linux-kernel - Re: [PATCH 2/2] x86, apic: Disable BSP if boot cpu is AP

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Message-ID: <20130904061221.GA17791@x1.alien8.de>
Date:	Wed, 4 Sep 2013 08:12:22 +0200
From:	Borislav Petkov <bp@...en8.de>
To:	HATAYAMA Daisuke <d.hatayama@...fujitsu.com>
Cc:	ebiederm@...ssion.com, vgoyal@...hat.com,
	akpm@...ux-foundation.org, hpa@...ux.intel.com,
	kexec@...ts.infradead.org, linux-kernel@...r.kernel.org,
	jingbai.ma@...com
Subject: Re: [PATCH 2/2] x86, apic: Disable BSP if boot cpu is AP

On Mon, Sep 02, 2013 at 06:42:44PM +0900, HATAYAMA Daisuke wrote:
> The reason why I don't lookup BSP flag in MSR is that it's impossible.
> To read MSR of some CPU, we need to use rdmsr instruction on the CPU.
> However, in case of this issue, the BSP is halting or running in
> the kdump 1st kernel.

Yes, and on the AP, that flag would be cleared which makes it not a BSP.

> A whole explanation is written in the patch description.

Those tend to get lost in git history when a bunch of whitespace jerk
offs appear ontop. So a nicely written comment in the code could be very
helpful.

Thanks.

-- 
Regards/Gruss,
Boris.
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