LXR linux/arch/x86/kernel/process.h

   1/* SPDX-License-Identifier: GPL-2.0 */
   2//
   3// Code shared between 32 and 64 bit
   4
   5#include <asm/spec-ctrl.h>
   6
   7void __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 */
  13static 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