linux-kernel - [PATCH v6 9/9] x86/nmi: Print source information with the unknown NMI console message

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Message-ID: <20250513203803.2636561-10-sohil.mehta@intel.com>
Date: Tue, 13 May 2025 13:38:03 -0700
From: Sohil Mehta <sohil.mehta@...el.com>
To: x86@...nel.org,
	linux-kernel@...r.kernel.org
Cc: Xin Li <xin@...or.com>,
	"H . Peter Anvin" <hpa@...or.com>,
	Andy Lutomirski <luto@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Borislav Petkov <bp@...en8.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Sean Christopherson <seanjc@...gle.com>,
	Adrian Hunter <adrian.hunter@...el.com>,
	Kan Liang <kan.liang@...ux.intel.com>,
	Tony Luck <tony.luck@...el.com>,
	Zhang Rui <rui.zhang@...el.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Sohil Mehta <sohil.mehta@...el.com>,
	Andrew Cooper <andrew.cooper3@...rix.com>,
	"Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
	Jacob Pan <jacob.pan@...ux.microsoft.com>,
	Andi Kleen <ak@...ux.intel.com>,
	Kai Huang <kai.huang@...el.com>,
	Sandipan Das <sandipan.das@....com>,
	linux-perf-users@...r.kernel.org,
	linux-edac@...r.kernel.org,
	kvm@...r.kernel.org,
	linux-pm@...r.kernel.org,
	linux-trace-kernel@...r.kernel.org
Subject: [PATCH v6 9/9] x86/nmi: Print source information with the unknown NMI console message

The NMI-source bitmap is critical information provided by the NMI-source
reporting feature. It is very useful in debugging unknown NMIs since it
can pinpoint the exact source that caused the NMI.

Print the source bitmap along with the "Unknown NMI" kernel log message.

Signed-off-by: Sohil Mehta <sohil.mehta@...el.com>
---
v6: Drop the tracepoint modification part for now.

v5: New patch
---
 arch/x86/kernel/nmi.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/x86/kernel/nmi.c b/arch/x86/kernel/nmi.c
index 55ecbe2ab5e4..7a288603683f 100644
--- a/arch/x86/kernel/nmi.c
+++ b/arch/x86/kernel/nmi.c
@@ -376,6 +376,9 @@ unknown_nmi_error(unsigned char reason, struct pt_regs *regs)
 	pr_emerg_ratelimited("Uhhuh. NMI received for unknown reason %02x on CPU %d.\n",
 			     reason, smp_processor_id());
 
+	if (cpu_feature_enabled(X86_FEATURE_NMI_SOURCE))
+		pr_emerg_ratelimited("NMI-source bitmap is 0x%lx\n", fred_event_data(regs));
+
 	if (unknown_nmi_panic || panic_on_unrecovered_nmi)
 		nmi_panic(regs, "NMI: Not continuing");
 
-- 
2.43.0