Commit adafb98d authored May 26, 2015 by Prarit Bhargava Committed by Ingo Molnar May 27, 2015

x86/cpu: Strip any /proc/cpuinfo model name field whitespace



When comparing the 'model name' field of each core in
/proc/cpuinfo it was noticed that there is a whitespace
difference between the cores' model names.

After some quick investigation it was noticed that the model
name fields were actually different -- processor 0's model name
field had trailing whitespace 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@prarit ~]# 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 the discrepancy.

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 strips the whitespace at the
end of the ->x86_model_id field.

But, the ->x86_model_id field should be the same for the all
identical CPUs in the box. Thus, we need to remove both leading
and trailing whitespace.

As a result, the print_cpu_info() output looks like

  smpboot: CPU0: AMD Opteron(TM) Processor 6272 (fam: 15, model: 01, stepping: 02)

and the x86_model_id field is correct on all processors on AMD
platforms:

  _____64_model_name      :_AMD_Opteron(TM)_Processor_6272

Output is still correct on an Intel box:

  ____144_model_name      :_Intel(R)_Xeon(R)_CPU_E7-8890_v3_@_2.50GHz

Signed-off-by: Prarit Bhargava <prarit@redhat.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Igor Mammedov <imammedo@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1432050210-32036-1-git-send-email-prarit@redhat.com
Link: http://lkml.kernel.org/r/1432628901-18044-15-git-send-email-bp@alien8.de


Signed-off-by: Ingo Molnar <mingo@kernel.org>

parent b9d16a2a

arch/x86/kernel/cpu/common.c

+4 −13

Original line number	Diff line number	Diff line
		@@ -419,7 +419,6 @@ static const struct cpu_dev *cpu_devs[X86_VENDOR_NUM] = {};
		static void get_model_name(struct cpuinfo_x86 *c)
		{
		unsigned int *v;
		char p, q;

		if (c->extended_cpuid_level < 0x80000004)
		return;
		@@ -431,18 +430,10 @@ static void get_model_name(struct cpuinfo_x86 *c)
		c->x86_model_id[48] = 0;

		/*
		* Intel chips right-justify this string for some dumb reason;
		* undo that brain damage:
		* Remove leading whitespace on Intel processors and trailing
		* whitespace on AMD processors.
		*/
		p = q = &c->x86_model_id[0];
		while (*p == ' ')
		p++;
		if (p != q) {
		while (*p)
		q++ = p++;
		while (q <= &c->x86_model_id[48])
		q++ = '\0'; / Zero-pad the rest */
		}
		memmove(c->x86_model_id, strim(c->x86_model_id), 48);
		}

		void cpu_detect_cache_sizes(struct cpuinfo_x86 *c)
		@@ -1122,7 +1113,7 @@ 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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