linux-kernel - Re: [Patch V1 3/7] x86/microcode/core: Move microcode

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Date:   Mon, 5 Dec 2022 09:05:54 -0800
From:   Ashok Raj <ashok.raj@...el.com>
To:     Borislav Petkov <bp@...en8.de>
CC:     X86-kernel <x86@...nel.org>,
        LKML Mailing List <linux-kernel@...r.kernel.org>,
        Dave Hansen <dave.hansen@...el.com>,
        "Tony Luck" <tony.luck@...el.com>, <alison.schofield@...el.com>,
        <reinette.chatre@...el.com>, Ashok Raj <ashok.raj@...el.com>
Subject: Re: [Patch V1 3/7] x86/microcode/core: Move microcode_check() to
 cpu/microcode/core.c

On Mon, Dec 05, 2022 at 05:25:17PM +0100, Borislav Petkov wrote:
> On Tue, Nov 29, 2022 at 01:08:28PM -0800, Ashok Raj wrote:
> > microcode_check() is only called from microcode/core.c. Move it and make
> > it static to prepare for upcoming fix of false negative when checking CPU
> > features after a microcode update.
> 
> So this function is there in cpu/common.c because it uses CPU facilities
> like cpuinfo_x86 and get_cpu_cap() so the logical place was there.
> So that I don't have to export a bunch of things but rather have the
> microcode loader call into it only.
> 
> Your next patch is using more of those CPU-specific facilities so
> "bleeding" them into the microcode loader looks like the wrong way
> around.
> 
> get_cpu_cap() deals with all those c->x86_capability arrays and other
> functions which do that, should be there too.

I was trying to move this similar to how x86_read_arch_cap_msr()
moved from x86/kernel/cpu/cpu.h -> asm/cpu.h.

Keeping the usage local since there is just one caller to microcode_check()
but there are other users of get_cpu_cap() like in
arch/x86/xen/enlighten_pv.c which seems to be reaching out to
../kernel/cpu/cpu.h. 

That said, what you say also makes sense. I'm fine with what you decide how
this should look.

Cheers
Ashok