1 /*
2  * SPDX-License-Identifier: MIT
3  *
4  * Copyright © 2016 Intel Corporation
5  */
6 
7 #ifndef I915_SCATTERLIST_H
8 #define I915_SCATTERLIST_H
9 
10 #include <linux/pfn.h>
11 #include <linux/scatterlist.h>
12 #include <linux/dma-mapping.h>
13 #include <xen/xen.h>
14 
15 #include "i915_gem.h"
16 
17 struct drm_mm_node;
18 struct ttm_resource;
19 
20 /*
21  * Optimised SGL iterator for GEM objects
22  */
23 static __always_inline struct sgt_iter {
24 	struct scatterlist *sgp;
25 	union {
26 		unsigned long pfn;
27 		dma_addr_t dma;
28 	};
29 	unsigned int curr;
30 	unsigned int max;
31 } __sgt_iter(struct scatterlist *sgl, bool dma) {
32 	struct sgt_iter s = { .sgp = sgl };
33 
34 	if (dma && s.sgp && sg_dma_len(s.sgp) == 0) {
35 		s.sgp = NULL;
36 	} else if (s.sgp) {
37 		s.max = s.curr = s.sgp->offset;
38 		if (dma) {
39 			s.dma = sg_dma_address(s.sgp);
40 			s.max += sg_dma_len(s.sgp);
41 		} else {
42 			s.pfn = page_to_pfn(sg_page(s.sgp));
43 			s.max += s.sgp->length;
44 		}
45 	}
46 
47 	return s;
48 }
49 
50 static inline int __sg_page_count(const struct scatterlist *sg)
51 {
52 	return sg->length >> PAGE_SHIFT;
53 }
54 
55 static inline int __sg_dma_page_count(const struct scatterlist *sg)
56 {
57 	return sg_dma_len(sg) >> PAGE_SHIFT;
58 }
59 
60 static inline struct scatterlist *____sg_next(struct scatterlist *sg)
61 {
62 	++sg;
63 	if (unlikely(sg_is_chain(sg)))
64 		sg = sg_chain_ptr(sg);
65 	return sg;
66 }
67 
68 /**
69  * __sg_next - return the next scatterlist entry in a list
70  * @sg:		The current sg entry
71  *
72  * Description:
73  *   If the entry is the last, return NULL; otherwise, step to the next
74  *   element in the array (@sg@+1). If that's a chain pointer, follow it;
75  *   otherwise just return the pointer to the current element.
76  **/
77 static inline struct scatterlist *__sg_next(struct scatterlist *sg)
78 {
79 	return sg_is_last(sg) ? NULL : ____sg_next(sg);
80 }
81 
82 /**
83  * __for_each_sgt_daddr - iterate over the device addresses of the given sg_table
84  * @__dp:	Device address (output)
85  * @__iter:	'struct sgt_iter' (iterator state, internal)
86  * @__sgt:	sg_table to iterate over (input)
87  * @__step:	step size
88  */
89 #define __for_each_sgt_daddr(__dp, __iter, __sgt, __step)		\
90 	for ((__iter) = __sgt_iter((__sgt)->sgl, true);			\
91 	     ((__dp) = (__iter).dma + (__iter).curr), (__iter).sgp;	\
92 	     (((__iter).curr += (__step)) >= (__iter).max) ?		\
93 	     (__iter) = __sgt_iter(__sg_next((__iter).sgp), true), 0 : 0)
94 
95 /**
96  * for_each_sgt_page - iterate over the pages of the given sg_table
97  * @__pp:	page pointer (output)
98  * @__iter:	'struct sgt_iter' (iterator state, internal)
99  * @__sgt:	sg_table to iterate over (input)
100  */
101 #define for_each_sgt_page(__pp, __iter, __sgt)				\
102 	for ((__iter) = __sgt_iter((__sgt)->sgl, false);		\
103 	     ((__pp) = (__iter).pfn == 0 ? NULL :			\
104 	      pfn_to_page((__iter).pfn + ((__iter).curr >> PAGE_SHIFT))); \
105 	     (((__iter).curr += PAGE_SIZE) >= (__iter).max) ?		\
106 	     (__iter) = __sgt_iter(__sg_next((__iter).sgp), false), 0 : 0)
107 
108 /**
109  * i915_sg_dma_sizes - Record the dma segment sizes of a scatterlist
110  * @sg: The scatterlist
111  *
112  * Return: An unsigned int with segment sizes logically or'ed together.
113  * A caller can use this information to determine what hardware page table
114  * entry sizes can be used to map the memory represented by the scatterlist.
115  */
116 static inline unsigned int i915_sg_dma_sizes(struct scatterlist *sg)
117 {
118 	unsigned int page_sizes;
119 
120 	page_sizes = 0;
121 	while (sg && sg_dma_len(sg)) {
122 		GEM_BUG_ON(sg->offset);
123 		GEM_BUG_ON(!IS_ALIGNED(sg_dma_len(sg), PAGE_SIZE));
124 		page_sizes |= sg_dma_len(sg);
125 		sg = __sg_next(sg);
126 	}
127 
128 	return page_sizes;
129 }
130 
131 static inline unsigned int i915_sg_segment_size(struct device *dev)
132 {
133 	size_t max = min_t(size_t, UINT_MAX, dma_max_mapping_size(dev));
134 
135 	/*
136 	 * For Xen PV guests pages aren't contiguous in DMA (machine) address
137 	 * space.  The DMA API takes care of that both in dma_alloc_* (by
138 	 * calling into the hypervisor to make the pages contiguous) and in
139 	 * dma_map_* (by bounce buffering).  But i915 abuses ignores the
140 	 * coherency aspects of the DMA API and thus can't cope with bounce
141 	 * buffering actually happening, so add a hack here to force small
142 	 * allocations and mappings when running in PV mode on Xen.
143 	 *
144 	 * Note this will still break if bounce buffering is required for other
145 	 * reasons, like confidential computing hypervisors or PCIe root ports
146 	 * with addressing limitations.
147 	 */
148 	if (xen_pv_domain())
149 		max = PAGE_SIZE;
150 	return round_down(max, PAGE_SIZE);
151 }
152 
153 bool i915_sg_trim(struct sg_table *orig_st);
154 
155 /**
156  * struct i915_refct_sgt_ops - Operations structure for struct i915_refct_sgt
157  */
158 struct i915_refct_sgt_ops {
159 	/**
160 	 * release() - Free the memory of the struct i915_refct_sgt
161 	 * @ref: struct kref that is embedded in the struct i915_refct_sgt
162 	 */
163 	void (*release)(struct kref *ref);
164 };
165 
166 /**
167  * struct i915_refct_sgt - A refcounted scatter-gather table
168  * @kref: struct kref for refcounting
169  * @table: struct sg_table holding the scatter-gather table itself. Note that
170  * @table->sgl = NULL can be used to determine whether a scatter-gather table
171  * is present or not.
172  * @size: The size in bytes of the underlying memory buffer
173  * @ops: The operations structure.
174  */
175 struct i915_refct_sgt {
176 	struct kref kref;
177 	struct sg_table table;
178 	size_t size;
179 	const struct i915_refct_sgt_ops *ops;
180 };
181 
182 /**
183  * i915_refct_sgt_put - Put a refcounted sg-table
184  * @rsgt the struct i915_refct_sgt to put.
185  */
186 static inline void i915_refct_sgt_put(struct i915_refct_sgt *rsgt)
187 {
188 	if (rsgt)
189 		kref_put(&rsgt->kref, rsgt->ops->release);
190 }
191 
192 /**
193  * i915_refct_sgt_get - Get a refcounted sg-table
194  * @rsgt the struct i915_refct_sgt to get.
195  */
196 static inline struct i915_refct_sgt *
197 i915_refct_sgt_get(struct i915_refct_sgt *rsgt)
198 {
199 	kref_get(&rsgt->kref);
200 	return rsgt;
201 }
202 
203 /**
204  * __i915_refct_sgt_init - Initialize a refcounted sg-list with a custom
205  * operations structure
206  * @rsgt The struct i915_refct_sgt to initialize.
207  * @size: Size in bytes of the underlying memory buffer.
208  * @ops: A customized operations structure in case the refcounted sg-list
209  * is embedded into another structure.
210  */
211 static inline void __i915_refct_sgt_init(struct i915_refct_sgt *rsgt,
212 					 size_t size,
213 					 const struct i915_refct_sgt_ops *ops)
214 {
215 	kref_init(&rsgt->kref);
216 	rsgt->table.sgl = NULL;
217 	rsgt->size = size;
218 	rsgt->ops = ops;
219 }
220 
221 void i915_refct_sgt_init(struct i915_refct_sgt *rsgt, size_t size);
222 
223 struct i915_refct_sgt *i915_rsgt_from_mm_node(const struct drm_mm_node *node,
224 					      u64 region_start,
225 					      u32 page_alignment);
226 
227 struct i915_refct_sgt *i915_rsgt_from_buddy_resource(struct ttm_resource *res,
228 						     u64 region_start,
229 						     u32 page_alignment);
230 
231 #endif
232