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

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Message-ID: <20120524184947.GA28338@phenom.dumpdata.com>
Date:	Thu, 24 May 2012 14:49:47 -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)

> >>>> -static struct miscdevice mce_chrdev_device = {
> >>>> +struct miscdevice mce_chrdev_device = {
> >>>>  	MISC_MCELOG_MINOR,
> >>>>  	"mcelog",
> >>>>  	&mce_chrdev_ops,
> >>> 
> >>> You're still reusing those - pls, define your own 'struct miscdevice
> >>> mce_chrdev_device' in drivers/xen/ or somewhere convenient and
> >>> your own mce_chrdev_ops. The only thing you should be touching in
> >>> arch/x86/.../mcheck/ is the export of MISC_MCELOG_MINOR.
> >>> 
> >>> Thanks.
> >> 
> >> I'm *not* reuse native code.
> >> I have defined 'struct miscdevice xen_mce_chrdev_device' in
> >> drivers/xen, and I also implement xen_mce_chrdev_ops, they are all
> >> xen-self-contained.  
> >> 
> >> The patch just redirect native mce_chrdev_device to
> >> xen_mce_chrdev_device when running under xen environment. 
> >> It didn't change any native code (except just cancel
> >> mce_chrdev_device 'static'), and will not break native logic. 
> > 
> > Why are you doing that?
> > 
> > Why don't you do
> > 
> > 	misc_register(&xen_mce_chrdev_device);
> > 
> > in xen_early_init_mcelog() ?
> > 
> > This way there'll be no arch/x86/ dependencies at all.
> 
> 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).

Won't the second registration (so the original one) of the major fail? So the mce_log
would just error out since somebody already registered?
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