linux-kernel - Re: [PATCH 1/2] x86/intel: introduce platform

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Date:   Mon, 15 Jan 2018 11:07:40 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     Jia Zhang <zhang.jia@...ux.alibaba.com>
Cc:     tony.luck@...el.com, mingo@...hat.com, hpa@...or.com,
        tglx@...utronix.de, x86@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] x86/intel: introduce platform_id

On Mon, Jan 15, 2018 at 01:43:22PM +0800, Jia Zhang wrote:
> Platform ID retrieved from MSR_IA32_PLATFORM_ID may be used as
> a filtration condition in some cases.
> 
> Signed-off-by: Jia Zhang <zhang.jia@...ux.alibaba.com>
> ---
>  arch/x86/include/asm/processor.h | 1 +
>  arch/x86/kernel/cpu/intel.c      | 7 +++++++
>  2 files changed, 8 insertions(+)
> 
> diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
> index d3a67fb..c0b4d47 100644
> --- a/arch/x86/include/asm/processor.h
> +++ b/arch/x86/include/asm/processor.h
> @@ -133,6 +133,7 @@ struct cpuinfo_x86 {
>  	u16			cpu_index;
>  	u32			microcode;
>  	unsigned		initialized : 1;
> +	u8			platform_id;

Platform ID in cpuinfo?

Nope, I don't think so.

>  } __randomize_layout;
>  
>  struct cpuid_regs {
> diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c
> index b1af220..cee0554 100644
> --- a/arch/x86/kernel/cpu/intel.c
> +++ b/arch/x86/kernel/cpu/intel.c
> @@ -229,6 +229,13 @@ static void early_init_intel(struct cpuinfo_x86 *c)
>  	}
>  
>  	check_mpx_erratum(c);
> +
> +	if ((c->x86 > 6) || (c->x86_model >= 5)) {
> +		u32 val[2];
> +
> +		rdmsr(MSR_IA32_PLATFORM_ID, val[0], val[1]);
> +		c->platform_id = 1 << ((val[1] >> 18) & 7);
> +	}

collect_cpu_info() in arch/x86/kernel/cpu/microcode/intel.c already does
that so you already have that info without duplicating it.

-- 
Regards/Gruss,
    Boris.

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