x86/idtentry: Switch to conditional RCU handling

Switch all idtentry_enter/exit() users over to the new conditional RCU
handling scheme and make the user mode entries in #DB, #INT3 and #MCE use
the user mode idtentry functions.
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
Signed-off-by: NIngo Molnar <mingo@kernel.org>
Acked-by: NAndy Lutomirski <luto@kernel.org>
Link: https://lore.kernel.org/r/20200521202117.382387286@linutronix.de

arch/x86/include/asm/idtentry.h

@@ -61,11 +61,12 @@ static __always_inline void __##func(struct pt_regs *regs);		\
 									\
 __visible noinstr void func(struct pt_regs *regs)			\
 {									\
-	idtentry_enter(regs);						\
+	bool rcu_exit = idtentry_enter_cond_rcu(regs);			\
+									\
 	instrumentation_begin();					\
 	__##func (regs);						\
 	instrumentation_end();						\
-	idtentry_exit(regs);						\
+	idtentry_exit_cond_rcu(regs, rcu_exit);				\
 }									\
 									\
 static __always_inline void __##func(struct pt_regs *regs)
@@ -107,11 +108,12 @@ static __always_inline void __##func(struct pt_regs *regs,		\
 __visible noinstr void func(struct pt_regs *regs,			\
 			    unsigned long error_code)			\
 {									\
-	idtentry_enter(regs);						\
+	bool rcu_exit = idtentry_enter_cond_rcu(regs);			\
+									\
 	instrumentation_begin();					\
 	__##func (regs, error_code);					\
 	instrumentation_end();						\
-	idtentry_exit(regs);						\
+	idtentry_exit_cond_rcu(regs, rcu_exit);				\
 }									\
 									\
 static __always_inline void __##func(struct pt_regs *regs,		\

arch/x86/kernel/cpu/mce/core.c

@@ -1929,11 +1929,11 @@ static __always_inline void exc_machine_check_kernel(struct pt_regs *regs)
 
 static __always_inline void exc_machine_check_user(struct pt_regs *regs)
 {
-	idtentry_enter(regs);
+	idtentry_enter_user(regs);
 	instrumentation_begin();
 	machine_check_vector(regs);
 	instrumentation_end();
-	idtentry_exit(regs);
+	idtentry_exit_user(regs);
 }
 
 #ifdef CONFIG_X86_64

arch/x86/kernel/traps.c

@@ -619,18 +619,18 @@ DEFINE_IDTENTRY_RAW(exc_int3)
 		return;
 
 	/*
-	 * idtentry_enter() uses static_branch_{,un}likely() and therefore
+	 * idtentry_enter_user() uses static_branch_{,un}likely() and therefore
 	 * can trigger INT3, hence poke_int3_handler() must be done
 	 * before. If the entry came from kernel mode, then use nmi_enter()
 	 * because the INT3 could have been hit in any context including
 	 * NMI.
 	 */
 	if (user_mode(regs)) {
-		idtentry_enter(regs);
+		idtentry_enter_user(regs);
 		instrumentation_begin();
 		do_int3_user(regs);
 		instrumentation_end();
-		idtentry_exit(regs);
+		idtentry_exit_user(regs);
 	} else {
 		nmi_enter();
 		instrumentation_begin();
@@ -877,7 +877,7 @@ static __always_inline void exc_debug_kernel(struct pt_regs *regs,
 static __always_inline void exc_debug_user(struct pt_regs *regs,
 					   unsigned long dr6)
 {
-	idtentry_enter(regs);
+	idtentry_enter_user(regs);
 	clear_thread_flag(TIF_BLOCKSTEP);
 
 	/*
@@ -886,7 +886,7 @@ static __always_inline void exc_debug_user(struct pt_regs *regs,
 	 * User wants a sigtrap for that.
 	 */
 	handle_debug(regs, dr6, !dr6);
-	idtentry_exit(regs);
+	idtentry_exit_user(regs);
 }
 
 #ifdef CONFIG_X86_64