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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 | ||
33 | void hv_begin_read(struct hv_ring_buffer_info *rbi) | |
34 | { | |
35 | rbi->ring_buffer->interrupt_mask = 1; | |
36 | mb(); | |
37 | } | |
38 | ||
39 | u32 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 | ||
73 | static 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 | ||
106 | static bool hv_need_to_signal_on_read(u32 prev_write_sz, | |
107 | struct hv_ring_buffer_info *rbi) | |
108 | { | |
109 | u32 cur_write_sz; | |
110 | u32 r_size; | |
111 | u32 write_loc = rbi->ring_buffer->write_index; | |
112 | u32 read_loc = rbi->ring_buffer->read_index; | |
113 | u32 pending_sz = rbi->ring_buffer->pending_send_sz; | |
114 | ||
115 | /* If the other end is not blocked on write don't bother. */ | |
116 | if (pending_sz == 0) | |
117 | return false; | |
118 | ||
119 | r_size = rbi->ring_datasize; | |
120 | cur_write_sz = write_loc >= read_loc ? r_size - (write_loc - read_loc) : | |
121 | read_loc - write_loc; | |
122 | ||
123 | if ((prev_write_sz < pending_sz) && (cur_write_sz >= pending_sz)) | |
124 | return true; | |
125 | ||
126 | return false; | |
127 | } | |
128 | ||
129 | /* Get the next write location for the specified ring buffer. */ | |
130 | static inline u32 | |
131 | hv_get_next_write_location(struct hv_ring_buffer_info *ring_info) | |
132 | { | |
133 | u32 next = ring_info->ring_buffer->write_index; | |
134 | ||
135 | return next; | |
136 | } | |
137 | ||
138 | /* Set the next write location for the specified ring buffer. */ | |
139 | static inline void | |
140 | hv_set_next_write_location(struct hv_ring_buffer_info *ring_info, | |
141 | u32 next_write_location) | |
142 | { | |
143 | ring_info->ring_buffer->write_index = next_write_location; | |
144 | } | |
145 | ||
146 | /* Get the next read location for the specified ring buffer. */ | |
147 | static inline u32 | |
148 | hv_get_next_read_location(struct hv_ring_buffer_info *ring_info) | |
149 | { | |
150 | u32 next = ring_info->ring_buffer->read_index; | |
151 | ||
152 | return next; | |
153 | } | |
154 | ||
155 | /* | |
156 | * Get the next read location + offset for the specified ring buffer. | |
157 | * This allows the caller to skip. | |
158 | */ | |
159 | static inline u32 | |
160 | hv_get_next_readlocation_withoffset(struct hv_ring_buffer_info *ring_info, | |
161 | u32 offset) | |
162 | { | |
163 | u32 next = ring_info->ring_buffer->read_index; | |
164 | ||
165 | next += offset; | |
166 | next %= ring_info->ring_datasize; | |
167 | ||
168 | return next; | |
169 | } | |
170 | ||
171 | /* Set the next read location for the specified ring buffer. */ | |
172 | static inline void | |
173 | hv_set_next_read_location(struct hv_ring_buffer_info *ring_info, | |
174 | u32 next_read_location) | |
175 | { | |
176 | ring_info->ring_buffer->read_index = next_read_location; | |
177 | } | |
178 | ||
179 | ||
180 | /* Get the start of the ring buffer. */ | |
181 | static inline void * | |
182 | hv_get_ring_buffer(struct hv_ring_buffer_info *ring_info) | |
183 | { | |
184 | return (void *)ring_info->ring_buffer->buffer; | |
185 | } | |
186 | ||
187 | ||
188 | /* Get the size of the ring buffer. */ | |
189 | static inline u32 | |
190 | hv_get_ring_buffersize(struct hv_ring_buffer_info *ring_info) | |
191 | { | |
192 | return ring_info->ring_datasize; | |
193 | } | |
194 | ||
195 | /* Get the read and write indices as u64 of the specified ring buffer. */ | |
196 | static inline u64 | |
197 | hv_get_ring_bufferindices(struct hv_ring_buffer_info *ring_info) | |
198 | { | |
199 | return (u64)ring_info->ring_buffer->write_index << 32; | |
200 | } | |
201 | ||
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 | static u32 hv_copyfrom_ringbuffer( | |
207 | struct hv_ring_buffer_info *ring_info, | |
208 | void *dest, | |
209 | u32 destlen, | |
210 | u32 start_read_offset) | |
211 | { | |
212 | void *ring_buffer = hv_get_ring_buffer(ring_info); | |
213 | u32 ring_buffer_size = hv_get_ring_buffersize(ring_info); | |
214 | ||
215 | u32 frag_len; | |
216 | ||
217 | /* wrap-around detected at the src */ | |
218 | if (destlen > ring_buffer_size - start_read_offset) { | |
219 | frag_len = ring_buffer_size - start_read_offset; | |
220 | ||
221 | memcpy(dest, ring_buffer + start_read_offset, frag_len); | |
222 | memcpy(dest + frag_len, ring_buffer, destlen - frag_len); | |
223 | } else | |
224 | ||
225 | memcpy(dest, ring_buffer + start_read_offset, destlen); | |
226 | ||
227 | ||
228 | start_read_offset += destlen; | |
229 | start_read_offset %= ring_buffer_size; | |
230 | ||
231 | return start_read_offset; | |
232 | } | |
233 | ||
234 | ||
235 | /* | |
236 | * Helper routine to copy from source to ring buffer. | |
237 | * Assume there is enough room. Handles wrap-around in dest case only!! | |
238 | */ | |
239 | static u32 hv_copyto_ringbuffer( | |
240 | struct hv_ring_buffer_info *ring_info, | |
241 | u32 start_write_offset, | |
242 | void *src, | |
243 | u32 srclen) | |
244 | { | |
245 | void *ring_buffer = hv_get_ring_buffer(ring_info); | |
246 | u32 ring_buffer_size = hv_get_ring_buffersize(ring_info); | |
247 | u32 frag_len; | |
248 | ||
249 | /* wrap-around detected! */ | |
250 | if (srclen > ring_buffer_size - start_write_offset) { | |
251 | frag_len = ring_buffer_size - start_write_offset; | |
252 | memcpy(ring_buffer + start_write_offset, src, frag_len); | |
253 | memcpy(ring_buffer, src + frag_len, srclen - frag_len); | |
254 | } else | |
255 | memcpy(ring_buffer + start_write_offset, src, srclen); | |
256 | ||
257 | start_write_offset += srclen; | |
258 | start_write_offset %= ring_buffer_size; | |
259 | ||
260 | return start_write_offset; | |
261 | } | |
262 | ||
263 | /* Get various debug metrics for the specified ring buffer. */ | |
264 | void hv_ringbuffer_get_debuginfo(struct hv_ring_buffer_info *ring_info, | |
265 | struct hv_ring_buffer_debug_info *debug_info) | |
266 | { | |
267 | u32 bytes_avail_towrite; | |
268 | u32 bytes_avail_toread; | |
269 | ||
270 | if (ring_info->ring_buffer) { | |
271 | hv_get_ringbuffer_availbytes(ring_info, | |
272 | &bytes_avail_toread, | |
273 | &bytes_avail_towrite); | |
274 | ||
275 | debug_info->bytes_avail_toread = bytes_avail_toread; | |
276 | debug_info->bytes_avail_towrite = bytes_avail_towrite; | |
277 | debug_info->current_read_index = | |
278 | ring_info->ring_buffer->read_index; | |
279 | debug_info->current_write_index = | |
280 | ring_info->ring_buffer->write_index; | |
281 | debug_info->current_interrupt_mask = | |
282 | ring_info->ring_buffer->interrupt_mask; | |
283 | } | |
284 | } | |
285 | ||
286 | /* Initialize the ring buffer. */ | |
287 | int hv_ringbuffer_init(struct hv_ring_buffer_info *ring_info, | |
288 | void *buffer, u32 buflen) | |
289 | { | |
290 | if (sizeof(struct hv_ring_buffer) != PAGE_SIZE) | |
291 | return -EINVAL; | |
292 | ||
293 | memset(ring_info, 0, sizeof(struct hv_ring_buffer_info)); | |
294 | ||
295 | ring_info->ring_buffer = (struct hv_ring_buffer *)buffer; | |
296 | ring_info->ring_buffer->read_index = | |
297 | ring_info->ring_buffer->write_index = 0; | |
298 | ||
299 | /* Set the feature bit for enabling flow control. */ | |
300 | ring_info->ring_buffer->feature_bits.value = 1; | |
301 | ||
302 | ring_info->ring_size = buflen; | |
303 | ring_info->ring_datasize = buflen - sizeof(struct hv_ring_buffer); | |
304 | ||
305 | spin_lock_init(&ring_info->ring_lock); | |
306 | ||
307 | return 0; | |
308 | } | |
309 | ||
310 | /* Cleanup the ring buffer. */ | |
311 | void hv_ringbuffer_cleanup(struct hv_ring_buffer_info *ring_info) | |
312 | { | |
313 | } | |
314 | ||
315 | /* Write to the ring buffer. */ | |
316 | int hv_ringbuffer_write(struct hv_ring_buffer_info *outring_info, | |
317 | struct kvec *kv_list, u32 kv_count, bool *signal, bool lock) | |
318 | { | |
319 | int i = 0; | |
320 | u32 bytes_avail_towrite; | |
321 | u32 bytes_avail_toread; | |
322 | u32 totalbytes_towrite = 0; | |
323 | ||
324 | u32 next_write_location; | |
325 | u32 old_write; | |
326 | u64 prev_indices = 0; | |
327 | unsigned long flags = 0; | |
328 | ||
329 | for (i = 0; i < kv_count; i++) | |
330 | totalbytes_towrite += kv_list[i].iov_len; | |
331 | ||
332 | totalbytes_towrite += sizeof(u64); | |
333 | ||
334 | if (lock) | |
335 | spin_lock_irqsave(&outring_info->ring_lock, flags); | |
336 | ||
337 | hv_get_ringbuffer_availbytes(outring_info, | |
338 | &bytes_avail_toread, | |
339 | &bytes_avail_towrite); | |
340 | ||
341 | /* | |
342 | * If there is only room for the packet, assume it is full. | |
343 | * Otherwise, the next time around, we think the ring buffer | |
344 | * is empty since the read index == write index. | |
345 | */ | |
346 | if (bytes_avail_towrite <= totalbytes_towrite) { | |
347 | if (lock) | |
348 | spin_unlock_irqrestore(&outring_info->ring_lock, flags); | |
349 | return -EAGAIN; | |
350 | } | |
351 | ||
352 | /* Write to the ring buffer */ | |
353 | next_write_location = hv_get_next_write_location(outring_info); | |
354 | ||
355 | old_write = next_write_location; | |
356 | ||
357 | for (i = 0; i < kv_count; i++) { | |
358 | next_write_location = hv_copyto_ringbuffer(outring_info, | |
359 | next_write_location, | |
360 | kv_list[i].iov_base, | |
361 | kv_list[i].iov_len); | |
362 | } | |
363 | ||
364 | /* Set previous packet start */ | |
365 | prev_indices = hv_get_ring_bufferindices(outring_info); | |
366 | ||
367 | next_write_location = hv_copyto_ringbuffer(outring_info, | |
368 | next_write_location, | |
369 | &prev_indices, | |
370 | sizeof(u64)); | |
371 | ||
372 | /* Issue a full memory barrier before updating the write index */ | |
373 | mb(); | |
374 | ||
375 | /* Now, update the write location */ | |
376 | hv_set_next_write_location(outring_info, next_write_location); | |
377 | ||
378 | ||
379 | if (lock) | |
380 | spin_unlock_irqrestore(&outring_info->ring_lock, flags); | |
381 | ||
382 | *signal = hv_need_to_signal(old_write, outring_info); | |
383 | return 0; | |
384 | } | |
385 | ||
386 | int hv_ringbuffer_read(struct hv_ring_buffer_info *inring_info, | |
387 | void *buffer, u32 buflen, u32 *buffer_actual_len, | |
388 | u64 *requestid, bool *signal, bool raw) | |
389 | { | |
390 | u32 bytes_avail_towrite; | |
391 | u32 bytes_avail_toread; | |
392 | u32 next_read_location = 0; | |
393 | u64 prev_indices = 0; | |
394 | struct vmpacket_descriptor desc; | |
395 | u32 offset; | |
396 | u32 packetlen; | |
397 | int ret = 0; | |
398 | ||
399 | if (buflen <= 0) | |
400 | return -EINVAL; | |
401 | ||
402 | ||
403 | *buffer_actual_len = 0; | |
404 | *requestid = 0; | |
405 | ||
406 | hv_get_ringbuffer_availbytes(inring_info, | |
407 | &bytes_avail_toread, | |
408 | &bytes_avail_towrite); | |
409 | ||
410 | /* Make sure there is something to read */ | |
411 | if (bytes_avail_toread < sizeof(desc)) { | |
412 | /* | |
413 | * No error is set when there is even no header, drivers are | |
414 | * supposed to analyze buffer_actual_len. | |
415 | */ | |
416 | return ret; | |
417 | } | |
418 | ||
419 | next_read_location = hv_get_next_read_location(inring_info); | |
420 | next_read_location = hv_copyfrom_ringbuffer(inring_info, &desc, | |
421 | sizeof(desc), | |
422 | next_read_location); | |
423 | ||
424 | offset = raw ? 0 : (desc.offset8 << 3); | |
425 | packetlen = (desc.len8 << 3) - offset; | |
426 | *buffer_actual_len = packetlen; | |
427 | *requestid = desc.trans_id; | |
428 | ||
429 | if (bytes_avail_toread < packetlen + offset) | |
430 | return -EAGAIN; | |
431 | ||
432 | if (packetlen > buflen) | |
433 | return -ENOBUFS; | |
434 | ||
435 | next_read_location = | |
436 | hv_get_next_readlocation_withoffset(inring_info, offset); | |
437 | ||
438 | next_read_location = hv_copyfrom_ringbuffer(inring_info, | |
439 | buffer, | |
440 | packetlen, | |
441 | next_read_location); | |
442 | ||
443 | next_read_location = hv_copyfrom_ringbuffer(inring_info, | |
444 | &prev_indices, | |
445 | sizeof(u64), | |
446 | next_read_location); | |
447 | ||
448 | /* | |
449 | * Make sure all reads are done before we update the read index since | |
450 | * the writer may start writing to the read area once the read index | |
451 | * is updated. | |
452 | */ | |
453 | mb(); | |
454 | ||
455 | /* Update the read index */ | |
456 | hv_set_next_read_location(inring_info, next_read_location); | |
457 | ||
458 | *signal = hv_need_to_signal_on_read(bytes_avail_towrite, inring_info); | |
459 | ||
460 | return ret; | |
461 | } |