Re: [Intel-IOMMU 07/10] Intel iommu cmdline option - forcedac

[Andrew Morton]

On Wed, 06 Jun 2007 11:57:05 -0700
anil.s.keshavamurthy@xxxxxxxxx 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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