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

* cpu-exec: more cleanups to CPU loop exits
* python: bump bundled Meson to 1.9.0
* rust: require Rust 1.83.0
* rust: temporarily remove from Ubuntu CI
* rust: vmstate: convert to use builder pattern
* rust: split "qemu-api" crate
* rust: rename qemu_api_macros -> qemu_macros
* rust: re-export qemu macros from other crates
* x86: fix functional test failure for Xen emulation
* x86: cleanups

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# gpg:                using RSA key F13338574B662389866C7682BFFBD25F78C7AE83
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* tag 'for-upstream' of https://gitlab.com/bonzini/qemu: (60 commits)
  accel/kvm: Set guest_memfd_offset to non-zero value only when guest_memfd is valid
  accel/kvm: Zero out mem explicitly in kvm_set_user_memory_region()
  accel/kvm: Switch to check KVM_CAP_GUEST_MEMFD and KVM_CAP_USER_MEMORY2 on VM
  i386/kvm: Drop KVM_CAP_X86_SMM check in kvm_arch_init()
  multiboot: Fix the split lock
  target/i386: Define enum X86ASIdx for x86's address spaces
  i386/cpu: Enable SMM cpu address space under KVM
  hpet: guard IRQ handling with BQL
  rust: do not inline do_init_io
  rust: meson: remove unnecessary complication in device crates
  docs: update rust.rst
  rust: re-export qemu macros from common/qom/hwcore
  rust: re-export qemu_macros internal helper in "bits"
  rust: repurpose qemu_api -> tests
  rust/pl011: drop dependency on qemu_api
  rust/hpet: drop now unneeded qemu_api dep
  rust: rename qemu_api_macros -> qemu_macros
  rust: split "hwcore" crate
  rust: split "system" crate
  rust: split "chardev" crate
  ...

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

1 files changed, 151 insertions, 0 deletions

diff --git a/rust/util/src/log.rs b/rust/util/src/log.rs
new file mode 100644
index 0000000000..af9a3e9123
--- /dev/null
+++ b/rust/util/src/log.rs
@@ -0,0 +1,151 @@
+// Copyright 2025 Bernhard Beschow <shentey@gmail.com>
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+//! Bindings for QEMU's logging infrastructure
+
+use std::{
+    io::{self, Write},
+    ptr::NonNull,
+};
+
+use common::errno;
+
+use crate::bindings;
+
+#[repr(u32)]
+/// Represents specific error categories within QEMU's logging system.
+///
+/// The `Log` enum provides a Rust abstraction for logging errors, corresponding
+/// to a subset of the error categories defined in the C implementation.
+pub enum Log {
+    /// Log invalid access caused by the guest.
+    /// Corresponds to `LOG_GUEST_ERROR` in the C implementation.
+    GuestError = bindings::LOG_GUEST_ERROR,
+
+    /// Log guest access of unimplemented functionality.
+    /// Corresponds to `LOG_UNIMP` in the C implementation.
+    Unimp = bindings::LOG_UNIMP,
+}
+
+/// A RAII guard for QEMU's logging infrastructure.  Creating the guard
+/// locks the log file, and dropping it (letting it go out of scope) unlocks
+/// the file.
+///
+/// As long as the guard lives, it can be written to using [`std::io::Write`].
+///
+/// The locking is recursive, therefore owning a guard does not prevent
+/// using [`log_mask_ln!()`](crate::log_mask_ln).
+pub struct LogGuard(NonNull<bindings::FILE>);
+
+impl LogGuard {
+    /// Return a RAII guard that writes to QEMU's logging infrastructure.
+    /// The log file is locked while the guard exists, ensuring that there
+    /// is no tearing of the messages.
+    ///
+    /// Return `None` if the log file is closed and could not be opened.
+    /// Do *not* use `unwrap()` on the result; failure can be handled simply
+    /// by not logging anything.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// # use util::log::LogGuard;
+    /// # use std::io::Write;
+    /// if let Some(mut log) = LogGuard::new() {
+    ///     writeln!(log, "test");
+    /// }
+    /// ```
+    pub fn new() -> Option<Self> {
+        let f = unsafe { bindings::qemu_log_trylock() }.cast();
+        NonNull::new(f).map(Self)
+    }
+
+    /// Writes a formatted string into the log, returning any error encountered.
+    ///
+    /// This method is primarily used by the
+    /// [`log_mask_ln!()`](crate::log_mask_ln) macro, and it is rare for it
+    /// to be called explicitly.  It is public because it is the only way to
+    /// examine the error, which `log_mask_ln!()` ignores
+    ///
+    /// Unlike `log_mask_ln!()`, it does *not* append a newline at the end.
+    pub fn log_fmt(args: std::fmt::Arguments) -> io::Result<()> {
+        if let Some(mut log) = Self::new() {
+            log.write_fmt(args)?;
+        }
+        Ok(())
+    }
+}
+
+impl Write for LogGuard {
+    fn write(&mut self, bytes: &[u8]) -> io::Result<usize> {
+        let ret = unsafe {
+            bindings::rust_fwrite(bytes.as_ptr().cast(), 1, bytes.len(), self.0.as_ptr())
+        };
+        errno::into_io_result(ret)
+    }
+
+    fn flush(&mut self) -> io::Result<()> {
+        // Do nothing, dropping the guard takes care of flushing
+        Ok(())
+    }
+}
+
+impl Drop for LogGuard {
+    fn drop(&mut self) {
+        unsafe {
+            bindings::qemu_log_unlock(self.0.as_ptr());
+        }
+    }
+}
+
+/// A macro to log messages conditionally based on a provided mask.
+///
+/// The `log_mask_ln` macro checks whether the given mask matches the current
+/// log level and, if so, formats and logs the message. It is the Rust
+/// counterpart of the `qemu_log_mask()` macro in the C implementation.
+///
+/// Errors from writing to the log are ignored.
+///
+/// # Parameters
+///
+/// - `$mask`: A log level mask. This should be a variant of the `Log` enum.
+/// - `$fmt`: A format string following the syntax and rules of the `format!`
+///   macro. It specifies the structure of the log message.
+/// - `$args`: Optional arguments to be interpolated into the format string.
+///
+/// # Example
+///
+/// ```
+/// use util::{log::Log, log_mask_ln};
+///
+/// let error_address = 0xbad;
+/// log_mask_ln!(Log::GuestError, "Address 0x{error_address:x} out of range");
+/// ```
+///
+/// It is also possible to use printf-style formatting, as well as having a
+/// trailing `,`:
+///
+/// ```
+/// use util::{log::Log, log_mask_ln};
+///
+/// let error_address = 0xbad;
+/// log_mask_ln!(
+///     Log::GuestError,
+///     "Address 0x{:x} out of range",
+///     error_address,
+/// );
+/// ```
+#[macro_export]
+macro_rules! log_mask_ln {
+    ($mask:expr, $fmt:tt $($args:tt)*) => {{
+        // Type assertion to enforce type `Log` for $mask
+        let _: $crate::log::Log = $mask;
+
+        if unsafe {
+            ($crate::bindings::qemu_loglevel & ($mask as std::os::raw::c_int)) != 0
+        } {
+            _ = $crate::log::LogGuard::log_fmt(
+                format_args!("{}\n", format_args!($fmt $($args)*)));
+        }
+    }};
+}