The common superclass for devices could have its own migration state;
for it to be included in the subclass's VMState, ParentField<> must
implement the VMState trait.

Reported-by: Chen Miao <chenmiao@openatom.club>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 roms/opensbi                  | 2 +-
 rust/migration/src/vmstate.rs | 3 ++-
 rust/qom/src/qom.rs           | 3 ++-
 3 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/roms/opensbi b/roms/opensbi
index a32a9106911..43cace6c367 160000
--- a/roms/opensbi
+++ b/roms/opensbi
@@ -1 +1 @@
-Subproject commit a32a91069119e7a5aa31e6bc51d5e00860be3d80
+Subproject commit 43cace6c3671e5172d0df0a8963e552bb04b7b20
diff --git a/rust/migration/src/vmstate.rs b/rust/migration/src/vmstate.rs
index 42e5df8d818..5a237c409ac 100644
--- a/rust/migration/src/vmstate.rs
+++ b/rust/migration/src/vmstate.rs
@@ -268,7 +268,7 @@ macro_rules! impl_vmstate_transparent {
     ($type:ty where $base:tt: VMState $($where:tt)*) => {
         unsafe impl<$base> $crate::vmstate::VMState for $type where $base: $crate::vmstate::VMState $($where)* {
             const BASE: $crate::vmstate::VMStateField = $crate::vmstate::VMStateField {
-                size: mem::size_of::<$type>(),
+                size: ::core::mem::size_of::<$type>(),
                 ..<$base as $crate::vmstate::VMState>::BASE
             };
             const VARRAY_FLAG: $crate::bindings::VMStateFlags = <$base as $crate::vmstate::VMState>::VARRAY_FLAG;
@@ -282,6 +282,7 @@ unsafe impl<$base> $crate::vmstate::VMState for $type where $base: $crate::vmsta
 impl_vmstate_transparent!(std::cell::UnsafeCell<T> where T: VMState);
 impl_vmstate_transparent!(std::pin::Pin<T> where T: VMState);
 impl_vmstate_transparent!(common::Opaque<T> where T: VMState);
+impl_vmstate_transparent!(std::mem::ManuallyDrop<T> where T: VMState);
 
 #[macro_export]
 macro_rules! impl_vmstate_bitsized {
diff --git a/rust/qom/src/qom.rs b/rust/qom/src/qom.rs
index 5808051cd77..84455cea79b 100644
--- a/rust/qom/src/qom.rs
+++ b/rust/qom/src/qom.rs
@@ -102,7 +102,7 @@
 };
 
 use common::Opaque;
-use migration::impl_vmstate_pointer;
+use migration::{impl_vmstate_pointer, impl_vmstate_transparent};
 
 use crate::bindings::{
     self, object_class_dynamic_cast, object_dynamic_cast, object_get_class, object_get_typename,
@@ -182,6 +182,7 @@ fn as_ref(&self) -> &$parent {
 #[derive(Debug)]
 #[repr(transparent)]
 pub struct ParentField<T: ObjectType>(std::mem::ManuallyDrop<T>);
+impl_vmstate_transparent!(ParentField<T> where T: VMState + ObjectType);
 
 impl<T: ObjectType> Deref for ParentField<T> {
     type Target = T;
-- 
2.51.1

On Tue, Oct 28, 2025 at 12:38:21PM +0100, Paolo Bonzini wrote:
> Date: Tue, 28 Oct 2025 12:38:21 +0100
> From: Paolo Bonzini <pbonzini@redhat.com>
> Subject: [PATCH] rust: migration: allow passing ParentField<> to vmstate_of!
> X-Mailer: git-send-email 2.51.1
> 
> The common superclass for devices could have its own migration state;
> for it to be included in the subclass's VMState, ParentField<> must
> implement the VMState trait.
> 
> Reported-by: Chen Miao <chenmiao@openatom.club>
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> ---
>  roms/opensbi                  | 2 +-
>  rust/migration/src/vmstate.rs | 3 ++-
>  rust/qom/src/qom.rs           | 3 ++-
>  3 files changed, 5 insertions(+), 3 deletions(-)
> 
> diff --git a/roms/opensbi b/roms/opensbi
> index a32a9106911..43cace6c367 160000
> --- a/roms/opensbi
> +++ b/roms/opensbi
> @@ -1 +1 @@
> -Subproject commit a32a91069119e7a5aa31e6bc51d5e00860be3d80
> +Subproject commit 43cace6c3671e5172d0df0a8963e552bb04b7b20

nit: rebase error?

Others,

Reviewed-by: Zhao Liu <zhao1.liu@intel.com>