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SubjectRe: [PATCH 08/21] dma-iommu: refactor iommu_dma_mmap
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On 27/03/2019 08:04, Christoph Hellwig wrote:
> Move the vm_area handling into __iommu_dma_mmap, which is renamed
> to iommu_dma_mmap_remap.
>
> Inline __iommu_dma_mmap_pfn into the main function to simplify the code
> flow a bit.
>
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
> drivers/iommu/dma-iommu.c | 50 ++++++++++++++-------------------------
> 1 file changed, 18 insertions(+), 32 deletions(-)
>
> diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
> index d14fe9f8c692..43bd3c7e0f6b 100644
> --- a/drivers/iommu/dma-iommu.c
> +++ b/drivers/iommu/dma-iommu.c
> @@ -597,23 +597,27 @@ static struct page **__iommu_dma_alloc(struct device *dev, size_t size,
> }
>
> /**
> - * __iommu_dma_mmap - Map a buffer into provided user VMA
> - * @pages: Array representing buffer from __iommu_dma_alloc()
> + * iommu_dma_mmap_remap - Map a remapped page array into provided user VMA
> + * @cpu_addr: virtual address of the memory to be remapped
> * @size: Size of buffer in bytes
> * @vma: VMA describing requested userspace mapping
> *
> - * Maps the pages of the buffer in @pages into @vma. The caller is responsible
> + * Maps the pages pointed to by @cpu_addr into @vma. The caller is responsible
> * for verifying the correct size and protection of @vma beforehand.
> */
> -static int __iommu_dma_mmap(struct page **pages, size_t size,
> +static int iommu_dma_mmap_remap(void *cpu_addr, size_t size,
> struct vm_area_struct *vma)
> {
> + struct vm_struct *area = find_vm_area(cpu_addr);
> unsigned long uaddr = vma->vm_start;
> unsigned int i, count = PAGE_ALIGN(size) >> PAGE_SHIFT;
> int ret = -ENXIO;
>
> + if (WARN_ON(!area || !area->pages))
> + return -ENXIO;
> +
> for (i = vma->vm_pgoff; i < count && uaddr < vma->vm_end; i++) {
> - ret = vm_insert_page(vma, uaddr, pages[i]);
> + ret = vm_insert_page(vma, uaddr, area->pages[i]);
> if (ret)
> break;
> uaddr += PAGE_SIZE;
> @@ -1052,21 +1056,13 @@ static void iommu_dma_free(struct device *dev, size_t size, void *cpu_addr,
> }
> }
>
> -static int __iommu_dma_mmap_pfn(struct vm_area_struct *vma,
> - unsigned long pfn, size_t size)
> -{
> - return remap_pfn_range(vma, vma->vm_start, pfn + vma->vm_pgoff,
> - vma->vm_end - vma->vm_start,
> - vma->vm_page_prot);
> -}
> -
> 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 vm_struct *area;
> + unsigned long pfn;
> int ret;
>
> vma->vm_page_prot = arch_dma_mmap_pgprot(dev, vma->vm_page_prot, attrs);
> @@ -1077,25 +1073,15 @@ 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)) {
> + if (!(attrs & DMA_ATTR_FORCE_CONTIGUOUS))
> + return iommu_dma_mmap_remap(cpu_addr, size, vma);
> + pfn = vmalloc_to_pfn(cpu_addr);
> + } else
> + pfn = page_to_pfn(virt_to_page(cpu_addr));

Nit: braces around the else clause for correct style.

Otherwise, this seems to make sense;

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

>
> - 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);
> - }
> -
> - area = find_vm_area(cpu_addr);
> - if (WARN_ON(!area || !area->pages))
> - return -ENXIO;
> -
> - return __iommu_dma_mmap(area->pages, size, vma);
> + return remap_pfn_range(vma, vma->vm_start, pfn + vma->vm_pgoff,
> + vma_pages(vma) << PAGE_SHIFT, vma->vm_page_prot);
> }
>
> static int __iommu_dma_get_sgtable_page(struct sg_table *sgt, struct page *page,
>

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