s390/diag: add tracepoint for diagnose calls

To be able to analyse problems in regard to hypervisor overhead
add a tracepoing for diagnose calls. It reports the number of
the diagnose issued, e.g.

            sshd-1385  [002] ....    42.701431: diagnose: nr=0x9c
          <idle>-0     [001] ..s.    43.587528: diagnose: nr=0x9c

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/include/asm/diag.h

@@ -33,16 +33,8 @@ enum diag_stat_enum {
 	NR_DIAG_STAT
 };
 
-struct diag_stat {
-	unsigned int counter[NR_DIAG_STAT];
-};
-
-DECLARE_PER_CPU(struct diag_stat, diag_stat);
-
-static inline void diag_stat_inc(enum diag_stat_enum nr)
-{
-	this_cpu_inc(diag_stat.counter[nr]);
-}
+void diag_stat_inc(enum diag_stat_enum nr);
+void diag_stat_inc_norecursion(enum diag_stat_enum nr);
 
 /*
  * Diagnose 10: Release page range

arch/s390/include/asm/trace/diag.h

@@ -0,0 +1,43 @@
+/*
+ * Tracepoint header for s390 diagnose calls
+ *
+ * Copyright IBM Corp. 2015
+ * Author(s): Martin Schwidefsky <schwidefsky@de.ibm.com>
+ */
+
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM s390
+
+#if !defined(_TRACE_S390_DIAG_H) || defined(TRACE_HEADER_MULTI_READ)
+#define _TRACE_S390_DIAG_H
+
+#include <linux/tracepoint.h>
+
+#undef TRACE_INCLUDE_PATH
+#undef TRACE_INCLUDE_FILE
+
+#define TRACE_INCLUDE_PATH asm/trace
+#define TRACE_INCLUDE_FILE diag
+
+TRACE_EVENT(diagnose,
+	TP_PROTO(unsigned short nr),
+	TP_ARGS(nr),
+	TP_STRUCT__entry(
+		__field(unsigned short, nr)
+	),
+	TP_fast_assign(
+		__entry->nr = nr;
+	),
+	TP_printk("nr=0x%x", __entry->nr)
+);
+
+#ifdef CONFIG_TRACEPOINTS
+void trace_diagnose_norecursion(int diag_nr);
+#else
+static inline void trace_diagnose_norecursion(int diag_nr) { }
+#endif
+
+#endif /* _TRACE_S390_DIAG_H */
+
+/* This part must be outside protection */
+#include <trace/define_trace.h>

arch/s390/kernel/Makefile

@@ -66,6 +66,8 @@ obj-$(CONFIG_UPROBES)		+= uprobes.o
 obj-$(CONFIG_PERF_EVENTS)	+= perf_event.o perf_cpum_cf.o perf_cpum_sf.o
 obj-$(CONFIG_PERF_EVENTS)	+= perf_cpum_cf_events.o
 
+obj-$(CONFIG_TRACEPOINTS)	+= trace.o
+
 # vdso
 obj-y				+= vdso64/
 obj-$(CONFIG_COMPAT)		+= vdso32/

arch/s390/kernel/diag.c

@@ -10,9 +10,13 @@
 #include <linux/seq_file.h>
 #include <linux/debugfs.h>
 #include <asm/diag.h>
+#include <asm/trace/diag.h>
 
-DEFINE_PER_CPU(struct diag_stat, diag_stat);
-EXPORT_PER_CPU_SYMBOL(diag_stat);
+struct diag_stat {
+	unsigned int counter[NR_DIAG_STAT];
+};
+
+static DEFINE_PER_CPU(struct diag_stat, diag_stat);
 
 struct diag_desc {
 	int code;
@@ -114,6 +118,20 @@ static int __init show_diag_stat_init(void)
 
 device_initcall(show_diag_stat_init);
 
+void diag_stat_inc(enum diag_stat_enum nr)
+{
+	this_cpu_inc(diag_stat.counter[nr]);
+	trace_diagnose(diag_map[nr].code);
+}
+EXPORT_SYMBOL(diag_stat_inc);
+
+void diag_stat_inc_norecursion(enum diag_stat_enum nr)
+{
+	this_cpu_inc(diag_stat.counter[nr]);
+	trace_diagnose_norecursion(diag_map[nr].code);
+}
+EXPORT_SYMBOL(diag_stat_inc_norecursion);
+
 /*
  * Diagnose 14: Input spool file manipulation
  */

arch/s390/kernel/smp.c

@@ -377,11 +377,11 @@ int smp_vcpu_scheduled(int cpu)
 void smp_yield_cpu(int cpu)
 {
 	if (MACHINE_HAS_DIAG9C) {
-		diag_stat_inc(DIAG_STAT_X09C);
+		diag_stat_inc_norecursion(DIAG_STAT_X09C);
 		asm volatile("diag %0,0,0x9c"
 			     : : "d" (pcpu_devices[cpu].address));
 	} else if (MACHINE_HAS_DIAG44) {
-		diag_stat_inc(DIAG_STAT_X044);
+		diag_stat_inc_norecursion(DIAG_STAT_X044);
 		asm volatile("diag 0,0,0x44");
 	}
 }

arch/s390/kernel/trace.c

@@ -0,0 +1,29 @@
+/*
+ * Tracepoint definitions for s390
+ *
+ * Copyright IBM Corp. 2015
+ * Author(s): Martin Schwidefsky <schwidefsky@de.ibm.com>
+ */
+
+#include <linux/percpu.h>
+#define CREATE_TRACE_POINTS
+#include <asm/trace/diag.h>
+
+EXPORT_TRACEPOINT_SYMBOL(diagnose);
+
+static DEFINE_PER_CPU(unsigned int, diagnose_trace_depth);
+
+void trace_diagnose_norecursion(int diag_nr)
+{
+	unsigned long flags;
+	unsigned int *depth;
+
+	local_irq_save(flags);
+	depth = this_cpu_ptr(&diagnose_trace_depth);
+	if (*depth == 0) {
+		(*depth)++;
+		trace_diagnose(diag_nr);
+		(*depth)--;
+	}
+	local_irq_restore(flags);
+}