linux-kernel - Re: [PATCH] x86: Report Intel platform

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Message-ID: <87shw6plxr.fsf@tassilo.jf.intel.com>
Date:	Tue, 21 Jun 2016 09:05:04 -0700
From:	Andi Kleen <andi@...stfloor.org>
To:	x86@...nel.org
Cc:	linux-kernel@...r.kernel.org, hmh@....eng.br
Subject: Re: [PATCH] x86: Report Intel platform_id in /proc/cpuinfo

Andi Kleen <andi@...stfloor.org> writes:

Ping! Any comments on this patch?

> From: Andi Kleen <ak@...ux.intel.com>
>
> We have a need to distinguish systems based on their platform ID.
> For example this is useful to distinguish systems with L4 cache
> versus ones without.
>
> There is a 3 bit identifier (also called processor flags) in
> the IA32_PLATFORM_ID MSR that can give a more fine grained
> identification of the CPU than just the model number/stepping.
>
> IA32_PLATFORM_ID is architectural.
>
> The processor flags are already used in the microcode driver.
> The MSR can be also accessed through /dev/cpu/*/msr, but that
> requires root and is awkward.
>
> This patch just exports the value retrieved by the microcode
> driver in /proc/cpuinfo. If the microcode driver is disabled
> it won't be shown, but that seems reasonable.
>
> v2: Handle 0 platform_id. Fix commit message.
> Cc: hmh@....eng.br
> Signed-off-by: Andi Kleen <ak@...ux.intel.com>
> ---
>  arch/x86/include/asm/processor.h      | 2 ++
>  arch/x86/kernel/cpu/microcode/intel.c | 2 ++
>  arch/x86/kernel/cpu/proc.c            | 2 ++
>  3 files changed, 6 insertions(+)
>
> diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
> index 20c11d1..270209c 100644
> --- a/arch/x86/include/asm/processor.h
> +++ b/arch/x86/include/asm/processor.h
> @@ -136,6 +136,8 @@ struct cpuinfo_x86 {
>  	/* Index into per_cpu list: */
>  	u16			cpu_index;
>  	u32			microcode;
> +	u32			platform_id;
> +	u8			has_platform_id;
>  };
>  
>  #define X86_VENDOR_INTEL	0
> diff --git a/arch/x86/kernel/cpu/microcode/intel.c b/arch/x86/kernel/cpu/microcode/intel.c
> index ee81c54..bcd3f59 100644
> --- a/arch/x86/kernel/cpu/microcode/intel.c
> +++ b/arch/x86/kernel/cpu/microcode/intel.c
> @@ -812,6 +812,8 @@ static int collect_cpu_info(int cpu_num, struct cpu_signature *csig)
>  		/* get processor flags from MSR 0x17 */
>  		rdmsr(MSR_IA32_PLATFORM_ID, val[0], val[1]);
>  		csig->pf = 1 << ((val[1] >> 18) & 7);
> +		cpu_data(cpu_num).platform_id = (val[1] >> 18) & 7;
> +		cpu_data(cpu_num).has_platform_id = true;
>  	}
>  
>  	csig->rev = c->microcode;
> diff --git a/arch/x86/kernel/cpu/proc.c b/arch/x86/kernel/cpu/proc.c
> index 18ca99f..5345d50 100644
> --- a/arch/x86/kernel/cpu/proc.c
> +++ b/arch/x86/kernel/cpu/proc.c
> @@ -76,6 +76,8 @@ static int show_cpuinfo(struct seq_file *m, void *v)
>  		seq_puts(m, "stepping\t: unknown\n");
>  	if (c->microcode)
>  		seq_printf(m, "microcode\t: 0x%x\n", c->microcode);
> +	if (c->has_platform_id)
> +		seq_printf(m, "platform_id\t: %d\n", c->platform_id);
>  
>  	if (cpu_has(c, X86_FEATURE_TSC)) {
>  		unsigned int freq = cpufreq_quick_get(cpu);

-- 
ak@...ux.intel.com -- Speaking for myself only