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 static gfp_t xen_swiotlb_gfp(void)
  27 {
  28         phys_addr_t base;
  29         u64 i;
  30
  31         for_each_mem_range(i, &base, NULL) {
  32                 if (base < (phys_addr_t)0xffffffff) {
  33                         if (IS_ENABLED(CONFIG_ZONE_DMA32))
  34                                 return __GFP_DMA32;
  35                         return __GFP_DMA;
  36                 }
  37         }
  38
  39         return GFP_KERNEL;
  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(struct device *dev, dma_addr_t handle,
  46                             size_t size, u32 op)
  47 {
  48         struct gnttab_cache_flush cflush;
  49
  50         cflush.offset = xen_offset_in_page(handle);
  51         cflush.op = op;
  52         handle &= XEN_PAGE_MASK;
  53
  54         do {
  55                 cflush.a.dev_bus_addr = dma_to_phys(dev, handle);
  56
  57                 if (size + cflush.offset > XEN_PAGE_SIZE)
  58                         cflush.length = XEN_PAGE_SIZE - cflush.offset;
  59                 else
  60                         cflush.length = size;
  61
  62                 HYPERVISOR_grant_table_op(GNTTABOP_cache_flush, &cflush, 1);
  63
  64                 cflush.offset = 0;
  65                 handle += cflush.length;
  66                 size -= cflush.length;
  67         } while (size);
  68 }
  69
  70 /*
  71  * Dom0 is mapped 1:1, and while the Linux page can span across multiple Xen
  72  * pages, it is not possible for it to contain a mix of local and foreign Xen
  73  * pages.  Calling pfn_valid on a foreign mfn will always return false, so if
  74  * pfn_valid returns true the pages is local and we can use the native
  75  * dma-direct functions, otherwise we call the Xen specific version.
  76  */
  77 void xen_dma_sync_for_cpu(struct device *dev, dma_addr_t handle,
  78                           size_t size, enum dma_data_direction dir)
  79 {
  80         if (dir != DMA_TO_DEVICE)
  81                 dma_cache_maint(dev, handle, size, GNTTAB_CACHE_INVAL);
  82 }
  83
  84 void xen_dma_sync_for_device(struct device *dev, dma_addr_t handle,
  85                              size_t size, enum dma_data_direction dir)
  86 {
  87         if (dir == DMA_FROM_DEVICE)
  88                 dma_cache_maint(dev, handle, size, GNTTAB_CACHE_INVAL);
  89         else
  90                 dma_cache_maint(dev, 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(dma_to_phys(dev, 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 static int __init xen_mm_init(void)
 120 {
 121         struct gnttab_cache_flush cflush;
 122         int rc;
 123
 124         if (!xen_swiotlb_detect())
 125                 return 0;
 126
 127         /* we can work with the default swiotlb */
 128         rc = swiotlb_init_late(swiotlb_size_or_default(),
 129                                xen_swiotlb_gfp(), NULL);
 130         if (rc < 0)
 131                 return rc;
 132
 133         cflush.op = 0;
 134         cflush.a.dev_bus_addr = 0;
 135         cflush.offset = 0;
 136         cflush.length = 0;
 137         if (HYPERVISOR_grant_table_op(GNTTABOP_cache_flush, &cflush, 1) != -ENOSYS)
 138                 hypercall_cflush = true;
 139         return 0;
 140 }
 141 arch_initcall(xen_mm_init);