net/core/xdp.c

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