3 * Copyright (c) 2009, Microsoft Corporation.
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.
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
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.
19 * Haiyang Zhang <haiyangz@microsoft.com>
20 * Hank Janssen <hjanssen@microsoft.com>
21 * K. Y. Srinivasan <kys@microsoft.com>
24 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
26 #include <linux/kernel.h>
28 #include <linux/hyperv.h>
30 #include "hyperv_vmbus.h"
32 void hv_begin_read(struct hv_ring_buffer_info
*rbi
)
34 rbi
->ring_buffer
->interrupt_mask
= 1;
38 u32
hv_end_read(struct hv_ring_buffer_info
*rbi
)
43 rbi
->ring_buffer
->interrupt_mask
= 0;
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
51 hv_get_ringbuffer_availbytes(rbi
, &read
, &write
);
57 * When we write to the ring buffer, check if the host needs to
58 * be signaled. Here is the details of this protocol:
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
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
72 static bool hv_need_to_signal(u32 old_write
, struct hv_ring_buffer_info
*rbi
)
74 if (rbi
->ring_buffer
->interrupt_mask
)
78 * This is the only case we need to signal when the
79 * ring transitions from being empty to non-empty.
81 if (old_write
== rbi
->ring_buffer
->read_index
)
88 * To optimize the flow management on the send-side,
89 * when the sender is blocked because of lack of
90 * sufficient space in the ring buffer, potential the
91 * consumer of the ring buffer can signal the producer.
92 * This is controlled by the following parameters:
94 * 1. pending_send_sz: This is the size in bytes that the
95 * producer is trying to send.
96 * 2. The feature bit feat_pending_send_sz set to indicate if
97 * the consumer of the ring will signal when the ring
98 * state transitions from being full to a state where
99 * there is room for the producer to send the pending packet.
102 static bool hv_need_to_signal_on_read(u32 old_rd
,
103 struct hv_ring_buffer_info
*rbi
)
108 u32 write_loc
= rbi
->ring_buffer
->write_index
;
109 u32 read_loc
= rbi
->ring_buffer
->read_index
;
110 u32 pending_sz
= rbi
->ring_buffer
->pending_send_sz
;
113 * If the other end is not blocked on write don't bother.
118 r_size
= rbi
->ring_datasize
;
119 cur_write_sz
= write_loc
>= read_loc
? r_size
- (write_loc
- read_loc
) :
120 read_loc
- write_loc
;
122 prev_write_sz
= write_loc
>= old_rd
? r_size
- (write_loc
- old_rd
) :
126 if ((prev_write_sz
< pending_sz
) && (cur_write_sz
>= pending_sz
))
133 * hv_get_next_write_location()
135 * Get the next write location for the specified ring buffer
139 hv_get_next_write_location(struct hv_ring_buffer_info
*ring_info
)
141 u32 next
= ring_info
->ring_buffer
->write_index
;
147 * hv_set_next_write_location()
149 * Set the next write location for the specified ring buffer
153 hv_set_next_write_location(struct hv_ring_buffer_info
*ring_info
,
154 u32 next_write_location
)
156 ring_info
->ring_buffer
->write_index
= next_write_location
;
160 * hv_get_next_read_location()
162 * Get the next read location for the specified ring buffer
165 hv_get_next_read_location(struct hv_ring_buffer_info
*ring_info
)
167 u32 next
= ring_info
->ring_buffer
->read_index
;
173 * hv_get_next_readlocation_withoffset()
175 * Get the next read location + offset for the specified ring buffer.
176 * This allows the caller to skip
179 hv_get_next_readlocation_withoffset(struct hv_ring_buffer_info
*ring_info
,
182 u32 next
= ring_info
->ring_buffer
->read_index
;
185 next
%= ring_info
->ring_datasize
;
192 * hv_set_next_read_location()
194 * Set the next read location for the specified ring buffer
198 hv_set_next_read_location(struct hv_ring_buffer_info
*ring_info
,
199 u32 next_read_location
)
201 ring_info
->ring_buffer
->read_index
= next_read_location
;
207 * hv_get_ring_buffer()
209 * Get the start of the ring buffer
212 hv_get_ring_buffer(struct hv_ring_buffer_info
*ring_info
)
214 return (void *)ring_info
->ring_buffer
->buffer
;
220 * hv_get_ring_buffersize()
222 * Get the size of the ring buffer
225 hv_get_ring_buffersize(struct hv_ring_buffer_info
*ring_info
)
227 return ring_info
->ring_datasize
;
232 * hv_get_ring_bufferindices()
234 * Get the read and write indices as u64 of the specified ring buffer
238 hv_get_ring_bufferindices(struct hv_ring_buffer_info
*ring_info
)
240 return (u64
)ring_info
->ring_buffer
->write_index
<< 32;
245 * hv_copyfrom_ringbuffer()
247 * Helper routine to copy to source from ring buffer.
248 * Assume there is enough room. Handles wrap-around in src case only!!
251 static u32
hv_copyfrom_ringbuffer(
252 struct hv_ring_buffer_info
*ring_info
,
255 u32 start_read_offset
)
257 void *ring_buffer
= hv_get_ring_buffer(ring_info
);
258 u32 ring_buffer_size
= hv_get_ring_buffersize(ring_info
);
262 /* wrap-around detected at the src */
263 if (destlen
> ring_buffer_size
- start_read_offset
) {
264 frag_len
= ring_buffer_size
- start_read_offset
;
266 memcpy(dest
, ring_buffer
+ start_read_offset
, frag_len
);
267 memcpy(dest
+ frag_len
, ring_buffer
, destlen
- frag_len
);
270 memcpy(dest
, ring_buffer
+ start_read_offset
, destlen
);
273 start_read_offset
+= destlen
;
274 start_read_offset
%= ring_buffer_size
;
276 return start_read_offset
;
282 * hv_copyto_ringbuffer()
284 * Helper routine to copy from source to ring buffer.
285 * Assume there is enough room. Handles wrap-around in dest case only!!
288 static u32
hv_copyto_ringbuffer(
289 struct hv_ring_buffer_info
*ring_info
,
290 u32 start_write_offset
,
294 void *ring_buffer
= hv_get_ring_buffer(ring_info
);
295 u32 ring_buffer_size
= hv_get_ring_buffersize(ring_info
);
298 /* wrap-around detected! */
299 if (srclen
> ring_buffer_size
- start_write_offset
) {
300 frag_len
= ring_buffer_size
- start_write_offset
;
301 memcpy(ring_buffer
+ start_write_offset
, src
, frag_len
);
302 memcpy(ring_buffer
, src
+ frag_len
, srclen
- frag_len
);
304 memcpy(ring_buffer
+ start_write_offset
, src
, srclen
);
306 start_write_offset
+= srclen
;
307 start_write_offset
%= ring_buffer_size
;
309 return start_write_offset
;
314 * hv_ringbuffer_get_debuginfo()
316 * Get various debug metrics for the specified ring buffer
319 void hv_ringbuffer_get_debuginfo(struct hv_ring_buffer_info
*ring_info
,
320 struct hv_ring_buffer_debug_info
*debug_info
)
322 u32 bytes_avail_towrite
;
323 u32 bytes_avail_toread
;
325 if (ring_info
->ring_buffer
) {
326 hv_get_ringbuffer_availbytes(ring_info
,
328 &bytes_avail_towrite
);
330 debug_info
->bytes_avail_toread
= bytes_avail_toread
;
331 debug_info
->bytes_avail_towrite
= bytes_avail_towrite
;
332 debug_info
->current_read_index
=
333 ring_info
->ring_buffer
->read_index
;
334 debug_info
->current_write_index
=
335 ring_info
->ring_buffer
->write_index
;
336 debug_info
->current_interrupt_mask
=
337 ring_info
->ring_buffer
->interrupt_mask
;
343 * hv_ringbuffer_init()
345 *Initialize the ring buffer
348 int hv_ringbuffer_init(struct hv_ring_buffer_info
*ring_info
,
349 void *buffer
, u32 buflen
)
351 if (sizeof(struct hv_ring_buffer
) != PAGE_SIZE
)
354 memset(ring_info
, 0, sizeof(struct hv_ring_buffer_info
));
356 ring_info
->ring_buffer
= (struct hv_ring_buffer
*)buffer
;
357 ring_info
->ring_buffer
->read_index
=
358 ring_info
->ring_buffer
->write_index
= 0;
360 ring_info
->ring_size
= buflen
;
361 ring_info
->ring_datasize
= buflen
- sizeof(struct hv_ring_buffer
);
363 spin_lock_init(&ring_info
->ring_lock
);
370 * hv_ringbuffer_cleanup()
372 * Cleanup the ring buffer
375 void hv_ringbuffer_cleanup(struct hv_ring_buffer_info
*ring_info
)
381 * hv_ringbuffer_write()
383 * Write to the ring buffer
386 int hv_ringbuffer_write(struct hv_ring_buffer_info
*outring_info
,
387 struct scatterlist
*sglist
, u32 sgcount
, bool *signal
)
390 u32 bytes_avail_towrite
;
391 u32 bytes_avail_toread
;
392 u32 totalbytes_towrite
= 0;
394 struct scatterlist
*sg
;
395 u32 next_write_location
;
397 u64 prev_indices
= 0;
400 for_each_sg(sglist
, sg
, sgcount
, i
)
402 totalbytes_towrite
+= sg
->length
;
405 totalbytes_towrite
+= sizeof(u64
);
407 spin_lock_irqsave(&outring_info
->ring_lock
, flags
);
409 hv_get_ringbuffer_availbytes(outring_info
,
411 &bytes_avail_towrite
);
414 /* If there is only room for the packet, assume it is full. */
415 /* Otherwise, the next time around, we think the ring buffer */
416 /* is empty since the read index == write index */
417 if (bytes_avail_towrite
<= totalbytes_towrite
) {
418 spin_unlock_irqrestore(&outring_info
->ring_lock
, flags
);
422 /* Write to the ring buffer */
423 next_write_location
= hv_get_next_write_location(outring_info
);
425 old_write
= next_write_location
;
427 for_each_sg(sglist
, sg
, sgcount
, i
)
429 next_write_location
= hv_copyto_ringbuffer(outring_info
,
435 /* Set previous packet start */
436 prev_indices
= hv_get_ring_bufferindices(outring_info
);
438 next_write_location
= hv_copyto_ringbuffer(outring_info
,
443 /* Issue a full memory barrier before updating the write index */
446 /* Now, update the write location */
447 hv_set_next_write_location(outring_info
, next_write_location
);
450 spin_unlock_irqrestore(&outring_info
->ring_lock
, flags
);
452 *signal
= hv_need_to_signal(old_write
, outring_info
);
459 * hv_ringbuffer_peek()
461 * Read without advancing the read index
464 int hv_ringbuffer_peek(struct hv_ring_buffer_info
*Inring_info
,
465 void *Buffer
, u32 buflen
)
467 u32 bytes_avail_towrite
;
468 u32 bytes_avail_toread
;
469 u32 next_read_location
= 0;
472 spin_lock_irqsave(&Inring_info
->ring_lock
, flags
);
474 hv_get_ringbuffer_availbytes(Inring_info
,
476 &bytes_avail_towrite
);
478 /* Make sure there is something to read */
479 if (bytes_avail_toread
< buflen
) {
481 spin_unlock_irqrestore(&Inring_info
->ring_lock
, flags
);
486 /* Convert to byte offset */
487 next_read_location
= hv_get_next_read_location(Inring_info
);
489 next_read_location
= hv_copyfrom_ringbuffer(Inring_info
,
494 spin_unlock_irqrestore(&Inring_info
->ring_lock
, flags
);
502 * hv_ringbuffer_read()
504 * Read and advance the read index
507 int hv_ringbuffer_read(struct hv_ring_buffer_info
*inring_info
, void *buffer
,
508 u32 buflen
, u32 offset
, bool *signal
)
510 u32 bytes_avail_towrite
;
511 u32 bytes_avail_toread
;
512 u32 next_read_location
= 0;
513 u64 prev_indices
= 0;
520 spin_lock_irqsave(&inring_info
->ring_lock
, flags
);
522 hv_get_ringbuffer_availbytes(inring_info
,
524 &bytes_avail_towrite
);
526 old_read
= bytes_avail_toread
;
528 /* Make sure there is something to read */
529 if (bytes_avail_toread
< buflen
) {
530 spin_unlock_irqrestore(&inring_info
->ring_lock
, flags
);
536 hv_get_next_readlocation_withoffset(inring_info
, offset
);
538 next_read_location
= hv_copyfrom_ringbuffer(inring_info
,
543 next_read_location
= hv_copyfrom_ringbuffer(inring_info
,
548 /* Make sure all reads are done before we update the read index since */
549 /* the writer may start writing to the read area once the read index */
553 /* Update the read index */
554 hv_set_next_read_location(inring_info
, next_read_location
);
556 spin_unlock_irqrestore(&inring_info
->ring_lock
, flags
);
558 *signal
= hv_need_to_signal_on_read(old_read
, inring_info
);