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

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Message-ID: <20120524191039.GB28338@phenom.dumpdata.com>
Date:	Thu, 24 May 2012 15:10:39 -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)

> >> 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?
> 
> > 
> >> 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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