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3e7ee490 HJ |
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> | |
b2a5a585 | 21 | * K. Y. Srinivasan <kys@microsoft.com> |
3e7ee490 HJ |
22 | * |
23 | */ | |
0a46618d | 24 | #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt |
3e7ee490 | 25 | |
a0086dc5 GKH |
26 | #include <linux/kernel.h> |
27 | #include <linux/mm.h> | |
46a97191 | 28 | #include <linux/hyperv.h> |
011a7c3c | 29 | #include <linux/uio.h> |
9988ce68 VK |
30 | #include <linux/vmalloc.h> |
31 | #include <linux/slab.h> | |
3f335ea2 | 32 | |
0f2a6619 | 33 | #include "hyperv_vmbus.h" |
3e7ee490 | 34 | |
f3dd3f47 | 35 | #define VMBUS_PKT_TRAILER 8 |
36 | ||
98fa8cf4 S |
37 | /* |
38 | * When we write to the ring buffer, check if the host needs to | |
39 | * be signaled. Here is the details of this protocol: | |
40 | * | |
41 | * 1. The host guarantees that while it is draining the | |
42 | * ring buffer, it will set the interrupt_mask to | |
43 | * indicate it does not need to be interrupted when | |
44 | * new data is placed. | |
45 | * | |
46 | * 2. The host guarantees that it will completely drain | |
47 | * the ring buffer before exiting the read loop. Further, | |
48 | * once the ring buffer is empty, it will clear the | |
49 | * interrupt_mask and re-check to see if new data has | |
50 | * arrived. | |
1f6ee4e7 S |
51 | * |
52 | * KYS: Oct. 30, 2016: | |
53 | * It looks like Windows hosts have logic to deal with DOS attacks that | |
54 | * can be triggered if it receives interrupts when it is not expecting | |
55 | * the interrupt. The host expects interrupts only when the ring | |
56 | * transitions from empty to non-empty (or full to non full on the guest | |
57 | * to host ring). | |
58 | * So, base the signaling decision solely on the ring state until the | |
59 | * host logic is fixed. | |
98fa8cf4 S |
60 | */ |
61 | ||
b103a56f | 62 | static void hv_signal_on_write(u32 old_write, struct vmbus_channel *channel) |
98fa8cf4 | 63 | { |
1f6ee4e7 S |
64 | struct hv_ring_buffer_info *rbi = &channel->outbound; |
65 | ||
dcd0eeca | 66 | virt_mb(); |
d45faaee | 67 | if (READ_ONCE(rbi->ring_buffer->interrupt_mask)) |
1f6ee4e7 | 68 | return; |
98fa8cf4 | 69 | |
e91e84fa | 70 | /* check interrupt_mask before read_index */ |
dcd0eeca | 71 | virt_rmb(); |
98fa8cf4 S |
72 | /* |
73 | * This is the only case we need to signal when the | |
74 | * ring transitions from being empty to non-empty. | |
75 | */ | |
d45faaee | 76 | if (old_write == READ_ONCE(rbi->ring_buffer->read_index)) |
1f6ee4e7 | 77 | vmbus_setevent(channel); |
98fa8cf4 | 78 | |
1f6ee4e7 | 79 | return; |
98fa8cf4 S |
80 | } |
81 | ||
822f18d4 | 82 | /* Get the next write location for the specified ring buffer. */ |
4d643114 | 83 | static inline u32 |
2b8a912e | 84 | hv_get_next_write_location(struct hv_ring_buffer_info *ring_info) |
3e7ee490 | 85 | { |
fc8c72eb | 86 | u32 next = ring_info->ring_buffer->write_index; |
3e7ee490 | 87 | |
3e7ee490 HJ |
88 | return next; |
89 | } | |
90 | ||
822f18d4 | 91 | /* Set the next write location for the specified ring buffer. */ |
3e7ee490 | 92 | static inline void |
2b8a912e | 93 | hv_set_next_write_location(struct hv_ring_buffer_info *ring_info, |
fc8c72eb | 94 | u32 next_write_location) |
3e7ee490 | 95 | { |
fc8c72eb | 96 | ring_info->ring_buffer->write_index = next_write_location; |
3e7ee490 HJ |
97 | } |
98 | ||
822f18d4 | 99 | /* Get the next read location for the specified ring buffer. */ |
4d643114 | 100 | static inline u32 |
e4165a0f | 101 | hv_get_next_read_location(const struct hv_ring_buffer_info *ring_info) |
3e7ee490 | 102 | { |
e4165a0f | 103 | return ring_info->ring_buffer->read_index; |
3e7ee490 HJ |
104 | } |
105 | ||
b2a5a585 | 106 | /* |
b2a5a585 | 107 | * Get the next read location + offset for the specified ring buffer. |
822f18d4 | 108 | * This allows the caller to skip. |
b2a5a585 | 109 | */ |
4d643114 | 110 | static inline u32 |
e4165a0f SH |
111 | hv_get_next_readlocation_withoffset(const struct hv_ring_buffer_info *ring_info, |
112 | u32 offset) | |
3e7ee490 | 113 | { |
fc8c72eb | 114 | u32 next = ring_info->ring_buffer->read_index; |
3e7ee490 | 115 | |
fc8c72eb | 116 | next += offset; |
8d12f882 SH |
117 | if (next >= ring_info->ring_datasize) |
118 | next -= ring_info->ring_datasize; | |
3e7ee490 HJ |
119 | |
120 | return next; | |
121 | } | |
122 | ||
822f18d4 | 123 | /* Set the next read location for the specified ring buffer. */ |
3e7ee490 | 124 | static inline void |
2b8a912e | 125 | hv_set_next_read_location(struct hv_ring_buffer_info *ring_info, |
fc8c72eb | 126 | u32 next_read_location) |
3e7ee490 | 127 | { |
fc8c72eb | 128 | ring_info->ring_buffer->read_index = next_read_location; |
ab028db4 | 129 | ring_info->priv_read_index = next_read_location; |
3e7ee490 HJ |
130 | } |
131 | ||
822f18d4 | 132 | /* Get the size of the ring buffer. */ |
4d643114 | 133 | static inline u32 |
e4165a0f | 134 | hv_get_ring_buffersize(const struct hv_ring_buffer_info *ring_info) |
3e7ee490 | 135 | { |
fc8c72eb | 136 | return ring_info->ring_datasize; |
3e7ee490 HJ |
137 | } |
138 | ||
822f18d4 | 139 | /* Get the read and write indices as u64 of the specified ring buffer. */ |
59471438 | 140 | static inline u64 |
2b8a912e | 141 | hv_get_ring_bufferindices(struct hv_ring_buffer_info *ring_info) |
3e7ee490 | 142 | { |
fc8c72eb | 143 | return (u64)ring_info->ring_buffer->write_index << 32; |
3e7ee490 HJ |
144 | } |
145 | ||
8f1136ae | 146 | /* |
8f1136ae S |
147 | * Helper routine to copy to source from ring buffer. |
148 | * Assume there is enough room. Handles wrap-around in src case only!! | |
8f1136ae S |
149 | */ |
150 | static u32 hv_copyfrom_ringbuffer( | |
e4165a0f | 151 | const struct hv_ring_buffer_info *ring_info, |
8f1136ae S |
152 | void *dest, |
153 | u32 destlen, | |
154 | u32 start_read_offset) | |
155 | { | |
156 | void *ring_buffer = hv_get_ring_buffer(ring_info); | |
157 | u32 ring_buffer_size = hv_get_ring_buffersize(ring_info); | |
158 | ||
f24f0b49 | 159 | memcpy(dest, ring_buffer + start_read_offset, destlen); |
8f1136ae S |
160 | |
161 | start_read_offset += destlen; | |
8d12f882 SH |
162 | if (start_read_offset >= ring_buffer_size) |
163 | start_read_offset -= ring_buffer_size; | |
8f1136ae S |
164 | |
165 | return start_read_offset; | |
166 | } | |
167 | ||
168 | ||
7581578d | 169 | /* |
7581578d S |
170 | * Helper routine to copy from source to ring buffer. |
171 | * Assume there is enough room. Handles wrap-around in dest case only!! | |
7581578d S |
172 | */ |
173 | static u32 hv_copyto_ringbuffer( | |
fc8c72eb HZ |
174 | struct hv_ring_buffer_info *ring_info, |
175 | u32 start_write_offset, | |
e4165a0f | 176 | const void *src, |
7581578d S |
177 | u32 srclen) |
178 | { | |
179 | void *ring_buffer = hv_get_ring_buffer(ring_info); | |
180 | u32 ring_buffer_size = hv_get_ring_buffersize(ring_info); | |
f24f0b49 VK |
181 | |
182 | memcpy(ring_buffer + start_write_offset, src, srclen); | |
3e7ee490 | 183 | |
7581578d | 184 | start_write_offset += srclen; |
8d12f882 SH |
185 | if (start_write_offset >= ring_buffer_size) |
186 | start_write_offset -= ring_buffer_size; | |
7581578d S |
187 | |
188 | return start_write_offset; | |
189 | } | |
3e7ee490 | 190 | |
822f18d4 | 191 | /* Get various debug metrics for the specified ring buffer. */ |
e4165a0f SH |
192 | void hv_ringbuffer_get_debuginfo(const struct hv_ring_buffer_info *ring_info, |
193 | struct hv_ring_buffer_debug_info *debug_info) | |
3e7ee490 | 194 | { |
fc8c72eb HZ |
195 | u32 bytes_avail_towrite; |
196 | u32 bytes_avail_toread; | |
3e7ee490 | 197 | |
fc8c72eb | 198 | if (ring_info->ring_buffer) { |
2b8a912e | 199 | hv_get_ringbuffer_availbytes(ring_info, |
fc8c72eb HZ |
200 | &bytes_avail_toread, |
201 | &bytes_avail_towrite); | |
3e7ee490 | 202 | |
fc8c72eb HZ |
203 | debug_info->bytes_avail_toread = bytes_avail_toread; |
204 | debug_info->bytes_avail_towrite = bytes_avail_towrite; | |
82f8bd40 | 205 | debug_info->current_read_index = |
fc8c72eb | 206 | ring_info->ring_buffer->read_index; |
82f8bd40 | 207 | debug_info->current_write_index = |
fc8c72eb | 208 | ring_info->ring_buffer->write_index; |
82f8bd40 | 209 | debug_info->current_interrupt_mask = |
fc8c72eb | 210 | ring_info->ring_buffer->interrupt_mask; |
3e7ee490 HJ |
211 | } |
212 | } | |
213 | ||
822f18d4 | 214 | /* Initialize the ring buffer. */ |
72a95cbc | 215 | int hv_ringbuffer_init(struct hv_ring_buffer_info *ring_info, |
9988ce68 | 216 | struct page *pages, u32 page_cnt) |
3e7ee490 | 217 | { |
9988ce68 VK |
218 | int i; |
219 | struct page **pages_wraparound; | |
220 | ||
221 | BUILD_BUG_ON((sizeof(struct hv_ring_buffer) != PAGE_SIZE)); | |
3e7ee490 | 222 | |
fc8c72eb | 223 | memset(ring_info, 0, sizeof(struct hv_ring_buffer_info)); |
3e7ee490 | 224 | |
9988ce68 VK |
225 | /* |
226 | * First page holds struct hv_ring_buffer, do wraparound mapping for | |
227 | * the rest. | |
228 | */ | |
229 | pages_wraparound = kzalloc(sizeof(struct page *) * (page_cnt * 2 - 1), | |
230 | GFP_KERNEL); | |
231 | if (!pages_wraparound) | |
232 | return -ENOMEM; | |
233 | ||
234 | pages_wraparound[0] = pages; | |
235 | for (i = 0; i < 2 * (page_cnt - 1); i++) | |
236 | pages_wraparound[i + 1] = &pages[i % (page_cnt - 1) + 1]; | |
237 | ||
238 | ring_info->ring_buffer = (struct hv_ring_buffer *) | |
239 | vmap(pages_wraparound, page_cnt * 2 - 1, VM_MAP, PAGE_KERNEL); | |
240 | ||
241 | kfree(pages_wraparound); | |
242 | ||
243 | ||
244 | if (!ring_info->ring_buffer) | |
245 | return -ENOMEM; | |
246 | ||
fc8c72eb HZ |
247 | ring_info->ring_buffer->read_index = |
248 | ring_info->ring_buffer->write_index = 0; | |
3e7ee490 | 249 | |
822f18d4 | 250 | /* Set the feature bit for enabling flow control. */ |
046c7911 S |
251 | ring_info->ring_buffer->feature_bits.value = 1; |
252 | ||
9988ce68 VK |
253 | ring_info->ring_size = page_cnt << PAGE_SHIFT; |
254 | ring_info->ring_datasize = ring_info->ring_size - | |
255 | sizeof(struct hv_ring_buffer); | |
3e7ee490 | 256 | |
fc8c72eb | 257 | spin_lock_init(&ring_info->ring_lock); |
3e7ee490 HJ |
258 | |
259 | return 0; | |
260 | } | |
261 | ||
822f18d4 | 262 | /* Cleanup the ring buffer. */ |
2dba688b | 263 | void hv_ringbuffer_cleanup(struct hv_ring_buffer_info *ring_info) |
3e7ee490 | 264 | { |
9988ce68 | 265 | vunmap(ring_info->ring_buffer); |
3e7ee490 HJ |
266 | } |
267 | ||
822f18d4 | 268 | /* Write to the ring buffer. */ |
1f6ee4e7 | 269 | int hv_ringbuffer_write(struct vmbus_channel *channel, |
e4165a0f | 270 | const struct kvec *kv_list, u32 kv_count) |
3e7ee490 | 271 | { |
4408f531 | 272 | int i = 0; |
fc8c72eb | 273 | u32 bytes_avail_towrite; |
fc8c72eb | 274 | u32 totalbytes_towrite = 0; |
3e7ee490 | 275 | |
66a60543 | 276 | u32 next_write_location; |
98fa8cf4 | 277 | u32 old_write; |
fc8c72eb | 278 | u64 prev_indices = 0; |
fe760e4d | 279 | unsigned long flags = 0; |
1f6ee4e7 | 280 | struct hv_ring_buffer_info *outring_info = &channel->outbound; |
3e7ee490 | 281 | |
e7e97dd8 S |
282 | if (channel->rescind) |
283 | return -ENODEV; | |
284 | ||
011a7c3c S |
285 | for (i = 0; i < kv_count; i++) |
286 | totalbytes_towrite += kv_list[i].iov_len; | |
3e7ee490 | 287 | |
fc8c72eb | 288 | totalbytes_towrite += sizeof(u64); |
3e7ee490 | 289 | |
5529eaf6 | 290 | spin_lock_irqsave(&outring_info->ring_lock, flags); |
3e7ee490 | 291 | |
a6341f00 | 292 | bytes_avail_towrite = hv_get_bytes_to_write(outring_info); |
3e7ee490 | 293 | |
822f18d4 VK |
294 | /* |
295 | * If there is only room for the packet, assume it is full. | |
296 | * Otherwise, the next time around, we think the ring buffer | |
297 | * is empty since the read index == write index. | |
298 | */ | |
fc8c72eb | 299 | if (bytes_avail_towrite <= totalbytes_towrite) { |
5529eaf6 | 300 | spin_unlock_irqrestore(&outring_info->ring_lock, flags); |
d2598f01 | 301 | return -EAGAIN; |
3e7ee490 HJ |
302 | } |
303 | ||
454f18a9 | 304 | /* Write to the ring buffer */ |
2b8a912e | 305 | next_write_location = hv_get_next_write_location(outring_info); |
3e7ee490 | 306 | |
98fa8cf4 S |
307 | old_write = next_write_location; |
308 | ||
011a7c3c | 309 | for (i = 0; i < kv_count; i++) { |
2b8a912e | 310 | next_write_location = hv_copyto_ringbuffer(outring_info, |
fc8c72eb | 311 | next_write_location, |
011a7c3c S |
312 | kv_list[i].iov_base, |
313 | kv_list[i].iov_len); | |
3e7ee490 HJ |
314 | } |
315 | ||
454f18a9 | 316 | /* Set previous packet start */ |
2b8a912e | 317 | prev_indices = hv_get_ring_bufferindices(outring_info); |
3e7ee490 | 318 | |
2b8a912e | 319 | next_write_location = hv_copyto_ringbuffer(outring_info, |
fc8c72eb HZ |
320 | next_write_location, |
321 | &prev_indices, | |
b219b3f7 | 322 | sizeof(u64)); |
3e7ee490 | 323 | |
98fa8cf4 | 324 | /* Issue a full memory barrier before updating the write index */ |
dcd0eeca | 325 | virt_mb(); |
3e7ee490 | 326 | |
454f18a9 | 327 | /* Now, update the write location */ |
2b8a912e | 328 | hv_set_next_write_location(outring_info, next_write_location); |
3e7ee490 | 329 | |
3e7ee490 | 330 | |
5529eaf6 | 331 | spin_unlock_irqrestore(&outring_info->ring_lock, flags); |
98fa8cf4 | 332 | |
b103a56f | 333 | hv_signal_on_write(old_write, channel); |
e7e97dd8 S |
334 | |
335 | if (channel->rescind) | |
336 | return -ENODEV; | |
337 | ||
3e7ee490 HJ |
338 | return 0; |
339 | } | |
340 | ||
f3dd3f47 | 341 | static inline void |
342 | init_cached_read_index(struct hv_ring_buffer_info *rbi) | |
343 | { | |
344 | rbi->cached_read_index = rbi->ring_buffer->read_index; | |
345 | } | |
346 | ||
3372592a | 347 | int hv_ringbuffer_read(struct vmbus_channel *channel, |
940b68e2 | 348 | void *buffer, u32 buflen, u32 *buffer_actual_len, |
3372592a | 349 | u64 *requestid, bool raw) |
3e7ee490 | 350 | { |
fc8c72eb HZ |
351 | u32 bytes_avail_toread; |
352 | u32 next_read_location = 0; | |
353 | u64 prev_indices = 0; | |
940b68e2 VK |
354 | struct vmpacket_descriptor desc; |
355 | u32 offset; | |
356 | u32 packetlen; | |
357 | int ret = 0; | |
3372592a | 358 | struct hv_ring_buffer_info *inring_info = &channel->inbound; |
3e7ee490 | 359 | |
fc8c72eb | 360 | if (buflen <= 0) |
a16e1485 | 361 | return -EINVAL; |
3e7ee490 | 362 | |
3e7ee490 | 363 | |
940b68e2 VK |
364 | *buffer_actual_len = 0; |
365 | *requestid = 0; | |
366 | ||
a6341f00 | 367 | bytes_avail_toread = hv_get_bytes_to_read(inring_info); |
454f18a9 | 368 | /* Make sure there is something to read */ |
940b68e2 VK |
369 | if (bytes_avail_toread < sizeof(desc)) { |
370 | /* | |
371 | * No error is set when there is even no header, drivers are | |
372 | * supposed to analyze buffer_actual_len. | |
373 | */ | |
3eba9a77 | 374 | return ret; |
940b68e2 | 375 | } |
3e7ee490 | 376 | |
f3dd3f47 | 377 | init_cached_read_index(inring_info); |
378 | ||
940b68e2 VK |
379 | next_read_location = hv_get_next_read_location(inring_info); |
380 | next_read_location = hv_copyfrom_ringbuffer(inring_info, &desc, | |
381 | sizeof(desc), | |
382 | next_read_location); | |
383 | ||
384 | offset = raw ? 0 : (desc.offset8 << 3); | |
385 | packetlen = (desc.len8 << 3) - offset; | |
386 | *buffer_actual_len = packetlen; | |
387 | *requestid = desc.trans_id; | |
388 | ||
3eba9a77 S |
389 | if (bytes_avail_toread < packetlen + offset) |
390 | return -EAGAIN; | |
940b68e2 | 391 | |
3eba9a77 S |
392 | if (packetlen > buflen) |
393 | return -ENOBUFS; | |
3e7ee490 | 394 | |
1ac58644 | 395 | next_read_location = |
2b8a912e | 396 | hv_get_next_readlocation_withoffset(inring_info, offset); |
3e7ee490 | 397 | |
2b8a912e | 398 | next_read_location = hv_copyfrom_ringbuffer(inring_info, |
fc8c72eb | 399 | buffer, |
940b68e2 | 400 | packetlen, |
fc8c72eb | 401 | next_read_location); |
3e7ee490 | 402 | |
2b8a912e | 403 | next_read_location = hv_copyfrom_ringbuffer(inring_info, |
fc8c72eb | 404 | &prev_indices, |
4408f531 | 405 | sizeof(u64), |
fc8c72eb | 406 | next_read_location); |
3e7ee490 | 407 | |
822f18d4 VK |
408 | /* |
409 | * Make sure all reads are done before we update the read index since | |
410 | * the writer may start writing to the read area once the read index | |
411 | * is updated. | |
412 | */ | |
dcd0eeca | 413 | virt_mb(); |
3e7ee490 | 414 | |
454f18a9 | 415 | /* Update the read index */ |
2b8a912e | 416 | hv_set_next_read_location(inring_info, next_read_location); |
3e7ee490 | 417 | |
3372592a | 418 | hv_signal_on_read(channel); |
c2b8e520 | 419 | |
940b68e2 | 420 | return ret; |
b5f53dde | 421 | } |
f3dd3f47 | 422 | |
423 | /* | |
424 | * Determine number of bytes available in ring buffer after | |
425 | * the current iterator (priv_read_index) location. | |
426 | * | |
427 | * This is similar to hv_get_bytes_to_read but with private | |
428 | * read index instead. | |
429 | */ | |
430 | static u32 hv_pkt_iter_avail(const struct hv_ring_buffer_info *rbi) | |
431 | { | |
432 | u32 priv_read_loc = rbi->priv_read_index; | |
433 | u32 write_loc = READ_ONCE(rbi->ring_buffer->write_index); | |
434 | ||
435 | if (write_loc >= priv_read_loc) | |
436 | return write_loc - priv_read_loc; | |
437 | else | |
438 | return (rbi->ring_datasize - priv_read_loc) + write_loc; | |
439 | } | |
440 | ||
441 | /* | |
442 | * Get first vmbus packet from ring buffer after read_index | |
443 | * | |
444 | * If ring buffer is empty, returns NULL and no other action needed. | |
445 | */ | |
446 | struct vmpacket_descriptor *hv_pkt_iter_first(struct vmbus_channel *channel) | |
447 | { | |
448 | struct hv_ring_buffer_info *rbi = &channel->inbound; | |
449 | ||
450 | /* set state for later hv_signal_on_read() */ | |
451 | init_cached_read_index(rbi); | |
452 | ||
453 | if (hv_pkt_iter_avail(rbi) < sizeof(struct vmpacket_descriptor)) | |
454 | return NULL; | |
455 | ||
456 | return hv_get_ring_buffer(rbi) + rbi->priv_read_index; | |
457 | } | |
458 | EXPORT_SYMBOL_GPL(hv_pkt_iter_first); | |
459 | ||
460 | /* | |
461 | * Get next vmbus packet from ring buffer. | |
462 | * | |
463 | * Advances the current location (priv_read_index) and checks for more | |
464 | * data. If the end of the ring buffer is reached, then return NULL. | |
465 | */ | |
466 | struct vmpacket_descriptor * | |
467 | __hv_pkt_iter_next(struct vmbus_channel *channel, | |
468 | const struct vmpacket_descriptor *desc) | |
469 | { | |
470 | struct hv_ring_buffer_info *rbi = &channel->inbound; | |
471 | u32 packetlen = desc->len8 << 3; | |
472 | u32 dsize = rbi->ring_datasize; | |
473 | ||
474 | /* bump offset to next potential packet */ | |
475 | rbi->priv_read_index += packetlen + VMBUS_PKT_TRAILER; | |
476 | if (rbi->priv_read_index >= dsize) | |
477 | rbi->priv_read_index -= dsize; | |
478 | ||
479 | /* more data? */ | |
480 | if (hv_pkt_iter_avail(rbi) < sizeof(struct vmpacket_descriptor)) | |
481 | return NULL; | |
482 | else | |
483 | return hv_get_ring_buffer(rbi) + rbi->priv_read_index; | |
484 | } | |
485 | EXPORT_SYMBOL_GPL(__hv_pkt_iter_next); | |
486 | ||
487 | /* | |
488 | * Update host ring buffer after iterating over packets. | |
489 | */ | |
490 | void hv_pkt_iter_close(struct vmbus_channel *channel) | |
491 | { | |
492 | struct hv_ring_buffer_info *rbi = &channel->inbound; | |
493 | ||
494 | /* | |
495 | * Make sure all reads are done before we update the read index since | |
496 | * the writer may start writing to the read area once the read index | |
497 | * is updated. | |
498 | */ | |
499 | virt_rmb(); | |
500 | rbi->ring_buffer->read_index = rbi->priv_read_index; | |
501 | ||
502 | hv_signal_on_read(channel); | |
503 | } | |
504 | EXPORT_SYMBOL_GPL(hv_pkt_iter_close); |