Date: Thu, 7 Jun 2007 16:58:39 -0700
From: Andrew Morton <akpm@linux-foundation.org>
To: anil.s.keshavamurthy@intel.com
Cc: linux-kernel@vger.kernel.org, ak@suse.de, gregkh@suse.de, muli@il.ibm.com,
       asit.k.mallick@intel.com, suresh.b.siddha@intel.com,
       arjan@linux.intel.com, ashok.raj@intel.com, shaohua.li@intel.com,
       davem@davemloft.net
Subject: Re: [Intel-IOMMU 07/10] Intel iommu cmdline option - forcedac
Message-Id: <20070607165839.acf76694.akpm@linux-foundation.org>
In-Reply-To: <20070606190042.930671000@askeshav-devel.jf.intel.com>
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	<20070606190042.930671000@askeshav-devel.jf.intel.com>
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On Wed, 06 Jun 2007 11:57:05 -0700
anil.s.keshavamurthy@intel.com wrote:

> --- linux-2.6.22-rc3.orig/Documentation/kernel-parameters.txt	2007-06-04 12:40:29.000000000 -0700
> +++ linux-2.6.22-rc3/Documentation/kernel-parameters.txt	2007-06-04 12:40:41.000000000 -0700
> @@ -785,6 +785,13 @@
>  			bypassed by not enabling DMAR with this option. In
>  			this case, gfx device will use physical address for
>  			DMA.
> +		forcedac

You want
		forcedac [X86-64]

> +			With this option iommu will not optimize to look
> +			for io virtual address below 32 bit forcing dual
> +			address cycle on pci bus for cards supporting greater
> +			than 32 bit addressing. The default is to look
> +			for translation below 32 bit and if not available
> +			then look in the higher range.

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