) ->
VMStateField {
}
}
+/// This macro can be used (by just passing it a type) to forward the `VMState`
+/// trait to the first field of a tuple. This is a workaround for lack of
+/// support of nested [`offset_of`](core::mem::offset_of) until Rust 1.82.0.
+///
+/// # Examples
+///
+/// ```
+/// # use qemu_api::vmstate::impl_vmstate_forward;
+/// pub struct Fifo([u8; 16]);
+/// impl_vmstate_forward!(Fifo);
+/// ```
+#[macro_export]
+macro_rules! impl_vmstate_forward {
+ // This is similar to impl_vmstate_transparent below, but it
+ // uses the same trick as vmstate_of! to obtain the type of
+ // the first field of the tuple
+ ($tuple:ty) => {
+ unsafe impl $crate::vmstate::VMState for $tuple {
+ const SCALAR_TYPE: $crate::vmstate::VMStateFieldType =
+
$crate::call_func_with_field!($crate::vmstate::vmstate_scalar_type, $tuple, 0);
+ const BASE: $crate::bindings::VMStateField =
+ $crate::call_func_with_field!($crate::vmstate::vmstate_base,
$tuple, 0);
+ }
+ };
+}
+
// Transparent wrappers: just use the internal type
macro_rules! impl_vmstate_transparent {
@@ -296,6 +331,26 @@ unsafe impl<$base> VMState for $type where $base: VMState
$($where)* {
impl_vmstate_transparent!(crate::cell::BqlCell<T> where T: VMState);
impl_vmstate_transparent!(crate::cell::BqlRefCell<T> where T: VMState);
+#[macro_export]
+macro_rules! impl_vmstate_bitsized {
+ ($type:ty) => {
+ unsafe impl $crate::vmstate::VMState for $type {
+ const SCALAR_TYPE: $crate::vmstate::VMStateFieldType =
+ <<<$type as
::bilge::prelude::Bitsized>::ArbitraryInt
+ as
::bilge::prelude::Number>::UnderlyingType
+ as
$crate::vmstate::VMState>::SCALAR_TYPE;
+ const BASE: $crate::bindings::VMStateField =
+ <<<$type as
::bilge::prelude::Bitsized>::ArbitraryInt
+ as
::bilge::prelude::Number>::UnderlyingType
+ as $crate::vmstate::VMState>::BASE;
+ const VARRAY_FLAG: $crate::bindings::VMStateFlags =
+ <<<$type as
::bilge::prelude::Bitsized>::ArbitraryInt
+ as
::bilge::prelude::Number>::UnderlyingType
+ as
$crate::vmstate::VMState>::VARRAY_FLAG;
+ }
+ };
+}
+
// Scalar types using predefined VMStateInfos
macro_rules! impl_vmstate_scalar {
--
2.48.1
