[PATCH 1/2] rust/qemu-api: Add initial logging support based on C API

[Bernhard Beschow <shentey@gmail.com>]

A qemu_log_mask!() macro is provided which expects similar arguments as the C
version. However, the formatting works as one would expect from Rust.

To maximize code reuse the macro is just a thin wrapper around qemu_log().
Also, just the bare minimum of logging masks is provided which should suffice
for the current use case of Rust in QEMU.

Signed-off-by: Bernhard Beschow <shentey@gmail.com>
---
 docs/devel/rust.rst       |  1 +
 rust/wrapper.h            |  2 ++
 rust/qemu-api/meson.build |  1 +
 rust/qemu-api/src/lib.rs  |  1 +
 rust/qemu-api/src/log.rs  | 55 +++++++++++++++++++++++++++++++++++++++
 5 files changed, 60 insertions(+)
 create mode 100644 rust/qemu-api/src/log.rs

diff --git a/docs/devel/rust.rst b/docs/devel/rust.rst
index 88bdec1eb2..bc50216dc6 100644
--- a/docs/devel/rust.rst
+++ b/docs/devel/rust.rst
@@ -187,6 +187,7 @@ module           status
 ``c_str``        complete
 ``errno``        complete
 ``irq``          complete
+``log``          proof of concept
 ``memory``       stable
 ``module``       complete
 ``offset_of``    stable
diff --git a/rust/wrapper.h b/rust/wrapper.h
index d4fec54657..9518face53 100644
--- a/rust/wrapper.h
+++ b/rust/wrapper.h
@@ -48,6 +48,8 @@ typedef enum memory_order {
 #endif /* __CLANG_STDATOMIC_H */
 
 #include "qemu/osdep.h"
+#include "qemu/log.h"
+#include "qemu/log-for-trace.h"
 #include "qemu/module.h"
 #include "qemu-io.h"
 #include "system/system.h"
diff --git a/rust/qemu-api/meson.build b/rust/qemu-api/meson.build
index 858685ddd4..112f6735a9 100644
--- a/rust/qemu-api/meson.build
+++ b/rust/qemu-api/meson.build
@@ -26,6 +26,7 @@ _qemu_api_rs = static_library(
       'src/c_str.rs',
       'src/errno.rs',
       'src/irq.rs',
+      'src/log.rs',
       'src/memory.rs',
       'src/module.rs',
       'src/offset_of.rs',
diff --git a/rust/qemu-api/src/lib.rs b/rust/qemu-api/src/lib.rs
index 05f38b51d3..b54989a243 100644
--- a/rust/qemu-api/src/lib.rs
+++ b/rust/qemu-api/src/lib.rs
@@ -21,6 +21,7 @@
 pub mod chardev;
 pub mod errno;
 pub mod irq;
+pub mod log;
 pub mod memory;
 pub mod module;
 pub mod offset_of;
diff --git a/rust/qemu-api/src/log.rs b/rust/qemu-api/src/log.rs
new file mode 100644
index 0000000000..3103a86efa
--- /dev/null
+++ b/rust/qemu-api/src/log.rs
@@ -0,0 +1,55 @@
+// Copyright 2025 Bernhard Beschow <shentey@gmail.com>
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+pub use crate::bindings::{LOG_GUEST_ERROR, LOG_INVALID_MEM, LOG_UNIMP};
+
+/// A macro to log messages conditionally based on a provided mask.
+///
+/// The `qemu_log_mask` macro checks whether the given mask matches the
+/// current log level and, if so, formats and logs the message.
+///
+/// # Parameters
+///
+/// - `$mask`: The log mask to check. This should be an integer value
+///   indicating the log level mask.
+/// - `$fmt`: A format string following the syntax and rules of the `format!`
+///   macro. It specifies the structure of the log message.
+/// - `$args`: Optional arguments to be interpolated into the format string.
+///
+/// # Example
+///
+/// ```
+/// use qemu_api::log::LOG_GUEST_ERROR;
+///
+/// qemu_log_mask!(
+///     LOG_GUEST_ERROR,
+///     "Address 0x{error_address:x} out of range\n"
+/// );
+/// ```
+///
+/// It is also possible to use printf style:
+///
+/// ```
+/// use qemu_api::log::LOG_GUEST_ERROR;
+///
+/// qemu_log_mask!(
+///     LOG_GUEST_ERROR,
+///     "Address 0x{:x} out of range\n",
+///     error_address
+/// );
+/// ```
+#[macro_export]
+macro_rules! qemu_log_mask {
+    ($mask:expr, $fmt:expr $(, $args:expr)*) => {{
+        if unsafe {
+            (::qemu_api::bindings::qemu_loglevel & ($mask as std::os::raw::c_int)) != 0
+        } {
+            let formatted_string = format!($fmt, $($args),*);
+            let c_string = std::ffi::CString::new(formatted_string).unwrap();
+
+            unsafe {
+                ::qemu_api::bindings::qemu_log(c_string.as_ptr());
+            }
+        }
+    }};
+}
-- 
2.49.0