_TIF_FSCHECK)
/* flags to check in __switch_to() */
-#define _TIF_WORK_CTXSW \
+#define _TIF_WORK_CTXSW_BASE \
(_TIF_IO_BITMAP|_TIF_NOCPUID|_TIF_NOTSC|_TIF_BLOCKSTEP| \
- _TIF_SSBD|_TIF_SPEC_IB)
+ _TIF_SSBD)
+
+/*
+ * Avoid calls to __switch_to_xtra() on UP as STIBP is not evaluated.
+ */
+#ifdef CONFIG_SMP
+# define _TIF_WORK_CTXSW (_TIF_WORK_CTXSW_BASE | _TIF_SPEC_IB)
+#else
+# define _TIF_WORK_CTXSW (_TIF_WORK_CTXSW_BASE)
+#endif
#define _TIF_WORK_CTXSW_PREV (_TIF_WORK_CTXSW|_TIF_USER_RETURN_NOTIFY)
#define _TIF_WORK_CTXSW_NEXT (_TIF_WORK_CTXSW)
//
// Code shared between 32 and 64 bit
+#include <asm/spec-ctrl.h>
+
void __switch_to_xtra(struct task_struct *prev_p, struct task_struct *next_p);
/*
unsigned long next_tif = task_thread_info(next)->flags;
unsigned long prev_tif = task_thread_info(prev)->flags;
+ if (IS_ENABLED(CONFIG_SMP)) {
+ /*
+ * Avoid __switch_to_xtra() invocation when conditional
+ * STIPB is disabled and the only different bit is
+ * TIF_SPEC_IB. For CONFIG_SMP=n TIF_SPEC_IB is not
+ * in the TIF_WORK_CTXSW masks.
+ */
+ if (!static_branch_likely(&switch_to_cond_stibp)) {
+ prev_tif &= ~_TIF_SPEC_IB;
+ next_tif &= ~_TIF_SPEC_IB;
+ }
+ }
+
/*
* __switch_to_xtra() handles debug registers, i/o bitmaps,
* speculation mitigations etc.