linux-kernel - Re: [PATCH] x86, cpuinfo remove cpu_data x86_model

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Message-ID: <555A6215.1050907@redhat.com>
Date:	Mon, 18 May 2015 18:05:09 -0400
From:	Prarit Bhargava <prarit@...hat.com>
To:	Prarit Bhargava <prarit@...hat.com>
CC:	linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
	Andy Lutomirski <luto@...capital.net>,
	Borislav Petkov <bp@...en8.de>,
	Denys Vlasenko <dvlasenk@...hat.com>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	Igor Mammedov <imammedo@...hat.com>,
	Fenghua Yu <fenghua.yu@...el.com>
Subject: Re: [PATCH] x86, cpuinfo remove cpu_data x86_model_id trailing whitespace



On 05/18/2015 06:01 PM, Prarit Bhargava wrote:
> When comparing 'model name' fields in /proc/cpuinfo it was noticed that
> a simple test comparing the model name fields was failing.  After some
> simple investigation it was noticed that, in fact, the model name fields
> are different for each processor.  Processor 0's model name field had
> white space removed, while the other processors did not.
> 
> Another way of seeing this behaviour is to convert spaces into underscores
> in the output of /proc/cpuinfo,
> 
> [thetango@...rit ~]# grep "^model name" /proc/cpuinfo | uniq -c | sed 's/\ /_/g'
> ______1_model_name      :_AMD_Opteron(TM)_Processor_6272
> _____63_model_name      :_AMD_Opteron(TM)_Processor_6272_________________
> 
> which shows two different model name fields even though they should be the
> same.
> 
> This occurs because the kernel calls strim() on cpu 0's x86_model_id field
> to output a pretty message to the console in print_cpu_info(), and as a
> result truncates the whitespace at the end of the x86_model_id field.
> 
> The x86_model_id field should be the same for the same processors.  This
> patch removes traliing space on every processor's x86_model_id field to make
> them consistent and maintains the correct output for print_cpu_info():
> 
> smpboot: CPU0: AMD Opteron(TM) Processor 6272 (fam: 15, model: 01, stepping: 02)
> 
> The x86_model_id field is correct and has no whitespace across all processors:
> 
> [thetango@...rit ~]# grep "^model name" /proc/cpuinfo | uniq -c | sed 's/\ /_/g'
> _____64_model_name      :_AMD_Opteron(TM)_Processor_6272
> 

Nack this ... hpa has suggested that I backwards search from the 48th character
for the first non-null ... I'll put together a new patch.

P.

> Signed-off-by: Prarit Bhargava <prarit@...hat.com>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: Ingo Molnar <mingo@...hat.com>
> Cc: "H. Peter Anvin" <hpa@...or.com>
> Cc: x86@...nel.org
> Cc: Andy Lutomirski <luto@...capital.net>
> Cc: Borislav Petkov <bp@...en8.de>
> Cc: Denys Vlasenko <dvlasenk@...hat.com>
> Cc: Dave Hansen <dave.hansen@...ux.intel.com>
> Cc: Igor Mammedov <imammedo@...hat.com>
> Cc: Fenghua Yu <fenghua.yu@...el.com>
> ---
>  arch/x86/kernel/cpu/common.c |    3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
> index a62cf04..fa771bb 100644
> --- a/arch/x86/kernel/cpu/common.c
> +++ b/arch/x86/kernel/cpu/common.c
> @@ -443,6 +443,7 @@ static void get_model_name(struct cpuinfo_x86 *c)
>  		while (q <= &c->x86_model_id[48])
>  			*q++ = '\0';	/* Zero-pad the rest */
>  	}
> +	strim(c->x86_model_id);
>  }
>  
>  void cpu_detect_cache_sizes(struct cpuinfo_x86 *c)
> @@ -1122,7 +1123,7 @@ void print_cpu_info(struct cpuinfo_x86 *c)
>  		printk(KERN_CONT "%s ", vendor);
>  
>  	if (c->x86_model_id[0])
> -		printk(KERN_CONT "%s", strim(c->x86_model_id));
> +		printk(KERN_CONT "%s", c->x86_model_id);
>  	else
>  		printk(KERN_CONT "%d86", c->x86);
>  
> 
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