Re: [tip:x86/mm] x86, mm: Allow ZONE_DMA to be configurable

[Borislav Petkov]

On Mon, May 16, 2011 at 11:13:07PM +0000, tip-bot for David Rientjes wrote:
> Commit-ID:  dc382fd5bcca7098a984705ed6ac880f539d068e
> Gitweb:     http://git.kernel.org/tip/dc382fd5bcca7098a984705ed6ac880f539d068e
> Author:     David Rientjes <rientjes@xxxxxxxxxx>
> AuthorDate: Mon, 16 May 2011 13:54:10 -0700
> Committer:  H. Peter Anvin <hpa@xxxxxxxxxxxxxxx>
> CommitDate: Mon, 16 May 2011 14:03:28 -0700
> 
> x86, mm: Allow ZONE_DMA to be configurable
> 
> ZONE_DMA is unnecessary for a large number of machines that do not
> require less than 32-bit DMA addressing, e.g. ISA legacy DMA or PCI
> cards with a restricted DMA address mask.
> 
> This patch allows users to disable ZONE_DMA for x86 if they know they
> will not be using such devices with their kernel.
> 
> This prevents the VM from unnecessarily reserving a ratio of memory
> (defaulting to 1/256th of system capacity) with lowmem_reserve_ratio
> for such allocations when it will never be used.
> 
> Signed-off-by: David Rientjes <rientjes@xxxxxxxxxx>
> Link: http://lkml.kernel.org/r/alpine.DEB.2.00.1105161353560.4353@xxxxxxxxxxxxxxxxxxxxxxxxx
> Signed-off-by: H. Peter Anvin <hpa@xxxxxxxxxxxxxxx>

This causes the ZONE_DMA menu option to appear in the toplevel menu of
the kernel configurator instead of under EXPERT, where it should belong
IMO.

> ---
>  arch/x86/Kconfig      |    9 ++++++++-
>  arch/x86/mm/init_32.c |    2 ++
>  arch/x86/mm/init_64.c |    2 ++
>  3 files changed, 12 insertions(+), 1 deletions(-)
> 
> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index 648fca4..0eb801a 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -112,7 +112,14 @@ config MMU
>  	def_bool y
>  
>  config ZONE_DMA
> -	def_bool y
> +	bool "DMA memory allocation support" if EXPERT
> +	default y
> +	help
> +	  DMA memory allocation support allows devices with less than 32-bit
> +	  addressing to allocate within the first 16MB of address space.
> +	  Disable if no such devices will be used.
> +
> +	  If unsure, say Y.

maybe this should go into init/Kconfig ?

Thanks.

-- 
Regards/Gruss,
    Boris.
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