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Subject[PATCH 07/19] dma-iommu: fix and refactor iommu_dma_get_sgtable
Date
The current iommu_dma_get_sgtable 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_get_sgtable with a slightly tweaked copy
of dma_common_get_sgtable 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 | 49 +++++++++++++++++++--------------------
1 file changed, 24 insertions(+), 25 deletions(-)

diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
index 26f479d49103..8f3dc6ab3da1 100644
--- a/drivers/iommu/dma-iommu.c
+++ b/drivers/iommu/dma-iommu.c
@@ -620,6 +620,18 @@ static int iommu_dma_mmap_remap(void *cpu_addr, size_t size,
return ret;
}

+static int iommu_dma_get_sgtable_remap(struct sg_table *sgt, void *cpu_addr,
+ size_t size)
+{
+ unsigned int count = PAGE_ALIGN(size) >> PAGE_SHIFT;
+ struct vm_struct *area = find_vm_area(cpu_addr);
+
+ if (WARN_ON(!area || !area->pages))
+ return -ENXIO;
+ return sg_alloc_table_from_pages(sgt, area->pages, count, 0, size,
+ GFP_KERNEL);
+}
+
static void iommu_dma_sync_single_for_cpu(struct device *dev,
dma_addr_t dma_handle, size_t size, enum dma_data_direction dir)
{
@@ -1080,37 +1092,24 @@ static int iommu_dma_mmap(struct device *dev, struct vm_area_struct *vma,
user_count << PAGE_SHIFT, vma->vm_page_prot);
}

-static int __iommu_dma_get_sgtable_page(struct sg_table *sgt, struct page *page,
- size_t size)
-{
- int ret = sg_alloc_table(sgt, 1, GFP_KERNEL);
-
- if (!ret)
- sg_set_page(sgt->sgl, page, PAGE_ALIGN(size), 0);
- return ret;
-}
-
static int iommu_dma_get_sgtable(struct device *dev, struct sg_table *sgt,
void *cpu_addr, dma_addr_t dma_addr, size_t size,
unsigned long attrs)
{
- unsigned int count = PAGE_ALIGN(size) >> PAGE_SHIFT;
- struct vm_struct *area = find_vm_area(cpu_addr);
-
- if (attrs & DMA_ATTR_FORCE_CONTIGUOUS) {
- /*
- * DMA_ATTR_FORCE_CONTIGUOUS allocations are always remapped,
- * hence in the vmalloc space.
- */
- struct page *page = vmalloc_to_page(cpu_addr);
- return __iommu_dma_get_sgtable_page(sgt, page, size);
- }
+ struct page *page;
+ int ret;

- if (WARN_ON(!area || !area->pages))
- return -ENXIO;
+ if (is_vmalloc_addr(cpu_addr)) {
+ if (!(attrs & DMA_ATTR_FORCE_CONTIGUOUS))
+ return iommu_dma_get_sgtable_remap(sgt, cpu_addr, size);
+ page = vmalloc_to_page(cpu_addr);
+ } else
+ page = virt_to_page(cpu_addr);

- return sg_alloc_table_from_pages(sgt, area->pages, count, 0, size,
- GFP_KERNEL);
+ ret = sg_alloc_table(sgt, 1, GFP_KERNEL);
+ if (!ret)
+ sg_set_page(sgt->sgl, page, PAGE_ALIGN(size), 0);
+ return ret;
}

static const struct dma_map_ops iommu_dma_ops = {
--
2.20.1
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