KVM: s390: add tracepoint in gmap notifier

The gmap notifier is called for changes in table entries with the
notifier bit set. To diagnose performance issues, it can be useful to
see what causes certain changes in the gmap.

Hence, add a tracepoint in the gmap notifier.

Signed-off-by: Nico Boehr <[email protected]>
Acked-by: David Hildenbrand <[email protected]>
Reviewed-by: Claudio Imbrenda <[email protected]>
Acked-by: Janosch Frank <[email protected]>
Signed-off-by: Janosch Frank <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Message-Id: <[email protected]>

Author: Nico Boehr

arch/s390/kvm/kvm-s390.c

@@ -4060,6 +4060,8 @@ static void kvm_gmap_notifier(struct gmap *gmap, unsigned long start,
 	unsigned long prefix;
 	unsigned long i;
 
+	trace_kvm_s390_gmap_notifier(start, end, gmap_is_shadow(gmap));
+
 	if (gmap_is_shadow(gmap))
 		return;
 	if (start >= 1UL << 31)

arch/s390/kvm/trace-s390.h

@@ -333,6 +333,29 @@ TRACE_EVENT(kvm_s390_airq_suppressed,
 		      __entry->id, __entry->isc)
 	);
 
+/*
+ * Trace point for gmap notifier calls.
+ */
+TRACE_EVENT(kvm_s390_gmap_notifier,
+	    TP_PROTO(unsigned long start, unsigned long end, unsigned int shadow),
+	    TP_ARGS(start, end, shadow),
+
+	    TP_STRUCT__entry(
+		    __field(unsigned long, start)
+		    __field(unsigned long, end)
+		    __field(unsigned int, shadow)
+		    ),
+
+	    TP_fast_assign(
+		    __entry->start = start;
+		    __entry->end = end;
+		    __entry->shadow = shadow;
+		    ),
+
+	    TP_printk("gmap notified (start:0x%lx end:0x%lx shadow:%d)",
+		      __entry->start, __entry->end, __entry->shadow)
+	);
+
 
 #endif /* _TRACE_KVMS390_H */