linux-kernel - Re: 2.6.22-rc6-mm1 Intel DMAR crash on AMD x86

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Date:	Fri, 29 Jun 2007 12:23:43 -0400
From:	Muli Ben-Yehuda <muli@...ibm.com>
To:	"Keshavamurthy, Anil S" <anil.s.keshavamurthy@...el.com>
Cc:	Robert Hancock <hancockr@...w.ca>, Zan Lynx <zlynx@....org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, "Raj, Ashok" <ashok.raj@...el.com>
Subject: Re: 2.6.22-rc6-mm1 Intel DMAR crash on AMD x86_64

On Fri, Jun 29, 2007 at 08:28:58AM -0700, Keshavamurthy, Anil S wrote:

> Here is the revised patch of the above.
> Andrew, please add this fix to
> +intel-iommu-dmar-detection-and-parsing-logic.patch
> ------------------------------------------------
> 
> Check for dmar_tbl pointer as this can be NULL on 
> systems with no Intel VT-d support.
> 
> Signed-off-by: Anil S Keshavamurthy <anil.s.keshavamurthy@...el.com>
> 
> ---
>  drivers/pci/dmar.c |    4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> Index: linux-2.6.22-rc4-mm2/drivers/pci/dmar.c
> ===================================================================
> --- linux-2.6.22-rc4-mm2.orig/drivers/pci/dmar.c	2007-06-29 07:43:43.000000000 -0700
> +++ linux-2.6.22-rc4-mm2/drivers/pci/dmar.c	2007-06-29 07:46:25.000000000 -0700
> @@ -260,6 +260,8 @@
>  	int ret = 0;
>  
>  	dmar = (struct acpi_table_dmar *)dmar_tbl;
> +	if (!dmar)
> +		return -ENODEV;
>  
>  	if (!dmar->width) {
>  		printk (KERN_WARNING PREFIX "Zero: Invalid DMAR haw\n");
> @@ -301,7 +303,7 @@
>  
>  	parse_dmar_table();
>  	if (list_empty(&dmar_drhd_units)) {
> -		printk(KERN_ERR PREFIX "No DMAR devices found\n");
> +		printk(KERN_INFO PREFIX "No DMAR devices found\n");
>  		return -ENODEV;
>  	}
>  	return 0;

The convention is to print a KERN_DEBUG message if hardware is not
found when probing it, otherwise the boot messages become cluttered
with lots of "$FOO not found".

Cheers,
Muli
-
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