This adds support for the DMA Contiguous Memory Allocator for intel-iommu.
This change enables dma_alloc_coherent() to allocate big contiguous
memory.

It is achieved in the same way as nommu_dma_ops currently does, i.e.
trying to allocate memory by dma_alloc_from_contiguous() and alloc_pages()
is used as a fallback.

Cc: Marek Szyprowski <m.szyprow...@samsung.com>
Cc: David Woodhouse <dw...@infradead.org>
Cc: io...@lists.linux-foundation.org
Cc: Thomas Gleixner <t...@linutronix.de>
Cc: Ingo Molnar <mi...@redhat.com>
Cc: "H. Peter Anvin" <h...@zytor.com>
Cc: x...@kernel.org
Signed-off-by: Akinobu Mita <akinobu.m...@gmail.com>
---
 drivers/iommu/intel-iommu.c | 32 ++++++++++++++++++++++++--------
 1 file changed, 24 insertions(+), 8 deletions(-)

diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
index fd426ca..172c2b0 100644
--- a/drivers/iommu/intel-iommu.c
+++ b/drivers/iommu/intel-iommu.c
@@ -3004,7 +3004,7 @@ static void *intel_alloc_coherent(struct device *hwdev, 
size_t size,
                                  dma_addr_t *dma_handle, gfp_t flags,
                                  struct dma_attrs *attrs)
 {
-       void *vaddr;
+       struct page *page = NULL;
        int order;
 
        size = PAGE_ALIGN(size);
@@ -3019,17 +3019,31 @@ static void *intel_alloc_coherent(struct device *hwdev, 
size_t size,
                        flags |= GFP_DMA32;
        }
 
-       vaddr = (void *)__get_free_pages(flags, order);
-       if (!vaddr)
+       if (!(flags & GFP_ATOMIC)) {
+               unsigned int count = size >> PAGE_SHIFT;
+
+               page = dma_alloc_from_contiguous(hwdev, count, order);
+               if (page && iommu_no_mapping(hwdev) &&
+                   page_to_phys(page) + size > hwdev->coherent_dma_mask) {
+                       dma_release_from_contiguous(hwdev, page, count);
+                       page = NULL;
+               }
+       }
+
+       if (!page)
+               page = alloc_pages(flags, order);
+       if (!page)
                return NULL;
-       memset(vaddr, 0, size);
+       memset(page_address(page), 0, size);
 
-       *dma_handle = __intel_map_single(hwdev, virt_to_bus(vaddr), size,
+       *dma_handle = __intel_map_single(hwdev, page_to_phys(page), size,
                                         DMA_BIDIRECTIONAL,
                                         hwdev->coherent_dma_mask);
        if (*dma_handle)
-               return vaddr;
-       free_pages((unsigned long)vaddr, order);
+               return page_address(page);
+       if (!dma_release_from_contiguous(hwdev, page, size >> PAGE_SHIFT))
+               __free_pages(page, order);
+
        return NULL;
 }
 
@@ -3037,12 +3051,14 @@ static void intel_free_coherent(struct device *hwdev, 
size_t size, void *vaddr,
                                dma_addr_t dma_handle, struct dma_attrs *attrs)
 {
        int order;
+       struct page *page = virt_to_page(vaddr);
 
        size = PAGE_ALIGN(size);
        order = get_order(size);
 
        intel_unmap_page(hwdev, dma_handle, size, DMA_BIDIRECTIONAL, NULL);
-       free_pages((unsigned long)vaddr, order);
+       if (!dma_release_from_contiguous(hwdev, page, size >> PAGE_SHIFT))
+               __free_pages(page, order);
 }
 
 static void intel_unmap_sg(struct device *hwdev, struct scatterlist *sglist,
-- 
1.8.3.2

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