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Subject: Re: [PATCH] iommu virtual merge no longer experimental
From: Benjamin Herrenschmidt <benh@au1.ibm.com>
To: Linas Vepstas <linas@austin.ibm.com>
In-Reply-To: <20070717160935.GE5771@austin.ibm.com>
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Date: Wed, 18 Jul 2007 06:56:26 +1000
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Cc: linuxppc-dev@ozlabs.org, paulus@samba.org,
	Arnd Bergmann <arnd.bergmann@de.ibm.com>, Tim Schimke <tschimke@us.ibm.com>
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On Tue, 2007-07-17 at 11:09 -0500, Linas Vepstas wrote:
> Per conversations with BenH, iommu virtual merging should no longer
> be considered to be an "experimental" feature. In particular, 
> CONFIG_VMERGE has been set to "y" in te defconfigs for quite a while.
> 
> Signed-off-by: Linas Vepstas <linas@austin.ibm.com>

Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

> ----
>  arch/powerpc/Kconfig |   11 ++++++-----
>  1 file changed, 6 insertions(+), 5 deletions(-)
> 
> Index: linux-2.6.22-git2/arch/powerpc/Kconfig
> ===================================================================
> --- linux-2.6.22-git2.orig/arch/powerpc/Kconfig	2007-07-08 18:32:17.000000000 -0500
> +++ linux-2.6.22-git2/arch/powerpc/Kconfig	2007-07-17 11:08:18.000000000 -0500
> @@ -430,16 +430,17 @@ config MATH_EMULATION
>  	  instructions to run.
>  
>  config IOMMU_VMERGE
> -	bool "Enable IOMMU virtual merging (EXPERIMENTAL)"
> -	depends on EXPERIMENTAL && PPC64
> -	default n
> +	bool "Enable IOMMU virtual merging"
> +	depends on PPC64
> +	default y
>  	help
>  	  Cause IO segments sent to a device for DMA to be merged virtually
>  	  by the IOMMU when they happen to have been allocated contiguously.
>  	  This doesn't add pressure to the IOMMU allocator. However, some
>  	  drivers don't support getting large merged segments coming back
> -	  from *_map_sg(). Say Y if you know the drivers you are using are
> -	  properly handling this case.
> +	  from *_map_sg().
> +
> +	  Most drivers don't have this problem; it is safe to say Y here.
>  
>  config HOTPLUG_CPU
>  	bool "Support for enabling/disabling CPUs"