drivers/xen/swiotlb-xen.c - third_party/kernel - Git at Google

 // SPDX-License-Identifier: GPL-2.0-only
 /*
  *  Copyright 2010
  *  by Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
  *
  * This code provides a IOMMU for Xen PV guests with PCI passthrough.
  *
  * PV guests under Xen are running in an non-contiguous memory architecture.
  *
  * When PCI pass-through is utilized, this necessitates an IOMMU for
  * translating bus (DMA) to virtual and vice-versa and also providing a
  * mechanism to have contiguous pages for device drivers operations (say DMA
  * operations).
  *
  * Specifically, under Xen the Linux idea of pages is an illusion. It
  * assumes that pages start at zero and go up to the available memory. To
  * help with that, the Linux Xen MMU provides a lookup mechanism to
  * translate the page frame numbers (PFN) to machine frame numbers (MFN)
  * and vice-versa. The MFN are the "real" frame numbers. Furthermore
  * memory is not contiguous. Xen hypervisor stitches memory for guests
  * from different pools, which means there is no guarantee that PFN==MFN
  * and PFN+1==MFN+1. Lastly with Xen 4.0, pages (in debug mode) are
  * allocated in descending order (high to low), meaning the guest might
  * never get any MFN's under the 4GB mark.
  */

 #define pr_fmt(fmt) "xen:" KBUILD_MODNAME ": " fmt

 #include <linux/memblock.h>
 #include <linux/dma-direct.h>
 #include <linux/dma-map-ops.h>
 #include <linux/export.h>
 #include <xen/swiotlb-xen.h>
 #include <xen/page.h>
 #include <xen/xen-ops.h>
 #include <xen/hvc-console.h>

 #include <asm/dma-mapping.h>
 #include <asm/xen/page-coherent.h>

 #include <trace/events/swiotlb.h>
 #define MAX_DMA_BITS 32

 /*
  * Quick lookup value of the bus address of the IOTLB.
  */

 static inline phys_addr_t xen_phys_to_bus(struct device *dev, phys_addr_t paddr)
 {
 	unsigned long bfn = pfn_to_bfn(XEN_PFN_DOWN(paddr));
 	phys_addr_t baddr = (phys_addr_t)bfn << XEN_PAGE_SHIFT;

 	baddr |= paddr & ~XEN_PAGE_MASK;
 	return baddr;
 }

 static inline dma_addr_t xen_phys_to_dma(struct device *dev, phys_addr_t paddr)
 {
 	return phys_to_dma(dev, xen_phys_to_bus(dev, paddr));
 }

 static inline phys_addr_t xen_bus_to_phys(struct device *dev,
 					  phys_addr_t baddr)
 {
 	unsigned long xen_pfn = bfn_to_pfn(XEN_PFN_DOWN(baddr));
 	phys_addr_t paddr = (xen_pfn << XEN_PAGE_SHIFT) |
 			    (baddr & ~XEN_PAGE_MASK);

 	return paddr;
 }

 static inline phys_addr_t xen_dma_to_phys(struct device *dev,
 					  dma_addr_t dma_addr)
 {
 	return xen_bus_to_phys(dev, dma_to_phys(dev, dma_addr));
 }

 static inline int range_straddles_page_boundary(phys_addr_t p, size_t size)
 {
 	unsigned long next_bfn, xen_pfn = XEN_PFN_DOWN(p);
 	unsigned int i, nr_pages = XEN_PFN_UP(xen_offset_in_page(p) + size);

 	next_bfn = pfn_to_bfn(xen_pfn);

 	for (i = 1; i < nr_pages; i++)
 		if (pfn_to_bfn(++xen_pfn) != ++next_bfn)
 			return 1;

 	return 0;
 }

 static int is_xen_swiotlb_buffer(struct device *dev, dma_addr_t dma_addr)
 {
 	unsigned long bfn = XEN_PFN_DOWN(dma_to_phys(dev, dma_addr));
 	unsigned long xen_pfn = bfn_to_local_pfn(bfn);
 	phys_addr_t paddr = (phys_addr_t)xen_pfn << XEN_PAGE_SHIFT;

 	/* If the address is outside our domain, it CAN
 	 * have the same virtual address as another address
 	 * in our domain. Therefore _only_ check address within our domain.
 	 */
 	if (pfn_valid(PFN_DOWN(paddr)))
 		return is_swiotlb_buffer(dev, paddr);
 	return 0;
 }

 static int xen_swiotlb_fixup(void *buf, unsigned long nslabs)
 {
 	int rc;
 	unsigned int order = get_order(IO_TLB_SEGSIZE << IO_TLB_SHIFT);
 	unsigned int i, dma_bits = order + PAGE_SHIFT;
 	dma_addr_t dma_handle;
 	phys_addr_t p = virt_to_phys(buf);

 	BUILD_BUG_ON(IO_TLB_SEGSIZE & (IO_TLB_SEGSIZE - 1));
 	BUG_ON(nslabs % IO_TLB_SEGSIZE);

 	i = 0;
 	do {
 		do {
 			rc = xen_create_contiguous_region(
 				p + (i << IO_TLB_SHIFT), order,
 				dma_bits, &dma_handle);
 		} while (rc && dma_bits++ < MAX_DMA_BITS);
 		if (rc)
 			return rc;

 		i += IO_TLB_SEGSIZE;
 	} while (i < nslabs);
 	return 0;
 }

 enum xen_swiotlb_err {
 	XEN_SWIOTLB_UNKNOWN = 0,
 	XEN_SWIOTLB_ENOMEM,
 	XEN_SWIOTLB_EFIXUP
 };

 static const char *xen_swiotlb_error(enum xen_swiotlb_err err)
 {
 	switch (err) {
 	case XEN_SWIOTLB_ENOMEM:
 		return "Cannot allocate Xen-SWIOTLB buffer\n";
 	case XEN_SWIOTLB_EFIXUP:
 		return "Failed to get contiguous memory for DMA from Xen!\n"\
 		    "You either: don't have the permissions, do not have"\
 		    " enough free memory under 4GB, or the hypervisor memory"\
 		    " is too fragmented!";
 	default:
 		break;
 	}
 	return "";
 }

 int xen_swiotlb_init(void)
 {
 	enum xen_swiotlb_err m_ret = XEN_SWIOTLB_UNKNOWN;
 	unsigned long bytes = swiotlb_size_or_default();
 	unsigned long nslabs = bytes >> IO_TLB_SHIFT;
 	unsigned int order, repeat = 3;
 	int rc = -ENOMEM;
 	char *start;

 	if (io_tlb_default_mem.nslabs) {
 		pr_warn("swiotlb buffer already initialized\n");
 		return -EEXIST;
 	}

 retry:
 	m_ret = XEN_SWIOTLB_ENOMEM;
 	order = get_order(bytes);

 	/*
 	 * Get IO TLB memory from any location.
 	 */
 #define SLABS_PER_PAGE (1 << (PAGE_SHIFT - IO_TLB_SHIFT))
 #define IO_TLB_MIN_SLABS ((1<<20) >> IO_TLB_SHIFT)
 	while ((SLABS_PER_PAGE << order) > IO_TLB_MIN_SLABS) {
 		start = (void *)xen_get_swiotlb_free_pages(order);
 		if (start)
 			break;
 		order--;
 	}
 	if (!start)
 		goto exit;
 	if (order != get_order(bytes)) {
 		pr_warn("Warning: only able to allocate %ld MB for software IO TLB\n",
 			(PAGE_SIZE << order) >> 20);
 		nslabs = SLABS_PER_PAGE << order;
 		bytes = nslabs << IO_TLB_SHIFT;
 	}

 	/*
 	 * And replace that memory with pages under 4GB.
 	 */
 	rc = xen_swiotlb_fixup(start, nslabs);
 	if (rc) {
 		free_pages((unsigned long)start, order);
 		m_ret = XEN_SWIOTLB_EFIXUP;
 		goto error;
 	}
 	rc = swiotlb_late_init_with_tbl(start, nslabs);
 	if (rc)
 		return rc;
 	swiotlb_set_max_segment(PAGE_SIZE);
 	return 0;
 error:
 	if (nslabs > 1024 && repeat--) {
 		/* Min is 2MB */
 		nslabs = max(1024UL, ALIGN(nslabs >> 1, IO_TLB_SEGSIZE));
 		bytes = nslabs << IO_TLB_SHIFT;
 		pr_info("Lowering to %luMB\n", bytes >> 20);
 		goto retry;
 	}
 exit:
 	pr_err("%s (rc:%d)\n", xen_swiotlb_error(m_ret), rc);
 	return rc;
 }

 #ifdef CONFIG_X86
 void __init xen_swiotlb_init_early(void)
 {
 	unsigned long bytes = swiotlb_size_or_default();
 	unsigned long nslabs = bytes >> IO_TLB_SHIFT;
 	unsigned int repeat = 3;
 	char *start;
 	int rc;

 retry:
 	/*
 	 * Get IO TLB memory from any location.
 	 */
 	start = memblock_alloc(PAGE_ALIGN(bytes),
 			       IO_TLB_SEGSIZE << IO_TLB_SHIFT);
 	if (!start)
 		panic("%s: Failed to allocate %lu bytes\n",
 		      __func__, PAGE_ALIGN(bytes));

 	/*
 	 * And replace that memory with pages under 4GB.
 	 */
 	rc = xen_swiotlb_fixup(start, nslabs);
 	if (rc) {
 		memblock_free(__pa(start), PAGE_ALIGN(bytes));
 		if (nslabs > 1024 && repeat--) {
 			/* Min is 2MB */
 			nslabs = max(1024UL, ALIGN(nslabs >> 1, IO_TLB_SEGSIZE));
 			bytes = nslabs << IO_TLB_SHIFT;
 			pr_info("Lowering to %luMB\n", bytes >> 20);
 			goto retry;
 		}
 		panic("%s (rc:%d)", xen_swiotlb_error(XEN_SWIOTLB_EFIXUP), rc);
 	}

 	if (swiotlb_init_with_tbl(start, nslabs, true))
 		panic("Cannot allocate SWIOTLB buffer");
 	swiotlb_set_max_segment(PAGE_SIZE);
 }
 #endif /* CONFIG_X86 */

 static void *
 xen_swiotlb_alloc_coherent(struct device *hwdev, size_t size,
 			   dma_addr_t *dma_handle, gfp_t flags,
 			   unsigned long attrs)
 {
 	void *ret;
 	int order = get_order(size);
 	u64 dma_mask = DMA_BIT_MASK(32);
 	phys_addr_t phys;
 	dma_addr_t dev_addr;

 	/*
 	* Ignore region specifiers - the kernel's ideas of
 	* pseudo-phys memory layout has nothing to do with the
 	* machine physical layout.  We can't allocate highmem
 	* because we can't return a pointer to it.
 	*/
 	flags &= ~(__GFP_DMA | __GFP_HIGHMEM);

 	/* Convert the size to actually allocated. */
 	size = 1UL << (order + XEN_PAGE_SHIFT);

 	/* On ARM this function returns an ioremap'ped virtual address for
 	 * which virt_to_phys doesn't return the corresponding physical
 	 * address. In fact on ARM virt_to_phys only works for kernel direct
 	 * mapped RAM memory. Also see comment below.
 	 */
 	ret = xen_alloc_coherent_pages(hwdev, size, dma_handle, flags, attrs);

 	if (!ret)
 		return ret;

 	if (hwdev && hwdev->coherent_dma_mask)
 		dma_mask = hwdev->coherent_dma_mask;

 	/* At this point dma_handle is the dma address, next we are
 	 * going to set it to the machine address.
 	 * Do not use virt_to_phys(ret) because on ARM it doesn't correspond
 	 * to *dma_handle. */
 	phys = dma_to_phys(hwdev, *dma_handle);
 	dev_addr = xen_phys_to_dma(hwdev, phys);
 	if (((dev_addr + size - 1 <= dma_mask)) &&
 	    !range_straddles_page_boundary(phys, size))
 		*dma_handle = dev_addr;
 	else {
 		if (xen_create_contiguous_region(phys, order,
 						 fls64(dma_mask), dma_handle) != 0) {
 			xen_free_coherent_pages(hwdev, size, ret, (dma_addr_t)phys, attrs);
 			return NULL;
 		}
 		*dma_handle = phys_to_dma(hwdev, *dma_handle);
 		SetPageXenRemapped(virt_to_page(ret));
 	}
 	memset(ret, 0, size);
 	return ret;
 }

 static void
 xen_swiotlb_free_coherent(struct device *hwdev, size_t size, void *vaddr,
 			  dma_addr_t dev_addr, unsigned long attrs)
 {
 	int order = get_order(size);
 	phys_addr_t phys;
 	u64 dma_mask = DMA_BIT_MASK(32);
 	struct page *page;

 	if (hwdev && hwdev->coherent_dma_mask)
 		dma_mask = hwdev->coherent_dma_mask;

 	/* do not use virt_to_phys because on ARM it doesn't return you the
 	 * physical address */
 	phys = xen_dma_to_phys(hwdev, dev_addr);

 	/* Convert the size to actually allocated. */
 	size = 1UL << (order + XEN_PAGE_SHIFT);

 	if (is_vmalloc_addr(vaddr))
 		page = vmalloc_to_page(vaddr);
 	else
 		page = virt_to_page(vaddr);

 	if (!WARN_ON((dev_addr + size - 1 > dma_mask) ||
 		     range_straddles_page_boundary(phys, size)) &&
 	    TestClearPageXenRemapped(page))
 		xen_destroy_contiguous_region(phys, order);

 	xen_free_coherent_pages(hwdev, size, vaddr, phys_to_dma(hwdev, phys),
 				attrs);
 }

 /*
  * Map a single buffer of the indicated size for DMA in streaming mode.  The
  * physical address to use is returned.
  *
  * Once the device is given the dma address, the device owns this memory until
  * either xen_swiotlb_unmap_page or xen_swiotlb_dma_sync_single is performed.
  */
 static dma_addr_t xen_swiotlb_map_page(struct device *dev, struct page *page,
 				unsigned long offset, size_t size,
 				enum dma_data_direction dir,
 				unsigned long attrs)
 {
 	phys_addr_t map, phys = page_to_phys(page) + offset;
 	dma_addr_t dev_addr = xen_phys_to_dma(dev, phys);

 	BUG_ON(dir == DMA_NONE);
 	/*
 	 * If the address happens to be in the device's DMA window,
 	 * we can safely return the device addr and not worry about bounce
 	 * buffering it.
 	 */
 	if (dma_capable(dev, dev_addr, size, true) &&
 	    !range_straddles_page_boundary(phys, size) &&
 		!xen_arch_need_swiotlb(dev, phys, dev_addr) &&
 		!is_swiotlb_force_bounce(dev))
 		goto done;

 	/*
 	 * Oh well, have to allocate and map a bounce buffer.
 	 */
 	trace_swiotlb_bounced(dev, dev_addr, size, swiotlb_force);

 	map = swiotlb_tbl_map_single(dev, phys, size, size, 0, dir, attrs);
 	if (map == (phys_addr_t)DMA_MAPPING_ERROR)
 		return DMA_MAPPING_ERROR;

 	phys = map;
 	dev_addr = xen_phys_to_dma(dev, map);

 	/*
 	 * Ensure that the address returned is DMA'ble
 	 */
 	if (unlikely(!dma_capable(dev, dev_addr, size, true))) {
 		swiotlb_tbl_unmap_single(dev, map, size, dir,
 				attrs | DMA_ATTR_SKIP_CPU_SYNC);
 		return DMA_MAPPING_ERROR;
 	}

 done:
 	if (!dev_is_dma_coherent(dev) && !(attrs & DMA_ATTR_SKIP_CPU_SYNC)) {
 		if (pfn_valid(PFN_DOWN(dma_to_phys(dev, dev_addr))))
 			arch_sync_dma_for_device(phys, size, dir);
 		else
 			xen_dma_sync_for_device(dev, dev_addr, size, dir);
 	}
 	return dev_addr;
 }

 /*
  * Unmap a single streaming mode DMA translation.  The dma_addr and size must
  * match what was provided for in a previous xen_swiotlb_map_page call.  All
  * other usages are undefined.
  *
  * After this call, reads by the cpu to the buffer are guaranteed to see
  * whatever the device wrote there.
  */
 static void xen_swiotlb_unmap_page(struct device *hwdev, dma_addr_t dev_addr,
 		size_t size, enum dma_data_direction dir, unsigned long attrs)
 {
 	phys_addr_t paddr = xen_dma_to_phys(hwdev, dev_addr);

 	BUG_ON(dir == DMA_NONE);

 	if (!dev_is_dma_coherent(hwdev) && !(attrs & DMA_ATTR_SKIP_CPU_SYNC)) {
 		if (pfn_valid(PFN_DOWN(dma_to_phys(hwdev, dev_addr))))
 			arch_sync_dma_for_cpu(paddr, size, dir);
 		else
 			xen_dma_sync_for_cpu(hwdev, dev_addr, size, dir);
 	}

 	/* NOTE: We use dev_addr here, not paddr! */
 	if (is_xen_swiotlb_buffer(hwdev, dev_addr))
 		swiotlb_tbl_unmap_single(hwdev, paddr, size, dir, attrs);
 }

 static void
 xen_swiotlb_sync_single_for_cpu(struct device *dev, dma_addr_t dma_addr,
 		size_t size, enum dma_data_direction dir)
 {
 	phys_addr_t paddr = xen_dma_to_phys(dev, dma_addr);

 	if (!dev_is_dma_coherent(dev)) {
 		if (pfn_valid(PFN_DOWN(dma_to_phys(dev, dma_addr))))
 			arch_sync_dma_for_cpu(paddr, size, dir);
 		else
 			xen_dma_sync_for_cpu(dev, dma_addr, size, dir);
 	}

 	if (is_xen_swiotlb_buffer(dev, dma_addr))
 		swiotlb_sync_single_for_cpu(dev, paddr, size, dir);
 }

 static void
 xen_swiotlb_sync_single_for_device(struct device *dev, dma_addr_t dma_addr,
 		size_t size, enum dma_data_direction dir)
 {
 	phys_addr_t paddr = xen_dma_to_phys(dev, dma_addr);

 	if (is_xen_swiotlb_buffer(dev, dma_addr))
 		swiotlb_sync_single_for_device(dev, paddr, size, dir);

 	if (!dev_is_dma_coherent(dev)) {
 		if (pfn_valid(PFN_DOWN(dma_to_phys(dev, dma_addr))))
 			arch_sync_dma_for_device(paddr, size, dir);
 		else
 			xen_dma_sync_for_device(dev, dma_addr, size, dir);
 	}
 }

 /*
  * Unmap a set of streaming mode DMA translations.  Again, cpu read rules
  * concerning calls here are the same as for swiotlb_unmap_page() above.
  */
 static void
 xen_swiotlb_unmap_sg(struct device *hwdev, struct scatterlist *sgl, int nelems,
 		enum dma_data_direction dir, unsigned long attrs)
 {
 	struct scatterlist *sg;
 	int i;

 	BUG_ON(dir == DMA_NONE);

 	for_each_sg(sgl, sg, nelems, i)
 		xen_swiotlb_unmap_page(hwdev, sg->dma_address, sg_dma_len(sg),
 				dir, attrs);

 }

 static int
 xen_swiotlb_map_sg(struct device *dev, struct scatterlist *sgl, int nelems,
 		enum dma_data_direction dir, unsigned long attrs)
 {
 	struct scatterlist *sg;
 	int i;

 	BUG_ON(dir == DMA_NONE);

 	for_each_sg(sgl, sg, nelems, i) {
 		sg->dma_address = xen_swiotlb_map_page(dev, sg_page(sg),
 				sg->offset, sg->length, dir, attrs);
 		if (sg->dma_address == DMA_MAPPING_ERROR)
 			goto out_unmap;
 		sg_dma_len(sg) = sg->length;
 	}

 	return nelems;
 out_unmap:
 	xen_swiotlb_unmap_sg(dev, sgl, i, dir, attrs | DMA_ATTR_SKIP_CPU_SYNC);
 	sg_dma_len(sgl) = 0;
 	return -EIO;
 }

 static void
 xen_swiotlb_sync_sg_for_cpu(struct device *dev, struct scatterlist *sgl,
 			    int nelems, enum dma_data_direction dir)
 {
 	struct scatterlist *sg;
 	int i;

 	for_each_sg(sgl, sg, nelems, i) {
 		xen_swiotlb_sync_single_for_cpu(dev, sg->dma_address,
 				sg->length, dir);
 	}
 }

 static void
 xen_swiotlb_sync_sg_for_device(struct device *dev, struct scatterlist *sgl,
 			       int nelems, enum dma_data_direction dir)
 {
 	struct scatterlist *sg;
 	int i;

 	for_each_sg(sgl, sg, nelems, i) {
 		xen_swiotlb_sync_single_for_device(dev, sg->dma_address,
 				sg->length, dir);
 	}
 }

 /*
  * Return whether the given device DMA address mask can be supported
  * properly.  For example, if your device can only drive the low 24-bits
  * during bus mastering, then you would pass 0x00ffffff as the mask to
  * this function.
  */
 static int
 xen_swiotlb_dma_supported(struct device *hwdev, u64 mask)
 {
 	return xen_phys_to_dma(hwdev, io_tlb_default_mem.end - 1) <= mask;
 }

 const struct dma_map_ops xen_swiotlb_dma_ops = {
 	.alloc = xen_swiotlb_alloc_coherent,
 	.free = xen_swiotlb_free_coherent,
 	.sync_single_for_cpu = xen_swiotlb_sync_single_for_cpu,
 	.sync_single_for_device = xen_swiotlb_sync_single_for_device,
 	.sync_sg_for_cpu = xen_swiotlb_sync_sg_for_cpu,
 	.sync_sg_for_device = xen_swiotlb_sync_sg_for_device,
 	.map_sg = xen_swiotlb_map_sg,
 	.unmap_sg = xen_swiotlb_unmap_sg,
 	.map_page = xen_swiotlb_map_page,
 	.unmap_page = xen_swiotlb_unmap_page,
 	.dma_supported = xen_swiotlb_dma_supported,
 	.mmap = dma_common_mmap,
 	.get_sgtable = dma_common_get_sgtable,
 	.alloc_pages = dma_common_alloc_pages,
 	.free_pages = dma_common_free_pages,
 	.max_mapping_size = swiotlb_max_mapping_size,
 };
	// SPDX-License-Identifier: GPL-2.0-only
	/*
	* Copyright 2010
	* by Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
	*
	* This code provides a IOMMU for Xen PV guests with PCI passthrough.
	*
	* PV guests under Xen are running in an non-contiguous memory architecture.
	*
	* When PCI pass-through is utilized, this necessitates an IOMMU for
	* translating bus (DMA) to virtual and vice-versa and also providing a
	* mechanism to have contiguous pages for device drivers operations (say DMA
	* operations).
	*
	* Specifically, under Xen the Linux idea of pages is an illusion. It
	* assumes that pages start at zero and go up to the available memory. To
	* help with that, the Linux Xen MMU provides a lookup mechanism to
	* translate the page frame numbers (PFN) to machine frame numbers (MFN)
	* and vice-versa. The MFN are the "real" frame numbers. Furthermore
	* memory is not contiguous. Xen hypervisor stitches memory for guests
	* from different pools, which means there is no guarantee that PFN==MFN
	* and PFN+1==MFN+1. Lastly with Xen 4.0, pages (in debug mode) are
	* allocated in descending order (high to low), meaning the guest might
	* never get any MFN's under the 4GB mark.
	*/

	#define pr_fmt(fmt) "xen:" KBUILD_MODNAME ": " fmt

	#include <linux/memblock.h>
	#include <linux/dma-direct.h>
	#include <linux/dma-map-ops.h>
	#include <linux/export.h>
	#include <xen/swiotlb-xen.h>
	#include <xen/page.h>
	#include <xen/xen-ops.h>
	#include <xen/hvc-console.h>

	#include <asm/dma-mapping.h>
	#include <asm/xen/page-coherent.h>

	#include <trace/events/swiotlb.h>
	#define MAX_DMA_BITS 32

	/*
	* Quick lookup value of the bus address of the IOTLB.
	*/

	static inline phys_addr_t xen_phys_to_bus(struct device *dev, phys_addr_t paddr)
	{
	unsigned long bfn = pfn_to_bfn(XEN_PFN_DOWN(paddr));
	phys_addr_t baddr = (phys_addr_t)bfn << XEN_PAGE_SHIFT;

	baddr \|= paddr & ~XEN_PAGE_MASK;
	return baddr;
	}

	static inline dma_addr_t xen_phys_to_dma(struct device *dev, phys_addr_t paddr)
	{
	return phys_to_dma(dev, xen_phys_to_bus(dev, paddr));
	}

	static inline phys_addr_t xen_bus_to_phys(struct device *dev,
	phys_addr_t baddr)
	{
	unsigned long xen_pfn = bfn_to_pfn(XEN_PFN_DOWN(baddr));
	phys_addr_t paddr = (xen_pfn << XEN_PAGE_SHIFT) \|
	(baddr & ~XEN_PAGE_MASK);

	return paddr;
	}

	static inline phys_addr_t xen_dma_to_phys(struct device *dev,
	dma_addr_t dma_addr)
	{
	return xen_bus_to_phys(dev, dma_to_phys(dev, dma_addr));
	}

	static inline int range_straddles_page_boundary(phys_addr_t p, size_t size)
	{
	unsigned long next_bfn, xen_pfn = XEN_PFN_DOWN(p);
	unsigned int i, nr_pages = XEN_PFN_UP(xen_offset_in_page(p) + size);

	next_bfn = pfn_to_bfn(xen_pfn);

	for (i = 1; i < nr_pages; i++)
	if (pfn_to_bfn(++xen_pfn) != ++next_bfn)
	return 1;

	return 0;
	}

	static int is_xen_swiotlb_buffer(struct device *dev, dma_addr_t dma_addr)
	{
	unsigned long bfn = XEN_PFN_DOWN(dma_to_phys(dev, dma_addr));
	unsigned long xen_pfn = bfn_to_local_pfn(bfn);
	phys_addr_t paddr = (phys_addr_t)xen_pfn << XEN_PAGE_SHIFT;

	/* If the address is outside our domain, it CAN
	* have the same virtual address as another address
	* in our domain. Therefore _only_ check address within our domain.
	*/
	if (pfn_valid(PFN_DOWN(paddr)))
	return is_swiotlb_buffer(dev, paddr);
	return 0;
	}

	static int xen_swiotlb_fixup(void *buf, unsigned long nslabs)
	{
	int rc;
	unsigned int order = get_order(IO_TLB_SEGSIZE << IO_TLB_SHIFT);
	unsigned int i, dma_bits = order + PAGE_SHIFT;
	dma_addr_t dma_handle;
	phys_addr_t p = virt_to_phys(buf);

	BUILD_BUG_ON(IO_TLB_SEGSIZE & (IO_TLB_SEGSIZE - 1));
	BUG_ON(nslabs % IO_TLB_SEGSIZE);

	i = 0;
	do {
	do {
	rc = xen_create_contiguous_region(
	p + (i << IO_TLB_SHIFT), order,
	dma_bits, &dma_handle);
	} while (rc && dma_bits++ < MAX_DMA_BITS);
	if (rc)
	return rc;

	i += IO_TLB_SEGSIZE;
	} while (i < nslabs);
	return 0;
	}

	enum xen_swiotlb_err {
	XEN_SWIOTLB_UNKNOWN = 0,
	XEN_SWIOTLB_ENOMEM,
	XEN_SWIOTLB_EFIXUP
	};

	static const char *xen_swiotlb_error(enum xen_swiotlb_err err)
	{
	switch (err) {
	case XEN_SWIOTLB_ENOMEM:
	return "Cannot allocate Xen-SWIOTLB buffer\n";
	case XEN_SWIOTLB_EFIXUP:
	return "Failed to get contiguous memory for DMA from Xen!\n"\
	"You either: don't have the permissions, do not have"\
	" enough free memory under 4GB, or the hypervisor memory"\
	" is too fragmented!";
	default:
	break;
	}
	return "";
	}

	int xen_swiotlb_init(void)
	{
	enum xen_swiotlb_err m_ret = XEN_SWIOTLB_UNKNOWN;
	unsigned long bytes = swiotlb_size_or_default();
	unsigned long nslabs = bytes >> IO_TLB_SHIFT;
	unsigned int order, repeat = 3;
	int rc = -ENOMEM;
	char *start;

	if (io_tlb_default_mem.nslabs) {
	pr_warn("swiotlb buffer already initialized\n");
	return -EEXIST;
	}

	retry:
	m_ret = XEN_SWIOTLB_ENOMEM;
	order = get_order(bytes);

	/*
	* Get IO TLB memory from any location.
	*/
	#define SLABS_PER_PAGE (1 << (PAGE_SHIFT - IO_TLB_SHIFT))
	#define IO_TLB_MIN_SLABS ((1<<20) >> IO_TLB_SHIFT)
	while ((SLABS_PER_PAGE << order) > IO_TLB_MIN_SLABS) {
	start = (void *)xen_get_swiotlb_free_pages(order);
	if (start)
	break;
	order--;
	}
	if (!start)
	goto exit;
	if (order != get_order(bytes)) {
	pr_warn("Warning: only able to allocate %ld MB for software IO TLB\n",
	(PAGE_SIZE << order) >> 20);
	nslabs = SLABS_PER_PAGE << order;
	bytes = nslabs << IO_TLB_SHIFT;
	}

	/*
	* And replace that memory with pages under 4GB.
	*/
	rc = xen_swiotlb_fixup(start, nslabs);
	if (rc) {
	free_pages((unsigned long)start, order);
	m_ret = XEN_SWIOTLB_EFIXUP;
	goto error;
	}
	rc = swiotlb_late_init_with_tbl(start, nslabs);
	if (rc)
	return rc;
	swiotlb_set_max_segment(PAGE_SIZE);
	return 0;
	error:
	if (nslabs > 1024 && repeat--) {
	/* Min is 2MB */
	nslabs = max(1024UL, ALIGN(nslabs >> 1, IO_TLB_SEGSIZE));
	bytes = nslabs << IO_TLB_SHIFT;
	pr_info("Lowering to %luMB\n", bytes >> 20);
	goto retry;
	}
	exit:
	pr_err("%s (rc:%d)\n", xen_swiotlb_error(m_ret), rc);
	return rc;
	}

	#ifdef CONFIG_X86
	void __init xen_swiotlb_init_early(void)
	{
	unsigned long bytes = swiotlb_size_or_default();
	unsigned long nslabs = bytes >> IO_TLB_SHIFT;
	unsigned int repeat = 3;
	char *start;
	int rc;

	retry:
	/*
	* Get IO TLB memory from any location.
	*/
	start = memblock_alloc(PAGE_ALIGN(bytes),
	IO_TLB_SEGSIZE << IO_TLB_SHIFT);
	if (!start)
	panic("%s: Failed to allocate %lu bytes\n",
	__func__, PAGE_ALIGN(bytes));

	/*
	* And replace that memory with pages under 4GB.
	*/
	rc = xen_swiotlb_fixup(start, nslabs);
	if (rc) {
	memblock_free(__pa(start), PAGE_ALIGN(bytes));
	if (nslabs > 1024 && repeat--) {
	/* Min is 2MB */
	nslabs = max(1024UL, ALIGN(nslabs >> 1, IO_TLB_SEGSIZE));
	bytes = nslabs << IO_TLB_SHIFT;
	pr_info("Lowering to %luMB\n", bytes >> 20);
	goto retry;
	}
	panic("%s (rc:%d)", xen_swiotlb_error(XEN_SWIOTLB_EFIXUP), rc);
	}

	if (swiotlb_init_with_tbl(start, nslabs, true))
	panic("Cannot allocate SWIOTLB buffer");
	swiotlb_set_max_segment(PAGE_SIZE);
	}
	#endif /* CONFIG_X86 */

	static void *
	xen_swiotlb_alloc_coherent(struct device *hwdev, size_t size,
	dma_addr_t *dma_handle, gfp_t flags,
	unsigned long attrs)
	{
	void *ret;
	int order = get_order(size);
	u64 dma_mask = DMA_BIT_MASK(32);
	phys_addr_t phys;
	dma_addr_t dev_addr;

	/*
	* Ignore region specifiers - the kernel's ideas of
	* pseudo-phys memory layout has nothing to do with the
	* machine physical layout. We can't allocate highmem
	* because we can't return a pointer to it.
	*/
	flags &= ~(__GFP_DMA \| __GFP_HIGHMEM);

	/* Convert the size to actually allocated. */
	size = 1UL << (order + XEN_PAGE_SHIFT);

	/* On ARM this function returns an ioremap'ped virtual address for
	* which virt_to_phys doesn't return the corresponding physical
	* address. In fact on ARM virt_to_phys only works for kernel direct
	* mapped RAM memory. Also see comment below.
	*/
	ret = xen_alloc_coherent_pages(hwdev, size, dma_handle, flags, attrs);

	if (!ret)
	return ret;

	if (hwdev && hwdev->coherent_dma_mask)
	dma_mask = hwdev->coherent_dma_mask;

	/* At this point dma_handle is the dma address, next we are
	* going to set it to the machine address.
	* Do not use virt_to_phys(ret) because on ARM it doesn't correspond
	* to dma_handle. /
	phys = dma_to_phys(hwdev, *dma_handle);
	dev_addr = xen_phys_to_dma(hwdev, phys);
	if (((dev_addr + size - 1 <= dma_mask)) &&
	!range_straddles_page_boundary(phys, size))
	*dma_handle = dev_addr;
	else {
	if (xen_create_contiguous_region(phys, order,
	fls64(dma_mask), dma_handle) != 0) {
	xen_free_coherent_pages(hwdev, size, ret, (dma_addr_t)phys, attrs);
	return NULL;
	}
	dma_handle = phys_to_dma(hwdev, dma_handle);
	SetPageXenRemapped(virt_to_page(ret));
	}
	memset(ret, 0, size);
	return ret;
	}

	static void
	xen_swiotlb_free_coherent(struct device hwdev, size_t size, void vaddr,
	dma_addr_t dev_addr, unsigned long attrs)
	{
	int order = get_order(size);
	phys_addr_t phys;
	u64 dma_mask = DMA_BIT_MASK(32);
	struct page *page;

	if (hwdev && hwdev->coherent_dma_mask)
	dma_mask = hwdev->coherent_dma_mask;

	/* do not use virt_to_phys because on ARM it doesn't return you the
	* physical address */
	phys = xen_dma_to_phys(hwdev, dev_addr);

	/* Convert the size to actually allocated. */
	size = 1UL << (order + XEN_PAGE_SHIFT);

	if (is_vmalloc_addr(vaddr))
	page = vmalloc_to_page(vaddr);
	else
	page = virt_to_page(vaddr);

	if (!WARN_ON((dev_addr + size - 1 > dma_mask) \|\|
	range_straddles_page_boundary(phys, size)) &&
	TestClearPageXenRemapped(page))
	xen_destroy_contiguous_region(phys, order);

	xen_free_coherent_pages(hwdev, size, vaddr, phys_to_dma(hwdev, phys),
	attrs);
	}

	/*
	* Map a single buffer of the indicated size for DMA in streaming mode. The
	* physical address to use is returned.
	*
	* Once the device is given the dma address, the device owns this memory until
	* either xen_swiotlb_unmap_page or xen_swiotlb_dma_sync_single is performed.
	*/
	static dma_addr_t xen_swiotlb_map_page(struct device dev, struct page page,
	unsigned long offset, size_t size,
	enum dma_data_direction dir,
	unsigned long attrs)
	{
	phys_addr_t map, phys = page_to_phys(page) + offset;
	dma_addr_t dev_addr = xen_phys_to_dma(dev, phys);

	BUG_ON(dir == DMA_NONE);
	/*
	* If the address happens to be in the device's DMA window,
	* we can safely return the device addr and not worry about bounce
	* buffering it.
	*/
	if (dma_capable(dev, dev_addr, size, true) &&
	!range_straddles_page_boundary(phys, size) &&
	!xen_arch_need_swiotlb(dev, phys, dev_addr) &&
	!is_swiotlb_force_bounce(dev))
	goto done;

	/*
	* Oh well, have to allocate and map a bounce buffer.
	*/
	trace_swiotlb_bounced(dev, dev_addr, size, swiotlb_force);

	map = swiotlb_tbl_map_single(dev, phys, size, size, 0, dir, attrs);
	if (map == (phys_addr_t)DMA_MAPPING_ERROR)
	return DMA_MAPPING_ERROR;

	phys = map;
	dev_addr = xen_phys_to_dma(dev, map);

	/*
	* Ensure that the address returned is DMA'ble
	*/
	if (unlikely(!dma_capable(dev, dev_addr, size, true))) {
	swiotlb_tbl_unmap_single(dev, map, size, dir,
	attrs \| DMA_ATTR_SKIP_CPU_SYNC);
	return DMA_MAPPING_ERROR;
	}

	done:
	if (!dev_is_dma_coherent(dev) && !(attrs & DMA_ATTR_SKIP_CPU_SYNC)) {
	if (pfn_valid(PFN_DOWN(dma_to_phys(dev, dev_addr))))
	arch_sync_dma_for_device(phys, size, dir);
	else
	xen_dma_sync_for_device(dev, dev_addr, size, dir);
	}
	return dev_addr;
	}

	/*
	* Unmap a single streaming mode DMA translation. The dma_addr and size must
	* match what was provided for in a previous xen_swiotlb_map_page call. All
	* other usages are undefined.
	*
	* After this call, reads by the cpu to the buffer are guaranteed to see
	* whatever the device wrote there.
	*/
	static void xen_swiotlb_unmap_page(struct device *hwdev, dma_addr_t dev_addr,
	size_t size, enum dma_data_direction dir, unsigned long attrs)
	{
	phys_addr_t paddr = xen_dma_to_phys(hwdev, dev_addr);

	BUG_ON(dir == DMA_NONE);

	if (!dev_is_dma_coherent(hwdev) && !(attrs & DMA_ATTR_SKIP_CPU_SYNC)) {
	if (pfn_valid(PFN_DOWN(dma_to_phys(hwdev, dev_addr))))
	arch_sync_dma_for_cpu(paddr, size, dir);
	else
	xen_dma_sync_for_cpu(hwdev, dev_addr, size, dir);
	}

	/* NOTE: We use dev_addr here, not paddr! */
	if (is_xen_swiotlb_buffer(hwdev, dev_addr))
	swiotlb_tbl_unmap_single(hwdev, paddr, size, dir, attrs);
	}

	static void
	xen_swiotlb_sync_single_for_cpu(struct device *dev, dma_addr_t dma_addr,
	size_t size, enum dma_data_direction dir)
	{
	phys_addr_t paddr = xen_dma_to_phys(dev, dma_addr);

	if (!dev_is_dma_coherent(dev)) {
	if (pfn_valid(PFN_DOWN(dma_to_phys(dev, dma_addr))))
	arch_sync_dma_for_cpu(paddr, size, dir);
	else
	xen_dma_sync_for_cpu(dev, dma_addr, size, dir);
	}

	if (is_xen_swiotlb_buffer(dev, dma_addr))
	swiotlb_sync_single_for_cpu(dev, paddr, size, dir);
	}

	static void
	xen_swiotlb_sync_single_for_device(struct device *dev, dma_addr_t dma_addr,
	size_t size, enum dma_data_direction dir)
	{
	phys_addr_t paddr = xen_dma_to_phys(dev, dma_addr);

	if (is_xen_swiotlb_buffer(dev, dma_addr))
	swiotlb_sync_single_for_device(dev, paddr, size, dir);

	if (!dev_is_dma_coherent(dev)) {
	if (pfn_valid(PFN_DOWN(dma_to_phys(dev, dma_addr))))
	arch_sync_dma_for_device(paddr, size, dir);
	else
	xen_dma_sync_for_device(dev, dma_addr, size, dir);
	}
	}

	/*
	* Unmap a set of streaming mode DMA translations. Again, cpu read rules
	* concerning calls here are the same as for swiotlb_unmap_page() above.
	*/
	static void
	xen_swiotlb_unmap_sg(struct device hwdev, struct scatterlist sgl, int nelems,
	enum dma_data_direction dir, unsigned long attrs)
	{
	struct scatterlist *sg;
	int i;

	BUG_ON(dir == DMA_NONE);

	for_each_sg(sgl, sg, nelems, i)
	xen_swiotlb_unmap_page(hwdev, sg->dma_address, sg_dma_len(sg),
	dir, attrs);

	}

	static int
	xen_swiotlb_map_sg(struct device dev, struct scatterlist sgl, int nelems,
	enum dma_data_direction dir, unsigned long attrs)
	{
	struct scatterlist *sg;
	int i;

	BUG_ON(dir == DMA_NONE);

	for_each_sg(sgl, sg, nelems, i) {
	sg->dma_address = xen_swiotlb_map_page(dev, sg_page(sg),
	sg->offset, sg->length, dir, attrs);
	if (sg->dma_address == DMA_MAPPING_ERROR)
	goto out_unmap;
	sg_dma_len(sg) = sg->length;
	}

	return nelems;
	out_unmap:
	xen_swiotlb_unmap_sg(dev, sgl, i, dir, attrs \| DMA_ATTR_SKIP_CPU_SYNC);
	sg_dma_len(sgl) = 0;
	return -EIO;
	}

	static void
	xen_swiotlb_sync_sg_for_cpu(struct device dev, struct scatterlist sgl,
	int nelems, enum dma_data_direction dir)
	{
	struct scatterlist *sg;
	int i;

	for_each_sg(sgl, sg, nelems, i) {
	xen_swiotlb_sync_single_for_cpu(dev, sg->dma_address,
	sg->length, dir);
	}
	}

	static void
	xen_swiotlb_sync_sg_for_device(struct device dev, struct scatterlist sgl,
	int nelems, enum dma_data_direction dir)
	{
	struct scatterlist *sg;
	int i;

	for_each_sg(sgl, sg, nelems, i) {
	xen_swiotlb_sync_single_for_device(dev, sg->dma_address,
	sg->length, dir);
	}
	}

	/*
	* Return whether the given device DMA address mask can be supported
	* properly. For example, if your device can only drive the low 24-bits
	* during bus mastering, then you would pass 0x00ffffff as the mask to
	* this function.
	*/
	static int
	xen_swiotlb_dma_supported(struct device *hwdev, u64 mask)
	{
	return xen_phys_to_dma(hwdev, io_tlb_default_mem.end - 1) <= mask;
	}

	const struct dma_map_ops xen_swiotlb_dma_ops = {
	.alloc = xen_swiotlb_alloc_coherent,
	.free = xen_swiotlb_free_coherent,
	.sync_single_for_cpu = xen_swiotlb_sync_single_for_cpu,
	.sync_single_for_device = xen_swiotlb_sync_single_for_device,
	.sync_sg_for_cpu = xen_swiotlb_sync_sg_for_cpu,
	.sync_sg_for_device = xen_swiotlb_sync_sg_for_device,
	.map_sg = xen_swiotlb_map_sg,
	.unmap_sg = xen_swiotlb_unmap_sg,
	.map_page = xen_swiotlb_map_page,
	.unmap_page = xen_swiotlb_unmap_page,
	.dma_supported = xen_swiotlb_dma_supported,
	.mmap = dma_common_mmap,
	.get_sgtable = dma_common_get_sgtable,
	.alloc_pages = dma_common_alloc_pages,
	.free_pages = dma_common_free_pages,
	.max_mapping_size = swiotlb_max_mapping_size,
	};