linux-kernel - Re: [PATCH] x86: always select SWIOTLB on x86

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Message-Id: <20081119144238W.fujita.tomonori@lab.ntt.co.jp>
Date:	Wed, 19 Nov 2008 14:41:53 +0900
From:	FUJITA Tomonori <fujita.tomonori@....ntt.co.jp>
To:	joerg.roedel@....com
Cc:	mingo@...hat.com, tglx@...utronix.de, linux-kernel@...r.kernel.org,
	iommu@...ts.linux-foundation.org, hawk@...-linux.org,
	stable@...nel.org
Subject: Re: [PATCH] x86: always select SWIOTLB on x86_64

On Tue, 18 Nov 2008 12:44:21 +0100
Joerg Roedel <joerg.roedel@....com> wrote:

> Impact: fixes korg bugzilla 11980
> 
> A kernel for a 64bit x86 system should always contain the swiotlb code
> in case it is booted on a machine without any hardware IOMMU supported
> by the kernel and more than 4GB of RAM. This patch changes Kconfig to
> always compile swiotlb into the kernel for x86_64.

Yeah, as I wrote in a different thread, I think that it makes sense to
enable SWIOTLB at all times:

http://marc.info/?l=linux-kernel&m=122593287501949&w=2

An option asking an user if he has more than 4GB RAM or not, doesn't
make sense much.

BTW, you can also remove the help description, right?
 
> ---
>  arch/x86/Kconfig |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index 93224b5..669c6d5 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -566,7 +566,7 @@ config AMD_IOMMU
>  
>  # need this always selected by IOMMU for the VIA workaround
>  config SWIOTLB
> -	bool
> +	def_bool y if X86_64
>  	help
>  	  Support for software bounce buffers used on x86-64 systems
>  	  which don't have a hardware IOMMU (e.g. the current generation
> -- 
> 1.5.6.4
> 
> 
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