diff options
| -rw-r--r-- | arch/x86/include/asm/thread_info.h | 13 | ||||
| -rw-r--r-- | arch/x86/kernel/process.h | 15 |
2 files changed, 26 insertions, 2 deletions
diff --git a/arch/x86/include/asm/thread_info.h b/arch/x86/include/asm/thread_info.h index 78ebda74b225..7b30338ca55b 100644 --- a/arch/x86/include/asm/thread_info.h +++ b/arch/x86/include/asm/thread_info.h @@ -149,9 +149,18 @@ struct thread_info { _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) diff --git a/arch/x86/kernel/process.h b/arch/x86/kernel/process.h index 020fbfac3a27..898e97cf6629 100644 --- a/arch/x86/kernel/process.h +++ b/arch/x86/kernel/process.h @@ -2,6 +2,8 @@ // // 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); /* @@ -14,6 +16,19 @@ static inline void switch_to_extra(struct task_struct *prev, 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. |