[RFC 13/26] rust: Add RCU bindings

[Zhao Liu]

Add rcu_read_lock() & rcu_read_unlock() bindings, then they can be used
in memory access.

Suggested-by: Paolo Bonzini <pbonz...@redhat.com>
Signed-off-by: Zhao Liu <zhao1....@intel.com>
---
 rust/qemu-api/meson.build |  1 +
 rust/qemu-api/src/lib.rs  |  1 +
 rust/qemu-api/src/rcu.rs  | 26 ++++++++++++++++++++++++++
 rust/qemu-api/wrapper.h   |  1 +
 4 files changed, 29 insertions(+)
 create mode 100644 rust/qemu-api/src/rcu.rs

diff --git a/rust/qemu-api/meson.build b/rust/qemu-api/meson.build
index a362d44ed396..d40472092248 100644
--- a/rust/qemu-api/meson.build
+++ b/rust/qemu-api/meson.build
@@ -68,6 +68,7 @@ _qemu_api_rs = static_library(
       'src/prelude.rs',
       'src/qdev.rs',
       'src/qom.rs',
+      'src/rcu.rs',
       'src/sysbus.rs',
       'src/timer.rs',
       'src/uninit.rs',
diff --git a/rust/qemu-api/src/lib.rs b/rust/qemu-api/src/lib.rs
index 86dcd8ef17a9..4705cf9ccbc5 100644
--- a/rust/qemu-api/src/lib.rs
+++ b/rust/qemu-api/src/lib.rs
@@ -26,6 +26,7 @@
 pub mod module;
 pub mod qdev;
 pub mod qom;
+pub mod rcu;
 pub mod sysbus;
 pub mod timer;
 pub mod uninit;
diff --git a/rust/qemu-api/src/rcu.rs b/rust/qemu-api/src/rcu.rs
new file mode 100644
index 000000000000..30d8b9e43967
--- /dev/null
+++ b/rust/qemu-api/src/rcu.rs
@@ -0,0 +1,26 @@
+// Copyright (C) 2025 Intel Corporation.
+// Author(s): Zhao Liu <zhao1....@intel.com>
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+//! Bindings for `rcu_read_lock` and `rcu_read_unlock`.
+//! More details about RCU in QEMU, please refer docs/devel/rcu.rst.
+
+use crate::bindings;
+
+/// Used by a reader to inform the reclaimer that the reader is
+/// entering an RCU read-side critical section.
+pub fn rcu_read_lock() {
+    // SAFETY: no return and no argument, everything is done at C side.
+    unsafe { bindings::rcu_read_lock() }
+}
+
+/// Used by a reader to inform the reclaimer that the reader is
+/// exiting an RCU read-side critical section.  Note that RCU
+/// read-side critical sections may be nested and/or overlapping.
+pub fn rcu_read_unlock() {
+    // SAFETY: no return and no argument, everything is done at C side.
+    unsafe { bindings::rcu_read_unlock() }
+}
+
+// FIXME: maybe we need rcu_read_lock_held() to check the rcu context,
+// then make it possible to add assertion at any RCU critical section.
diff --git a/rust/qemu-api/wrapper.h b/rust/qemu-api/wrapper.h
index 15a1b19847f2..ce0ac8d3f550 100644
--- a/rust/qemu-api/wrapper.h
+++ b/rust/qemu-api/wrapper.h
@@ -69,3 +69,4 @@ typedef enum memory_order {
 #include "qemu/timer.h"
 #include "system/address-spaces.h"
 #include "hw/char/pl011.h"
+#include "qemu/rcu.h"
-- 
2.34.1