context_tracking: remove duplicate enabled check

All calls to context_tracking_enter and context_tracking_exit
are already checking context_tracking_is_enabled, except the
context_tracking_user_enter and context_tracking_user_exit
functions left in for the benefit of assembly calls.

Pull the check up to those functions, by making them simple
wrappers around the user_enter and user_exit inline functions.

Cc: Frederic Weisbecker <[e-mail]>
Cc: Paul McKenney <[e-mail]>
Reviewed-by: Rik van Riel <[e-mail]>
Tested-by: Rik van Riel <[e-mail]>
Acked-by: Andy Lutomirski <[e-mail]>
Signed-off-by: Paolo Bonzini <[e-mail]>

include/linux/context_tracking.h

···
 static inline void user_enter(void)
 {
 	if (context_tracking_is_enabled())
-		context_tracking_user_enter();
+		context_tracking_enter(CONTEXT_USER);
 
 }
 static inline void user_exit(void)
 {
 	if (context_tracking_is_enabled())
-		context_tracking_user_exit();
+		context_tracking_exit(CONTEXT_USER);
 }
 
 static inline enum ctx_state exception_enter(void)

kernel/context_tracking.c

···
 	unsigned long flags;
 
 	/*
-	 * Repeat the user_enter() check here because some archs may be calling
-	 * this from asm and if no CPU needs context tracking, they shouldn't
-	 * go further. Repeat the check here until they support the inline static
-	 * key check.
-	 */
-	if (!context_tracking_is_enabled())
-		return;
-
-	/*
 	 * Some contexts may involve an exception occuring in an irq,
 	 * leading to that nesting:
 	 * rcu_irq_enter() rcu_user_exit() rcu_user_exit() rcu_irq_exit()
···
 
 void context_tracking_user_enter(void)
 {
-	context_tracking_enter(CONTEXT_USER);
+	user_enter();
 }
 NOKPROBE_SYMBOL(context_tracking_user_enter);
 
···
 void context_tracking_exit(enum ctx_state state)
 {
 	unsigned long flags;
-
-	if (!context_tracking_is_enabled())
-		return;
 
 	if (in_interrupt())
 		return;
···
 
 void context_tracking_user_exit(void)
 {
-	context_tracking_exit(CONTEXT_USER);
+	user_exit();
 }
 NOKPROBE_SYMBOL(context_tracking_user_exit);