linux-kernel - [RFC PATCH 29/56] x86/apic: Add self-NMI support

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Message-ID: <20251013143444.3999-30-david.kaplan@amd.com>
Date: Mon, 13 Oct 2025 09:34:17 -0500
From: David Kaplan <david.kaplan@....com>
To: Thomas Gleixner <tglx@...utronix.de>, Borislav Petkov <bp@...en8.de>,
	Peter Zijlstra <peterz@...radead.org>, Josh Poimboeuf <jpoimboe@...nel.org>,
	Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>, Ingo Molnar
	<mingo@...hat.com>, Dave Hansen <dave.hansen@...ux.intel.com>,
	<x86@...nel.org>, "H . Peter Anvin" <hpa@...or.com>
CC: Alexander Graf <graf@...zon.com>, Boris Ostrovsky
	<boris.ostrovsky@...cle.com>, <linux-kernel@...r.kernel.org>
Subject: [RFC PATCH 29/56] x86/apic: Add self-NMI support

Add function to send an NMI-to-self which is needed for stop_machine_nmi().
Note that send_IPI_self() cannot be used to send an NMI so send_IPI() is
used.

Signed-off-by: David Kaplan <david.kaplan@....com>
---
 arch/x86/kernel/apic/ipi.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/arch/x86/kernel/apic/ipi.c b/arch/x86/kernel/apic/ipi.c
index 98a57cb4aa86..6d4e5aa27529 100644
--- a/arch/x86/kernel/apic/ipi.c
+++ b/arch/x86/kernel/apic/ipi.c
@@ -4,6 +4,7 @@
 #include <linux/delay.h>
 #include <linux/smp.h>
 #include <linux/string_choices.h>
+#include <linux/stop_machine.h>
 
 #include <asm/io_apic.h>
 
@@ -248,6 +249,12 @@ void default_send_IPI_self(int vector)
 	__default_send_IPI_shortcut(APIC_DEST_SELF, vector);
 }
 
+/* Self-NMI is used in stop_machine_nmi() */
+void arch_send_self_nmi(void)
+{
+	apic->send_IPI(smp_processor_id(), NMI_VECTOR);
+}
+
 #ifdef CONFIG_X86_32
 void default_send_IPI_mask_sequence_logical(const struct cpumask *mask, int vector)
 {
-- 
2.34.1