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

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Message-ID: <DE8DF0795D48FD4CA783C40EC82923351F0C89@SHSMSX101.ccr.corp.intel.com>
Date:	Fri, 25 May 2012 18:01:04 +0000
From:	"Liu, Jinsong" <jinsong.liu@...el.com>
To:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.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)

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/...

>> 
>>> 
>>>> This patch just do redirection at xen code path, and that would not
>>>> hurt anything to native kernel.
>>> 
>>> My concern is that if we remove /dev/mcelog one day, xen people will
>>> cry.
> 
> Hehe.
> 
> The goal here is to serve the distros so to say. So if the distros
> stop using /dev/mcelog and the /dev/mcelog goes away we won't cry b/c
> well, the user of it has gone away!
> 
> So the moment you remove that, pls CC us so we can remove it too
> and retool to use the MCElogv2.
> 
>> 
>> Don't worry :)
>> Xen people would handle that case (that's not trouble for xen), just
>> notify us is enough. 
>> If kernel really remove /dev/mcelog some day, xen just need simply
>> add 1 line misc_register(&xen_mce_chrdev_device), since currently
>> all other code are xen-self-contained.  
> 
> Well, I will delete it. My customer is distro (Fedora, Debian, Oracle
> and SuSE)- and if the distro is not using it there is not point
> of keeping it.

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