[PATCH] arm64/dma-mapping: fix DMA_ATTR_FORCE_CONTIGUOUS mmaping code

[Andrzej Hajda]

In case of DMA_ATTR_FORCE_CONTIGUOUS allocations vm_area->pages
is invalid. __iommu_mmap_attrs and __iommu_get_sgtable cannot use
it. In first case temporary pages array is passed to iommu_dma_mmap,
in 2nd case single entry sg table is created directly instead
of calling helper.

Fixes: 44176bb ("arm64: Add support for DMA_ATTR_FORCE_CONTIGUOUS to IOMMU")
Signed-off-by: Andrzej Hajda <a.hajda at samsung.com>
---
Hi,

I am not familiar with this framework so please don't be too cruel ;)
Alternative solution I see is to always create vm_area->pages,
I do not know which approach is preferred.

Regards
Andrzej
---
 arch/arm64/mm/dma-mapping.c | 40 ++++++++++++++++++++++++++++++++++++++--
 1 file changed, 38 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/mm/dma-mapping.c b/arch/arm64/mm/dma-mapping.c
index f7b5401..bba2bc8 100644
--- a/arch/arm64/mm/dma-mapping.c
+++ b/arch/arm64/mm/dma-mapping.c
@@ -704,7 +704,30 @@ static int __iommu_mmap_attrs(struct device *dev, struct vm_area_struct *vma,
 		return ret;
 
 	area = find_vm_area(cpu_addr);
-	if (WARN_ON(!area || !area->pages))
+	if (WARN_ON(!area))
+		return -ENXIO;
+
+	if (attrs & DMA_ATTR_FORCE_CONTIGUOUS) {
+		struct page *page = vmalloc_to_page(cpu_addr);
+		unsigned int count = size >> PAGE_SHIFT;
+		struct page **pages;
+		unsigned long pfn;
+		int i;
+
+		pages = kmalloc_array(count, sizeof(*pages), GFP_KERNEL);
+		if (!pages)
+			return -ENOMEM;
+
+		for (i = 0, pfn = page_to_pfn(page); i < count; i++)
+			pages[i] = pfn_to_page(pfn + i);
+
+		ret = iommu_dma_mmap(pages, size, vma);
+		kfree(pages);
+
+		return ret;
+	}
+
+	if (WARN_ON(!area->pages))
 		return -ENXIO;
 
 	return iommu_dma_mmap(area->pages, size, vma);
@@ -717,7 +740,20 @@ static int __iommu_get_sgtable(struct device *dev, struct sg_table *sgt,
 	unsigned int count = PAGE_ALIGN(size) >> PAGE_SHIFT;
 	struct vm_struct *area = find_vm_area(cpu_addr);
 
-	if (WARN_ON(!area || !area->pages))
+	if (WARN_ON(!area))
+		return -ENXIO;
+
+	if (attrs & DMA_ATTR_FORCE_CONTIGUOUS) {
+		int ret = sg_alloc_table(sgt, 1, GFP_KERNEL);
+
+		if (!ret)
+			sg_set_page(sgt->sgl, vmalloc_to_page(cpu_addr),
+				PAGE_ALIGN(size), 0);
+
+		return ret;
+	}
+
+	if (WARN_ON(!area->pages))
 		return -ENXIO;
 
 	return sg_alloc_table_from_pages(sgt, area->pages, count, 0, size,
-- 
2.7.4