linux-kernel - Re: [patch V2 04/28] x86/speculation: Reorganize cpu_show

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Date:   Thu, 29 Nov 2018 09:29:23 -0500
From:   Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     LKML <linux-kernel@...r.kernel.org>, x86@...nel.org,
        Peter Zijlstra <peterz@...radead.org>,
        Andy Lutomirski <luto@...nel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Jiri Kosina <jkosina@...e.cz>,
        Tom Lendacky <thomas.lendacky@....com>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        David Woodhouse <dwmw@...zon.co.uk>,
        Tim Chen <tim.c.chen@...ux.intel.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Casey Schaufler <casey.schaufler@...el.com>,
        Asit Mallick <asit.k.mallick@...el.com>,
        Arjan van de Ven <arjan@...ux.intel.com>,
        Jon Masters <jcm@...hat.com>,
        Waiman Long <longman9394@...il.com>,
        Greg KH <gregkh@...uxfoundation.org>,
        Dave Stewart <david.c.stewart@...el.com>,
        Kees Cook <keescook@...omium.org>
Subject: Re: [patch V2 04/28] x86/speculation: Reorganize cpu_show_common()

On Sun, Nov 25, 2018 at 07:33:32PM +0100, Thomas Gleixner wrote:
> The Spectre V2 printout in cpu_show_common() handles conditionals for the
> various mitigation methods directly in the sprintf() argument list. That's
> hard to read and will become unreadable if more complex decisions need to
> be made for a particular method.
> 
> Move the conditionals for STIBP and IBPB string selection into helper
> functions, so they can be extended later on.
> 

Yeeey!


Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>

Thank you!
> Signed-off-by: Tim Chen <tim.c.chen@...ux.intel.com>
> Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
> 
> ---
>  arch/x86/kernel/cpu/bugs.c |   20 ++++++++++++++++++--
>  1 file changed, 18 insertions(+), 2 deletions(-)
> 
> --- a/arch/x86/kernel/cpu/bugs.c
> +++ b/arch/x86/kernel/cpu/bugs.c
> @@ -844,6 +844,22 @@ static ssize_t l1tf_show_state(char *buf
>  }
>  #endif
>  
> +static char *stibp_state(void)
> +{
> +	if (x86_spec_ctrl_base & SPEC_CTRL_STIBP)
> +		return ", STIBP";
> +	else
> +		return "";
> +}
> +
> +static char *ibpb_state(void)
> +{
> +	if (boot_cpu_has(X86_FEATURE_USE_IBPB))
> +		return ", IBPB";
> +	else
> +		return "";
> +}
> +
>  static ssize_t cpu_show_common(struct device *dev, struct device_attribute *attr,
>  			       char *buf, unsigned int bug)
>  {
> @@ -865,9 +881,9 @@ static ssize_t cpu_show_common(struct de
>  
>  	case X86_BUG_SPECTRE_V2:
>  		return sprintf(buf, "%s%s%s%s%s%s\n", spectre_v2_strings[spectre_v2_enabled],
> -			       boot_cpu_has(X86_FEATURE_USE_IBPB) ? ", IBPB" : "",
> +			       ibpb_state(),
>  			       boot_cpu_has(X86_FEATURE_USE_IBRS_FW) ? ", IBRS_FW" : "",
> -			       (x86_spec_ctrl_base & SPEC_CTRL_STIBP) ? ", STIBP" : "",
> +			       stibp_state(),
>  			       boot_cpu_has(X86_FEATURE_RSB_CTXSW) ? ", RSB filling" : "",
>  			       spectre_v2_module_string());
>  
> 
>