linux-kernel - Re: [PATCH V2 1/2] rust: cpu: Introduce CpuId abstraction

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Message-ID: <20250609111857.ijvagblorxtq7d2n@vireshk-i7>
Date: Mon, 9 Jun 2025 16:48:57 +0530
From: Viresh Kumar <viresh.kumar@...aro.org>
To: Boqun Feng <boqun.feng@...il.com>,
	"Rafael J. Wysocki" <rafael@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <peterz@...radead.org>,
	Miguel Ojeda <ojeda@...nel.org>,
	Alex Gaynor <alex.gaynor@...il.com>, Gary Guo <gary@...yguo.net>,
	Björn Roy Baron <bjorn3_gh@...tonmail.com>,
	Benno Lossin <lossin@...nel.org>,
	Andreas Hindborg <a.hindborg@...nel.org>,
	Alice Ryhl <aliceryhl@...gle.com>, Trevor Gross <tmgross@...ch.edu>,
	Danilo Krummrich <dakr@...nel.org>
Cc: Vincent Guittot <vincent.guittot@...aro.org>,
	Yury Norov <yury.norov@...il.com>, rust-for-linux@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH V2 1/2] rust: cpu: Introduce CpuId abstraction

On 09-06-25, 16:21, Viresh Kumar wrote:
> This adds abstraction for representing a CPU identifier.
> 
> Suggested-by: Boqun Feng <boqun.feng@...il.com>
> Signed-off-by: Viresh Kumar <viresh.kumar@...aro.org>
> ---
>  rust/kernel/cpu.rs | 102 +++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 102 insertions(+)

Boqun,

Should I implement CpuId::current() like this ? Will fold this into
1/2, if it looks okay.

diff --git a/rust/helpers/cpu.c b/rust/helpers/cpu.c
new file mode 100644
index 000000000000..61d0387c8cf3
--- /dev/null
+++ b/rust/helpers/cpu.c
@@ -0,0 +1,8 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/smp.h>
+
+unsigned int rust_helper_smp_processor_id(void)
+{
+       return smp_processor_id();
+}
diff --git a/rust/helpers/helpers.c b/rust/helpers/helpers.c
index 0f1b5d115985..16fa9bca5949 100644
--- a/rust/helpers/helpers.c
+++ b/rust/helpers/helpers.c
@@ -13,6 +13,7 @@
 #include "build_assert.c"
 #include "build_bug.c"
 #include "clk.c"
+#include "cpu.c"
 #include "cpufreq.c"
 #include "cpumask.c"
 #include "cred.c"
diff --git a/rust/kernel/cpu.rs b/rust/kernel/cpu.rs
index da53f04da495..b093d22ccbd9 100644
--- a/rust/kernel/cpu.rs
+++ b/rust/kernel/cpu.rs
@@ -94,6 +94,12 @@ pub fn from_u32(id: u32) -> Option<Self> {
     pub fn as_u32(&self) -> u32 {
         self.0
     }
+
+    /// Returns the ID of the CPU this code is currently running on.
+    pub fn current() -> Self {
+        // SAFETY: smp_processor_id() always return valid cpu id.
+        unsafe { Self::from_u32_unchecked(bindings::smp_processor_id()) }
+    }
 }

 impl From<CpuId> for u32 {

-- 
viresh