1 /* SPDX-License-Identifier: GPL-2.0 */
2 //
3 // Code shared between 32 and 64 bit
4 
5 #include <asm/spec-ctrl.h>
6 
7 void __switch_to_xtra(struct task_struct *prev_p, struct task_struct *next_p);
8 
9 /*
10  * This needs to be inline to optimize for the common case where no extra
11  * work needs to be done.
12  */
switch_to_extra(struct task_struct * prev,struct task_struct * next)13 static inline void switch_to_extra(struct task_struct *prev,
14 				   struct task_struct *next)
15 {
16 	unsigned long next_tif = task_thread_info(next)->flags;
17 	unsigned long prev_tif = task_thread_info(prev)->flags;
18 
19 	if (IS_ENABLED(CONFIG_SMP)) {
20 		/*
21 		 * Avoid __switch_to_xtra() invocation when conditional
22 		 * STIBP is disabled and the only different bit is
23 		 * TIF_SPEC_IB. For CONFIG_SMP=n TIF_SPEC_IB is not
24 		 * in the TIF_WORK_CTXSW masks.
25 		 */
26 		if (!static_branch_likely(&switch_to_cond_stibp)) {
27 			prev_tif &= ~_TIF_SPEC_IB;
28 			next_tif &= ~_TIF_SPEC_IB;
29 		}
30 	}
31 
32 	/*
33 	 * __switch_to_xtra() handles debug registers, i/o bitmaps,
34 	 * speculation mitigations etc.
35 	 */
36 	if (unlikely(next_tif & _TIF_WORK_CTXSW_NEXT ||
37 		     prev_tif & _TIF_WORK_CTXSW_PREV))
38 		__switch_to_xtra(prev, next);
39 }
40