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

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Message-ID: <DE8DF0795D48FD4CA783C40EC82923351ED978@SHSMSX101.ccr.corp.intel.com>
Date:	Thu, 24 May 2012 16:52:35 +0000
From:	"Liu, Jinsong" <jinsong.liu@...el.com>
To:	Borislav Petkov <bp@...64.org>
CC:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	"Luck, Tony" <tony.luck@...el.com>,
	"xen-devel@...ts.xensource.com" <xen-devel@...ts.xensource.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH 1/3] xen/mce: Add mcelog support for Xen platform (v2)

Borislav Petkov wrote:
> On Thu, May 24, 2012 at 04:15:02PM +0000, Liu, Jinsong 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.

> 
>> 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.

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.

Thanks,
Jinsong

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