1 // SPDX-License-Identifier: GPL-2.0 OR MIT
2 
3 /*
4  *  Xen para-virtual DRM device
5  *
6  * Copyright (C) 2016-2018 EPAM Systems Inc.
7  *
8  * Author: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
9  */
10 
11 #include <linux/dma-buf.h>
12 #include <linux/scatterlist.h>
13 #include <linux/shmem_fs.h>
14 
15 #include <drm/drm_fb_helper.h>
16 #include <drm/drm_gem.h>
17 #include <drm/drm_prime.h>
18 #include <drm/drm_probe_helper.h>
19 
20 #include <xen/balloon.h>
21 #include <xen/xen.h>
22 
23 #include "xen_drm_front.h"
24 #include "xen_drm_front_gem.h"
25 
26 struct xen_gem_object {
27 	struct drm_gem_object base;
28 
29 	size_t num_pages;
30 	struct page **pages;
31 
32 	/* set for buffers allocated by the backend */
33 	bool be_alloc;
34 
35 	/* this is for imported PRIME buffer */
36 	struct sg_table *sgt_imported;
37 };
38 
39 static inline struct xen_gem_object *
40 to_xen_gem_obj(struct drm_gem_object *gem_obj)
41 {
42 	return container_of(gem_obj, struct xen_gem_object, base);
43 }
44 
45 static int gem_alloc_pages_array(struct xen_gem_object *xen_obj,
46 				 size_t buf_size)
47 {
48 	xen_obj->num_pages = DIV_ROUND_UP(buf_size, PAGE_SIZE);
49 	xen_obj->pages = kvmalloc_array(xen_obj->num_pages,
50 					sizeof(struct page *), GFP_KERNEL);
51 	return !xen_obj->pages ? -ENOMEM : 0;
52 }
53 
54 static void gem_free_pages_array(struct xen_gem_object *xen_obj)
55 {
56 	kvfree(xen_obj->pages);
57 	xen_obj->pages = NULL;
58 }
59 
60 static const struct vm_operations_struct xen_drm_drv_vm_ops = {
61 	.open           = drm_gem_vm_open,
62 	.close          = drm_gem_vm_close,
63 };
64 
65 static const struct drm_gem_object_funcs xen_drm_front_gem_object_funcs = {
66 	.free = xen_drm_front_gem_object_free,
67 	.get_sg_table = xen_drm_front_gem_get_sg_table,
68 	.vmap = xen_drm_front_gem_prime_vmap,
69 	.vunmap = xen_drm_front_gem_prime_vunmap,
70 	.vm_ops = &xen_drm_drv_vm_ops,
71 };
72 
73 static struct xen_gem_object *gem_create_obj(struct drm_device *dev,
74 					     size_t size)
75 {
76 	struct xen_gem_object *xen_obj;
77 	int ret;
78 
79 	xen_obj = kzalloc(sizeof(*xen_obj), GFP_KERNEL);
80 	if (!xen_obj)
81 		return ERR_PTR(-ENOMEM);
82 
83 	xen_obj->base.funcs = &xen_drm_front_gem_object_funcs;
84 
85 	ret = drm_gem_object_init(dev, &xen_obj->base, size);
86 	if (ret < 0) {
87 		kfree(xen_obj);
88 		return ERR_PTR(ret);
89 	}
90 
91 	return xen_obj;
92 }
93 
94 static struct xen_gem_object *gem_create(struct drm_device *dev, size_t size)
95 {
96 	struct xen_drm_front_drm_info *drm_info = dev->dev_private;
97 	struct xen_gem_object *xen_obj;
98 	int ret;
99 
100 	size = round_up(size, PAGE_SIZE);
101 	xen_obj = gem_create_obj(dev, size);
102 	if (IS_ERR(xen_obj))
103 		return xen_obj;
104 
105 	if (drm_info->front_info->cfg.be_alloc) {
106 		/*
107 		 * backend will allocate space for this buffer, so
108 		 * only allocate array of pointers to pages
109 		 */
110 		ret = gem_alloc_pages_array(xen_obj, size);
111 		if (ret < 0)
112 			goto fail;
113 
114 		/*
115 		 * allocate ballooned pages which will be used to map
116 		 * grant references provided by the backend
117 		 */
118 		ret = xen_alloc_unpopulated_pages(xen_obj->num_pages,
119 					          xen_obj->pages);
120 		if (ret < 0) {
121 			DRM_ERROR("Cannot allocate %zu ballooned pages: %d\n",
122 				  xen_obj->num_pages, ret);
123 			gem_free_pages_array(xen_obj);
124 			goto fail;
125 		}
126 
127 		xen_obj->be_alloc = true;
128 		return xen_obj;
129 	}
130 	/*
131 	 * need to allocate backing pages now, so we can share those
132 	 * with the backend
133 	 */
134 	xen_obj->num_pages = DIV_ROUND_UP(size, PAGE_SIZE);
135 	xen_obj->pages = drm_gem_get_pages(&xen_obj->base);
136 	if (IS_ERR(xen_obj->pages)) {
137 		ret = PTR_ERR(xen_obj->pages);
138 		xen_obj->pages = NULL;
139 		goto fail;
140 	}
141 
142 	return xen_obj;
143 
144 fail:
145 	DRM_ERROR("Failed to allocate buffer with size %zu\n", size);
146 	return ERR_PTR(ret);
147 }
148 
149 struct drm_gem_object *xen_drm_front_gem_create(struct drm_device *dev,
150 						size_t size)
151 {
152 	struct xen_gem_object *xen_obj;
153 
154 	xen_obj = gem_create(dev, size);
155 	if (IS_ERR(xen_obj))
156 		return ERR_CAST(xen_obj);
157 
158 	return &xen_obj->base;
159 }
160 
161 void xen_drm_front_gem_free_object_unlocked(struct drm_gem_object *gem_obj)
162 {
163 	struct xen_gem_object *xen_obj = to_xen_gem_obj(gem_obj);
164 
165 	if (xen_obj->base.import_attach) {
166 		drm_prime_gem_destroy(&xen_obj->base, xen_obj->sgt_imported);
167 		gem_free_pages_array(xen_obj);
168 	} else {
169 		if (xen_obj->pages) {
170 			if (xen_obj->be_alloc) {
171 				xen_free_unpopulated_pages(xen_obj->num_pages,
172 							   xen_obj->pages);
173 				gem_free_pages_array(xen_obj);
174 			} else {
175 				drm_gem_put_pages(&xen_obj->base,
176 						  xen_obj->pages, true, false);
177 			}
178 		}
179 	}
180 	drm_gem_object_release(gem_obj);
181 	kfree(xen_obj);
182 }
183 
184 struct page **xen_drm_front_gem_get_pages(struct drm_gem_object *gem_obj)
185 {
186 	struct xen_gem_object *xen_obj = to_xen_gem_obj(gem_obj);
187 
188 	return xen_obj->pages;
189 }
190 
191 struct sg_table *xen_drm_front_gem_get_sg_table(struct drm_gem_object *gem_obj)
192 {
193 	struct xen_gem_object *xen_obj = to_xen_gem_obj(gem_obj);
194 
195 	if (!xen_obj->pages)
196 		return ERR_PTR(-ENOMEM);
197 
198 	return drm_prime_pages_to_sg(gem_obj->dev,
199 				     xen_obj->pages, xen_obj->num_pages);
200 }
201 
202 struct drm_gem_object *
203 xen_drm_front_gem_import_sg_table(struct drm_device *dev,
204 				  struct dma_buf_attachment *attach,
205 				  struct sg_table *sgt)
206 {
207 	struct xen_drm_front_drm_info *drm_info = dev->dev_private;
208 	struct xen_gem_object *xen_obj;
209 	size_t size;
210 	int ret;
211 
212 	size = attach->dmabuf->size;
213 	xen_obj = gem_create_obj(dev, size);
214 	if (IS_ERR(xen_obj))
215 		return ERR_CAST(xen_obj);
216 
217 	ret = gem_alloc_pages_array(xen_obj, size);
218 	if (ret < 0)
219 		return ERR_PTR(ret);
220 
221 	xen_obj->sgt_imported = sgt;
222 
223 	ret = drm_prime_sg_to_page_addr_arrays(sgt, xen_obj->pages,
224 					       NULL, xen_obj->num_pages);
225 	if (ret < 0)
226 		return ERR_PTR(ret);
227 
228 	ret = xen_drm_front_dbuf_create(drm_info->front_info,
229 					xen_drm_front_dbuf_to_cookie(&xen_obj->base),
230 					0, 0, 0, size, sgt->sgl->offset,
231 					xen_obj->pages);
232 	if (ret < 0)
233 		return ERR_PTR(ret);
234 
235 	DRM_DEBUG("Imported buffer of size %zu with nents %u\n",
236 		  size, sgt->orig_nents);
237 
238 	return &xen_obj->base;
239 }
240 
241 static int gem_mmap_obj(struct xen_gem_object *xen_obj,
242 			struct vm_area_struct *vma)
243 {
244 	int ret;
245 
246 	/*
247 	 * clear the VM_PFNMAP flag that was set by drm_gem_mmap(), and set the
248 	 * vm_pgoff (used as a fake buffer offset by DRM) to 0 as we want to map
249 	 * the whole buffer.
250 	 */
251 	vma->vm_flags &= ~VM_PFNMAP;
252 	vma->vm_flags |= VM_MIXEDMAP;
253 	vma->vm_pgoff = 0;
254 	/*
255 	 * According to Xen on ARM ABI (xen/include/public/arch-arm.h):
256 	 * all memory which is shared with other entities in the system
257 	 * (including the hypervisor and other guests) must reside in memory
258 	 * which is mapped as Normal Inner Write-Back Outer Write-Back
259 	 * Inner-Shareable.
260 	 */
261 	vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);
262 
263 	/*
264 	 * vm_operations_struct.fault handler will be called if CPU access
265 	 * to VM is here. For GPUs this isn't the case, because CPU
266 	 * doesn't touch the memory. Insert pages now, so both CPU and GPU are
267 	 * happy.
268 	 * FIXME: as we insert all the pages now then no .fault handler must
269 	 * be called, so don't provide one
270 	 */
271 	ret = vm_map_pages(vma, xen_obj->pages, xen_obj->num_pages);
272 	if (ret < 0)
273 		DRM_ERROR("Failed to map pages into vma: %d\n", ret);
274 
275 	return ret;
276 }
277 
278 int xen_drm_front_gem_mmap(struct file *filp, struct vm_area_struct *vma)
279 {
280 	struct xen_gem_object *xen_obj;
281 	struct drm_gem_object *gem_obj;
282 	int ret;
283 
284 	ret = drm_gem_mmap(filp, vma);
285 	if (ret < 0)
286 		return ret;
287 
288 	gem_obj = vma->vm_private_data;
289 	xen_obj = to_xen_gem_obj(gem_obj);
290 	return gem_mmap_obj(xen_obj, vma);
291 }
292 
293 int xen_drm_front_gem_prime_vmap(struct drm_gem_object *gem_obj, struct dma_buf_map *map)
294 {
295 	struct xen_gem_object *xen_obj = to_xen_gem_obj(gem_obj);
296 	void *vaddr;
297 
298 	if (!xen_obj->pages)
299 		return -ENOMEM;
300 
301 	/* Please see comment in gem_mmap_obj on mapping and attributes. */
302 	vaddr = vmap(xen_obj->pages, xen_obj->num_pages,
303 		     VM_MAP, PAGE_KERNEL);
304 	if (!vaddr)
305 		return -ENOMEM;
306 	dma_buf_map_set_vaddr(map, vaddr);
307 
308 	return 0;
309 }
310 
311 void xen_drm_front_gem_prime_vunmap(struct drm_gem_object *gem_obj,
312 				    struct dma_buf_map *map)
313 {
314 	vunmap(map->vaddr);
315 }
316 
317 int xen_drm_front_gem_prime_mmap(struct drm_gem_object *gem_obj,
318 				 struct vm_area_struct *vma)
319 {
320 	struct xen_gem_object *xen_obj;
321 	int ret;
322 
323 	ret = drm_gem_mmap_obj(gem_obj, gem_obj->size, vma);
324 	if (ret < 0)
325 		return ret;
326 
327 	xen_obj = to_xen_gem_obj(gem_obj);
328 	return gem_mmap_obj(xen_obj, vma);
329 }
330