From: Zhao Liu <zhao1....@intel.com> Unfortunately, at present it's not possible to have a const "with_exist_check" method to append test_fn after vmstate_struct (due to error on "constant functions cannot evaluate destructors" for `F`).
Before the vmstate builder, the only way to support "test_fn" is to extend vmstate_struct macro to add the such new optional member (and fortunately, Rust can still parse the current expansion!). Abstract the previous callback implementation of vmstate_validate into a separate macro, and moves it before vmstate_struct for vmstate_struct to call. Note that there's no need to add any extra flag for a new test_fn added in the VMStateField. Signed-off-by: Zhao Liu <zhao1....@intel.com> Link: https://lore.kernel.org/r/20250414144943.1112885-2-zhao1....@intel.com Signed-off-by: Paolo Bonzini <pbonz...@redhat.com> --- rust/qemu-api/src/vmstate.rs | 70 +++++++++++++++++++----------------- 1 file changed, 37 insertions(+), 33 deletions(-) diff --git a/rust/qemu-api/src/vmstate.rs b/rust/qemu-api/src/vmstate.rs index 1b2b12eadd6..8c4a5bee3c1 100644 --- a/rust/qemu-api/src/vmstate.rs +++ b/rust/qemu-api/src/vmstate.rs @@ -200,13 +200,14 @@ pub const fn vmstate_varray_flag<T: VMState>(_: PhantomData<T>) -> VMStateFlags /// and [`impl_vmstate_forward!`](crate::impl_vmstate_forward) help with this. #[macro_export] macro_rules! vmstate_of { - ($struct_name:ty, $field_name:ident $([0 .. $num:ident $(* $factor:expr)?])? $(,)?) => { + ($struct_name:ty, $field_name:ident $([0 .. $num:ident $(* $factor:expr)?])? $(, $test_fn:expr)? $(,)?) => { $crate::bindings::VMStateField { name: ::core::concat!(::core::stringify!($field_name), "\0") .as_bytes() .as_ptr() as *const ::std::os::raw::c_char, offset: $crate::offset_of!($struct_name, $field_name), $(num_offset: $crate::offset_of!($struct_name, $num),)? + $(field_exists: $crate::vmstate_exist_fn!($struct_name, $test_fn),)? // The calls to `call_func_with_field!` are the magic that // computes most of the VMStateField from the type of the field. info: $crate::info_enum_to_ref!($crate::call_func_with_field!( @@ -435,6 +436,38 @@ macro_rules! vmstate_unused { }}; } +pub extern "C" fn rust_vms_test_field_exists<T, F: for<'a> FnCall<(&'a T, u8), bool>>( + opaque: *mut c_void, + version_id: c_int, +) -> bool { + // SAFETY: the opaque was passed as a reference to `T`. + let owner: &T = unsafe { &*(opaque.cast::<T>()) }; + let version: u8 = version_id.try_into().unwrap(); + F::call((owner, version)) +} + +pub type VMSFieldExistCb = unsafe extern "C" fn( + opaque: *mut std::os::raw::c_void, + version_id: std::os::raw::c_int, +) -> bool; + +#[macro_export] +macro_rules! vmstate_exist_fn { + ($struct_name:ty, $test_fn:expr) => {{ + const fn test_cb_builder__<T, F: for<'a> $crate::callbacks::FnCall<(&'a T, u8), bool>>( + _phantom: ::core::marker::PhantomData<F>, + ) -> $crate::vmstate::VMSFieldExistCb { + let _: () = F::ASSERT_IS_SOME; + $crate::vmstate::rust_vms_test_field_exists::<T, F> + } + + const fn phantom__<T>(_: &T) -> ::core::marker::PhantomData<T> { + ::core::marker::PhantomData + } + Some(test_cb_builder__::<$struct_name, _>(phantom__(&$test_fn))) + }}; +} + // FIXME: including the `vmsd` field in a `const` is not possible without // the const_refs_static feature (stabilized in Rust 1.83.0). Without it, // it is not possible to use VMS_STRUCT in a transparent manner using @@ -445,7 +478,7 @@ macro_rules! vmstate_unused { #[doc(alias = "VMSTATE_STRUCT")] #[macro_export] macro_rules! vmstate_struct { - ($struct_name:ty, $field_name:ident $([0 .. $num:ident $(* $factor:expr)?])?, $vmsd:expr, $type:ty $(,)?) => { + ($struct_name:ty, $field_name:ident $([0 .. $num:ident $(* $factor:expr)?])?, $vmsd:expr, $type:ty $(, $test_fn:expr)? $(,)?) => { $crate::bindings::VMStateField { name: ::core::concat!(::core::stringify!($field_name), "\0") .as_bytes() @@ -458,6 +491,7 @@ macro_rules! vmstate_struct { size: ::core::mem::size_of::<$type>(), flags: $crate::bindings::VMStateFlags::VMS_STRUCT, vmsd: $vmsd, + $(field_exists: $crate::vmstate_exist_fn!($struct_name, $test_fn),)? ..$crate::zeroable::Zeroable::ZERO } $(.with_varray_flag_unchecked( $crate::call_func_with_field!( @@ -514,43 +548,13 @@ macro_rules! vmstate_fields { }} } -pub extern "C" fn rust_vms_test_field_exists<T, F: for<'a> FnCall<(&'a T, u8), bool>>( - opaque: *mut c_void, - version_id: c_int, -) -> bool { - let owner: &T = unsafe { &*(opaque.cast::<T>()) }; - let version: u8 = version_id.try_into().unwrap(); - // SAFETY: the opaque was passed as a reference to `T`. - F::call((owner, version)) -} - -pub type VMSFieldExistCb = unsafe extern "C" fn( - opaque: *mut std::os::raw::c_void, - version_id: std::os::raw::c_int, -) -> bool; - #[doc(alias = "VMSTATE_VALIDATE")] #[macro_export] macro_rules! vmstate_validate { ($struct_name:ty, $test_name:expr, $test_fn:expr $(,)?) => { $crate::bindings::VMStateField { name: ::std::ffi::CStr::as_ptr($test_name), - field_exists: { - const fn test_cb_builder__< - T, - F: for<'a> $crate::callbacks::FnCall<(&'a T, u8), bool>, - >( - _phantom: ::core::marker::PhantomData<F>, - ) -> $crate::vmstate::VMSFieldExistCb { - let _: () = F::ASSERT_IS_SOME; - $crate::vmstate::rust_vms_test_field_exists::<T, F> - } - - const fn phantom__<T>(_: &T) -> ::core::marker::PhantomData<T> { - ::core::marker::PhantomData - } - Some(test_cb_builder__::<$struct_name, _>(phantom__(&$test_fn))) - }, + field_exists: $crate::vmstate_exist_fn!($struct_name, $test_fn), flags: $crate::bindings::VMStateFlags( $crate::bindings::VMStateFlags::VMS_MUST_EXIST.0 | $crate::bindings::VMStateFlags::VMS_ARRAY.0, -- 2.49.0
