arch/arm/xen/mm.c

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