Re: [PATCH 08/11] rust: qemu-macros: add ToMigrationState derive macro

[Paolo Bonzini <pbonzini@redhat.com>]

On 11/3/25 16:49, Zhao Liu wrote:
>> did you miss something like the following?
>>
>>
>> diff --git a/rust/qemu-macros/src/migration_state.rs b/rust/qemu-macros/src/migration_state.rs
>> index 5edf0efe687f..2064bb73a6f0 100644
>> --- a/rust/qemu-macros/src/migration_state.rs
>> +++ b/rust/qemu-macros/src/migration_state.rs
>> @@ -236,6 +236,16 @@ pub struct #name {
>>           }
>>       }
>>
>> +    fn generate_vmstate_impl(&self) -> TokenStream {
>> +        let name = self.migration_state_name();
>> +
>> +        quote! {
>> +            unsafe impl ::migration::VMState for #name {
>> +                const BASE: ::migration::VMStateField = ::common::Zeroable::ZERO;
> 
> It seems the generated migration_state_struct needs a complete VMSD:
> collect all its fields and build a VMSD.
> 
> And then apply impl_vmstate_struct! to this  migration_state_struct.
> 
> If we zero the BASE, then `vmstate_of!(Self, migration_state)` seems
> can't migrate its fields.

The VMStateDescription for the inner struct is indeed missing, but you 
need to write it yourself and apply impl_vmstate_struct, because the 
derive macro cannot know the checks or version_ids for each field, or 
the subsections.

The VMStateDescription for Migratable<> however is automatic (of 
course), and the outer VMStateDescription for the device is simple---it 
consists only of the parent class if applicable, and the Migratable<>, 
similar to VMSTATE_PL011.

For HPET, you'll have to move the subsections from VMSTATE_HPET to the 
inner VMState.

Paolo