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[Xen-devel] [PATCH] linux: move swiotlb.c to lib/swiotlb-xen.c



.. as it should have been from the time lib/swiotlb.c appeared.

As before, the patch works on 2.6.22 and was just made apply to the aged
Xen repository. It also depends on the make logic change submitted before.

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxxxx>

Index: head-2007-07-10/arch/i386/kernel/swiotlb.c
===================================================================
--- head-2007-07-10.orig/arch/i386/kernel/swiotlb.c     2007-07-10 
11:14:07.000000000 +0200
+++ /dev/null   1970-01-01 00:00:00.000000000 +0000
@@ -1,745 +0,0 @@
-/*
- * Dynamic DMA mapping support.
- *
- * This implementation is a fallback for platforms that do not support
- * I/O TLBs (aka DMA address translation hardware).
- * Copyright (C) 2000 Asit Mallick <Asit.K.Mallick@xxxxxxxxx>
- * Copyright (C) 2000 Goutham Rao <goutham.rao@xxxxxxxxx>
- * Copyright (C) 2000, 2003 Hewlett-Packard Co
- *     David Mosberger-Tang <davidm@xxxxxxxxxx>
- * Copyright (C) 2005 Keir Fraser <keir@xxxxxxxxxxxxx>
- */
-
-#include <linux/cache.h>
-#include <linux/mm.h>
-#include <linux/module.h>
-#include <linux/pci.h>
-#include <linux/spinlock.h>
-#include <linux/string.h>
-#include <linux/types.h>
-#include <linux/ctype.h>
-#include <linux/init.h>
-#include <linux/bootmem.h>
-#include <linux/highmem.h>
-#include <asm/io.h>
-#include <asm/pci.h>
-#include <asm/dma.h>
-#include <asm/uaccess.h>
-#include <xen/gnttab.h>
-#include <xen/interface/memory.h>
-#include <asm-i386/mach-xen/asm/gnttab_dma.h>
-
-int swiotlb;
-EXPORT_SYMBOL(swiotlb);
-
-#define OFFSET(val,align) ((unsigned long)((val) & ( (align) - 1)))
-
-/*
- * Maximum allowable number of contiguous slabs to map,
- * must be a power of 2.  What is the appropriate value ?
- * The complexity of {map,unmap}_single is linearly dependent on this value.
- */
-#define IO_TLB_SEGSIZE 128
-
-/*
- * log of the size of each IO TLB slab.  The number of slabs is command line
- * controllable.
- */
-#define IO_TLB_SHIFT 11
-
-int swiotlb_force;
-
-static char *iotlb_virt_start;
-static unsigned long iotlb_nslabs;
-
-/*
- * Used to do a quick range check in swiotlb_unmap_single and
- * swiotlb_sync_single_*, to see if the memory was in fact allocated by this
- * API.
- */
-static unsigned long iotlb_pfn_start, iotlb_pfn_end;
-
-/* Does the given dma address reside within the swiotlb aperture? */
-static inline int in_swiotlb_aperture(dma_addr_t dev_addr)
-{
-       unsigned long pfn = mfn_to_local_pfn(dev_addr >> PAGE_SHIFT);
-       return (pfn_valid(pfn)
-               && (pfn >= iotlb_pfn_start)
-               && (pfn < iotlb_pfn_end));
-}
-
-/*
- * When the IOMMU overflows we return a fallback buffer. This sets the size.
- */
-static unsigned long io_tlb_overflow = 32*1024;
-
-void *io_tlb_overflow_buffer;
-
-/*
- * This is a free list describing the number of free entries available from
- * each index
- */
-static unsigned int *io_tlb_list;
-static unsigned int io_tlb_index;
-
-/*
- * We need to save away the original address corresponding to a mapped entry
- * for the sync operations.
- */
-static struct phys_addr {
-       struct page *page;
-       unsigned int offset;
-} *io_tlb_orig_addr;
-
-/*
- * Protect the above data structures in the map and unmap calls
- */
-static DEFINE_SPINLOCK(io_tlb_lock);
-
-static unsigned int dma_bits;
-static unsigned int __initdata max_dma_bits = 32;
-static int __init
-setup_dma_bits(char *str)
-{
-       max_dma_bits = simple_strtoul(str, NULL, 0);
-       return 0;
-}
-__setup("dma_bits=", setup_dma_bits);
-
-static int __init
-setup_io_tlb_npages(char *str)
-{
-       /* Unlike ia64, the size is aperture in megabytes, not 'slabs'! */
-       if (isdigit(*str)) {
-               iotlb_nslabs = simple_strtoul(str, &str, 0) <<
-                       (20 - IO_TLB_SHIFT);
-               iotlb_nslabs = ALIGN(iotlb_nslabs, IO_TLB_SEGSIZE);
-               /* Round up to power of two (xen_create_contiguous_region). */
-               while (iotlb_nslabs & (iotlb_nslabs-1))
-                       iotlb_nslabs += iotlb_nslabs & ~(iotlb_nslabs-1);
-       }
-       if (*str == ',')
-               ++str;
-       /*
-         * NB. 'force' enables the swiotlb, but doesn't force its use for
-         * every DMA like it does on native Linux. 'off' forcibly disables
-         * use of the swiotlb.
-         */
-       if (!strcmp(str, "force"))
-               swiotlb_force = 1;
-       else if (!strcmp(str, "off"))
-               swiotlb_force = -1;
-       return 1;
-}
-__setup("swiotlb=", setup_io_tlb_npages);
-/* make io_tlb_overflow tunable too? */
-
-/*
- * Statically reserve bounce buffer space and initialize bounce buffer data
- * structures for the software IO TLB used to implement the PCI DMA API.
- */
-void
-swiotlb_init_with_default_size (size_t default_size)
-{
-       unsigned long i, bytes;
-       int rc;
-
-       if (!iotlb_nslabs) {
-               iotlb_nslabs = (default_size >> IO_TLB_SHIFT);
-               iotlb_nslabs = ALIGN(iotlb_nslabs, IO_TLB_SEGSIZE);
-               /* Round up to power of two (xen_create_contiguous_region). */
-               while (iotlb_nslabs & (iotlb_nslabs-1))
-                       iotlb_nslabs += iotlb_nslabs & ~(iotlb_nslabs-1);
-       }
-
-       bytes = iotlb_nslabs * (1UL << IO_TLB_SHIFT);
-
-       /*
-        * Get IO TLB memory from the low pages
-        */
-       iotlb_virt_start = alloc_bootmem_low_pages(bytes);
-       if (!iotlb_virt_start)
-               panic("Cannot allocate SWIOTLB buffer!\n");
-
-       dma_bits = get_order(IO_TLB_SEGSIZE << IO_TLB_SHIFT) + PAGE_SHIFT;
-       for (i = 0; i < iotlb_nslabs; i += IO_TLB_SEGSIZE) {
-               do {
-                       rc = xen_create_contiguous_region(
-                               (unsigned long)iotlb_virt_start + (i << 
IO_TLB_SHIFT),
-                               get_order(IO_TLB_SEGSIZE << IO_TLB_SHIFT),
-                               dma_bits);
-               } while (rc && dma_bits++ < max_dma_bits);
-               if (rc) {
-                       if (i == 0)
-                               panic("No suitable physical memory available 
for SWIOTLB buffer!\n"
-                                     "Use dom0_mem Xen boot parameter to 
reserve\n"
-                                     "some DMA memory (e.g., 
dom0_mem=-128M).\n");
-                       iotlb_nslabs = i;
-                       i <<= IO_TLB_SHIFT;
-                       free_bootmem(__pa(iotlb_virt_start + i), bytes - i);
-                       bytes = i;
-                       for (dma_bits = 0; i > 0; i -= IO_TLB_SEGSIZE << 
IO_TLB_SHIFT) {
-                               unsigned int bits = 
fls64(virt_to_bus(iotlb_virt_start + i - 1));
-
-                               if (bits > dma_bits)
-                                       dma_bits = bits;
-                       }
-                       break;
-               }
-       }
-
-       /*
-        * Allocate and initialize the free list array.  This array is used
-        * to find contiguous free memory regions of size up to IO_TLB_SEGSIZE.
-        */
-       io_tlb_list = alloc_bootmem(iotlb_nslabs * sizeof(int));
-       for (i = 0; i < iotlb_nslabs; i++)
-               io_tlb_list[i] = IO_TLB_SEGSIZE - OFFSET(i, IO_TLB_SEGSIZE);
-       io_tlb_index = 0;
-       io_tlb_orig_addr = alloc_bootmem(
-               iotlb_nslabs * sizeof(*io_tlb_orig_addr));
-
-       /*
-        * Get the overflow emergency buffer
-        */
-       io_tlb_overflow_buffer = alloc_bootmem_low(io_tlb_overflow);
-       if (!io_tlb_overflow_buffer)
-               panic("Cannot allocate SWIOTLB overflow buffer!\n");
-
-       do {
-               rc = xen_create_contiguous_region(
-                       (unsigned long)io_tlb_overflow_buffer,
-                       get_order(io_tlb_overflow),
-                       dma_bits);
-       } while (rc && dma_bits++ < max_dma_bits);
-       if (rc)
-               panic("No suitable physical memory available for SWIOTLB 
overflow buffer!\n");
-
-       iotlb_pfn_start = __pa(iotlb_virt_start) >> PAGE_SHIFT;
-       iotlb_pfn_end   = iotlb_pfn_start + (bytes >> PAGE_SHIFT);
-
-       printk(KERN_INFO "Software IO TLB enabled: \n"
-              " Aperture:     %lu megabytes\n"
-              " Kernel range: %p - %p\n"
-              " Address size: %u bits\n",
-              bytes >> 20,
-              iotlb_virt_start, iotlb_virt_start + bytes,
-              dma_bits);
-}
-
-void
-swiotlb_init(void)
-{
-       long ram_end;
-       size_t defsz = 64 * (1 << 20); /* 64MB default size */
-
-       if (swiotlb_force == 1) {
-               swiotlb = 1;
-       } else if ((swiotlb_force != -1) &&
-                  is_running_on_xen() &&
-                  is_initial_xendomain()) {
-               /* Domain 0 always has a swiotlb. */
-               ram_end = HYPERVISOR_memory_op(XENMEM_maximum_ram_page, NULL);
-               if (ram_end <= 0x7ffff)
-                       defsz = 2 * (1 << 20); /* 2MB on <2GB on systems. */
-               swiotlb = 1;
-       }
-
-       if (swiotlb)
-               swiotlb_init_with_default_size(defsz);
-       else
-               printk(KERN_INFO "Software IO TLB disabled\n");
-}
-
-/*
- * We use __copy_to_user_inatomic to transfer to the host buffer because the
- * buffer may be mapped read-only (e.g, in blkback driver) but lower-level
- * drivers map the buffer for DMA_BIDIRECTIONAL access. This causes an
- * unnecessary copy from the aperture to the host buffer, and a page fault.
- */
-static void
-__sync_single(struct phys_addr buffer, char *dma_addr, size_t size, int dir)
-{
-       if (PageHighMem(buffer.page)) {
-               size_t len, bytes;
-               char *dev, *host, *kmp;
-               len = size;
-               while (len != 0) {
-                       unsigned long flags;
-
-                       if (((bytes = len) + buffer.offset) > PAGE_SIZE)
-                               bytes = PAGE_SIZE - buffer.offset;
-                       local_irq_save(flags); /* protects KM_BOUNCE_READ */
-                       kmp  = kmap_atomic(buffer.page, KM_BOUNCE_READ);
-                       dev  = dma_addr + size - len;
-                       host = kmp + buffer.offset;
-                       if (dir == DMA_FROM_DEVICE) {
-                               if (__copy_to_user_inatomic(host, dev, bytes))
-                                       /* inaccessible */;
-                       } else
-                               memcpy(dev, host, bytes);
-                       kunmap_atomic(kmp, KM_BOUNCE_READ);
-                       local_irq_restore(flags);
-                       len -= bytes;
-                       buffer.page++;
-                       buffer.offset = 0;
-               }
-       } else {
-               char *host = (char *)phys_to_virt(
-                       page_to_pseudophys(buffer.page)) + buffer.offset;
-               if (dir == DMA_FROM_DEVICE) {
-                       if (__copy_to_user_inatomic(host, dma_addr, size))
-                               /* inaccessible */;
-               } else if (dir == DMA_TO_DEVICE)
-                       memcpy(dma_addr, host, size);
-       }
-}
-
-/*
- * Allocates bounce buffer and returns its kernel virtual address.
- */
-static void *
-map_single(struct device *hwdev, struct phys_addr buffer, size_t size, int dir)
-{
-       unsigned long flags;
-       char *dma_addr;
-       unsigned int nslots, stride, index, wrap;
-       struct phys_addr slot_buf;
-       int i;
-
-       /*
-        * For mappings greater than a page, we limit the stride (and
-        * hence alignment) to a page size.
-        */
-       nslots = ALIGN(size, 1 << IO_TLB_SHIFT) >> IO_TLB_SHIFT;
-       if (size > PAGE_SIZE)
-               stride = (1 << (PAGE_SHIFT - IO_TLB_SHIFT));
-       else
-               stride = 1;
-
-       BUG_ON(!nslots);
-
-       /*
-        * Find suitable number of IO TLB entries size that will fit this
-        * request and allocate a buffer from that IO TLB pool.
-        */
-       spin_lock_irqsave(&io_tlb_lock, flags);
-       {
-               wrap = index = ALIGN(io_tlb_index, stride);
-
-               if (index >= iotlb_nslabs)
-                       wrap = index = 0;
-
-               do {
-                       /*
-                        * If we find a slot that indicates we have 'nslots'
-                        * number of contiguous buffers, we allocate the
-                        * buffers from that slot and mark the entries as '0'
-                        * indicating unavailable.
-                        */
-                       if (io_tlb_list[index] >= nslots) {
-                               int count = 0;
-
-                               for (i = index; i < (int)(index + nslots); i++)
-                                       io_tlb_list[i] = 0;
-                               for (i = index - 1;
-                                    (OFFSET(i, IO_TLB_SEGSIZE) !=
-                                     IO_TLB_SEGSIZE -1) && io_tlb_list[i];
-                                    i--)
-                                       io_tlb_list[i] = ++count;
-                               dma_addr = iotlb_virt_start +
-                                       (index << IO_TLB_SHIFT);
-
-                               /*
-                                * Update the indices to avoid searching in
-                                * the next round.
-                                */
-                               io_tlb_index = 
-                                       ((index + nslots) < iotlb_nslabs
-                                        ? (index + nslots) : 0);
-
-                               goto found;
-                       }
-                       index += stride;
-                       if (index >= iotlb_nslabs)
-                               index = 0;
-               } while (index != wrap);
-
-               spin_unlock_irqrestore(&io_tlb_lock, flags);
-               return NULL;
-       }
-  found:
-       spin_unlock_irqrestore(&io_tlb_lock, flags);
-
-       /*
-        * Save away the mapping from the original address to the DMA address.
-        * This is needed when we sync the memory.  Then we sync the buffer if
-        * needed.
-        */
-       slot_buf = buffer;
-       for (i = 0; i < nslots; i++) {
-               slot_buf.page += slot_buf.offset >> PAGE_SHIFT;
-               slot_buf.offset &= PAGE_SIZE - 1;
-               io_tlb_orig_addr[index+i] = slot_buf;
-               slot_buf.offset += 1 << IO_TLB_SHIFT;
-       }
-       if ((dir == DMA_TO_DEVICE) || (dir == DMA_BIDIRECTIONAL))
-               __sync_single(buffer, dma_addr, size, DMA_TO_DEVICE);
-
-       return dma_addr;
-}
-
-struct phys_addr dma_addr_to_phys_addr(char *dma_addr)
-{
-       int index = (dma_addr - iotlb_virt_start) >> IO_TLB_SHIFT;
-       struct phys_addr buffer = io_tlb_orig_addr[index];
-       buffer.offset += (long)dma_addr & ((1 << IO_TLB_SHIFT) - 1);
-       buffer.page += buffer.offset >> PAGE_SHIFT;
-       buffer.offset &= PAGE_SIZE - 1;
-       return buffer;
-}
-
-/*
- * dma_addr is the kernel virtual address of the bounce buffer to unmap.
- */
-static void
-unmap_single(struct device *hwdev, char *dma_addr, size_t size, int dir)
-{
-       unsigned long flags;
-       int i, count, nslots = ALIGN(size, 1 << IO_TLB_SHIFT) >> IO_TLB_SHIFT;
-       int index = (dma_addr - iotlb_virt_start) >> IO_TLB_SHIFT;
-       struct phys_addr buffer = dma_addr_to_phys_addr(dma_addr);
-
-       /*
-        * First, sync the memory before unmapping the entry
-        */
-       if ((dir == DMA_FROM_DEVICE) || (dir == DMA_BIDIRECTIONAL))
-               __sync_single(buffer, dma_addr, size, DMA_FROM_DEVICE);
-
-       /*
-        * Return the buffer to the free list by setting the corresponding
-        * entries to indicate the number of contigous entries available.
-        * While returning the entries to the free list, we merge the entries
-        * with slots below and above the pool being returned.
-        */
-       spin_lock_irqsave(&io_tlb_lock, flags);
-       {
-               count = ((index + nslots) < ALIGN(index + 1, IO_TLB_SEGSIZE) ?
-                        io_tlb_list[index + nslots] : 0);
-               /*
-                * Step 1: return the slots to the free list, merging the
-                * slots with superceeding slots
-                */
-               for (i = index + nslots - 1; i >= index; i--)
-                       io_tlb_list[i] = ++count;
-               /*
-                * Step 2: merge the returned slots with the preceding slots,
-                * if available (non zero)
-                */
-               for (i = index - 1;
-                    (OFFSET(i, IO_TLB_SEGSIZE) !=
-                     IO_TLB_SEGSIZE -1) && io_tlb_list[i];
-                    i--)
-                       io_tlb_list[i] = ++count;
-       }
-       spin_unlock_irqrestore(&io_tlb_lock, flags);
-}
-
-static void
-sync_single(struct device *hwdev, char *dma_addr, size_t size, int dir)
-{
-       struct phys_addr buffer = dma_addr_to_phys_addr(dma_addr);
-       BUG_ON((dir != DMA_FROM_DEVICE) && (dir != DMA_TO_DEVICE));
-       __sync_single(buffer, dma_addr, size, dir);
-}
-
-static void
-swiotlb_full(struct device *dev, size_t size, int dir, int do_panic)
-{
-       /*
-        * Ran out of IOMMU space for this operation. This is very bad.
-        * Unfortunately the drivers cannot handle this operation properly.
-        * unless they check for pci_dma_mapping_error (most don't)
-        * When the mapping is small enough return a static buffer to limit
-        * the damage, or panic when the transfer is too big.
-        */
-       printk(KERN_ERR "PCI-DMA: Out of SW-IOMMU space for %lu bytes at "
-              "device %s\n", (unsigned long)size, dev ? dev->bus_id : "?");
-
-       if (size > io_tlb_overflow && do_panic) {
-               if (dir == PCI_DMA_FROMDEVICE || dir == PCI_DMA_BIDIRECTIONAL)
-                       panic("PCI-DMA: Memory would be corrupted\n");
-               if (dir == PCI_DMA_TODEVICE || dir == PCI_DMA_BIDIRECTIONAL)
-                       panic("PCI-DMA: Random memory would be DMAed\n");
-       }
-}
-
-/*
- * Map a single buffer of the indicated size for DMA in streaming mode.  The
- * PCI address to use is returned.
- *
- * Once the device is given the dma address, the device owns this memory until
- * either swiotlb_unmap_single or swiotlb_dma_sync_single is performed.
- */
-dma_addr_t
-swiotlb_map_single(struct device *hwdev, void *ptr, size_t size, int dir)
-{
-       dma_addr_t dev_addr = gnttab_dma_map_page(virt_to_page(ptr)) +
-                             offset_in_page(ptr);
-       void *map;
-       struct phys_addr buffer;
-
-       BUG_ON(dir == DMA_NONE);
-
-       /*
-        * If the pointer passed in happens to be in the device's DMA window,
-        * we can safely return the device addr and not worry about bounce
-        * buffering it.
-        */
-       if (!range_straddles_page_boundary(__pa(ptr), size) &&
-           !address_needs_mapping(hwdev, dev_addr))
-               return dev_addr;
-
-       /*
-        * Oh well, have to allocate and map a bounce buffer.
-        */
-       gnttab_dma_unmap_page(dev_addr);
-       buffer.page   = virt_to_page(ptr);
-       buffer.offset = (unsigned long)ptr & ~PAGE_MASK;
-       map = map_single(hwdev, buffer, size, dir);
-       if (!map) {
-               swiotlb_full(hwdev, size, dir, 1);
-               map = io_tlb_overflow_buffer;
-       }
-
-       dev_addr = virt_to_bus(map);
-       return dev_addr;
-}
-
-/*
- * Unmap a single streaming mode DMA translation.  The dma_addr and size must
- * match what was provided for in a previous swiotlb_map_single 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.
- */
-void
-swiotlb_unmap_single(struct device *hwdev, dma_addr_t dev_addr, size_t size,
-                    int dir)
-{
-       BUG_ON(dir == DMA_NONE);
-       if (in_swiotlb_aperture(dev_addr))
-               unmap_single(hwdev, bus_to_virt(dev_addr), size, dir);
-       else
-               gnttab_dma_unmap_page(dev_addr);
-}
-
-/*
- * Make physical memory consistent for a single streaming mode DMA translation
- * after a transfer.
- *
- * If you perform a swiotlb_map_single() but wish to interrogate the buffer
- * using the cpu, yet do not wish to teardown the PCI dma mapping, you must
- * call this function before doing so.  At the next point you give the PCI dma
- * address back to the card, you must first perform a
- * swiotlb_dma_sync_for_device, and then the device again owns the buffer
- */
-void
-swiotlb_sync_single_for_cpu(struct device *hwdev, dma_addr_t dev_addr,
-                           size_t size, int dir)
-{
-       BUG_ON(dir == DMA_NONE);
-       if (in_swiotlb_aperture(dev_addr))
-               sync_single(hwdev, bus_to_virt(dev_addr), size, dir);
-}
-
-void
-swiotlb_sync_single_for_device(struct device *hwdev, dma_addr_t dev_addr,
-                              size_t size, int dir)
-{
-       BUG_ON(dir == DMA_NONE);
-       if (in_swiotlb_aperture(dev_addr))
-               sync_single(hwdev, bus_to_virt(dev_addr), size, dir);
-}
-
-/*
- * Map a set of buffers described by scatterlist in streaming mode for DMA.
- * This is the scatter-gather version of the above swiotlb_map_single
- * interface.  Here the scatter gather list elements are each tagged with the
- * appropriate dma address and length.  They are obtained via
- * sg_dma_{address,length}(SG).
- *
- * NOTE: An implementation may be able to use a smaller number of
- *       DMA address/length pairs than there are SG table elements.
- *       (for example via virtual mapping capabilities)
- *       The routine returns the number of addr/length pairs actually
- *       used, at most nents.
- *
- * Device ownership issues as mentioned above for swiotlb_map_single are the
- * same here.
- */
-int
-swiotlb_map_sg(struct device *hwdev, struct scatterlist *sg, int nelems,
-              int dir)
-{
-       struct phys_addr buffer;
-       dma_addr_t dev_addr;
-       char *map;
-       int i;
-
-       BUG_ON(dir == DMA_NONE);
-
-       for (i = 0; i < nelems; i++, sg++) {
-               dev_addr = gnttab_dma_map_page(sg->page) + sg->offset;
-
-               if (range_straddles_page_boundary(page_to_pseudophys(sg->page)
-                                                 + sg->offset, sg->length)
-                   || address_needs_mapping(hwdev, dev_addr)) {
-                       gnttab_dma_unmap_page(dev_addr);
-                       buffer.page   = sg->page;
-                       buffer.offset = sg->offset;
-                       map = map_single(hwdev, buffer, sg->length, dir);
-                       if (!map) {
-                               /* Don't panic here, we expect map_sg users
-                                  to do proper error handling. */
-                               swiotlb_full(hwdev, sg->length, dir, 0);
-                               swiotlb_unmap_sg(hwdev, sg - i, i, dir);
-                               sg[0].dma_length = 0;
-                               return 0;
-                       }
-                       sg->dma_address = (dma_addr_t)virt_to_bus(map);
-               } else
-                       sg->dma_address = dev_addr;
-               sg->dma_length = sg->length;
-       }
-       return nelems;
-}
-
-/*
- * Unmap a set of streaming mode DMA translations.  Again, cpu read rules
- * concerning calls here are the same as for swiotlb_unmap_single() above.
- */
-void
-swiotlb_unmap_sg(struct device *hwdev, struct scatterlist *sg, int nelems,
-                int dir)
-{
-       int i;
-
-       BUG_ON(dir == DMA_NONE);
-
-       for (i = 0; i < nelems; i++, sg++)
-               if (in_swiotlb_aperture(sg->dma_address))
-                       unmap_single(hwdev, 
-                                    (void *)bus_to_virt(sg->dma_address),
-                                    sg->dma_length, dir);
-               else
-                       gnttab_dma_unmap_page(sg->dma_address);
-}
-
-/*
- * Make physical memory consistent for a set of streaming mode DMA translations
- * after a transfer.
- *
- * The same as swiotlb_sync_single_* but for a scatter-gather list, same rules
- * and usage.
- */
-void
-swiotlb_sync_sg_for_cpu(struct device *hwdev, struct scatterlist *sg,
-                       int nelems, int dir)
-{
-       int i;
-
-       BUG_ON(dir == DMA_NONE);
-
-       for (i = 0; i < nelems; i++, sg++)
-               if (in_swiotlb_aperture(sg->dma_address))
-                       sync_single(hwdev,
-                                   (void *)bus_to_virt(sg->dma_address),
-                                   sg->dma_length, dir);
-}
-
-void
-swiotlb_sync_sg_for_device(struct device *hwdev, struct scatterlist *sg,
-                          int nelems, int dir)
-{
-       int i;
-
-       BUG_ON(dir == DMA_NONE);
-
-       for (i = 0; i < nelems; i++, sg++)
-               if (in_swiotlb_aperture(sg->dma_address))
-                       sync_single(hwdev,
-                                   (void *)bus_to_virt(sg->dma_address),
-                                   sg->dma_length, dir);
-}
-
-#ifdef CONFIG_HIGHMEM
-
-dma_addr_t
-swiotlb_map_page(struct device *hwdev, struct page *page,
-                unsigned long offset, size_t size,
-                enum dma_data_direction direction)
-{
-       struct phys_addr buffer;
-       dma_addr_t dev_addr;
-       char *map;
-
-       dev_addr = gnttab_dma_map_page(page) + offset;
-       if (address_needs_mapping(hwdev, dev_addr)) {
-               gnttab_dma_unmap_page(dev_addr);
-               buffer.page   = page;
-               buffer.offset = offset;
-               map = map_single(hwdev, buffer, size, direction);
-               if (!map) {
-                       swiotlb_full(hwdev, size, direction, 1);
-                       map = io_tlb_overflow_buffer;
-               }
-               dev_addr = (dma_addr_t)virt_to_bus(map);
-       }
-
-       return dev_addr;
-}
-
-void
-swiotlb_unmap_page(struct device *hwdev, dma_addr_t dma_address,
-                  size_t size, enum dma_data_direction direction)
-{
-       BUG_ON(direction == DMA_NONE);
-       if (in_swiotlb_aperture(dma_address))
-               unmap_single(hwdev, bus_to_virt(dma_address), size, direction);
-       else
-               gnttab_dma_unmap_page(dma_address);
-}
-
-#endif
-
-int
-swiotlb_dma_mapping_error(dma_addr_t dma_addr)
-{
-       return (dma_addr == virt_to_bus(io_tlb_overflow_buffer));
-}
-
-/*
- * Return whether the given PCI device DMA address mask can be supported
- * properly.  For example, if your device can only drive the low 24-bits
- * during PCI bus mastering, then you would pass 0x00ffffff as the mask to
- * this function.
- */
-int
-swiotlb_dma_supported (struct device *hwdev, u64 mask)
-{
-       return (mask >= ((1UL << dma_bits) - 1));
-}
-
-EXPORT_SYMBOL(swiotlb_init);
-EXPORT_SYMBOL(swiotlb_map_single);
-EXPORT_SYMBOL(swiotlb_unmap_single);
-EXPORT_SYMBOL(swiotlb_map_sg);
-EXPORT_SYMBOL(swiotlb_unmap_sg);
-EXPORT_SYMBOL(swiotlb_sync_single_for_cpu);
-EXPORT_SYMBOL(swiotlb_sync_single_for_device);
-EXPORT_SYMBOL(swiotlb_sync_sg_for_cpu);
-EXPORT_SYMBOL(swiotlb_sync_sg_for_device);
-EXPORT_SYMBOL(swiotlb_dma_mapping_error);
-EXPORT_SYMBOL(swiotlb_dma_supported);
Index: head-2007-07-10/lib/Makefile
===================================================================
--- head-2007-07-10.orig/lib/Makefile   2007-07-10 10:29:24.000000000 +0200
+++ head-2007-07-10/lib/Makefile        2007-07-10 11:20:35.000000000 +0200
@@ -58,9 +58,6 @@ obj-$(CONFIG_SMP) += percpu_counter.o
 obj-$(CONFIG_AUDIT_GENERIC) += audit.o
 
 obj-$(CONFIG_SWIOTLB) += swiotlb.o
-ifeq ($(CONFIG_X86),y)
-swiotlb-$(CONFIG_XEN) := ../arch/i386/kernel/swiotlb.o
-endif
 ifeq ($(CONFIG_IA64),y)
 swiotlb-$(CONFIG_XEN) := ../arch/ia64/xen/swiotlb.o
 endif
Index: head-2007-07-10/lib/swiotlb-xen.c
===================================================================
--- /dev/null   1970-01-01 00:00:00.000000000 +0000
+++ head-2007-07-10/lib/swiotlb-xen.c   2007-07-10 11:20:35.000000000 +0200
@@ -0,0 +1,745 @@
+/*
+ * Dynamic DMA mapping support.
+ *
+ * This implementation is a fallback for platforms that do not support
+ * I/O TLBs (aka DMA address translation hardware).
+ * Copyright (C) 2000 Asit Mallick <Asit.K.Mallick@xxxxxxxxx>
+ * Copyright (C) 2000 Goutham Rao <goutham.rao@xxxxxxxxx>
+ * Copyright (C) 2000, 2003 Hewlett-Packard Co
+ *     David Mosberger-Tang <davidm@xxxxxxxxxx>
+ * Copyright (C) 2005 Keir Fraser <keir@xxxxxxxxxxxxx>
+ */
+
+#include <linux/cache.h>
+#include <linux/mm.h>
+#include <linux/module.h>
+#include <linux/pci.h>
+#include <linux/spinlock.h>
+#include <linux/string.h>
+#include <linux/types.h>
+#include <linux/ctype.h>
+#include <linux/init.h>
+#include <linux/bootmem.h>
+#include <linux/highmem.h>
+#include <asm/io.h>
+#include <asm/pci.h>
+#include <asm/dma.h>
+#include <asm/uaccess.h>
+#include <xen/gnttab.h>
+#include <xen/interface/memory.h>
+#include <asm-i386/mach-xen/asm/gnttab_dma.h>
+
+int swiotlb;
+EXPORT_SYMBOL(swiotlb);
+
+#define OFFSET(val,align) ((unsigned long)((val) & ( (align) - 1)))
+
+/*
+ * Maximum allowable number of contiguous slabs to map,
+ * must be a power of 2.  What is the appropriate value ?
+ * The complexity of {map,unmap}_single is linearly dependent on this value.
+ */
+#define IO_TLB_SEGSIZE 128
+
+/*
+ * log of the size of each IO TLB slab.  The number of slabs is command line
+ * controllable.
+ */
+#define IO_TLB_SHIFT 11
+
+int swiotlb_force;
+
+static char *iotlb_virt_start;
+static unsigned long iotlb_nslabs;
+
+/*
+ * Used to do a quick range check in swiotlb_unmap_single and
+ * swiotlb_sync_single_*, to see if the memory was in fact allocated by this
+ * API.
+ */
+static unsigned long iotlb_pfn_start, iotlb_pfn_end;
+
+/* Does the given dma address reside within the swiotlb aperture? */
+static inline int in_swiotlb_aperture(dma_addr_t dev_addr)
+{
+       unsigned long pfn = mfn_to_local_pfn(dev_addr >> PAGE_SHIFT);
+       return (pfn_valid(pfn)
+               && (pfn >= iotlb_pfn_start)
+               && (pfn < iotlb_pfn_end));
+}
+
+/*
+ * When the IOMMU overflows we return a fallback buffer. This sets the size.
+ */
+static unsigned long io_tlb_overflow = 32*1024;
+
+void *io_tlb_overflow_buffer;
+
+/*
+ * This is a free list describing the number of free entries available from
+ * each index
+ */
+static unsigned int *io_tlb_list;
+static unsigned int io_tlb_index;
+
+/*
+ * We need to save away the original address corresponding to a mapped entry
+ * for the sync operations.
+ */
+static struct phys_addr {
+       struct page *page;
+       unsigned int offset;
+} *io_tlb_orig_addr;
+
+/*
+ * Protect the above data structures in the map and unmap calls
+ */
+static DEFINE_SPINLOCK(io_tlb_lock);
+
+static unsigned int dma_bits;
+static unsigned int __initdata max_dma_bits = 32;
+static int __init
+setup_dma_bits(char *str)
+{
+       max_dma_bits = simple_strtoul(str, NULL, 0);
+       return 0;
+}
+__setup("dma_bits=", setup_dma_bits);
+
+static int __init
+setup_io_tlb_npages(char *str)
+{
+       /* Unlike ia64, the size is aperture in megabytes, not 'slabs'! */
+       if (isdigit(*str)) {
+               iotlb_nslabs = simple_strtoul(str, &str, 0) <<
+                       (20 - IO_TLB_SHIFT);
+               iotlb_nslabs = ALIGN(iotlb_nslabs, IO_TLB_SEGSIZE);
+               /* Round up to power of two (xen_create_contiguous_region). */
+               while (iotlb_nslabs & (iotlb_nslabs-1))
+                       iotlb_nslabs += iotlb_nslabs & ~(iotlb_nslabs-1);
+       }
+       if (*str == ',')
+               ++str;
+       /*
+         * NB. 'force' enables the swiotlb, but doesn't force its use for
+         * every DMA like it does on native Linux. 'off' forcibly disables
+         * use of the swiotlb.
+         */
+       if (!strcmp(str, "force"))
+               swiotlb_force = 1;
+       else if (!strcmp(str, "off"))
+               swiotlb_force = -1;
+       return 1;
+}
+__setup("swiotlb=", setup_io_tlb_npages);
+/* make io_tlb_overflow tunable too? */
+
+/*
+ * Statically reserve bounce buffer space and initialize bounce buffer data
+ * structures for the software IO TLB used to implement the PCI DMA API.
+ */
+void
+swiotlb_init_with_default_size (size_t default_size)
+{
+       unsigned long i, bytes;
+       int rc;
+
+       if (!iotlb_nslabs) {
+               iotlb_nslabs = (default_size >> IO_TLB_SHIFT);
+               iotlb_nslabs = ALIGN(iotlb_nslabs, IO_TLB_SEGSIZE);
+               /* Round up to power of two (xen_create_contiguous_region). */
+               while (iotlb_nslabs & (iotlb_nslabs-1))
+                       iotlb_nslabs += iotlb_nslabs & ~(iotlb_nslabs-1);
+       }
+
+       bytes = iotlb_nslabs * (1UL << IO_TLB_SHIFT);
+
+       /*
+        * Get IO TLB memory from the low pages
+        */
+       iotlb_virt_start = alloc_bootmem_low_pages(bytes);
+       if (!iotlb_virt_start)
+               panic("Cannot allocate SWIOTLB buffer!\n");
+
+       dma_bits = get_order(IO_TLB_SEGSIZE << IO_TLB_SHIFT) + PAGE_SHIFT;
+       for (i = 0; i < iotlb_nslabs; i += IO_TLB_SEGSIZE) {
+               do {
+                       rc = xen_create_contiguous_region(
+                               (unsigned long)iotlb_virt_start + (i << 
IO_TLB_SHIFT),
+                               get_order(IO_TLB_SEGSIZE << IO_TLB_SHIFT),
+                               dma_bits);
+               } while (rc && dma_bits++ < max_dma_bits);
+               if (rc) {
+                       if (i == 0)
+                               panic("No suitable physical memory available 
for SWIOTLB buffer!\n"
+                                     "Use dom0_mem Xen boot parameter to 
reserve\n"
+                                     "some DMA memory (e.g., 
dom0_mem=-128M).\n");
+                       iotlb_nslabs = i;
+                       i <<= IO_TLB_SHIFT;
+                       free_bootmem(__pa(iotlb_virt_start + i), bytes - i);
+                       bytes = i;
+                       for (dma_bits = 0; i > 0; i -= IO_TLB_SEGSIZE << 
IO_TLB_SHIFT) {
+                               unsigned int bits = 
fls64(virt_to_bus(iotlb_virt_start + i - 1));
+
+                               if (bits > dma_bits)
+                                       dma_bits = bits;
+                       }
+                       break;
+               }
+       }
+
+       /*
+        * Allocate and initialize the free list array.  This array is used
+        * to find contiguous free memory regions of size up to IO_TLB_SEGSIZE.
+        */
+       io_tlb_list = alloc_bootmem(iotlb_nslabs * sizeof(int));
+       for (i = 0; i < iotlb_nslabs; i++)
+               io_tlb_list[i] = IO_TLB_SEGSIZE - OFFSET(i, IO_TLB_SEGSIZE);
+       io_tlb_index = 0;
+       io_tlb_orig_addr = alloc_bootmem(
+               iotlb_nslabs * sizeof(*io_tlb_orig_addr));
+
+       /*
+        * Get the overflow emergency buffer
+        */
+       io_tlb_overflow_buffer = alloc_bootmem_low(io_tlb_overflow);
+       if (!io_tlb_overflow_buffer)
+               panic("Cannot allocate SWIOTLB overflow buffer!\n");
+
+       do {
+               rc = xen_create_contiguous_region(
+                       (unsigned long)io_tlb_overflow_buffer,
+                       get_order(io_tlb_overflow),
+                       dma_bits);
+       } while (rc && dma_bits++ < max_dma_bits);
+       if (rc)
+               panic("No suitable physical memory available for SWIOTLB 
overflow buffer!\n");
+
+       iotlb_pfn_start = __pa(iotlb_virt_start) >> PAGE_SHIFT;
+       iotlb_pfn_end   = iotlb_pfn_start + (bytes >> PAGE_SHIFT);
+
+       printk(KERN_INFO "Software IO TLB enabled: \n"
+              " Aperture:     %lu megabytes\n"
+              " Kernel range: %p - %p\n"
+              " Address size: %u bits\n",
+              bytes >> 20,
+              iotlb_virt_start, iotlb_virt_start + bytes,
+              dma_bits);
+}
+
+void
+swiotlb_init(void)
+{
+       long ram_end;
+       size_t defsz = 64 * (1 << 20); /* 64MB default size */
+
+       if (swiotlb_force == 1) {
+               swiotlb = 1;
+       } else if ((swiotlb_force != -1) &&
+                  is_running_on_xen() &&
+                  is_initial_xendomain()) {
+               /* Domain 0 always has a swiotlb. */
+               ram_end = HYPERVISOR_memory_op(XENMEM_maximum_ram_page, NULL);
+               if (ram_end <= 0x7ffff)
+                       defsz = 2 * (1 << 20); /* 2MB on <2GB on systems. */
+               swiotlb = 1;
+       }
+
+       if (swiotlb)
+               swiotlb_init_with_default_size(defsz);
+       else
+               printk(KERN_INFO "Software IO TLB disabled\n");
+}
+
+/*
+ * We use __copy_to_user_inatomic to transfer to the host buffer because the
+ * buffer may be mapped read-only (e.g, in blkback driver) but lower-level
+ * drivers map the buffer for DMA_BIDIRECTIONAL access. This causes an
+ * unnecessary copy from the aperture to the host buffer, and a page fault.
+ */
+static void
+__sync_single(struct phys_addr buffer, char *dma_addr, size_t size, int dir)
+{
+       if (PageHighMem(buffer.page)) {
+               size_t len, bytes;
+               char *dev, *host, *kmp;
+               len = size;
+               while (len != 0) {
+                       unsigned long flags;
+
+                       if (((bytes = len) + buffer.offset) > PAGE_SIZE)
+                               bytes = PAGE_SIZE - buffer.offset;
+                       local_irq_save(flags); /* protects KM_BOUNCE_READ */
+                       kmp  = kmap_atomic(buffer.page, KM_BOUNCE_READ);
+                       dev  = dma_addr + size - len;
+                       host = kmp + buffer.offset;
+                       if (dir == DMA_FROM_DEVICE) {
+                               if (__copy_to_user_inatomic(host, dev, bytes))
+                                       /* inaccessible */;
+                       } else
+                               memcpy(dev, host, bytes);
+                       kunmap_atomic(kmp, KM_BOUNCE_READ);
+                       local_irq_restore(flags);
+                       len -= bytes;
+                       buffer.page++;
+                       buffer.offset = 0;
+               }
+       } else {
+               char *host = (char *)phys_to_virt(
+                       page_to_pseudophys(buffer.page)) + buffer.offset;
+               if (dir == DMA_FROM_DEVICE) {
+                       if (__copy_to_user_inatomic(host, dma_addr, size))
+                               /* inaccessible */;
+               } else if (dir == DMA_TO_DEVICE)
+                       memcpy(dma_addr, host, size);
+       }
+}
+
+/*
+ * Allocates bounce buffer and returns its kernel virtual address.
+ */
+static void *
+map_single(struct device *hwdev, struct phys_addr buffer, size_t size, int dir)
+{
+       unsigned long flags;
+       char *dma_addr;
+       unsigned int nslots, stride, index, wrap;
+       struct phys_addr slot_buf;
+       int i;
+
+       /*
+        * For mappings greater than a page, we limit the stride (and
+        * hence alignment) to a page size.
+        */
+       nslots = ALIGN(size, 1 << IO_TLB_SHIFT) >> IO_TLB_SHIFT;
+       if (size > PAGE_SIZE)
+               stride = (1 << (PAGE_SHIFT - IO_TLB_SHIFT));
+       else
+               stride = 1;
+
+       BUG_ON(!nslots);
+
+       /*
+        * Find suitable number of IO TLB entries size that will fit this
+        * request and allocate a buffer from that IO TLB pool.
+        */
+       spin_lock_irqsave(&io_tlb_lock, flags);
+       {
+               wrap = index = ALIGN(io_tlb_index, stride);
+
+               if (index >= iotlb_nslabs)
+                       wrap = index = 0;
+
+               do {
+                       /*
+                        * If we find a slot that indicates we have 'nslots'
+                        * number of contiguous buffers, we allocate the
+                        * buffers from that slot and mark the entries as '0'
+                        * indicating unavailable.
+                        */
+                       if (io_tlb_list[index] >= nslots) {
+                               int count = 0;
+
+                               for (i = index; i < (int)(index + nslots); i++)
+                                       io_tlb_list[i] = 0;
+                               for (i = index - 1;
+                                    (OFFSET(i, IO_TLB_SEGSIZE) !=
+                                     IO_TLB_SEGSIZE -1) && io_tlb_list[i];
+                                    i--)
+                                       io_tlb_list[i] = ++count;
+                               dma_addr = iotlb_virt_start +
+                                       (index << IO_TLB_SHIFT);
+
+                               /*
+                                * Update the indices to avoid searching in
+                                * the next round.
+                                */
+                               io_tlb_index = 
+                                       ((index + nslots) < iotlb_nslabs
+                                        ? (index + nslots) : 0);
+
+                               goto found;
+                       }
+                       index += stride;
+                       if (index >= iotlb_nslabs)
+                               index = 0;
+               } while (index != wrap);
+
+               spin_unlock_irqrestore(&io_tlb_lock, flags);
+               return NULL;
+       }
+  found:
+       spin_unlock_irqrestore(&io_tlb_lock, flags);
+
+       /*
+        * Save away the mapping from the original address to the DMA address.
+        * This is needed when we sync the memory.  Then we sync the buffer if
+        * needed.
+        */
+       slot_buf = buffer;
+       for (i = 0; i < nslots; i++) {
+               slot_buf.page += slot_buf.offset >> PAGE_SHIFT;
+               slot_buf.offset &= PAGE_SIZE - 1;
+               io_tlb_orig_addr[index+i] = slot_buf;
+               slot_buf.offset += 1 << IO_TLB_SHIFT;
+       }
+       if ((dir == DMA_TO_DEVICE) || (dir == DMA_BIDIRECTIONAL))
+               __sync_single(buffer, dma_addr, size, DMA_TO_DEVICE);
+
+       return dma_addr;
+}
+
+struct phys_addr dma_addr_to_phys_addr(char *dma_addr)
+{
+       int index = (dma_addr - iotlb_virt_start) >> IO_TLB_SHIFT;
+       struct phys_addr buffer = io_tlb_orig_addr[index];
+       buffer.offset += (long)dma_addr & ((1 << IO_TLB_SHIFT) - 1);
+       buffer.page += buffer.offset >> PAGE_SHIFT;
+       buffer.offset &= PAGE_SIZE - 1;
+       return buffer;
+}
+
+/*
+ * dma_addr is the kernel virtual address of the bounce buffer to unmap.
+ */
+static void
+unmap_single(struct device *hwdev, char *dma_addr, size_t size, int dir)
+{
+       unsigned long flags;
+       int i, count, nslots = ALIGN(size, 1 << IO_TLB_SHIFT) >> IO_TLB_SHIFT;
+       int index = (dma_addr - iotlb_virt_start) >> IO_TLB_SHIFT;
+       struct phys_addr buffer = dma_addr_to_phys_addr(dma_addr);
+
+       /*
+        * First, sync the memory before unmapping the entry
+        */
+       if ((dir == DMA_FROM_DEVICE) || (dir == DMA_BIDIRECTIONAL))
+               __sync_single(buffer, dma_addr, size, DMA_FROM_DEVICE);
+
+       /*
+        * Return the buffer to the free list by setting the corresponding
+        * entries to indicate the number of contigous entries available.
+        * While returning the entries to the free list, we merge the entries
+        * with slots below and above the pool being returned.
+        */
+       spin_lock_irqsave(&io_tlb_lock, flags);
+       {
+               count = ((index + nslots) < ALIGN(index + 1, IO_TLB_SEGSIZE) ?
+                        io_tlb_list[index + nslots] : 0);
+               /*
+                * Step 1: return the slots to the free list, merging the
+                * slots with superceeding slots
+                */
+               for (i = index + nslots - 1; i >= index; i--)
+                       io_tlb_list[i] = ++count;
+               /*
+                * Step 2: merge the returned slots with the preceding slots,
+                * if available (non zero)
+                */
+               for (i = index - 1;
+                    (OFFSET(i, IO_TLB_SEGSIZE) !=
+                     IO_TLB_SEGSIZE -1) && io_tlb_list[i];
+                    i--)
+                       io_tlb_list[i] = ++count;
+       }
+       spin_unlock_irqrestore(&io_tlb_lock, flags);
+}
+
+static void
+sync_single(struct device *hwdev, char *dma_addr, size_t size, int dir)
+{
+       struct phys_addr buffer = dma_addr_to_phys_addr(dma_addr);
+       BUG_ON((dir != DMA_FROM_DEVICE) && (dir != DMA_TO_DEVICE));
+       __sync_single(buffer, dma_addr, size, dir);
+}
+
+static void
+swiotlb_full(struct device *dev, size_t size, int dir, int do_panic)
+{
+       /*
+        * Ran out of IOMMU space for this operation. This is very bad.
+        * Unfortunately the drivers cannot handle this operation properly.
+        * unless they check for pci_dma_mapping_error (most don't)
+        * When the mapping is small enough return a static buffer to limit
+        * the damage, or panic when the transfer is too big.
+        */
+       printk(KERN_ERR "PCI-DMA: Out of SW-IOMMU space for %lu bytes at "
+              "device %s\n", (unsigned long)size, dev ? dev->bus_id : "?");
+
+       if (size > io_tlb_overflow && do_panic) {
+               if (dir == PCI_DMA_FROMDEVICE || dir == PCI_DMA_BIDIRECTIONAL)
+                       panic("PCI-DMA: Memory would be corrupted\n");
+               if (dir == PCI_DMA_TODEVICE || dir == PCI_DMA_BIDIRECTIONAL)
+                       panic("PCI-DMA: Random memory would be DMAed\n");
+       }
+}
+
+/*
+ * Map a single buffer of the indicated size for DMA in streaming mode.  The
+ * PCI address to use is returned.
+ *
+ * Once the device is given the dma address, the device owns this memory until
+ * either swiotlb_unmap_single or swiotlb_dma_sync_single is performed.
+ */
+dma_addr_t
+swiotlb_map_single(struct device *hwdev, void *ptr, size_t size, int dir)
+{
+       dma_addr_t dev_addr = gnttab_dma_map_page(virt_to_page(ptr)) +
+                             offset_in_page(ptr);
+       void *map;
+       struct phys_addr buffer;
+
+       BUG_ON(dir == DMA_NONE);
+
+       /*
+        * If the pointer passed in happens to be in the device's DMA window,
+        * we can safely return the device addr and not worry about bounce
+        * buffering it.
+        */
+       if (!range_straddles_page_boundary(__pa(ptr), size) &&
+           !address_needs_mapping(hwdev, dev_addr))
+               return dev_addr;
+
+       /*
+        * Oh well, have to allocate and map a bounce buffer.
+        */
+       gnttab_dma_unmap_page(dev_addr);
+       buffer.page   = virt_to_page(ptr);
+       buffer.offset = (unsigned long)ptr & ~PAGE_MASK;
+       map = map_single(hwdev, buffer, size, dir);
+       if (!map) {
+               swiotlb_full(hwdev, size, dir, 1);
+               map = io_tlb_overflow_buffer;
+       }
+
+       dev_addr = virt_to_bus(map);
+       return dev_addr;
+}
+
+/*
+ * Unmap a single streaming mode DMA translation.  The dma_addr and size must
+ * match what was provided for in a previous swiotlb_map_single 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.
+ */
+void
+swiotlb_unmap_single(struct device *hwdev, dma_addr_t dev_addr, size_t size,
+                    int dir)
+{
+       BUG_ON(dir == DMA_NONE);
+       if (in_swiotlb_aperture(dev_addr))
+               unmap_single(hwdev, bus_to_virt(dev_addr), size, dir);
+       else
+               gnttab_dma_unmap_page(dev_addr);
+}
+
+/*
+ * Make physical memory consistent for a single streaming mode DMA translation
+ * after a transfer.
+ *
+ * If you perform a swiotlb_map_single() but wish to interrogate the buffer
+ * using the cpu, yet do not wish to teardown the PCI dma mapping, you must
+ * call this function before doing so.  At the next point you give the PCI dma
+ * address back to the card, you must first perform a
+ * swiotlb_dma_sync_for_device, and then the device again owns the buffer
+ */
+void
+swiotlb_sync_single_for_cpu(struct device *hwdev, dma_addr_t dev_addr,
+                           size_t size, int dir)
+{
+       BUG_ON(dir == DMA_NONE);
+       if (in_swiotlb_aperture(dev_addr))
+               sync_single(hwdev, bus_to_virt(dev_addr), size, dir);
+}
+
+void
+swiotlb_sync_single_for_device(struct device *hwdev, dma_addr_t dev_addr,
+                              size_t size, int dir)
+{
+       BUG_ON(dir == DMA_NONE);
+       if (in_swiotlb_aperture(dev_addr))
+               sync_single(hwdev, bus_to_virt(dev_addr), size, dir);
+}
+
+/*
+ * Map a set of buffers described by scatterlist in streaming mode for DMA.
+ * This is the scatter-gather version of the above swiotlb_map_single
+ * interface.  Here the scatter gather list elements are each tagged with the
+ * appropriate dma address and length.  They are obtained via
+ * sg_dma_{address,length}(SG).
+ *
+ * NOTE: An implementation may be able to use a smaller number of
+ *       DMA address/length pairs than there are SG table elements.
+ *       (for example via virtual mapping capabilities)
+ *       The routine returns the number of addr/length pairs actually
+ *       used, at most nents.
+ *
+ * Device ownership issues as mentioned above for swiotlb_map_single are the
+ * same here.
+ */
+int
+swiotlb_map_sg(struct device *hwdev, struct scatterlist *sg, int nelems,
+              int dir)
+{
+       struct phys_addr buffer;
+       dma_addr_t dev_addr;
+       char *map;
+       int i;
+
+       BUG_ON(dir == DMA_NONE);
+
+       for (i = 0; i < nelems; i++, sg++) {
+               dev_addr = gnttab_dma_map_page(sg->page) + sg->offset;
+
+               if (range_straddles_page_boundary(page_to_pseudophys(sg->page)
+                                                 + sg->offset, sg->length)
+                   || address_needs_mapping(hwdev, dev_addr)) {
+                       gnttab_dma_unmap_page(dev_addr);
+                       buffer.page   = sg->page;
+                       buffer.offset = sg->offset;
+                       map = map_single(hwdev, buffer, sg->length, dir);
+                       if (!map) {
+                               /* Don't panic here, we expect map_sg users
+                                  to do proper error handling. */
+                               swiotlb_full(hwdev, sg->length, dir, 0);
+                               swiotlb_unmap_sg(hwdev, sg - i, i, dir);
+                               sg[0].dma_length = 0;
+                               return 0;
+                       }
+                       sg->dma_address = (dma_addr_t)virt_to_bus(map);
+               } else
+                       sg->dma_address = dev_addr;
+               sg->dma_length = sg->length;
+       }
+       return nelems;
+}
+
+/*
+ * Unmap a set of streaming mode DMA translations.  Again, cpu read rules
+ * concerning calls here are the same as for swiotlb_unmap_single() above.
+ */
+void
+swiotlb_unmap_sg(struct device *hwdev, struct scatterlist *sg, int nelems,
+                int dir)
+{
+       int i;
+
+       BUG_ON(dir == DMA_NONE);
+
+       for (i = 0; i < nelems; i++, sg++)
+               if (in_swiotlb_aperture(sg->dma_address))
+                       unmap_single(hwdev, 
+                                    (void *)bus_to_virt(sg->dma_address),
+                                    sg->dma_length, dir);
+               else
+                       gnttab_dma_unmap_page(sg->dma_address);
+}
+
+/*
+ * Make physical memory consistent for a set of streaming mode DMA translations
+ * after a transfer.
+ *
+ * The same as swiotlb_sync_single_* but for a scatter-gather list, same rules
+ * and usage.
+ */
+void
+swiotlb_sync_sg_for_cpu(struct device *hwdev, struct scatterlist *sg,
+                       int nelems, int dir)
+{
+       int i;
+
+       BUG_ON(dir == DMA_NONE);
+
+       for (i = 0; i < nelems; i++, sg++)
+               if (in_swiotlb_aperture(sg->dma_address))
+                       sync_single(hwdev,
+                                   (void *)bus_to_virt(sg->dma_address),
+                                   sg->dma_length, dir);
+}
+
+void
+swiotlb_sync_sg_for_device(struct device *hwdev, struct scatterlist *sg,
+                          int nelems, int dir)
+{
+       int i;
+
+       BUG_ON(dir == DMA_NONE);
+
+       for (i = 0; i < nelems; i++, sg++)
+               if (in_swiotlb_aperture(sg->dma_address))
+                       sync_single(hwdev,
+                                   (void *)bus_to_virt(sg->dma_address),
+                                   sg->dma_length, dir);
+}
+
+#ifdef CONFIG_HIGHMEM
+
+dma_addr_t
+swiotlb_map_page(struct device *hwdev, struct page *page,
+                unsigned long offset, size_t size,
+                enum dma_data_direction direction)
+{
+       struct phys_addr buffer;
+       dma_addr_t dev_addr;
+       char *map;
+
+       dev_addr = gnttab_dma_map_page(page) + offset;
+       if (address_needs_mapping(hwdev, dev_addr)) {
+               gnttab_dma_unmap_page(dev_addr);
+               buffer.page   = page;
+               buffer.offset = offset;
+               map = map_single(hwdev, buffer, size, direction);
+               if (!map) {
+                       swiotlb_full(hwdev, size, direction, 1);
+                       map = io_tlb_overflow_buffer;
+               }
+               dev_addr = (dma_addr_t)virt_to_bus(map);
+       }
+
+       return dev_addr;
+}
+
+void
+swiotlb_unmap_page(struct device *hwdev, dma_addr_t dma_address,
+                  size_t size, enum dma_data_direction direction)
+{
+       BUG_ON(direction == DMA_NONE);
+       if (in_swiotlb_aperture(dma_address))
+               unmap_single(hwdev, bus_to_virt(dma_address), size, direction);
+       else
+               gnttab_dma_unmap_page(dma_address);
+}
+
+#endif
+
+int
+swiotlb_dma_mapping_error(dma_addr_t dma_addr)
+{
+       return (dma_addr == virt_to_bus(io_tlb_overflow_buffer));
+}
+
+/*
+ * Return whether the given PCI device DMA address mask can be supported
+ * properly.  For example, if your device can only drive the low 24-bits
+ * during PCI bus mastering, then you would pass 0x00ffffff as the mask to
+ * this function.
+ */
+int
+swiotlb_dma_supported (struct device *hwdev, u64 mask)
+{
+       return (mask >= ((1UL << dma_bits) - 1));
+}
+
+EXPORT_SYMBOL(swiotlb_init);
+EXPORT_SYMBOL(swiotlb_map_single);
+EXPORT_SYMBOL(swiotlb_unmap_single);
+EXPORT_SYMBOL(swiotlb_map_sg);
+EXPORT_SYMBOL(swiotlb_unmap_sg);
+EXPORT_SYMBOL(swiotlb_sync_single_for_cpu);
+EXPORT_SYMBOL(swiotlb_sync_single_for_device);
+EXPORT_SYMBOL(swiotlb_sync_sg_for_cpu);
+EXPORT_SYMBOL(swiotlb_sync_sg_for_device);
+EXPORT_SYMBOL(swiotlb_dma_mapping_error);
+EXPORT_SYMBOL(swiotlb_dma_supported);



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