locking/lock_events: Don't show pvqspinlock events on bare metal

On bare metal, the pvqspinlock event counts will always be 0. So there
is no point in showing their corresponding debugfs files. So they are
skipped in this case.

Signed-off-by: Waiman Long <longman@redhat.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Davidlohr Bueso <dbueso@suse.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tim Chen <tim.c.chen@linux.intel.com>
Cc: Will Deacon <will.deacon@arm.com>
Link: http://lkml.kernel.org/r/20190404174320.22416-10-longman@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

kernel/locking/lock_events.c

@@ -115,6 +115,29 @@ static const struct file_operations fops_lockevent = {
 	.llseek = default_llseek,
 };
 
+#ifdef CONFIG_PARAVIRT_SPINLOCKS
+#include <asm/paravirt.h>
+
+static bool __init skip_lockevent(const char *name)
+{
+	static int pv_on __initdata = -1;
+
+	if (pv_on < 0)
+		pv_on = !pv_is_native_spin_unlock();
+	/*
+	 * Skip PV qspinlock events on bare metal.
+	 */
+	if (!pv_on && !memcmp(name, "pv_", 3))
+		return true;
+	return false;
+}
+#else
+static inline bool skip_lockevent(const char *name)
+{
+	return false;
+}
+#endif
+
 /*
  * Initialize debugfs for the locking event counts.
  */
@@ -133,10 +156,13 @@ static int __init init_lockevent_counts(void)
 	 * root is allowed to do the read/write to limit impact to system
 	 * performance.
 	 */
-	for (i = 0; i < lockevent_num; i++)
+	for (i = 0; i < lockevent_num; i++) {
+		if (skip_lockevent(lockevent_names[i]))
+			continue;
 		if (!debugfs_create_file(lockevent_names[i], 0400, d_counts,
 					 (void *)(long)i, &fops_lockevent))
 			goto fail_undo;
+	}
 
 	if (!debugfs_create_file(lockevent_names[LOCKEVENT_reset_cnts], 0200,
 				 d_counts, (void *)(long)LOCKEVENT_reset_cnts,