Re: [PATCH 12/26] iommu/dma: Refactor the page array remapping allocator

[Robin Murphy <robin.murphy@arm.com>]

On 22/04/2019 18:59, Christoph Hellwig wrote:
> Move the call to dma_common_pages_remap into __iommu_dma_alloc and
> rename it to iommu_dma_alloc_remap.  This creates a self-contained
> helper for remapped pages allocation and mapping.

Reviewed-by: Robin Murphy <robin.murphy@arm.com>

> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
>   drivers/iommu/dma-iommu.c | 54 +++++++++++++++++++--------------------
>   1 file changed, 26 insertions(+), 28 deletions(-)
> 
> diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
> index 8e2d9733113e..b8e46e89a60a 100644
> --- a/drivers/iommu/dma-iommu.c
> +++ b/drivers/iommu/dma-iommu.c
> @@ -535,9 +535,9 @@ static struct page **__iommu_dma_get_pages(void *cpu_addr)
>   }
>   
>   /**
> - * iommu_dma_free - Free a buffer allocated by __iommu_dma_alloc()
> + * iommu_dma_free - Free a buffer allocated by iommu_dma_alloc_remap()
>    * @dev: Device which owns this buffer
> - * @pages: Array of buffer pages as returned by __iommu_dma_alloc()
> + * @pages: Array of buffer pages as returned by __iommu_dma_alloc_remap()
>    * @size: Size of buffer in bytes
>    * @handle: DMA address of buffer
>    *
> @@ -553,33 +553,35 @@ static void __iommu_dma_free(struct device *dev, struct page **pages,
>   }
>   
>   /**
> - * __iommu_dma_alloc - Allocate and map a buffer contiguous in IOVA space
> + * iommu_dma_alloc_remap - Allocate and map a buffer contiguous in IOVA space
>    * @dev: Device to allocate memory for. Must be a real device
>    *	 attached to an iommu_dma_domain
>    * @size: Size of buffer in bytes
> + * @dma_handle: Out argument for allocated DMA handle
>    * @gfp: Allocation flags
>    * @attrs: DMA attributes for this allocation
> - * @prot: IOMMU mapping flags
> - * @handle: Out argument for allocated DMA handle
>    *
>    * If @size is less than PAGE_SIZE, then a full CPU page will be allocated,
>    * but an IOMMU which supports smaller pages might not map the whole thing.
>    *
> - * Return: Array of struct page pointers describing the buffer,
> - *	   or NULL on failure.
> + * Return: Mapped virtual address, or NULL on failure.
>    */
> -static struct page **__iommu_dma_alloc(struct device *dev, size_t size,
> -		gfp_t gfp, unsigned long attrs, int prot, dma_addr_t *handle)
> +static void *iommu_dma_alloc_remap(struct device *dev, size_t size,
> +		dma_addr_t *dma_handle, gfp_t gfp, unsigned long attrs)
>   {
>   	struct iommu_domain *domain = iommu_get_dma_domain(dev);
>   	struct iommu_dma_cookie *cookie = domain->iova_cookie;
>   	struct iova_domain *iovad = &cookie->iovad;
> +	bool coherent = dev_is_dma_coherent(dev);
> +	int ioprot = dma_info_to_prot(DMA_BIDIRECTIONAL, coherent, attrs);
> +	pgprot_t prot = arch_dma_mmap_pgprot(dev, PAGE_KERNEL, attrs);
> +	unsigned int count, min_size, alloc_sizes = domain->pgsize_bitmap;
>   	struct page **pages;
>   	struct sg_table sgt;
>   	dma_addr_t iova;
> -	unsigned int count, min_size, alloc_sizes = domain->pgsize_bitmap;
> +	void *vaddr;
>   
> -	*handle = DMA_MAPPING_ERROR;
> +	*dma_handle = DMA_MAPPING_ERROR;
>   
>   	min_size = alloc_sizes & -alloc_sizes;
>   	if (min_size < PAGE_SIZE) {
> @@ -605,7 +607,7 @@ static struct page **__iommu_dma_alloc(struct device *dev, size_t size,
>   	if (sg_alloc_table_from_pages(&sgt, pages, count, 0, size, GFP_KERNEL))
>   		goto out_free_iova;
>   
> -	if (!(prot & IOMMU_CACHE)) {
> +	if (!(ioprot & IOMMU_CACHE)) {
>   		struct scatterlist *sg;
>   		int i;
>   
> @@ -613,14 +615,21 @@ static struct page **__iommu_dma_alloc(struct device *dev, size_t size,
>   			arch_dma_prep_coherent(sg_page(sg), sg->length);
>   	}
>   
> -	if (iommu_map_sg(domain, iova, sgt.sgl, sgt.orig_nents, prot)
> +	if (iommu_map_sg(domain, iova, sgt.sgl, sgt.orig_nents, ioprot)
>   			< size)
>   		goto out_free_sg;
>   
> -	*handle = iova;
> +	vaddr = dma_common_pages_remap(pages, size, VM_USERMAP, prot,
> +			__builtin_return_address(0));
> +	if (!vaddr)
> +		goto out_unmap;
> +
> +	*dma_handle = iova;
>   	sg_free_table(&sgt);
> -	return pages;
> +	return vaddr;
>   
> +out_unmap:
> +	__iommu_dma_unmap(dev, iova, size);
>   out_free_sg:
>   	sg_free_table(&sgt);
>   out_free_iova:
> @@ -989,18 +998,7 @@ static void *iommu_dma_alloc(struct device *dev, size_t size,
>   						    size >> PAGE_SHIFT);
>   		}
>   	} else {
> -		pgprot_t prot = arch_dma_mmap_pgprot(dev, PAGE_KERNEL, attrs);
> -		struct page **pages;
> -
> -		pages = __iommu_dma_alloc(dev, iosize, gfp, attrs, ioprot,
> -					handle);
> -		if (!pages)
> -			return NULL;
> -
> -		addr = dma_common_pages_remap(pages, size, VM_USERMAP, prot,
> -					      __builtin_return_address(0));
> -		if (!addr)
> -			__iommu_dma_free(dev, pages, iosize, handle);
> +		addr = iommu_dma_alloc_remap(dev, iosize, handle, gfp, attrs);
>   	}
>   	return addr;
>   }
> @@ -1014,7 +1012,7 @@ static void iommu_dma_free(struct device *dev, size_t size, void *cpu_addr,
>   	/*
>   	 * @cpu_addr will be one of 4 things depending on how it was allocated:
>   	 * - A remapped array of pages for contiguous allocations.
> -	 * - A remapped array of pages from __iommu_dma_alloc(), for all
> +	 * - A remapped array of pages from iommu_dma_alloc_remap(), for all
>   	 *   non-atomic allocations.
>   	 * - A non-cacheable alias from the atomic pool, for atomic
>   	 *   allocations by non-coherent devices.
>