arch/arm/xen/mm.c

   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
  26 unsigned 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
  44 static bool hypercall_cflush = false;
  45
  46 /* buffers in highmem or foreign pages cannot cross page boundaries */
  47 static 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  */
  79 void 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
  86 void 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
  95 bool 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
 121 int 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
 133 void xen_destroy_contiguous_region(phys_addr_t pstart, unsigned int order)
 134 {
 135         return;
 136 }
 137
 138 static int __init xen_mm_init(void)
 139 {
 140         struct gnttab_cache_flush cflush;
 141         if (!xen_initial_domain())
 142                 return 0;
 143         xen_swiotlb_init(1, false);
 144
 145         cflush.op = 0;
 146         cflush.a.dev_bus_addr = 0;
 147         cflush.offset = 0;
 148         cflush.length = 0;
 149         if (HYPERVISOR_grant_table_op(GNTTABOP_cache_flush, &cflush, 1) != -ENOSYS)
 150                 hypercall_cflush = true;
 151         return 0;
 152 }
 153 arch_initcall(xen_mm_init);