On 9/25/25 14:35, Zhao Liu wrote:
+/// #[derive(ToMigrationState)]
/// pub struct DeviceRegs {
/// status: u32,
/// }
+/// # unsafe impl VMState for DeviceRegsMigration {
+/// # const BASE: VMStateField = ::common::Zeroable::ZERO;
+/// # }
Outdated comment? Looks like the DeviceRegsMigration definition is
missing.
It's defined by the #[derive(ToMigrationState)].
the below conversion is ugly:>
#[property(rename = "msi", bit = HPET_FLAG_MSI_SUPPORT_SHIFT as u8, default =
false)]
conversion should happen within the macro parsing process. But unfortunately,
try_into() is not const, maybe I could do this for bit property:
diff --git a/rust/qemu-macros/src/lib.rs b/rust/qemu-macros/src/lib.rs
index c459f9bcb42f..e67df57c3712 100644
--- a/rust/qemu-macros/src/lib.rs
+++ b/rust/qemu-macros/src/lib.rs
@@ -275,7 +275,10 @@ macro_rules! str_to_c_str {
name: ::std::ffi::CStr::as_ptr(#prop_name),
info: #qdev_prop,
offset: ::core::mem::offset_of!(#name, #field_name) as isize,
- bitnr: #bitnr,
+ bitnr: {
+ const _: () = assert!(#bitnr <= u8::MAX as _, "bit exceeds u8
range");
+ #bitnr as u8
+ },
set_default: #set_default,
defval: ::hwcore::bindings::Property__bindgen_ty_1 { u:
#defval as u64 },
..::common::Zeroable::ZERO
Good idea (also testing >= 0 is needed). "const { assert!(...); }" is
even simpler.
+/// - `#[migration_state(clone)]` - Clones the field value.
How about emphasizing the use case?
"Clones the field value, especially for the types don't implement `Copy`."
I don't have a use case yet to be honest, but at the same time I want to
help potential device authors and remove the need to muck with the macro.
+/// Fields without any attributes use `ToMigrationState` recursively; note that
+/// this is a simple copy for types that implement `Copy`.
+///
+/// # Attribute compatibility
+///
+/// - `omit` cannot be used with any other attributes
+/// - only one of `into(Type)`, `try_into(Type)` can be used, but they can be
+/// coupled with `clone`.
+///
...
The implementation of the entire macro is great.
Thanks. :) It's indeed pretty easy to follow, and I like procedural
macro code that is simple but powerful.
The attrs crate also helps a lot!
+#[test]
+fn test_derive_to_migration_state() {
...
+ quote! {
+ #[derive(Default)]
+ pub struct CustomMigration {
+ pub shared_data: String,
+ pub converted_field: Cow<'static, str>,
+ pub fallible_field: i8,
+ pub nested_field: <NestedStruct as ToMigrationState>::Migrated,
+ pub simple_field: <u32 as ToMigrationState>::Migrated,
+ }
In the production code, CustomMigration still needs to implement VMState
trait, so that String & Cow<'static, str> also need to implement VMState
trait. This seems like the thing that we are currently missing.
Or more simply they're not chosen well. :) For the documentation I will
think of better types.
For test, it's enough to show how the macro works.
Yes, for testing it's a lesser deal.
Paolo
