1 // SPDX-License-Identifier: GPL-2.0-only
3 * Xen grant DMA-mapping layer - contains special DMA-mapping routines
4 * for providing grant references as DMA addresses to be used by frontends
5 * (e.g. virtio) in Xen guests
7 * Copyright (c) 2021, Juergen Gross <jgross@suse.com>
10 #include <linux/module.h>
11 #include <linux/dma-map-ops.h>
13 #include <linux/pfn.h>
14 #include <linux/xarray.h>
16 #include <xen/xen-ops.h>
17 #include <xen/grant_table.h>
19 struct xen_grant_dma_data {
20 /* The ID of backend domain */
21 domid_t backend_domid;
22 /* Is device behaving sane? */
26 static DEFINE_XARRAY(xen_grant_dma_devices);
28 #define XEN_GRANT_DMA_ADDR_OFF (1ULL << 63)
30 static inline dma_addr_t grant_to_dma(grant_ref_t grant)
32 return XEN_GRANT_DMA_ADDR_OFF | ((dma_addr_t)grant << PAGE_SHIFT);
35 static inline grant_ref_t dma_to_grant(dma_addr_t dma)
37 return (grant_ref_t)((dma & ~XEN_GRANT_DMA_ADDR_OFF) >> PAGE_SHIFT);
40 static struct xen_grant_dma_data *find_xen_grant_dma_data(struct device *dev)
42 struct xen_grant_dma_data *data;
44 xa_lock(&xen_grant_dma_devices);
45 data = xa_load(&xen_grant_dma_devices, (unsigned long)dev);
46 xa_unlock(&xen_grant_dma_devices);
52 * DMA ops for Xen frontends (e.g. virtio).
54 * Used to act as a kind of software IOMMU for Xen guests by using grants as
56 * Such a DMA address is formed by using the grant reference as a frame
57 * number and setting the highest address bit (this bit is for the backend
58 * to be able to distinguish it from e.g. a mmio address).
60 static void *xen_grant_dma_alloc(struct device *dev, size_t size,
61 dma_addr_t *dma_handle, gfp_t gfp,
64 struct xen_grant_dma_data *data;
65 unsigned int i, n_pages = PFN_UP(size);
70 data = find_xen_grant_dma_data(dev);
74 if (unlikely(data->broken))
77 ret = alloc_pages_exact(n_pages * PAGE_SIZE, gfp);
81 pfn = virt_to_pfn(ret);
83 if (gnttab_alloc_grant_reference_seq(n_pages, &grant)) {
84 free_pages_exact(ret, n_pages * PAGE_SIZE);
88 for (i = 0; i < n_pages; i++) {
89 gnttab_grant_foreign_access_ref(grant + i, data->backend_domid,
90 pfn_to_gfn(pfn + i), 0);
93 *dma_handle = grant_to_dma(grant);
98 static void xen_grant_dma_free(struct device *dev, size_t size, void *vaddr,
99 dma_addr_t dma_handle, unsigned long attrs)
101 struct xen_grant_dma_data *data;
102 unsigned int i, n_pages = PFN_UP(size);
105 data = find_xen_grant_dma_data(dev);
109 if (unlikely(data->broken))
112 grant = dma_to_grant(dma_handle);
114 for (i = 0; i < n_pages; i++) {
115 if (unlikely(!gnttab_end_foreign_access_ref(grant + i))) {
116 dev_alert(dev, "Grant still in use by backend domain, disabled for further use\n");
122 gnttab_free_grant_reference_seq(grant, n_pages);
124 free_pages_exact(vaddr, n_pages * PAGE_SIZE);
127 static struct page *xen_grant_dma_alloc_pages(struct device *dev, size_t size,
128 dma_addr_t *dma_handle,
129 enum dma_data_direction dir,
134 vaddr = xen_grant_dma_alloc(dev, size, dma_handle, gfp, 0);
138 return virt_to_page(vaddr);
141 static void xen_grant_dma_free_pages(struct device *dev, size_t size,
142 struct page *vaddr, dma_addr_t dma_handle,
143 enum dma_data_direction dir)
145 xen_grant_dma_free(dev, size, page_to_virt(vaddr), dma_handle, 0);
148 static dma_addr_t xen_grant_dma_map_page(struct device *dev, struct page *page,
149 unsigned long offset, size_t size,
150 enum dma_data_direction dir,
153 struct xen_grant_dma_data *data;
154 unsigned int i, n_pages = PFN_UP(size);
156 dma_addr_t dma_handle;
158 if (WARN_ON(dir == DMA_NONE))
159 return DMA_MAPPING_ERROR;
161 data = find_xen_grant_dma_data(dev);
163 return DMA_MAPPING_ERROR;
165 if (unlikely(data->broken))
166 return DMA_MAPPING_ERROR;
168 if (gnttab_alloc_grant_reference_seq(n_pages, &grant))
169 return DMA_MAPPING_ERROR;
171 for (i = 0; i < n_pages; i++) {
172 gnttab_grant_foreign_access_ref(grant + i, data->backend_domid,
173 xen_page_to_gfn(page) + i, dir == DMA_TO_DEVICE);
176 dma_handle = grant_to_dma(grant) + offset;
181 static void xen_grant_dma_unmap_page(struct device *dev, dma_addr_t dma_handle,
182 size_t size, enum dma_data_direction dir,
185 struct xen_grant_dma_data *data;
186 unsigned int i, n_pages = PFN_UP(size);
189 if (WARN_ON(dir == DMA_NONE))
192 data = find_xen_grant_dma_data(dev);
196 if (unlikely(data->broken))
199 grant = dma_to_grant(dma_handle);
201 for (i = 0; i < n_pages; i++) {
202 if (unlikely(!gnttab_end_foreign_access_ref(grant + i))) {
203 dev_alert(dev, "Grant still in use by backend domain, disabled for further use\n");
209 gnttab_free_grant_reference_seq(grant, n_pages);
212 static void xen_grant_dma_unmap_sg(struct device *dev, struct scatterlist *sg,
213 int nents, enum dma_data_direction dir,
216 struct scatterlist *s;
219 if (WARN_ON(dir == DMA_NONE))
222 for_each_sg(sg, s, nents, i)
223 xen_grant_dma_unmap_page(dev, s->dma_address, sg_dma_len(s), dir,
227 static int xen_grant_dma_map_sg(struct device *dev, struct scatterlist *sg,
228 int nents, enum dma_data_direction dir,
231 struct scatterlist *s;
234 if (WARN_ON(dir == DMA_NONE))
237 for_each_sg(sg, s, nents, i) {
238 s->dma_address = xen_grant_dma_map_page(dev, sg_page(s), s->offset,
239 s->length, dir, attrs);
240 if (s->dma_address == DMA_MAPPING_ERROR)
243 sg_dma_len(s) = s->length;
249 xen_grant_dma_unmap_sg(dev, sg, i, dir, attrs | DMA_ATTR_SKIP_CPU_SYNC);
255 static int xen_grant_dma_supported(struct device *dev, u64 mask)
257 return mask == DMA_BIT_MASK(64);
260 static const struct dma_map_ops xen_grant_dma_ops = {
261 .alloc = xen_grant_dma_alloc,
262 .free = xen_grant_dma_free,
263 .alloc_pages = xen_grant_dma_alloc_pages,
264 .free_pages = xen_grant_dma_free_pages,
265 .mmap = dma_common_mmap,
266 .get_sgtable = dma_common_get_sgtable,
267 .map_page = xen_grant_dma_map_page,
268 .unmap_page = xen_grant_dma_unmap_page,
269 .map_sg = xen_grant_dma_map_sg,
270 .unmap_sg = xen_grant_dma_unmap_sg,
271 .dma_supported = xen_grant_dma_supported,
274 bool xen_is_grant_dma_device(struct device *dev)
276 struct device_node *iommu_np;
279 /* XXX Handle only DT devices for now */
283 iommu_np = of_parse_phandle(dev->of_node, "iommus", 0);
284 has_iommu = iommu_np && of_device_is_compatible(iommu_np, "xen,grant-dma");
285 of_node_put(iommu_np);
290 void xen_grant_setup_dma_ops(struct device *dev)
292 struct xen_grant_dma_data *data;
293 struct of_phandle_args iommu_spec;
295 data = find_xen_grant_dma_data(dev);
297 dev_err(dev, "Xen grant DMA data is already created\n");
301 /* XXX ACPI device unsupported for now */
305 if (of_parse_phandle_with_args(dev->of_node, "iommus", "#iommu-cells",
307 dev_err(dev, "Cannot parse iommus property\n");
311 if (!of_device_is_compatible(iommu_spec.np, "xen,grant-dma") ||
312 iommu_spec.args_count != 1) {
313 dev_err(dev, "Incompatible IOMMU node\n");
314 of_node_put(iommu_spec.np);
318 of_node_put(iommu_spec.np);
320 data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
325 * The endpoint ID here means the ID of the domain where the corresponding
328 data->backend_domid = iommu_spec.args[0];
330 if (xa_err(xa_store(&xen_grant_dma_devices, (unsigned long)dev, data,
332 dev_err(dev, "Cannot store Xen grant DMA data\n");
336 dev->dma_ops = &xen_grant_dma_ops;
341 dev_err(dev, "Cannot set up Xen grant DMA ops, retain platform DMA ops\n");
344 MODULE_DESCRIPTION("Xen grant DMA-mapping layer");
345 MODULE_AUTHOR("Juergen Gross <jgross@suse.com>");
346 MODULE_LICENSE("GPL");