Re: [RFC 07/18] rust: move Cell vmstate impl

[Paolo Bonzini <pbonzini@redhat.com>]

On 8/26/25 16:04, marcandre.lureau@redhat.com wrote:
> From: Marc-André Lureau <marcandre.lureau@redhat.com>
> 
> This will allow to split vmstate to a standalone crate next.

Can you explain why this is needed?  Could "migration" depend on "bql" 
(or even, "bql" could stay in util), and keep the implementation of 
VMState for cells, just like you do for Opaque?

Thanks,

Paolo

> Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
> ---
>   rust/qemu-api/src/cell.rs    |  5 ++++-
>   rust/qemu-api/src/vmstate.rs | 16 +++++++---------
>   2 files changed, 11 insertions(+), 10 deletions(-)
> 
> diff --git a/rust/qemu-api/src/cell.rs b/rust/qemu-api/src/cell.rs
> index 98d720caf9..4bce526e45 100644
> --- a/rust/qemu-api/src/cell.rs
> +++ b/rust/qemu-api/src/cell.rs
> @@ -152,7 +152,7 @@
>       ptr::NonNull,
>   };
>   
> -use crate::bindings;
> +use crate::{bindings, impl_vmstate_transparent};
>   
>   /// An internal function that is used by doctests.
>   pub fn bql_start_test() {
> @@ -866,3 +866,6 @@ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
>           (**self).fmt(f)
>       }
>   }
> +
> +impl_vmstate_transparent!(BqlCell<T> where T: VMState);
> +impl_vmstate_transparent!(BqlRefCell<T> where T: VMState);
> diff --git a/rust/qemu-api/src/vmstate.rs b/rust/qemu-api/src/vmstate.rs
> index c1e2b06390..9d33997c57 100644
> --- a/rust/qemu-api/src/vmstate.rs
> +++ b/rust/qemu-api/src/vmstate.rs
> @@ -29,8 +29,7 @@
>   
>   use common::{callbacks::FnCall, Zeroable};
>   
> -use crate::bindings::VMStateFlags;
> -pub use crate::bindings::{VMStateDescription, VMStateField};
> +pub use crate::bindings::{VMStateDescription, VMStateField, VMStateFlags};
>   
>   /// This macro is used to call a function with a generic argument bound
>   /// to the type of a field.  The function must take a
> @@ -325,15 +324,16 @@ unsafe impl $crate::vmstate::VMState for $tuple {
>   
>   // Transparent wrappers: just use the internal type
>   
> +#[macro_export]
>   macro_rules! impl_vmstate_transparent {
>       ($type:ty where $base:tt: VMState $($where:tt)*) => {
> -        unsafe impl<$base> VMState for $type where $base: VMState $($where)* {
> -            const SCALAR_TYPE: VMStateFieldType = <$base as VMState>::SCALAR_TYPE;
> -            const BASE: VMStateField = VMStateField {
> +        unsafe impl<$base> $crate::vmstate::VMState for $type where $base: $crate::vmstate::VMState $($where)* {
> +            const SCALAR_TYPE: $crate::vmstate::VMStateFieldType = <$base as $crate::vmstate::VMState>::SCALAR_TYPE;
> +            const BASE: $crate::vmstate::VMStateField = $crate::vmstate::VMStateField {
>                   size: mem::size_of::<$type>(),
> -                ..<$base as VMState>::BASE
> +                ..<$base as $crate::vmstate::VMState>::BASE
>               };
> -            const VARRAY_FLAG: VMStateFlags = <$base as VMState>::VARRAY_FLAG;
> +            const VARRAY_FLAG: $crate::vmstate::VMStateFlags = <$base as $crate::vmstate::VMState>::VARRAY_FLAG;
>           }
>       };
>   }
> @@ -341,8 +341,6 @@ unsafe impl<$base> VMState for $type where $base: VMState $($where)* {
>   impl_vmstate_transparent!(std::cell::Cell<T> where T: VMState);
>   impl_vmstate_transparent!(std::cell::UnsafeCell<T> where T: VMState);
>   impl_vmstate_transparent!(std::pin::Pin<T> where T: VMState);
> -impl_vmstate_transparent!(crate::cell::BqlCell<T> where T: VMState);
> -impl_vmstate_transparent!(crate::cell::BqlRefCell<T> where T: VMState);
>   impl_vmstate_transparent!(::common::Opaque<T> where T: VMState);
>   
>   #[macro_export]