context_tracking: Run vtime_user_enter/exit only when state == CONTEXT_USER

Only run vtime_user_enter, vtime_user_exit, and the user enter & exit
trace points when we are entering or exiting user state, respectively.

The KVM code in guest_enter and guest_exit already take care of calling
vtime_guest_enter and vtime_guest_exit, respectively.

The RCU code only distinguishes between "idle" and "not idle or kernel".
There should be no need to add an additional (unused) state there.

Reviewed-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Rik van Riel <riel@redhat.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Will deacon <will.deacon@arm.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Luiz Capitulino <lcapitulino@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>

kernel/context_tracking.c

@@ -77,7 +77,6 @@ void context_tracking_enter(enum ctx_state state)
 	local_irq_save(flags);
 	if ( __this_cpu_read(context_tracking.state) != state) {
 		if (__this_cpu_read(context_tracking.active)) {
-			trace_user_enter(0);
 			/*
 			 * At this stage, only low level arch entry code remains and
 			 * then we'll run in userspace. We can assume there won't be
@@ -85,7 +84,10 @@ void context_tracking_enter(enum ctx_state state)
 			 * user_exit() or rcu_irq_enter(). Let's remove RCU's dependency
 			 * on the tick.
 			 */
-			vtime_user_enter(current);
+			if (state == CONTEXT_USER) {
+				trace_user_enter(0);
+				vtime_user_enter(current);
+			}
 			rcu_user_enter();
 		}
 		/*
@@ -143,8 +145,10 @@ void context_tracking_exit(enum ctx_state state)
 			 * RCU core about that (ie: we may need the tick again).
 			 */
 			rcu_user_exit();
-			vtime_user_exit(current);
-			trace_user_exit(0);
+			if (state == CONTEXT_USER) {
+				vtime_user_exit(current);
+				trace_user_exit(0);
+			}
 		}
 		__this_cpu_write(context_tracking.state, CONTEXT_KERNEL);
 	}