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

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Message-ID: <20091023153027.GA18068@elte.hu>
Date:	Fri, 23 Oct 2009 17:30:27 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Daniel Walker <dwalker@...o99.com>
Cc:	Erwan Velu <erwanaliasr1@...il.com>,
	Jeremy Fitzhardinge <jeremy@...p.org>,
	linux-kernel@...r.kernel.org, x86@...nel.org
Subject: Re: [PATCH] dmi_check_system can generate Warnings when no DMI
	table is present


* Daniel Walker <dwalker@...o99.com> wrote:

> On Fri, 2009-10-23 at 17:03 +0200, Erwan Velu wrote:
> > Daniel Walker a écrit :
> > > [...]
> > > It's your defect, so you can still try to fix it (unless the "xen
> > > people" or someone else beats you to it.) 
> > >
> > > It looks like on a normal system dmi_scan_machine() gets called very
> > > early in setup_arch() arch/x86/kernel/setup.c . A possible good fix
> > > might be to add a dmi_disable() into the dmi driver that just shuts off
> > > dmi, and run that in xen_arch_setup() in arch/x86/xen/setup.c 
> > Could it make sense having this patch (I can work on it) while keeping 
> > my previous patch ?
> > Does it make sense keeping the default return value I've been adding 
> > when no dmi table is found ?
> 
> 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.

	Ingo
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