linux-kernel - Re: [Xen-devel] [PATCH 1/3] xen/mce: Add mcelog support for Xen platform (v2)

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Message-ID: <20120525180303.GB27280@phenom.dumpdata.com>
Date:	Fri, 25 May 2012 14:03:03 -0400
From:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
To:	"Liu, Jinsong" <jinsong.liu@...el.com>
Cc:	Borislav Petkov <bp@...64.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"Luck, Tony" <tony.luck@...el.com>,
	"xen-devel@...ts.xensource.com" <xen-devel@...ts.xensource.com>
Subject: Re: [Xen-devel] [PATCH 1/3] xen/mce: Add mcelog support for Xen
 platform (v2)

On Fri, May 25, 2012 at 06:01:04PM +0000, Liu, Jinsong wrote:
> Konrad Rzeszutek Wilk wrote:
> >>>> The reason is, if we do so, it would be covered by native
> >>>> misc_register(&mce_chrdev_device) later when native kernel init
> >>>> (xen init first and then start native kernel).
> >>>> Under such case, if linux running under xen platform, /dev/mcelog
> >>>> point to vcpu, that's pointless since it cannot get any mcelog from
> >>>> physical cpu (which owned by xen).
> >>>> 
> >>>> Yes, we can use another misc device like /dev/xen-mcelog, w/
> >>>> another device minor like 226, but that's not good for userspace
> >>>> mcelog tools. As far as I know, Novell mcelog use unified
> >>>> /dev/mcelog interface for linux running under either bare metal or
> >>>> xen platform. 
> >>> 
> >>> Maybe create a symlink in /dev/mcelog pointing to /dev/xen-mcelog?
> >>> 
> >>> That should solve it.
> >> 
> >> Kernel has created a file /dev/mcelog no matter running at native or
> >> xen platform. 
> >> If xen try to mask kernel creating /dev/mcelog, that would be
> >> harmful to native kernel. 
> > 
> > Huh? The Xen code won't run under native kernel so how will it mask
> > it? 
> 
> Hmm, I mean 'xen related code' of linux kernel, e.g. drivers/xen/...

OK? I am still not getting what you are saying. Could you please
rephrase it?

Why would disabling the generic "/dev/mcelog" and use your version
of "/dev/mcelog" be harmful? I think this is what Boris was hinting
as the proper way of doing it.

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