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![Alexey Kardashevskiy](/assets/img/avatar_default.png)
So far we have been using huge DMA windows to map all the RAM available. The RAM is normally mapped to the VM address space contiguously, and there is always a reasonable upper limit for possible future hot plugged RAM which makes it easy to map all RAM via IOMMU. Now there is persistent memory ("ibm,pmemory" in the FDT) which (unlike normal RAM) can map anywhere in the VM space beyond the maximum RAM size and since it can be used for DMA, it requires extending the huge window up to MAX_PHYSMEM_BITS which requires hypervisor support for: 1. huge TCE tables; 2. multilevel TCE tables; 3. huge IOMMU pages. Certain hypervisors cannot do either so the only option left is restricting the huge DMA window to include only RAM and fallback to the default DMA window for persistent memory. This defines arch_dma_map_direct/etc to allow generic DMA code perform additional checks on whether direct DMA is still possible. This checks if the system has persistent memory. If it does not, the DMA bypass mode is selected, i.e. * dev->bus_dma_limit = 0 * dev->dma_ops_bypass = true <- this avoid calling dma_ops for mapping. If there is such memory, this creates identity mapping only for RAM and sets the dev->bus_dma_limit to let the generic code decide whether to call into the direct DMA or the indirect DMA ops. This should not change the existing behaviour when no persistent memory as dev->dma_ops_bypass is expected to be set. Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru> Acked-by: Michael Ellerman <mpe@ellerman.id.au> Signed-off-by: Christoph Hellwig <hch@lst.de>
210 lines
5.7 KiB
C
210 lines
5.7 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* Copyright (C) 2006 Benjamin Herrenschmidt, IBM Corporation
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*
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* Provide default implementations of the DMA mapping callbacks for
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* busses using the iommu infrastructure
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*/
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#include <linux/dma-direct.h>
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#include <linux/pci.h>
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#include <asm/iommu.h>
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#ifdef CONFIG_ARCH_HAS_DMA_MAP_DIRECT
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#define can_map_direct(dev, addr) \
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((dev)->bus_dma_limit >= phys_to_dma((dev), (addr)))
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bool arch_dma_map_page_direct(struct device *dev, phys_addr_t addr)
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{
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if (likely(!dev->bus_dma_limit))
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return false;
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return can_map_direct(dev, addr);
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}
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#define is_direct_handle(dev, h) ((h) >= (dev)->archdata.dma_offset)
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bool arch_dma_unmap_page_direct(struct device *dev, dma_addr_t dma_handle)
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{
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if (likely(!dev->bus_dma_limit))
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return false;
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return is_direct_handle(dev, dma_handle);
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}
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bool arch_dma_map_sg_direct(struct device *dev, struct scatterlist *sg,
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int nents)
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{
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struct scatterlist *s;
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int i;
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if (likely(!dev->bus_dma_limit))
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return false;
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for_each_sg(sg, s, nents, i) {
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if (!can_map_direct(dev, sg_phys(s) + s->offset + s->length))
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return false;
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}
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return true;
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}
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bool arch_dma_unmap_sg_direct(struct device *dev, struct scatterlist *sg,
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int nents)
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{
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struct scatterlist *s;
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int i;
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if (likely(!dev->bus_dma_limit))
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return false;
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for_each_sg(sg, s, nents, i) {
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if (!is_direct_handle(dev, s->dma_address + s->length))
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return false;
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}
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return true;
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}
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#endif /* CONFIG_ARCH_HAS_DMA_MAP_DIRECT */
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/*
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* Generic iommu implementation
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*/
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/* Allocates a contiguous real buffer and creates mappings over it.
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* Returns the virtual address of the buffer and sets dma_handle
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* to the dma address (mapping) of the first page.
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*/
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static void *dma_iommu_alloc_coherent(struct device *dev, size_t size,
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dma_addr_t *dma_handle, gfp_t flag,
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unsigned long attrs)
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{
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return iommu_alloc_coherent(dev, get_iommu_table_base(dev), size,
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dma_handle, dev->coherent_dma_mask, flag,
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dev_to_node(dev));
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}
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static void dma_iommu_free_coherent(struct device *dev, size_t size,
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void *vaddr, dma_addr_t dma_handle,
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unsigned long attrs)
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{
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iommu_free_coherent(get_iommu_table_base(dev), size, vaddr, dma_handle);
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}
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/* Creates TCEs for a user provided buffer. The user buffer must be
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* contiguous real kernel storage (not vmalloc). The address passed here
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* comprises a page address and offset into that page. The dma_addr_t
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* returned will point to the same byte within the page as was passed in.
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*/
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static dma_addr_t dma_iommu_map_page(struct device *dev, struct page *page,
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unsigned long offset, size_t size,
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enum dma_data_direction direction,
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unsigned long attrs)
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{
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return iommu_map_page(dev, get_iommu_table_base(dev), page, offset,
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size, dma_get_mask(dev), direction, attrs);
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}
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static void dma_iommu_unmap_page(struct device *dev, dma_addr_t dma_handle,
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size_t size, enum dma_data_direction direction,
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unsigned long attrs)
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{
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iommu_unmap_page(get_iommu_table_base(dev), dma_handle, size, direction,
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attrs);
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}
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static int dma_iommu_map_sg(struct device *dev, struct scatterlist *sglist,
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int nelems, enum dma_data_direction direction,
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unsigned long attrs)
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{
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return ppc_iommu_map_sg(dev, get_iommu_table_base(dev), sglist, nelems,
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dma_get_mask(dev), direction, attrs);
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}
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static void dma_iommu_unmap_sg(struct device *dev, struct scatterlist *sglist,
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int nelems, enum dma_data_direction direction,
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unsigned long attrs)
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{
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ppc_iommu_unmap_sg(get_iommu_table_base(dev), sglist, nelems,
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direction, attrs);
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}
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static bool dma_iommu_bypass_supported(struct device *dev, u64 mask)
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{
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struct pci_dev *pdev = to_pci_dev(dev);
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struct pci_controller *phb = pci_bus_to_host(pdev->bus);
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if (iommu_fixed_is_weak || !phb->controller_ops.iommu_bypass_supported)
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return false;
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return phb->controller_ops.iommu_bypass_supported(pdev, mask);
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}
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/* We support DMA to/from any memory page via the iommu */
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int dma_iommu_dma_supported(struct device *dev, u64 mask)
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{
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struct iommu_table *tbl = get_iommu_table_base(dev);
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if (dev_is_pci(dev) && dma_iommu_bypass_supported(dev, mask)) {
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/*
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* dma_iommu_bypass_supported() sets dma_max when there is
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* 1:1 mapping but it is somehow limited.
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* ibm,pmemory is one example.
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*/
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dev->dma_ops_bypass = dev->bus_dma_limit == 0;
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if (!dev->dma_ops_bypass)
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dev_warn(dev,
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"iommu: 64-bit OK but direct DMA is limited by %llx\n",
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dev->bus_dma_limit);
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else
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dev_dbg(dev, "iommu: 64-bit OK, using fixed ops\n");
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return 1;
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}
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if (!tbl) {
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dev_err(dev, "Warning: IOMMU dma not supported: mask 0x%08llx, table unavailable\n", mask);
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return 0;
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}
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if (tbl->it_offset > (mask >> tbl->it_page_shift)) {
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dev_info(dev, "Warning: IOMMU offset too big for device mask\n");
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dev_info(dev, "mask: 0x%08llx, table offset: 0x%08lx\n",
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mask, tbl->it_offset << tbl->it_page_shift);
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return 0;
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}
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dev_dbg(dev, "iommu: not 64-bit, using default ops\n");
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dev->dma_ops_bypass = false;
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return 1;
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}
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u64 dma_iommu_get_required_mask(struct device *dev)
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{
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struct iommu_table *tbl = get_iommu_table_base(dev);
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u64 mask;
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if (!tbl)
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return 0;
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mask = 1ULL << (fls_long(tbl->it_offset + tbl->it_size) +
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tbl->it_page_shift - 1);
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mask += mask - 1;
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return mask;
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}
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const struct dma_map_ops dma_iommu_ops = {
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.alloc = dma_iommu_alloc_coherent,
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.free = dma_iommu_free_coherent,
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.map_sg = dma_iommu_map_sg,
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.unmap_sg = dma_iommu_unmap_sg,
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.dma_supported = dma_iommu_dma_supported,
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.map_page = dma_iommu_map_page,
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.unmap_page = dma_iommu_unmap_page,
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.get_required_mask = dma_iommu_get_required_mask,
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.mmap = dma_common_mmap,
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.get_sgtable = dma_common_get_sgtable,
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.alloc_pages = dma_common_alloc_pages,
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.free_pages = dma_common_free_pages,
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};
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