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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 | virt_mb(); | |
37 | } | |
38 | ||
39 | u32 hv_end_read(struct hv_ring_buffer_info *rbi) | |
40 | { | |
41 | ||
42 | rbi->ring_buffer->interrupt_mask = 0; | |
43 | virt_mb(); | |
44 | ||
45 | /* | |
46 | * Now check to see if the ring buffer is still empty. | |
47 | * If it is not, we raced and we need to process new | |
48 | * incoming messages. | |
49 | */ | |
50 | return hv_get_bytes_to_read(rbi); | |
51 | } | |
52 | ||
53 | /* | |
54 | * When we write to the ring buffer, check if the host needs to | |
55 | * be signaled. Here is the details of this protocol: | |
56 | * | |
57 | * 1. The host guarantees that while it is draining the | |
58 | * ring buffer, it will set the interrupt_mask to | |
59 | * indicate it does not need to be interrupted when | |
60 | * new data is placed. | |
61 | * | |
62 | * 2. The host guarantees that it will completely drain | |
63 | * the ring buffer before exiting the read loop. Further, | |
64 | * once the ring buffer is empty, it will clear the | |
65 | * interrupt_mask and re-check to see if new data has | |
66 | * arrived. | |
67 | */ | |
68 | ||
69 | static bool hv_need_to_signal(u32 old_write, struct hv_ring_buffer_info *rbi, | |
70 | enum hv_signal_policy policy) | |
71 | { | |
72 | virt_mb(); | |
73 | if (READ_ONCE(rbi->ring_buffer->interrupt_mask)) | |
74 | return false; | |
75 | ||
76 | /* | |
77 | * When the client wants to control signaling, | |
78 | * we only honour the host interrupt mask. | |
79 | */ | |
80 | if (policy == HV_SIGNAL_POLICY_EXPLICIT) | |
81 | return true; | |
82 | ||
83 | /* check interrupt_mask before read_index */ | |
84 | virt_rmb(); | |
85 | /* | |
86 | * This is the only case we need to signal when the | |
87 | * ring transitions from being empty to non-empty. | |
88 | */ | |
89 | if (old_write == READ_ONCE(rbi->ring_buffer->read_index)) | |
90 | return true; | |
91 | ||
92 | return false; | |
93 | } | |
94 | ||
95 | /* Get the next write location for the specified ring buffer. */ | |
96 | static inline u32 | |
97 | hv_get_next_write_location(struct hv_ring_buffer_info *ring_info) | |
98 | { | |
99 | u32 next = ring_info->ring_buffer->write_index; | |
100 | ||
101 | return next; | |
102 | } | |
103 | ||
104 | /* Set the next write location for the specified ring buffer. */ | |
105 | static inline void | |
106 | hv_set_next_write_location(struct hv_ring_buffer_info *ring_info, | |
107 | u32 next_write_location) | |
108 | { | |
109 | ring_info->ring_buffer->write_index = next_write_location; | |
110 | } | |
111 | ||
112 | /* Get the next read location for the specified ring buffer. */ | |
113 | static inline u32 | |
114 | hv_get_next_read_location(struct hv_ring_buffer_info *ring_info) | |
115 | { | |
116 | u32 next = ring_info->ring_buffer->read_index; | |
117 | ||
118 | return next; | |
119 | } | |
120 | ||
121 | /* | |
122 | * Get the next read location + offset for the specified ring buffer. | |
123 | * This allows the caller to skip. | |
124 | */ | |
125 | static inline u32 | |
126 | hv_get_next_readlocation_withoffset(struct hv_ring_buffer_info *ring_info, | |
127 | u32 offset) | |
128 | { | |
129 | u32 next = ring_info->ring_buffer->read_index; | |
130 | ||
131 | next += offset; | |
132 | next %= ring_info->ring_datasize; | |
133 | ||
134 | return next; | |
135 | } | |
136 | ||
137 | /* Set the next read location for the specified ring buffer. */ | |
138 | static inline void | |
139 | hv_set_next_read_location(struct hv_ring_buffer_info *ring_info, | |
140 | u32 next_read_location) | |
141 | { | |
142 | ring_info->ring_buffer->read_index = next_read_location; | |
143 | ring_info->priv_read_index = next_read_location; | |
144 | } | |
145 | ||
146 | /* Get the size of the ring buffer. */ | |
147 | static inline u32 | |
148 | hv_get_ring_buffersize(struct hv_ring_buffer_info *ring_info) | |
149 | { | |
150 | return ring_info->ring_datasize; | |
151 | } | |
152 | ||
153 | /* Get the read and write indices as u64 of the specified ring buffer. */ | |
154 | static inline u64 | |
155 | hv_get_ring_bufferindices(struct hv_ring_buffer_info *ring_info) | |
156 | { | |
157 | return (u64)ring_info->ring_buffer->write_index << 32; | |
158 | } | |
159 | ||
160 | /* | |
161 | * Helper routine to copy to source from ring buffer. | |
162 | * Assume there is enough room. Handles wrap-around in src case only!! | |
163 | */ | |
164 | static u32 hv_copyfrom_ringbuffer( | |
165 | struct hv_ring_buffer_info *ring_info, | |
166 | void *dest, | |
167 | u32 destlen, | |
168 | u32 start_read_offset) | |
169 | { | |
170 | void *ring_buffer = hv_get_ring_buffer(ring_info); | |
171 | u32 ring_buffer_size = hv_get_ring_buffersize(ring_info); | |
172 | ||
173 | u32 frag_len; | |
174 | ||
175 | /* wrap-around detected at the src */ | |
176 | if (destlen > ring_buffer_size - start_read_offset) { | |
177 | frag_len = ring_buffer_size - start_read_offset; | |
178 | ||
179 | memcpy(dest, ring_buffer + start_read_offset, frag_len); | |
180 | memcpy(dest + frag_len, ring_buffer, destlen - frag_len); | |
181 | } else | |
182 | ||
183 | memcpy(dest, ring_buffer + start_read_offset, destlen); | |
184 | ||
185 | ||
186 | start_read_offset += destlen; | |
187 | start_read_offset %= ring_buffer_size; | |
188 | ||
189 | return start_read_offset; | |
190 | } | |
191 | ||
192 | ||
193 | /* | |
194 | * Helper routine to copy from source to ring buffer. | |
195 | * Assume there is enough room. Handles wrap-around in dest case only!! | |
196 | */ | |
197 | static u32 hv_copyto_ringbuffer( | |
198 | struct hv_ring_buffer_info *ring_info, | |
199 | u32 start_write_offset, | |
200 | void *src, | |
201 | u32 srclen) | |
202 | { | |
203 | void *ring_buffer = hv_get_ring_buffer(ring_info); | |
204 | u32 ring_buffer_size = hv_get_ring_buffersize(ring_info); | |
205 | u32 frag_len; | |
206 | ||
207 | /* wrap-around detected! */ | |
208 | if (srclen > ring_buffer_size - start_write_offset) { | |
209 | frag_len = ring_buffer_size - start_write_offset; | |
210 | memcpy(ring_buffer + start_write_offset, src, frag_len); | |
211 | memcpy(ring_buffer, src + frag_len, srclen - frag_len); | |
212 | } else | |
213 | memcpy(ring_buffer + start_write_offset, src, srclen); | |
214 | ||
215 | start_write_offset += srclen; | |
216 | start_write_offset %= ring_buffer_size; | |
217 | ||
218 | return start_write_offset; | |
219 | } | |
220 | ||
221 | /* Get various debug metrics for the specified ring buffer. */ | |
222 | void hv_ringbuffer_get_debuginfo(struct hv_ring_buffer_info *ring_info, | |
223 | struct hv_ring_buffer_debug_info *debug_info) | |
224 | { | |
225 | u32 bytes_avail_towrite; | |
226 | u32 bytes_avail_toread; | |
227 | ||
228 | if (ring_info->ring_buffer) { | |
229 | hv_get_ringbuffer_availbytes(ring_info, | |
230 | &bytes_avail_toread, | |
231 | &bytes_avail_towrite); | |
232 | ||
233 | debug_info->bytes_avail_toread = bytes_avail_toread; | |
234 | debug_info->bytes_avail_towrite = bytes_avail_towrite; | |
235 | debug_info->current_read_index = | |
236 | ring_info->ring_buffer->read_index; | |
237 | debug_info->current_write_index = | |
238 | ring_info->ring_buffer->write_index; | |
239 | debug_info->current_interrupt_mask = | |
240 | ring_info->ring_buffer->interrupt_mask; | |
241 | } | |
242 | } | |
243 | ||
244 | /* Initialize the ring buffer. */ | |
245 | int hv_ringbuffer_init(struct hv_ring_buffer_info *ring_info, | |
246 | void *buffer, u32 buflen) | |
247 | { | |
248 | if (sizeof(struct hv_ring_buffer) != PAGE_SIZE) | |
249 | return -EINVAL; | |
250 | ||
251 | memset(ring_info, 0, sizeof(struct hv_ring_buffer_info)); | |
252 | ||
253 | ring_info->ring_buffer = (struct hv_ring_buffer *)buffer; | |
254 | ring_info->ring_buffer->read_index = | |
255 | ring_info->ring_buffer->write_index = 0; | |
256 | ||
257 | /* Set the feature bit for enabling flow control. */ | |
258 | ring_info->ring_buffer->feature_bits.value = 1; | |
259 | ||
260 | ring_info->ring_size = buflen; | |
261 | ring_info->ring_datasize = buflen - sizeof(struct hv_ring_buffer); | |
262 | ||
263 | spin_lock_init(&ring_info->ring_lock); | |
264 | ||
265 | return 0; | |
266 | } | |
267 | ||
268 | /* Cleanup the ring buffer. */ | |
269 | void hv_ringbuffer_cleanup(struct hv_ring_buffer_info *ring_info) | |
270 | { | |
271 | } | |
272 | ||
273 | /* Write to the ring buffer. */ | |
274 | int hv_ringbuffer_write(struct hv_ring_buffer_info *outring_info, | |
275 | struct kvec *kv_list, u32 kv_count, bool *signal, bool lock, | |
276 | enum hv_signal_policy policy) | |
277 | { | |
278 | int i = 0; | |
279 | u32 bytes_avail_towrite; | |
280 | u32 totalbytes_towrite = 0; | |
281 | ||
282 | u32 next_write_location; | |
283 | u32 old_write; | |
284 | u64 prev_indices = 0; | |
285 | unsigned long flags = 0; | |
286 | ||
287 | for (i = 0; i < kv_count; i++) | |
288 | totalbytes_towrite += kv_list[i].iov_len; | |
289 | ||
290 | totalbytes_towrite += sizeof(u64); | |
291 | ||
292 | if (lock) | |
293 | spin_lock_irqsave(&outring_info->ring_lock, flags); | |
294 | ||
295 | bytes_avail_towrite = hv_get_bytes_to_write(outring_info); | |
296 | ||
297 | /* | |
298 | * If there is only room for the packet, assume it is full. | |
299 | * Otherwise, the next time around, we think the ring buffer | |
300 | * is empty since the read index == write index. | |
301 | */ | |
302 | if (bytes_avail_towrite <= totalbytes_towrite) { | |
303 | if (lock) | |
304 | spin_unlock_irqrestore(&outring_info->ring_lock, flags); | |
305 | return -EAGAIN; | |
306 | } | |
307 | ||
308 | /* Write to the ring buffer */ | |
309 | next_write_location = hv_get_next_write_location(outring_info); | |
310 | ||
311 | old_write = next_write_location; | |
312 | ||
313 | for (i = 0; i < kv_count; i++) { | |
314 | next_write_location = hv_copyto_ringbuffer(outring_info, | |
315 | next_write_location, | |
316 | kv_list[i].iov_base, | |
317 | kv_list[i].iov_len); | |
318 | } | |
319 | ||
320 | /* Set previous packet start */ | |
321 | prev_indices = hv_get_ring_bufferindices(outring_info); | |
322 | ||
323 | next_write_location = hv_copyto_ringbuffer(outring_info, | |
324 | next_write_location, | |
325 | &prev_indices, | |
326 | sizeof(u64)); | |
327 | ||
328 | /* Issue a full memory barrier before updating the write index */ | |
329 | virt_mb(); | |
330 | ||
331 | /* Now, update the write location */ | |
332 | hv_set_next_write_location(outring_info, next_write_location); | |
333 | ||
334 | ||
335 | if (lock) | |
336 | spin_unlock_irqrestore(&outring_info->ring_lock, flags); | |
337 | ||
338 | *signal = hv_need_to_signal(old_write, outring_info, policy); | |
339 | return 0; | |
340 | } | |
341 | ||
342 | int hv_ringbuffer_read(struct hv_ring_buffer_info *inring_info, | |
343 | void *buffer, u32 buflen, u32 *buffer_actual_len, | |
344 | u64 *requestid, bool *signal, bool raw) | |
345 | { | |
346 | u32 bytes_avail_toread; | |
347 | u32 next_read_location = 0; | |
348 | u64 prev_indices = 0; | |
349 | struct vmpacket_descriptor desc; | |
350 | u32 offset; | |
351 | u32 packetlen; | |
352 | int ret = 0; | |
353 | ||
354 | if (buflen <= 0) | |
355 | return -EINVAL; | |
356 | ||
357 | ||
358 | *buffer_actual_len = 0; | |
359 | *requestid = 0; | |
360 | ||
361 | bytes_avail_toread = hv_get_bytes_to_read(inring_info); | |
362 | /* Make sure there is something to read */ | |
363 | if (bytes_avail_toread < sizeof(desc)) { | |
364 | /* | |
365 | * No error is set when there is even no header, drivers are | |
366 | * supposed to analyze buffer_actual_len. | |
367 | */ | |
368 | return ret; | |
369 | } | |
370 | ||
371 | next_read_location = hv_get_next_read_location(inring_info); | |
372 | next_read_location = hv_copyfrom_ringbuffer(inring_info, &desc, | |
373 | sizeof(desc), | |
374 | next_read_location); | |
375 | ||
376 | offset = raw ? 0 : (desc.offset8 << 3); | |
377 | packetlen = (desc.len8 << 3) - offset; | |
378 | *buffer_actual_len = packetlen; | |
379 | *requestid = desc.trans_id; | |
380 | ||
381 | if (bytes_avail_toread < packetlen + offset) | |
382 | return -EAGAIN; | |
383 | ||
384 | if (packetlen > buflen) | |
385 | return -ENOBUFS; | |
386 | ||
387 | next_read_location = | |
388 | hv_get_next_readlocation_withoffset(inring_info, offset); | |
389 | ||
390 | next_read_location = hv_copyfrom_ringbuffer(inring_info, | |
391 | buffer, | |
392 | packetlen, | |
393 | next_read_location); | |
394 | ||
395 | next_read_location = hv_copyfrom_ringbuffer(inring_info, | |
396 | &prev_indices, | |
397 | sizeof(u64), | |
398 | next_read_location); | |
399 | ||
400 | /* | |
401 | * Make sure all reads are done before we update the read index since | |
402 | * the writer may start writing to the read area once the read index | |
403 | * is updated. | |
404 | */ | |
405 | virt_mb(); | |
406 | ||
407 | /* Update the read index */ | |
408 | hv_set_next_read_location(inring_info, next_read_location); | |
409 | ||
410 | *signal = hv_need_to_signal_on_read(inring_info); | |
411 | ||
412 | return ret; | |
413 | } |