Re: [PATCH 1/2] x86 swiotlb: Verify we can perform the remapping requested.

[Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>]

On Mon, Oct 17, 2011 at 02:19:18PM -0700, Eric W. Biederman wrote:
> 
> Recently I had a driver try with a peculiar 2G dma memory limit.
> It failed in weird and strange ways because my bounce buffers were
> being allocated above 2G where the driver could not reach, and
> no error was reported when the mappings were setup.

OK, so the overflow buffer was used instead.. which presumarily
also was allocated above the 2G? That seems to point that
alloc_bootmem_low_pages is not doing its job?

> 
> Use the swiotlb_dma_supported to avoid silent problems like this
> in the future.

Which driver was it that had this limit?

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

I also CC-ed Fujita on this as he is the swiotlb maintainer.

> ---
>  arch/x86/kernel/pci-swiotlb.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/arch/x86/kernel/pci-swiotlb.c b/arch/x86/kernel/pci-swiotlb.c
> index 8f972cb..6a802fa 100644
> --- a/arch/x86/kernel/pci-swiotlb.c
> +++ b/arch/x86/kernel/pci-swiotlb.c
> @@ -38,7 +38,7 @@ static struct dma_map_ops swiotlb_dma_ops = {
>  	.unmap_sg = swiotlb_unmap_sg_attrs,
>  	.map_page = swiotlb_map_page,
>  	.unmap_page = swiotlb_unmap_page,
> -	.dma_supported = NULL,
> +	.dma_supported = swiotlb_dma_supported,
>  };
>  
>  /*
> -- 
> 1.7.2.5
> 
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