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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
31#include "hyperv_vmbus.h"
32
33void hv_begin_read(struct hv_ring_buffer_info *rbi)
34{
35 rbi->ring_buffer->interrupt_mask = 1;
36 mb();
37}
38
39u32 hv_end_read(struct hv_ring_buffer_info *rbi)
40{
41 u32 read;
42 u32 write;
43
44 rbi->ring_buffer->interrupt_mask = 0;
45 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 hv_get_ringbuffer_availbytes(rbi, &read, &write);
53
54 return read;
55}
56
57/*
58 * When we write to the ring buffer, check if the host needs to
59 * be signaled. Here is the details of this protocol:
60 *
61 * 1. The host guarantees that while it is draining the
62 * ring buffer, it will set the interrupt_mask to
63 * indicate it does not need to be interrupted when
64 * new data is placed.
65 *
66 * 2. The host guarantees that it will completely drain
67 * the ring buffer before exiting the read loop. Further,
68 * once the ring buffer is empty, it will clear the
69 * interrupt_mask and re-check to see if new data has
70 * arrived.
71 */
72
73static bool hv_need_to_signal(u32 old_write, struct hv_ring_buffer_info *rbi)
74{
75 mb();
76 if (rbi->ring_buffer->interrupt_mask)
77 return false;
78
79 /* check interrupt_mask before read_index */
80 rmb();
81 /*
82 * This is the only case we need to signal when the
83 * ring transitions from being empty to non-empty.
84 */
85 if (old_write == rbi->ring_buffer->read_index)
86 return true;
87
88 return false;
89}
90
91/*
92 * To optimize the flow management on the send-side,
93 * when the sender is blocked because of lack of
94 * sufficient space in the ring buffer, potential the
95 * consumer of the ring buffer can signal the producer.
96 * This is controlled by the following parameters:
97 *
98 * 1. pending_send_sz: This is the size in bytes that the
99 * producer is trying to send.
100 * 2. The feature bit feat_pending_send_sz set to indicate if
101 * the consumer of the ring will signal when the ring
102 * state transitions from being full to a state where
103 * there is room for the producer to send the pending packet.
104 */
105
106static bool hv_need_to_signal_on_read(u32 old_rd,
107 struct hv_ring_buffer_info *rbi)
108{
109 u32 prev_write_sz;
110 u32 cur_write_sz;
111 u32 r_size;
112 u32 write_loc = rbi->ring_buffer->write_index;
113 u32 read_loc = rbi->ring_buffer->read_index;
114 u32 pending_sz = rbi->ring_buffer->pending_send_sz;
115
116 /*
117 * If the other end is not blocked on write don't bother.
118 */
119 if (pending_sz == 0)
120 return false;
121
122 r_size = rbi->ring_datasize;
123 cur_write_sz = write_loc >= read_loc ? r_size - (write_loc - read_loc) :
124 read_loc - write_loc;
125
126 prev_write_sz = write_loc >= old_rd ? r_size - (write_loc - old_rd) :
127 old_rd - write_loc;
128
129
130 if ((prev_write_sz < pending_sz) && (cur_write_sz >= pending_sz))
131 return true;
132
133 return false;
134}
135
136/*
137 * hv_get_next_write_location()
138 *
139 * Get the next write location for the specified ring buffer
140 *
141 */
142static inline u32
143hv_get_next_write_location(struct hv_ring_buffer_info *ring_info)
144{
145 u32 next = ring_info->ring_buffer->write_index;
146
147 return next;
148}
149
150/*
151 * hv_set_next_write_location()
152 *
153 * Set the next write location for the specified ring buffer
154 *
155 */
156static inline void
157hv_set_next_write_location(struct hv_ring_buffer_info *ring_info,
158 u32 next_write_location)
159{
160 ring_info->ring_buffer->write_index = next_write_location;
161}
162
163/*
164 * hv_get_next_read_location()
165 *
166 * Get the next read location for the specified ring buffer
167 */
168static inline u32
169hv_get_next_read_location(struct hv_ring_buffer_info *ring_info)
170{
171 u32 next = ring_info->ring_buffer->read_index;
172
173 return next;
174}
175
176/*
177 * hv_get_next_readlocation_withoffset()
178 *
179 * Get the next read location + offset for the specified ring buffer.
180 * This allows the caller to skip
181 */
182static inline u32
183hv_get_next_readlocation_withoffset(struct hv_ring_buffer_info *ring_info,
184 u32 offset)
185{
186 u32 next = ring_info->ring_buffer->read_index;
187
188 next += offset;
189 next %= ring_info->ring_datasize;
190
191 return next;
192}
193
194/*
195 *
196 * hv_set_next_read_location()
197 *
198 * Set the next read location for the specified ring buffer
199 *
200 */
201static inline void
202hv_set_next_read_location(struct hv_ring_buffer_info *ring_info,
203 u32 next_read_location)
204{
205 ring_info->ring_buffer->read_index = next_read_location;
206}
207
208
209/*
210 *
211 * hv_get_ring_buffer()
212 *
213 * Get the start of the ring buffer
214 */
215static inline void *
216hv_get_ring_buffer(struct hv_ring_buffer_info *ring_info)
217{
218 return (void *)ring_info->ring_buffer->buffer;
219}
220
221
222/*
223 *
224 * hv_get_ring_buffersize()
225 *
226 * Get the size of the ring buffer
227 */
228static inline u32
229hv_get_ring_buffersize(struct hv_ring_buffer_info *ring_info)
230{
231 return ring_info->ring_datasize;
232}
233
234/*
235 *
236 * hv_get_ring_bufferindices()
237 *
238 * Get the read and write indices as u64 of the specified ring buffer
239 *
240 */
241static inline u64
242hv_get_ring_bufferindices(struct hv_ring_buffer_info *ring_info)
243{
244 return (u64)ring_info->ring_buffer->write_index << 32;
245}
246
247/*
248 *
249 * hv_copyfrom_ringbuffer()
250 *
251 * Helper routine to copy to source from ring buffer.
252 * Assume there is enough room. Handles wrap-around in src case only!!
253 *
254 */
255static u32 hv_copyfrom_ringbuffer(
256 struct hv_ring_buffer_info *ring_info,
257 void *dest,
258 u32 destlen,
259 u32 start_read_offset)
260{
261 void *ring_buffer = hv_get_ring_buffer(ring_info);
262 u32 ring_buffer_size = hv_get_ring_buffersize(ring_info);
263
264 u32 frag_len;
265
266 /* wrap-around detected at the src */
267 if (destlen > ring_buffer_size - start_read_offset) {
268 frag_len = ring_buffer_size - start_read_offset;
269
270 memcpy(dest, ring_buffer + start_read_offset, frag_len);
271 memcpy(dest + frag_len, ring_buffer, destlen - frag_len);
272 } else
273
274 memcpy(dest, ring_buffer + start_read_offset, destlen);
275
276
277 start_read_offset += destlen;
278 start_read_offset %= ring_buffer_size;
279
280 return start_read_offset;
281}
282
283
284/*
285 *
286 * hv_copyto_ringbuffer()
287 *
288 * Helper routine to copy from source to ring buffer.
289 * Assume there is enough room. Handles wrap-around in dest case only!!
290 *
291 */
292static u32 hv_copyto_ringbuffer(
293 struct hv_ring_buffer_info *ring_info,
294 u32 start_write_offset,
295 void *src,
296 u32 srclen)
297{
298 void *ring_buffer = hv_get_ring_buffer(ring_info);
299 u32 ring_buffer_size = hv_get_ring_buffersize(ring_info);
300 u32 frag_len;
301
302 /* wrap-around detected! */
303 if (srclen > ring_buffer_size - start_write_offset) {
304 frag_len = ring_buffer_size - start_write_offset;
305 memcpy(ring_buffer + start_write_offset, src, frag_len);
306 memcpy(ring_buffer, src + frag_len, srclen - frag_len);
307 } else
308 memcpy(ring_buffer + start_write_offset, src, srclen);
309
310 start_write_offset += srclen;
311 start_write_offset %= ring_buffer_size;
312
313 return start_write_offset;
314}
315
316/*
317 *
318 * hv_ringbuffer_get_debuginfo()
319 *
320 * Get various debug metrics for the specified ring buffer
321 *
322 */
323void hv_ringbuffer_get_debuginfo(struct hv_ring_buffer_info *ring_info,
324 struct hv_ring_buffer_debug_info *debug_info)
325{
326 u32 bytes_avail_towrite;
327 u32 bytes_avail_toread;
328
329 if (ring_info->ring_buffer) {
330 hv_get_ringbuffer_availbytes(ring_info,
331 &bytes_avail_toread,
332 &bytes_avail_towrite);
333
334 debug_info->bytes_avail_toread = bytes_avail_toread;
335 debug_info->bytes_avail_towrite = bytes_avail_towrite;
336 debug_info->current_read_index =
337 ring_info->ring_buffer->read_index;
338 debug_info->current_write_index =
339 ring_info->ring_buffer->write_index;
340 debug_info->current_interrupt_mask =
341 ring_info->ring_buffer->interrupt_mask;
342 }
343}
344
345/*
346 *
347 * hv_ringbuffer_init()
348 *
349 *Initialize the ring buffer
350 *
351 */
352int hv_ringbuffer_init(struct hv_ring_buffer_info *ring_info,
353 void *buffer, u32 buflen)
354{
355 if (sizeof(struct hv_ring_buffer) != PAGE_SIZE)
356 return -EINVAL;
357
358 memset(ring_info, 0, sizeof(struct hv_ring_buffer_info));
359
360 ring_info->ring_buffer = (struct hv_ring_buffer *)buffer;
361 ring_info->ring_buffer->read_index =
362 ring_info->ring_buffer->write_index = 0;
363
364 ring_info->ring_size = buflen;
365 ring_info->ring_datasize = buflen - sizeof(struct hv_ring_buffer);
366
367 spin_lock_init(&ring_info->ring_lock);
368
369 return 0;
370}
371
372/*
373 *
374 * hv_ringbuffer_cleanup()
375 *
376 * Cleanup the ring buffer
377 *
378 */
379void hv_ringbuffer_cleanup(struct hv_ring_buffer_info *ring_info)
380{
381}
382
383/*
384 *
385 * hv_ringbuffer_write()
386 *
387 * Write to the ring buffer
388 *
389 */
390int hv_ringbuffer_write(struct hv_ring_buffer_info *outring_info,
391 struct kvec *kv_list, u32 kv_count, bool *signal)
392{
393 int i = 0;
394 u32 bytes_avail_towrite;
395 u32 bytes_avail_toread;
396 u32 totalbytes_towrite = 0;
397
398 u32 next_write_location;
399 u32 old_write;
400 u64 prev_indices = 0;
401 unsigned long flags;
402
403 for (i = 0; i < kv_count; i++)
404 totalbytes_towrite += kv_list[i].iov_len;
405
406 totalbytes_towrite += sizeof(u64);
407
408 spin_lock_irqsave(&outring_info->ring_lock, flags);
409
410 hv_get_ringbuffer_availbytes(outring_info,
411 &bytes_avail_toread,
412 &bytes_avail_towrite);
413
414
415 /* If there is only room for the packet, assume it is full. */
416 /* Otherwise, the next time around, we think the ring buffer */
417 /* is empty since the read index == write index */
418 if (bytes_avail_towrite <= totalbytes_towrite) {
419 spin_unlock_irqrestore(&outring_info->ring_lock, flags);
420 return -EAGAIN;
421 }
422
423 /* Write to the ring buffer */
424 next_write_location = hv_get_next_write_location(outring_info);
425
426 old_write = next_write_location;
427
428 for (i = 0; i < kv_count; i++) {
429 next_write_location = hv_copyto_ringbuffer(outring_info,
430 next_write_location,
431 kv_list[i].iov_base,
432 kv_list[i].iov_len);
433 }
434
435 /* Set previous packet start */
436 prev_indices = hv_get_ring_bufferindices(outring_info);
437
438 next_write_location = hv_copyto_ringbuffer(outring_info,
439 next_write_location,
440 &prev_indices,
441 sizeof(u64));
442
443 /* Issue a full memory barrier before updating the write index */
444 mb();
445
446 /* Now, update the write location */
447 hv_set_next_write_location(outring_info, next_write_location);
448
449
450 spin_unlock_irqrestore(&outring_info->ring_lock, flags);
451
452 *signal = hv_need_to_signal(old_write, outring_info);
453 return 0;
454}
455
456
457/*
458 *
459 * hv_ringbuffer_peek()
460 *
461 * Read without advancing the read index
462 *
463 */
464int hv_ringbuffer_peek(struct hv_ring_buffer_info *Inring_info,
465 void *Buffer, u32 buflen)
466{
467 u32 bytes_avail_towrite;
468 u32 bytes_avail_toread;
469 u32 next_read_location = 0;
470 unsigned long flags;
471
472 spin_lock_irqsave(&Inring_info->ring_lock, flags);
473
474 hv_get_ringbuffer_availbytes(Inring_info,
475 &bytes_avail_toread,
476 &bytes_avail_towrite);
477
478 /* Make sure there is something to read */
479 if (bytes_avail_toread < buflen) {
480
481 spin_unlock_irqrestore(&Inring_info->ring_lock, flags);
482
483 return -EAGAIN;
484 }
485
486 /* Convert to byte offset */
487 next_read_location = hv_get_next_read_location(Inring_info);
488
489 next_read_location = hv_copyfrom_ringbuffer(Inring_info,
490 Buffer,
491 buflen,
492 next_read_location);
493
494 spin_unlock_irqrestore(&Inring_info->ring_lock, flags);
495
496 return 0;
497}
498
499
500/*
501 *
502 * hv_ringbuffer_read()
503 *
504 * Read and advance the read index
505 *
506 */
507int hv_ringbuffer_read(struct hv_ring_buffer_info *inring_info, void *buffer,
508 u32 buflen, u32 offset, bool *signal)
509{
510 u32 bytes_avail_towrite;
511 u32 bytes_avail_toread;
512 u32 next_read_location = 0;
513 u64 prev_indices = 0;
514 unsigned long flags;
515 u32 old_read;
516
517 if (buflen <= 0)
518 return -EINVAL;
519
520 spin_lock_irqsave(&inring_info->ring_lock, flags);
521
522 hv_get_ringbuffer_availbytes(inring_info,
523 &bytes_avail_toread,
524 &bytes_avail_towrite);
525
526 old_read = bytes_avail_toread;
527
528 /* Make sure there is something to read */
529 if (bytes_avail_toread < buflen) {
530 spin_unlock_irqrestore(&inring_info->ring_lock, flags);
531
532 return -EAGAIN;
533 }
534
535 next_read_location =
536 hv_get_next_readlocation_withoffset(inring_info, offset);
537
538 next_read_location = hv_copyfrom_ringbuffer(inring_info,
539 buffer,
540 buflen,
541 next_read_location);
542
543 next_read_location = hv_copyfrom_ringbuffer(inring_info,
544 &prev_indices,
545 sizeof(u64),
546 next_read_location);
547
548 /* Make sure all reads are done before we update the read index since */
549 /* the writer may start writing to the read area once the read index */
550 /*is updated */
551 mb();
552
553 /* Update the read index */
554 hv_set_next_read_location(inring_info, next_read_location);
555
556 spin_unlock_irqrestore(&inring_info->ring_lock, flags);
557
558 *signal = hv_need_to_signal_on_read(old_read, inring_info);
559
560 return 0;
561}
1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 *
4 * Copyright (c) 2009, Microsoft Corporation.
5 *
6 * Authors:
7 * Haiyang Zhang <haiyangz@microsoft.com>
8 * Hank Janssen <hjanssen@microsoft.com>
9 * K. Y. Srinivasan <kys@microsoft.com>
10 */
11#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
12
13#include <linux/kernel.h>
14#include <linux/mm.h>
15#include <linux/hyperv.h>
16#include <linux/uio.h>
17#include <linux/vmalloc.h>
18#include <linux/slab.h>
19#include <linux/prefetch.h>
20
21#include "hyperv_vmbus.h"
22
23#define VMBUS_PKT_TRAILER 8
24
25/*
26 * When we write to the ring buffer, check if the host needs to
27 * be signaled. Here is the details of this protocol:
28 *
29 * 1. The host guarantees that while it is draining the
30 * ring buffer, it will set the interrupt_mask to
31 * indicate it does not need to be interrupted when
32 * new data is placed.
33 *
34 * 2. The host guarantees that it will completely drain
35 * the ring buffer before exiting the read loop. Further,
36 * once the ring buffer is empty, it will clear the
37 * interrupt_mask and re-check to see if new data has
38 * arrived.
39 *
40 * KYS: Oct. 30, 2016:
41 * It looks like Windows hosts have logic to deal with DOS attacks that
42 * can be triggered if it receives interrupts when it is not expecting
43 * the interrupt. The host expects interrupts only when the ring
44 * transitions from empty to non-empty (or full to non full on the guest
45 * to host ring).
46 * So, base the signaling decision solely on the ring state until the
47 * host logic is fixed.
48 */
49
50static void hv_signal_on_write(u32 old_write, struct vmbus_channel *channel)
51{
52 struct hv_ring_buffer_info *rbi = &channel->outbound;
53
54 virt_mb();
55 if (READ_ONCE(rbi->ring_buffer->interrupt_mask))
56 return;
57
58 /* check interrupt_mask before read_index */
59 virt_rmb();
60 /*
61 * This is the only case we need to signal when the
62 * ring transitions from being empty to non-empty.
63 */
64 if (old_write == READ_ONCE(rbi->ring_buffer->read_index)) {
65 ++channel->intr_out_empty;
66 vmbus_setevent(channel);
67 }
68}
69
70/* Get the next write location for the specified ring buffer. */
71static inline u32
72hv_get_next_write_location(struct hv_ring_buffer_info *ring_info)
73{
74 u32 next = ring_info->ring_buffer->write_index;
75
76 return next;
77}
78
79/* Set the next write location for the specified ring buffer. */
80static inline void
81hv_set_next_write_location(struct hv_ring_buffer_info *ring_info,
82 u32 next_write_location)
83{
84 ring_info->ring_buffer->write_index = next_write_location;
85}
86
87/* Set the next read location for the specified ring buffer. */
88static inline void
89hv_set_next_read_location(struct hv_ring_buffer_info *ring_info,
90 u32 next_read_location)
91{
92 ring_info->ring_buffer->read_index = next_read_location;
93 ring_info->priv_read_index = next_read_location;
94}
95
96/* Get the size of the ring buffer. */
97static inline u32
98hv_get_ring_buffersize(const struct hv_ring_buffer_info *ring_info)
99{
100 return ring_info->ring_datasize;
101}
102
103/* Get the read and write indices as u64 of the specified ring buffer. */
104static inline u64
105hv_get_ring_bufferindices(struct hv_ring_buffer_info *ring_info)
106{
107 return (u64)ring_info->ring_buffer->write_index << 32;
108}
109
110/*
111 * Helper routine to copy from source to ring buffer.
112 * Assume there is enough room. Handles wrap-around in dest case only!!
113 */
114static u32 hv_copyto_ringbuffer(
115 struct hv_ring_buffer_info *ring_info,
116 u32 start_write_offset,
117 const void *src,
118 u32 srclen)
119{
120 void *ring_buffer = hv_get_ring_buffer(ring_info);
121 u32 ring_buffer_size = hv_get_ring_buffersize(ring_info);
122
123 memcpy(ring_buffer + start_write_offset, src, srclen);
124
125 start_write_offset += srclen;
126 if (start_write_offset >= ring_buffer_size)
127 start_write_offset -= ring_buffer_size;
128
129 return start_write_offset;
130}
131
132/*
133 *
134 * hv_get_ringbuffer_availbytes()
135 *
136 * Get number of bytes available to read and to write to
137 * for the specified ring buffer
138 */
139static void
140hv_get_ringbuffer_availbytes(const struct hv_ring_buffer_info *rbi,
141 u32 *read, u32 *write)
142{
143 u32 read_loc, write_loc, dsize;
144
145 /* Capture the read/write indices before they changed */
146 read_loc = READ_ONCE(rbi->ring_buffer->read_index);
147 write_loc = READ_ONCE(rbi->ring_buffer->write_index);
148 dsize = rbi->ring_datasize;
149
150 *write = write_loc >= read_loc ? dsize - (write_loc - read_loc) :
151 read_loc - write_loc;
152 *read = dsize - *write;
153}
154
155/* Get various debug metrics for the specified ring buffer. */
156int hv_ringbuffer_get_debuginfo(struct hv_ring_buffer_info *ring_info,
157 struct hv_ring_buffer_debug_info *debug_info)
158{
159 u32 bytes_avail_towrite;
160 u32 bytes_avail_toread;
161
162 mutex_lock(&ring_info->ring_buffer_mutex);
163
164 if (!ring_info->ring_buffer) {
165 mutex_unlock(&ring_info->ring_buffer_mutex);
166 return -EINVAL;
167 }
168
169 hv_get_ringbuffer_availbytes(ring_info,
170 &bytes_avail_toread,
171 &bytes_avail_towrite);
172 debug_info->bytes_avail_toread = bytes_avail_toread;
173 debug_info->bytes_avail_towrite = bytes_avail_towrite;
174 debug_info->current_read_index = ring_info->ring_buffer->read_index;
175 debug_info->current_write_index = ring_info->ring_buffer->write_index;
176 debug_info->current_interrupt_mask
177 = ring_info->ring_buffer->interrupt_mask;
178 mutex_unlock(&ring_info->ring_buffer_mutex);
179
180 return 0;
181}
182EXPORT_SYMBOL_GPL(hv_ringbuffer_get_debuginfo);
183
184/* Initialize a channel's ring buffer info mutex locks */
185void hv_ringbuffer_pre_init(struct vmbus_channel *channel)
186{
187 mutex_init(&channel->inbound.ring_buffer_mutex);
188 mutex_init(&channel->outbound.ring_buffer_mutex);
189}
190
191/* Initialize the ring buffer. */
192int hv_ringbuffer_init(struct hv_ring_buffer_info *ring_info,
193 struct page *pages, u32 page_cnt)
194{
195 int i;
196 struct page **pages_wraparound;
197
198 BUILD_BUG_ON((sizeof(struct hv_ring_buffer) != PAGE_SIZE));
199
200 /*
201 * First page holds struct hv_ring_buffer, do wraparound mapping for
202 * the rest.
203 */
204 pages_wraparound = kcalloc(page_cnt * 2 - 1, sizeof(struct page *),
205 GFP_KERNEL);
206 if (!pages_wraparound)
207 return -ENOMEM;
208
209 pages_wraparound[0] = pages;
210 for (i = 0; i < 2 * (page_cnt - 1); i++)
211 pages_wraparound[i + 1] = &pages[i % (page_cnt - 1) + 1];
212
213 ring_info->ring_buffer = (struct hv_ring_buffer *)
214 vmap(pages_wraparound, page_cnt * 2 - 1, VM_MAP, PAGE_KERNEL);
215
216 kfree(pages_wraparound);
217
218
219 if (!ring_info->ring_buffer)
220 return -ENOMEM;
221
222 ring_info->ring_buffer->read_index =
223 ring_info->ring_buffer->write_index = 0;
224
225 /* Set the feature bit for enabling flow control. */
226 ring_info->ring_buffer->feature_bits.value = 1;
227
228 ring_info->ring_size = page_cnt << PAGE_SHIFT;
229 ring_info->ring_size_div10_reciprocal =
230 reciprocal_value(ring_info->ring_size / 10);
231 ring_info->ring_datasize = ring_info->ring_size -
232 sizeof(struct hv_ring_buffer);
233 ring_info->priv_read_index = 0;
234
235 spin_lock_init(&ring_info->ring_lock);
236
237 return 0;
238}
239
240/* Cleanup the ring buffer. */
241void hv_ringbuffer_cleanup(struct hv_ring_buffer_info *ring_info)
242{
243 mutex_lock(&ring_info->ring_buffer_mutex);
244 vunmap(ring_info->ring_buffer);
245 ring_info->ring_buffer = NULL;
246 mutex_unlock(&ring_info->ring_buffer_mutex);
247}
248
249/* Write to the ring buffer. */
250int hv_ringbuffer_write(struct vmbus_channel *channel,
251 const struct kvec *kv_list, u32 kv_count)
252{
253 int i;
254 u32 bytes_avail_towrite;
255 u32 totalbytes_towrite = sizeof(u64);
256 u32 next_write_location;
257 u32 old_write;
258 u64 prev_indices;
259 unsigned long flags;
260 struct hv_ring_buffer_info *outring_info = &channel->outbound;
261
262 if (channel->rescind)
263 return -ENODEV;
264
265 for (i = 0; i < kv_count; i++)
266 totalbytes_towrite += kv_list[i].iov_len;
267
268 spin_lock_irqsave(&outring_info->ring_lock, flags);
269
270 bytes_avail_towrite = hv_get_bytes_to_write(outring_info);
271
272 /*
273 * If there is only room for the packet, assume it is full.
274 * Otherwise, the next time around, we think the ring buffer
275 * is empty since the read index == write index.
276 */
277 if (bytes_avail_towrite <= totalbytes_towrite) {
278 ++channel->out_full_total;
279
280 if (!channel->out_full_flag) {
281 ++channel->out_full_first;
282 channel->out_full_flag = true;
283 }
284
285 spin_unlock_irqrestore(&outring_info->ring_lock, flags);
286 return -EAGAIN;
287 }
288
289 channel->out_full_flag = false;
290
291 /* Write to the ring buffer */
292 next_write_location = hv_get_next_write_location(outring_info);
293
294 old_write = next_write_location;
295
296 for (i = 0; i < kv_count; i++) {
297 next_write_location = hv_copyto_ringbuffer(outring_info,
298 next_write_location,
299 kv_list[i].iov_base,
300 kv_list[i].iov_len);
301 }
302
303 /* Set previous packet start */
304 prev_indices = hv_get_ring_bufferindices(outring_info);
305
306 next_write_location = hv_copyto_ringbuffer(outring_info,
307 next_write_location,
308 &prev_indices,
309 sizeof(u64));
310
311 /* Issue a full memory barrier before updating the write index */
312 virt_mb();
313
314 /* Now, update the write location */
315 hv_set_next_write_location(outring_info, next_write_location);
316
317
318 spin_unlock_irqrestore(&outring_info->ring_lock, flags);
319
320 hv_signal_on_write(old_write, channel);
321
322 if (channel->rescind)
323 return -ENODEV;
324
325 return 0;
326}
327
328int hv_ringbuffer_read(struct vmbus_channel *channel,
329 void *buffer, u32 buflen, u32 *buffer_actual_len,
330 u64 *requestid, bool raw)
331{
332 struct vmpacket_descriptor *desc;
333 u32 packetlen, offset;
334
335 if (unlikely(buflen == 0))
336 return -EINVAL;
337
338 *buffer_actual_len = 0;
339 *requestid = 0;
340
341 /* Make sure there is something to read */
342 desc = hv_pkt_iter_first(channel);
343 if (desc == NULL) {
344 /*
345 * No error is set when there is even no header, drivers are
346 * supposed to analyze buffer_actual_len.
347 */
348 return 0;
349 }
350
351 offset = raw ? 0 : (desc->offset8 << 3);
352 packetlen = (desc->len8 << 3) - offset;
353 *buffer_actual_len = packetlen;
354 *requestid = desc->trans_id;
355
356 if (unlikely(packetlen > buflen))
357 return -ENOBUFS;
358
359 /* since ring is double mapped, only one copy is necessary */
360 memcpy(buffer, (const char *)desc + offset, packetlen);
361
362 /* Advance ring index to next packet descriptor */
363 __hv_pkt_iter_next(channel, desc);
364
365 /* Notify host of update */
366 hv_pkt_iter_close(channel);
367
368 return 0;
369}
370
371/*
372 * Determine number of bytes available in ring buffer after
373 * the current iterator (priv_read_index) location.
374 *
375 * This is similar to hv_get_bytes_to_read but with private
376 * read index instead.
377 */
378static u32 hv_pkt_iter_avail(const struct hv_ring_buffer_info *rbi)
379{
380 u32 priv_read_loc = rbi->priv_read_index;
381 u32 write_loc = READ_ONCE(rbi->ring_buffer->write_index);
382
383 if (write_loc >= priv_read_loc)
384 return write_loc - priv_read_loc;
385 else
386 return (rbi->ring_datasize - priv_read_loc) + write_loc;
387}
388
389/*
390 * Get first vmbus packet from ring buffer after read_index
391 *
392 * If ring buffer is empty, returns NULL and no other action needed.
393 */
394struct vmpacket_descriptor *hv_pkt_iter_first(struct vmbus_channel *channel)
395{
396 struct hv_ring_buffer_info *rbi = &channel->inbound;
397 struct vmpacket_descriptor *desc;
398
399 hv_debug_delay_test(channel, MESSAGE_DELAY);
400 if (hv_pkt_iter_avail(rbi) < sizeof(struct vmpacket_descriptor))
401 return NULL;
402
403 desc = hv_get_ring_buffer(rbi) + rbi->priv_read_index;
404 if (desc)
405 prefetch((char *)desc + (desc->len8 << 3));
406
407 return desc;
408}
409EXPORT_SYMBOL_GPL(hv_pkt_iter_first);
410
411/*
412 * Get next vmbus packet from ring buffer.
413 *
414 * Advances the current location (priv_read_index) and checks for more
415 * data. If the end of the ring buffer is reached, then return NULL.
416 */
417struct vmpacket_descriptor *
418__hv_pkt_iter_next(struct vmbus_channel *channel,
419 const struct vmpacket_descriptor *desc)
420{
421 struct hv_ring_buffer_info *rbi = &channel->inbound;
422 u32 packetlen = desc->len8 << 3;
423 u32 dsize = rbi->ring_datasize;
424
425 hv_debug_delay_test(channel, MESSAGE_DELAY);
426 /* bump offset to next potential packet */
427 rbi->priv_read_index += packetlen + VMBUS_PKT_TRAILER;
428 if (rbi->priv_read_index >= dsize)
429 rbi->priv_read_index -= dsize;
430
431 /* more data? */
432 return hv_pkt_iter_first(channel);
433}
434EXPORT_SYMBOL_GPL(__hv_pkt_iter_next);
435
436/* How many bytes were read in this iterator cycle */
437static u32 hv_pkt_iter_bytes_read(const struct hv_ring_buffer_info *rbi,
438 u32 start_read_index)
439{
440 if (rbi->priv_read_index >= start_read_index)
441 return rbi->priv_read_index - start_read_index;
442 else
443 return rbi->ring_datasize - start_read_index +
444 rbi->priv_read_index;
445}
446
447/*
448 * Update host ring buffer after iterating over packets. If the host has
449 * stopped queuing new entries because it found the ring buffer full, and
450 * sufficient space is being freed up, signal the host. But be careful to
451 * only signal the host when necessary, both for performance reasons and
452 * because Hyper-V protects itself by throttling guests that signal
453 * inappropriately.
454 *
455 * Determining when to signal is tricky. There are three key data inputs
456 * that must be handled in this order to avoid race conditions:
457 *
458 * 1. Update the read_index
459 * 2. Read the pending_send_sz
460 * 3. Read the current write_index
461 *
462 * The interrupt_mask is not used to determine when to signal. The
463 * interrupt_mask is used only on the guest->host ring buffer when
464 * sending requests to the host. The host does not use it on the host->
465 * guest ring buffer to indicate whether it should be signaled.
466 */
467void hv_pkt_iter_close(struct vmbus_channel *channel)
468{
469 struct hv_ring_buffer_info *rbi = &channel->inbound;
470 u32 curr_write_sz, pending_sz, bytes_read, start_read_index;
471
472 /*
473 * Make sure all reads are done before we update the read index since
474 * the writer may start writing to the read area once the read index
475 * is updated.
476 */
477 virt_rmb();
478 start_read_index = rbi->ring_buffer->read_index;
479 rbi->ring_buffer->read_index = rbi->priv_read_index;
480
481 /*
482 * Older versions of Hyper-V (before WS2102 and Win8) do not
483 * implement pending_send_sz and simply poll if the host->guest
484 * ring buffer is full. No signaling is needed or expected.
485 */
486 if (!rbi->ring_buffer->feature_bits.feat_pending_send_sz)
487 return;
488
489 /*
490 * Issue a full memory barrier before making the signaling decision.
491 * If reading pending_send_sz were to be reordered and happen
492 * before we commit the new read_index, a race could occur. If the
493 * host were to set the pending_send_sz after we have sampled
494 * pending_send_sz, and the ring buffer blocks before we commit the
495 * read index, we could miss sending the interrupt. Issue a full
496 * memory barrier to address this.
497 */
498 virt_mb();
499
500 /*
501 * If the pending_send_sz is zero, then the ring buffer is not
502 * blocked and there is no need to signal. This is far by the
503 * most common case, so exit quickly for best performance.
504 */
505 pending_sz = READ_ONCE(rbi->ring_buffer->pending_send_sz);
506 if (!pending_sz)
507 return;
508
509 /*
510 * Ensure the read of write_index in hv_get_bytes_to_write()
511 * happens after the read of pending_send_sz.
512 */
513 virt_rmb();
514 curr_write_sz = hv_get_bytes_to_write(rbi);
515 bytes_read = hv_pkt_iter_bytes_read(rbi, start_read_index);
516
517 /*
518 * We want to signal the host only if we're transitioning
519 * from a "not enough free space" state to a "enough free
520 * space" state. For example, it's possible that this function
521 * could run and free up enough space to signal the host, and then
522 * run again and free up additional space before the host has a
523 * chance to clear the pending_send_sz. The 2nd invocation would
524 * be a null transition from "enough free space" to "enough free
525 * space", which doesn't warrant a signal.
526 *
527 * Exactly filling the ring buffer is treated as "not enough
528 * space". The ring buffer always must have at least one byte
529 * empty so the empty and full conditions are distinguishable.
530 * hv_get_bytes_to_write() doesn't fully tell the truth in
531 * this regard.
532 *
533 * So first check if we were in the "enough free space" state
534 * before we began the iteration. If so, the host was not
535 * blocked, and there's no need to signal.
536 */
537 if (curr_write_sz - bytes_read > pending_sz)
538 return;
539
540 /*
541 * Similarly, if the new state is "not enough space", then
542 * there's no need to signal.
543 */
544 if (curr_write_sz <= pending_sz)
545 return;
546
547 ++channel->intr_in_full;
548 vmbus_setevent(channel);
549}
550EXPORT_SYMBOL_GPL(hv_pkt_iter_close);