Re: [PATCHv3 13/13] x86/mm: Offset boot-time paging mode switching cost

[Andi Kleen]

> diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
> index 077e8b45784c..6f92e61d35ac 100644
> --- a/arch/x86/entry/entry_64.S
> +++ b/arch/x86/entry/entry_64.S
> @@ -274,7 +274,7 @@ return_from_SYSCALL_64:
>  	 * depending on paging mode) in the address.
>  	 */
>  #ifdef CONFIG_X86_5LEVEL
> -	testl	$1, p4d_folded(%rip)
> +	testl	$1, __p4d_folded(%rip)
>  	jnz	1f


You can use

	ALTERNATIVE "", "jmp 1f", X86_FEATURE_LA57

to do the patching.

-Andi