drivers/hv/ring_buffer.c

   1 /*
   2  *
   3  * Copyright (c) 2009, Microsoft Corporation.
   4  *
   5  * This program is free software; you can redistribute it and/or modify it
   6  * under the terms and conditions of the GNU General Public License,
   7  * version 2, as published by the Free Software Foundation.
   8  *
   9  * This program is distributed in the hope it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
  12  * more details.
  13  *
  14  * You should have received a copy of the GNU General Public License along with
  15  * this program; if not, write to the Free Software Foundation, Inc., 59 Temple
  16  * Place - Suite 330, Boston, MA 02111-1307 USA.
  17  *
  18  * Authors:
  19  *   Haiyang Zhang <haiyangz@microsoft.com>
  20  *   Hank Janssen  <hjanssen@microsoft.com>
  21  *   K. Y. Srinivasan <kys@microsoft.com>
  22  *
  23  */
  24 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  25
  26 #include <linux/kernel.h>
  27 #include <linux/mm.h>
  28 #include <linux/hyperv.h>
  29
  30 #include "hyperv_vmbus.h"
  31
  32
  33 /* #defines */
  34
  35
  36 /* Amount of space to write to */
  37 #define BYTES_AVAIL_TO_WRITE(r, w, z) \
  38         ((w) >= (r)) ? ((z) - ((w) - (r))) : ((r) - (w))
  39
  40
  41 /*
  42  *
  43  * hv_get_ringbuffer_availbytes()
  44  *
  45  * Get number of bytes available to read and to write to
  46  * for the specified ring buffer
  47  */
  48 static inline void
  49 hv_get_ringbuffer_availbytes(struct hv_ring_buffer_info *rbi,
  50                           u32 *read, u32 *write)
  51 {
  52         u32 read_loc, write_loc;
  53
  54         smp_read_barrier_depends();
  55
  56         /* Capture the read/write indices before they changed */
  57         read_loc = rbi->ring_buffer->read_index;
  58         write_loc = rbi->ring_buffer->write_index;
  59
  60         *write = BYTES_AVAIL_TO_WRITE(read_loc, write_loc, rbi->ring_datasize);
  61         *read = rbi->ring_datasize - *write;
  62 }
  63
  64 /*
  65  * hv_get_next_write_location()
  66  *
  67  * Get the next write location for the specified ring buffer
  68  *
  69  */
  70 static inline u32
  71 hv_get_next_write_location(struct hv_ring_buffer_info *ring_info)
  72 {
  73         u32 next = ring_info->ring_buffer->write_index;
  74
  75         return next;
  76 }
  77
  78 /*
  79  * hv_set_next_write_location()
  80  *
  81  * Set the next write location for the specified ring buffer
  82  *
  83  */
  84 static inline void
  85 hv_set_next_write_location(struct hv_ring_buffer_info *ring_info,
  86                      u32 next_write_location)
  87 {
  88         ring_info->ring_buffer->write_index = next_write_location;
  89 }
  90
  91 /*
  92  * hv_get_next_read_location()
  93  *
  94  * Get the next read location for the specified ring buffer
  95  */
  96 static inline u32
  97 hv_get_next_read_location(struct hv_ring_buffer_info *ring_info)
  98 {
  99         u32 next = ring_info->ring_buffer->read_index;
 100
 101         return next;
 102 }
 103
 104 /*
 105  * hv_get_next_readlocation_withoffset()
 106  *
 107  * Get the next read location + offset for the specified ring buffer.
 108  * This allows the caller to skip
 109  */
 110 static inline u32
 111 hv_get_next_readlocation_withoffset(struct hv_ring_buffer_info *ring_info,
 112                                  u32 offset)
 113 {
 114         u32 next = ring_info->ring_buffer->read_index;
 115
 116         next += offset;
 117         next %= ring_info->ring_datasize;
 118
 119         return next;
 120 }
 121
 122 /*
 123  *
 124  * hv_set_next_read_location()
 125  *
 126  * Set the next read location for the specified ring buffer
 127  *
 128  */
 129 static inline void
 130 hv_set_next_read_location(struct hv_ring_buffer_info *ring_info,
 131                     u32 next_read_location)
 132 {
 133         ring_info->ring_buffer->read_index = next_read_location;
 134 }
 135
 136
 137 /*
 138  *
 139  * hv_get_ring_buffer()
 140  *
 141  * Get the start of the ring buffer
 142  */
 143 static inline void *
 144 hv_get_ring_buffer(struct hv_ring_buffer_info *ring_info)
 145 {
 146         return (void *)ring_info->ring_buffer->buffer;
 147 }
 148
 149
 150 /*
 151  *
 152  * hv_get_ring_buffersize()
 153  *
 154  * Get the size of the ring buffer
 155  */
 156 static inline u32
 157 hv_get_ring_buffersize(struct hv_ring_buffer_info *ring_info)
 158 {
 159         return ring_info->ring_datasize;
 160 }
 161
 162 /*
 163  *
 164  * hv_get_ring_bufferindices()
 165  *
 166  * Get the read and write indices as u64 of the specified ring buffer
 167  *
 168  */
 169 static inline u64
 170 hv_get_ring_bufferindices(struct hv_ring_buffer_info *ring_info)
 171 {
 172         return (u64)ring_info->ring_buffer->write_index << 32;
 173 }
 174
 175 /*
 176  *
 177  * hv_copyfrom_ringbuffer()
 178  *
 179  * Helper routine to copy to source from ring buffer.
 180  * Assume there is enough room. Handles wrap-around in src case only!!
 181  *
 182  */
 183 static u32 hv_copyfrom_ringbuffer(
 184         struct hv_ring_buffer_info      *ring_info,
 185         void                            *dest,
 186         u32                             destlen,
 187         u32                             start_read_offset)
 188 {
 189         void *ring_buffer = hv_get_ring_buffer(ring_info);
 190         u32 ring_buffer_size = hv_get_ring_buffersize(ring_info);
 191
 192         u32 frag_len;
 193
 194         /* wrap-around detected at the src */
 195         if (destlen > ring_buffer_size - start_read_offset) {
 196                 frag_len = ring_buffer_size - start_read_offset;
 197
 198                 memcpy(dest, ring_buffer + start_read_offset, frag_len);
 199                 memcpy(dest + frag_len, ring_buffer, destlen - frag_len);
 200         } else
 201
 202                 memcpy(dest, ring_buffer + start_read_offset, destlen);
 203
 204
 205         start_read_offset += destlen;
 206         start_read_offset %= ring_buffer_size;
 207
 208         return start_read_offset;
 209 }
 210
 211
 212 /*
 213  *
 214  * hv_copyto_ringbuffer()
 215  *
 216  * Helper routine to copy from source to ring buffer.
 217  * Assume there is enough room. Handles wrap-around in dest case only!!
 218  *
 219  */
 220 static u32 hv_copyto_ringbuffer(
 221         struct hv_ring_buffer_info      *ring_info,
 222         u32                             start_write_offset,
 223         void                            *src,
 224         u32                             srclen)
 225 {
 226         void *ring_buffer = hv_get_ring_buffer(ring_info);
 227         u32 ring_buffer_size = hv_get_ring_buffersize(ring_info);
 228         u32 frag_len;
 229
 230         /* wrap-around detected! */
 231         if (srclen > ring_buffer_size - start_write_offset) {
 232                 frag_len = ring_buffer_size - start_write_offset;
 233                 memcpy(ring_buffer + start_write_offset, src, frag_len);
 234                 memcpy(ring_buffer, src + frag_len, srclen - frag_len);
 235         } else
 236                 memcpy(ring_buffer + start_write_offset, src, srclen);
 237
 238         start_write_offset += srclen;
 239         start_write_offset %= ring_buffer_size;
 240
 241         return start_write_offset;
 242 }
 243
 244 /*
 245  *
 246  * hv_ringbuffer_get_debuginfo()
 247  *
 248  * Get various debug metrics for the specified ring buffer
 249  *
 250  */
 251 void hv_ringbuffer_get_debuginfo(struct hv_ring_buffer_info *ring_info,
 252                             struct hv_ring_buffer_debug_info *debug_info)
 253 {
 254         u32 bytes_avail_towrite;
 255         u32 bytes_avail_toread;
 256
 257         if (ring_info->ring_buffer) {
 258                 hv_get_ringbuffer_availbytes(ring_info,
 259                                         &bytes_avail_toread,
 260                                         &bytes_avail_towrite);
 261
 262                 debug_info->bytes_avail_toread = bytes_avail_toread;
 263                 debug_info->bytes_avail_towrite = bytes_avail_towrite;
 264                 debug_info->current_read_index =
 265                         ring_info->ring_buffer->read_index;
 266                 debug_info->current_write_index =
 267                         ring_info->ring_buffer->write_index;
 268                 debug_info->current_interrupt_mask =
 269                         ring_info->ring_buffer->interrupt_mask;
 270         }
 271 }
 272
 273
 274 /*
 275  *
 276  * hv_get_ringbuffer_interrupt_mask()
 277  *
 278  * Get the interrupt mask for the specified ring buffer
 279  *
 280  */
 281 u32 hv_get_ringbuffer_interrupt_mask(struct hv_ring_buffer_info *rbi)
 282 {
 283         return rbi->ring_buffer->interrupt_mask;
 284 }
 285
 286 /*
 287  *
 288  * hv_ringbuffer_init()
 289  *
 290  *Initialize the ring buffer
 291  *
 292  */
 293 int hv_ringbuffer_init(struct hv_ring_buffer_info *ring_info,
 294                    void *buffer, u32 buflen)
 295 {
 296         if (sizeof(struct hv_ring_buffer) != PAGE_SIZE)
 297                 return -EINVAL;
 298
 299         memset(ring_info, 0, sizeof(struct hv_ring_buffer_info));
 300
 301         ring_info->ring_buffer = (struct hv_ring_buffer *)buffer;
 302         ring_info->ring_buffer->read_index =
 303                 ring_info->ring_buffer->write_index = 0;
 304
 305         ring_info->ring_size = buflen;
 306         ring_info->ring_datasize = buflen - sizeof(struct hv_ring_buffer);
 307
 308         spin_lock_init(&ring_info->ring_lock);
 309
 310         return 0;
 311 }
 312
 313 /*
 314  *
 315  * hv_ringbuffer_cleanup()
 316  *
 317  * Cleanup the ring buffer
 318  *
 319  */
 320 void hv_ringbuffer_cleanup(struct hv_ring_buffer_info *ring_info)
 321 {
 322 }
 323
 324 /*
 325  *
 326  * hv_ringbuffer_write()
 327  *
 328  * Write to the ring buffer
 329  *
 330  */
 331 int hv_ringbuffer_write(struct hv_ring_buffer_info *outring_info,
 332                     struct scatterlist *sglist, u32 sgcount)
 333 {
 334         int i = 0;
 335         u32 bytes_avail_towrite;
 336         u32 bytes_avail_toread;
 337         u32 totalbytes_towrite = 0;
 338
 339         struct scatterlist *sg;
 340         u32 next_write_location;
 341         u64 prev_indices = 0;
 342         unsigned long flags;
 343
 344         for_each_sg(sglist, sg, sgcount, i)
 345         {
 346                 totalbytes_towrite += sg->length;
 347         }
 348
 349         totalbytes_towrite += sizeof(u64);
 350
 351         spin_lock_irqsave(&outring_info->ring_lock, flags);
 352
 353         hv_get_ringbuffer_availbytes(outring_info,
 354                                 &bytes_avail_toread,
 355                                 &bytes_avail_towrite);
 356
 357
 358         /* If there is only room for the packet, assume it is full. */
 359         /* Otherwise, the next time around, we think the ring buffer */
 360         /* is empty since the read index == write index */
 361         if (bytes_avail_towrite <= totalbytes_towrite) {
 362                 spin_unlock_irqrestore(&outring_info->ring_lock, flags);
 363                 return -EAGAIN;
 364         }
 365
 366         /* Write to the ring buffer */
 367         next_write_location = hv_get_next_write_location(outring_info);
 368
 369         for_each_sg(sglist, sg, sgcount, i)
 370         {
 371                 next_write_location = hv_copyto_ringbuffer(outring_info,
 372                                                      next_write_location,
 373                                                      sg_virt(sg),
 374                                                      sg->length);
 375         }
 376
 377         /* Set previous packet start */
 378         prev_indices = hv_get_ring_bufferindices(outring_info);
 379
 380         next_write_location = hv_copyto_ringbuffer(outring_info,
 381                                              next_write_location,
 382                                              &prev_indices,
 383                                              sizeof(u64));
 384
 385         /* Make sure we flush all writes before updating the writeIndex */
 386         wmb();
 387
 388         /* Now, update the write location */
 389         hv_set_next_write_location(outring_info, next_write_location);
 390
 391
 392         spin_unlock_irqrestore(&outring_info->ring_lock, flags);
 393         return 0;
 394 }
 395
 396
 397 /*
 398  *
 399  * hv_ringbuffer_peek()
 400  *
 401  * Read without advancing the read index
 402  *
 403  */
 404 int hv_ringbuffer_peek(struct hv_ring_buffer_info *Inring_info,
 405                    void *Buffer, u32 buflen)
 406 {
 407         u32 bytes_avail_towrite;
 408         u32 bytes_avail_toread;
 409         u32 next_read_location = 0;
 410         unsigned long flags;
 411
 412         spin_lock_irqsave(&Inring_info->ring_lock, flags);
 413
 414         hv_get_ringbuffer_availbytes(Inring_info,
 415                                 &bytes_avail_toread,
 416                                 &bytes_avail_towrite);
 417
 418         /* Make sure there is something to read */
 419         if (bytes_avail_toread < buflen) {
 420
 421                 spin_unlock_irqrestore(&Inring_info->ring_lock, flags);
 422
 423                 return -EAGAIN;
 424         }
 425
 426         /* Convert to byte offset */
 427         next_read_location = hv_get_next_read_location(Inring_info);
 428
 429         next_read_location = hv_copyfrom_ringbuffer(Inring_info,
 430                                                 Buffer,
 431                                                 buflen,
 432                                                 next_read_location);
 433
 434         spin_unlock_irqrestore(&Inring_info->ring_lock, flags);
 435
 436         return 0;
 437 }
 438
 439
 440 /*
 441  *
 442  * hv_ringbuffer_read()
 443  *
 444  * Read and advance the read index
 445  *
 446  */
 447 int hv_ringbuffer_read(struct hv_ring_buffer_info *inring_info, void *buffer,
 448                    u32 buflen, u32 offset)
 449 {
 450         u32 bytes_avail_towrite;
 451         u32 bytes_avail_toread;
 452         u32 next_read_location = 0;
 453         u64 prev_indices = 0;
 454         unsigned long flags;
 455
 456         if (buflen <= 0)
 457                 return -EINVAL;
 458
 459         spin_lock_irqsave(&inring_info->ring_lock, flags);
 460
 461         hv_get_ringbuffer_availbytes(inring_info,
 462                                 &bytes_avail_toread,
 463                                 &bytes_avail_towrite);
 464
 465         /* Make sure there is something to read */
 466         if (bytes_avail_toread < buflen) {
 467                 spin_unlock_irqrestore(&inring_info->ring_lock, flags);
 468
 469                 return -EAGAIN;
 470         }
 471
 472         next_read_location =
 473                 hv_get_next_readlocation_withoffset(inring_info, offset);
 474
 475         next_read_location = hv_copyfrom_ringbuffer(inring_info,
 476                                                 buffer,
 477                                                 buflen,
 478                                                 next_read_location);
 479
 480         next_read_location = hv_copyfrom_ringbuffer(inring_info,
 481                                                 &prev_indices,
 482                                                 sizeof(u64),
 483                                                 next_read_location);
 484
 485         /* Make sure all reads are done before we update the read index since */
 486         /* the writer may start writing to the read area once the read index */
 487         /*is updated */
 488         mb();
 489
 490         /* Update the read index */
 491         hv_set_next_read_location(inring_info, next_read_location);
 492
 493         spin_unlock_irqrestore(&inring_info->ring_lock, flags);
 494
 495         return 0;
 496 }