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);
142
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