linux-kernel - [PATCH v3] x86/mce/inject: Remove call to mce_notify

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Message-ID: <20250225143348.268469-1-nik.borisov@suse.com>
Date: Tue, 25 Feb 2025 16:33:48 +0200
From: Nikolay Borisov <nik.borisov@...e.com>
To: linux-edac@...r.kernel.org
Cc: bp@...en8.de,
	qiuxu.zhuo@...el.com,
	x86@...nel.org,
	linux-kernel@...r.kernel.org,
	Nikolay Borisov <nik.borisov@...e.com>
Subject: [PATCH v3] x86/mce/inject: Remove call to mce_notify_irq()

The call to mce_notify_irq() has been there since the initial version of
the soft inject mce machinery, introduced in ea149b36c7f5 ("x86,
mce: add basic error injection infrastructure"). At that time it was
functional since injecting an MCE resulted in the following call chain:

    raise_mce()
      ->machine_check_poll()
          ->mce_log() - sets notfiy_user_bit
    ->mce_notify_user() (current mce_notify_irq) consumed the bit and called the
    usermode helper.

However, with the introduction of 011d82611172 ("RAS: Add a Corrected Errors Collector")
the code got moved around and the usermode helper began to be called
via the early notifier (mce_first_notifier()) rendering the call in
raise_local() defunct as the mce_need_notify bit (ex notify_user) is
only being set from the early notifier.

Remove the noop call and make mce_notify_irq static. No functional
changes.

Signed-off-by: Nikolay Borisov <nik.borisov@...e.com>
---
 arch/x86/include/asm/mce.h       |  2 --
 arch/x86/kernel/cpu/mce/core.c   | 44 ++++++++++++++++----------------
 arch/x86/kernel/cpu/mce/inject.c |  1 -
 3 files changed, 22 insertions(+), 25 deletions(-)

diff --git a/arch/x86/include/asm/mce.h b/arch/x86/include/asm/mce.h
index eb2db07ef39c..6c77c03139f7 100644
--- a/arch/x86/include/asm/mce.h
+++ b/arch/x86/include/asm/mce.h
@@ -296,8 +296,6 @@ enum mcp_flags {
 
 void machine_check_poll(enum mcp_flags flags, mce_banks_t *b);
 
-bool mce_notify_irq(void);
-
 DECLARE_PER_CPU(struct mce, injectm);
 
 /* Disable CMCI/polling for MCA bank claimed by firmware */
diff --git a/arch/x86/kernel/cpu/mce/core.c b/arch/x86/kernel/cpu/mce/core.c
index 0dc00c9894c7..1f14c3308b6b 100644
--- a/arch/x86/kernel/cpu/mce/core.c
+++ b/arch/x86/kernel/cpu/mce/core.c
@@ -584,6 +584,28 @@ bool mce_is_correctable(struct mce *m)
 }
 EXPORT_SYMBOL_GPL(mce_is_correctable);
 
+/*
+ * Notify the user(s) about new machine check events.
+ * Can be called from interrupt context, but not from machine check/NMI
+ * context.
+ */
+static bool mce_notify_irq(void)
+{
+	/* Not more than two messages every minute */
+	static DEFINE_RATELIMIT_STATE(ratelimit, 60*HZ, 2);
+
+	if (test_and_clear_bit(0, &mce_need_notify)) {
+		mce_work_trigger();
+
+		if (__ratelimit(&ratelimit))
+			pr_info(HW_ERR "Machine check events logged\n");
+
+		return true;
+	}
+
+	return false;
+}
+
 static int mce_early_notifier(struct notifier_block *nb, unsigned long val,
 			      void *data)
 {
@@ -1773,28 +1795,6 @@ static void mce_timer_delete_all(void)
 		del_timer_sync(&per_cpu(mce_timer, cpu));
 }
 
-/*
- * Notify the user(s) about new machine check events.
- * Can be called from interrupt context, but not from machine check/NMI
- * context.
- */
-bool mce_notify_irq(void)
-{
-	/* Not more than two messages every minute */
-	static DEFINE_RATELIMIT_STATE(ratelimit, 60*HZ, 2);
-
-	if (test_and_clear_bit(0, &mce_need_notify)) {
-		mce_work_trigger();
-
-		if (__ratelimit(&ratelimit))
-			pr_info(HW_ERR "Machine check events logged\n");
-
-		return true;
-	}
-	return false;
-}
-EXPORT_SYMBOL_GPL(mce_notify_irq);
-
 static void __mcheck_cpu_mce_banks_init(void)
 {
 	struct mce_bank *mce_banks = this_cpu_ptr(mce_banks_array);
diff --git a/arch/x86/kernel/cpu/mce/inject.c b/arch/x86/kernel/cpu/mce/inject.c
index 313fe682db33..06e3cf7229ce 100644
--- a/arch/x86/kernel/cpu/mce/inject.c
+++ b/arch/x86/kernel/cpu/mce/inject.c
@@ -229,7 +229,6 @@ static int raise_local(void)
 	} else if (m->status) {
 		pr_info("Starting machine check poll CPU %d\n", cpu);
 		raise_poll(m);
-		mce_notify_irq();
 		pr_info("Machine check poll done on CPU %d\n", cpu);
 	} else
 		m->finished = 0;
-- 
2.43.0