Merge tag 'for-upstream' of https://gitlab.com/bonzini/qemu into stagingHEADstagingmaster

* cleanups for distributed DTB files
* scripts/meson-buildoptions: Sort coroutine_backend choices lexicographically
* rust/qemu-api: Add initial logging support
: rust: pl011: Implement logging
* target/i386: fix Win98
* meson: cleanup win32 library detection
* rust: safe(r) instance_init
* rust: prepare for multiple bindgen invocations
* rust: fix new warning
* target/i386: Warn about why CPUID_EXT_PDCM is not available
* target/i386: small TDX fixes and clarifications
* target/i386: support for TDX quote generation

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# gpg:                using RSA key F13338574B662389866C7682BFFBD25F78C7AE83
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# gpg:                 aka "Paolo Bonzini <pbonzini@redhat.com>" [full]
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* tag 'for-upstream' of https://gitlab.com/bonzini/qemu: (24 commits)
  i386/tdx: handle TDG.VP.VMCALL<GetQuote>
  i386/tdx: handle TDG.VP.VMCALL<GetTdVmCallInfo>
  update Linux headers to v6.16-rc3
  i386/tdx: Clarify the error message of mrconfigid/mrowner/mrownerconfig
  i386/tdx: Fix the typo of the comment of struct TdxGuest
  i386/cpu: Rename enable_cpuid_0x1f to force_cpuid_0x1f
  i386/tdx: Error and exit when named cpu model is requested
  i386/cpu: Warn about why CPUID_EXT_PDCM is not available
  i386/cpu: Move adjustment of CPUID_EXT_PDCM before feature_dependencies[] check
  rust: hpet: fix new warning
  rust: pl011: Add missing logging to match C version
  rust: pl011: Implement logging
  rust/qemu-api: Add initial logging support based on C API
  rust: move rust.bindgen to qemu-api crate
  rust: prepare variable definitions for multiple bindgen invocations
  rust: qom: change instance_init to take a ParentInit<>
  rust: qom: make ParentInit lifetime-invariant
  rust: qom: introduce ParentInit
  rust: hpet: fully initialize object during instance_init
  rust: qemu_api: introduce MaybeUninit field projection
  ...

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

1 files changed, 85 insertions, 0 deletions

diff --git a/rust/qemu-api/src/uninit.rs b/rust/qemu-api/src/uninit.rs
new file mode 100644
index 0000000..04123b4
--- /dev/null
+++ b/rust/qemu-api/src/uninit.rs
@@ -0,0 +1,85 @@
+//! Access fields of a [`MaybeUninit`]
+
+use std::{
+    mem::MaybeUninit,
+    ops::{Deref, DerefMut},
+};
+
+pub struct MaybeUninitField<'a, T, U> {
+    parent: &'a mut MaybeUninit<T>,
+    child: *mut U,
+}
+
+impl<'a, T, U> MaybeUninitField<'a, T, U> {
+    #[doc(hidden)]
+    pub fn new(parent: &'a mut MaybeUninit<T>, child: *mut U) -> Self {
+        MaybeUninitField { parent, child }
+    }
+
+    /// Return a constant pointer to the containing object of the field.
+    ///
+    /// Because the `MaybeUninitField` remembers the containing object,
+    /// it is possible to use it in foreign APIs that initialize the
+    /// child.
+    pub fn parent(f: &Self) -> *const T {
+        f.parent.as_ptr()
+    }
+
+    /// Return a mutable pointer to the containing object.
+    ///
+    /// Because the `MaybeUninitField` remembers the containing object,
+    /// it is possible to use it in foreign APIs that initialize the
+    /// child.
+    pub fn parent_mut(f: &mut Self) -> *mut T {
+        f.parent.as_mut_ptr()
+    }
+}
+
+impl<'a, T, U> Deref for MaybeUninitField<'a, T, U> {
+    type Target = MaybeUninit<U>;
+
+    fn deref(&self) -> &MaybeUninit<U> {
+        // SAFETY: self.child was obtained by dereferencing a valid mutable
+        // reference; the content of the memory may be invalid or uninitialized
+        // but MaybeUninit<_> makes no assumption on it
+        unsafe { &*(self.child.cast()) }
+    }
+}
+
+impl<'a, T, U> DerefMut for MaybeUninitField<'a, T, U> {
+    fn deref_mut(&mut self) -> &mut MaybeUninit<U> {
+        // SAFETY: self.child was obtained by dereferencing a valid mutable
+        // reference; the content of the memory may be invalid or uninitialized
+        // but MaybeUninit<_> makes no assumption on it
+        unsafe { &mut *(self.child.cast()) }
+    }
+}
+
+/// ```
+/// #[derive(Debug)]
+/// struct S {
+///     x: u32,
+///     y: u32,
+/// }
+///
+/// # use std::mem::MaybeUninit;
+/// # use qemu_api::{assert_match, uninit_field_mut};
+///
+/// let mut s: MaybeUninit<S> = MaybeUninit::zeroed();
+/// uninit_field_mut!(s, x).write(5);
+/// let s = unsafe { s.assume_init() };
+/// assert_match!(s, S { x: 5, y: 0 });
+/// ```
+#[macro_export]
+macro_rules! uninit_field_mut {
+    ($container:expr, $($field:tt)+) => {{
+        let container__: &mut ::std::mem::MaybeUninit<_> = &mut $container;
+        let container_ptr__ = container__.as_mut_ptr();
+
+        // SAFETY: the container is not used directly, only through a MaybeUninit<>,
+        // so the safety is delegated to the caller and to final invocation of
+        // assume_init()
+        let target__ = unsafe { std::ptr::addr_of_mut!((*container_ptr__).$($field)+) };
+        $crate::uninit::MaybeUninitField::new(container__, target__)
+    }};
+}