[PATCH v2] 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 should not
use it and take advantage of contiguous nature of the allocation.

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

In this version of the patch I have replaced temporal pages and
iommu_dma_mmap with remap_pfn_range or rather its simplified version
vm_iomap_memory.
Unfortunately I have not find nice helper for sgtable creation, so I
left sg allocation inside _iommu_mmap_attrs.

As the fixing of DMA_ATTR_FORCE_CONTIGUOUS related crashes has higher
priority I have focused only on it in this patch.

Regards
Andrzej
---
 arch/arm64/mm/dma-mapping.c | 17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/mm/dma-mapping.c b/arch/arm64/mm/dma-mapping.c
index f7b5401..41c7c36 100644
--- a/arch/arm64/mm/dma-mapping.c
+++ b/arch/arm64/mm/dma-mapping.c
@@ -703,6 +703,10 @@ static int __iommu_mmap_attrs(struct device *dev, struct vm_area_struct *vma,
 	if (dma_mmap_from_coherent(dev, vma, cpu_addr, size, &ret))
 		return ret;
 
+	if (attrs & DMA_ATTR_FORCE_CONTIGUOUS)
+		return vm_iomap_memory(vma,
+				page_to_phys(vmalloc_to_page(cpu_addr)), size);
+
 	area = find_vm_area(cpu_addr);
 	if (WARN_ON(!area || !area->pages))
 		return -ENXIO;
@@ -715,8 +719,19 @@ static int __iommu_get_sgtable(struct device *dev, struct sg_table *sgt,
 			       size_t size, unsigned long attrs)
 {
 	unsigned int count = PAGE_ALIGN(size) >> PAGE_SHIFT;
-	struct vm_struct *area = find_vm_area(cpu_addr);
+	struct vm_struct *area;
+
+	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;
+	}
+
+	area = find_vm_area(cpu_addr);
 	if (WARN_ON(!area || !area->pages))
 		return -ENXIO;
 
-- 
2.7.4