Re: [PATCH 07/11] rust: migration: add high-level migration wrappers

[Zhao Liu <zhao1.liu@intel.com>]

On Wed, Oct 01, 2025 at 09:52:06AM +0200, Paolo Bonzini wrote:
> Date: Wed,  1 Oct 2025 09:52:06 +0200
> From: Paolo Bonzini <pbonzini@redhat.com>
> Subject: [PATCH 07/11] rust: migration: add high-level migration wrappers
> X-Mailer: git-send-email 2.51.0
> 
> Instead of dealing with pre/post callbacks, allow devices to
> implement a snapshot/restore mechanism; this has two main
> advantages:
> 
> - it can be easily implemented via procedural macros
> 
> - there can be generic implementations to deal with various
>   kinds of interior-mutable containers, from BqlRefCell to Mutex,
>   so that C code does not see Rust concepts such as Mutex<>.
> 
> Using it is easy; you can implement the snapshot/restore trait
> ToMigrationState and declare your state like:
> 
>      regs: Migratable<Mutex<MyDeviceRegisters>>
> 
> Migratable<> allows dereferencing to the underlying object with
> no run-time cost.
> 
> Note that Migratable<> actually does not accept ToMigrationState,
> only the similar ToMigrationStateShared trait that the user will mostly
> not care about.  This is required by the fact that pre/post callbacks
> take a &self, and ensures that the argument is a Mutex or BqlRefCell
> (including an array or Arc<> thereof).
> 
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> ---
>  docs/devel/rust.rst              |   1 +
>  rust/migration/meson.build       |   1 +
>  rust/migration/src/lib.rs        |   3 +
>  rust/migration/src/migratable.rs | 434 +++++++++++++++++++++++++++++++
>  4 files changed, 439 insertions(+)
>  create mode 100644 rust/migration/src/migratable.rs

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