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

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Message-ID: <4AE1E862.8090109@goop.org>
Date:	Fri, 23 Oct 2009 10:31:14 -0700
From:	Jeremy Fitzhardinge <jeremy@...p.org>
To:	Ingo Molnar <mingo@...e.hu>
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

On 10/23/09 10:04, Ingo Molnar wrote:
>> 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?
>   

The backtraces in the original report showed that the messages were
coming from DMI calls in the PCI init path or i8042_init.  PCI shouldn't
be being called early, and i8042_init is just a normal module_init.

DomU has no DMI (we just put all zeros into the ISA window to catch any
probes), and nothing Xen-specific has any DMI dependencies.  So there
should be no cause to make any premature dmi calls.

It looks like setup_arch() is being missed, but its hard to see how we'd
get very far in that case...

Also, the referenced reports are for distro kernels which may not
contain mainline Xen in the first place (Novell have their own massive
Xen patch stack they dump onto the kernels before shipping, so Xen bug
reports against SuSE kernels don't have any relevance to mainline).  I'd
like to see a boot log of a mainline kernel showing the problem.

    J
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