The following commit has been merged into the x86/nmi branch of tip:

Commit-ID:     b4bc3144c1eca9107f45018000a1e68bfd308d8c
Gitweb:        https://git.kernel.org/tip/b4bc3144c1eca9107f45018000a1e68bfd308d8c
Author:        Sohil Mehta <sohil.mehta@intel.com>
AuthorDate:    Thu, 27 Mar 2025 23:46:25 
Committer:     Ingo Molnar <mingo@kernel.org>
CommitterDate: Tue, 01 Apr 2025 22:26:11 +02:00

x86/nmi: Fix comment in unknown_nmi_error()

The comment in unknown_nmi_error() is incorrect and misleading. There
is no longer a restriction on having a single Unknown NMI handler. Also,
nmi_handle() never used the 'b2b' parameter.

The commits that made the comment outdated are:

  0d443b70cc92 ("x86/platform: Remove warning message for duplicate NMI handlers")
  bf9f2ee28d47 ("x86/nmi: Remove the 'b2b' parameter from nmi_handle()")

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

Signed-off-by: Sohil Mehta <sohil.mehta@intel.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Kai Huang <kai.huang@intel.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Nikolay Borisov <nik.borisov@suse.com>
Link: https://lore.kernel.org/r/20250327234629.3953536-6-sohil.mehta@intel.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 cdfb386..2a07c9a 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) {