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
)
75 if (rbi
->ring_buffer
->interrupt_mask
)
79 * This is the only case we need to signal when the
80 * ring transitions from being empty to non-empty.
82 if (old_write
== rbi
->ring_buffer
->read_index
)
89 * To optimize the flow management on the send-side,
90 * when the sender is blocked because of lack of
91 * sufficient space in the ring buffer, potential the
92 * consumer of the ring buffer can signal the producer.
93 * This is controlled by the following parameters:
95 * 1. pending_send_sz: This is the size in bytes that the
96 * producer is trying to send.
97 * 2. The feature bit feat_pending_send_sz set to indicate if
98 * the consumer of the ring will signal when the ring
99 * state transitions from being full to a state where
100 * there is room for the producer to send the pending packet.
103 static bool hv_need_to_signal_on_read(u32 old_rd
,
104 struct hv_ring_buffer_info
*rbi
)
109 u32 write_loc
= rbi
->ring_buffer
->write_index
;
110 u32 read_loc
= rbi
->ring_buffer
->read_index
;
111 u32 pending_sz
= rbi
->ring_buffer
->pending_send_sz
;
114 * If the other end is not blocked on write don't bother.
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
;
123 prev_write_sz
= write_loc
>= old_rd
? r_size
- (write_loc
- old_rd
) :
127 if ((prev_write_sz
< pending_sz
) && (cur_write_sz
>= pending_sz
))
134 * hv_get_next_write_location()
136 * Get the next write location for the specified ring buffer
140 hv_get_next_write_location(struct hv_ring_buffer_info
*ring_info
)
142 u32 next
= ring_info
->ring_buffer
->write_index
;
148 * hv_set_next_write_location()
150 * Set the next write location for the specified ring buffer
154 hv_set_next_write_location(struct hv_ring_buffer_info
*ring_info
,
155 u32 next_write_location
)
157 ring_info
->ring_buffer
->write_index
= next_write_location
;
161 * hv_get_next_read_location()
163 * Get the next read location for the specified ring buffer
166 hv_get_next_read_location(struct hv_ring_buffer_info
*ring_info
)
168 u32 next
= ring_info
->ring_buffer
->read_index
;
174 * hv_get_next_readlocation_withoffset()
176 * Get the next read location + offset for the specified ring buffer.
177 * This allows the caller to skip
180 hv_get_next_readlocation_withoffset(struct hv_ring_buffer_info
*ring_info
,
183 u32 next
= ring_info
->ring_buffer
->read_index
;
186 next
%= ring_info
->ring_datasize
;
193 * hv_set_next_read_location()
195 * Set the next read location for the specified ring buffer
199 hv_set_next_read_location(struct hv_ring_buffer_info
*ring_info
,
200 u32 next_read_location
)
202 ring_info
->ring_buffer
->read_index
= next_read_location
;
208 * hv_get_ring_buffer()
210 * Get the start of the ring buffer
213 hv_get_ring_buffer(struct hv_ring_buffer_info
*ring_info
)
215 return (void *)ring_info
->ring_buffer
->buffer
;
221 * hv_get_ring_buffersize()
223 * Get the size of the ring buffer
226 hv_get_ring_buffersize(struct hv_ring_buffer_info
*ring_info
)
228 return ring_info
->ring_datasize
;
233 * hv_get_ring_bufferindices()
235 * Get the read and write indices as u64 of the specified ring buffer
239 hv_get_ring_bufferindices(struct hv_ring_buffer_info
*ring_info
)
241 return (u64
)ring_info
->ring_buffer
->write_index
<< 32;
246 * hv_copyfrom_ringbuffer()
248 * Helper routine to copy to source from ring buffer.
249 * Assume there is enough room. Handles wrap-around in src case only!!
252 static u32
hv_copyfrom_ringbuffer(
253 struct hv_ring_buffer_info
*ring_info
,
256 u32 start_read_offset
)
258 void *ring_buffer
= hv_get_ring_buffer(ring_info
);
259 u32 ring_buffer_size
= hv_get_ring_buffersize(ring_info
);
263 /* wrap-around detected at the src */
264 if (destlen
> ring_buffer_size
- start_read_offset
) {
265 frag_len
= ring_buffer_size
- start_read_offset
;
267 memcpy(dest
, ring_buffer
+ start_read_offset
, frag_len
);
268 memcpy(dest
+ frag_len
, ring_buffer
, destlen
- frag_len
);
271 memcpy(dest
, ring_buffer
+ start_read_offset
, destlen
);
274 start_read_offset
+= destlen
;
275 start_read_offset
%= ring_buffer_size
;
277 return start_read_offset
;
283 * hv_copyto_ringbuffer()
285 * Helper routine to copy from source to ring buffer.
286 * Assume there is enough room. Handles wrap-around in dest case only!!
289 static u32
hv_copyto_ringbuffer(
290 struct hv_ring_buffer_info
*ring_info
,
291 u32 start_write_offset
,
295 void *ring_buffer
= hv_get_ring_buffer(ring_info
);
296 u32 ring_buffer_size
= hv_get_ring_buffersize(ring_info
);
299 /* wrap-around detected! */
300 if (srclen
> ring_buffer_size
- start_write_offset
) {
301 frag_len
= ring_buffer_size
- start_write_offset
;
302 memcpy(ring_buffer
+ start_write_offset
, src
, frag_len
);
303 memcpy(ring_buffer
, src
+ frag_len
, srclen
- frag_len
);
305 memcpy(ring_buffer
+ start_write_offset
, src
, srclen
);
307 start_write_offset
+= srclen
;
308 start_write_offset
%= ring_buffer_size
;
310 return start_write_offset
;
315 * hv_ringbuffer_get_debuginfo()
317 * Get various debug metrics for the specified ring buffer
320 void hv_ringbuffer_get_debuginfo(struct hv_ring_buffer_info
*ring_info
,
321 struct hv_ring_buffer_debug_info
*debug_info
)
323 u32 bytes_avail_towrite
;
324 u32 bytes_avail_toread
;
326 if (ring_info
->ring_buffer
) {
327 hv_get_ringbuffer_availbytes(ring_info
,
329 &bytes_avail_towrite
);
331 debug_info
->bytes_avail_toread
= bytes_avail_toread
;
332 debug_info
->bytes_avail_towrite
= bytes_avail_towrite
;
333 debug_info
->current_read_index
=
334 ring_info
->ring_buffer
->read_index
;
335 debug_info
->current_write_index
=
336 ring_info
->ring_buffer
->write_index
;
337 debug_info
->current_interrupt_mask
=
338 ring_info
->ring_buffer
->interrupt_mask
;
344 * hv_ringbuffer_init()
346 *Initialize the ring buffer
349 int hv_ringbuffer_init(struct hv_ring_buffer_info
*ring_info
,
350 void *buffer
, u32 buflen
)
352 if (sizeof(struct hv_ring_buffer
) != PAGE_SIZE
)
355 memset(ring_info
, 0, sizeof(struct hv_ring_buffer_info
));
357 ring_info
->ring_buffer
= (struct hv_ring_buffer
*)buffer
;
358 ring_info
->ring_buffer
->read_index
=
359 ring_info
->ring_buffer
->write_index
= 0;
361 ring_info
->ring_size
= buflen
;
362 ring_info
->ring_datasize
= buflen
- sizeof(struct hv_ring_buffer
);
364 spin_lock_init(&ring_info
->ring_lock
);
371 * hv_ringbuffer_cleanup()
373 * Cleanup the ring buffer
376 void hv_ringbuffer_cleanup(struct hv_ring_buffer_info
*ring_info
)
382 * hv_ringbuffer_write()
384 * Write to the ring buffer
387 int hv_ringbuffer_write(struct hv_ring_buffer_info
*outring_info
,
388 struct scatterlist
*sglist
, u32 sgcount
, bool *signal
)
391 u32 bytes_avail_towrite
;
392 u32 bytes_avail_toread
;
393 u32 totalbytes_towrite
= 0;
395 struct scatterlist
*sg
;
396 u32 next_write_location
;
398 u64 prev_indices
= 0;
401 for_each_sg(sglist
, sg
, sgcount
, i
)
403 totalbytes_towrite
+= sg
->length
;
406 totalbytes_towrite
+= sizeof(u64
);
408 spin_lock_irqsave(&outring_info
->ring_lock
, flags
);
410 hv_get_ringbuffer_availbytes(outring_info
,
412 &bytes_avail_towrite
);
415 /* If there is only room for the packet, assume it is full. */
416 /* Otherwise, the next time around, we think the ring buffer */
417 /* is empty since the read index == write index */
418 if (bytes_avail_towrite
<= totalbytes_towrite
) {
419 spin_unlock_irqrestore(&outring_info
->ring_lock
, flags
);
423 /* Write to the ring buffer */
424 next_write_location
= hv_get_next_write_location(outring_info
);
426 old_write
= next_write_location
;
428 for_each_sg(sglist
, sg
, sgcount
, i
)
430 next_write_location
= hv_copyto_ringbuffer(outring_info
,
436 /* Set previous packet start */
437 prev_indices
= hv_get_ring_bufferindices(outring_info
);
439 next_write_location
= hv_copyto_ringbuffer(outring_info
,
444 /* Issue a full memory barrier before updating the write index */
447 /* Now, update the write location */
448 hv_set_next_write_location(outring_info
, next_write_location
);
451 spin_unlock_irqrestore(&outring_info
->ring_lock
, flags
);
453 *signal
= hv_need_to_signal(old_write
, outring_info
);
460 * hv_ringbuffer_peek()
462 * Read without advancing the read index
465 int hv_ringbuffer_peek(struct hv_ring_buffer_info
*Inring_info
,
466 void *Buffer
, u32 buflen
)
468 u32 bytes_avail_towrite
;
469 u32 bytes_avail_toread
;
470 u32 next_read_location
= 0;
473 spin_lock_irqsave(&Inring_info
->ring_lock
, flags
);
475 hv_get_ringbuffer_availbytes(Inring_info
,
477 &bytes_avail_towrite
);
479 /* Make sure there is something to read */
480 if (bytes_avail_toread
< buflen
) {
482 spin_unlock_irqrestore(&Inring_info
->ring_lock
, flags
);
487 /* Convert to byte offset */
488 next_read_location
= hv_get_next_read_location(Inring_info
);
490 next_read_location
= hv_copyfrom_ringbuffer(Inring_info
,
495 spin_unlock_irqrestore(&Inring_info
->ring_lock
, flags
);
503 * hv_ringbuffer_read()
505 * Read and advance the read index
508 int hv_ringbuffer_read(struct hv_ring_buffer_info
*inring_info
, void *buffer
,
509 u32 buflen
, u32 offset
, bool *signal
)
511 u32 bytes_avail_towrite
;
512 u32 bytes_avail_toread
;
513 u32 next_read_location
= 0;
514 u64 prev_indices
= 0;
521 spin_lock_irqsave(&inring_info
->ring_lock
, flags
);
523 hv_get_ringbuffer_availbytes(inring_info
,
525 &bytes_avail_towrite
);
527 old_read
= bytes_avail_toread
;
529 /* Make sure there is something to read */
530 if (bytes_avail_toread
< buflen
) {
531 spin_unlock_irqrestore(&inring_info
->ring_lock
, flags
);
537 hv_get_next_readlocation_withoffset(inring_info
, offset
);
539 next_read_location
= hv_copyfrom_ringbuffer(inring_info
,
544 next_read_location
= hv_copyfrom_ringbuffer(inring_info
,
549 /* Make sure all reads are done before we update the read index since */
550 /* the writer may start writing to the read area once the read index */
554 /* Update the read index */
555 hv_set_next_read_location(inring_info
, next_read_location
);
557 spin_unlock_irqrestore(&inring_info
->ring_lock
, flags
);
559 *signal
= hv_need_to_signal_on_read(old_read
, inring_info
);