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