root/arch/arm/xen/mm.c

DEFINITIONS

1. xen_get_swiotlb_free_pages
2. dma_cache_maint
3. xen_dma_sync_for_cpu
4. xen_dma_sync_for_device
5. xen_arch_need_swiotlb
6. xen_create_contiguous_region
7. xen_destroy_contiguous_region
8. xen_mm_init

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