Drivers: hv: Get rid of unnecessary request for offers
[linux-3.10.git] / drivers / hv / ring_buffer.c
1 /*
2  *
3  * Copyright (c) 2009, Microsoft Corporation.
4  *
5  * This program is free software; you can redistribute it and/or modify it
6  * under the terms and conditions of the GNU General Public License,
7  * version 2, as published by the Free Software Foundation.
8  *
9  * This program is distributed in the hope it will be useful, but WITHOUT
10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
12  * more details.
13  *
14  * You should have received a copy of the GNU General Public License along with
15  * this program; if not, write to the Free Software Foundation, Inc., 59 Temple
16  * Place - Suite 330, Boston, MA 02111-1307 USA.
17  *
18  * Authors:
19  *   Haiyang Zhang <haiyangz@microsoft.com>
20  *   Hank Janssen  <hjanssen@microsoft.com>
21  *   K. Y. Srinivasan <kys@microsoft.com>
22  *
23  */
24 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
25
26 #include <linux/kernel.h>
27 #include <linux/mm.h>
28 #include <linux/hyperv.h>
29
30 #include "hyperv_vmbus.h"
31
32 void hv_begin_read(struct hv_ring_buffer_info *rbi)
33 {
34         rbi->ring_buffer->interrupt_mask = 1;
35         smp_mb();
36 }
37
38 u32 hv_end_read(struct hv_ring_buffer_info *rbi)
39 {
40         u32 read;
41         u32 write;
42
43         rbi->ring_buffer->interrupt_mask = 0;
44         smp_mb();
45
46         /*
47          * Now check to see if the ring buffer is still empty.
48          * If it is not, we raced and we need to process new
49          * incoming messages.
50          */
51         hv_get_ringbuffer_availbytes(rbi, &read, &write);
52
53         return read;
54 }
55
56 /*
57  * When we write to the ring buffer, check if the host needs to
58  * be signaled. Here is the details of this protocol:
59  *
60  *      1. The host guarantees that while it is draining the
61  *         ring buffer, it will set the interrupt_mask to
62  *         indicate it does not need to be interrupted when
63  *         new data is placed.
64  *
65  *      2. The host guarantees that it will completely drain
66  *         the ring buffer before exiting the read loop. Further,
67  *         once the ring buffer is empty, it will clear the
68  *         interrupt_mask and re-check to see if new data has
69  *         arrived.
70  */
71
72 static bool hv_need_to_signal(u32 old_write, struct hv_ring_buffer_info *rbi)
73 {
74         if (rbi->ring_buffer->interrupt_mask)
75                 return false;
76
77         /*
78          * This is the only case we need to signal when the
79          * ring transitions from being empty to non-empty.
80          */
81         if (old_write == rbi->ring_buffer->read_index)
82                 return true;
83
84         return false;
85 }
86
87
88 /*
89  * hv_get_next_write_location()
90  *
91  * Get the next write location for the specified ring buffer
92  *
93  */
94 static inline u32
95 hv_get_next_write_location(struct hv_ring_buffer_info *ring_info)
96 {
97         u32 next = ring_info->ring_buffer->write_index;
98
99         return next;
100 }
101
102 /*
103  * hv_set_next_write_location()
104  *
105  * Set the next write location for the specified ring buffer
106  *
107  */
108 static inline void
109 hv_set_next_write_location(struct hv_ring_buffer_info *ring_info,
110                      u32 next_write_location)
111 {
112         ring_info->ring_buffer->write_index = next_write_location;
113 }
114
115 /*
116  * hv_get_next_read_location()
117  *
118  * Get the next read location for the specified ring buffer
119  */
120 static inline u32
121 hv_get_next_read_location(struct hv_ring_buffer_info *ring_info)
122 {
123         u32 next = ring_info->ring_buffer->read_index;
124
125         return next;
126 }
127
128 /*
129  * hv_get_next_readlocation_withoffset()
130  *
131  * Get the next read location + offset for the specified ring buffer.
132  * This allows the caller to skip
133  */
134 static inline u32
135 hv_get_next_readlocation_withoffset(struct hv_ring_buffer_info *ring_info,
136                                  u32 offset)
137 {
138         u32 next = ring_info->ring_buffer->read_index;
139
140         next += offset;
141         next %= ring_info->ring_datasize;
142
143         return next;
144 }
145
146 /*
147  *
148  * hv_set_next_read_location()
149  *
150  * Set the next read location for the specified ring buffer
151  *
152  */
153 static inline void
154 hv_set_next_read_location(struct hv_ring_buffer_info *ring_info,
155                     u32 next_read_location)
156 {
157         ring_info->ring_buffer->read_index = next_read_location;
158 }
159
160
161 /*
162  *
163  * hv_get_ring_buffer()
164  *
165  * Get the start of the ring buffer
166  */
167 static inline void *
168 hv_get_ring_buffer(struct hv_ring_buffer_info *ring_info)
169 {
170         return (void *)ring_info->ring_buffer->buffer;
171 }
172
173
174 /*
175  *
176  * hv_get_ring_buffersize()
177  *
178  * Get the size of the ring buffer
179  */
180 static inline u32
181 hv_get_ring_buffersize(struct hv_ring_buffer_info *ring_info)
182 {
183         return ring_info->ring_datasize;
184 }
185
186 /*
187  *
188  * hv_get_ring_bufferindices()
189  *
190  * Get the read and write indices as u64 of the specified ring buffer
191  *
192  */
193 static inline u64
194 hv_get_ring_bufferindices(struct hv_ring_buffer_info *ring_info)
195 {
196         return (u64)ring_info->ring_buffer->write_index << 32;
197 }
198
199 /*
200  *
201  * hv_copyfrom_ringbuffer()
202  *
203  * Helper routine to copy to source from ring buffer.
204  * Assume there is enough room. Handles wrap-around in src case only!!
205  *
206  */
207 static u32 hv_copyfrom_ringbuffer(
208         struct hv_ring_buffer_info      *ring_info,
209         void                            *dest,
210         u32                             destlen,
211         u32                             start_read_offset)
212 {
213         void *ring_buffer = hv_get_ring_buffer(ring_info);
214         u32 ring_buffer_size = hv_get_ring_buffersize(ring_info);
215
216         u32 frag_len;
217
218         /* wrap-around detected at the src */
219         if (destlen > ring_buffer_size - start_read_offset) {
220                 frag_len = ring_buffer_size - start_read_offset;
221
222                 memcpy(dest, ring_buffer + start_read_offset, frag_len);
223                 memcpy(dest + frag_len, ring_buffer, destlen - frag_len);
224         } else
225
226                 memcpy(dest, ring_buffer + start_read_offset, destlen);
227
228
229         start_read_offset += destlen;
230         start_read_offset %= ring_buffer_size;
231
232         return start_read_offset;
233 }
234
235
236 /*
237  *
238  * hv_copyto_ringbuffer()
239  *
240  * Helper routine to copy from source to ring buffer.
241  * Assume there is enough room. Handles wrap-around in dest case only!!
242  *
243  */
244 static u32 hv_copyto_ringbuffer(
245         struct hv_ring_buffer_info      *ring_info,
246         u32                             start_write_offset,
247         void                            *src,
248         u32                             srclen)
249 {
250         void *ring_buffer = hv_get_ring_buffer(ring_info);
251         u32 ring_buffer_size = hv_get_ring_buffersize(ring_info);
252         u32 frag_len;
253
254         /* wrap-around detected! */
255         if (srclen > ring_buffer_size - start_write_offset) {
256                 frag_len = ring_buffer_size - start_write_offset;
257                 memcpy(ring_buffer + start_write_offset, src, frag_len);
258                 memcpy(ring_buffer, src + frag_len, srclen - frag_len);
259         } else
260                 memcpy(ring_buffer + start_write_offset, src, srclen);
261
262         start_write_offset += srclen;
263         start_write_offset %= ring_buffer_size;
264
265         return start_write_offset;
266 }
267
268 /*
269  *
270  * hv_ringbuffer_get_debuginfo()
271  *
272  * Get various debug metrics for the specified ring buffer
273  *
274  */
275 void hv_ringbuffer_get_debuginfo(struct hv_ring_buffer_info *ring_info,
276                             struct hv_ring_buffer_debug_info *debug_info)
277 {
278         u32 bytes_avail_towrite;
279         u32 bytes_avail_toread;
280
281         if (ring_info->ring_buffer) {
282                 hv_get_ringbuffer_availbytes(ring_info,
283                                         &bytes_avail_toread,
284                                         &bytes_avail_towrite);
285
286                 debug_info->bytes_avail_toread = bytes_avail_toread;
287                 debug_info->bytes_avail_towrite = bytes_avail_towrite;
288                 debug_info->current_read_index =
289                         ring_info->ring_buffer->read_index;
290                 debug_info->current_write_index =
291                         ring_info->ring_buffer->write_index;
292                 debug_info->current_interrupt_mask =
293                         ring_info->ring_buffer->interrupt_mask;
294         }
295 }
296
297 /*
298  *
299  * hv_ringbuffer_init()
300  *
301  *Initialize the ring buffer
302  *
303  */
304 int hv_ringbuffer_init(struct hv_ring_buffer_info *ring_info,
305                    void *buffer, u32 buflen)
306 {
307         if (sizeof(struct hv_ring_buffer) != PAGE_SIZE)
308                 return -EINVAL;
309
310         memset(ring_info, 0, sizeof(struct hv_ring_buffer_info));
311
312         ring_info->ring_buffer = (struct hv_ring_buffer *)buffer;
313         ring_info->ring_buffer->read_index =
314                 ring_info->ring_buffer->write_index = 0;
315
316         ring_info->ring_size = buflen;
317         ring_info->ring_datasize = buflen - sizeof(struct hv_ring_buffer);
318
319         spin_lock_init(&ring_info->ring_lock);
320
321         return 0;
322 }
323
324 /*
325  *
326  * hv_ringbuffer_cleanup()
327  *
328  * Cleanup the ring buffer
329  *
330  */
331 void hv_ringbuffer_cleanup(struct hv_ring_buffer_info *ring_info)
332 {
333 }
334
335 /*
336  *
337  * hv_ringbuffer_write()
338  *
339  * Write to the ring buffer
340  *
341  */
342 int hv_ringbuffer_write(struct hv_ring_buffer_info *outring_info,
343                     struct scatterlist *sglist, u32 sgcount, bool *signal)
344 {
345         int i = 0;
346         u32 bytes_avail_towrite;
347         u32 bytes_avail_toread;
348         u32 totalbytes_towrite = 0;
349
350         struct scatterlist *sg;
351         u32 next_write_location;
352         u32 old_write;
353         u64 prev_indices = 0;
354         unsigned long flags;
355
356         for_each_sg(sglist, sg, sgcount, i)
357         {
358                 totalbytes_towrite += sg->length;
359         }
360
361         totalbytes_towrite += sizeof(u64);
362
363         spin_lock_irqsave(&outring_info->ring_lock, flags);
364
365         hv_get_ringbuffer_availbytes(outring_info,
366                                 &bytes_avail_toread,
367                                 &bytes_avail_towrite);
368
369
370         /* If there is only room for the packet, assume it is full. */
371         /* Otherwise, the next time around, we think the ring buffer */
372         /* is empty since the read index == write index */
373         if (bytes_avail_towrite <= totalbytes_towrite) {
374                 spin_unlock_irqrestore(&outring_info->ring_lock, flags);
375                 return -EAGAIN;
376         }
377
378         /* Write to the ring buffer */
379         next_write_location = hv_get_next_write_location(outring_info);
380
381         old_write = next_write_location;
382
383         for_each_sg(sglist, sg, sgcount, i)
384         {
385                 next_write_location = hv_copyto_ringbuffer(outring_info,
386                                                      next_write_location,
387                                                      sg_virt(sg),
388                                                      sg->length);
389         }
390
391         /* Set previous packet start */
392         prev_indices = hv_get_ring_bufferindices(outring_info);
393
394         next_write_location = hv_copyto_ringbuffer(outring_info,
395                                              next_write_location,
396                                              &prev_indices,
397                                              sizeof(u64));
398
399         /* Issue a full memory barrier before updating the write index */
400         smp_mb();
401
402         /* Now, update the write location */
403         hv_set_next_write_location(outring_info, next_write_location);
404
405
406         spin_unlock_irqrestore(&outring_info->ring_lock, flags);
407
408         *signal = hv_need_to_signal(old_write, outring_info);
409         return 0;
410 }
411
412
413 /*
414  *
415  * hv_ringbuffer_peek()
416  *
417  * Read without advancing the read index
418  *
419  */
420 int hv_ringbuffer_peek(struct hv_ring_buffer_info *Inring_info,
421                    void *Buffer, u32 buflen)
422 {
423         u32 bytes_avail_towrite;
424         u32 bytes_avail_toread;
425         u32 next_read_location = 0;
426         unsigned long flags;
427
428         spin_lock_irqsave(&Inring_info->ring_lock, flags);
429
430         hv_get_ringbuffer_availbytes(Inring_info,
431                                 &bytes_avail_toread,
432                                 &bytes_avail_towrite);
433
434         /* Make sure there is something to read */
435         if (bytes_avail_toread < buflen) {
436
437                 spin_unlock_irqrestore(&Inring_info->ring_lock, flags);
438
439                 return -EAGAIN;
440         }
441
442         /* Convert to byte offset */
443         next_read_location = hv_get_next_read_location(Inring_info);
444
445         next_read_location = hv_copyfrom_ringbuffer(Inring_info,
446                                                 Buffer,
447                                                 buflen,
448                                                 next_read_location);
449
450         spin_unlock_irqrestore(&Inring_info->ring_lock, flags);
451
452         return 0;
453 }
454
455
456 /*
457  *
458  * hv_ringbuffer_read()
459  *
460  * Read and advance the read index
461  *
462  */
463 int hv_ringbuffer_read(struct hv_ring_buffer_info *inring_info, void *buffer,
464                    u32 buflen, u32 offset)
465 {
466         u32 bytes_avail_towrite;
467         u32 bytes_avail_toread;
468         u32 next_read_location = 0;
469         u64 prev_indices = 0;
470         unsigned long flags;
471
472         if (buflen <= 0)
473                 return -EINVAL;
474
475         spin_lock_irqsave(&inring_info->ring_lock, flags);
476
477         hv_get_ringbuffer_availbytes(inring_info,
478                                 &bytes_avail_toread,
479                                 &bytes_avail_towrite);
480
481         /* Make sure there is something to read */
482         if (bytes_avail_toread < buflen) {
483                 spin_unlock_irqrestore(&inring_info->ring_lock, flags);
484
485                 return -EAGAIN;
486         }
487
488         next_read_location =
489                 hv_get_next_readlocation_withoffset(inring_info, offset);
490
491         next_read_location = hv_copyfrom_ringbuffer(inring_info,
492                                                 buffer,
493                                                 buflen,
494                                                 next_read_location);
495
496         next_read_location = hv_copyfrom_ringbuffer(inring_info,
497                                                 &prev_indices,
498                                                 sizeof(u64),
499                                                 next_read_location);
500
501         /* Make sure all reads are done before we update the read index since */
502         /* the writer may start writing to the read area once the read index */
503         /*is updated */
504         smp_mb();
505
506         /* Update the read index */
507         hv_set_next_read_location(inring_info, next_read_location);
508
509         spin_unlock_irqrestore(&inring_info->ring_lock, flags);
510
511         return 0;
512 }