linux-kernel - Re: [git-pull -tip] x86: cpu

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Message-ID: <20090420111619.GE6670@elte.hu>
Date:	Mon, 20 Apr 2009 13:16:19 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Jaswinder Singh Rajput <jaswinder@...nel.org>
Cc:	x86 maintainers <x86@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Alan Cox <alan@...rguk.ukuu.org.uk>
Subject: Re: [git-pull -tip] x86: cpu_debug patches

* Jaswinder Singh Rajput <jaswinder@...nel.org> wrote:

>  static DEFINE_PER_CPU(struct cpu_cpuX_base, cpu_arr[CPU_REG_ALL_BIT]);
>  static DEFINE_PER_CPU(struct cpu_private *, priv_arr[MAX_CPU_FILES]);
>  static DEFINE_PER_CPU(unsigned, cpu_modelflag);
>  static DEFINE_PER_CPU(int, cpu_priv_count);
> -static DEFINE_PER_CPU(unsigned, cpu_model);
> +
> +/* Storing vendor locally because it is used excessive in this code */
> +static unsigned cpu_vendor;

There's still no need to store it locally - what's wrong with 
cpu_data(cpu) or current_cpu_data?

Also, do we need the per-cpu cpu_modelflag variable too? I'd suggest 
to integrate that kind of enumeration into struct cpuinfo_x86 and 
cpu_info. We often have such kinds of constructs in x86 code:

	c->x86 <= 0x11

So extending your scheme to other code would benefit all code.

Plus this kind of enumeration:

        switch (model) {
        case 0x0501:
        case 0x0502:
        case 0x0504:
                flag = CPU_INTEL_PENTIUM;
                break;
        case 0x0601:
        case 0x0603:
        case 0x0605:
        case 0x0607:
        case 0x0608:
        case 0x060A:
        case 0x060B:
                flag = CPU_INTEL_P6;

The 0x05/0x06 there is already available as the family flag in 
cpuinfo_x86, as cpu_info::x86. The 01,02...0B model portion is also 
already available as cpu_info::x86_model.

[ there's also cpu_info::x86_mask, which gives the stepping. ]

This is what i meant when i said that you needlessly duplicate 
already existing information. You encode/decode it in some weird 
looking way instead of using the already existing, per CPU 
information of cpu_info.

	Ingo
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