xref: /openbmc/linux/net/core/xdp.c (revision da2ef666)
1 /* net/core/xdp.c
2  *
3  * Copyright (c) 2017 Jesper Dangaard Brouer, Red Hat Inc.
4  * Released under terms in GPL version 2.  See COPYING.
5  */
6 #include <linux/bpf.h>
7 #include <linux/filter.h>
8 #include <linux/types.h>
9 #include <linux/mm.h>
10 #include <linux/netdevice.h>
11 #include <linux/slab.h>
12 #include <linux/idr.h>
13 #include <linux/rhashtable.h>
14 #include <net/page_pool.h>
15 
16 #include <net/xdp.h>
17 
18 #define REG_STATE_NEW		0x0
19 #define REG_STATE_REGISTERED	0x1
20 #define REG_STATE_UNREGISTERED	0x2
21 #define REG_STATE_UNUSED	0x3
22 
23 static DEFINE_IDA(mem_id_pool);
24 static DEFINE_MUTEX(mem_id_lock);
25 #define MEM_ID_MAX 0xFFFE
26 #define MEM_ID_MIN 1
27 static int mem_id_next = MEM_ID_MIN;
28 
29 static bool mem_id_init; /* false */
30 static struct rhashtable *mem_id_ht;
31 
32 struct xdp_mem_allocator {
33 	struct xdp_mem_info mem;
34 	union {
35 		void *allocator;
36 		struct page_pool *page_pool;
37 		struct zero_copy_allocator *zc_alloc;
38 	};
39 	struct rhash_head node;
40 	struct rcu_head rcu;
41 };
42 
43 static u32 xdp_mem_id_hashfn(const void *data, u32 len, u32 seed)
44 {
45 	const u32 *k = data;
46 	const u32 key = *k;
47 
48 	BUILD_BUG_ON(FIELD_SIZEOF(struct xdp_mem_allocator, mem.id)
49 		     != sizeof(u32));
50 
51 	/* Use cyclic increasing ID as direct hash key */
52 	return key;
53 }
54 
55 static int xdp_mem_id_cmp(struct rhashtable_compare_arg *arg,
56 			  const void *ptr)
57 {
58 	const struct xdp_mem_allocator *xa = ptr;
59 	u32 mem_id = *(u32 *)arg->key;
60 
61 	return xa->mem.id != mem_id;
62 }
63 
64 static const struct rhashtable_params mem_id_rht_params = {
65 	.nelem_hint = 64,
66 	.head_offset = offsetof(struct xdp_mem_allocator, node),
67 	.key_offset  = offsetof(struct xdp_mem_allocator, mem.id),
68 	.key_len = FIELD_SIZEOF(struct xdp_mem_allocator, mem.id),
69 	.max_size = MEM_ID_MAX,
70 	.min_size = 8,
71 	.automatic_shrinking = true,
72 	.hashfn    = xdp_mem_id_hashfn,
73 	.obj_cmpfn = xdp_mem_id_cmp,
74 };
75 
76 static void __xdp_mem_allocator_rcu_free(struct rcu_head *rcu)
77 {
78 	struct xdp_mem_allocator *xa;
79 
80 	xa = container_of(rcu, struct xdp_mem_allocator, rcu);
81 
82 	/* Allow this ID to be reused */
83 	ida_simple_remove(&mem_id_pool, xa->mem.id);
84 
85 	/* Notice, driver is expected to free the *allocator,
86 	 * e.g. page_pool, and MUST also use RCU free.
87 	 */
88 
89 	/* Poison memory */
90 	xa->mem.id = 0xFFFF;
91 	xa->mem.type = 0xF0F0;
92 	xa->allocator = (void *)0xDEAD9001;
93 
94 	kfree(xa);
95 }
96 
97 static void __xdp_rxq_info_unreg_mem_model(struct xdp_rxq_info *xdp_rxq)
98 {
99 	struct xdp_mem_allocator *xa;
100 	int id = xdp_rxq->mem.id;
101 
102 	if (id == 0)
103 		return;
104 
105 	mutex_lock(&mem_id_lock);
106 
107 	xa = rhashtable_lookup_fast(mem_id_ht, &id, mem_id_rht_params);
108 	if (xa && !rhashtable_remove_fast(mem_id_ht, &xa->node, mem_id_rht_params))
109 		call_rcu(&xa->rcu, __xdp_mem_allocator_rcu_free);
110 
111 	mutex_unlock(&mem_id_lock);
112 }
113 
114 void xdp_rxq_info_unreg(struct xdp_rxq_info *xdp_rxq)
115 {
116 	/* Simplify driver cleanup code paths, allow unreg "unused" */
117 	if (xdp_rxq->reg_state == REG_STATE_UNUSED)
118 		return;
119 
120 	WARN(!(xdp_rxq->reg_state == REG_STATE_REGISTERED), "Driver BUG");
121 
122 	__xdp_rxq_info_unreg_mem_model(xdp_rxq);
123 
124 	xdp_rxq->reg_state = REG_STATE_UNREGISTERED;
125 	xdp_rxq->dev = NULL;
126 
127 	/* Reset mem info to defaults */
128 	xdp_rxq->mem.id = 0;
129 	xdp_rxq->mem.type = 0;
130 }
131 EXPORT_SYMBOL_GPL(xdp_rxq_info_unreg);
132 
133 static void xdp_rxq_info_init(struct xdp_rxq_info *xdp_rxq)
134 {
135 	memset(xdp_rxq, 0, sizeof(*xdp_rxq));
136 }
137 
138 /* Returns 0 on success, negative on failure */
139 int xdp_rxq_info_reg(struct xdp_rxq_info *xdp_rxq,
140 		     struct net_device *dev, u32 queue_index)
141 {
142 	if (xdp_rxq->reg_state == REG_STATE_UNUSED) {
143 		WARN(1, "Driver promised not to register this");
144 		return -EINVAL;
145 	}
146 
147 	if (xdp_rxq->reg_state == REG_STATE_REGISTERED) {
148 		WARN(1, "Missing unregister, handled but fix driver");
149 		xdp_rxq_info_unreg(xdp_rxq);
150 	}
151 
152 	if (!dev) {
153 		WARN(1, "Missing net_device from driver");
154 		return -ENODEV;
155 	}
156 
157 	/* State either UNREGISTERED or NEW */
158 	xdp_rxq_info_init(xdp_rxq);
159 	xdp_rxq->dev = dev;
160 	xdp_rxq->queue_index = queue_index;
161 
162 	xdp_rxq->reg_state = REG_STATE_REGISTERED;
163 	return 0;
164 }
165 EXPORT_SYMBOL_GPL(xdp_rxq_info_reg);
166 
167 void xdp_rxq_info_unused(struct xdp_rxq_info *xdp_rxq)
168 {
169 	xdp_rxq->reg_state = REG_STATE_UNUSED;
170 }
171 EXPORT_SYMBOL_GPL(xdp_rxq_info_unused);
172 
173 bool xdp_rxq_info_is_reg(struct xdp_rxq_info *xdp_rxq)
174 {
175 	return (xdp_rxq->reg_state == REG_STATE_REGISTERED);
176 }
177 EXPORT_SYMBOL_GPL(xdp_rxq_info_is_reg);
178 
179 static int __mem_id_init_hash_table(void)
180 {
181 	struct rhashtable *rht;
182 	int ret;
183 
184 	if (unlikely(mem_id_init))
185 		return 0;
186 
187 	rht = kzalloc(sizeof(*rht), GFP_KERNEL);
188 	if (!rht)
189 		return -ENOMEM;
190 
191 	ret = rhashtable_init(rht, &mem_id_rht_params);
192 	if (ret < 0) {
193 		kfree(rht);
194 		return ret;
195 	}
196 	mem_id_ht = rht;
197 	smp_mb(); /* mutex lock should provide enough pairing */
198 	mem_id_init = true;
199 
200 	return 0;
201 }
202 
203 /* Allocate a cyclic ID that maps to allocator pointer.
204  * See: https://www.kernel.org/doc/html/latest/core-api/idr.html
205  *
206  * Caller must lock mem_id_lock.
207  */
208 static int __mem_id_cyclic_get(gfp_t gfp)
209 {
210 	int retries = 1;
211 	int id;
212 
213 again:
214 	id = ida_simple_get(&mem_id_pool, mem_id_next, MEM_ID_MAX, gfp);
215 	if (id < 0) {
216 		if (id == -ENOSPC) {
217 			/* Cyclic allocator, reset next id */
218 			if (retries--) {
219 				mem_id_next = MEM_ID_MIN;
220 				goto again;
221 			}
222 		}
223 		return id; /* errno */
224 	}
225 	mem_id_next = id + 1;
226 
227 	return id;
228 }
229 
230 static bool __is_supported_mem_type(enum xdp_mem_type type)
231 {
232 	if (type == MEM_TYPE_PAGE_POOL)
233 		return is_page_pool_compiled_in();
234 
235 	if (type >= MEM_TYPE_MAX)
236 		return false;
237 
238 	return true;
239 }
240 
241 int xdp_rxq_info_reg_mem_model(struct xdp_rxq_info *xdp_rxq,
242 			       enum xdp_mem_type type, void *allocator)
243 {
244 	struct xdp_mem_allocator *xdp_alloc;
245 	gfp_t gfp = GFP_KERNEL;
246 	int id, errno, ret;
247 	void *ptr;
248 
249 	if (xdp_rxq->reg_state != REG_STATE_REGISTERED) {
250 		WARN(1, "Missing register, driver bug");
251 		return -EFAULT;
252 	}
253 
254 	if (!__is_supported_mem_type(type))
255 		return -EOPNOTSUPP;
256 
257 	xdp_rxq->mem.type = type;
258 
259 	if (!allocator) {
260 		if (type == MEM_TYPE_PAGE_POOL || type == MEM_TYPE_ZERO_COPY)
261 			return -EINVAL; /* Setup time check page_pool req */
262 		return 0;
263 	}
264 
265 	/* Delay init of rhashtable to save memory if feature isn't used */
266 	if (!mem_id_init) {
267 		mutex_lock(&mem_id_lock);
268 		ret = __mem_id_init_hash_table();
269 		mutex_unlock(&mem_id_lock);
270 		if (ret < 0) {
271 			WARN_ON(1);
272 			return ret;
273 		}
274 	}
275 
276 	xdp_alloc = kzalloc(sizeof(*xdp_alloc), gfp);
277 	if (!xdp_alloc)
278 		return -ENOMEM;
279 
280 	mutex_lock(&mem_id_lock);
281 	id = __mem_id_cyclic_get(gfp);
282 	if (id < 0) {
283 		errno = id;
284 		goto err;
285 	}
286 	xdp_rxq->mem.id = id;
287 	xdp_alloc->mem  = xdp_rxq->mem;
288 	xdp_alloc->allocator = allocator;
289 
290 	/* Insert allocator into ID lookup table */
291 	ptr = rhashtable_insert_slow(mem_id_ht, &id, &xdp_alloc->node);
292 	if (IS_ERR(ptr)) {
293 		errno = PTR_ERR(ptr);
294 		goto err;
295 	}
296 
297 	mutex_unlock(&mem_id_lock);
298 
299 	return 0;
300 err:
301 	mutex_unlock(&mem_id_lock);
302 	kfree(xdp_alloc);
303 	return errno;
304 }
305 EXPORT_SYMBOL_GPL(xdp_rxq_info_reg_mem_model);
306 
307 /* XDP RX runs under NAPI protection, and in different delivery error
308  * scenarios (e.g. queue full), it is possible to return the xdp_frame
309  * while still leveraging this protection.  The @napi_direct boolian
310  * is used for those calls sites.  Thus, allowing for faster recycling
311  * of xdp_frames/pages in those cases.
312  */
313 static void __xdp_return(void *data, struct xdp_mem_info *mem, bool napi_direct,
314 			 unsigned long handle)
315 {
316 	struct xdp_mem_allocator *xa;
317 	struct page *page;
318 
319 	switch (mem->type) {
320 	case MEM_TYPE_PAGE_POOL:
321 		rcu_read_lock();
322 		/* mem->id is valid, checked in xdp_rxq_info_reg_mem_model() */
323 		xa = rhashtable_lookup(mem_id_ht, &mem->id, mem_id_rht_params);
324 		page = virt_to_head_page(data);
325 		if (xa) {
326 			napi_direct &= !xdp_return_frame_no_direct();
327 			page_pool_put_page(xa->page_pool, page, napi_direct);
328 		} else {
329 			put_page(page);
330 		}
331 		rcu_read_unlock();
332 		break;
333 	case MEM_TYPE_PAGE_SHARED:
334 		page_frag_free(data);
335 		break;
336 	case MEM_TYPE_PAGE_ORDER0:
337 		page = virt_to_page(data); /* Assumes order0 page*/
338 		put_page(page);
339 		break;
340 	case MEM_TYPE_ZERO_COPY:
341 		/* NB! Only valid from an xdp_buff! */
342 		rcu_read_lock();
343 		/* mem->id is valid, checked in xdp_rxq_info_reg_mem_model() */
344 		xa = rhashtable_lookup(mem_id_ht, &mem->id, mem_id_rht_params);
345 		xa->zc_alloc->free(xa->zc_alloc, handle);
346 		rcu_read_unlock();
347 	default:
348 		/* Not possible, checked in xdp_rxq_info_reg_mem_model() */
349 		break;
350 	}
351 }
352 
353 void xdp_return_frame(struct xdp_frame *xdpf)
354 {
355 	__xdp_return(xdpf->data, &xdpf->mem, false, 0);
356 }
357 EXPORT_SYMBOL_GPL(xdp_return_frame);
358 
359 void xdp_return_frame_rx_napi(struct xdp_frame *xdpf)
360 {
361 	__xdp_return(xdpf->data, &xdpf->mem, true, 0);
362 }
363 EXPORT_SYMBOL_GPL(xdp_return_frame_rx_napi);
364 
365 void xdp_return_buff(struct xdp_buff *xdp)
366 {
367 	__xdp_return(xdp->data, &xdp->rxq->mem, true, xdp->handle);
368 }
369 EXPORT_SYMBOL_GPL(xdp_return_buff);
370 
371 int xdp_attachment_query(struct xdp_attachment_info *info,
372 			 struct netdev_bpf *bpf)
373 {
374 	bpf->prog_id = info->prog ? info->prog->aux->id : 0;
375 	bpf->prog_flags = info->prog ? info->flags : 0;
376 	return 0;
377 }
378 EXPORT_SYMBOL_GPL(xdp_attachment_query);
379 
380 bool xdp_attachment_flags_ok(struct xdp_attachment_info *info,
381 			     struct netdev_bpf *bpf)
382 {
383 	if (info->prog && (bpf->flags ^ info->flags) & XDP_FLAGS_MODES) {
384 		NL_SET_ERR_MSG(bpf->extack,
385 			       "program loaded with different flags");
386 		return false;
387 	}
388 	return true;
389 }
390 EXPORT_SYMBOL_GPL(xdp_attachment_flags_ok);
391 
392 void xdp_attachment_setup(struct xdp_attachment_info *info,
393 			  struct netdev_bpf *bpf)
394 {
395 	if (info->prog)
396 		bpf_prog_put(info->prog);
397 	info->prog = bpf->prog;
398 	info->flags = bpf->flags;
399 }
400 EXPORT_SYMBOL_GPL(xdp_attachment_setup);
401