linux-kernel - Re: [PATCH 20/24] iommu/dma: Refactor iommu_dma

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Date:   Wed, 22 May 2019 18:11:09 +0100
From:   Robin Murphy <robin.murphy@....com>
To:     Christoph Hellwig <hch@....de>
Cc:     Joerg Roedel <joro@...tes.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Tom Murphy <tmurphy@...sta.com>,
        iommu@...ts.linux-foundation.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 20/24] iommu/dma: Refactor iommu_dma_mmap

On 20/05/2019 08:29, Christoph Hellwig wrote:
> Inline __iommu_dma_mmap_pfn into the main function, and use the
> fact that __iommu_dma_get_pages return NULL for remapped contigous
> allocations to simplify the code flow a bit.

This would be a good point to get rid of __iommu_dma_mmap() now too.

Robin.

> Signed-off-by: Christoph Hellwig <hch@....de>
> Reviewed-by: Robin Murphy <robin.murphy@....com>
> ---
>   drivers/iommu/dma-iommu.c | 46 ++++++++++-----------------------------
>   1 file changed, 11 insertions(+), 35 deletions(-)
> 
> diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
> index fa95794868a4..84150ca7b572 100644
> --- a/drivers/iommu/dma-iommu.c
> +++ b/drivers/iommu/dma-iommu.c
> @@ -1042,31 +1042,12 @@ static void *iommu_dma_alloc(struct device *dev, size_t size,
>   	return cpu_addr;
>   }
>   
> -static int __iommu_dma_mmap_pfn(struct vm_area_struct *vma,
> -			      unsigned long pfn, size_t size)
> -{
> -	int ret = -ENXIO;
> -	unsigned long nr_vma_pages = vma_pages(vma);
> -	unsigned long nr_pages = PAGE_ALIGN(size) >> PAGE_SHIFT;
> -	unsigned long off = vma->vm_pgoff;
> -
> -	if (off < nr_pages && nr_vma_pages <= (nr_pages - off)) {
> -		ret = remap_pfn_range(vma, vma->vm_start,
> -				      pfn + off,
> -				      vma->vm_end - vma->vm_start,
> -				      vma->vm_page_prot);
> -	}
> -
> -	return ret;
> -}
> -
>   static int iommu_dma_mmap(struct device *dev, struct vm_area_struct *vma,
>   		void *cpu_addr, dma_addr_t dma_addr, size_t size,
>   		unsigned long attrs)
>   {
>   	unsigned long nr_pages = PAGE_ALIGN(size) >> PAGE_SHIFT;
> -	unsigned long off = vma->vm_pgoff;
> -	struct page **pages;
> +	unsigned long pfn, off = vma->vm_pgoff;
>   	int ret;
>   
>   	vma->vm_page_prot = arch_dma_mmap_pgprot(dev, vma->vm_page_prot, attrs);
> @@ -1077,24 +1058,19 @@ static int iommu_dma_mmap(struct device *dev, struct vm_area_struct *vma,
>   	if (off >= nr_pages || vma_pages(vma) > nr_pages - off)
>   		return -ENXIO;
>   
> -	if (!is_vmalloc_addr(cpu_addr)) {
> -		unsigned long pfn = page_to_pfn(virt_to_page(cpu_addr));
> -		return __iommu_dma_mmap_pfn(vma, pfn, size);
> -	}
> +	if (is_vmalloc_addr(cpu_addr)) {
> +		struct page **pages = __iommu_dma_get_pages(cpu_addr);
>   
> -	if (attrs & DMA_ATTR_FORCE_CONTIGUOUS) {
> -		/*
> -		 * DMA_ATTR_FORCE_CONTIGUOUS allocations are always remapped,
> -		 * hence in the vmalloc space.
> -		 */
> -		unsigned long pfn = vmalloc_to_pfn(cpu_addr);
> -		return __iommu_dma_mmap_pfn(vma, pfn, size);
> +		if (pages)
> +			return __iommu_dma_mmap(pages, size, vma);
> +		pfn = vmalloc_to_pfn(cpu_addr);
> +	} else {
> +		pfn = page_to_pfn(virt_to_page(cpu_addr));
>   	}
>   
> -	pages = __iommu_dma_get_pages(cpu_addr);
> -	if (!pages)
> -		return -ENXIO;
> -	return __iommu_dma_mmap(pages, size, vma);
> +	return remap_pfn_range(vma, vma->vm_start, pfn + off,
> +			       vma->vm_end - vma->vm_start,
> +			       vma->vm_page_prot);
>   }
>   
>   static int iommu_dma_get_sgtable(struct device *dev, struct sg_table *sgt,
>