linux-kernel - [PATCH 5/9] x86/nmi: Fix comment in unknown NMI handling

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Message-ID: <20250327234629.3953536-6-sohil.mehta@intel.com>
Date: Thu, 27 Mar 2025 23:46:25 +0000
From: Sohil Mehta <sohil.mehta@...el.com>
To: x86@...nel.org,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>
Cc: Borislav Petkov <bp@...en8.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	"H . Peter Anvin" <hpa@...or.com>,
	Josh Poimboeuf <jpoimboe@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Sohil Mehta <sohil.mehta@...el.com>,
	"Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
	Kai Huang <kai.huang@...el.com>,
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
	Mike Rapoport <rppt@...nel.org>,
	Petr Mladek <pmladek@...e.com>,
	Jani Nikula <jani.nikula@...el.com>,
	Tony Luck <tony.luck@...el.com>,
	Xin Li <xin@...or.com>,
	linux-kernel@...r.kernel.org
Subject: [PATCH 5/9] x86/nmi: Fix comment in unknown NMI handling

The comment in unknown NMI handling is incorrect and misleading. There
is no longer a restriction on having a single Unknown NMI handler. Also,
nmi_handle() does not use the 'b2b' parameter anymore.

The changes that made the comment outdated are:

commit 0d443b70cc92 ("x86/platform: Remove warning message for duplicate
NMI handlers")

commit bf9f2ee28d47 ("x86/nmi: Remove the 'b2b' parameter from
nmi_handle()")

Remove the old comment and update it to reflect the current intention.

Signed-off-by: Sohil Mehta <sohil.mehta@...el.com>
---
 arch/x86/kernel/nmi.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kernel/nmi.c b/arch/x86/kernel/nmi.c
index cdfb3864d59a..2a07c9adc6a6 100644
--- a/arch/x86/kernel/nmi.c
+++ b/arch/x86/kernel/nmi.c
@@ -327,10 +327,9 @@ unknown_nmi_error(unsigned char reason, struct pt_regs *regs)
 	int handled;
 
 	/*
-	 * Use 'false' as back-to-back NMIs are dealt with one level up.
-	 * Of course this makes having multiple 'unknown' handlers useless
-	 * as only the first one is ever run (unless it can actually determine
-	 * if it caused the NMI)
+	 * As a last resort, let the "unknown" handlers make a
+	 * best-effort attempt to figure out if they can claim
+	 * responsibility for this Unknown NMI.
 	 */
 	handled = nmi_handle(NMI_UNKNOWN, regs);
 	if (handled) {
-- 
2.43.0