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

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Message-ID: <4AE1E06B.7010101@goop.org>
Date:	Fri, 23 Oct 2009 09:57:15 -0700
From:	Jeremy Fitzhardinge <jeremy@...p.org>
To:	Erwan Velu <erwanaliasr1@...il.com>
CC:	linux-kernel@...r.kernel.org, x86@...nel.org,
	Ingo Molnar <mingo@...hat.com>,
	Daniel Walker <dwalker@...sta.com>
Subject: Re: [PATCH] dmi_check_system can generate Warnings when no DMI table
 is present

On 10/23/09 02:34, Erwan Velu wrote:
> When running the Linux Kernel, on some systems that doesn't have any
> DMI table (like a Xen domU), some dmi_* calls can generates Warnings
> like :
>
>> / WARNING: at /usr/src/linux-2.6.29.1/drivers/firmware/dmi_scan.c:425/
>> / dmi_matches+0x7e/0x80()/
>> / dmi check: not initialized yet/
>
> Some users reported this error :
> http://lists.xensource.com/archives/html/xen-users/2009-04/msg00128.html
> https://qa.mandriva.com/show_bug.cgi?id=54775

I don't think either of those reports are for kernels with upstream Xen
support.  Novell reimplements their own Xen support in their kernels; I
don't know whether Mandriva repackages the Novell kernel or not, but
some distros do.

> When the kernel is compiled with CONFIG_DMI, dmi_check_system(),
> dmi_first_match(), dmi_name_in_vendors(), dmi_find_device(),
> dmi_get_date(), dmi_match() calls doesn't check the status of the
> dmi_available variable.
>
> When this functions are called and if no valid dmi table has been
> found, this pretty simple patch just return the default values
> returned when CONFIG_DMI isn't set.
>
> This patch applies to the lastest git tree.
> I'm CCing the x86 maintainers as I can't find any maintainer of
> drivers/firmware/dmi.

This doesn't make any sense to me.  dmi_scan_machine() should be called
in the normal place under Xen, so it will initialize the DMI subsystem. 
There won't be any DMI table in domU, but that's OK.

Please include a full boot log showing the problem. "DMI not present or
invalid" should always be present in the kernel log.

    J
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