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 #include <linux/uio.h>
  30 #include <linux/vmalloc.h>
  31 #include <linux/slab.h>
  32
  33 #include "hyperv_vmbus.h"
  34
  35 void hv_begin_read(struct hv_ring_buffer_info *rbi)
  36 {
  37         rbi->ring_buffer->interrupt_mask = 1;
  38         virt_mb();
  39 }
  40
  41 u32 hv_end_read(struct hv_ring_buffer_info *rbi)
  42 {
  43
  44         rbi->ring_buffer->interrupt_mask = 0;
  45         virt_mb();
  46
  47         /*
  48          * Now check to see if the ring buffer is still empty.
  49          * If it is not, we raced and we need to process new
  50          * incoming messages.
  51          */
  52         return hv_get_bytes_to_read(rbi);
  53 }
  54
  55 /*
  56  * When we write to the ring buffer, check if the host needs to
  57  * be signaled. Here is the details of this protocol:
  58  *
  59  *      1. The host guarantees that while it is draining the
  60  *         ring buffer, it will set the interrupt_mask to
  61  *         indicate it does not need to be interrupted when
  62  *         new data is placed.
  63  *
  64  *      2. The host guarantees that it will completely drain
  65  *         the ring buffer before exiting the read loop. Further,
  66  *         once the ring buffer is empty, it will clear the
  67  *         interrupt_mask and re-check to see if new data has
  68  *         arrived.
  69  *
  70  * KYS: Oct. 30, 2016:
  71  * It looks like Windows hosts have logic to deal with DOS attacks that
  72  * can be triggered if it receives interrupts when it is not expecting
  73  * the interrupt. The host expects interrupts only when the ring
  74  * transitions from empty to non-empty (or full to non full on the guest
  75  * to host ring).
  76  * So, base the signaling decision solely on the ring state until the
  77  * host logic is fixed.
  78  */
  79
  80 static void hv_signal_on_write(u32 old_write, struct vmbus_channel *channel,
  81                                bool kick_q)
  82 {
  83         struct hv_ring_buffer_info *rbi = &channel->outbound;
  84
  85         virt_mb();
  86         if (READ_ONCE(rbi->ring_buffer->interrupt_mask))
  87                 return;
  88
  89         /* check interrupt_mask before read_index */
  90         virt_rmb();
  91         /*
  92          * This is the only case we need to signal when the
  93          * ring transitions from being empty to non-empty.
  94          */
  95         if (old_write == READ_ONCE(rbi->ring_buffer->read_index))
  96                 vmbus_setevent(channel);
  97
  98         return;
  99 }
 100
 101 /* Get the next write location for the specified ring buffer. */
 102 static inline u32
 103 hv_get_next_write_location(struct hv_ring_buffer_info *ring_info)
 104 {
 105         u32 next = ring_info->ring_buffer->write_index;
 106
 107         return next;
 108 }
 109
 110 /* Set the next write location for the specified ring buffer. */
 111 static inline void
 112 hv_set_next_write_location(struct hv_ring_buffer_info *ring_info,
 113                      u32 next_write_location)
 114 {
 115         ring_info->ring_buffer->write_index = next_write_location;
 116 }
 117
 118 /* Get the next read location for the specified ring buffer. */
 119 static inline u32
 120 hv_get_next_read_location(struct hv_ring_buffer_info *ring_info)
 121 {
 122         u32 next = ring_info->ring_buffer->read_index;
 123
 124         return next;
 125 }
 126
 127 /*
 128  * Get the next read location + offset for the specified ring buffer.
 129  * This allows the caller to skip.
 130  */
 131 static inline u32
 132 hv_get_next_readlocation_withoffset(struct hv_ring_buffer_info *ring_info,
 133                                  u32 offset)
 134 {
 135         u32 next = ring_info->ring_buffer->read_index;
 136
 137         next += offset;
 138         next %= ring_info->ring_datasize;
 139
 140         return next;
 141 }
 142
 143 /* Set the next read location for the specified ring buffer. */
 144 static inline void
 145 hv_set_next_read_location(struct hv_ring_buffer_info *ring_info,
 146                     u32 next_read_location)
 147 {
 148         ring_info->ring_buffer->read_index = next_read_location;
 149         ring_info->priv_read_index = next_read_location;
 150 }
 151
 152 /* Get the size of the ring buffer. */
 153 static inline u32
 154 hv_get_ring_buffersize(struct hv_ring_buffer_info *ring_info)
 155 {
 156         return ring_info->ring_datasize;
 157 }
 158
 159 /* Get the read and write indices as u64 of the specified ring buffer. */
 160 static inline u64
 161 hv_get_ring_bufferindices(struct hv_ring_buffer_info *ring_info)
 162 {
 163         return (u64)ring_info->ring_buffer->write_index << 32;
 164 }
 165
 166 /*
 167  * Helper routine to copy to source from ring buffer.
 168  * Assume there is enough room. Handles wrap-around in src case only!!
 169  */
 170 static u32 hv_copyfrom_ringbuffer(
 171         struct hv_ring_buffer_info      *ring_info,
 172         void                            *dest,
 173         u32                             destlen,
 174         u32                             start_read_offset)
 175 {
 176         void *ring_buffer = hv_get_ring_buffer(ring_info);
 177         u32 ring_buffer_size = hv_get_ring_buffersize(ring_info);
 178
 179         memcpy(dest, ring_buffer + start_read_offset, destlen);
 180
 181         start_read_offset += destlen;
 182         start_read_offset %= ring_buffer_size;
 183
 184         return start_read_offset;
 185 }
 186
 187
 188 /*
 189  * Helper routine to copy from source to ring buffer.
 190  * Assume there is enough room. Handles wrap-around in dest case only!!
 191  */
 192 static u32 hv_copyto_ringbuffer(
 193         struct hv_ring_buffer_info      *ring_info,
 194         u32                             start_write_offset,
 195         void                            *src,
 196         u32                             srclen)
 197 {
 198         void *ring_buffer = hv_get_ring_buffer(ring_info);
 199         u32 ring_buffer_size = hv_get_ring_buffersize(ring_info);
 200
 201         memcpy(ring_buffer + start_write_offset, src, srclen);
 202
 203         start_write_offset += srclen;
 204         start_write_offset %= ring_buffer_size;
 205
 206         return start_write_offset;
 207 }
 208
 209 /* Get various debug metrics for the specified ring buffer. */
 210 void hv_ringbuffer_get_debuginfo(struct hv_ring_buffer_info *ring_info,
 211                             struct hv_ring_buffer_debug_info *debug_info)
 212 {
 213         u32 bytes_avail_towrite;
 214         u32 bytes_avail_toread;
 215
 216         if (ring_info->ring_buffer) {
 217                 hv_get_ringbuffer_availbytes(ring_info,
 218                                         &bytes_avail_toread,
 219                                         &bytes_avail_towrite);
 220
 221                 debug_info->bytes_avail_toread = bytes_avail_toread;
 222                 debug_info->bytes_avail_towrite = bytes_avail_towrite;
 223                 debug_info->current_read_index =
 224                         ring_info->ring_buffer->read_index;
 225                 debug_info->current_write_index =
 226                         ring_info->ring_buffer->write_index;
 227                 debug_info->current_interrupt_mask =
 228                         ring_info->ring_buffer->interrupt_mask;
 229         }
 230 }
 231
 232 /* Initialize the ring buffer. */
 233 int hv_ringbuffer_init(struct hv_ring_buffer_info *ring_info,
 234                        struct page *pages, u32 page_cnt)
 235 {
 236         int i;
 237         struct page **pages_wraparound;
 238
 239         BUILD_BUG_ON((sizeof(struct hv_ring_buffer) != PAGE_SIZE));
 240
 241         memset(ring_info, 0, sizeof(struct hv_ring_buffer_info));
 242
 243         /*
 244          * First page holds struct hv_ring_buffer, do wraparound mapping for
 245          * the rest.
 246          */
 247         pages_wraparound = kzalloc(sizeof(struct page *) * (page_cnt * 2 - 1),
 248                                    GFP_KERNEL);
 249         if (!pages_wraparound)
 250                 return -ENOMEM;
 251
 252         pages_wraparound[0] = pages;
 253         for (i = 0; i < 2 * (page_cnt - 1); i++)
 254                 pages_wraparound[i + 1] = &pages[i % (page_cnt - 1) + 1];
 255
 256         ring_info->ring_buffer = (struct hv_ring_buffer *)
 257                 vmap(pages_wraparound, page_cnt * 2 - 1, VM_MAP, PAGE_KERNEL);
 258
 259         kfree(pages_wraparound);
 260
 261
 262         if (!ring_info->ring_buffer)
 263                 return -ENOMEM;
 264
 265         ring_info->ring_buffer->read_index =
 266                 ring_info->ring_buffer->write_index = 0;
 267
 268         /* Set the feature bit for enabling flow control. */
 269         ring_info->ring_buffer->feature_bits.value = 1;
 270
 271         ring_info->ring_size = page_cnt << PAGE_SHIFT;
 272         ring_info->ring_datasize = ring_info->ring_size -
 273                 sizeof(struct hv_ring_buffer);
 274
 275         spin_lock_init(&ring_info->ring_lock);
 276
 277         return 0;
 278 }
 279
 280 /* Cleanup the ring buffer. */
 281 void hv_ringbuffer_cleanup(struct hv_ring_buffer_info *ring_info)
 282 {
 283         vunmap(ring_info->ring_buffer);
 284 }
 285
 286 /* Write to the ring buffer. */
 287 int hv_ringbuffer_write(struct vmbus_channel *channel,
 288                     struct kvec *kv_list, u32 kv_count, bool lock,
 289                     bool kick_q)
 290 {
 291         int i = 0;
 292         u32 bytes_avail_towrite;
 293         u32 totalbytes_towrite = 0;
 294
 295         u32 next_write_location;
 296         u32 old_write;
 297         u64 prev_indices = 0;
 298         unsigned long flags = 0;
 299         struct hv_ring_buffer_info *outring_info = &channel->outbound;
 300
 301         for (i = 0; i < kv_count; i++)
 302                 totalbytes_towrite += kv_list[i].iov_len;
 303
 304         totalbytes_towrite += sizeof(u64);
 305
 306         if (lock)
 307                 spin_lock_irqsave(&outring_info->ring_lock, flags);
 308
 309         bytes_avail_towrite = hv_get_bytes_to_write(outring_info);
 310
 311         /*
 312          * If there is only room for the packet, assume it is full.
 313          * Otherwise, the next time around, we think the ring buffer
 314          * is empty since the read index == write index.
 315          */
 316         if (bytes_avail_towrite <= totalbytes_towrite) {
 317                 if (lock)
 318                         spin_unlock_irqrestore(&outring_info->ring_lock, flags);
 319                 return -EAGAIN;
 320         }
 321
 322         /* Write to the ring buffer */
 323         next_write_location = hv_get_next_write_location(outring_info);
 324
 325         old_write = next_write_location;
 326
 327         for (i = 0; i < kv_count; i++) {
 328                 next_write_location = hv_copyto_ringbuffer(outring_info,
 329                                                      next_write_location,
 330                                                      kv_list[i].iov_base,
 331                                                      kv_list[i].iov_len);
 332         }
 333
 334         /* Set previous packet start */
 335         prev_indices = hv_get_ring_bufferindices(outring_info);
 336
 337         next_write_location = hv_copyto_ringbuffer(outring_info,
 338                                              next_write_location,
 339                                              &prev_indices,
 340                                              sizeof(u64));
 341
 342         /* Issue a full memory barrier before updating the write index */
 343         virt_mb();
 344
 345         /* Now, update the write location */
 346         hv_set_next_write_location(outring_info, next_write_location);
 347
 348
 349         if (lock)
 350                 spin_unlock_irqrestore(&outring_info->ring_lock, flags);
 351
 352         hv_signal_on_write(old_write, channel, kick_q);
 353         return 0;
 354 }
 355
 356 int hv_ringbuffer_read(struct vmbus_channel *channel,
 357                        void *buffer, u32 buflen, u32 *buffer_actual_len,
 358                        u64 *requestid, bool raw)
 359 {
 360         u32 bytes_avail_toread;
 361         u32 next_read_location = 0;
 362         u64 prev_indices = 0;
 363         struct vmpacket_descriptor desc;
 364         u32 offset;
 365         u32 packetlen;
 366         int ret = 0;
 367         struct hv_ring_buffer_info *inring_info = &channel->inbound;
 368
 369         if (buflen <= 0)
 370                 return -EINVAL;
 371
 372
 373         *buffer_actual_len = 0;
 374         *requestid = 0;
 375
 376         bytes_avail_toread = hv_get_bytes_to_read(inring_info);
 377         /* Make sure there is something to read */
 378         if (bytes_avail_toread < sizeof(desc)) {
 379                 /*
 380                  * No error is set when there is even no header, drivers are
 381                  * supposed to analyze buffer_actual_len.
 382                  */
 383                 return ret;
 384         }
 385
 386         init_cached_read_index(channel);
 387         next_read_location = hv_get_next_read_location(inring_info);
 388         next_read_location = hv_copyfrom_ringbuffer(inring_info, &desc,
 389                                                     sizeof(desc),
 390                                                     next_read_location);
 391
 392         offset = raw ? 0 : (desc.offset8 << 3);
 393         packetlen = (desc.len8 << 3) - offset;
 394         *buffer_actual_len = packetlen;
 395         *requestid = desc.trans_id;
 396
 397         if (bytes_avail_toread < packetlen + offset)
 398                 return -EAGAIN;
 399
 400         if (packetlen > buflen)
 401                 return -ENOBUFS;
 402
 403         next_read_location =
 404                 hv_get_next_readlocation_withoffset(inring_info, offset);
 405
 406         next_read_location = hv_copyfrom_ringbuffer(inring_info,
 407                                                 buffer,
 408                                                 packetlen,
 409                                                 next_read_location);
 410
 411         next_read_location = hv_copyfrom_ringbuffer(inring_info,
 412                                                 &prev_indices,
 413                                                 sizeof(u64),
 414                                                 next_read_location);
 415
 416         /*
 417          * Make sure all reads are done before we update the read index since
 418          * the writer may start writing to the read area once the read index
 419          * is updated.
 420          */
 421         virt_mb();
 422
 423         /* Update the read index */
 424         hv_set_next_read_location(inring_info, next_read_location);
 425
 426         hv_signal_on_read(channel);
 427
 428         return ret;
 429 }