linux-kernel - Re: [PATCH 4/5] x86: dma_alloc_coherent sets gfp flags properly

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Date:	Mon, 8 Sep 2008 14:01:56 +0200
From:	Joerg Roedel <joerg.roedel@....com>
To:	FUJITA Tomonori <fujita.tomonori@....ntt.co.jp>
CC:	linux-kernel@...r.kernel.org, mingo@...hat.com,
	tony.luck@...el.com, linux-ia64@...r.kernel.org,
	iommu@...ts.linux-foundation.org
Subject: Re: [PATCH 4/5] x86: dma_alloc_coherent sets gfp flags properly

On Mon, Sep 08, 2008 at 06:10:13PM +0900, FUJITA Tomonori wrote:
> Non real IOMMU implemenations (which doesn't do virtual mappings,
> e.g. swiotlb, pci-nommu, etc) need to use proper gfp flags and
> dma_mask to allocate pages in their own dma_alloc_coherent()
> (allocated page need to be suitable for device's coherent_dma_mask).
> 
> This patch makes dma_alloc_coherent do this job so that IOMMUs don't
> need to take care of it any more.
> 
> Real IOMMU implemenataions can simply ignore the gfp flags.
> 
> Signed-off-by: FUJITA Tomonori <fujita.tomonori@....ntt.co.jp>

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

> ---
>  arch/x86/kernel/pci-nommu.c   |   19 ++-----------------
>  include/asm-x86/dma-mapping.h |   32 ++++++++++++++++++++++++++++----
>  2 files changed, 30 insertions(+), 21 deletions(-)
> 
> diff --git a/arch/x86/kernel/pci-nommu.c b/arch/x86/kernel/pci-nommu.c
> index ada1c87..8e398b5 100644
> --- a/arch/x86/kernel/pci-nommu.c
> +++ b/arch/x86/kernel/pci-nommu.c
> @@ -80,26 +80,11 @@ nommu_alloc_coherent(struct device *hwdev, size_t size,
>  	int node;
>  	struct page *page;
>  
> -	gfp |= __GFP_ZERO;
> -
> -	dma_mask = hwdev->coherent_dma_mask;
> -	if (!dma_mask)
> -		dma_mask = *(hwdev->dma_mask);
> +	dma_mask = dma_alloc_coherent_mask(hwdev, gfp);
>  
> -	if (dma_mask < DMA_24BIT_MASK)
> -		return NULL;
> +	gfp |= __GFP_ZERO;
>  
>  	node = dev_to_node(hwdev);
> -
> -#ifdef CONFIG_X86_64
> -	if (dma_mask <= DMA_32BIT_MASK && !(gfp & GFP_DMA))
> -		gfp |= GFP_DMA32;
> -#endif
> -
> -	/* No alloc-free penalty for ISA devices */
> -	if (dma_mask == DMA_24BIT_MASK)
> -		gfp |= GFP_DMA;
> -
>  again:
>  	page = alloc_pages_node(node, gfp, get_order(size));
>  	if (!page)
> diff --git a/include/asm-x86/dma-mapping.h b/include/asm-x86/dma-mapping.h
> index 9d6dcf4..a072ae6 100644
> --- a/include/asm-x86/dma-mapping.h
> +++ b/include/asm-x86/dma-mapping.h
> @@ -241,6 +241,29 @@ static inline int dma_get_cache_alignment(void)
>  	return boot_cpu_data.x86_clflush_size;
>  }
>  
> +static inline unsigned long dma_alloc_coherent_mask(struct device *dev,
> +						    gfp_t gfp)
> +{
> +	unsigned long dma_mask = 0;
> +
> +	dma_mask = dev->coherent_dma_mask;
> +	if (!dma_mask)
> +		dma_mask = (gfp & GFP_DMA) ? DMA_24BIT_MASK : DMA_32BIT_MASK;
> +
> +	return dma_mask;
> +}
> +
> +static inline gfp_t dma_alloc_coherent_gfp_flags(struct device *dev, gfp_t gfp)
> +{
> +	unsigned long dma_mask = dma_alloc_coherent_mask(dev, gfp);
> +
> +#ifdef CONFIG_X86_64
> +	if (dma_mask <= DMA_32BIT_MASK && !(gfp & GFP_DMA))
> +		gfp |= GFP_DMA32;
> +#endif
> +       return gfp;
> +}
> +
>  static inline void *
>  dma_alloc_coherent(struct device *dev, size_t size, dma_addr_t *dma_handle,
>  		gfp_t gfp)
> @@ -261,10 +284,11 @@ dma_alloc_coherent(struct device *dev, size_t size, dma_addr_t *dma_handle,
>  	if (!dev->dma_mask)
>  		return NULL;
>  
> -	if (ops->alloc_coherent)
> -		return ops->alloc_coherent(dev, size,
> -				dma_handle, gfp);
> -	return NULL;
> +	if (!ops->alloc_coherent)
> +		return NULL;
> +
> +	return ops->alloc_coherent(dev, size, dma_handle,
> +				   dma_alloc_coherent_gfp_flags(dev, gfp));
>  }
>  
>  static inline void dma_free_coherent(struct device *dev, size_t size,
> -- 
> 1.5.5.GIT
> 
> 

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