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Subject[PATCH 06/19] dma-iommu: fix and refactor iommu_dma_mmap
Date
The current iommu_dma_mmap code does not properly handle memory from the
page allocator that hasn't been remapped, which can happen in the rare
case of allocations for a coherent device that aren't allowed to block.

Fix this by replacing iommu_dma_mmap with a slightly tweaked copy of
dma_common_mmap with special handling for the remapped array of
pages allocated from __iommu_dma_alloc.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
drivers/iommu/dma-iommu.c | 59 +++++++++++++++------------------------
1 file changed, 23 insertions(+), 36 deletions(-)

diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
index e0ffe22775ac..26f479d49103 100644
--- a/drivers/iommu/dma-iommu.c
+++ b/drivers/iommu/dma-iommu.c
@@ -592,23 +592,27 @@ 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;
@@ -1047,29 +1051,14 @@ 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)
-{
- 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)
{
- struct vm_struct *area;
+ unsigned long user_count = vma_pages(vma);
+ unsigned long count = PAGE_ALIGN(size) >> PAGE_SHIFT;
+ unsigned long off = vma->vm_pgoff;
+ unsigned long pfn;
int ret;

vma->vm_page_prot = arch_dma_mmap_pgprot(dev, vma->vm_page_prot, attrs);
@@ -1077,20 +1066,18 @@ static int iommu_dma_mmap(struct device *dev, struct vm_area_struct *vma,
if (dma_mmap_from_dev_coherent(dev, vma, cpu_addr, size, &ret))
return ret;

- 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))
+ if (off >= count || user_count > count - off)
return -ENXIO;

- return __iommu_dma_mmap(area->pages, size, vma);
+ 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));
+
+ return remap_pfn_range(vma, vma->vm_start, pfn + vma->vm_pgoff,
+ user_count << PAGE_SHIFT, vma->vm_page_prot);
}

static int __iommu_dma_get_sgtable_page(struct sg_table *sgt, struct page *page,
--
2.20.1
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