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helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -50 X-Spam_score: -5.1 X-Spam_bar: ----- X-Spam_report: (-5.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-2.996, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=-0.043, RCVD_IN_VALIDITY_CERTIFIED_BLOCKED=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Scalar types are those that have their own VMStateInfo. This poses a problem in that references to VMStateInfo can only be included in associated consts starting with Rust 1.83.0, when the const_refs_static was stabilized. Removing the requirement is done by placing a limited list of VMStateInfos in an enum, and going from enum to &VMStateInfo only when building the VMStateField. The same thing cannot be done with VMS_STRUCT because the set of VMStateDescriptions extends to structs defined by the devices. Therefore, structs and cells cannot yet use vmstate_of!. Signed-off-by: Paolo Bonzini --- rust/qemu-api/src/vmstate.rs | 128 ++++++++++++++++++++++++++++++++++- 1 file changed, 126 insertions(+), 2 deletions(-) diff --git a/rust/qemu-api/src/vmstate.rs b/rust/qemu-api/src/vmstate.rs index 7652930affc..a262c315da1 100644 --- a/rust/qemu-api/src/vmstate.rs +++ b/rust/qemu-api/src/vmstate.rs @@ -22,7 +22,10 @@ use core::{marker::PhantomData, mem, ptr::NonNull}; pub use crate::bindings::{VMStateDescription, VMStateField}; -use crate::bindings::VMStateFlags; +use crate::{ + bindings::{self, VMStateFlags}, + zeroable::Zeroable, +}; /// This macro is used to call a function with a generic argument bound /// to the type of a field. The function must take a @@ -61,6 +64,70 @@ const fn phantom__(_: &T) -> ::core::marker::PhantomData { ::core::marker: }; } +/// Workaround for lack of `const_refs_static`: references to global variables +/// can be included in a `static`, but not in a `const`; unfortunately, this +/// is exactly what would go in the `VMStateField`'s `info` member. +/// +/// This enum contains the contents of the `VMStateField`'s `info` member, +/// but as an `enum` instead of a pointer. +#[allow(non_camel_case_types)] +pub enum VMStateFieldType { + null, + vmstate_info_bool, + vmstate_info_int8, + vmstate_info_int16, + vmstate_info_int32, + vmstate_info_int64, + vmstate_info_uint8, + vmstate_info_uint16, + vmstate_info_uint32, + vmstate_info_uint64, + vmstate_info_timer, +} + +/// Workaround for lack of `const_refs_static`. Converts a `VMStateFieldType` +/// to a `*const VMStateInfo`, for inclusion in a `VMStateField`. +#[macro_export] +macro_rules! info_enum_to_ref { + ($e:expr) => { + unsafe { + match $e { + $crate::vmstate::VMStateFieldType::null => ::core::ptr::null(), + $crate::vmstate::VMStateFieldType::vmstate_info_bool => { + ::core::ptr::addr_of!($crate::bindings::vmstate_info_bool) + } + $crate::vmstate::VMStateFieldType::vmstate_info_int8 => { + ::core::ptr::addr_of!($crate::bindings::vmstate_info_int8) + } + $crate::vmstate::VMStateFieldType::vmstate_info_int16 => { + ::core::ptr::addr_of!($crate::bindings::vmstate_info_int16) + } + $crate::vmstate::VMStateFieldType::vmstate_info_int32 => { + ::core::ptr::addr_of!($crate::bindings::vmstate_info_int32) + } + $crate::vmstate::VMStateFieldType::vmstate_info_int64 => { + ::core::ptr::addr_of!($crate::bindings::vmstate_info_int64) + } + $crate::vmstate::VMStateFieldType::vmstate_info_uint8 => { + ::core::ptr::addr_of!($crate::bindings::vmstate_info_uint8) + } + $crate::vmstate::VMStateFieldType::vmstate_info_uint16 => { + ::core::ptr::addr_of!($crate::bindings::vmstate_info_uint16) + } + $crate::vmstate::VMStateFieldType::vmstate_info_uint32 => { + ::core::ptr::addr_of!($crate::bindings::vmstate_info_uint32) + } + $crate::vmstate::VMStateFieldType::vmstate_info_uint64 => { + ::core::ptr::addr_of!($crate::bindings::vmstate_info_uint64) + } + $crate::vmstate::VMStateFieldType::vmstate_info_timer => { + ::core::ptr::addr_of!($crate::bindings::vmstate_info_timer) + } + } + } + }; +} + /// A trait for types that can be included in a device's migration stream. It /// provides the base contents of a `VMStateField` (minus the name and offset). /// @@ -69,6 +136,12 @@ const fn phantom__(_: &T) -> ::core::marker::PhantomData { ::core::marker: /// The contents of this trait go straight into structs that are parsed by C /// code and used to introspect into other structs. Be careful. pub unsafe trait VMState { + /// The `info` member of a `VMStateField` is a pointer and as such cannot + /// yet be included in the [`BASE`](VMState::BASE) associated constant; + /// this is only allowed by Rust 1.83.0 and newer. For now, include the + /// member as an enum which is stored in a separate constant. + const SCALAR_TYPE: VMStateFieldType = VMStateFieldType::null; + /// The base contents of a `VMStateField` (minus the name and offset) for /// the type that is implementing the trait. const BASE: VMStateField; @@ -83,6 +156,12 @@ pub unsafe trait VMState { }; } +/// Internal utility function to retrieve a type's `VMStateFieldType`; +/// used by [`vmstate_of!`](crate::vmstate_of). +pub const fn vmstate_scalar_type(_: PhantomData) -> VMStateFieldType { + T::SCALAR_TYPE +} + /// Internal utility function to retrieve a type's `VMStateField`; /// used by [`vmstate_of!`](crate::vmstate_of). pub const fn vmstate_base(_: PhantomData) -> VMStateField { @@ -99,6 +178,15 @@ pub const fn vmstate_varray_flag(_: PhantomData) -> VMStateFlags /// Return the `VMStateField` for a field of a struct. The field must be /// visible in the current scope. /// +/// Only a limited set of types is supported out of the box: +/// * scalar types (integer and `bool`) +/// * the C struct `QEMUTimer` +/// * a transparent wrapper for any of the above (`Cell`, `UnsafeCell`, +/// [`BqlCell`](crate::cell::BqlCell), [`BqlRefCell`](crate::cell::BqlRefCell) +/// * a raw pointer to any of the above +/// * a `NonNull` pointer or a `Box` for any of the above +/// * an array of any of the above +/// /// In order to support other types, the trait `VMState` must be implemented /// for them. #[macro_export] @@ -109,8 +197,14 @@ macro_rules! vmstate_of { .as_bytes() .as_ptr() as *const ::std::os::raw::c_char, offset: $crate::offset_of!($struct_name, $field_name), - // Compute most of the VMStateField from the type of the field. $(.num_offset: $crate::offset_of!($struct_name, $num),)? + // 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!( + $crate::vmstate::vmstate_scalar_type, + $struct_name, + $field_name + )), ..$crate::call_func_with_field!( $crate::vmstate::vmstate_base, $struct_name, @@ -187,6 +281,7 @@ pub const fn with_varray_multiply(mut self, num: u32) -> VMStateField { macro_rules! impl_vmstate_transparent { ($type:ty where $base:tt: VMState $($where:tt)*) => { unsafe impl<$base> VMState for $type where $base: VMState $($where)* { + const SCALAR_TYPE: VMStateFieldType = <$base as VMState>::SCALAR_TYPE; const BASE: VMStateField = VMStateField { size: mem::size_of::<$type>(), ..<$base as VMState>::BASE @@ -201,6 +296,33 @@ unsafe impl<$base> VMState for $type where $base: VMState $($where)* { impl_vmstate_transparent!(crate::cell::BqlCell where T: VMState); impl_vmstate_transparent!(crate::cell::BqlRefCell where T: VMState); +// Scalar types using predefined VMStateInfos + +macro_rules! impl_vmstate_scalar { + ($info:ident, $type:ty$(, $varray_flag:ident)?) => { + unsafe impl VMState for $type { + const SCALAR_TYPE: VMStateFieldType = VMStateFieldType::$info; + const BASE: VMStateField = VMStateField { + size: mem::size_of::<$type>(), + flags: VMStateFlags::VMS_SINGLE, + ..Zeroable::ZERO + }; + $(const VARRAY_FLAG: VMStateFlags = VMStateFlags::$varray_flag;)? + } + }; +} + +impl_vmstate_scalar!(vmstate_info_bool, bool); +impl_vmstate_scalar!(vmstate_info_int8, i8); +impl_vmstate_scalar!(vmstate_info_int16, i16); +impl_vmstate_scalar!(vmstate_info_int32, i32); +impl_vmstate_scalar!(vmstate_info_int64, i64); +impl_vmstate_scalar!(vmstate_info_uint8, u8, VMS_VARRAY_UINT8); +impl_vmstate_scalar!(vmstate_info_uint16, u16, VMS_VARRAY_UINT16); +impl_vmstate_scalar!(vmstate_info_uint32, u32, VMS_VARRAY_UINT32); +impl_vmstate_scalar!(vmstate_info_uint64, u64); +impl_vmstate_scalar!(vmstate_info_timer, bindings::QEMUTimer); + // Pointer types using the underlying type's VMState plus VMS_POINTER // Note that references are not supported, though references to cells // could be allowed. @@ -208,6 +330,7 @@ unsafe impl<$base> VMState for $type where $base: VMState $($where)* { macro_rules! impl_vmstate_pointer { ($type:ty where $base:tt: VMState $($where:tt)*) => { unsafe impl<$base> VMState for $type where $base: VMState $($where)* { + const SCALAR_TYPE: VMStateFieldType = ::SCALAR_TYPE; const BASE: VMStateField = <$base as VMState>::BASE.with_pointer_flag(); } }; @@ -225,6 +348,7 @@ unsafe impl<$base> VMState for $type where $base: VMState $($where)* { // VMS_ARRAY/VMS_ARRAY_OF_POINTER unsafe impl VMState for [T; N] { + const SCALAR_TYPE: VMStateFieldType = ::SCALAR_TYPE; const BASE: VMStateField = ::BASE.with_array_flag(N); }