On Fri, 2018-01-26 at 21:08 +0100, Borislav Petkov wrote:
> 
> --- a/arch/x86/include/asm/processor.h
> +++ b/arch/x86/include/asm/processor.h
> @@ -971,4 +971,8 @@ bool xen_set_default_idle(void);
>  
>  void stop_this_cpu(void *dummy);
>  void df_debug(struct pt_regs *regs, long error_code);
> +
> +#ifdef CONFIG_RETPOLINE
> +void __ibp_barrier(void);
> +#endif
>  #endif /* _ASM_X86_PROCESSOR_H */

Did I already say that needs to live in asm-prototypes.h? And it needs
to be exported to modules, I think.