linux/arch/arm/xen/mm.c
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   1// SPDX-License-Identifier: GPL-2.0-only
   2#include <linux/cpu.h>
   3#include <linux/dma-direct.h>
   4#include <linux/dma-map-ops.h>
   5#include <linux/gfp.h>
   6#include <linux/highmem.h>
   7#include <linux/export.h>
   8#include <linux/memblock.h>
   9#include <linux/of_address.h>
  10#include <linux/slab.h>
  11#include <linux/types.h>
  12#include <linux/vmalloc.h>
  13#include <linux/swiotlb.h>
  14
  15#include <xen/xen.h>
  16#include <xen/interface/grant_table.h>
  17#include <xen/interface/memory.h>
  18#include <xen/page.h>
  19#include <xen/xen-ops.h>
  20#include <xen/swiotlb-xen.h>
  21
  22#include <asm/cacheflush.h>
  23#include <asm/xen/hypercall.h>
  24#include <asm/xen/interface.h>
  25
  26unsigned long xen_get_swiotlb_free_pages(unsigned int order)
  27{
  28        phys_addr_t base;
  29        gfp_t flags = __GFP_NOWARN|__GFP_KSWAPD_RECLAIM;
  30        u64 i;
  31
  32        for_each_mem_range(i, &base, NULL) {
  33                if (base < (phys_addr_t)0xffffffff) {
  34                        if (IS_ENABLED(CONFIG_ZONE_DMA32))
  35                                flags |= __GFP_DMA32;
  36                        else
  37                                flags |= __GFP_DMA;
  38                        break;
  39                }
  40        }
  41        return __get_free_pages(flags, order);
  42}
  43
  44static bool hypercall_cflush = false;
  45
  46/* buffers in highmem or foreign pages cannot cross page boundaries */
  47static void dma_cache_maint(struct device *dev, dma_addr_t handle,
  48                            size_t size, u32 op)
  49{
  50        struct gnttab_cache_flush cflush;
  51
  52        cflush.offset = xen_offset_in_page(handle);
  53        cflush.op = op;
  54        handle &= XEN_PAGE_MASK;
  55
  56        do {
  57                cflush.a.dev_bus_addr = dma_to_phys(dev, handle);
  58
  59                if (size + cflush.offset > XEN_PAGE_SIZE)
  60                        cflush.length = XEN_PAGE_SIZE - cflush.offset;
  61                else
  62                        cflush.length = size;
  63
  64                HYPERVISOR_grant_table_op(GNTTABOP_cache_flush, &cflush, 1);
  65
  66                cflush.offset = 0;
  67                handle += cflush.length;
  68                size -= cflush.length;
  69        } while (size);
  70}
  71
  72/*
  73 * Dom0 is mapped 1:1, and while the Linux page can span across multiple Xen
  74 * pages, it is not possible for it to contain a mix of local and foreign Xen
  75 * pages.  Calling pfn_valid on a foreign mfn will always return false, so if
  76 * pfn_valid returns true the pages is local and we can use the native
  77 * dma-direct functions, otherwise we call the Xen specific version.
  78 */
  79void xen_dma_sync_for_cpu(struct device *dev, dma_addr_t handle,
  80                          size_t size, enum dma_data_direction dir)
  81{
  82        if (dir != DMA_TO_DEVICE)
  83                dma_cache_maint(dev, handle, size, GNTTAB_CACHE_INVAL);
  84}
  85
  86void xen_dma_sync_for_device(struct device *dev, dma_addr_t handle,
  87                             size_t size, enum dma_data_direction dir)
  88{
  89        if (dir == DMA_FROM_DEVICE)
  90                dma_cache_maint(dev, handle, size, GNTTAB_CACHE_INVAL);
  91        else
  92                dma_cache_maint(dev, handle, size, GNTTAB_CACHE_CLEAN);
  93}
  94
  95bool xen_arch_need_swiotlb(struct device *dev,
  96                           phys_addr_t phys,
  97                           dma_addr_t dev_addr)
  98{
  99        unsigned int xen_pfn = XEN_PFN_DOWN(phys);
 100        unsigned int bfn = XEN_PFN_DOWN(dma_to_phys(dev, dev_addr));
 101
 102        /*
 103         * The swiotlb buffer should be used if
 104         *      - Xen doesn't have the cache flush hypercall
 105         *      - The Linux page refers to foreign memory
 106         *      - The device doesn't support coherent DMA request
 107         *
 108         * The Linux page may be spanned acrros multiple Xen page, although
 109         * it's not possible to have a mix of local and foreign Xen page.
 110         * Furthermore, range_straddles_page_boundary is already checking
 111         * if buffer is physically contiguous in the host RAM.
 112         *
 113         * Therefore we only need to check the first Xen page to know if we
 114         * require a bounce buffer because the device doesn't support coherent
 115         * memory and we are not able to flush the cache.
 116         */
 117        return (!hypercall_cflush && (xen_pfn != bfn) &&
 118                !dev_is_dma_coherent(dev));
 119}
 120
 121int xen_create_contiguous_region(phys_addr_t pstart, unsigned int order,
 122                                 unsigned int address_bits,
 123                                 dma_addr_t *dma_handle)
 124{
 125        if (!xen_initial_domain())
 126                return -EINVAL;
 127
 128        /* we assume that dom0 is mapped 1:1 for now */
 129        *dma_handle = pstart;
 130        return 0;
 131}
 132
 133void xen_destroy_contiguous_region(phys_addr_t pstart, unsigned int order)
 134{
 135        return;
 136}
 137
 138static int __init xen_mm_init(void)
 139{
 140        struct gnttab_cache_flush cflush;
 141        int rc;
 142
 143        if (!xen_swiotlb_detect())
 144                return 0;
 145
 146        rc = xen_swiotlb_init();
 147        /* we can work with the default swiotlb */
 148        if (rc < 0 && rc != -EEXIST)
 149                return rc;
 150
 151        cflush.op = 0;
 152        cflush.a.dev_bus_addr = 0;
 153        cflush.offset = 0;
 154        cflush.length = 0;
 155        if (HYPERVISOR_grant_table_op(GNTTABOP_cache_flush, &cflush, 1) != -ENOSYS)
 156                hypercall_cflush = true;
 157        return 0;
 158}
 159arch_initcall(xen_mm_init);
 160