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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 #define VMBUS_PKT_TRAILER 8
36
37 /*
38 * When we write to the ring buffer, check if the host needs to
39 * be signaled. Here is the details of this protocol:
40 *
41 * 1. The host guarantees that while it is draining the
42 * ring buffer, it will set the interrupt_mask to
43 * indicate it does not need to be interrupted when
44 * new data is placed.
45 *
46 * 2. The host guarantees that it will completely drain
47 * the ring buffer before exiting the read loop. Further,
48 * once the ring buffer is empty, it will clear the
49 * interrupt_mask and re-check to see if new data has
50 * arrived.
51 *
52 * KYS: Oct. 30, 2016:
53 * It looks like Windows hosts have logic to deal with DOS attacks that
54 * can be triggered if it receives interrupts when it is not expecting
55 * the interrupt. The host expects interrupts only when the ring
56 * transitions from empty to non-empty (or full to non full on the guest
57 * to host ring).
58 * So, base the signaling decision solely on the ring state until the
59 * host logic is fixed.
60 */
61
62 static void hv_signal_on_write(u32 old_write, struct vmbus_channel *channel)
63 {
64 struct hv_ring_buffer_info *rbi = &channel->outbound;
65
66 virt_mb();
67 if (READ_ONCE(rbi->ring_buffer->interrupt_mask))
68 return;
69
70 /* check interrupt_mask before read_index */
71 virt_rmb();
72 /*
73 * This is the only case we need to signal when the
74 * ring transitions from being empty to non-empty.
75 */
76 if (old_write == READ_ONCE(rbi->ring_buffer->read_index))
77 vmbus_setevent(channel);
78 }
79
80 /* Get the next write location for the specified ring buffer. */
81 static inline u32
82 hv_get_next_write_location(struct hv_ring_buffer_info *ring_info)
83 {
84 u32 next = ring_info->ring_buffer->write_index;
85
86 return next;
87 }
88
89 /* Set the next write location for the specified ring buffer. */
90 static inline void
91 hv_set_next_write_location(struct hv_ring_buffer_info *ring_info,
92 u32 next_write_location)
93 {
94 ring_info->ring_buffer->write_index = next_write_location;
95 }
96
97 /* Get the next read location for the specified ring buffer. */
98 static inline u32
99 hv_get_next_read_location(const struct hv_ring_buffer_info *ring_info)
100 {
101 return ring_info->ring_buffer->read_index;
102 }
103
104 /*
105 * Get the next read location + offset for the specified ring buffer.
106 * This allows the caller to skip.
107 */
108 static inline u32
109 hv_get_next_readlocation_withoffset(const struct hv_ring_buffer_info *ring_info,
110 u32 offset)
111 {
112 u32 next = ring_info->ring_buffer->read_index;
113
114 next += offset;
115 if (next >= ring_info->ring_datasize)
116 next -= ring_info->ring_datasize;
117
118 return next;
119 }
120
121 /* Set the next read location for the specified ring buffer. */
122 static inline void
123 hv_set_next_read_location(struct hv_ring_buffer_info *ring_info,
124 u32 next_read_location)
125 {
126 ring_info->ring_buffer->read_index = next_read_location;
127 ring_info->priv_read_index = next_read_location;
128 }
129
130 /* Get the size of the ring buffer. */
131 static inline u32
132 hv_get_ring_buffersize(const struct hv_ring_buffer_info *ring_info)
133 {
134 return ring_info->ring_datasize;
135 }
136
137 /* Get the read and write indices as u64 of the specified ring buffer. */
138 static inline u64
139 hv_get_ring_bufferindices(struct hv_ring_buffer_info *ring_info)
140 {
141 return (u64)ring_info->ring_buffer->write_index << 32;
142 }
143
144 /*
145 * Helper routine to copy to source from ring buffer.
146 * Assume there is enough room. Handles wrap-around in src case only!!
147 */
148 static u32 hv_copyfrom_ringbuffer(
149 const struct hv_ring_buffer_info *ring_info,
150 void *dest,
151 u32 destlen,
152 u32 start_read_offset)
153 {
154 void *ring_buffer = hv_get_ring_buffer(ring_info);
155 u32 ring_buffer_size = hv_get_ring_buffersize(ring_info);
156
157 memcpy(dest, ring_buffer + start_read_offset, destlen);
158
159 start_read_offset += destlen;
160 if (start_read_offset >= ring_buffer_size)
161 start_read_offset -= ring_buffer_size;
162
163 return start_read_offset;
164 }
165
166
167 /*
168 * Helper routine to copy from source to ring buffer.
169 * Assume there is enough room. Handles wrap-around in dest case only!!
170 */
171 static u32 hv_copyto_ringbuffer(
172 struct hv_ring_buffer_info *ring_info,
173 u32 start_write_offset,
174 const void *src,
175 u32 srclen)
176 {
177 void *ring_buffer = hv_get_ring_buffer(ring_info);
178 u32 ring_buffer_size = hv_get_ring_buffersize(ring_info);
179
180 memcpy(ring_buffer + start_write_offset, src, srclen);
181
182 start_write_offset += srclen;
183 if (start_write_offset >= ring_buffer_size)
184 start_write_offset -= ring_buffer_size;
185
186 return start_write_offset;
187 }
188
189 /* Get various debug metrics for the specified ring buffer. */
190 void hv_ringbuffer_get_debuginfo(const struct hv_ring_buffer_info *ring_info,
191 struct hv_ring_buffer_debug_info *debug_info)
192 {
193 u32 bytes_avail_towrite;
194 u32 bytes_avail_toread;
195
196 if (ring_info->ring_buffer) {
197 hv_get_ringbuffer_availbytes(ring_info,
198 &bytes_avail_toread,
199 &bytes_avail_towrite);
200
201 debug_info->bytes_avail_toread = bytes_avail_toread;
202 debug_info->bytes_avail_towrite = bytes_avail_towrite;
203 debug_info->current_read_index =
204 ring_info->ring_buffer->read_index;
205 debug_info->current_write_index =
206 ring_info->ring_buffer->write_index;
207 debug_info->current_interrupt_mask =
208 ring_info->ring_buffer->interrupt_mask;
209 }
210 }
211 EXPORT_SYMBOL_GPL(hv_ringbuffer_get_debuginfo);
212
213 /* Initialize the ring buffer. */
214 int hv_ringbuffer_init(struct hv_ring_buffer_info *ring_info,
215 struct page *pages, u32 page_cnt)
216 {
217 int i;
218 struct page **pages_wraparound;
219
220 BUILD_BUG_ON((sizeof(struct hv_ring_buffer) != PAGE_SIZE));
221
222 memset(ring_info, 0, sizeof(struct hv_ring_buffer_info));
223
224 /*
225 * First page holds struct hv_ring_buffer, do wraparound mapping for
226 * the rest.
227 */
228 pages_wraparound = kzalloc(sizeof(struct page *) * (page_cnt * 2 - 1),
229 GFP_KERNEL);
230 if (!pages_wraparound)
231 return -ENOMEM;
232
233 pages_wraparound[0] = pages;
234 for (i = 0; i < 2 * (page_cnt - 1); i++)
235 pages_wraparound[i + 1] = &pages[i % (page_cnt - 1) + 1];
236
237 ring_info->ring_buffer = (struct hv_ring_buffer *)
238 vmap(pages_wraparound, page_cnt * 2 - 1, VM_MAP, PAGE_KERNEL);
239
240 kfree(pages_wraparound);
241
242
243 if (!ring_info->ring_buffer)
244 return -ENOMEM;
245
246 ring_info->ring_buffer->read_index =
247 ring_info->ring_buffer->write_index = 0;
248
249 /* Set the feature bit for enabling flow control. */
250 ring_info->ring_buffer->feature_bits.value = 1;
251
252 ring_info->ring_size = page_cnt << PAGE_SHIFT;
253 ring_info->ring_datasize = ring_info->ring_size -
254 sizeof(struct hv_ring_buffer);
255
256 spin_lock_init(&ring_info->ring_lock);
257
258 return 0;
259 }
260
261 /* Cleanup the ring buffer. */
262 void hv_ringbuffer_cleanup(struct hv_ring_buffer_info *ring_info)
263 {
264 vunmap(ring_info->ring_buffer);
265 }
266
267 /* Write to the ring buffer. */
268 int hv_ringbuffer_write(struct vmbus_channel *channel,
269 const struct kvec *kv_list, u32 kv_count)
270 {
271 int i;
272 u32 bytes_avail_towrite;
273 u32 totalbytes_towrite = sizeof(u64);
274 u32 next_write_location;
275 u32 old_write;
276 u64 prev_indices;
277 unsigned long flags;
278 struct hv_ring_buffer_info *outring_info = &channel->outbound;
279
280 if (channel->rescind)
281 return -ENODEV;
282
283 for (i = 0; i < kv_count; i++)
284 totalbytes_towrite += kv_list[i].iov_len;
285
286 spin_lock_irqsave(&outring_info->ring_lock, flags);
287
288 bytes_avail_towrite = hv_get_bytes_to_write(outring_info);
289
290 /*
291 * If there is only room for the packet, assume it is full.
292 * Otherwise, the next time around, we think the ring buffer
293 * is empty since the read index == write index.
294 */
295 if (bytes_avail_towrite <= totalbytes_towrite) {
296 spin_unlock_irqrestore(&outring_info->ring_lock, flags);
297 return -EAGAIN;
298 }
299
300 /* Write to the ring buffer */
301 next_write_location = hv_get_next_write_location(outring_info);
302
303 old_write = next_write_location;
304
305 for (i = 0; i < kv_count; i++) {
306 next_write_location = hv_copyto_ringbuffer(outring_info,
307 next_write_location,
308 kv_list[i].iov_base,
309 kv_list[i].iov_len);
310 }
311
312 /* Set previous packet start */
313 prev_indices = hv_get_ring_bufferindices(outring_info);
314
315 next_write_location = hv_copyto_ringbuffer(outring_info,
316 next_write_location,
317 &prev_indices,
318 sizeof(u64));
319
320 /* Issue a full memory barrier before updating the write index */
321 virt_mb();
322
323 /* Now, update the write location */
324 hv_set_next_write_location(outring_info, next_write_location);
325
326
327 spin_unlock_irqrestore(&outring_info->ring_lock, flags);
328
329 hv_signal_on_write(old_write, channel);
330
331 if (channel->rescind)
332 return -ENODEV;
333
334 return 0;
335 }
336
337 static inline void
338 init_cached_read_index(struct hv_ring_buffer_info *rbi)
339 {
340 rbi->cached_read_index = rbi->ring_buffer->read_index;
341 }
342
343 int hv_ringbuffer_read(struct vmbus_channel *channel,
344 void *buffer, u32 buflen, u32 *buffer_actual_len,
345 u64 *requestid, bool raw)
346 {
347 u32 bytes_avail_toread;
348 u32 next_read_location;
349 u64 prev_indices = 0;
350 struct vmpacket_descriptor desc;
351 u32 offset;
352 u32 packetlen;
353 struct hv_ring_buffer_info *inring_info = &channel->inbound;
354
355 if (buflen <= 0)
356 return -EINVAL;
357
358 *buffer_actual_len = 0;
359 *requestid = 0;
360
361 bytes_avail_toread = hv_get_bytes_to_read(inring_info);
362 /* Make sure there is something to read */
363 if (bytes_avail_toread < sizeof(desc)) {
364 /*
365 * No error is set when there is even no header, drivers are
366 * supposed to analyze buffer_actual_len.
367 */
368 return 0;
369 }
370
371 init_cached_read_index(inring_info);
372
373 next_read_location = hv_get_next_read_location(inring_info);
374 next_read_location = hv_copyfrom_ringbuffer(inring_info, &desc,
375 sizeof(desc),
376 next_read_location);
377
378 offset = raw ? 0 : (desc.offset8 << 3);
379 packetlen = (desc.len8 << 3) - offset;
380 *buffer_actual_len = packetlen;
381 *requestid = desc.trans_id;
382
383 if (bytes_avail_toread < packetlen + offset)
384 return -EAGAIN;
385
386 if (packetlen > buflen)
387 return -ENOBUFS;
388
389 next_read_location =
390 hv_get_next_readlocation_withoffset(inring_info, offset);
391
392 next_read_location = hv_copyfrom_ringbuffer(inring_info,
393 buffer,
394 packetlen,
395 next_read_location);
396
397 next_read_location = hv_copyfrom_ringbuffer(inring_info,
398 &prev_indices,
399 sizeof(u64),
400 next_read_location);
401
402 /*
403 * Make sure all reads are done before we update the read index since
404 * the writer may start writing to the read area once the read index
405 * is updated.
406 */
407 virt_mb();
408
409 /* Update the read index */
410 hv_set_next_read_location(inring_info, next_read_location);
411
412 hv_signal_on_read(channel);
413
414 return 0;
415 }
416
417 /*
418 * Determine number of bytes available in ring buffer after
419 * the current iterator (priv_read_index) location.
420 *
421 * This is similar to hv_get_bytes_to_read but with private
422 * read index instead.
423 */
424 static u32 hv_pkt_iter_avail(const struct hv_ring_buffer_info *rbi)
425 {
426 u32 priv_read_loc = rbi->priv_read_index;
427 u32 write_loc = READ_ONCE(rbi->ring_buffer->write_index);
428
429 if (write_loc >= priv_read_loc)
430 return write_loc - priv_read_loc;
431 else
432 return (rbi->ring_datasize - priv_read_loc) + write_loc;
433 }
434
435 /*
436 * Get first vmbus packet from ring buffer after read_index
437 *
438 * If ring buffer is empty, returns NULL and no other action needed.
439 */
440 struct vmpacket_descriptor *hv_pkt_iter_first(struct vmbus_channel *channel)
441 {
442 struct hv_ring_buffer_info *rbi = &channel->inbound;
443
444 /* set state for later hv_signal_on_read() */
445 init_cached_read_index(rbi);
446
447 if (hv_pkt_iter_avail(rbi) < sizeof(struct vmpacket_descriptor))
448 return NULL;
449
450 return hv_get_ring_buffer(rbi) + rbi->priv_read_index;
451 }
452 EXPORT_SYMBOL_GPL(hv_pkt_iter_first);
453
454 /*
455 * Get next vmbus packet from ring buffer.
456 *
457 * Advances the current location (priv_read_index) and checks for more
458 * data. If the end of the ring buffer is reached, then return NULL.
459 */
460 struct vmpacket_descriptor *
461 __hv_pkt_iter_next(struct vmbus_channel *channel,
462 const struct vmpacket_descriptor *desc)
463 {
464 struct hv_ring_buffer_info *rbi = &channel->inbound;
465 u32 packetlen = desc->len8 << 3;
466 u32 dsize = rbi->ring_datasize;
467
468 /* bump offset to next potential packet */
469 rbi->priv_read_index += packetlen + VMBUS_PKT_TRAILER;
470 if (rbi->priv_read_index >= dsize)
471 rbi->priv_read_index -= dsize;
472
473 /* more data? */
474 if (hv_pkt_iter_avail(rbi) < sizeof(struct vmpacket_descriptor))
475 return NULL;
476 else
477 return hv_get_ring_buffer(rbi) + rbi->priv_read_index;
478 }
479 EXPORT_SYMBOL_GPL(__hv_pkt_iter_next);
480
481 /*
482 * Update host ring buffer after iterating over packets.
483 */
484 void hv_pkt_iter_close(struct vmbus_channel *channel)
485 {
486 struct hv_ring_buffer_info *rbi = &channel->inbound;
487
488 /*
489 * Make sure all reads are done before we update the read index since
490 * the writer may start writing to the read area once the read index
491 * is updated.
492 */
493 virt_rmb();
494 rbi->ring_buffer->read_index = rbi->priv_read_index;
495
496 hv_signal_on_read(channel);
497 }
498 EXPORT_SYMBOL_GPL(hv_pkt_iter_close);