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>
29 #include <linux/uio.h>
31 #include "hyperv_vmbus.h"
33 void hv_begin_read(struct hv_ring_buffer_info
*rbi
)
35 rbi
->ring_buffer
->interrupt_mask
= 1;
39 u32
hv_end_read(struct hv_ring_buffer_info
*rbi
)
44 rbi
->ring_buffer
->interrupt_mask
= 0;
48 * Now check to see if the ring buffer is still empty.
49 * If it is not, we raced and we need to process new
52 hv_get_ringbuffer_availbytes(rbi
, &read
, &write
);
58 * When we write to the ring buffer, check if the host needs to
59 * be signaled. Here is the details of this protocol:
61 * 1. The host guarantees that while it is draining the
62 * ring buffer, it will set the interrupt_mask to
63 * indicate it does not need to be interrupted when
66 * 2. The host guarantees that it will completely drain
67 * the ring buffer before exiting the read loop. Further,
68 * once the ring buffer is empty, it will clear the
69 * interrupt_mask and re-check to see if new data has
73 static bool hv_need_to_signal(u32 old_write
, struct hv_ring_buffer_info
*rbi
)
76 if (rbi
->ring_buffer
->interrupt_mask
)
79 /* check interrupt_mask before read_index */
82 * This is the only case we need to signal when the
83 * ring transitions from being empty to non-empty.
85 if (old_write
== rbi
->ring_buffer
->read_index
)
92 * To optimize the flow management on the send-side,
93 * when the sender is blocked because of lack of
94 * sufficient space in the ring buffer, potential the
95 * consumer of the ring buffer can signal the producer.
96 * This is controlled by the following parameters:
98 * 1. pending_send_sz: This is the size in bytes that the
99 * producer is trying to send.
100 * 2. The feature bit feat_pending_send_sz set to indicate if
101 * the consumer of the ring will signal when the ring
102 * state transitions from being full to a state where
103 * there is room for the producer to send the pending packet.
106 static bool hv_need_to_signal_on_read(struct hv_ring_buffer_info
*rbi
)
111 u32 read_loc
= rbi
->ring_buffer
->read_index
;
115 * Issue a full memory barrier before making the signaling decision.
116 * Here is the reason for having this barrier:
117 * If the reading of the pend_sz (in this function)
118 * were to be reordered and read before we commit the new read
119 * index (in the calling function) we could
120 * have a problem. If the host were to set the pending_sz after we
121 * have sampled pending_sz and go to sleep before we commit the
122 * read index, we could miss sending the interrupt. Issue a full
123 * memory barrier to address this.
127 pending_sz
= rbi
->ring_buffer
->pending_send_sz
;
128 write_loc
= rbi
->ring_buffer
->write_index
;
129 /* If the other end is not blocked on write don't bother. */
133 r_size
= rbi
->ring_datasize
;
134 cur_write_sz
= write_loc
>= read_loc
? r_size
- (write_loc
- read_loc
) :
135 read_loc
- write_loc
;
137 if (cur_write_sz
>= pending_sz
)
143 /* Get the next write location for the specified ring buffer. */
145 hv_get_next_write_location(struct hv_ring_buffer_info
*ring_info
)
147 u32 next
= ring_info
->ring_buffer
->write_index
;
152 /* 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
;
160 /* Get the next read location for the specified ring buffer. */
162 hv_get_next_read_location(struct hv_ring_buffer_info
*ring_info
)
164 u32 next
= ring_info
->ring_buffer
->read_index
;
170 * Get the next read location + offset for the specified ring buffer.
171 * This allows the caller to skip.
174 hv_get_next_readlocation_withoffset(struct hv_ring_buffer_info
*ring_info
,
177 u32 next
= ring_info
->ring_buffer
->read_index
;
180 next
%= ring_info
->ring_datasize
;
185 /* Set the next read location for the specified ring buffer. */
187 hv_set_next_read_location(struct hv_ring_buffer_info
*ring_info
,
188 u32 next_read_location
)
190 ring_info
->ring_buffer
->read_index
= next_read_location
;
194 /* Get the start of the ring buffer. */
196 hv_get_ring_buffer(struct hv_ring_buffer_info
*ring_info
)
198 return (void *)ring_info
->ring_buffer
->buffer
;
202 /* Get the size of the ring buffer. */
204 hv_get_ring_buffersize(struct hv_ring_buffer_info
*ring_info
)
206 return ring_info
->ring_datasize
;
209 /* Get the read and write indices as u64 of the specified ring buffer. */
211 hv_get_ring_bufferindices(struct hv_ring_buffer_info
*ring_info
)
213 return (u64
)ring_info
->ring_buffer
->write_index
<< 32;
217 * Helper routine to copy to source from ring buffer.
218 * Assume there is enough room. Handles wrap-around in src case only!!
220 static u32
hv_copyfrom_ringbuffer(
221 struct hv_ring_buffer_info
*ring_info
,
224 u32 start_read_offset
)
226 void *ring_buffer
= hv_get_ring_buffer(ring_info
);
227 u32 ring_buffer_size
= hv_get_ring_buffersize(ring_info
);
231 /* wrap-around detected at the src */
232 if (destlen
> ring_buffer_size
- start_read_offset
) {
233 frag_len
= ring_buffer_size
- start_read_offset
;
235 memcpy(dest
, ring_buffer
+ start_read_offset
, frag_len
);
236 memcpy(dest
+ frag_len
, ring_buffer
, destlen
- frag_len
);
239 memcpy(dest
, ring_buffer
+ start_read_offset
, destlen
);
242 start_read_offset
+= destlen
;
243 start_read_offset
%= ring_buffer_size
;
245 return start_read_offset
;
250 * Helper routine to copy from source to ring buffer.
251 * Assume there is enough room. Handles wrap-around in dest case only!!
253 static u32
hv_copyto_ringbuffer(
254 struct hv_ring_buffer_info
*ring_info
,
255 u32 start_write_offset
,
259 void *ring_buffer
= hv_get_ring_buffer(ring_info
);
260 u32 ring_buffer_size
= hv_get_ring_buffersize(ring_info
);
263 /* wrap-around detected! */
264 if (srclen
> ring_buffer_size
- start_write_offset
) {
265 frag_len
= ring_buffer_size
- start_write_offset
;
266 memcpy(ring_buffer
+ start_write_offset
, src
, frag_len
);
267 memcpy(ring_buffer
, src
+ frag_len
, srclen
- frag_len
);
269 memcpy(ring_buffer
+ start_write_offset
, src
, srclen
);
271 start_write_offset
+= srclen
;
272 start_write_offset
%= ring_buffer_size
;
274 return start_write_offset
;
277 /* Get various debug metrics for the specified ring buffer. */
278 void hv_ringbuffer_get_debuginfo(struct hv_ring_buffer_info
*ring_info
,
279 struct hv_ring_buffer_debug_info
*debug_info
)
281 u32 bytes_avail_towrite
;
282 u32 bytes_avail_toread
;
284 if (ring_info
->ring_buffer
) {
285 hv_get_ringbuffer_availbytes(ring_info
,
287 &bytes_avail_towrite
);
289 debug_info
->bytes_avail_toread
= bytes_avail_toread
;
290 debug_info
->bytes_avail_towrite
= bytes_avail_towrite
;
291 debug_info
->current_read_index
=
292 ring_info
->ring_buffer
->read_index
;
293 debug_info
->current_write_index
=
294 ring_info
->ring_buffer
->write_index
;
295 debug_info
->current_interrupt_mask
=
296 ring_info
->ring_buffer
->interrupt_mask
;
300 /* Initialize the ring buffer. */
301 int hv_ringbuffer_init(struct hv_ring_buffer_info
*ring_info
,
302 void *buffer
, u32 buflen
)
304 if (sizeof(struct hv_ring_buffer
) != PAGE_SIZE
)
307 memset(ring_info
, 0, sizeof(struct hv_ring_buffer_info
));
309 ring_info
->ring_buffer
= (struct hv_ring_buffer
*)buffer
;
310 ring_info
->ring_buffer
->read_index
=
311 ring_info
->ring_buffer
->write_index
= 0;
313 /* Set the feature bit for enabling flow control. */
314 ring_info
->ring_buffer
->feature_bits
.value
= 1;
316 ring_info
->ring_size
= buflen
;
317 ring_info
->ring_datasize
= buflen
- sizeof(struct hv_ring_buffer
);
319 spin_lock_init(&ring_info
->ring_lock
);
324 /* Cleanup the ring buffer. */
325 void hv_ringbuffer_cleanup(struct hv_ring_buffer_info
*ring_info
)
329 /* Write to the ring buffer. */
330 int hv_ringbuffer_write(struct hv_ring_buffer_info
*outring_info
,
331 struct kvec
*kv_list
, u32 kv_count
, bool *signal
, bool lock
)
334 u32 bytes_avail_towrite
;
335 u32 bytes_avail_toread
;
336 u32 totalbytes_towrite
= 0;
338 u32 next_write_location
;
340 u64 prev_indices
= 0;
341 unsigned long flags
= 0;
343 for (i
= 0; i
< kv_count
; i
++)
344 totalbytes_towrite
+= kv_list
[i
].iov_len
;
346 totalbytes_towrite
+= sizeof(u64
);
349 spin_lock_irqsave(&outring_info
->ring_lock
, flags
);
351 hv_get_ringbuffer_availbytes(outring_info
,
353 &bytes_avail_towrite
);
356 * If there is only room for the packet, assume it is full.
357 * Otherwise, the next time around, we think the ring buffer
358 * is empty since the read index == write index.
360 if (bytes_avail_towrite
<= totalbytes_towrite
) {
362 spin_unlock_irqrestore(&outring_info
->ring_lock
, flags
);
366 /* Write to the ring buffer */
367 next_write_location
= hv_get_next_write_location(outring_info
);
369 old_write
= next_write_location
;
371 for (i
= 0; i
< kv_count
; i
++) {
372 next_write_location
= hv_copyto_ringbuffer(outring_info
,
378 /* Set previous packet start */
379 prev_indices
= hv_get_ring_bufferindices(outring_info
);
381 next_write_location
= hv_copyto_ringbuffer(outring_info
,
386 /* Issue a full memory barrier before updating the write index */
389 /* Now, update the write location */
390 hv_set_next_write_location(outring_info
, next_write_location
);
394 spin_unlock_irqrestore(&outring_info
->ring_lock
, flags
);
396 *signal
= hv_need_to_signal(old_write
, outring_info
);
400 int hv_ringbuffer_read(struct hv_ring_buffer_info
*inring_info
,
401 void *buffer
, u32 buflen
, u32
*buffer_actual_len
,
402 u64
*requestid
, bool *signal
, bool raw
)
404 u32 bytes_avail_towrite
;
405 u32 bytes_avail_toread
;
406 u32 next_read_location
= 0;
407 u64 prev_indices
= 0;
408 struct vmpacket_descriptor desc
;
417 *buffer_actual_len
= 0;
420 hv_get_ringbuffer_availbytes(inring_info
,
422 &bytes_avail_towrite
);
424 /* Make sure there is something to read */
425 if (bytes_avail_toread
< sizeof(desc
)) {
427 * No error is set when there is even no header, drivers are
428 * supposed to analyze buffer_actual_len.
433 next_read_location
= hv_get_next_read_location(inring_info
);
434 next_read_location
= hv_copyfrom_ringbuffer(inring_info
, &desc
,
438 offset
= raw
? 0 : (desc
.offset8
<< 3);
439 packetlen
= (desc
.len8
<< 3) - offset
;
440 *buffer_actual_len
= packetlen
;
441 *requestid
= desc
.trans_id
;
443 if (bytes_avail_toread
< packetlen
+ offset
)
446 if (packetlen
> buflen
)
450 hv_get_next_readlocation_withoffset(inring_info
, offset
);
452 next_read_location
= hv_copyfrom_ringbuffer(inring_info
,
457 next_read_location
= hv_copyfrom_ringbuffer(inring_info
,
463 * Make sure all reads are done before we update the read index since
464 * the writer may start writing to the read area once the read index
469 /* Update the read index */
470 hv_set_next_read_location(inring_info
, next_read_location
);
472 *signal
= hv_need_to_signal_on_read(inring_info
);