linux-kernel - Re: [PATCH 2/2] x86 amd_gart_64: Verify we can perform the remapping requested

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Date:	Mon, 24 Oct 2011 12:07:36 +0200
From:	Joerg Roedel <joro@...tes.org>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] x86 amd_gart_64: Verify we can perform the
	remapping requested

On Mon, Oct 17, 2011 at 02:20:15PM -0700, Eric W. Biederman wrote:
> 
> Recently I had a driver try with a peculiar 2G dma memory limit.
> The driver failed in weird and strange ways because the GART remapping
> apperture had been allocated above 2G where the driver cound not reach,
> and no error was reported when the mappings were setup.
> 
> Implement gart_dma_supported to test for this problem case and to return
> and error if we can not support the remapping.

You do basically the same as for swiotlb, so it must be good :)

> Signed-off-by: Eric W. Biederman <ebiederm@...ssion.com>

For both patches:

Acked-by: Joerg Roedel <joerg.roedel@....com>

> ---
>  arch/x86/kernel/amd_gart_64.c |    9 +++++++++
>  1 files changed, 9 insertions(+), 0 deletions(-)
> 
> diff --git a/arch/x86/kernel/amd_gart_64.c b/arch/x86/kernel/amd_gart_64.c
> index 8a439d3..66279cb 100644
> --- a/arch/x86/kernel/amd_gart_64.c
> +++ b/arch/x86/kernel/amd_gart_64.c
> @@ -519,6 +519,14 @@ static int gart_mapping_error(struct device *dev, dma_addr_t dma_addr)
>  	return (dma_addr == bad_dma_addr);
>  }
>  
> +static int gart_dma_supported(struct device *dev, u64 mask)
> +{
> +	unsigned long iommu_max_addr = iommu_bus_base + iommu_size - 1;
> +
> +	/* Fail if the gart window is too high to fit in the devices dma mask */
> +	return iommu_max_addr <= mask;
> +}
> +
>  static int no_agp;
>  
>  static __init unsigned long check_iommu_size(unsigned long aper, u64 aper_size)
> @@ -703,6 +711,7 @@ static struct dma_map_ops gart_dma_ops = {
>  	.alloc_coherent			= gart_alloc_coherent,
>  	.free_coherent			= gart_free_coherent,
>  	.mapping_error			= gart_mapping_error,
> +	.dma_supported			= gart_dma_supported,
>  };
>  
>  static void gart_iommu_shutdown(void)
> -- 
> 1.7.2.5
> 
> --
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