[PATCH 2/2] trace,x86: Add nmi to the irq_vectors class

[Daniel Bristot de Oliveira <bristot@redhat.com>]

Currently, the irq_vector class of tracepoints does not include the NMI
entry. The NMI was in the first set of tracepoints for IRQs, but it was
dropped off because of the logic of switching IDT when enabling trace[1].
However, as the switching IDT logic was removed [2], it is possible to add
the NMI tracepoints back.

The tracepoints looks like:
 <idle>-0     [000] d.Z.   179.594315: nmi_entry: vector=2
 <idle>-0     [000] d.Z.   179.594396: nmi_exit: vector=2

[1] trace,x86: irq vector tracepoint support
    https://lwn.net/Articles/555465/
[2] commit 4b9a8dca0e58 ("x86/idt: Remove the tracing IDT completely")

Signed-off-by: Daniel Bristot de Oliveira <bristot@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Clark Williams <williams@redhat.com>
Cc: linux-kernel@vger.kernel.org
Cc: x86@kernel.org
---
 arch/x86/include/asm/trace/irq_vectors.h | 5 +++++
 arch/x86/kernel/nmi.c                    | 4 ++++
 2 files changed, 9 insertions(+)

diff --git a/arch/x86/include/asm/trace/irq_vectors.h b/arch/x86/include/asm/trace/irq_vectors.h
index bc9669df97c9..5b93e1a6b1fe 100644
--- a/arch/x86/include/asm/trace/irq_vectors.h
+++ b/arch/x86/include/asm/trace/irq_vectors.h
@@ -144,6 +144,11 @@ DEFINE_IRQ_VECTOR_EVENT(thermal_apic);
  */
 DEFINE_IRQ_VECTOR_EVENT(external_interrupt);
 
+/*
+ * nmi - called when entering/exiting from nmi vector handler.
+ */
+DEFINE_IRQ_VECTOR_EVENT(nmi);
+
 TRACE_EVENT(vector_config,
 
 	TP_PROTO(unsigned int irq, unsigned int vector,
diff --git a/arch/x86/kernel/nmi.c b/arch/x86/kernel/nmi.c
index 18bc9b51ac9b..fa2d16b3af60 100644
--- a/arch/x86/kernel/nmi.c
+++ b/arch/x86/kernel/nmi.c
@@ -37,6 +37,8 @@
 
 #define CREATE_TRACE_POINTS
 #include <trace/events/nmi.h>
+#undef CREATE_TRACE_POINTS
+#include <asm/trace/irq_vectors.h>
 
 struct nmi_desc {
 	raw_spinlock_t lock;
@@ -514,12 +516,14 @@ do_nmi(struct pt_regs *regs, long error_code)
 #endif
 
 	nmi_enter();
+	trace_nmi_entry(2);
 
 	inc_irq_stat(__nmi_count);
 
 	if (!ignore_nmis)
 		default_do_nmi(regs);
 
+	trace_nmi_exit(2);
 	nmi_exit();
 
 #ifdef CONFIG_X86_64
-- 
2.17.1