linux-kernel - Re: [PATCH] x86, cpuinfo fix cpu_data(0) x86_model

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Message-ID: <20150518194538.GD23618@pd.tnic>
Date:	Mon, 18 May 2015 21:45:38 +0200
From:	Borislav Petkov <bp@...en8.de>
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>,
	Denys Vlasenko <dvlasenk@...hat.com>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	Peter P Waskiewicz Jr <peter.p.waskiewicz.jr@...el.com>,
	Igor Mammedov <imammedo@...hat.com>,
	Fenghua Yu <fenghua.yu@...el.com>
Subject: Re: [PATCH] x86, cpuinfo fix cpu_data(0) x86_model_id field
 truncation

On Mon, May 18, 2015 at 02:21:00PM -0400, 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

I'd actually prefer this much simpler patch:

---
diff --git a/arch/x86/kernel/cpu/proc.c b/arch/x86/kernel/cpu/proc.c
index e7d8c7608471..d215e9b26567 100644
--- a/arch/x86/kernel/cpu/proc.c
+++ b/arch/x86/kernel/cpu/proc.c
@@ -67,7 +67,7 @@ static int show_cpuinfo(struct seq_file *m, void *v)
 		   c->x86_vendor_id[0] ? c->x86_vendor_id : "unknown",
 		   c->x86,
 		   c->x86_model,
-		   c->x86_model_id[0] ? c->x86_model_id : "unknown");
+		   c->x86_model_id[0] ? strim(c->x86_model_id) : "unknown");
 
 	if (c->x86_mask || c->cpuid_level >= 0)
 		seq_printf(m, "stepping\t: %d\n", c->x86_mask);
---

-- 
Regards/Gruss,
    Boris.

ECO tip #101: Trim your mails when you reply.
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