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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-mapping.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                         flags |= __GFP_DMA;
 32                         break;
 33                 }
 34         }
 35         return __get_free_pages(flags, order);
 36 }
 37 
 38 enum dma_cache_op {
 39        DMA_UNMAP,
 40        DMA_MAP,
 41 };
 42 static bool hypercall_cflush = false;
 43 
 44 /* functions called by SWIOTLB */
 45 
 46 static void dma_cache_maint(dma_addr_t handle, unsigned long offset,
 47         size_t size, enum dma_data_direction dir, enum dma_cache_op op)
 48 {
 49         struct gnttab_cache_flush cflush;
 50         unsigned long xen_pfn;
 51         size_t left = size;
 52 
 53         xen_pfn = (handle >> XEN_PAGE_SHIFT) + offset / XEN_PAGE_SIZE;
 54         offset %= XEN_PAGE_SIZE;
 55 
 56         do {
 57                 size_t len = left;
 58         
 59                 /* buffers in highmem or foreign pages cannot cross page
 60                  * boundaries */
 61                 if (len + offset > XEN_PAGE_SIZE)
 62                         len = XEN_PAGE_SIZE - offset;
 63 
 64                 cflush.op = 0;
 65                 cflush.a.dev_bus_addr = xen_pfn << XEN_PAGE_SHIFT;
 66                 cflush.offset = offset;
 67                 cflush.length = len;
 68 
 69                 if (op == DMA_UNMAP && dir != DMA_TO_DEVICE)
 70                         cflush.op = GNTTAB_CACHE_INVAL;
 71                 if (op == DMA_MAP) {
 72                         if (dir == DMA_FROM_DEVICE)
 73                                 cflush.op = GNTTAB_CACHE_INVAL;
 74                         else
 75                                 cflush.op = GNTTAB_CACHE_CLEAN;
 76                 }
 77                 if (cflush.op)
 78                         HYPERVISOR_grant_table_op(GNTTABOP_cache_flush, &cflush, 1);
 79 
 80                 offset = 0;
 81                 xen_pfn++;
 82                 left -= len;
 83         } while (left);
 84 }
 85 
 86 static void __xen_dma_page_dev_to_cpu(struct device *hwdev, dma_addr_t handle,
 87                 size_t size, enum dma_data_direction dir)
 88 {
 89         dma_cache_maint(handle & PAGE_MASK, handle & ~PAGE_MASK, size, dir, DMA_UNMAP);
 90 }
 91 
 92 static void __xen_dma_page_cpu_to_dev(struct device *hwdev, dma_addr_t handle,
 93                 size_t size, enum dma_data_direction dir)
 94 {
 95         dma_cache_maint(handle & PAGE_MASK, handle & ~PAGE_MASK, size, dir, DMA_MAP);
 96 }
 97 
 98 void __xen_dma_map_page(struct device *hwdev, struct page *page,
 99              dma_addr_t dev_addr, unsigned long offset, size_t size,
100              enum dma_data_direction dir, unsigned long attrs)
101 {
102         if (is_device_dma_coherent(hwdev))
103                 return;
104         if (attrs & DMA_ATTR_SKIP_CPU_SYNC)
105                 return;
106 
107         __xen_dma_page_cpu_to_dev(hwdev, dev_addr, size, dir);
108 }
109 
110 void __xen_dma_unmap_page(struct device *hwdev, dma_addr_t handle,
111                 size_t size, enum dma_data_direction dir,
112                 unsigned long attrs)
113 
114 {
115         if (is_device_dma_coherent(hwdev))
116                 return;
117         if (attrs & DMA_ATTR_SKIP_CPU_SYNC)
118                 return;
119 
120         __xen_dma_page_dev_to_cpu(hwdev, handle, size, dir);
121 }
122 
123 void __xen_dma_sync_single_for_cpu(struct device *hwdev,
124                 dma_addr_t handle, size_t size, enum dma_data_direction dir)
125 {
126         if (is_device_dma_coherent(hwdev))
127                 return;
128         __xen_dma_page_dev_to_cpu(hwdev, handle, size, dir);
129 }
130 
131 void __xen_dma_sync_single_for_device(struct device *hwdev,
132                 dma_addr_t handle, size_t size, enum dma_data_direction dir)
133 {
134         if (is_device_dma_coherent(hwdev))
135                 return;
136         __xen_dma_page_cpu_to_dev(hwdev, handle, size, dir);
137 }
138 
139 bool xen_arch_need_swiotlb(struct device *dev,
140                            phys_addr_t phys,
141                            dma_addr_t dev_addr)
142 {
143         unsigned int xen_pfn = XEN_PFN_DOWN(phys);
144         unsigned int bfn = XEN_PFN_DOWN(dev_addr);
145 
146         /*
147          * The swiotlb buffer should be used if
148          *      - Xen doesn't have the cache flush hypercall
149          *      - The Linux page refers to foreign memory
150          *      - The device doesn't support coherent DMA request
151          *
152          * The Linux page may be spanned acrros multiple Xen page, although
153          * it's not possible to have a mix of local and foreign Xen page.
154          * Furthermore, range_straddles_page_boundary is already checking
155          * if buffer is physically contiguous in the host RAM.
156          *
157          * Therefore we only need to check the first Xen page to know if we
158          * require a bounce buffer because the device doesn't support coherent
159          * memory and we are not able to flush the cache.
160          */
161         return (!hypercall_cflush && (xen_pfn != bfn) &&
162                 !is_device_dma_coherent(dev));
163 }
164 
165 int xen_create_contiguous_region(phys_addr_t pstart, unsigned int order,
166                                  unsigned int address_bits,
167                                  dma_addr_t *dma_handle)
168 {
169         if (!xen_initial_domain())
170                 return -EINVAL;
171 
172         /* we assume that dom0 is mapped 1:1 for now */
173         *dma_handle = pstart;
174         return 0;
175 }
176 EXPORT_SYMBOL_GPL(xen_create_contiguous_region);
177 
178 void xen_destroy_contiguous_region(phys_addr_t pstart, unsigned int order)
179 {
180         return;
181 }
182 EXPORT_SYMBOL_GPL(xen_destroy_contiguous_region);
183 
184 const struct dma_map_ops *xen_dma_ops;
185 EXPORT_SYMBOL(xen_dma_ops);
186 
187 int __init xen_mm_init(void)
188 {
189         struct gnttab_cache_flush cflush;
190         if (!xen_initial_domain())
191                 return 0;
192         xen_swiotlb_init(1, false);
193         xen_dma_ops = &xen_swiotlb_dma_ops;
194 
195         cflush.op = 0;
196         cflush.a.dev_bus_addr = 0;
197         cflush.offset = 0;
198         cflush.length = 0;
199         if (HYPERVISOR_grant_table_op(GNTTABOP_cache_flush, &cflush, 1) != -ENOSYS)
200                 hypercall_cflush = true;
201         return 0;
202 }
203 arch_initcall(xen_mm_init);
204 

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