linux-kernel - Re: [PATCH] dmi_check_system can generate Warnings when no DMI table is present

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Message-ID: <20091023170428.GA25484@elte.hu>
Date:	Fri, 23 Oct 2009 19:04:28 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Jeremy Fitzhardinge <jeremy@...p.org>
Cc:	Daniel Walker <dwalker@...o99.com>,
	Erwan Velu <erwanaliasr1@...il.com>,
	linux-kernel@...r.kernel.org, x86@...nel.org
Subject: Re: [PATCH] dmi_check_system can generate Warnings when no DMI
	table is present


* Jeremy Fitzhardinge <jeremy@...p.org> wrote:

> On 10/23/09 08:30, Ingo Molnar wrote:
> >> Ingo mentioned that the returning mechanism your adding was left out 
> >> intentionally to catch this error, so I don't think your original 
> >> patch could be included ..
> >>     
> > Yes. That mechanism found a real bug here.
> >
> > Calling the DMI code too early (when the strings are still empty) 
> > can cause silent failures: we wont crash but we might miss to act on 
> > DMI quirks.
> 
> Yes.  There's nothing preventing the DMI subsystem from being 
> initialized under Xen; in fact we rely on it in a dom0 kernel (which 
> does have access to the DMI tables).  I don't know what the underlying 
> bug in the original report is, but there's more to it than failing to 
> init DMI.

yeah. It's probably some init ordering problem - some version of Xen 
calling into the DMI code too early. It probably doesnt even matter in 
practice as we rarely rely on DMI details in Xen guests, right?

	Ingo
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