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);