Re: [PATCH 34/34] x86/mm/pti: Add Warning when booting on a PCIE capable CPU

[Waiman Long]

On 03/05/2018 05:26 AM, Joerg Roedel wrote:
> From: Joerg Roedel <jroedel@xxxxxxx>
>
> Warn the user in case the performance can be significantly
> improved by switching to a 64-bit kernel.
>
> Suggested-by: Andy Lutomirski <luto@xxxxxxxxxx>
> Signed-off-by: Joerg Roedel <jroedel@xxxxxxx>
> ---
>  arch/x86/mm/pti.c | 16 ++++++++++++++++
>  1 file changed, 16 insertions(+)
>
> diff --git a/arch/x86/mm/pti.c b/arch/x86/mm/pti.c
> index 3ffd923..8f5aa0d 100644
> --- a/arch/x86/mm/pti.c
> +++ b/arch/x86/mm/pti.c
> @@ -385,6 +385,22 @@ void __init pti_init(void)
>  
>  	pr_info("enabled\n");
>  
> +#ifdef CONFIG_X86_32
> +	if (boot_cpu_has(X86_FEATURE_PCID)) {
> +		/* Use printk to work around pr_fmt() */
> +		printk(KERN_WARNING "\n");
> +		printk(KERN_WARNING "************************************************************\n");
> +		printk(KERN_WARNING "** WARNING! WARNING! WARNING! WARNING! WARNING! WARNING!  **\n");
> +		printk(KERN_WARNING "**                                                        **\n");
> +		printk(KERN_WARNING "** You are using 32-bit PTI on a 64-bit PCID-capable CPU. **\n");
> +		printk(KERN_WARNING "** Your performance will increase dramatically if you     **\n");
> +		printk(KERN_WARNING "** switch to a 64-bit kernel!                             **\n");
> +		printk(KERN_WARNING "**                                                        **\n");
> +		printk(KERN_WARNING "** WARNING! WARNING! WARNING! WARNING! WARNING! WARNING!  **\n");
> +		printk(KERN_WARNING "************************************************************\n");
> +	}
> +#endif
> +
>  	pti_clone_user_shared();
>  	pti_clone_entry_text();
>  	pti_setup_espfix64();

Typo in the patch title: PCIE => PCID.

-Longman