linux-kernel - Re: [PATCH v8 13/46] x86, mm: use pfn_range_is

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Date:	Wed, 28 Nov 2012 12:07:11 -0500
From:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
To:	Yinghai Lu <yinghai@...nel.org>
Cc:	Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...e.hu>,
	"H. Peter Anvin" <hpa@...or.com>, Jacob Shin <jacob.shin@....com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Stefano Stabellini <stefano.stabellini@...citrix.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v8 13/46] x86, mm: use pfn_range_is_mapped() with gart

On Fri, Nov 16, 2012 at 07:38:50PM -0800, Yinghai Lu wrote:
> We are going to map ram only, so under max_low_pfn_mapped,
> between 4g and max_pfn_mapped does not mean mapped at all.

Perhaps the re-write I mentioned in the earlier email could
help here.

> 
> Use pfn_range_is_mapped() directly.
> 
> Signed-off-by: Yinghai Lu <yinghai@...nel.org>
> ---
>  arch/x86/kernel/amd_gart_64.c |    5 ++---
>  1 files changed, 2 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/x86/kernel/amd_gart_64.c b/arch/x86/kernel/amd_gart_64.c
> index e663112..b574b29 100644
> --- a/arch/x86/kernel/amd_gart_64.c
> +++ b/arch/x86/kernel/amd_gart_64.c
> @@ -768,10 +768,9 @@ int __init gart_iommu_init(void)
>  	aper_base	= info.aper_base;
>  	end_pfn		= (aper_base>>PAGE_SHIFT) + (aper_size>>PAGE_SHIFT);
>  
> -	if (end_pfn > max_low_pfn_mapped) {
> -		start_pfn = (aper_base>>PAGE_SHIFT);
> +	start_pfn = PFN_DOWN(aper_base);
> +	if (!pfn_range_is_mapped(start_pfn, end_pfn))
>  		init_memory_mapping(start_pfn<<PAGE_SHIFT, end_pfn<<PAGE_SHIFT);
> -	}
>  
>  	pr_info("PCI-DMA: using GART IOMMU.\n");
>  	iommu_size = check_iommu_size(info.aper_base, aper_size);
> -- 
> 1.7.7
--
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